SCExAO/CHARIS High-Contrast Imaging of Spirals and Darkening Features in the HD 34700 A Protoplanetary Disk
Taichi Uyama, Thayne Currie, Valentin Christiaens, Jaehan Bae, Takayuki Muto, Sanemichi Z. Takahashi, Ryo Tazaki, Marie Ygouf, Jeremy N. Kasdin, Tyler Groff, Timothy D. Brandt, Jeffrey Chilcote, Masahiko Hayashi, Michael W. McElwain, Olivier Guyon, Julien Lozi, Nemanja Jovanovic, Frantz Martinache, Tomoyuki Kudo, Motohide Tamura, Eiji Akiyama, Charles A. Beichman, Carol A. Grady, Gillian R. Knapp, Jungmi Kwon, Michael Sitko, Michihiro Takami, Kevin R. Wagner, John P. Wisniewski, Yi Yang
DDraft version July 24, 2020
Typeset using L A TEX twocolumn style in AASTeX63
SCExAO/CHARIS High-Contrast Imaging of Spirals and Darkening Features in the HD 34700 AProtoplanetary Disk
Taichi Uyama,
1, 2, 3
Thayne Currie,
4, 5, 6
Valentin Christiaens, Jaehan Bae,
8, 9
Takayuki Muto, Sanemichi Z. Takahashi, Ryo Tazaki, Marie Ygouf, Jeremy N. Kasdin, Tyler Groff, Timothy D. Brandt, Jeffrey Chilcote, Masahiko Hayashi, Michael W. McElwain, Olivier Guyon,
5, 16, 17
Julien Lozi, Nemanja Jovanovic, Frantz Martinache, Tomoyuki Kudo, Motohide Tamura,
20, 21, 3
Eiji Akiyama, Charles A. Beichman,
2, 1
Carol A. Grady,
15, 6, 23
Gillian R. Knapp, Jungmi Kwon, Michael Sitko, Michihiro Takami, Kevin R. Wagner,
16, 27
John P. Wisniewski, and Yi Yang
20, 3 Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA NASA Exoplanet Science Institute, Pasadena, CA 91125, USA National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan NASA-Ames Research Center, Moffett Blvd., Moffett Field, CA 94035, USA Subaru Telescope, National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 650 North A‘oh ¯ o k ¯ u Place, Hilo,HI 96720, USA Eureka Scientific, 2452 Delmer, Suite 100, Oakland, CA 96002, USA School of Physics and Astronomy, Monash University, 10 College Walk, Clayton Melbourne 3800, Vic, Australia Earth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Road NW, Washington, DC 20015, USA NHFP Sagan Fellow Division of Liberal Arts, Kogakuin University 2665-1, Nakano-cho, Hachioji-chi, Tokyo, 192-0015, Japan Department of Mechanical Engineering, Princeton University, Princeton, NJ 08544, USA NASA-Goddard Space Flight Center, Greenbelt, MD 20771, USA Department of Physics, University of California-Santa Barbara, Santa Barbara, CA 93106, USA Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN, 46556, USA Exoplanets and Stellar Astrophysics Laboratory, Code 667, Goddard Space Flight Center, Greenbelt, MD 20771, USA Steward Observatory, University of Arizona, Tucson, AZ 85721, USA Astrobiology Center, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo, Japan Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA Universit ´ e C ˆ o te d’Azur, Observatoire de la C ˆ o te d’Azur, CNRS, Laboratoire Lagrange, France Department of Astronomy, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan Astrobiology Center of NINS, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan Department of Engineering, Niigata Institute of Technology, 1719 Fujihashi, Kashiwazaki, Niigata 945-1195, Japan Goddard Center for Astrobiology, 8800 Greenbelt Road, Greenbelt, MD 20771, USA Department of Astrophysical Science, Princeton University, Peyton Hall, Ivy Lane, Princeton, NJ 08544, USA Space Science Institute, 4765 Walnut St, Suite B, Boulder, CO 80301, USA Institute of Astronomy and Astrophysics, Academia Sinica, National Taiwan University, No.1, Sec. 4, Roosevelt Rd, Taipei 10617,Taiwan, R.O.C. NASA NExSS Earths in Other Solar SystemsTeam, USA Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks Street, Norman, OK 73019, US
ABSTRACTWe present Subaru/SCExAO+CHARIS broadband (
JHK -band) integral field spectroscopy of HD34700 A. CHARIS data recover HD 34700 A’s disk ring and confirm multiple spirals discovered inMonnier et al. (2019). We set limits on substellar companions of ∼ M Jup at 0 . (cid:48)(cid:48) ∼ M Jup at 0 . (cid:48)(cid:48)
75 (outside the ring). The data reveal darkening effects on the ring and spiral,although we do not identify the origin of each feature such as shadows or physical features related tothe outer spirals. Geometric albedoes converted from the surface brightness suggests a higher scaleheight and/or prominently abundant sub-micron dust at position angle between ∼ ◦ and 90 ◦ . Spiralfitting resulted in very large pitch angles ( ∼ − ◦ ) and a stellar flyby of HD 34700 B or infall froma possible envelope is perhaps a reasonable scenario to explain the large pitch angles. a r X i v : . [ a s t r o - ph . E P ] J u l Uyama et al.
