Search for associations containing young stars (SACY) VIII. An updated census of spectroscopic binary systems showing hints of non-universal multiplicity among these associations
S. Zúñiga-Fernández, A. Bayo, P. Elliott, C. Zamora, G. Corvalán, X. Haubois, J. M. Corral-Santana, J. Olofsson, N. Huélamo, M. F. Sterzik, C. A. O. Torres, G. R. Quast, C. H. F. Melo
AAstronomy & Astrophysics manuscript no. sb˙update © ESO 2020October 22, 2020
Search for associations containing young stars (SACY)
VIII. An updated census of spectroscopic binary systems showing hints ofnon-universal multiplicity among these associations
S. Z´u˜niga-Fern´andez , , (cid:63) , A. Bayo , , P. Elliott , C. Zamora , , G. Corval´an , , X. Haubois , J. M. Corral-Santana , J.Olofsson , , N. Hu´elamo , M. F. Sterzik , C. A. O. Torres , G. R. Quast , and C. H. F. Melo N´ucleo Milenio de Formaci´on Planetaria (NPF), Valpara´ıso, Chile European Southern Observatory, Alonso de C´ordova 3107, Vitacura, Casilla 19001, Santiago de Chile, Chile Universidad de Valpara´ıso, Instituto de F´ısica y Astronom´ıa (IFA), Avenida Gran Breta˜na 1111, Casilla 5030, Valpara´ıso, Chile Department of Physics and Astronomy, York University, Toronto, ON M3J 1P3, Canada Centro de Astrobiolog´ıa (CSIC-INTA), ESAC Campus, Camino del Castillo s / n, E-28692 Villanueva de la Ca˜nada, Madrid, Spain Laborat´orio Nacional de Astrof´ısica / MCTIC, Rua Estados Unidos 154, 37504-364 Itajub´a (MG), Brazil European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748, Garching bei Munchen, GermanyReceived ; accepted
ABSTRACT
Context.
Nearby young associations o ff er one of the best opportunities to study in detail the properties of young stellar and substellarobjects thanks to their proximity ( <
200 pc) and age ( ∼ −
150 Myr). Previous works have identified spectroscopic ( < − , − ,
000 au) binaries in the young associations. In most ofthe previous analyses, single-lined spectroscopic binaries (SB1) were identified based on radial velocities variations. However, thisapparent variation can also be caused by mechanisms unrelated to multiplicity.
Aims.
We seek to update the spectroscopy binary fraction of the SACY (Search for Associations Containing Young stars) sampletaking in consideration all possible biases in our identification of binary candidates, such as activity and rotation.
Methods.
Using high-resolution spectroscopic observations we have produced ∼ Results.
We identified 68 SB candidates from our sample of 410 objects. Our results hint that the youngest associations have ahigher SB fraction. Specifically, we found sensitivity-corrected SB fractions of 22 + − % for ε Cha , 31 + − % for TW Hya and 32 + − %for β Pictoris, in contrast with the five oldest associations we have sampled ( ∼ −
125 Myr) which are ∼
10% or lower. This resultseems independent of the methodology used to asses membership to the associations.
Conclusions.
The new CCF analysis, radial velocity estimates and SB candidates are particularly relevant for membership revisionof targets in young stellar associations. These targets would be ideal candidates for follow-up campaigns using high-resolution tech-niques in order to confirm binarity, resolve the orbits, and ideally calculate dynamical masses. Additionally, if the results on SBfraction in the youngest associations are confirmed, it could hint of non-universal multiplicity among SACY associations.
Key words. (Stars:) binaries: spectroscopic – Stars: pre-main sequence – Stars: formation – (Stars:) binaries (including multiple):close – Techniques: radial velocities – Techniques: spectroscopic
1. Introduction
Since the first nearby young moving group of stars was iden-tified around 30 years ago (TW Hya association, de la Rezaet al. 1989; Kastner et al. 1997) extensive research has been con-ducted on these stellar associations: from identifying new onesand their members, to characterizing their chemical composi-tion, dynamics, ages and multiplicity fractions (see Zuckermanet al. 2004; Torres et al. 2008; Shkolnik et al. 2012; Malo et al.2014; Elliott & Bayo 2016; Gagn´e et al. 2018a, among oth-ers). These nearby populations, given their age ( ∼ <
200 pc), are great laboratories for studying theproperties of young stellar and substellar objects.Recent studies have used youth signatures (such as the pres-ence of H α in emission or the detection of the Li λ (cid:63) [email protected] and 6D kinematics (i.e. Galactic position and Galactic velocityin the 6 parameter space, XYZ and UVW) to estimate member-ship (Schneider et al. 2019; Lee & Song 2019). In this context,multiplicity studies (particularly the search for tight binaries)play an important role since age diagnostics, velocity determina-tions, and astrometry are often a ff ected by the use of single-starmodels on blended multiple systems.More generally speaking, stellar multiplicity is important ina broad range of fields (e.g. supernova rates), but we will fo-cus here on its impact in the star formation processes. Workson multiplicity as a function of environment, and detailed stud-ies of composition and orbital parameters, provide valuableempirical data to improve our understanding of stellar evolu-tion and unresolved stellar populations. These empirical esti-mates are of particular interest at younger ages and close sep-arations where the theoretical models remain still only loosely a r X i v : . [ a s t r o - ph . S R ] O c t . Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) constrained (Duchˆene et al. 2007; Connelley et al. 2008; Tobinet al. 2016), and the literature is still far from the more ex-haustive work done for main sequence (MS) stars with volumelimited samples (Tokovinin 2014a; Tokovinin & Briceno 2019;Tokovinin 2019; Sperauskas et al. 2019; Merle et al. 2020).It is widely accepted that almost half of solar-type starsspend their time in the MS as multiple systems (Tokovinin2014a; Raghavan et al. 2010). There is also increasing evidencethat multiplicity is even higher at very young ages (Tobin et al.2016), possibly indicating the primordial nature of multiplicityin the processes of star formation. Observational studies suggestan overall decrease of the binary fraction from pre-MS ages tofield ages (Ghez et al. 1997; Kouwenhoven et al. 2007; Raghavanet al. 2010). This decrease could be a consequence of disrup-tion process in long period systems due to interactions withother systems (Raghavan et al. 2010) or due to the dynamicalevolution of wide companions in triple or higher order systems(Sterzik & Tokovinin 2002; Reipurth & Mikkola 2012; Elliott &Bayo 2016). In contrast with wide binaries, tight binaries are ex-pected to “last” longer given their larger binding energy. A num-ber of observational results on tight binaries have indicated thatthe overall SB fraction remains unchanged after 1 Myr (Nguyenet al. 2012; Tokovinin 2014b; Elliott et al. 2014). However, re-cently, Jaehnig et al. (2017) suggested that some SBs (periods ≈ − days) in pre-MS clusters ( ≈ −
10 Myr) can be dy-namical disrupted prior to reaching the MS. The evolution andthe formation channel of multiple stellar systems can not be eas-ily determined by field stars, where billions of years of dynam-ical evolution have already occurred. Therefore it is necessaryto devote specific studies of the stellar multiplicity from star-forming regions (SFRs) to the young associations (1 −
100 Myr).The multiplicity studies for the youngest stars ( ≤
100 Myr)are still dominated by low number statistics. This is particularlycritical in the case of SBs (sub-au separation scales) where high-resolution techniques are mandatory (Melo 2003; Nguyen et al.2012; Viana Almeida et al. 2012), but some of these techniquescan be contaminated by phenomena such as activity and rota-tion, inherent to the young ages involved (see Section 5). Inprinciple, the preferred mechanism to form some of these closebinaries ( (cid:46)
100 au) is disk fragmentation, where the disk frag-ments due to gravitational instabilities (Bonnell & Bate 1994;Zhu et al. 2012). However, the formation mechanisms could bea ff ected by environment conditions. In particular, Bate (2019)found an apparent trend for multiple systems to be preferentiallytighter when formed at lower metallicity environments. On theother hand, the tightest systems ( (cid:46)
10 au) cannot form directlyneither via turbulent nor disk fragmentation, and the emergingconsensus is that some processing must dynamically evolve theinitial separations to closer ones (Bate et al. 2002). In particular,Tokovinin et al. (2006) found that ∼
63% of MS SBs were mem-bers of high-order multiple systems (see Elliott & Bayo 2016for a similar result focused on the β Pictoris moving group).Interestingly, ∼
98% of SBs with orbital periods shorter than3 days have additional companions. This result seems to pro-vide observational support to the dynamical evolution hypothe-sis commented before. Further SB studies in younger population( ≤
100 Myr) are, in any case, still needed to provide improvedstatistics on more pristine populations.This work is the continuation of a series of studies of multi-plicity in young associations over a wide range of orbital param-eters ( a ∼ . − au: Elliott et al. 2014, 2015, 2016a; Elliott& Bayo 2016). In particular, this work focuses on SB identifi-cation within SACY via cross-correlation function (CCF), notonly using the radial velocity (RV) variations with time as a sign of multiplicity, but also incorporating high-order featuresas a complementary tool to establish the origin of the variation.After modelling and applying observational bias corrections, wepresent the results on SB fraction in each association within theSACY sample and the list of SB candidates, including notes onindividual objects.
2. Sample
The sample presented in this work is drawn from our databaseof young association members, as in Elliott et al. (2016a),mainly collected from Torres et al. (2006); Torres et al. (2008);Zuckerman et al. (2011); Malo et al. (2014); Kraus et al. (2014);Elliott et al. (2014) and Murphy et al. (2015). The membershipof each object to the di ff erent associations was assessed using theconvergence method described in Torres et al. (2006) and Torreset al. (2008) with the updated distances from the second Gaiadata release (Gaia DR2, Gaia Collaboration et al. 2018). Thefull membership study and further analysis will be presented inTorres et al. (in prep.).In addition, the targets selected for this work have to fulfil atleast one of the following selection criteria: – The objects have at least one high-resolution spectrum in ourdatabase, from which a CCF can be calculated. – The target has at least one RV measurement (with uncer-tainty ≤ − ) and one v sin i value in the literature (withuncertainty ≤ − ).We will be referred as “the sample” to which was ob-tained with the SACY convergence method unless otherwise in-dicated. Our sample covers an approximate mass range of 0.1 –1.5 M (cid:12) , with the majority of objects having an estimated massaround 1 M (cid:12) . Masses were estimated from the 2MASS near-infrared magnitudes and parallactic distances using the evolu-tionary tracks from Bara ff e et al. (2015). Our final sample sizeis 410 objects, 303 of which have two or more epochs of high-resolution spectra. Further details on the literature’s measure-ments used in our sample are summarised in Sec. 3.2, and allrelevant parameters for this work are listed in Table G.4.
3. Observations and additional data
We obtained spectra taken with the Ultraviolet and VisualEchelle Spectrograph (UVES; λ / Δλ ∼ ,
000 with 1 (cid:48)(cid:48) slit,Dekker et al. 2000) at Paranal, Chile. These observations camefrom three of our observing campaigns, taken between 2015 and2016. We also added data retrieved from the ESO phase 3 pub-lic archive . Our data were taken with a 1 (cid:48)(cid:48) slit width in thewavelength range 3250 − ff erent observing epochs of a given source ranges from 1 dayto ∼ pipeline of UVES,using the uves obs redchain recipe (bias corrected, dark cur-rent corrected, flat-fielded, wavelength-calibrated and extracted).This provides three spectra from the two arms of the instrument(BLUE and REDL / REDU, with wavelength coverage 3250 − − − / N) for the BLUE spectrum http://archive.eso.org/wdb/wdb/adp/phase3_main/form
2. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) is >
10. Otherwise, we combined the REDU and REDL spec-tra only. In total, we present 998 individual CCFs from UVESobservations.
In order to maximise the time baseline and available spec-tral information for each target, we used the publicly avail-able Phase 3 data taken with the Fibre-fed Extended Range´Echelle Spectrograph (FEROS / / λ / Δλ ≈ , / ESO 2.2-m telescope located atESO’s La Silla Observatory, Chile. The wavelength range of thereduced spectra is 3527 − λ / Δλ ≈ , − Table 1 lists the references used in this work for both the RVand v sin i values. As mentioned previously, we only includevalues that have uncertainties ≤ − and ≤ − forRV and v sin i , respectively. The table is split into two sections:the top one shows values that do not have associated ModifiedJulian Dates (MJD) values for each RV. The bottom section cor-responds to surveys that do have individual MJD values for eachobservation. The second Gaia data release (hereafter: Gaia DR2) was issuedon 25 April 2018, providing accurate proper motions and par-allaxes (among other astrophysical parameters) for more than abillion sources. In particular, this Gaia data release also includesfor the first time RV values (Katz et al. 2018) for objects with amean G magnitude between ∼ ∼
13 and e ff ective tempera-tures ( T e ff ) between 3550 and 6900 K.The overall precision of the RV at the bright-end is in theorder of 200 −
300 m s − while at the faint-end it deteriorates to ∼ . − for a T e ff of 4750 K and ∼ . − for a T e ff of6500 K.Stars identified as double-lined spectroscopic binaries arenot reported in Gaia DR2, while variable single-lined, variablestar, and non detected double-lined spectroscopic binaries havebeen treated as single stars in the same release (Sartoretti et al.2018). Table 1.
