Searching for short-period variable stars in the direction of Coma Berenices and Upgren 1 open clusters: Melotte 111 AV 1224 a new eclipsing binary star
aa r X i v : . [ a s t r o - ph . S R ] J u l Searching for short-period variable stars in the direction of Coma Berenices and Upgren 1open clusters: Melotte 111 AV 1224 a new eclipsing binary star
L. Fox Machado a, ∗ , R. Michel a , M. Alvarez a , J.H. Pe˜na b a Observatorio Astron´omico Nacional, Instituto de Astronom´ıa – Universidad Nacional Aut´onoma de M´exico, Ap. P. 877, Ensenada, BC 22860, M´exico b Instituto de Astronom´ıa – Universidad Nacional Aut´onoma de M´exico, Ap. P. 70-264, M´exico, D.F. 04510, M´exico
Abstract
We report the results of CCD photometric observations in the direction of the Coma Berenices and Upgren 1 open clusters with theaim at searching for new short-period variable stars. A total of 35 stars were checked for variability. As a result of this search thestar designated in the SIMBAD database as Melotte 111 AV 1224 was found to be a new eclipsing binary star. Follow-up Str¨omgrenphotometric and spectroscopic observations allowed us to derive the spectral type, distance, reddening and e ff ective temperatureof the star. A preliminary analysis of the binary light curve was performed and the parameters of the orbital system were derived.From the derived physical parameters we conclude that Melotte 111 AV 1224 is most likely a W-UMa eclipsing binary that is not amember of the Coma Berenices open cluster. On other hand, we did not find evidence of brightness variations in the stars NSV 5612and NSV 5615 previously catalogued as variable stars in Coma Berenices open cluster. Keywords: techniques: photometric, spectroscopic –open clusters: individual:Melotte 111, Upgren 1, stars:variability – stars:individual: Melotte 111 AV 1224,NSV 5613,NSV 5615. .
PACS:
1. Introduction
The study of short period variable stars in open clusters isfundamental in stellar evolution. Since all the cluster membersare assumed to have the same interstellar reddening, distance,age and chemical abundance, it is possible to put strong con-straints on these physical parameters of the cluster variablesin asteroseismic model calculations [e.g. Fox Machado et al.(2001, 2006)].Besides the great success of multichannel photoelectric pho-tometers to study short period variables in open clusters [e.g.Costa et al. 2007; Fox Machado et al. (2002, 2007); Li et al.(2002, 2004)], CCD technique working in the time-series pho-tometry mode has been preferred for open clusters observa-tions (e.g. Kang et al. 2007; Kopacki et al. 2008; Luo et al.2009; Choo et al. 2003). Indeed a CCD camera allows to obtainhigh precision photometric data by measuring the program starand reference stars simultaneously in the CCD’s field of view(FOV hereafter) under the same weather and instrumental con-ditions. The number of stars observed simultaneously with aCCD camera may vary from a couple, in case of a small FOVand sparse fields (e.g Baran et al. 2011a), up to thousands formosaic CCDs pointing near the plane of the Milky Way.Taking the advantage of CCD cameras we have carriedout a search for new short period variable stars in the di-rection of the Coma Berenices and Upgren 1 open clus-ters. Coma Berenices (Melotte 111 hereafter, RA = h m , ∗ Corresponding author. Tel.: +
52 6461744580; fax +
52 6461744607
Email address: [email protected] (L. Fox Machado)
DEC = + o ′ , J2000.0 ) is the second closest open clus-ter to the Sun being more distant than the Hyades ( ∼ ∼
180 pc). The
Hippar-cos intermediate astrometry data place it at d = . ± . / H] = − . ± .
021 dex, Cayrel de Strobel 1990, [Fe / H] = . ± .