Keywords:
Coronagraphic imaging, Protoplanetary disks INTRODUCTIONProtoplanetary disks around young ( (cid:46)
10 Myr) starsare key laboratories for exploring planet formation. Re-cent high angular resolution observations of these disksin scattered light through thermal emission in the sub-millimeter reveal a variety of asymmetric features – e.g.gaps, rings, and spirals – that may be traced to planetformation processes (e.g. Avenhaus et al. 2018; Andrewset al. 2018). Theoretical studies have predicted part ofsuch asymmetric features are related to planet formation(e.g. Zhu et al. 2011; Dodson-Robinson & Salyk 2011)and recently VLT and MagAO high-contrast imagingobservations reported the first convincing protoplanetswithin a gap of the PDS 70’s protoplanetary disk (Kep-pler et al. 2018; Wagner et al. 2018; Haffert et al. 2019).High-contrast imaging opened a new window of investi-gating planet formation mechanism but the occurrencerate of detected young planets is much smaller ( ∼ (cid:38)
10 Myr; Torres 2004). Thissystem has two other companions (HD 34700 BC) lo-cated at ∼ . (cid:48)(cid:48) ∼ . (cid:48)(cid:48) Gaia ( 356 . +6 . − . pc) showed a larger distance than theprevious assumption, which made one infer a youngerage. Monnier et al. (2019) implemented radiative trans-fer modeling along with Gemini/GPI JH -band observa-tions and proved that HD 34700 A is a young system ( ∼ J band, it had differences somewhat betweenGPI-based JH -band total intensity and H -band polar-ized intensity. Another intriguing feature in the HD34700 A disk is its spiral features: previous high angularresolution observations have reported a variety of mor-phology in disks at various evolutionary stages (e.g. ABAur, SAO 206462, MWC 758, HD100453, HD 100546,HD 142527, Elias 2-27, CQ Tau, GG Tau; Hashimotoet al. 2011; Muto et al. 2012; Grady et al. 2013; Wagneret al. 2015; Currie et al. 2015; Avenhaus et al. 2014;P´erez et al. 2016; Uyama et al. 2020; Keppler et al.2020). Among these disks this object has the largest number of spirals in a disk, the mechanism of which isstill unclear.In this study we present integral field spectroscopy re-sults of HD 34700 A taken with the Coronagraphic HighAngular Resolution Imaging Spectrograph (CHARIS)and the Subaru Coronagraphic Extreme Adaptive Op-tics (SCExAO). Our observation and several differential-imaging reductions detected the ring and multiple spi-rals. We also newly detected darkening features on thering and one of the spirals. Section 2 describes our ob-servation, data reduction, and results. We then imple-mented radiative transfer modeling from J to K bandand investigated scattering profiles. Our spiral fittingshows very large pitch angles ( ∼ ◦ − ◦ ) and we dis-cuss possible scenarios that can induce multiple spiralswith such large pitch angles. Details of each topic are in-vestigated in Section 3. Finally we summarize our workin Section 4. DATA2.1.
Observations
We used Subaru/SCExAO+CHARIS in broadbandintegral field spectroscopy (IFS) mode (1.16-2.37 µ m,spectral resolution of R ∼
19, pixel scale = 0 . (cid:48)(cid:48) − ). In this paper we collapse the reduced IFSdata cube into JHK -band images to discuss simultane-ous multi-band imaging results. HD 34700 A ( J =8.04, H =7.71, K =7.48; Cutri et al. 2003) was observed on2019 January 12 UT with a Lyot coronagraph mask tosuppress the starlight and a fixed pupil so that angu-lar differential imaging (ADI; Marois et al. 2006) couldbe applied after. HR 2466 ( J =5.03, H =5.07, K =5.11;Cutri et al. 2003) was also observed for a PSF referenceof reference-star differential imaging (RDI; Lafreni`ereet al. 2009). Details about the data reduction are ex-plained in Section 2.2. Astrogrids made from the star’sPSF were added in the field of view (FoV) with 25nmamplitude modulation in the deformable mirror (Jo-vanovic et al. 2015; Sahoo et al. 2020), which providesaccurate measurements of the central star’s location andphotometry. The data were taken under very good see-ing conditions ( θ V ∼ . (cid:48)(cid:48)
4) and a typical FWHM was ∼ JHK bands, respectively. The to-tal exposure time was 2168.6 seconds (1.475-sec singleexposure ×
21 coadds ×
70 cubes) for HD 34700 A and2952.95 seconds (1.475-sec single exposure ×
14 coadds ×
143 cubes) for HR 2466. The HD 34700 A observationobtained ∼ ◦ of parallactic angle change for ADI. a r c s e c a r c s e c Figure 1.
Comparison of a single exposure for HD 34700A (left) and HR 2466 (right) at channel 11 ( λ =1.6296 µ m).Color scale is arbitrary and these images are not rotatedto North up. Astrogrids are located by the four edges ineach FoV. Dashed black circle in each image indicates thecoronagraph mask (113 mas in radius). Data Reduction and Results
We used CHARIS data reduction pipeline with the χ extraction algorithm (Brandt et al. 2017) to extractdark-subtracted, flat-fielded, and wavelength-calibrateddata cubes with 22 uniform spectral channels from theCHARIS raw files for both HD 34700 A and HR 2466.For spectrophotometric calibration we used appropri-ate Kuruz model atmospheres (Castelli & Kurucz 2003)adopting G0V and A2V for spectral types of HD 34700A and HR 2466 respectively. Single extracted data cubesshow the ring feature of HD 34700 A without any post-processing (Figure 1).For post-processing PSF subtraction we implementedtwo reduction techniques: (1) RDI by following the wayof Currie et al. (2019) to capture the ring morphologywithout self-subtraction (2) combination of ADI andspectral differential imaging (SDI; Vigan et al. 2015) byfollowing the way of Currie et al. (2018) to get high con-trast enough to investigate outer spirals and potentialplanetary-mass companions. In both data reductions weused the same data reduction pipelines as Currie et al.(2018, 2019). Our methods are described in more detailbelow. 2.2.1. RDI
First, we performed RDI by utilizing Karhunen-Lo` e veImage Projection algorithms (KLIP; Soummer et al.2012), where we adopted a “full-frame subtraction” onthe CHARIS FoV ( r min = 3 pix for the inner workingangle, r max = 65 pix (1 . (cid:48)(cid:48)
05) for the outer working angle,and ∆ r = 62 pix for the subtraction separation).Figure 2 compares collapsed JHK -band (1.154–2.387 µ m) images of RDI-reduced (Karhunen-Lo` e ve - thenumber of basis vector; KL=5) HD 34700 A data andFigure 3 shows polar-projected images of Figure 2. Herewe excluded channels (channel No. 6-8: 1.3746-1.4714 µ m, No. 15-17: 1.8672-1.9987 µ m) that have strongertelluric absorption and lie either in the wings or outside of the nominal JHK bandpasses. We were able to re-solve scattered light from the ring surface, but did notconfirm an inner arc in the gap Monnier et al. (2019)reported. Regions interior to ∼ J , H , and K bands are dominated by residual specklenoise in our RDI reduction. Thus, we focus on charac-terizing disk features at wider separations (Section 3).Details about the ring feature are discussed in Section3. The ring extends along the whole azimuthal directionand shows some asymmetric features such as darkening,which makes it difficult to calculate a radial noise profileto define error bars of the surface brightness. Therefore,we calculate standard deviations at the interior (0 . (cid:48)(cid:48) . (cid:48)(cid:48)
7) of the ring in each collapsed imageand defined noise at the ring separation as interpolationof the standard deviations between the two separations.Here we adopted 3 σ clipping to mitigate effects of thepresence of the ring at ∼ . (cid:48)(cid:48) ∼ . (cid:48)(cid:48) ADI+SDI
After the basic reductions as mentioned at the begin-ning of Section 2.2 we performed ADI reduction utiliz-ing Locally Optimized Combination of Images (LOCI;Lafreni`ere et al. 2007) and Adaptive-LOCI (A-LOCI;Currie et al. 2012) algorithms. A smaller separation ofsubtraction zones (∆ r = 5 pix) than the RDI reduction,a singular value decomposition (SVD) cutoff to truncatethe diagonal terms of the covariance matrix of SV D lim =10 − (see also Currie et al. 2013, 2018), a rotation gap of δ = 0 .