Previous catalogues of RV and v sin i values used in thiswork. The bottom section shows those values with associatedMJDs, while the top section show values for which MJDs havebeen estimated from the respective MJD-range. Ref. Values MJD-range Ref. codeMJD estimated from observation rangeSchlieder et al. (2012) RV, v sin i a v sin i b v sin i c v sin i v sin i Notes. ( a ) Extended from Shkolnik et al. (2010), ( b ) Stars added to theinitial sample of Zuckerman et al. (2004), ( c ) v sin i values not usedfrom Kraus et al. (2014) as these values are the standard deviation ofthe broadening function, not calibrated v sin i values. We retrieved Gaia DR2 data for all the objects in the SACYsample using the astroquery Vizier package . We updatedour local database to use identifiers resovable by the Sesame ser-vice and the Gaia DR2 queries were based on those identifiers.Objects not resolved by identifiers were instead searched by co-ordinates. In both cases we ran an initial query with a 10 (cid:48)(cid:48) radiusand used the proper motions of the closest Gaia source, withinthe radius, to derive its J2000 coordinates (that are those orig-inally included in our local database). Those J2000 coordinateswere then matched to the coordinates in our local database with a1 (cid:48)(cid:48) radius. Objects outside of this 1 (cid:48)(cid:48) radius were individually in-spected (see Fig. E.1 in the Appendix) by cross validating usingSimbad, Vizier and the TESS input catalogue (TIC-8, Stassunet al. 2019). We recovered Gaia DR2 counterparts for 805 out of837 targets in our local database, corresponding to a complete-ness of 96 .
2% (see Fig. 1). From these 805 objects, 374 have RVmeasurements from Gaia, which were used in this work as anadditional epoch of data.Our database comprises 2379 RV measurements and 1515 v sin i values, 1151 of which come from our CCF calculationof high-resolution spectra. All these values together with otheradditional properties can be found in Table G.1 and G.2. Σ In order to asses any possible bias throughout this work with theuse of the convergence method to build the census of the di ff er- https://astroquery.readthedocs.io/en/latest/vizier/vizier.html
3. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY)
V Magnitude
Fig. 1.
V-magnitude distribution of all members of the SACYsample along with those with counterpart in the Gaia DR2. Wereach a completeness of 96 .
2% where 44 .
7% of the objects countwith a Gaia RV estimate.ent associations, we have followed an independent path, utilisingthe BANYAN Σ tool for young association membership.Accurate RV, distances and proper motion values are key in-gredients in the accuracy of our convergence method (Torreset al. 2006; Torres et al. 2008). Similarly, the recovery rateof BANYAN Σ is 68% when proper motion and RV are usedand 90% when parallaxes are included (Gagn´e et al. 2018a).Therefore, as we did for the convergence method, we fed the RVmeasurements collected in this work plus the Gaia DR2 propermotion and parallaxes to the BANYAN Σ tool for membershipassessment.It is out of the scope of this work to develop or establish ametric to compare in details the outcome of the two methodolo-gies. However, the two resulting censuses, allow us to test therobustness of our results against moderate changes in member-ship (see Sec. 8 for further details). The membership results forthe SACY convergence method and BANYAN Σ are available inTable G.4 and summarised in Fig. 2. The mass distributions ofthe samples analysed throughout this work (using either our con-vergence method or BANYAN Σ tool) are shown in the bottompanel of Fig. 2. As it can be seen, the only associations with no-ticeable di ff erences regarding total number of members are ABDand THA. In order to estimate the rotational periods of the objects in thesample, we queried two of the main missions delivering preciselight curves: K2 and TESS (Howell et al. 2014; Ricker et al.2015). We proceeded in the following manner:1. We queried the archives of both missions via the MASTAPI (via the astroquery package within astropy ) with https://github.com/jgagneastro/banyan_sigma Mass ( M ) F r e q u e n c y SACYBANYAN
ABD ARG BPC COL ECH OCT THA TWA
Young associations N u m b e r o f m e m b e r s Method
SACYBANYAN
Fig. 2.
Top:
Number of targets belonging to each young as-sociations identified by our convergence method (SACY) andBANYAN Σ . Bottom:
Mass function of the census built with theconvergence method and BANYAN Σ for membership assess-ment.the J2000 coordinates of each object and a search radius of0.002 deg ( ∼ (cid:48)(cid:48) ). We obtained light curves for 272 out of 410objects ( ∼
65% of the sample). In particular, 266 were takenwith TESS (across di ff erent sectors) and six with K2.2. In all cases we chose the Pre-search Data ConditionedSimple Aperture Photometry (PCDSAP) fluxes andcharacterised the variability of the sources via theirLomb-Scargle (LS) periodograms (calculated with astropy.timeseries.lombscargle , VanderPlas &Ivezic 2015).3. Even though the false alarm probabilities (FAPs) of the peaksidentified in the LS periodogram were extremely low (typi-cally well below 10 − ), we performed a simple quality checkfor the identified periods in the following way: we foldedeach light curve to the period with the highest intensity inthe LS periodogram and model the modulation by calculat-ing the median, binning the phased curve in 100 bins. Suchtrend was subtracted from the phased light curve and the me-dian absolute deviation (MAD) of those residuals was com-pared to the MAD of the original phased light curve.4. In the case of TESS data, additional checks need to be doneto account for the large pixel size of its detector. In or-der to estimate the contamination that could a ff ect each ofthe light curves, we modified the existing python package tpfplotter (Aller et al. 2020) that, in short, provides thenumber of Gaia sources within a ∆ G mag (Gaia G mag, this ∆ is defined by the user) of the science target that fall in thepipeline aperture of TESS. We modified the code in order totake into account both, the proper motion of our targets andthe cross-match with Gaia DR2 explained in Sec. 3.3. Wechose a ∆ Gmag of 5 magnitudes and in Table G.4 we includenotes on the minimum ∆ Gmag found within the aperture. We
4. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) note that a number (27 to be precise) of our Gaia cross-matchidentifications are not recovered in Simbad. Even though westand by those identifications, we have identified them in thecolumn
LC notes of Table G.4.5. We classified a period as “good quality” if the MAD of theresiduals is at least three times smaller than the MAD of theoriginal phased light curve and if there are no Gaia sourcesthat fall in the aperture with ∆ G mag <
5. Periods which ful-fil the criteria based on the MAD of the residuals but havecontaminants in the aperture with 2 . ≤ ∆ G mag ≤ v sin i from ourwork are presented in Fig. 3 (see the details regarding v sin i estimation in appendix. B). This relation was used throughoutour analysis as a complementary source to evaluate the nature ofSB candidates. Median v sin i (km s ) P e r i o d f r o m L C ( d a y s ) LC quality flag: GoodLC quality flag: CautionLC quality flag: Bad
Fig. 3.
Rotational periods estimated from the light curves versusmedian v sin i from our work. The quality flag of the perioddefined in Sec. 3.5, is color-coded as grey, orange and blue forbad, caution and good, respectively.
4. Properties and calculation of CCF profiles
There are two main ways of calculating CCFs from high-resolution spectra, using either observations of RV standard starsor using a numerical mask, acting as a standard star. In this anal-ysis we used a CORAVEL-type numerical mask which was con-voluted with the observed spectrum for each observation (for fur-ther details see Queloz 1995). For the sake of homogeneity and given the relatively narrow range of spectral types in our sample(see Table G.4), we use a single K0 mask in our analysis.Only in the cases where the K0 mask completely failed in theCCF calculation (assessed by the goodness of fit of the Gaussianprofile to the CCF), we used other available masks (F0 or M4,depending on the spectral type of the star). However, for consis-tency, the CCF profiles and respective properties of such objectsare not included in the statistical analysis of our measurements.The CCFs analysis and the SB update presented in this workfollows up what was presented by Elliott et al. (2014). However,here we do not only enlarge our database of observations, butwe have also chosen to use a much more detailed approach incalculating the CCFs for each observation; by introducing high-order features of the CCFs, we can distinguish between apparentRV variation caused by poor fitting of the CCF and variationproduced by bound companions and / or stellar activity. The uncertainty in RV calculation using a numerical mask( σ meas . ) can be derived with the following equation (Baranneet al. 1996): σ meas . = C ( T e ff ) D × S / N + . ω − (1)where C ( T e ff ) is a constant that depends on both the spectral typeof the star and the mask used, which is typically 0.04; ω is the(noiseless) full width at half maximum (in km s − ) of the CCF; D is the (noiseless) relative depth, and S / N is the mean signal-to-noise ratio.This uncertainty is relevant to one measurement of RV froma single observation and a single instrument. Given the highS / N of our data, typically ∼ − ff erent epochs and gauging thelevel of intrinsic variation of the star. As these stars are oftenvariable, the CCF profiles are not always completely symmetric(Lagrange et al. 2013) and, therefore the uncertainty calculatedusing Equation 1 is underestimated. Thus, following the analysispresented in Elliott et al. (2014), we use an empirical approachto estimate RV uncertainties (see Sec. 6.1 for further details). In order to better describe the CCF profile we calculate a set ofhigh-order cross-correlation features: – Bisector : The bisector is calculated from the midpoint ofthe line for each element of intensity that defines the CCFprofile, shown by the grey dots in upper right panel in Fig. 4. – Bisector inverse slope : Here we adopt the bisector inverseslope (BIS) as defined by Queloz et al. (2001):
BIS = ¯ v t − ¯ v b (2)where ¯ v t is the mean bisector velocity in the region between10% and 40% of the line depth and ¯ v b is the mean bisectorvelocity between 55% and 90% of the line depth. These tworegions are highlighted in the bottom right panel of Fig. 4. – Bisector slope (b b ) : This is defined as the inverse slope froma linear fit (shown by the red line in the bottom right panel
5. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) − − −
25 0 25 50 75 100Velocity (km s − )0 . . . . . . CC F RV: 6.7Depth: 0.104Width: 11.2AD stat: 0.765 (0.025)MJD: 56774.40 − − − − )0 . . . . . . CC F − − − − ) − . − . − . − . . . . . . . R e l a ti v e d e p t h Best fit: 12 km s − Stretch: 1.5 vsin(i) value . . . . . . . . P r o fi l e r e s i du a l . . . . . . − )0 . . . . . . CC F ¯ v t − ¯ v b = -0.242 b b = -2.653 c b = 0.089 Fig. 4.
An example of the graphical output from our CCF calculation code for one target.
Top left : The CCF profile. The quantitiesshown in the lower left are the peak of the fitted Gaussian profile (RV), the depth of the CCF, the width ( σ ) of the Gaussianprofile, the Anderson-Darling statistic for normality between − σ and + σ with its respective significance level and the MJD of theobservation. Top right : The 2 σ region of the CCF profile and the bisector (grey dots). Bottom left : The normalised CCF fitted withthe best-fit rotational profile (from profiles in the v sin i range 1–200 km s − ). The residuals of fits are shown in the inset. Bottomright : The bisector slope along with three metrics of its shape ( b b , c b and BIS ). See text in Section 4 and 5 for further details.of Fig. 4) for the region between 25%-80% of the CCF’sdepth (Dall et al. 2006). – Curvature (c b ) : The curvature of the CCF’s profile is definedas: c b = ( v − v ) − ( v − v ) (3)where v , v , and v are the mean bisector velocity on the20-30%, 40-55%, and 75-100% of the CCF’s depth. Thisdefinition is from Dall et al. (2006) which is a slightlymodified version of the curvature presented in Povich et al. (2001). – Anderson-Darling statistic (AD) : We use the AD statisticaround the peak of the CCF profile as a test for normality,i.e. how Gaussian-like the profile is. We perform this testaround the 1 σ region around the peak of the CCF profile.The AD statistic and its significance are shown in the upperleft panel of Figure 4, i.e. the null hypothesis, that thefunction is not Gaussian, cannot be rejected at a significantlevel.
6. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY)
Fig. 5.
Left panel : RV values calculated in this work versus values from the literature. Crosses represent previously identifiedspectroscopic multiple systems. The 1:1 relation is shown by the dashed line.
Right panel : Same as upper panel, but for v sin i values. – Profile residual : The CCF profile is fitted by a set of ro-tational profiles (Gray 1976) to determine its v sin i value.In order to quantify the validity of this fit we calculated theoverall residual for each v sin i profile (from 1 - 200 km s − ).The minimum of this set of residuals is used to determinethe best-fit profile for each observation, but also the abso-lute value is retained. That way we can compare the absoluteresiduals as a function of other properties in our sample.