047 dex,Friel & Boesgaard 1992). The age of the cluster is estimated atbetween 400 and 600 Myr (e.g. Bounatiro & Arimoto 1993).Several investigations which have addressed the stellar popu-lation in Melotte 111 support the fact that the cluster has rel-atively few members and, particularly that it is poor in low-mass stars. (e.g., Artyukhina et al. 1955; Argue & Kenworthy1969; De Luca & Weis 1981; Bounatiro & Arimoto 1993).Several searches for new low-mass cluster members havebeen recently performed but without more success than earlystudies (e.g. Casewell et al. 2006; Mermilliod et al. 2008;Melnikov & Eisl¨o ff el 2012; Terrien, et al. 2014). In particu-lar Terrien, et al. (2014) have addressed the membership of thestars in direction of Coma Berenices using SDSS III APOGEEradial velocity measurements, confirming just eight K / M dwarfnew candidate members of the cluster. Given that Melotte 111is relatively sparse and the verification of membership in thecluster has been challenging, the detection of new variable starsthat are members of the cluster is very important. Meolotte 111covers about 100 deg on the sky, but its central part occupiesonly about 25 deg . The core of the cluster is estimated be-tween 5-6 pc (Odenkirchen et al., 1998). The catalogue of vari-able stars in open cluster by Zejda et al. (2012) lists 57 variablestars belonging to the Melotte 111 open cluster. Preprint submitted to New Astronomy March 9, 2018 pgren 1 (RA = h m , DEC = + o ′ , J2000.0) is an as-sociation of seven F-type stars located at a distance of ∼
117 pcand considered to be a remnant of an old galactic open cluster(Upgren & Rubin 1965, Upgren et al. 1982).Gatewood, et al. (1988) studied these stars with a multichan-nel astrometric photometer and proposed that the cluster iscomposed of two dynamically di ff erent groups. We have ob-served four stars in this association.The paper is organized as follows. In Sect. 2, the acqui-sition of the data and the description of the observations arepresented. In Sect. 3, the analysis of di ff erential light curvesand the fields observed are discussed. Sect. 4 is devoted tothe analysis of the light curve and the physical parameters ofMelotte 111 AV 1224. In Sect. 5 we summarize our conclu-sions.
2. Observations and data reduction
The CCD observations have been made with the 0.84-m f / × × µ m . The gain and readout noise of the CCD cam-era are 1.8 e − / ADU and 7.0 e − , respectively. The typical fieldof view in this configuration is about 8 ′ × ′ arcmin with thescale of 0. 28 ′′ / pixel. To search for short-period variable starsin direction of Melotte 111 we observed three fields centeredat the following coordinates α J2000 . = h m s . δ J2000 . =+ ◦ ′ . ′′ ; α J2000 . = h m s . δ J2000 . = + ◦ ′ . ′′ and α J2000 . = h m s . δ J2000 . = + ◦ ′ . ′′ . The im-ages of these FOVs are shown in Figures 1, 2, 4 respectively.The field in direction of Upgren 1 was centered at the coordi-nates α J2000 . = h m s . δ J2000 . = + ◦ ′ . ′′ (Fig. 3).In each figure the target stars are labeled with numbers andtheir corresponding identifications are given in the caption ofthe figure. The log of observations is shown in Table 1 wherethe dates, FOV, HJD start, HJD end, filters, exposure timesand number of frames are listed. We note that the star des-ignation Melotte 111 AV refers to the star running number ofthe astrometric catalogue for the area of Coma Berenices byAbad & Vicente (1999).Sky flats, dark and bias exposures were taken each night. AllCCD images were preprocessed to correct overscan, trim un-reliable and useless regions, subtract bias frames, correct flatfielding and reject cosmic rays using the IRAF / CCDRED pack-age. Then, instrumental magnitudes of the stars were com-puted using the point spread function fitting method of theIRAF / DAOPHOT package (Massey & Davis, 1992). The pho-tometry is gathered in tables where frame No., HJD, airmass,UT, photometric instrumental magnitudes and photometric er-rors are included. Typical internal errors of the single framephotometry for stars are of about 0.001 mag in the bands used.The di ff erential light curves were derived on a star-to-star basiscomputing the di ff erence in magnitude of one star with respect Figure 1: CCD FOV 1. The following targets were observed: 1-NSV 5613(BD +
27 2129) , 2-NSV 5615 (BD +
27 2130), 3-USNO B1 1167-0214141, 4-Melotte 111 AV 1616, 5-Melotte 111 124, 6-Melotte 111 AV 1625. North is upand East is left.Figure 2: CCD FOV 2. The following targets are identified: 1-IC 3194(Galaxy), 2-Melotte 111 AV 1176, 3-USNO B1 1151-0193085, 4-USNOB1 1150-0195002, 5-Melotte 111 AV 1192, 6-Melotte 111 AV 1196,7-USNO B1 1151-0193137, 8-USNO-B1 1151-0193141, 9-SSDSJ122138.25 + + + + + + + + + to the others. In that way each star was checked for variabilityrelative to at least two reference stars.