75 to limit signal loss/biasing due to azimuthallydisplaced copies of the astrophysical signal, and a pixelmask over the subtraction zone (e.g. Currie et al. 2012)were adopted to generate weighed reference PSFs at dif-ferent separations. To further suppress residual specklesand achieve higher contrast we then performed SDI re-duction on the ADI residuals.Figures 4 and 5 show J , H , and K -band images re-duced using ADI+SDI instead of RDI (see Figures 2 and3). We were able to detect several spiral features thatare not detected by the RDI reduction (signal-to-noiseratios (SNRs) ≥ . De-tails of the spiral fitting are described in Section 3.1.3.2.3. Constraints on Potential Companions The noise is defined as standard deviation at separations be-tween 0 . (cid:48)(cid:48) − FWHM / . (cid:48)(cid:48)
75 + FWHM / Uyama et al. D e c [ a r c s e c ] J band S u r f a c e B r i g h t n e ss [ m J y a r c s e c ] D e c [ a r c s e c ] H band S u r f a c e B r i g h t n e ss [ m J y a r c s e c ] D e c [ a r c s e c ]
100 au K band S u r f a c e B r i g h t n e ss [ m J y a r c s e c ] Figure 2.
RDI-KLIP (KL=5) reduction results at J (left), H (center), and K (right) bands. The central unresolved binary(HD 34700 Aab) is masked by the reduction algorithm. North is up and East is left. -90 0 90 180 2700.30.50.7 J band -90 0 90 180 2700.30.50.7 H band -90 0 90 180 270Position Angle [deg]0.30.50.7 S e p a r a t i o n [ a r c s e c ] K band Figure 3.
Polar-projected (East of North) images of Figure2 at the ring area. Color scale is set the same as Figure 2.
Our data did not reveal any substellar-mass com-panion candidates. We determined contrast limits bycalculating radial noise profiles at each spectral chan-nel, as in prior studies (Currie et al. 2011), including asmall sample statistics correction (Mawet et al. 2014).We took account of throughput correction by estimat-ing flux loss of injected fake point sources made by theADI+SDI reduction. We note that noise in this sectionis different from the noise of surface brightness used inSections 2.2.1 and 2.2.2 because we aim at constrain-ing point sources and thus used convolved images withaperture radii=FWHM/2. Figure 6 shows 5 σ contrastlimits of our ADI+SDI reduction results and compari-son with mass unit at each band assuming a hot-startmodel (COND03; Baraffe et al. 2003) and 5 Myr. Thebroadband contrast achieved 10 − ( ∼ M Jup ) at 0 . (cid:48)(cid:48) − ( ∼ M Jup ) at 0 . (cid:48)(cid:48)
75. The detection limitsare strongly affected by the bright ring and spirals at separations (cid:38) . (cid:48)(cid:48)
4, which bias an estimate of the noise. K -band contrast limits are poorer than JH -band lim-its because of the thermal background at channels oflonger wavelength. With a cold-start model (Spiegel &Burrows 2012) a 10 M Jup object corresponds to ∼ − contrast at each band and we do not compare our de-tection limits with the cold-start model.To test a hypothesis of an eccentric ( e = 0 .
2) 50 M Jup companion embedded in the disk (Monnier et al. 2019),we injected a fake source in the CHARIS data set andreran the ADI+SDI reduction. For a spectrum we madea planet model among
JHK bands by assuming H -bandcontrast of 10 − . , which corresponds to 0.05 M (cid:12) and ∼ . (cid:48)(cid:48)
35 North and 0 . (cid:48)(cid:48) ANALYSIS AND DISCUSSION3.1.
Disk Morphology
Figure 8 compares our new ADI+SDI and RDI im-ages of HD 34700 A to the GPI-polarimetric differentialimaging (PDI) result shown in Monnier et al. (2019). Inthis subsection we describe the ring, darkening features,and spirals in detail. D e c [ a r c s e c ] J band D e c [ a r c s e c ] H band D e c [ a r c s e c ]
100 au K band Figure 4.
Same comparison of the reduced images as Figure 2 with ADI+SDI-ALOCI reduction. Color scale is arbitrary. Apositive signal at a similar location to where Monnier et al. (2019) predicted a substellar-mass companion, which is likely apart of disk distorted or an artifact by the ADI+SDI reduction, is indicated by yellow arrow in each image (see Section 2.3 fordetails). -90 0 90 180 2700.30.50.70.9 J band -90 0 90 180 2700.30.50.70.9 H band -90 0 90 180 270Position Angle [deg]0.30.50.70.9 S e p a r a t i o n [ a r c s e c ] K band Figure 5.
Same as Figure 3 for Figure 4 at the ring+spiralarea.
Ring
We estimate that the RDI process alters the signalless than ∼
15% (see Section 3.2), and thus we use theRDI images for our analysis. We fit the bright edge ofthe cavity to an ellipse using the python ellipse fittingtool described in Hammel & Sullivan-Molina (2020). Weprovided as input to the python routine the pixel coor-dinates of the local radial maxima in the surface bright-ness profiles in 1 ◦ -wide azimuthal sections (cyan pointsin Figure 9a). We performed the fit separately on the C o n t r a s t J H K J band H band K bandBroadband Figure 6. σ contrast limits of our ADI+SDI result. Dashedlines correspond to that at each slice and J , H , K , andBroadband ( JHK ) correspond to those of collapsed imagesat each wavelength, respectively. We also plot mass as afunction of contrast at three wavelengths assuming COND03and 5 Myr. J -, H - and K -band RDI images (Figure 3) and foundconsistent results. The uncertainties on each parame-ter of the ellipse were obtained in each band using thestandard deviation of the Gaussian fit to the distribu-tion of fitting results for 10000 bootstraps. Our finalresults are an average of the best fits obtained in eachband, with the uncertainties for each band combined inquadrature. We found a semi-major axis of 487.1 mas ± ± ± . ◦ ± . ◦ .Assuming that the actual shape of the cavity is cir-cular, our best-fit ellipse suggests a disk inclination of40 . ◦ ± . ◦ and PA of semi-major axis of 74 . ◦ ± . ◦ .Regarding the uncertainty of PA we include the fit-ting uncertainty and CHARIS uncertainty on true north Uyama et al. D e c [ a r c s e c ] J band D e c [ a r c s e c ] H band D e c [ a r c s e c ] K band Figure 7.