5. Estimates of radial and rotational velocities
To calculate all the properties defined in the previous sectionfrom the available high-resolution optical spectra, we wrote aseries of functions . Those functions compute the CCFs, and re-turn these properties as a “digest” of the information containedin the CCFs.Figure 4 shows the summary graphical output from the mas-ter function described before. The CCF is shown in the top leftpanel of Fig. 4, i.e. the resulting profile of the star’s spectrumwith the numerical mask (in black) and the Gaussian profile fit-ted to the data (in blue). The grey dots in the right panel of Fig.4 represent the bisector of the profile whereas the red and blueparts show the two separate sides of the 2 σ region of the star’sCCF profile. Another relevant output from our functions is thestar’s normalised CCF profile with the best-fit rotational profile(bottom left in Fig. 4 from a series of profiles with v sin i from1 - 200 km s − ). The legend shows the best fitting profile valueand the stretch factor which is a measure of how much the best-fit v sin i profile was stretched to achieve the fit. The inset in theupper right shows an area around the minimum of the residualsfrom di ff erent v sin i profile fitting, highlighting in this case that7 km s − is clearly the best fit. Note that these v sin i values are“raw”, see Appendix B for details on calibration. The three met-rics of the bisector are also given by our functions (see bottomright panel in Fig. 4). Namely the BIS (¯ v t − ¯ v b ), the slope ( b b )and the curvature ( c b ) which help to quantitatively characterisethe properties of the bisector. Code is available at https://github.com/szunigaf
We visually inspected each of the CCF outputs and removedany observations where the CCF calculation had clearly failed(or a di ff erent mask had to be used), mostly due to low S / N. Thisleft 1375 CCFs for further analysis.Several broadening mechanisms can contribute to the widthof the CCF, these can either be inherent to the star (surface grav-ity, e ff ective temperature, rotation, turbulence) or arise from theinstrument used to obtain the observations. Therefore to accu-rately measure rotational velocities we have to account for non-rotational broadening mechanisms, both physical and instrumen-tal. The details for our calibration approach can be found inAppendix B.5.With our calibrated v sin i values and barycentric RVs, wewere able to look at the overall properties of our targets by com-bining individual observations. We were also able to identifyany clear double-lined spectroscopic binaries from their double-peaked CCF profiles, see Appendix A. For each object, we compared the median RVs and v sin i fromour database with previously published values (see Table 1 forreferences) to ensure there was no significant o ff set. Figure 5shows the results of this comparison. The error bars for eachquantity represent the standard deviation from multiple observa-tions.Black crosses represent objects previously identified as mul-tiple systems, i.e. those not likely to follow the 1:1 relation. Wealso note that for v sin i (cid:38)
50 km s − , the broader CCF profiletranslates into a larger uncertainty on the estimate of this quan-tity (see Appendix B). With all of this into account, the 1:1 rela-tion describes adequately the comparison of both sets of valuesfor objects considered as a single stars, demonstrating that ournew functions calculating CCF properties are working correctly.
7. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) v sin i, this work (km s ) R V , t h i s w o r k ( k m s ) v sin i, this work + literature (km s ) R V , t h i s w o r k + li t e r a t u r e + G D R ( k m s ) power law envelopev sin i binned 3 RV Fig. 6.
Left panel : The standard deviation in RV as a function of v sin i for measurements calculated in this work. The 3 σ valuefrom binning in 6 km s − bins are represented by the red solid lines. The power-law envelope is represented by dash-dotted blueline. Right panel : Same as left panel but including values from literature and Gaia DR2 for the standard deviation estimates.
6. Using multiple measurements to identifysingle-lined spectroscopic binaries
Most previous studies identifying SB1 solely rely on the analy-sis of multi-epoch RV values. However, in this work we use thehigh-order CCF features, if possible, when investigating any po-tential RV variation to better conclude on the true nature of theobject. We made an initial list of systems to be further investi-gated by looking at both RV and v sin i variation as a function of v sin i . Typically, the variation in RV ( σ rv ) is used to flag potential SB1.However, this apparent variation can also be caused by mecha-nisms unrelated to multiplicity. Elliott et al. (2014) used a singlevalue (global σ rv = − ) to flag potential SB1, irrespec-tive of their v sin i values. However, in this work we show that σ rv is a function of v sin i , i.e. the apparent radial velocity vari-ation is intrinsically related to the target’s v sin i . This was alsodemonstrated in Bailey et al. (2012) using near-infrared radialvelocities. The relationship can be explained by the peak of theCCF being less well-defined the broader the profile is. We canexploit this relationship to revisit the spectroscopic multiplicityof stars in our sample.Fig. 6 shows σ rv versus v sin i for stars in our sample thatare not double- or triple-lined spectroscopic binaries, and thathave observations for at least two di ff erent epochs. The left panelshows the estimates from this work while the right panel presentsour values together with those compiled from literature and GaiaDR2. For the sake of homogeneity, to be considered, the litera-ture data also has to fulfil the criteria of having an uncertainty onRV and v sin i lower than 3 and 5 km s − , respectively (Sec. 2).Considering only our measurements, we note that the disper-sion in RV is relatively low for slow rotators. For example, 3 σ variation of 0 . . − for v sin i of ≈ − ,respectively (shown by the solid red line in Fig. 6). Only at v sin i ≈
40 km s − more than 3 km s − RV variations are ob-served. When measurements from the literature are considered,on average, RV variations increase which is expected from com-bining observations from di ff erent instruments, heterogeneity in the procedure to perform the estimates, and a longer time-spanbetween observations.As mentioned before, a relationship between v sin i and σ rv is expected. In order to obtain a general and empirical descrip-tion this relation, we calculated the 3 σ interval for σ rv using anarray of binned v sin i values. We ran a Monte Carlo simulationusing the 3 σ statistics for di ff erent bin size and phase (the start-ing point of the binning). The bin size range was between 3 and 7km s − . This range was estimated from the three most common-used bin size estimation method: Freedman & Diaconis (1981),Scott (1979) and Sturges (1926). The selected initial phase rangecovers from 0 to 4 km s − . This exercise allowed us to address thedispersion in the results that can be explained solely in therms ofthe choice of phase and bin size. Each realisation is representedby a light red line in Fig. 6. It is out of the scope of this work tocharacterise in details the underlining physical structure betweenthe σ rv values as a function of v sin i . The only purpose of thesimple analysis presented here is to have a first order estimate ofthe e ff ect of the rotation velocity in the RV determination and,consequently, in its variation. The final adopted thresholds to beused as “caution” flags when assessing multiplicity are those re-sulting from a 6 km s − step between 0 and 42 km s − (solid redline, Fig. 6). This bin size was selected by taking in considera-tion the better compromise between sampling and the minimumnumber of points in each bin. Beyond 43 km s − on v sin i , thenumber of points in each bin is (cid:46)
10, and therefore the statisticsbecome less reliable. However, we can assume that a very roughpositive correlation is maintained or at the very least that it doesnot invert, i.e. the higher the v sin i , the larger the RV variationis. As an alternative method to identify SB candidates, we fit apower-law of the form σ rv = m ( v sin i ) b and then we scale itup to keep a conservative envelope that leave about 85% of thepoints below it. The fit is obtained using a Huber loss function(Huber 1964), which is more robust to outliers than squared lossfunction (Ivezi´c et al. 2014), and is shown as a dashed-dottedblue line in Fig. 6. We identified SB candidates using both se-lection criteria and further investigated the nature of any targetswith RV variation lying above either of those thresholds. We in-vestigated the true SB nature of any targets with RV variationsabove those thresholds (see Table 3 and Appendix A).
8. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY)
Large projected rotational velocity values could not only resultfrom a single fast rotator, but also from a blended profile of twoslower rotators. If the latter is the case, one would expect v sin i values varying in time depending on the system’s phase at thetime of the observations. To investigate any potential systemsof this kind, similarly to Fig. 6, we looked at the typical vari-ations in v sin i as a function of median v sin i . These resultsare shown in Fig. 7. Note that as our v sin i values are calcu-lated from a grid of rotational profiles with 1 km s − step, we areinsensitive to smaller variations and therefore many objects ap-pear to be constant. Following a similar approach to the one ofthe previous subsection, we calculated an upper envelopes to thevariations in v sin i and flagged systems above those levels forfurther inspection. v sin i, this work (km s ) v s i n i , t h i s w o r k ( k m s ) v sin i, this work + literature (km s ) v s i n i , t h i s w o r k + li t e r a t u r e + G D R ( k m s ) power law envelopev sin i binned 3 vsini Fig. 7.
Top panel : v sin i versus the standard deviation in v sin i for measurements calculated in this work. The 3 σ values, from3 to 45 km s − binned in 7 km s − bins, are shown by red solidlines. The power-law envelope is represented by dash-dottedblue line. Bottom panel : Same as upper panel, however, including values fromthe literature.
Another way to validate whether a RV variation is induced by abound companion is to include the BIS as an additional source ofinformation. Lagrange et al. (2013) used this technique search-ing for giant planets in a sample of 26 stars, some of which are in
Table 2.
Kinematic properties of previously identified close vi-sual binaries within our sample. ID σ rv v sin i Time span Num. obs P Ref.(km s − ) (km s − ) (day) (year)TWA 22 0.19 9.9 64 3 5.15 aHD 98800 0.07 < < ≈
75 . . . 1 11.74 e, f
Notes. a: Bonnefoy et al. (2009), b: Malkov et al. (2012), c: Bouchy, F.et al. (2009), d: Sato et al. (2009), e: Close et al. (2005), f: Nielsen et al.(2005), g: Torres et al. (1995) the young associations studied here. Significant anti-correlationbetween the BIS and RV suggests that the RV jitter is most likelydue to stellar activity (Desort et al. 2007). This technique relieson a large number of measurements per target and therefore inthis work we are limited to a small number of stars in our sam-ple. Therefore, in our case, this technique allowed us to rule outa few potential SBs rather than to identify new systems. The BISand RV values are listed in Table G.1.
We searched the literature to identify formerly flagged SBs fromour sample to assess the robustness of our method. For all previ-ously identified spectroscopic binaries, we recover a very largefraction of them (84% + − ). Most of the non-recovered SBs cor-respond to objects or systems with very few observations in ourlocal database, but for a few of the objects, our analysis contra-dicts the “SB flag” found in the literature (see Appendix A forcomments on the individual sources). Some multiple systems have the right configuration and are lo-cated at the right distance for them to be resolvable with directimaging techniques (with adaptive optics, AO hereafter) and, inaddition, display RV variations of the primary. A good exampleof such system is V343 Nor (Nielsen et al. 2016). Looking forsimilar cases, we compiled a list of targets from the literaturethat have AO-discovered known companions (typically, with es-timated periods of ≈ ffi cient time coverage in our databaseof high-resolution spectra to achieved the sensitivity needed todetect any companion-induced RV changes. However, the orbitsof all four systems have been determined in previous works, asnoted in Table 2. The final list of SB candidates identified in this work is pre-sented in Table 3. In a few cases, our analysis contradicts pre-vious claims of multiplicity from the literature, while in someother cases, we do not recover the SB nature of some candi-dates, which we attribute to the sampling of the data available tous (see details on Appendix A).
9. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY)
Out of the 381 objects from the compilation of our work, theliterature (Table 1) and Gaia DR2, we identified 68 SB candi-dates. For each candidate, we compiled all the information avail-able regarding RV and v sin i both from our work and the lit-erature and used those values to establish a final classificationregarding their multiplicity. The conclusion ( Conc. ) column ofTable 3 presents the summary of this analysis, where the values“Y”, “N” or “?” correspond to “multiple system”, “not a multiplesystem according to the data available”, or “inconclusive”.While specific comments for particularly interesting or chal-lenging candidates can be found in Appendix A, there were anumber of cases where the variable flag of v sin i turned out tobe a misleading diagnostic. In these cases, a closer inspection ofthe CCF profiles revealed that the variability was not real andjust induced by a poor fitting of the rotational profile. In suchcases, it is still possible that the candidate is an unresolved SB,but, since we do not have su ffi cient evidence to support that con-clusion, we flagged those candidates as inconclusive.
10. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY)
Table 3.
Properties of targets flagged as potential SB1 systems in the analysis presented in this work. Standard deviation are calculated for targetswith two or more epochs. Targets previously flagged but not recovered in this work are available in Appendix A. The new and recovered SB2 / SB3targets are available in Appendix A and Table G.4.