3. Analysis of di ff erential light curves We proceeded to search for short-period variable stars ineach observed field using the di ff erential CCD time-series pho-tometry obtained in the previous section. Our calculations fora V =
15 mag star indicated that with 8 hours of data we canachieve a detection threshold around 1 mmag (millimagnitude)level. Assuming a 4 σ definition for the threshold, the noiselevel should be 0.25 mmag. This detection threshold is verytypical for most ground-based observations.2 igure 5: Top: Light curve and amplitude spectrum of NSV 5613. Bottom: Light curve and amplitude spectrum of NSV 5615.Figure 3: CCD FOV 3. The following targets were observed: 1-BD +
25 2296,2-GSC 02530 02027, 3-HD 109509, 4-HD 109542,, 5-HD 109530. North is upand East is left.
The search for stellar pulsations was done in two steps. First,all di ff erential light curves were visually inspected for the pres-ence of obvious variability. In this way we searched the lightcurves for features like eclipsing binaries, planetary transits,flares and high amplitude pulsations. Second, all light curveswere subject to Fourier analysis. This latter step is very con-venient in analysis of periodicities. It may uncover a periodicchange with either a very tiny amplitude not easily seen directlyin the light curves or a short period like those present in pulsat- Figure 4: CCD FOV 4. The following targets are listed: 1-Melotte 111 AV 1224, 2-Melotte AV 1236, 3-Melotte 111 AV 1248, 4-SDSSJ122202.82 + ing white dwarfs or sdB type variables. We calculated Fouriertransform up to the Nyquist frequency.Some comments on the observed field can be made. TheFOV 1 (Fig. 1) includes six stars. Two stars, NSV 5613(BD +
27 2129) and NSV 5615 (BD +
27 2130), have been classi-fied in the literature as variable stars of Melotte 111. NSV 5613was reported as suspected variable of Melotte 111 by Golay(1973) while NSV 5615 has been classified as a RR Lyrae typevariable star by Archer (1959). Since then no new observations3f these targets has been reported to the best of our knowledge.These stars are also listed in the International Variable Star In-dex (VSX) database of the American Association of VariableStar Observers (AAVSO). Moreover both stars are included inthe catalogue of variable stars in open clusters by Zejda et al.(2012), but no period information is given for them. We haveobserved both targets and the adjacent field stars through aStr¨omgren y filter with 30 sec of exposure times which cor-respond to a Nyquist frequency of 1980 c / d (see Table 1 fordetails). The light curves and amplitude spectra of these twostars are shown in Fig. 5. As can be seen there is no evidenceof periodic variations either in the light curves or in the ampli-tude spectra. We conclude that these stars have been wronglyclassified as variables, as they do not pulsate at all.The FOV 2 (Fig. 2) is the most crowded field we haveobserved. The light curves of the 19 targets numberedin the figure has been derived. The following starsare listed as members of Melotte 111 in the SIMBADdatabase: Melotte 111 AV 1176, Melotte 111 AV 1192,Melotte 111 AV 1196, Melotte 111 AV 1204 andMelotte 111 AV 1207. This FOV was observed througha Johnson V filter with an exposure time between 60 sec cor-responding to a Nyquist frequency of 635 c / d. After carefullyanalyzing the light curves and amplitude spectra of all thestars in this FOV we conclude that none of the stars presentsignificant variations attributed to intrinsic pulsations.As was mentioned before the FOV 3 (Fig. 3) was set in di-rection of Upgren 1. We have observed four stars of this as-sociation namely HD 109509, HD 109530, HD 109542 andBD +
37 2295 through a y -Str¨omgren filter with a exposure timeof 20 sec resulting in a Nyquist frequency of 2274 c / d. Afterchecking carefully the light curves and the amplitude spectrawe conclude that none of the stars is variable.Five stars in FOV 4 (Fig. 4) were checked for variability.Three stars are presumable members of Melotte 111, namelyMelotte 111 AV 1224, Melotte AV 1236, Melotte 111 AV 1248.We found evident brightness changes on a time scale of fewhours in Melotte 111 AV 1224. The adjacent stars in the fieldwere found not to be variable stars. An in depth analysis of thelight curve is given in the next section.