As Figure 4 with an injected fake source (indicated by dashed yellow circles) to test the hypothesis of a 50- M Jup companion. We changed the color scale from Figure 4 to clearly show the injected source.
Figure 8.
Comparison of the collapsed RDI and ADI+SDI images to the GPI-PDI image Monnier et al. (2019), reproduced bypermission of J. Monnier. The arrows indicate darkening features (see Section 3.1.2). The central star is indicated by a whitestar in the masked region.
Figure 9. a)
Fit of the ring to an ellipse (blue curve) overlaid on the
JHK band-collapsed RDI image. Cyan crosses show localradial maxima used for the fit. b) Fit of the spiral arms seen in the collapsed ADI+SDI image to the equation of a generalArchimedean spiral. c) Deprojected ADI+SDI disk image (assuming a thin-disk), where the spirals are fit to the equation of alogarithmic spiral, in order to estimate their pitch angle. In all images the central star is indicated by a white star. (0 . ◦ ; see Appendix A of Currie et al. 2018). Our es-timates of the cavity parameters and the disk inclina-tion are all consistent to those inferred in Monnier et al.(2019) using a similar method applied to the PDI image,apart from the value of the PA of the semi-major axis ofthe disk (for which they found 69 . ◦ ± . ◦ ). The slightdiscrepancy might be due to the difference of the scat-tering phase function between polarized intensity andtotal intensity. However, such difference can stem fromthe requirement for the shift of the center of the ellipsewith respect to the star to lie along the semi-minor axisin their procedure. Considering the uncertainties on thecentering of the star and the assumption of a circularshape cavity, we did not force this condition in our pro-cedure.We note that the assumption of a circular cavity is notnecessarily correct, given that several disks with largecavities show a non-null eccentricity, such as HD 142527and MWC 758 (Avenhaus et al. 2014; Dong et al. 2018b).New ALMA data probing the kinematics of the diskwould provide an independent estimate of the inclina-tion of the disk. The difference of inclination, if any, es-timated from the scattered light and ALMA will suggestdifferent distribution of gas/small grains/large grainsand therefore we can answer whether the assumptionof circular cavity is reasonable.3.1.2. Darkening Effects
The RDI images show evidence for multiple darkeningareas on the bright edge of the cavity and these areas,except for the Northwest one, coincide with the GPI-PDI image, which are indicated by arrows in Figure 8.We also indicate these regions by gray shades in plotsof surface brightness and geometric albedo of the ring(see Figure 11 and Section 3.3 for details). We firstnote that the darkening features on the ring, except theNorthwest one, are located by the roots of S1, possiblyS3, S4, and S6 (see also Figure 9). Shadows, actual geo-metric features, or other scattering characteristics due toheterogeneous dust distribution may give explanationsof the darkening features. We individually investigatethe possibility of the shadowing effect for each darken-ing feature but do not rule out other possibilities. Wealso note that reproducing all the darkening features byonly the shadowing effect likely requires multiple innerdisks, which may be dynamically unstable. It is hardto identify which mechanism is the most favorable forreproducing each feature in this study.Prominent roughly symmetric shadowing effects canbe seen to the North and South, at PA spanning ∼ − ◦ to 30 ◦ and ∼ ◦ to 200 ◦ , and to the Northwest andSoutheast, at PA spanning ∼ ◦ to 120 ◦ and ∼ ◦ to 325 ◦ (-70 ◦ to -35 ◦ ), respectively. There might be otherpossible darkening areas that are marginally seen in ourreduced images and the surface brightness profile (e.g.PA ∼ ◦ in J band), but they are less convincing thanthose mentioned above and we do not conclude such pos-sible features as shadows or spiral roots in this study.The effect of the North-South symmetric shadows is seenin all bands, albeit stronger at a shorter wavelength.The other pair is only seen in J and H band suggest-ing optically-thin at longer wavelength (Figures 3 and11) or different scattering characteristics (in this casethe darkening feature corresponds to a non-shadowingeffect). These darkening features can also be seen in ourADI+SDI image, although less conspicuously given thepresence of radial post-processing artifacts (left panel ofFigure 8). Furthermore, our ADI+SDI image suggestsshadowing of a part of the main NW spiral, which ap-pears to lie in the continuity of the Northern part of thesymmetric N-S shadow.A comparison of our images to the PDI image shown inMonnier et al. (2019) confirms the presence of all darken-ing areas, except one in the Northwest direction, in theirimage too (right panel of Figure 8) - albeit not reportedas such. The symmetric shadows are reminiscent of po-larimetric imaging or space-based coronagraphic imag-ing of the disks such as HD 142527 (Avenhaus et al.2014; Marino et al. 2015), HD 100453 (Benisty et al.2017), HD 163296 (Wisniewski et al. 2008; Rich et al.2019), SAO 206462 (Stolker et al. 2017), and DoAr 44(Casassus et al. 2018), and suggest the presence of aninclined inner disk. These shadow features may also bereproduced by a combination of single shadows. Thesingle shadow is reminiscent of the ones observed in thecircumbinary disk of GG Tau A, which includes a closecentral binary similar to HD 34700 A (Itoh et al. 2002,2014), and in the transition disk of HD 169142 (Quanzet al. 2013; Bertrang et al. 2018). For GG Tau, sev-eral explanations for the single shadow have been pro-posed, including a dense clump in an accretion streamonto one component of the central binary, or a circum-planetary disk surrounding a protoplanet located in thecavity (Krist et al. 2002; Canovas et al. 2017) as well ascircumstellar disks around GG Tau Aa/b (Brauer et al.2019; Keppler et al. 2020).Finally we note that our observation did not detectany further inner object(s) down to ∼ . (cid:48)(cid:48)
2. ALMA con-tinuum observation may help to investigate possible in-ner disk(s). Follow-up high-contrast observations arealso useful to investigate time variation of the shadowsand to constrain inner objects as previous observationsreported (possible) changes of shadow features (in a timescale of years; Wisniewski et al. 2008; Debes et al. 2017;
Uyama et al.