ID Values calculated in this work Values calculated in this work + literature median σ rv vsini median σ vsini RV median σ rv vsini median σ vsini Potential SB1 systems from variable RV and / or v sin i valuesCD-46 644 23.70 0.03 34.16 0.0 24.22 0.96 34.16 7.54 2 (4) NHD 17332 A 4.62 0.75 8.41 4.55 4.20 0.66 8.41 4.55 2 (4) ?CD-56 1032A 31.87 4.12 39.72 6.56 31.87 5.83 39.72 9.28 2 (2) YCPD-19 878 25.59 1.32 30.63 0.51 25.59 1.32 30.63 0.51 4 (4) ?TYC 7627-2190-1 21.94 3.03 12.95 12.85 21.94 3.71 24.98 14.88 3 (4) YV*PXVir -12.99 0.52 4.17 0.31 -12.39 5.81 4.16 0.35 4 (8) SB1 YHD 159911 21.77 0.63 58.4 12.02 21.77 0.63 58.4 12.02 3 (3) YCD-43 3604 17.5 2.35 18.0 2.19 17.43 2.66 18.0 9.52 4 (5) YV* V379 Vel 14.645 0.045 7.9 1.5 14.6 1.49 7.9 1.5 2 (3) ?TYC 8594-58-1 11.03 0.650 12.95 0.0 11.03 0.75 12.95 9.45 4 (5) N2MASS J12203437-7539286 4.86 0.02 7.9 1.5 4.86 2.47 7.90 2.37 2 (3) YHD 129496 -6.07 3.07 66.99 1.51 -6.07 3.07 66.99 1.51 2 (2) NV*AFLep 20.89 1.11 50.32 11.42 21.39 1.25 50.32 11.42 4 (5) NHD 139084 5.17 1.99 15.77 0.56 5.10 1.76 15.88 0.55 9 (11) SB1 YHD 139084 B 4.55 0.01 15.98 1.50 2.32 3.14 15.98 1.5 1 (2) NHD 164249 A -0.14 1.17 21.54 2.37 -0.09 1.06 21.03 2.25 8 (11) NHD 164249 B -0.6 0.28 12.95 6.06 -0.88 0.88 12.95 6.06 2 (3) NCD-31 16041 -8.81 0.20 40.22 3.78 -8.73 1.25 43.25 4.92 3 (4) NV*PZTel -2.99 2.96 55.23 12.55 -3.54 2.71 58.99 12.81 10 (12) NHD 199143 -22.73 . . . 58.40 . . . -13.62 12.89 92.95 48.86 1 (2) N*cEri 18.48 7.64 57.39 1.69 18.43 7.23 57.39 1.69 7 (8) NGJ 3305 23.91 0.49 5.88 0.48 20.95 1.57 5.88 0.48 3 (9) YHD 22213 11.27 3.14 40.73 0.51 11.27 3.14 40.73 0.51 2 (2) YHD 21997 17.17 0.86 65.47 9.05 17.24 0.91 65.47 9.05 3 (4) NV*AGLep 25.31 0.57 23.050 4.76 25.31 0.57 23.050 4.76 4 (5) ?CD-44 753 13.16 0.91 7.9 0.95 13.78 1.37 7.0 0.95 3 (6) NHD 104467 11.16 2.78 25.07 2.25 11.4 2.31 25.07 2.25 6 (8) Y2MASS J12020369-7853012 11.17 2.91 14.97 0.71 11.17 2.91 14.97 0.71 4 (4) SB1 YBD-184452A . . . . . . . . . . . . -19.31 2.01 8.05 4.59 0 (2) ?GSC 08057-00342 . . . . . . . . . . . . 13.5 5.59 5.2 . . . 0 (3) SB1 Y2MASS J04470041-513440 . . . . . . . . . . . . 17.92 1.98 5.1 . . . 0 (2) NUCAC3 33-129092 . . . . . . . . . . . . 7.07 2.86 10.5 . . . 0 (2) NUCAC4 110-129613 . . . . . . . . . . . . 3.58 6.24 25.1 . . . 0 (2) NCD-53 544 12.62 2.90 63.45 2.18 12.56 2.55 65.47 8.26 3 (5) NTYC8098-414-1 . . . . . . . . . . . . 19.53 8.72 11.75 9.40 0 (6) ?HD 207575 1.42 2.42 37.19 5.82 1.5 2.14 37.19 5.82 5 (7) ?HD 207964 23.46 0.2 53.86 1.52 23.26 12.65 53.86 1.52 2 (3) NTYC 9344-293-1 6.16 1.01 55.37 1.43 6.95 1.57 55.35 10.0 3 (6) NUCAC3 92-4597 . . . . . . . . . . . . -5.2 9.81 4.7 . . . 0 (3) SB YHD 3221 -2.39 3.26 68.5 5.01 -2.39 3.26 68.5 5.01 3 (3) NUCAC3 70-2386 . . . . . . . . . . . . 5.65 2.33 19.2 . . . 0 (2) SB YV* CE Ant 11.7 0.06 4.87 1.75 12.4 0.32 4.87 1.76 4 (17) NTWA23 10.82 0.04 9.92 3.0 7.71 2.61 9.92 3.0 2 (16) SB YUCAC2 1331888 -1.66 0.56 25.07 1.0 -2.22 2.01 25.80 1.09 2 (3) NHD 48189 36.14 0.01 16.99 1.5 33.40 2.06 17.29 0.43 2 (3) NCD-30 3394 12.71 2.39 37.69 0.50 14.99 2.84 37.19 0.87 4 (5) ?CD-30 3394B 13.94 3.21 47.79 2.71 15.09 3.24 47.29 4.07 4 (5) ?CD-52 9381 -13.85 2.74 39.71 1.23 -13.85 2.74 39.71 1.23 4 (4) NGSC 08350-01924 1.57 1.45 23.05 3.0 0.21 1.46 23.05 3.0 2 (4) NV*AFHor 12.91 0.06 7.90 1.5 12.70 1.13 7.90 1.58 2 (6) NRX J12204-7407 14.60 1.37 39.72 1.5 14.60 1.58 39.71 1.72 4 (4) N[FLG2003] eps Cha 7 13.64 1.24 23.05 0.47 13.64 1.24 23.05 0.47 3 (3) NHD 17250 10.51 0.54 42.24 0.82 9.73 2.92 42.24 1.01 3 (5) SB YHD 191089 -11.69 0.47 43.75 1.23 -11.18 3.13 43.75 1.42 4 (7) ?V* AO Men 16.02 0.22 16.69 0.44 16.02 1.63 16.69 0.44 8 (10) NHD 984 -2.21 1.95 39.26 1.45 -2.21 2.30 39.26 1.59 6 (8) NHD 37484 21.19 0.13 52.34 1.5 21.32 2.80 52.34 1.5 2 (3) N2MASS J01505688-5844032 . . . . . . . . . . . . 9.95 1.62 10.10 . . . 0 (2) NUCAC4 137-000439 . . . . . . . . . . . . 7.69 2.41 11.20 . . . 0 (2) ?2MASS J12560830-6926539 . . . . . . . . . . . . 11.31 3.53 16.30 . . . 0 (2) YBD-20 1111 19.26 0.72 24.06 4.54 18.68 1.00 24.06 5.56 3 (4) ?Smethells 165 5.98 0.72 20.02 0.47 6.04 0.69 20.02 4.04 3 (6) ?
11. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY)
7. Accounting for observation sensitivity
As we have seen through this work, tight binaries can be de-tected in spectroscopic data via identification of double (or mul-tiple) lines, variable RVs (or, unrelated to this work, even unex-pected mixes of spectroscopic features). However, our ability toidentify these features (multiple lines and variations in RV), canbe severely biased by factors such as: the observations strategy(time span T and number of measurements N obs ) and the inher-ent sensitivity of the spectrographs employed for the observa-tions. These factors have been thoroughly studied and modelledby Tokovinin (2014a). The steps incorporated in our analysis totranslate this knowledge into detection probability maps werethe following:1. We created a set of 10 ,
000 simulated binaries from the fol-lowing distributions: (cid:4)
Period ( p ): log-normal ( µ = σ = (cid:4) mass ratio ( q ): uniform (for system between 0.01-1.0 M (cid:12) ; Raghavan et al. 2010; Kraus et al. 2011; Elliottet al. 2015) (cid:4) Eccentricity ( e ), two-part: – p ≤
12 days, e = – p >
12 days, uniform (for 0 ≤ e ≤ (cid:4) Initial phase ( φ ), longitude of ascending mode ( ω ) andinclination ( i ): uniform (for 0 ≤ φ ≤
1, 0 ≤ ω ≤ π , and0 ≤ i ≤ π , respectively)2. From our simulations and using equations 5 to 7 fromTokovinin (2014a), we calculated a detection probabilitymap for each object characterised by its three detection pa-rameters ( N obs , T and σ RV ). In the case of single epoch data,we assumed the same artificial parameters used by Tokovinin(2014a) (i.e. T =
100 days, N obs =
3, and σ RV = − ),since we are still sensitive to double- and triple-lined multi-ple systems.3. The detection map of each object was calculated on the samemass ratio vs. period grid. This “common-grid” approach,makes it easy to average those maps for objects belonging tothe same moving group, yielding an average sensitivity mapper association in our sample, see Fig. 8.4. These “association-averaged” probability maps were used tocorrect our SB fractions from biases induced by the obser-vation strategy and precision. The correction was calculatedby taking the mean value in the parameter space 0 . ≤ q ≤ p ≤ . days. We excluded mass ratios smaller than0.1 as very few targets have any meaningful probability ofdetection in this parameter space (Fig. 8, color-scale fromred, 100%, to white, 0%).Note that these corrections are applied across the entire pa-rameter space and do not have assumptions regarding the under-lining mass ratio or period distributions (as we have extremelylimited information on both).
8. Updated census of spectroscopic binaries
Building from the previous sections, in Fig. 9, we present theSB fraction obtained for each associations as a function of themedian v sin i of its members. In that figure we present bothfractions, the original one that disregards the e ff ects discussed inSec. 7, and the “corrected” one (blue and red symbols, respec-tively). The uncertainties on the derived fractions are calculatedfrom binomial statistics (Burgasser et al. 2003). M a ss -r a ti o M a ss -r a ti o Fig. 8.
Upper panel : Average detection probabilities for THAassociation (contours from red, 100%, to white, 0%), detectedspectroscopic companions (white stars) and visual binaries(black crosses) in the physical separation versus mass ratio. Thesolid, dashed and dash-dotted lines encompass areas with detec-tion probabilities ≥ Bottompanel : Same as upper panel but for BPC association.As mentioned before, it is extremely di ffi cult to fully accountfor the e ff ect of v sin i on the sensitivity to identify SBs. Sincefast rotators may bias the resulting SB fractions, we opted to lookfor any relationship between the obtained SB and the median v sin i of the members of each association. No apparent correla-tion was found between those two quantities, and the distributionof v sin i values for each association are plotted in Fig. 10.A striking result from our study is that the SB fraction ob-tained for the TW Hya association seems to contradict the resultsfrom Elliott et al. (2014). This di ff erence is driven by the discov-ery of three newly identified SBs in this work, that was possiblebecause of an increase of 30% in the amount of data availablefor this association since Elliott et al. (2014). To test this resultagainst membership criteria, we compared the fraction estimatedusing the census obtained from the BANYAN Σ tool with that ofthe convergence method and both figures are fully compatible(see Fig. 11).Interestingly, the three highest SB fractions are found forthe three youngest associations ( ε Cha 18 + − %, TW Hya 22 + − %and β Pictoris moving group 24 + − % prior sensitivity correction,
12. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) and 22 + − %, 32 + − %, and 33 + − %, respectively, when the correc-tions of Sec. 7 are applied). This is unlikely to result from a lackof sensitivity due to large rotational broadening, as the median v sin i values are relatively low and similar (once the low-numberstatistics are taken into account) for the three associations (seeFig. 10). Furthermore, as shown in Fig. 11, the higher SB frac-tion of these associations seems to be insensitive to the member-ship criteria used, appearing also when the BANYAN Σ censusis employed. On the other hand, the average SB fraction for thefive older associations are (cid:46)
10% (with the possible “intermedi-ate” case of THA). It must be noted that the confidence intervalfor this “dichotomy” is only 1 to 2 σ given the associated largeuncertainties.
10 15 20 25 30 38
Median v sin i (km s ) S B f r a c t i o n ARGCOL OCTTHABPC ECH
ABDTWA
UncorrectedCorrected
Fig. 9.
SB fraction as a function of median v sin i . The uncor-rected SB fractions are shown in purple and in text next to thename of each association. The corrected SB fractions are shownin red. The primary mass range is 0 . ≤ M ≤ . M (cid:12) .
9. Discussion
The results presented in Section 8 suggest a counter-intuitivepath of evolution for SBs. In this section we compare our re-sults to the literature, discuss whether these results are in fact anartefact produced by our methodology or a physical result; and,in the latter case, if we are really witnessing early SB evolutionor the e ff ect of other environmental factors. Figure 11 shows SB fractions ( ≈ ≈ ≈ (cid:38)
20 Myr) across the mass range of ∼ . − . (cid:12) . On the other hand, the observed SB fractionsfor the three youngest associations seem to be larger than thosereported for the previously mentioned young regions of Tau-Aur (1 Myr) and Cha I (2 Myr). The estimated distances to theseyoung regions are ∼
140 pc and ∼
160 pc, respectively (Nguyen F r e q u e n c y ABD ARG F r e q u e n c y BPC COL F r e q u e n c y ECH OCT v sin i (km s ) F r e q u e n c y THA v sin i (km s ) TWA
Fig. 10. v sin i histogram for each young association from thiswork with primary mass range 0 . ≤ M ≤ . M (cid:12) . Age (Myr) S B f r a c t i o n COLOCTTHABPCECHARG ABDTWA
SACY SB fraction correctedBANYAN SB fraction corrected
Fig. 11.