4. Melotte 111 AV 1224
Due to variable nature of Melotte 111 AV 1224, we decidedto monitor this star during all remaining nights. A total numberof 818 frames were obtained through a V Johnson filter. Theexposure time was set to 120 sec.The light curve of Melotte 111 AV 1224 in the time space isshown in Fig. 6. As can be seen the light curve is not sinusoidal,but is strictly periodic. The period of the light curve was derivedby using the Period04 program (Lenz & Breger, 2005). Thefrequency spectrum reveals two peaks, f ∼ . − and 2 f ∼ . − . The derived period is P = . ± . http: // / vsx / Figure 6: Timed light curve of Melotte 111 AV 1224. The continuous line is asynthetic light curve generated with the main and harmonic frequencies.
The following ephemeris was derived from the computed pe-riod of the binary system:
HJD max I = . + . × E (1)where the reference epoch was chosen to be the initial HJD timeof the light curve.Apart from calculating the light elements using the pe-riod derived with the Period04 program, we have also ex-plored other means by which to determine the period ofMelotte 111 AV 1224. To do so, we determined individualtime of maximum from the photometry data via the method ofKwee & van Woerden (1956). A total of 6 timings were ob-tained (4 primary eclipses and 2 secondary eclipses) which arelisted in Table 2. These were then used to establish a periodand a reference epoch by solving for a linear ephemeris usingstandard least-squares techniques. Primary and secondary max-ima were adjusted simultaneously and the orbit was assumedto be circular. The resulting period and epoch are given by P = . T = . In order to shed more light on the physical natureof Melotte 111 AV 1224 Str¨omgren photometry and low-resolution spectroscopy was performed.4 able 1: Log of observations.
UT Date 2009 Fields Start Time End Time Filter Exp. time No. of(HJD 2454900 + ) (HJD 2454900 + ) (sec) ImagesApril 12 FOV 1 (Fig. 1) 33.660060 33.956975 y
30 1069April 13 FOV 2 (Fig. 2) 34.649227 34.974052 V
60 350April 16 FOV 3 (Fig. 3) 37.705917 37.989076 y
20 1195April 17 FOV 4 (Fig. 4) 38.631485 38.973245 V
120 230April 18 FOV 4 (Fig. 4) 39.683163 39.683163 V
120 205April 20 FOV 4 (Fig. 4) 41.661120 41.953617 V
120 176April 21 FOV 4 (Fig. 4) 42.669725 42.669725 V
120 207
Table 2: Times of maxima for Melotte 111 AV 1224.
HJD Type E O-C2454938 . ± . . ± . . ± . . ± . . ± . . ± . Kepler targets (Uytterhoeven et al.,2011). A set of standard stars was also observed to transforminstrumental observations into the standard system and to cor-rect for atmospheric extinction. The instrumental magnitudes( inst ) and colours, once corrected from atmospheric extinction,were transformed to the standard system ( std ) through the wellknown transformation relations given by Str¨omgren (1966) : V std = A + y inst + B ( b − y ) inst ( b − y ) std = C + D ( b − y ) inst m , std = E + Fm , inst + G ( b − y ) inst c , std = H + Ic , inst + J ( b − y ) inst H β, std = K + LH β, inst where V is the magnitude in the Johnson system, and the m and the c indices are defined in the standard way: m ≡ ( u − v ) − ( v − b ) and c ≡ ( v − b ) − ( b − y ).The following indices in the Str¨omgren system forMelotte 111 AV 1224 were derived: V = . ± . b − y ) = . ± m = . ± . c = . ± . H β = . ± . Figure 7: Stellar spectrum of Melottte 111 AV 1224 and HD 185144 a K0Vstar. & Chivens spectrograph installed in the Cassegrain focus ofthe telescope. The 400 lines / mm grating with a blaze angleof 4.18 ◦ was used. The grating angle was set to 7 ◦ to coverwavelength range from 4000 Å to 7500 Å. A 2048 × .3. Physical parameters from Str¨omgren photometry andspectroscopy We have used the standard uvby − β indices to estimate theunreddened colours of Melotte AV 1224. The UVBYBETA IDL code was implemented to derive the following intrinsiccolours: E ( b − y ) = . b − y ) = . m = . c = . M V = .