Stolker et al. 2017; Uyama et al. 2018; Rich et al. 2019;Laws et al. 2020). Assuming that an inner object ata radius of 0 . (cid:48)(cid:48) J -band result)) casts ashadow on the ring (0.5) and that we can identify thetime variation of the shadow if the shadow shifts by 30mas (= J -band angular resolution in our observation),the inner object should move 12 mas (4.4 au). A pe-riod of Keplerian rotation at 73 au around HD 34700A is about 313 years and the 4.4-au movement takes 3years. A color discussion at the darkening areas withthe high-contrast imaging may also help to investigatewhether possible inner object(s) are optically-think orthin. If the darkening areas are accompanied with ac-tual geometric features the scattered light there mightinclude multiple scattering, a ratio of which depends ondust properties (e.g. Takami et al. 2013), and then de-tailed discussions with radiative transfer simulations arerequired for a synthetic understanding of the HD 34700A’s disk. 3.1.3. Spiral Characterization
To increase SNRs of the faint spirals we used amedian-combined ADI+SDI image using all CHARISspectral channels. Although the ADI+SDI reductioncan cause self-subtraction of the spiral features, our datareduction adopts reasonable settings to avoid biasing theactual morphology (see Section 2.2.2 for the settings).The rotation gap ( δ = 0 .
75) limits the self-subtractionof the astrophysical signal caused by rotating the field.With a local pixel masking over the subtraction zone,the astrophysical signal contained within the subtrac-tion zone does not bias the LOCI coefficients and self-subtraction is reduced (for details see Currie et al. 2018).We followed the same procedure as in Reggiani et al.(2018) and Price et al. (2018) to identify the trace ofspiral arms as local maxima in the radial intensity pro-file of the disk, and fit them to the equation of using theequations of general Archimedian and logarithmic spiralarms, respectively. The fits to the equation of generalArchimedean spirals systematically yield the best mor-phological match, while the fit to logarithmic spirals isused for pitch angle estimation. In polar coordinates,a general Archimedean spiral is given by the equation r = a + bθ n , and a logarithmic spiral by r = r e kθ ,where the pitch angle ( φ = arctan( k )) is constant anddetermines the spiral. With this procedure, we fit thesix brightest spirals outside the ring, including two arcslikely tracing the same spiral but truncated due to shad-owing from the inner disk (referred to as S1a and S1b).All the identified spirals have SNRs (cid:38) ∼ − . Table 1.
Pitch angle of the spiralsSpiral φ φ deproj , thin φ deproj , h=0 . (deg) (deg) (deg)S1a 31 . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . image. The first column in Table 1 reports the pitchangle measured for each spiral arm labeled in Figure 9.Given that the disk is inclined, if the spirals are lo-cated in the same plane as the inner edge of the outerdisk (i.e. the bright ring), one has to measure spiral pitchangles in the deprojected image of the disk for a mean-ingful comparison to the values predicted by differentspiral formation mechanisms. We deprojected the im-age with respect to the center of the disk, i.e. consid-ering the 52.7 mas shift with respect to the location ofthe star, and considering the values of inclination andPA of semi-major axis inferred in Section 3.1.1: 40.9 ◦ and 74.5 ◦ , respectively. The pitch angles measured inthe deprojected image are provided in the middle col-umn of Table 1. This way of deprojection ignores thevertical characteristics of the spiral feature. For compar-ison we made another deprojected image with diskmap(Stolker et al. 2016) by taking into account a large con-stant opening angle ( h ( r ) = 0 . r , where h is the heightof the scattering surface) and then conducted the spiralfitting, the results of which are also given at the last col-umn in Table 1. The difference is significant along thesemi-minor axis (S1a, S2, S3, and S6). We note that ourspiral fitting may also be affected by the inclination ofHD 34700 A’s disk. Dong et al. (2016) suggested thatscattered light of the spiral feature can be distorted byits inclination and image deprojection by ∼ ◦ may nottrace the real spiral feature.The pitch angle values in Table 1 are significantly dis-crepant with the rough estimates of 20–30 ◦ reported inMonnier et al. (2019). Since they do not mention howthe pitch angles were measured nor whether a deprojec-tion was performed for their measurement, it is difficultto discuss the reason for this discrepancy. From the de-projected pitch angles of Table 1 in a thin-disk case, wenotice a significant difference between S1 ( φ deproj ∼ ◦ )and the other spirals ( φ deproj ∼ ◦ ), possibly point-ing to different origins. In a thick-disk case the pitchangle of S1b is significantly different to other spirals.As S1b is located at a larger separation from the ringand it might have different characteristics than the otherspirals. We note that ADI+SDI reduction could causedistortion of the real shapes because of self-subtractionand follow-up observations with ALMA or high-contrastPDI/RDI reductions with a comparable angular resolu-tion and sensitivity will help to confirm our result of thespiral fitting. 3.2. Forward Modeling
To investigate the disk’s scattering profile, we useforward-modeling to reproduce the observed ring with asynthetic scattered light disk and simultaneously matchmost of the system’s spectral energy distribution. Herewe do not include probable shadowing effects due toinner disk(s). We followed Currie et al. (2019) withMCMax3D radiative transfer code (Min et al. 2009) tomodel the ring and compared the forward-modeled diskwith the CHARIS-RDI result. We adopted the best-fitparameters in Monnier et al. (2019) as initial parametersand then explored a small range of the model componentparameters to reproduce the scattered light image.Table 2 summarizes the best-fit model of the ring andFigure 10 compares the forward-modeled disks at