Corrected SB fraction as a function of age (Myr) formembership estimation from our convergence method (bluedots, Torres et al. 2006; Torres et al. 2008) and BANYAN Σ (orange dots, Gagn´e et al. 2018a). The shaded area highlightsthe ≤
20 Myr zone of the figure. The primary mass range is0 . ≤ M ≤ . M (cid:12) .et al. 2012), therefore we argue that, given the overall closer dis-tance of our targets, the di ff erence should not rise from a lack ofsensitivity or a completeness bias in the SACY sample (see Sec.5 from Nguyen et al. 2012).
13. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY)
Nevertheless, the relative paucity of SBs in Tau-Aur andCha I could be explained by the sample used by Nguyen et al.(2012) which is concentrated on the higher stellar density re-gions of the clouds. For instance, Guieu et al. (2006) revisitedthe previously claimed brown dwarf deficit in the same Tau-Aurregion, performing a larger scale optical survey including thesurroundings of the clouds as well as their densest parts. The au-thors concluded that the possible deficit was in fact an artefactfrom target selection rather than a real di ff erence. Interestingly,Viana Almeida et al. (2012) derived an SB fraction of ≈
42% forthe Rho Ophiuchus star forming region ( ∼ . − ∼ . − . (cid:12) (Natta, A. et al. 2006)and a binary fraction of ≈
71% combining data from di ff erentworks. These results are more consistent with the SB fraction ofour youngest associations and are aligned with the notion thatmultiplicity is very high at young ages (younger than ∼ ff erence on SB frac-tion in Fig. 11 is weak, at the level of 1 to 2 σ , it is hard to recon-cile with the general picture of SB fraction remaining unchangedafter ∼ In Section 7 we created sensitivity maps from 10 ,
000 simulatedbinaries, to estimate how many binary systems would have beenmissed because of our observing strategy. The simulated bina-ries were drawn according to certain priors on the mass ratio,period, and orbital parameters, but those parental distributionswere originally estimated from field star surveys (Raghavan et al.2010; Tokovinin 2014a). Those priors may not be representativeof the underlying population of binary stars in young associa-tions ( (cid:46)
100 Myr). This may have consequences on the sensi-tivity corrections we obtained which may lead to an artificiallylarge corrected
SB fraction.The prior on the period distribution is the most critical one,as it has the most significant e ff ect on the detection probability(shorter periods are easier to detect using spectroscopic observa-tions). Taking this into consideration we created new sensitivitymaps using a log-normal period distribution ( µ = . σ = . / I sys-tems ( (cid:46) ∼
2% on the correction factor. This slight increase isnot su ffi cient to explain the di ff erence of (cid:38) −
20% betweenthe three younger association with respect to the older ones inour sample. We further tested the impact of the period distri-bution on the correction factor by taking an even more extremecase. We used a distribution centred at the smallest separationthat a primordial binary system could have ( ≈
10 au from discfragmentation Vaytet, N. et al. 2012), and even in that almost un-realistic scenario we did not reach a change of sensitivity su ffi -cient to justify the di ff erences of SB fractions between the youngand old associations in our sample. The analysis presented heresuggests that the di ff erences in SB fractions are not artificiallycreated by our sensitivity correction approach. From the SBs identified in this work, ∼ + − % are also partof higher-order multiple systems (Elliott et al. 2016a; Elliott &Bayo 2016). This shows a preference for SBs to be found intriple or higher-order systems, similar to the 63% reported inTokovinin et al. (2006) for field stars. There is observational evidence that suggests an overall de-crease of binary fraction from pre-MS ages to field ages (Ghezet al. 1997; Kouwenhoven et al. 2007; Raghavan et al. 2010).Elliott & Bayo (2016) suggested that dynamical interactionsof triple systems (as proposed by Sterzik & Tokovinin 2002;Reipurth & Mikkola 2012) could explain the population fromclose (0.1 au) to very wide (10 kau) tertiary components wherethe majority of the wide companions are in the process of beingdisrupted on timescales of 10 −
100 Myr. The results of Raghavanet al. (2010) also suggest that systems with long periods, or thosewho have more than two components, tend to lose companionswith age due to dynamical evolution. However, these mecha-nisms that would explain the disruption of wide companionswould not necessary explain the SB fraction in this sample. Infact, Tokovinin et al. (2006) suggested that the overall SB frac-tion seems to remain unchanged after ∼ ∼ + − % of SBsin the three youngest associations studied here are part of a tripleor high order multiple system in contrast with the ∼ + − % forthe five older associations. Our results hint that the youngest associations ( (cid:46)
20 Myr) mayhave a larger SB fraction, even though it remains tentative atthe moment. This result suggests a possible decrease of the SBfraction from ∼ ∼
100 Myr. A similar result was obtainedfor the IN-SYNC (INfrared Spectroscopy of Young NebulousClusters) sample from high resolution H-band spectra observa-tions of low-mass stars in Orion A, NGC 2264, NGC 1333, IC348, and the Pleiades (Jaehnig et al. 2017), where the SB frac-tion of the five pre-MS clusters ( ≈ −
10 Myr) was ≈ − ≈ −
10% found for the Pleiades ( ≈
100 Myr).Jaehnig et al. (2017) claim that the time sampling of their obser-vations make it more sensitive to the critical 10 − days pe-riod range where binary systems are wide enough to be disruptedby dynamical interaction over ∼
100 Myr timescale in dense en-vironments. However, this scenario is proposed for clusters withtypical densities of ≈ M (cid:12) pc − (at the core radius, Piskunovet al. 2007) and may not be compatible with the typical densitiesof ≈ .
01 stars pc − for loose associations such as the ones in theSACY sample (Moraux 2016). The tentative variations in SB fraction could be related to di ff er-ences in the primordial multiplicity depending on the formationhistory and environment of the associations. In Figure 12, weshow the sub-spaces of the UVWXYZ-space for all the associa-tions studied in this paper, to search for possible signs of cluster-ing in both velocity and spatial coordinates. Given the proximityof the SACY associations no clear separated groups of pointsappear for the spatial coordinates (Torres et al. 2006). However,it is more informative to plot the galactic proper motion to tracea possible common origin (UVW: positive toward the Galacticcenter, Galactic rotation and North Galactic Pole respectively).Qualitatively, we identify possible clustering of points in theUVW sub-spaces (first row of Fig. 12) for the three youngestassociations (blue coloured symbols) that may suggest possiblecommon birth place in the Galactic bars for these associationscompared to the older ones.
14. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY)
25 20 15 10 5
U (km s ) V ( k m s )
25 20 15 10 5
U (km s ) W ( k m s )
30 25 20 15 10 5 0
V (km s ) W ( k m s ) ABDARGBPC COLECHOCT THATWA200 100 0 100 200
X (pc) Y ( p c )
200 100 0 100 200
X (pc) Z ( p c )
200 100 0 100 200
Y (pc) Z ( p c ) Fig. 12.
Combinations of the sub-spaces of the UVWXYZ-space for the young associations in the SACY sample. The blue colouredsymbols correspond to the three youngest associations (BPC, ECH and TWA). The full membership study and further analysis willbe presented in Torres et al. (in prep.).Furthermore, previous studies have found evidence that thethree associations, β Pictoris, TW Hya, and ε Cha possiblyformed in or near the Sco-Cen giant molecular cloud 5 −
15 Myrago (Mamajek & Feigelson 2001; Torres et al. 2008). Then thedi ff erence in the SB fraction presented in this work could arisefrom di ff erent primordial multiplicity instead of being caused bytheir dynamical evolution. In support of the latter argument, theoverall binary fraction in Sco-Cen is ≈
93% among solar-typestars and ≈
75% among low-mass star (Kouwenhoven 2006).These figures are higher than the overall binary fraction for solar-type and low-mass stars in Tau-Aur reported by (Kraus et al.2011, ∼ − ff erent binary parameter spaceexplored). In addition, Clark Cunningham et al. (2020) recentlyclaimed that the ABD association may be kinematically linked toa newly discovered “stellar string” Theia 301. Kounkel & Covey(2019) argue that although they recover Sco-Cen in their kine-matic clustering searches, this association is di ff erent than the“typical strings” such as Theia 301.To summarise, there are hints supporting non-universal mul-tiplicity, however, our current data-set does not allow us to con-firm di ff erent environmental star formation history among theSACY associations.
10. Summary and conclusions
In this work we have presented an update of the SB census forthe associations within SACY. The study is based on new ob-servational data (as well as literature and archival data), but alsonew criteria to identify these tight binaries. We have estimatedradial and rotational velocity for 1375 spectra using CCFs andcompiled ∼
400 RV measurements from literature (including Gaia DR2, Gaia Collaboration et al. 2018). Our RVs and v sin i estimates are in good agreement with previously published val-ues, following a 1:1 relation with values in literature (for targetsthat are not identified as a multiple systems), demonstrating thatour CCF analysis is robust. Further robustness is provided bythe fact that we have recovered the 84 + − % of previously knownmultiple systems.Besides RV variations as keys to identify SB candidates, weused high-order cross-correlation functions as a complementarydiagnostic tool. These features o ff er a concrete way to quantifythe symmetry, curvature and quality of the fitting of the CCFs.More epochs do not only allow to improve the reliability of anyRV variation, but it also allows for other statistics to be usedwhen assessing the binary nature of a candidate (see Sec. 6.3 forinstance).We have calculated the SB fraction for each SACY associa-tion and have estimated a correction factor taking into accountpossible sensitivity issues and biases from the observations (seeSec. 7). The summary of SB candidates can be found in Tables3 and G.4. The analysis and conclusions reached for each targetflagged as a candidate can be found in Appendix A.We find that the three youngest associations have over-all higher SB fractions ( ε Cha 22 + − %, TW Hya 32 + − % and β Pictoris moving group 33 + − % when the corrections of Sec. 7are applied) compared with the five oldest associations in theSACY sample ( ∼ −
125 Myr) which are ∼
10% or lower. Thisresults seems to be independent of the method used for member-ship assessment (see Fig. 11) and not artificially created by thesensitivity correction approach (see Sec. 9.2). In addition, morethan 90% of the SB identified in ε Cha, TW Hya and β Pictorisare part of a triple or hierarchical system in contrast with ≈
15. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) of the five older associations. While the di ff erence in SB frac-tion remains tentative at the moment, we propose two possibleexplanations: an evolution e ff ect (previously reported in denserenvironments), and a primordial non-universal multiplicity. Withthe data available nowadays we cannot distinguish between thetwo possibilities. Acknowledgements. The authors would like to thank the anonymous refereefor constructive comments that helped to improve the content and clarity ofthis paper. S.Z-F acknowledges financial support from the European SouthernObservatory via its studentship program and ANID via PFCHA / DoctoradoNacional / a community-developed core Python packagefor Astronomy (Astropy Collaboration et al. 2013, 2018). This research hasmade use of the SIMBAD database and VizieR catalogue access tool, CDS,Strasbourg, France. The original description of the VizieR service was pub-lished in Ochsenbein et al. (2000). This research has made use of the servicesof the ESO Science Archive Facility, based on data products created from ob-servations collected at the European Organisation for Astronomical Researchin the Southern Hemisphere under ESO programmes 077.B-0348, 086.A-9014,088.A-9007, 077.D-0712, 090.D-0061, 091.D-0414, 082.D-0933, 077.C-0138,078.A-9059, 084.A-9004, 094.A-9012, 077.C-0573, 083.A-9004, 084.B-0029,077.A-9005, 082.A-9007, 078.C-0378, 079.A-9017, 060.A-9700, 083.A-9003,077.C-0192, 079.A-9007, 086.A-9006, 078.D-0080, 085.A-9027, 080.A-9006,090.A-9013, 089.A-9007, 093.A-9029, 084.A-9003, 082.C-0446, 086.D-0460,087.C-0476, 090.C-0345, 077.D-0478, 086.A-9007, 090.A-9003, 090.A-9010,089.D-0709, 077.C-0258, 079.A-9002, 078.A-9048, 077.A-9009, 078.A-9058,079.A-9006, 092.A-9007, 093.C-0343, 095.C-0437 and 097.C-0444. Fundingfor the TESS mission is provided by the NASA Explorer Program. Funding forthe TESS Asteroseismic Science Operations Centre is provided by the DanishNational Research Foundation (Grant agreement no.:DNRF106), ESA PRODEX(PEA 4000119301) and Stellar Astrophysics Centre (SAC) at Aarhus University.This work has made use of data from the European Space Agency (ESA) missionGaia, processed by the Gaia Data Processing and Analysis Consortium (DPAC).Funding for the DPAC has been provided by national institutions, in particu-lar the institutions participating in the Gaia Multilateral Agreement. Data wereobtained from the Mikulski Archive for Space Telescopes (MAST). STScI isoperated by the Association of Universities for Research in Astronomy, Inc., un-der NASA contract NAS5- 2655. This research has made use of the WashingtonDouble Star Catalog maintained at the U.S. Naval Observatory. References
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17. Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) , Online Material p 1
Appendix A: Notes on individual sources
A.1. Sources flagged variable in this work
CD-46 644 : This target was flagged due to variation in its v sin i value. The CCF profile is somewhat asymmetric however, theevidence is not strong enough to confirm its spectroscopicbinary nature. Therefore, it was rejected as a spectroscopicbinary. HD 17332 A : This target has two UVES observations and nosignificant radial velocity variation. However, its v sin i valuewas calculated to be 13 and 4 km s − in the two epochs. Closerinspection of the CCF profile shows that the profile is wellfitted. However, given we only have two epochs we cannotconclude whether this change is due to a companion or inherentvariability of the star. Therefore at this time we flag the systemas a questionable SB, flagged for further investigation. CD-56 1032A : This target has two UVES observations produ-cing radial velocity values of 35 .