35 which lead to T e ff = ±
300 K and R = . ± . R ⊙ . A similar value of T e ff is obtained us-ing the calibrations of Ram´ırez & Mel´endez (2005) for FGKstars. The intrinsic colours are consistent with an early K-type star in agreement with our spectroscopic classification. Asa reference, the atmospheric parameters of the standard starHD 185144 are the followings: T e ff = g = . / s (Takeda, et al., 2005)The distance moduli of Melotte 111 AV 1224 amounts to8.045 mag which leads to a distance of 392 pc implying thatMelotte 111 AV 1224 is rather located behind the Molotte 111open cluster. Using the light elements derived in Sect. 4.1, we have con-structed the phased light curve of Melotte 111 AV 1224 shownin Fig. 8. In an e ff ort to gain a better understanding of thebinary system and determine its physical properties, we haveanalyzed the phased light curve with the software PHOEBEV.0.31a (PHysics Of Eclipsing BinariEs, Prˇsa & Zwitter 2005).PHOEBE is a software package for modeling eclipsing binarystars based on the Wilson-Devinney code (Wilson & Devinney,1971). It permits creation of a synthetic light curve that wouldbest fit the observational data by adjusting interactively the or-bital and stellar parameters through a user interface friendly.We averaged the phases and magnitudes every three points anduse this binned light curve as input in the PHOEBE code.In the light curve analysis we assume a few fixed parametersduring the fitting process: the temperature of the primary star,based on the Str¨omgren photometry (Sect. 4.3) is set to T = HJD wereobtained from equation (1). The logarithmic limb-darkeningcoe ffi cients and bolometric limb-darkening coe ffi cients, weredetermined from tables by van Hamme (1993) for the primaryand secondary components, respectively. Standard values ofbolometric albedos (Ruci´nski, 1969), and the gravity-darkeningcoe ffi cients (Lucy, 1967) for radiative and convective envelopeswere used. The adjustable parameters in the light curves fittingwere the orbital inclination i , the surface potentials Ω and Ω ,the e ff ective temperature of the secondary T , the mass ratio q and luminosity of the primary component.The shape of the light curve of Melotte 111 AV 1224 resem-bles those of both systems classical Beta Lyrae (EB) and W-UMa, with a di ff erence in amplitude of the primary and sec-ondary eclipses and with no clear beginning and end of theeclipses. The di ff erence in eclipse amplitudes strongly suggestssignificant deformation of the components and perhaps some Written by T.T. Moon at University London in 1985 and based on calibra-tions of Moon & Dworetsky 1985 degree of contact. Consequently, we performed fits in overcon-tact mode (Mode-3), in semidetached mode with the primaryfilling its Roche lobe (Mode-6) and and in semidetached modewith the secondary component filling its Roche lobe (Mode-7). As the primary and secondary eclipses occur at almost 0.5phase interval suggesting a circular orbit, we have set the ec-centricity e = .
0. During the fitting process the iterations werecarried out automatically until convergence, and a solution wasdefined as the set of parameters for which the di ff erential cor-rections were smaller than the probable errors and the small-est χ was obtained. With all configurations two spots on thesecondary component have been considered during the fittingprocess to account for a slight asymmetry in the light curve.Our analysis reveals that astrophysically reasonable solutionsare obtained with either configuration overcontact or semide-tached with the secondary filling its Roche lobe, even thoughthe smallest χ is achieved in overcontact configuration. Fig-ure 9 depicts our best-fit theoretical light curve (solid line) fittedto the observational data (circles) in overcontact configurationmode. The full list of fitted, absolute and spots parameters isgiven in Table 3. For comparison in Table 4 the fitted parame-ters in semidetached configuration are listed. The uncertaintiesassigned to the adjusted parameters are the internal errors pro-vided directly by the code.Briefly, our results show that the Melotte 111 AV 1224 sys-tem appears to have a mass ratio of q ≈ .
21, and low incli-nation angle of i ≈ ◦ , and a secondary star temperature of T ≈ ff erence of ∼ ff erent eclipse depths observed in the light curves.