JHK bands. The disk component surface density follows Σ(
R < R w ) ∝ R − (cid:15) × exp(-( − R/R exp w ) ) and Σ ( R ≥ R w ) ∝ R − (cid:15) . The scale height in our model is consistent withthe best-fit scale height without VSG/PAH in Monnieret al. (2019). Other best-fit parameters do not havelarge differences from the Monnier et al. (2019) best-fit parameters but our best-fit model provides a bet-ter match to the surface brightness (see Section 3.3 fordetails). We estimated attenuation factors by compar-ing the modeled disks before and after the KLIP-RDIreduction, which are used for throughput correction ofthe RDI reduction ( ∼ Scattering Profiles
Figure 11 compares azimuthal profiles of surfacebrightness and geometric albedo (see Equation (3) ofMulders et al. 2013) by tracing the peaks of the ring.Note that this geometric albedo depends on dust albedoand geometry of the disk. Solid lines with errors corre-spond to the traced ring peaks from the collapsed
JHK -band images after the throughput correction. Error barsare extrapolated from the background noise at 0 . (cid:48)(cid:48) J band at ∼ -90 ◦ to 0 ◦ , large parts of which are affected by the darkening effects(see also Section 3.1.2), and better reproduces the totalintensity of the resolved ring without weighting differ-ent passbands. Monnier et al. (2019) needed to multi-ply the H -band model by 2 to match the GPI result.We note that the model adopts a simple ellipse to ap-proximately reproduce the ring geometry but the actualring has more complex features such as the darkeningfeatures, the discontinuity at PA ∼ ◦ , and the spirals.Compared with the GPI total intensity (Monnier et al.2019) our azimuthal profiles are different in both J and H bands. This difference is mainly due to the differenceof data reduction: Monnier et al. (2019) made an ap-proximate reference PSF by assuming a Moffat functionand subtracted it from the total intensity (star+disk)image to extract the disk total intensity, while we usedthe practical star (HR 2466) for a reference PSF andconducted the RDI reduction. As HD 34700 A is a bi-nary the light source onto the disk surface is variable,which can also vary the scattering profile.We used photometric results of 2MASS (Cutri et al.2003) and deprojected separations (assuming the diskinclination of 40.9 ◦ - see Table 2) of the traced ringto convert surface brightness into the geometric albedo.The difference of the geometric albedo profiles betweenthe resolved disk and the modeled disk looks larger thanthe case of the surface brightness profile because theconversion includes geometric difference between bothof the disks (see Appendix A). A remarkable feature inthe albedo plot is a color tendency at PA between ∼ ◦ and 90 ◦ . The model-based geometric albedo is compa-rable at JH band, while the actual J -band geometricalbedo has a higher value than that in H -band. SuchReyleigh-scattering-like feature appears at higher scaleheight or where sub-micron dust is prominent and ourresult suggests either or both of these possibilities at thisarea. 3.4. Origin of the Spirals
Spiral S1, particularly S1b, appears to be more tightlywound than the other spirals observed in the disk, withmeasured pitch angles of ∼ ◦ -47 ◦ and ∼ ◦ for theinner (S1a) and outer (S1b) sections (see Section 3.1.3),respectively. In a thin-disk case S1ab can be formed bythe same origin and it is also interesting that S1 is theonly spiral that is directly crossed by a shadow. Shad-owing has been suggested as a possible mechanism toform spiral arms, due to the periodic temperature andhence pressure kick imprinted on material rotating in thedisk (Montesinos et al. 2016; Montesinos & Cuello 2018).The morphology of S1a and S1b is roughly compati-ble with the inner and outer wake of a spiral launched0 Uyama et al.
Table 2.
Disk Model ParametersParameter ValueDisk ParametersDistance ∗ (pc) 365.5 T eff ∗ (for Aa, Ab) (K) 5900 , 5800 L (cid:63) ∗ (for Aa, Ab) ( L (cid:12) ) 13 , 11.5 R (cid:63) ∗ (for Aa, Ab) ( R (cid:12) ) 3.46 , 3.4 M (cid:63) ∗ (for Aa, Ab) ( M (cid:12) ) 2.0 , 2.0Separation between Aab ∗ (au) 0.69 A V ∗ θ ) (deg) 60Disk inclination ( i ) (deg) 40.9Disk Offset from Star - Major Axis (au) -10Disk Offset from Star - Minor Axis (au) 5Inner radius, R in (au) 170Outer radius, R out (au) 400Disk wall radius, R w (au) 200Scale height at inner radius, H o , in p gas (cid:15) ) 0.5Wall shape ( w ) rounded/0.2 M dust ( M (cid:12) ) 2.5 × − Minimum dust size ( a min , µm [small, large]) 0.25, 5Maximum dust size ( a max , µm [small, large]) 5, 1000Dust Size Power Law, p a Note —We fixed stellar parameters (with ∗ symbol) to thoseestimated in Monnier et al. (2019). The dust mass is evenly dividedbetween “small grain” and “large grain” components. The wallshape parameter defines the spatial scale over which the disk surfacedensity increases from R in to R w . See Mulders et al. (2010, 2013)and Thalmann et al. (2014) for detailed explanations of theMCMax3D terminology. D e c [ a r c s e c ] J band S u r f a c e B r i g h t n e ss [ m J y a r c s e c ] D e c [ a r c s e c ] H band S u r f a c e B r i g h t n e ss [ m J y a r c s e c ] D e c [ a r c s e c ] K band S u r f a c e B r i g h t n e ss [ m J y a r c s e c ] Figure 10.
The best-fit forward-modeled disks at J (left), H (center), and K (right) bands. The images are convolved by theinstrumental PSF and then reduced by the RDI reduction. Figure 11.