99 and 27 .
75 km / s − . The targetis a relatively fast rotator ( v sin i ≈
40 km s − ) but the rotationalprofile is well fitted considering. Therefore we flagged thistarget as a spectroscopic binary. CPD-19 878 : This target shows variation in radial velocity.However, given we only have four epochs we cannot concludewhether this change is due to a companion or inherent variabil-ity of the star. Therefore at this time we flag the system as aquestionable SB, flagged for further investigation.
TYC 7627-2190-1 : This target shows significant variation inradial velocity from both our observations and those includingliterature values. Closer inspection of its CCF profile revealsthat it is likely a merged double-lined spectroscopic binary.
V*PXVir : This is a known single-lined spectroscopic binarywith an orbital solution ( P = . ± .
06 day), presentedin Gri ffi n (2010). In this work, when combined with literaturevalues, the system was flagged as variable. HD 159911 : This target was flagged as having high v sin i variation. Despite it has a high v sin i value ( ≈
58 km s − ) itsCCF profile is well fitted and therefore it is flagged as a potentialSB1 system. CD-43 3604 : Its CCF profile has two clear peaks at di ff erentdepths and the centre of the single Gaussian fit moves signifi-cantly from epoch to epoch. The target’s rotational broadening ispoorly constrained due to the merged double-peak nature of theprofile. This target is likely a merged double-lined spectroscopicbinary. V* 379 Vel, TYC 8594-58-1, HD 37484 : These targets wereflagged due to variation in its radial velocity when a literaturevalue was included. Given that the variation come only forone extra epoch, there is not enough evidence to establish theorigin of this variation. Therefore, these targets are rejected as aspectroscopic binary for now. : This target only has three obser-vations (two presented here, the other from Torres et al. 2006).However, given its low v sin i value ( ≈ − ) the di ff erencein radial velocities (0 . . − ) is significant. HD 129496 : This target was initially flagged as having po-tentially variable radial velocity, however it has a very high v sin i value ( ≈
67 km s − ). It’s CCF profile is poorly fitted andtherefore it is rejected as a spectroscopic binary. CD-52 9381 : This target has a high v sin i value( ≈
40 km s − ) and was flagged due to radial velocity vari-ation ( σ rv = .
75 km s − ). A closer inspection of its CCFreveals that the profile is asymmetric however, there are not twodistinguishable peaks. At this time we reject this target as aspectroscopic binary. V*AFLep : This target was flagged due to variation in its v sin i value from 3 measurements. The CCF profile is somewhatasymmetric however, the evidence is not strong enough toconfirm its spectroscopic binary nature. Therefore, it wasrejected as a spectroscopic binary. HD 139084 : This is a known single-lined spectroscopic andclose visual binary. The orbital solution of this system wasrecently presented in Nielsen et al. (2016). The period of thesystem is 4.576 yr putting it on the limit of detectability, seeFig. 8.
HD 139084 B : This target is a fast rotator ( v sin i ≥
50 km s − )and only has two observations (one presented here and otherfrom Torres et al. 2006). For that reason, there is not enoughevidence to establish the origin of the variation. Therefore, thistarget is rejected as a spectroscopic binary. HD 164249 B : This target was flagged for potential variable v sin i values. However its CCF profiles are poorly fitted andtherefore it was rejected as a spectroscopic binary. CD-31 16041 : This target was flagged due to variation inits v sin i value from 3 measurements. The CCF profile issomewhat asymmetric however, the evidence is not strongenough to confirm its spectroscopic binary nature. Therefore, itwas rejected as a spectroscopic binary. V*PZTel : This target was flagged due to variation in its v sin i value. However, it is a very fast rotator ( v sin i
64 km s − )and its CCF profile is poorly fitted, there it was rejected as aspectroscopic binary. HD 191089 : From our measurements alone this target would notbe flagged as variable. However, with the inclusion of literaturevalues it’s radial velocity significantly changes. There are twoseparate measurements (Gontcharov (2006): -5.9 km s − andDesidera et al. (2015): -6.4 km s − ). The values calculated fromour 3 UVES observations are -12.18, -12.14 and -11.24 km s − .In Grandjean et al. (2020) analysis this source was flaggedas a variable due to stellar pulsations. Therefore at this timewe flag the system as a questionable SB, flagged for furtherinvestigation. HD 199143 : This target is a fast rotator and has been flaggedfor both variable v sin i value and radial velocity. The valuecalculated in this work is v sin i ≈
58 km s − , compared to thatof Torres et al. (2006), 128 km s − . Closer inspection of itsCCF shows that our fit of rotational broadening is most likelyunderestimated due to the velocity span of the CCF fit (-180– +
180 km s − ). Therefore the value of 58 km s − should betreated as a conservative lower limit. Additionally the profile is . Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) , Online Material p 2 extremely noisy and poorly fitted by both a Gaussian for its ra-dial velocity value and the rotational broadening profiles. Giventhese limitations the system was rejected as a spectroscopicbinary. *cEri : This target is a very fast rotator ( v sin i ≈
57 km s − ).Additionally, its CCF is very noisy and poorly fitted. Therefore,it is likely that the apparent radial velocity variation is notphysical and the result of a poorly constrained profile. Thissystem is rejected as a spectroscopic binary. GJ 3305 : Given its low v sin i value ( ≈ − ) its radialvelocity variation ( σ rv ≈ − ) is well above the thresholdfor identifying it as a spectroscopic binary. HD 22213 : This target has two UVES observations producingradial velocity values of 8.13 and 14.41 km s − . The target isa relatively fast rotator ( v sin i ≈
41 km s − ) but the rotationalprofile is well fitted considering. Therefore we flagged thistarget as a spectroscopic binary. V*AGLep : This target has three UVES observations and nosignificant radial velocity variation. However, its v sin i valuewas calculated to be ∼
23 and 33 km s − between the threeepochs. Closer inspection of the CCF profile shows that firstly,for a relatively fast rotator the profile is well fitted. However,the shape changes significantly between the two epochs (thebisector slope, curvature and bisector inverse slope changedramatically). However, given we only have two epochs wecannot conclude whether this change is due to a companion orinherent variability of the star. Therefore at this time we flag thesystem as a questionable SB, flagged for further investigation. HD 21997 : This target was flagged as having variable v sin i ,however, given the associated uncertainty and high v sin i valuethis variation is not significant. CD-44 753 : This target were flagged due to variation in itsradial velocity when a literature value was included. Given thatthe variation come only for one extra epoch, there is not enoughevidence to establish the origin of this variation. Therefore, thistargets is rejected as a spectroscopic binary for the moment.
HD 104467 : This target was flagged due to significant radialvelocity variation. The v sin i value of the target is ≈
25 km s − ,and the profile is well fitted. Therefore this system is flagged asa spectroscopic binary. : This target was flagged due tosignificant radial velocity variation. The v sin i value of thetarget is ≈
15 km s − , and the profile is well fitted. This targetwas previously flagged as a single-lined spectroscopic binaryin Elliott et al. (2014). Therefore this system is flagged as aspectroscopic binary. BD-20 1111 : We have 3 UVES observations of this target and ithas been flagged as having a variable v sin i value. The shapeof the profile significantly changes between 2 epochs resultingin the di ff erent v sin i values of 25 and 15 km s − . Given thatwe only have 3 epochs currently we cannot assess whether thisasymmetry is a result of the star’s changing surface or of aphysically bound companion. Therefore at this time we flag thetarget as a questionable SB system. CD-66 395 : This target is a very fast rotator ( v sin i ≈
60 km s − ).Additionally, its CCF is very noisy and poorly fitted. Therefore,it is likely that the apparent radial velocity variation is notphysical and the result of a poorly constrained profile. Thissystem is rejected as a spectroscopic binary. BD-184452A : This target only has two v sin i observations fromTorres et al. 2006 and one RV value from Gaia DR2. Thereforeis not enough evidence yet to establish the origin of the vari-ation. At this time we flag the target as a questionable SB system. GSC 08057-00342 : This target has 3 radial velocity values inthe literature from Rodriguez et al. (2013), Malo et al. (2014),and Kraus et al. (2014). Given its low v sin i value ( ≈ − )its large radial velocity variation ( σ rv ≈ − ) is well abovethe threshold for identifying it as a spectroscopic binary. Thisobject was also independently identified as a SB by Flagg et al.(2020). HD 17250 : This target has 3 RV from UVES observations and2 from literature (Gontcharov 2006; Gaia Collaboration et al.2018). This object is the main star of a quadruple system withtwo visual companions and was flagged as an SB by (Tokovinin& Horch 2016). : These targets only has two observations (one fromGDR2 and other from Kraus et al. 2014). There is not enoughevidence yet to establish the origin of the variation. Thereforethese target are rejected as a spectroscopic binary.
CD-53 544 : This target was flagged due to variation in RV and v sin i values. The CCF profile is somewhat asymmetric howeverthe evidence is not strong enough to confirm its spectroscopicbinary nature. TYC8098-414-1 : There are 6 available radial velocity measure-ments for this system. Five of these six measurements wouldgive an RV ∼ − , which would not be flagged as SBcandidate. However, the inclusion of one value from Kraus et al.(2014) of -1.60 km s − makes the apparent variation significant.It is di ffi cult to assess these individual values given the availableinformation. At this time, the system is flagged as a potentialSB for further investigation. HD 207575 : This target shows variation in radial velocity and v sin i value. The CCF profile shows that the shape changebetween the epochs (the bisector slope, curvature and bisectorinverse slope). However, given we only have five epochs wecannot conclude whether this change is due to a companion orinherent variability of the star. Recently, Grandjean et al. (2020)flag this source as a variable due to pulsations from HARPSobservations. Therefore, this target is rejected as a spectroscopicbinary. HD 207964 : This targets only has three observations (one fromGDR2 and two from our work). Given that there is not enoughevidence to establish the origin of the variation. Therefore, thistarget is rejected as a spectroscopic binary.
TYC 9344-293-1 : This object has a variable number of v sin i values. The values are 61 km s − (Torres et al. 2006), 59.5, 65.4and 67.5 km s − (Malo et al. 2014) and 55, 55, and 58 km s − (this work). The most di ff erent was the value of 33.1 km s − . Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) , Online Material p 3 published in Kraus et al. (2014). This system was tagged asa rotational variable but for the moment rejected as potentialspectroscopic binary.
UCAC3 92-4597 : This target was previously flagged as a SBin (Malo et al. 2014). In this work, the system was flagged as avariable using the literature values.
CD-30 3394, CD-30 3394B : These objects was flagged dueto RV variation. The CCF profile shows that the shape changebetween the epochs (the bisector slope, curvature and bisectorinverse slope). However, given we only have four epochs wecannot conclude whether this change is due to a companionor inherent variability of the star. At this time, the systems areflagged as a potential SBs for further investigation.
HD 3221 : This target is a very fast rotator ( v sin i ≥
68 km s − )and its profile is extremely noisy and poorly fitted. For thatreason the radial velocity variation is likely non physical.Therefore, this target is rejected as a spectroscopic binary. SCRJ0103-5515 : This target was previously flagged as a doubleor multiple star in WDS. In this work, the system was flaggedas a variable using the literature values from (Malo et al. 2014)and (Kraus et al. 2014).
V* CE Ant : This target was flagged due to variation in its v sin i value from our measurements. The CCF profile issomewhat asymmetric however, the evidence is not strongenough to confirm its spectroscopic binary nature. Therefore, itwas rejected as a spectroscopic binary. TWA23 : This target has 16 individual radial velocity mea-surements (the majority from Bailey et al. 2012) and showssignificant radial velocity variation. Although we only have oneobservation, from UVES, the profile is consistent as resultingfrom a merged SB2 system. There is a significant asymmetryat approximately half the depth of the profile, causing a largebisector slope. Therefore this target is flagged as an SB2 system.