5. Results and conclusions
A summary of a search for new short-period pulsating vari-ables in direction of the open clusters Melotte 111 and Up-gren 1 has been presented. 35 stars were checked for variabil-ity in four observed fields. We did not confirm the variabilityin the stars NSV 5612 and NSV 5615 considered as variablestars of the Melotte 111 open cluster. On the contrary, the starMelotte 111 AV 1224 was found to be a new eclipsing binarystar. Follow-up CCD observations of Melotte 111 AV 1224 al-lowed us to estimate the orbital period and ephemeris of thesystem. Based on Str¨omgren standard photometry and low-resolution spectra we conclude that the primary componentis most likely an early K-type dwarf. The analysis of theStr¨omgren standard photometry place it to 392 pc much morefarther that Melotte 111 open cluster ( ∼
87 pc). Therefore,Melotte 111 AV 1224 is not dynamically associated with theMelotte 111 open cluster. This is consistent with the fact al-ready pointed out in early investigations that the Melotte 111open cluster has relatively few members and particularly that itis poor in low-mass stars. Although a classical Beta Lyrae (EB)binarity classification cannot be ruled out, our analysis of thelight curve of Melotte 111 AV 1224 revealed properties sim-ilar in many respects to those of the W UMa systems, whichare characterized by having short orbital periods (0.2 - 0.8 d)6 able 3: Solution parameters for Melotte 111 AV 1224 in overcontact configuration.
Parameters SystemPrimary component Secondary Component
HJD [days] 38.631482Orbital period – P [days] 0.345894Semi-major axis a [ R ⊙ ] 3 . ± . q = m / m . ± . i [ ◦ ] 45 ± e ff ective temperature [K] T = . ± Ω = . ± . Ω = . ± . A = . A = . g = . g = . ffi cient x = . x = . ffi cient y = . y = . Ω ( L ) = . Ω ( L ) = . M ⊙ ] M = . M = . R ⊙ ] R = . R = . M bol1 = . M bol2 = . g Log ( g ) = . Log ( g ) = . L ⊙ ] 1.622 1.659Spot parametersColatitude Longitude Radius Temperature factor[ ◦ ] [ ◦ ] [ ◦ ] T spot / T surf Spot 1 18 300 44 0.7Spot 2 15 180 50 0.7and are composed of F-K type stars sharing a common enve-lope. However the evolutionary history of the system is notclear due to the missing of radial velocity data. We have foundthat both models, overcontact and semidetached, systems fit theobserved light curves equally well. We think that the systemis undergoing cyclic variations with alternating phases of truecontact and semidetached, but almost contact, phases. Duringthe contact phases the characteristic W-Uma light curve shouldbe observed, while during semidetached phases the surface tem-perature of the components should be di ff erent, thus producingBeta Lyrae (EB) type light curve. Therefore we are probablyseeing the semidetached phases of the system.To date our observations represent the most extensive workon Melotte 111 AV 1224. Overall we believe that our resultsare the best that we can achieved based solely on photometricobservations made in the V filter. For a better understanding ofthe properties, both spectroscopic observations and photometricdata at multiple wavelengths are needed. Acknowledgments
This work has received financial support from the UNAM viagrant IN114309. Based on observations collected at the 0.84m telescope at the Observatorio Astron´omico Nacional at SanPedro M´artir, Baja California, Mexico. Special thanks are given to the technical sta ff and night assistants of the San Pedro M´artirobservatory. We thank J. Miller for a careful proofreading ofthis manuscript. This research has made use of the SIMBADdatabase operated at the CDS, Strasbourg (France). References