Azimuthal profiles of surface brightness afterthe throughput correction by tracing the ring peak (top) andgeometric albedo converted from the surface brightness (bot-tom). Those profiles of the modeled disks are overlaid. Grayshaded areas indicate the darkening areas (see Section 3.1.2).Gray vertical dashed and dashed-dotted lines indicate themajor and minor axes of the best-fit disk model respectively.Error bars in the top image correspond to 14.5, 11.3, and8.93 mJy arcsec − at J , H , and K band, respectively. Notethat the model adopted a simple ring without the darkeningeffects, discontinuity, and spirals seen in the actual disk. from a shadow, with a larger (resp. smaller) pitch anglefor the inner (resp. outer) wake. In a thick-disk caseS1ab might be disconnected and formed via differentmechanisms. Future observation may help to investi-gate whether these spirals are physically connected ornot.The radially-extended feature of S1 is also compatiblewith being launched by a companion. In that case, itis unlikely to be caused by a yet undetected companionin the cavity, as outer wakes are expected to be tightlywound ( φ ≤ ◦ ; Bae & Zhu 2018). The large pitch angleof both S1a and S1b would suggest they correspond toan inner spiral wake (with respect to the companion).This could be either a yet undetected protoplanet in theouter disk (e.g. Dong et al. 2015; Zhu et al. 2015), orthe known K-dwarf outer companion HD 34700 B.From their flocculent appearance, spirals S2–S6 ( φ ∼ ◦ ) may resemble those seen in numerical simulations ofgravitationally unstable protoplanetary disks (e.g. Riceet al. 2003). However, Monnier et al. (2019) estimated the Toomre parameter values larger than 25 everywherein the disk based on their radiative transfer model, whichmakes this possibility unlikely.3.4.1. Stellar Flyby
Considering the respective proper motion of HD 34700AB, an interesting possibility is that of a recent flyby.Hydrodynamical simulations show stellar flybys can in-duce spirals with a large pitch angle (e.g. Cuello et al.2019, 2020). In practice arms/spirals in the RW Aur Aand UX Tau A disks can be well reproduced by the stel-lar flyby (Dai et al. 2015; Rodriguez et al. 2018; M´enardet al. 2020). We checked RA, Dec, and proper motionsfor HD 34700 A and B (Gaia Collaboration et al. 2018)and calculated their projected separation over the past.The separation ( r ) between HD 34700 AB is expressedas follows: r = (cid:112) (∆RA − ∆ pm RA × t ) + (∆Dec − ∆ pm Dec × t ) , where ∆RA and ∆Dec are differences of RA and Decin Gaia DR2, ∆ pm RA and ∆ pm Dec are those of propermotions along RA and Dec, and t corresponds to time[year]. We also checked the projected separation withHD 34700 C, which is located at ∼ . (cid:48)(cid:48) ∼
700 au away from HD 34700 A. For thecase of C the separation is greater than 1000 au and Cmay be less responsible for inducing the spirals than B.The larger relative proper motion of C than that of B2
Uyama et al. may be affected by the systematic uncertainty betweenGaia DR2 and Sterzik et al. (2005). We assume thesame distance and do not take into account of line-of-sight motion in these plots because Gaia-based distancesare 356 . +6 . − . pc and 353 +10 − pc for A and B respectivelyand are consistent with each other within errors. Theparallax of C has not been measured and we adoptedthe same assumption about the distance. We note thaterrors of the separation increase as time increases (seeAppendix B) if we include Gaia measurement errors ofthe proper motion, and that the error bars in Figure 12include only measurement errors of RA and Dec. Cuelloet al. (2019) showed that spirals induced by a stellarflyby can survive for more than 7000 years under someconditions and stellar flyby is perhaps a reasonable sce-nario if HD 34700 B passed by HD 34700 A ∼ Infall
An alternative possibility for the origin of the floc-culent spiral pattern is infall from a late envelope ora captured cloudlet (e.g. Tang et al. 2012; Dullemondet al. 2019). A late-envelope infall was proposed toaccount for the similar spiral pattern observed in thedisk of AB Aur (Fukagawa et al. 2004; Tang et al. 2012,2017). Large scale images of the environment of ABAur show the presence of a large surrounding cloudlet,which led Dullemond et al. (2019) to propose that tran-sitional disks like AB Aur could all be the result ofcloudlet capture. In that case, the spirals might beseen in a different plane than that of the inner rim ofthe outer disk, i.e. the outer disk would be warped,as e.g. HD 100546 (e.g. Quillen 2006). This would ex-plain the very large deprojected pitch angle values. Wenote that previous studies and our observation have notyet detected any envelope-like features. Monnier et al.(2019) implemented SED fitting of HD 34700 A and in-dicated Av=0. They also presented the large FoV imageof HST/NICMOS ( ∼ . (cid:48)(cid:48) × . (cid:48)(cid:48)
9) where one half of itsvicinity was explored and there is no significant signalof envelope. The HST/STIS data cover the whole vicin-ity (within a radius of ∼ (cid:48)(cid:48) ) and confirmed faint haloextending outside the CHARIS FoV ( ∼ − (cid:48)(cid:48) in radius;Ygouf et al. 2019, and Ygouf et al. in prep). We at-tempted to fit the traced peaks of the spirals with infallbut could not set robust constraints on spiral parame-ters with the infall scenario because of large uncertain-ties (see Appendix C). CO rotational line observations with ALMA may help to investigate the kinematics ofthe outer disk, including the spirals.Apart from AB Aur, HD 34700 A also shows a sim-ilar spiral pattern to the circumbinary disk HD 142527(e.g. Fukagawa et al. 2006; Christiaens et al. 2014; Aven-haus et al. 2014). Both systems harbor a prominentspiral combined with multiple smaller flocculent spiralarms stemming from the edge of the cavity. The hydro-dynamical simulations in Price et al. (2018) suggest thatthe dynamical interaction between the inner binary andthe outer disk can account for the flocculent spiral armsin HD 142527. The prominent spiral might correspondto a secular large-scale spiral density wave (e.g. Demi-dova & Shevchenko 2015). However the separation be-tween the inner binary of HD 34700 Aa and Ab is signif-icantly smaller than HD 142527 AB (0.69 AU versus 25–50 AU) for a similar size cavity ( ∼
175 AU versus ∼ SUMMARYWe have presented Subaru/SCExAO+CHARISbroadband (
JHK band) integral field spectroscopyof the HD 34700 A protoplanetary disk. The observa-tion was conducted under such a good seeing conditionthat a single frame could resolve the ring without anypost-processing. We then conducted RDI and ADI+SDIreductions to obtain its morphology and to estimate thesurface brightness accurately, which resulted in cleardetection of both the ring and multiple spirals as shownin Monnier et al. (2019). Although Monnier et al. (2019)suggested a 50 M Jup companion embedded in the disk,we did not detect any companion candidates. We calcu-lated contrast limits from the ADI+SDI result and thebroadband contrast curve sets a constraint on potentialsubstellar-mass objects down to ∼ M Jup at 0 . (cid:48)(cid:48) ∼ M Jup at 0 . (cid:48)(cid:48)
75 (outside the ring) as-suming COND03 model and 5 Myr. We also tested the50 M Jup companion scenario by injecting a fake sourceand concluded that our observation could set a robustconstraint on this hypothesis.We used the MCMax3D radiative transfer code to re-produce the ring scattering profile. By checking thereduced images and comparing surface brightness withthe forward-modeled disk we newly confirmed darken-ing effects on the ring and spiral, large parts of whichappear to be shadows cast by possible inner object(s).Except at these darkening features our best-fit modelprovides a better match to the actual surface bright-ness among
JHK bands than Monnier et al. (2019) that3 S e p a r a t i o n [ a r c s e c ]
700 au900 au1100 au1300 au1500 au1700 au1900 auseparation between HD 34700AB S e p a r a t i o n [ a r c s e c ] Figure 12.