V* AO Men : This target was flagged due to variation in itsradial velocity when a Gaia DR2 value was included . Given thatthe variation come only for one extra epoch, there is not enoughevidence to establish the origin of this variation. On the otherhand, Grandjean et al. (2020) estimated that the variation wasdue to stellar activity (spots). Therefore, this target is rejected asa spectroscopic binary.
HD 984 : This target was flagged due to variation in its radialvelocity when a Gaia DR2 value was included. Johnson-Grohet al. (2017) calculated the orbit of this system as ∼
70 yr,which is outside outside the region where a visual binary canbe detected through radial velocity variation given ∼
10 yrmeasurements. Therefore, although this object is a visual binaryit cannot be flagged as a spectroscopic binary. : Thesetargets were flagged due to variation in its radial velocity fromtwo literature values (Kraus et al. 2014; Gaia Collaboration et al.2018). Shan et al. (2017) did not find sign of companion fromadaptive optics observations conducted on the 6.5 m MagellanClay Telescope for these objects. UCAC4 137-000439 wasnoted as potential tight binary in Janson et al. (2017) with anestimated separation of ∼ . (cid:48)(cid:48) . 2MASS J01505688-5844032 is rejected as a spectroscopic binary for the moment and UCAC4137-000439 is flagged as a potential SB for further investigation. : This target only has two obser-vations (one from Torres et al. 2006 and another from GaiaDR2). Elliott et al. (2015) probed binarity in this object byhigh-resolution imaging with an estimated angular separationof 0 . (cid:48)(cid:48) , physical separation of 13.1 AU and mass ratio of0 .
55. This object is at the boundaries of the region where avisual binary can be detected through radial velocity variationgiven ∼
10 yr measurements. At this time we flag the target as aquestionable SB system.
Smethells 165 : This target was previously flagged as a doubleor multiple star in WDS. In this work, the system was flagged asa variable using the v sin i values from literature. The variationcame from one v sin i measurement from Kraus et al. (2014).At this time we flag the target as a potential SB for furtherinvestigation. A.2. Sources previously flagged as spectroscopic multiplesystems not recovered in this work
CD-29 4446 : This is a known binary system with an orbitalsolution presented in Rodet et al. (2018). In this work, thesystem was flagged as a variable using the literature values.
V* V1005 Ori : This target was flagged as an SB1 system inElliott et al. (2014). The compilation of further radial velocitiesdo not show significant radial velocity variation caused by acompanion.
HD 98800A : Torres et al. (1995) calculated the orbit of this SB1system as 262 day. In the results presented here we only have 2radial velocity values which are 4 days apart and therefore didnot detect any significant change in velocity. This is one of thefew clear spectroscopic systems missed by our analysis.
CD-33 7795 : This target is a known triple system with com-panions at ≈ (cid:48)(cid:48) (Macintosh et al. 2001) and 2 (cid:48)(cid:48) (Webb et al.1999). Konopacky et al. (2007) calculated the orbit of the innersystem as 5.94 ± ∼
10 yr measurements. However, this object isa fast rotator ( v sin i ≈
50 km s − ) and only has 2 epochs ofradial velocity data which do not show significant variation.Therefore, although this object is a visual binary it cannot beflagged as a spectroscopic binary. HD 13183 : This target was flagged as a potential SB1 system inthe CORAVEL database (Nordstrom et al. 1996). Furthermore,Cutispoto et al. (2002) found evidence for significant radialvelocity variation. From our compilation of values this systemdoes not exhibit significant variation given its rotational velocity( v sin i ≈
24 km s − ), however it does have an asymmetricalCCF profile. Given the previous notes in multiple other worksthis system is flagged as a spectroscopic binary. . Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) , Online Material p 4
A.3. Double- and triple-lined spectroscopic binaries
Double and triple-lined spectroscopic multiple systems canbe identified from a single epoch of data, and are essentiallyconfirmed as multiple systems with one detection. For thatreason the notes below on each system are brief, with referencesto their original discovery where applicable.
HD 67945 : This target was flagged as a potential SB2 system inTorres et al. (2006). However, given its extremely fast rotation v sin i ≥
58 km s − and extremely noisy CCF profile we do notfind su ffi cient evidence to confirm that. Additionally it doesnot have significant radial velocity variation. Therefore, it wasrejected as a spectroscopic binary. HD 155177
There are 3 individual radial velocity values forthis target with uncertainties < − , two of which arecalculated in this work. Both the shape ( b b , c b and BIS ) and thepeak of the CCF profile change significantly in the 2 observa-tions. Therefore, this system is flagged as a spectroscopic binary.
GSC 06513-00291 : Malo et al. (2014) flag this system as anSB2 and quote values of 12.1, 21.6 and 2.4 for v sin i of thistarget from three observations. Interestingly the RV values fromthe three epochs 22 and 23.9 and 22.8 do not vary significantly.This target has a companion at ≈ (cid:48)(cid:48) . Therefore, it is likely anSB3 system. The companion at 0.1 (cid:48)(cid:48) (3 au using a trigonometricdistance of 29.4 pc, Riedel et al. 2014) would have a period > ff erence unless the orbit was extremely eccentric. This systemis therefore flagged as an SB3. V4046 Sgr : This target is a well known SB2 system, the orbitalsolution was presented in R. Quast et al. (2000). We recoverboth components of this system in all CCF profiles.
LP 476-207 A : This is a known SB2 system whose orbitalsolution was presented in Delfosse et al. (1999). We recoverboth components of this system in all CCF profiles.
Barta 161 12 : We do not have our own observations of thistarget and therefore cannot further investigate the spectroscopicbinary-nature of this object with our measurements. However,Malo et al. (2014) reported this target as an SB2 system. Thereare multiple radial velocity measurement that show apparentvariation, however, it was not recovered in our analysis asthe majority of measurements have uncertainties larger than3 km s − . This target is therefore flagged as a spectroscopicbinary. HD 217379A : This is a previously discovered SB3 system(Elliott et al. 2014). More recently Tokovinin (2016) presentedan orbital solution for both the inner and outer system. Werecover all three components of this system in our CCF profiles.
TWA 3A : This target was flagged as an SB2 system in Maloet al. (2014) We do not have further observations from UVES,FEROS or HARPS. However, from our compilation of radialvelocities this system has significant radial velocity variation.
UCAC3 112-6119, UCAC3 92-4597 : Kraus et al. (2014)flagged these two targets as an SB2 systems. We do not havefurther observations from UVES, FEROS or HARPS. However,from our compilation of radial velocities these systems have significant radial velocity variation.
HD 309751, HD 33999 : These two systems were previouslyreported in Elliott et al. (2014) and recovered in this analysis.
HD 36329 : This SB2 system was previously reported in Torreset al. (2006) recovered in this analysis.
TYC 8098-414-1 : Kraus et al. (2014) noted this target as anSB2 system, however, we do not recover the component in ouranalysis. Most likely the companion is not detected as its fluxratio is to low in our optical spectra. Malo et al. (2014) alsonoted that their v sin i value did not agree with the literaturevalues and mentioned that this could be an unresolved spectro-scopic binary. Given this information the system is flagged asan SB2 in our analysis. HD 199058 : Chauvin et al. (2015) noted this object as a binaryor multiple system. In this work we flagged this target as an SB2.
TYC 6872-1011-1, BD-20 951, GSC 08077-01788, UCAC3116-474938, V* V1215 Cen, HD 36329 : To the best of ourknowledge these systems have not previously been reported inthe literature. All are newly discovered SB2 systems.
Appendix B: Measurements of v sin i
B.1. Calibrating using CCF width
In the case of slow rotators ( v sin i (cid:46)
20 km s − ) there is asignificant contribution to the width ( σ obs ) of the cross correla-tion function (CCF) from non-rotation related broadening mech-anisms which can either be inherent to the star (e ff ective temper-ature and turbulence) or from the instrument that is used for theobservation. The width of the CCF profile is described by: σ = σ − σ (B.1)where σ obs is the width of the resultant CCF profile, σ rot isthe rotational broadening of the star and σ is the width of a non-rotating star, which can be very well expressed as a function ofcolour.Beyond ≈
20 km s − the width of the CCF profile is domi-nated by the rotation of the star and therefore these e ff ects be-come small or negligible. Note that within our sample of objectsthere are very few measurements with FEROS or HARPS with v sin i values ≥
20 km s − .The v sin i value can be expressed as (Queloz et al. 1998): v sin i = A (cid:113) σ − σ (B.2)where A is the coupling constant, calibrating one set of CCFmeasurements to previously calibrated v sin i values.First, to determine the value of σ we computed the lowerenvelope of points in a V − K versus σ obs diagram, see Fig. B.1for an example using UVES observations. The envelope was fit-ted with a polynomial and is shown as the dotted line. This issimilar to the technique used in Melo et al. (2001) and Boisseet al. (2010). We used this σ value for each star with its respec-tive V − K colour and found the slope (and o ff set) between pub-lished v sin i values and our calculated A (cid:113) σ − σ values. Notethat in this analysis we used CCF profiles with low fit residualsin order to better constrain the results. . Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) , Online Material p 5
Figure B.2 shows the resultant relation for observations us-ing UVES. We have highlighted 3 regions of the Fig. to guide thereader’s eye. Below ≈ − , in the case of UVES, σ ≈ σ obs and therefore this is our reliable lower limit on v sin i values.Between ≈ − the 1:1 linear relation su ffi ciently de-scribes the majority of our data. . . . . . . . V − K (mag)51015202530 σ ( k m / s ) Fig. B.1. V − K colour versus σ (the observed width of the CCFprofile) for all individual UVES observations. The dotted linerepresents a polynomial fitted to the lower envelope of thesemeasurements. A q σ − σ (km/s)0510152025303540 v s i n i , lit e r a t u r eca li b r a t e d ( k m / s ) Fig. B.2. A (cid:113) σ − σ versus literature v sin i values for UVESobservations. Three regions are highlighted. From left to right:Our lower limit on reliable v sin i values (6 km s − ), the interme-diate range (6-20 km s − ) where the 1:1 relation should hold andthe fast rotator range ( >
20 km s − ). The dotted line representsthe 1:1 relation between the two sets of values. Figure B.2 shows that, at least in the case of UVES obser-vations this calibration is relatively successful as the literature v sin i values match the A (cid:113) σ − σ value. However, in the caseof FEROS and HARPS we were unable to perform the sameanalysis successfully. Due to the smaller number of objects anaccurate calculation of σ was severely inhibited. With this inmind, below we outline an alternative approach to v sin i calcu-lation. B.2. Calibrating using rotational profiles
We directly compared our calculated values using rotational pro-files to published values. We used v sin i with published uncer-tainties < − in this analysis. Figure B.3 shows the resultsfor UVES, FEROS and HARPS in the left, middle and right pan-els, respectively. A linear relation ( y = mx + c ) was fitted to eachset of points and was used to calibrate our values. v sin i , CCF, UVES (km/s)05101520 v s i n i , lit e r a t u r e ( k m / s ) . x + − . v sin i , CCF, FEROS (km/s)05101520 . x + . v sin i , CCF, HARPS (km/s)05101520 . x + . Fig. B.3. v sin i values from fitted rotational profiles versus liter-ature v sin i values. The left, middle and right panels show mea-surements for UVES, FEROS and HARPS observations. The lin-ear relation ( y = mx + c ) is shown for each set of measurements. v sin i , HARPS (km/s)0510152025303540 v s i n i , UV E S ( k m / s ) v sin i , FEROS (km/s)0510152025303540 v s i n i , UV E S ( k m / s ) v sin i , HARPS (km/s)0510152025303540 v s i n i , F E R O S ( k m / s ) Fig. B.4. v sin i values calculated in this work for each pair ofinstruments. Left, middle and right panels are HARPS versusUVES, FEROS versus UVES and HARPS versus FEROS, re-spectively. The 1:1 relation in each case is plotted as the dottedline.To verify this relationship we performed an internal check bycomparing v sin i values for objects that were observed with atleast 2 of the 3 instruments. Figure B.4 shows the results of thiscomparison for each pair of instruments. Given typical uncer-tainties on v sin i values are 1-2 km s − (Melo et al. 2001; Maloet al. 2014) the resultant 1:1 relationships adequately describeour data. The advantage of this calibration technique is that thelinear relation can be applied to all stars in our sample. However,in the case of the technique described in Section B.1, a V − K value is needed and some stars in our sample do not have reli-able V magnitudes. Additionally, our stars cover the age range ≈ ff erent evolutionarystages, which could hinder a robust σ calculation. . Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) , Online Material p 6
B.3. v sin i lower limit From our calibration of v sin i values described in the previoussection we arrive at lower limits of 0.83, 4.47 and 8.36 km s − us-ing a star rotating with a projected rotational velocity of 1 km s − for UVES, HARPS and FEROS, respectively. However, as high-lighted in Section B.1, a more realistic lower limit on v sin i values for UVES is 6 km s − , where σ ≈ σ obs . B.4. Limitations on v sin i measurements of extremely fastrotators In the case of very large rotational broadening( v sin i ≥
60 km s − ), some stars’ v sin i values can be un-derestimated. This is due to the width of the profile approachingthe width of the velocity span used in the CCF calculation.This causes a lack of continuum and when the profile is fittedthe outer wings of the profile can be wrongly ignored. Forfast rotators in our sample ( v sin i ≥
50 km s − ) we reran ourCCF calculation using a wider velocity window of -250 to +
250 km s − . Even with this broader window some star’s CCFprofile widths were still underestimated. In these cases we useour calculated value as a lower limit. B.5. Measurement uncertainties on v sin i values We compared our calibrated v sin i values with the fitted linearrelation (see Section B.2) and calculate the quadratic sum of theerror as tracer of uncertainties. We set three uncertainties valuesbased on three order of magnitude from residuals. These valueswere selected from the mean uncertainty value from the errorsbetween the calibrated v sin i and the fitted linear relation oneach range of profile fit residuals (see Fig. B.5). v sin i , calibrated (km/s)10 − − − R o t a ti n a l p r o fi l e fi t r e s i du a l Fig. B.5.