Abad, C., & Vicente, B. 1999, A&AS, 136, 307Archer, S., 1959, JBAA, 69, No.4, 157Argue, A.N., & Kenworthy, C.M., 1969, MNRAS, 146, 479Artyukhina, N.M. 1955, Trudy gos. astr. Inst. Sternberga 26, 3Baran, A.S. et al. 2011a, Acta Astronomica, 61, 37Baran, A.S. et al. 2011b, Acta Astronomica, 61, 325Bounatiro, L., & Arimoto, N. 1993, A&A, 268, 829Casewell, S.L., et al., 2006, MNRAS, 365, 447Cayrel de Strobel, G. 1990, MmSAI, 61, 613Choo, K. J., et al. 2003, A&A 399, 99Costa,J.E.S. et al. 2007, A&A, 468, 637De Luca, E.E., & Weis, E. W., 1981, PASP, 93, 32Friel, E.D., & Boesgaard, A.M. 1992, ApJ, 387, 107Fox Machado, L., et al. 2001, In: Proc. of SOHO 10 / GONG 2000 Workshop:Helio-and asteroseismology at the dawn of the millenium, eds. A. Wilson,P. Pall´e, ESA SP-464, p. 427Fox Machado, L., et al. 2006, A&A, 446, 611Fox Machado, L., et al. 2002, A&A, 382, 556Fox Machado, L., et al. 2007, AJ, 134, 860Fox Machado, L., et al. 2010, New Astronomy, 15, 397Gatewood, G. et al. 1988, ApJ, 332, 917 able 4: Solution parameters for Melotte 111 AV 1224 in semidetached configuration. Parameters SystemPrimary component Secondary Component
HJD [days] 38.631482Orbital period – P [days] 0.345894Semi-major axis a [ R ⊙ ] 2 . ± . q = m / m . ± . i [ ◦ ] 40 ± e ff ective temperature [K] T = . ± Ω = . ± . Ω = . ± . A = . A = . g = . g = . ffi cient x = . x = . ffi cient y = . y = . Ω ( L ) = . Ω ( L ) = . M ⊙ ] M = . M = . R ⊙ ] R = . R = . M bol1 = . M bol2 = . g Log ( g ) = . Log ( g ) = . L ⊙ ] 1.622 1.659Spot parametersColatitude Longitude Radius Temperature factor[ ◦ ] [ ◦ ] [ ◦ ] T spot / T surf Spot 1 6 100 20 0.7Spot 2 4 110 35 2.0
Golay, M. 1973, ApJ, in: Proc. of IAU Symp. 54 Problems of Calibration ofAbsolute Magnitudes and Temperature of Stars, eds. B. Hauk, E. Bengt, p.275Kang, Y.B., et al. 2007, PASP, 119, 239Kwee, K.K., & van Woerden, H. 1956, BAN, 12, 237Kopacki, G. et al. 2008, Acta Astronomica 58, 373Lenz, P., & Breger, M. 2005, CoAst, 146, 53Li, Z. P., et al. 2002, A&A, 395, 873Li, Z. P., et al. 2004, A&A, 420, 283Lucy, L. B., 1967, Z. Astrophys., 65, 89Luo, Y. P., et al. 2009, New Astronomy 14, 584Massey, P, & Davis, L.E. 1982, A User’s Guide to Stellar CCD Photometrywith IRAFMermilliod, J.-C., et al. 2008, A&A, 491, 951Melnikov, S., & Eisl¨o ff el, J., 2012, A&A, 544, A111Moon, T.T., & Dworetsky, M.M. 1985, MNRAS, 217, 305Nicolet, B. 1981, A&A, 104, 185Odenkirchen, M., et al. 1998, New Astronomy, 3, 583Pe˜na, J.H., et al. 2007, RevMexAA, 43, 329Pe˜na, J.H., et al. 2011, RevMexAA, 47, 309Prˇsa, A., & Zwitter, T. 2005, ApJ, 628, 426Ram´ırez, I, & Mel´endez, J., 2005, ApJ, 626, 465Ruci´nski, S.M. 1969, Acta Astronomica, 19, 245Str¨omgren, B. 1996, ARA&A, 4, 433Takeda, Y., et al. 2005, PASJ, 57, 27Terrien, R.C., et al. 2014, ApJ, 782, 61Upgren, A.R., & Rubin, V.C, 1965, PASP, 94, 229Upgren, A.R., et al. 1982, PASP, 77, 355Uytterhoeven, K., et al., 2011, A&A, 534, 125van Hamme, W. 1993, AJ, 106, 2096 van Leeuwen, F. 2009, A&A, 497, 209Wilson, R.E., & Devinney, E.J. 1971, ApJ, 166, 605Zejda, M., et al, 2012, A&A, 548, A97 igure 8: Phased light curve of Melotte 111 AV 1224.Figure 9: The binned observational light curve in V band (circles) and the besttheoretical fit model (solid line) of Melotte 111 AV 1224.band (circles) and the besttheoretical fit model (solid line) of Melotte 111 AV 1224.