The rotational profile fit residual as a function of cal-ibrated v sin i values. The v sin i uncertainties value is defineddepending on the range of fit residual values. Appendix C: Sensitivity maps
Average detection probability maps (contours from red, 100%,to white, 0%) computed for the population of binaries described in Sec. 7. Detected spectroscopic companions (white stars) andvisual binaries (black crosses) in the physical separation versusmass ratio. The solid, dashed and dash-dotted lines encompassareas with detection probabilities ≥ M a ss -r a ti o Fig. C.1.
Average detection probabilities for ABD association. M a ss -r a ti o Fig. C.2.
Average detection probabilities for ARG association. M a ss -r a ti o Fig. C.3.
Average detection probabilities for COL association. . Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) , Online Material p 7 M a ss -r a ti o Fig. C.4.
Average detection probabilities for ECH association. M a ss -r a ti o Fig. C.5.
Average detection probabilities for OCT association. M a ss -r a ti o Fig. C.6.
Average detection probabilities for TWA association.
Appendix D: SB1 systems identified in this work v sin i, this work + literature (km s ) R V , t h i s w o r k + li t e r a t u r e + G D R ( k m s ) v sin i, this work (km s ) R V , t h i s w o r k ( k m s ) power law envelopev sin i - 6 km/s binned RV this work Fig. D.1.
Upper panel : The standard deviation in RV as a func-tion of v sin i for measurements calculated in this work. The 3 σ value from binning in 6 km s − bins are represented by the solidlines. The power law envelope is represented by dash-dotted line.The SB1s identified in this work are plotted as a red dots and thepreviously identified SB1s from literature are represented as ablue crosses. Bottom panel : Same as upper panel but includingvalues from literature and Gaia DR2. Some SB1 were confirmedonly when literature values were included (red dots under the 3 σ envelope in upper panel). Details on each candidate can be foundin Appendix A. . Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) , Online Material p 8
Appendix E: Gaia DR2
Example of the sanity checks performed regarding the correctidentification of the Gaia DR2 counterparts to the SACY mem-bers.
Parallax previous SACY collection P a r a ll a x G D R
50 100 150 200 250 300 350
PM module previous SACY collection P M m o d u l e G D R Fig. E.1.
Possible mismatched results was visually inspected andcrosschecked to avoid false positives. The dotted-dashed linerepresent the 1:1 relation.
Appendix F: Rotational periods from light curves
In Fig. F.1 we show an example of the TESS light curve foldedto the period estimated in this work for GSC 07396-00759. Thelower panel shows the residuals obtained after subtraction of thebinned / smoothed phased light curve to be used to asses thereliability of the period. We can see that despite possible flares inthe data-set, our procedure o ff ers a simple but robust diagnostic.On the other hand, as it is evident from Fig. F.2, the apertureused to derive the TESS light curve is contaminated by similarbrightness objects and therefore, we cannot assure that the re-ported value is the rotational period of this particular source. F l u x GSC07396-00759
Data MedianPercentile 10 (lower) - 90 (upper)0.0 0.2 0.4 0.6 0.8 1.0Phase (period 11.64 days)50050100150200 F l u x GSC07396-00759
Fig. F.1.
Upper panel:
Phased light curve for GSC 07396-00759.The solid line represent the median calculated by binning thephased curve in 100 bins. The MAD for the phased curve for thisobject is 652 . Bottom panel:
Residuals from subtracting lightcurve values from the “median model” (solid line). The MAD ofthe residuals is 121 . Pixel Column Number P i x e l R o w N u m b e r E N
Coordinates GSC07396-00759 - Sector 13 m = -2.0 m = 0.0 m = 2.0 m = 5.0 m = 8.0 12345 6789 1011 121314 15 16171819 20 2122 23242526 272829 30 3132 333435 3637 3839 404142 4344 4546 47 484950 5152535455 565758 596061 6263646566 6768 6970 7172 737475 7677 787980 81828384 8586 87 8889 90919293 9495 9697 98 99100101102103 104105 106107 108109 110111 112113 114115 116117 118119 120121122123 124125126 127 128129 130131132 133134 135136137 138 139140141142 143144 145146147 148149 150 151 152153 154155 156157 158159 160161 162163164165166167 168 169170 171172 173174 175176 177178 179180 181182 183184 185 186187188189 190 191192 193 194195196 197 198199200 0.040.060.080.100.120.140.160.180.20 F l u x × ( e ) Fig. F.2.
Output figure for GSC 07396-00759 from the package tpfplotter (Aller et al. 2020). We count the number of Gaiasources within a ∆ G mag ≤ ∆ Gmag valueto assess the quality of the rotational period. . Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) , Online Material p 9
Appendix G: Individual and summary tables
Table G.1.
Table of all individual radial velocity values calculated in this work and compiled from literature / Gaia DR2 (first 10rows). The full table (2048 RV values) is published online in the machine-readable format. The high order features (BIS, b b , c b ) areavailable for all our CCF calculations. The reference code in Ref. column correspond to: ZF20: this work or updated value of Elliottet al. (2014), SC12: Schlieder et al. (2012), SH12: Shkolnik et al. (2012), TO06: Torres et al. (2006), LO06: Lopez-Santiago et al.(2006), RO13: Rodriguez et al. (2013), MA10: Maldonado et al. (2010), MO13: Mo´or et al. (2013), RE09: Reiners & Basri (2009),GO06: Gontcharov (2006), MA14: Malo et al. (2014), KR14: Kraus et al. (2014), MO01b: Montes et al. (2001), MO02: Mochnackiet al. (2002), BA12: Bailey et al. (2012), DE15: Desidera et al. (2015) and GDR2: Gaia DR2, Gaia Collaboration et al. (2018). TheMJD and instrument information is not available for all rows in the table, more details in Sec. 2.
SIMBAD ID RA J2000 (deg) DEC J2000 (deg) RV RV err MJD BIS b b c b Instrument Ref.BD-202977 144.964005 -21.571400 18.87 0.532750 53906 -0.404 -8.353 -0.150 FEROS ZF20BD-202977 144.964005 -21.571400 17.73 0.532750 54240.1 -0.103 -2.283 -0.138 UVES ZF20BD-202977 144.964005 -21.571400 17.75 0.532750 54240.1 -0.089 -1.893 -0.133 UVES ZF20HD99827 171.324005 -84.954399 20.01 1.390170 54906.3 -0.430 -73.848 -0.676 UVES ZF20HD99827 171.324005 -84.954399 19.94 1.390170 54906.3 -0.747 -60.319 -0.830 UVES ZF20HD99827 171.324005 -84.954399 16.30 1.390170 55371.1 0.894 7.246 -1.184 UVES ZF20HD99827 171.324005 -84.954399 19.42 1.390170 56734.3 1.609 81.204 -0.746 UVES ZF20HD99827 171.324005 -84.954399 19.55 1.390170 56748.1 0.810 9.514 -2.268 UVES ZF20CD-691055 194.606995 -70.480301 13.70 0.894763 54577 -1.860 -90.714 4.322 FEROS ZF20CD-691055 194.606995 -70.480301 12.53 0.894763 55978.4 1.439 13.629 2.944 UVES ZF20
Table G.2.
Table of all individual rotational velocity values calculated in this work and compiled from literature (first 10 rows). Thefull table (1480 v sin i values) is published online in the machine-readable format. The reference code in Ref. column correspond to:ZF20: this work, SC12: Schlieder et al. (2012), TO06: Torres et al. (2006), MA14: Malo et al. (2014), BA12: Bailey et al. (2012)and DE15: Desidera et al. (2015).
SIMBAD ID RA J2000 (deg) DEC J2000 (deg) vsini vsini err Ref.BD-202977 144.964005 -21.571400 13.49 1.5 ZF20BD-202977 144.964005 -21.571400 9.92 1.5 ZF20BD-202977 144.964005 -21.571400 9.92 1.5 ZF20HD99827 171.324005 -84.954399 41.23 3.0 ZF20HD99827 171.324005 -84.954399 40.22 3.0 ZF20HD99827 171.324005 -84.954399 39.21 3.0 ZF20HD99827 171.324005 -84.954399 41.23 3.0 ZF20HD99827 171.324005 -84.954399 41.23 6.0 ZF20CD-691055 194.606995 -70.480301 15.20 6.0 ZF20CD-691055 194.606995 -70.480301 28.10 6.0 ZF20
Table G.3.
Component radial velocity values for SB2 systems estimated in this work.
SIMBAD ID RA J2000 (deg) DEC J2000 (deg) RV1 RV1 err RV2 RV2 err MJDGSC08077-01788 72.970802 -46.791901 -21.2927 1.618303 70.72530 0.694135 56735.1GSC08077-01788 72.970802 -46.791901 -15.4776 1.312729 65.67440 1.338559 56738.1HD199058 313.588013 9.040000 -30.0904 1.000865 -11.77740 1.547928 56828.4HD199058 313.588013 9.040000 -24.9204 0.972239 -13.04740 1.352694 56836.3HD199058 313.588013 9.040000 -24.5381 0.860092 -15.96410 1.037438 57275.1HD199058 313.588013 9.040000 -25.0000 0.904851 -13.90000 1.964319 54783.0HD36329 82.350403 -34.515598 23.8599 0.979925 23.85990 0.904718 57271.4HD36329 82.350403 -34.515598 -44.8610 1.290879 90.64900 1.382289 57276.4HD36329 82.350403 -34.515598 -19.5175 1.143967 68.21940 1.918715 57295.3HD51062 103.447998 -43.114201 14.6000 0.912295 38.90000 0.997951 55522.3HD99827 171.324005 -84.954399 1.7000 1.269730 33.50000 1.642376 54169.2UCAC3116-474938 299.011993 -32.121899 -29.8203 1.363111 15.90560 1.102911 57255.3UCAC3116-474938 299.011993 -32.121899 -66.4405 1.185148 54.73050 1.044546 57272.1UCAC3116-474938 299.011993 -32.121899 -40.6756 1.003758 28.52240 1.520679 57275.1UCAC3116-474938 299.011993 -32.121899 -14.4882 1.280286 2.47079 0.857250 57292.2 . Z´u˜niga-Fern´andez et al.: Search for associations containing young stars (SACY) , Online Material p 10
Table G.4.
Summary table of the sample presented in this work. This table is available only in electronic format.
Label Units DescriptionSimbad ID Simbad identifierRA J2000 degrees Right ascension at J2000DEC J2000 degrees Declination at J2000RV median
CCF km s − Median RV from our CCF calculation σ RV CCF km s − Standard deviation in RV from our CCF calculationvsini median
CCF km s − Median v sin i from our CCF calculation σ v sin i CCF km s − Standard deviation in v sin i from our CCF calculationN obs CCF Number of observation from our CCF calculationRV median km s − Median RV from our work + literature σ RV km s − Standard deviation in RV from our work + literatureN obs RV Number of RV observations from our work + literaturevsini median km s − Median v sin i from our work + literature σ v sin i km s − Standard deviation in v sin i from our work + literatureN obs vsini Number of vsini observations from our work + literaturePeriod days Period from light curves σ Period days Period uncertaintyFAP False alarm probabilityPhased-MAD MAD on phased light curveResidual-MAD MAD on residuals of phased light curveP-MAD / R-MAD Ratio between phased-MAD and residuals-MADINSTR. Instrument that has measured the light curveTESS sector TESS sectorTESS / K2 ID TESS or K2 identifierN sources
TESS number of sources in TESS aperture with ∆ Gmag < ∆ Gmag
TESS mag Minimum ∆ Gmag in TESS apertureLC notes Light curves notes on the objectLC q flag