Projected separation between HD 34700 AB (left) and AC (right). Error bars include only measurement errors ofRA and Dec (see also Figure 14). showed some discrepancy between their model and sur-face brightness. However, part of these features are lo-cated by the roots of the spirals and we do not ruleout other possibilities such as physical features relatedto the outer spirals. Geometric albedo converted fromthe surface brightness of the ring suggests a higher scaleheight and/or prominently abundant sub-micron dust atposition angles between ∼ ◦ and 90 ◦ .We also conducted spiral fitting of S1-S6 and the re-sult suggests very large pitch angles ( ∼ − ◦ ) thatare larger than the estimated pitch angles presented inMonnier et al. (2019). A stellar flyby of HD 34700 Bor infall from surrounding envelope is perhaps a rea-sonable scenario to explain the large pitch angles. Weinvestigated the separation between HD 34700 AB basedon Gaia-based coordinates and proper motions and HD34700 B could be located ∼
700 au away from HD 34700A about 8000 years ago. Future CO observations withALMA may investigate the kinematics of the outer disk,including the spirals. ACKNOWLEDGMENTSThe authors would like to thank the anonymous ref-erees for their constructive comments and suggestionsto improve the quality of the paper. We thank JohnMonnier for authorization to use GPI-PDI images orig-inally presented in Monnier et al. (2019). The authorsare grateful to Gijs Mulders for the helpful comments.This research is based on data collected at the SubaruTelescope, which is operated by the National Astronom-ical Observatories of Japan. This research has madeuse of NASA’s Astrophysics Data System BibliographicServices. This research has made use of the SIMBADdatabase, operated at CDS, Strasbourg, France. Thisresearch made use of Astropy, a community-developedcore Python package for Astronomy (Astropy Collabo-ration et al. 2013, 2018)TU acknowledges JSPS overseas research fellowship.TC is funded by a NASA Senior Postdoctoral Fel-lowship. JW acknowledges funding support from theNASA XRP program via grants 80NSSC20K0252 andNNX17AF88G. ST is supported by JSPS KAKENHIGrant-in-Aid for Early-Career Scientists No. 19K14764.MT is supported by MEXT/JSPS KAKENHI grantNos. 18H05442, 15H02063, and 22000005. EAis supported by MEXT/JSPS KAKENHI grant No.17K05399. The development of SCExAO was sup-ported by JSPS (Grant-in-Aid for Research
Uyama et al. community. We are most fortunate to have the oppor-tunity to conduct observations from this mountain.APPENDIX A. DIFFERENCE BETWEEN SEPARATIONS OF THE TRACED RINGSFigure 13 shows peak loci of the resolved ring and the modeled ring in each band. The difference of disk geometryaffects the conversion from surface brightness into geometric albedo in Section 3.3. -90 0 90 180 2700.30.40.50.6 J band observed deprojectedobservedmodel deprojectedmodel-90 0 90 180 2700.30.40.50.6 H band -90 0 90 180 270Position Angle [deg]0.40.6 S e p a r a t i o n [ a r c s e c ] K band Figure 13.
Comparison of peak loci between the resolved ring (‘observed’ - solid line) and the modeled ring (‘model’ - dashedline), overlaid with both of deprojected separations (‘deprojected’), at J , H , and K bands, respectively.B. ERRORS OF SEPARATION BETWEEN HD 34700 AB AND ACThe error of separation is estimated according to the law of propagation σ r = (cid:115) ( ∂r∂ ∆RA σ ∆ RA ) + ( ∂r∂ ∆ pm RA σ ∆ pm RA ) + ( ∂r∂ ∆Dec σ ∆ Dec ) + ( ∂r∂ ∆ pm Dec σ ∆ pm Dec ) , where σ ∆ RA and other error parameters above are defined as sum of squares of the Gaia DR2 measurement errors. Inparticular, coefficients of the proper motion errors ( ∂r∂ ∆ pm RA and ∂r∂ ∆ pm Dec ) are expressed as ∂r∂ ∆ pm C = − t (∆C − ∆ pm C × t ) r ,where C is RA or Dec, and have an order of t . Therefore the errors of the separation increase according to t if weinclude the measurement errors of the proper motions (see Figure 14 for the plot with error bars including the propermotion errors). C. FITTING OF SPIRALS BY GAS INFALL MODELInfall motion of the envelope gas is written by the parabolic orbit (cf. Cassen & Moosman 1981), which is given by r (cid:48) = a − cos( θ (cid:48) − b ) , S e p a r a t i o n [ a r c s e c ] separation between HD 34700AB S e p a r a t i o n [ a r c s e c ] separation between HD 34700AC Figure 14.
As Figure 12 with both measurement errors of the coordinates and the proper motions. The solid line correspondsto the separation without errors and the shaded area corresponds to the errors.
Table 3.
Best fit parameters and errors obtained from the fitting of gas infall modelParameters S1a S1b S2 S3 S4 S5 S6Best Fit a [mas] 45.7 706 290 677 1.27 × b [rad] -0.0472 -0.584 -0.195 -0.588 -0.737 -0.0997 -0.727 i [rad] -1.54 -1.01 -1.45 -1.15 -1.26 -1.46 -1.11Ω [rad] -1.43 -2.15 -1.54 -0.782 0.331 1.95 1.70Standard Error a [mas] 2.85 × × × ×
313 8.78 × b [rad] 2.96 0.732 2.17 0.764 0.222 13.9 0.0970 i [rad] 1.78 1.18 1.36 0.624 0.0404 16.2 0.0272Ω [rad] 0.0939 0.998 0.378 0.627 0.103 1.81 0.119 in the coordinate of the orbital plane ( r (cid:48) , θ (cid:48) ), where a and b are parameters characterizing the orbit. The inclination i and the position angle Ω of the orbital plane are also parameters of the orbit. We fit the observed spirals by theparabolic orbit by assuming 1) spirals are located foreground and 2) spirals can extends inward the ring and they maynot be detected in the CHARIS image. We summarize the best fit parameters and the standard errors in Table 3. Theerrors depend on the traced peaks and the ADI+SDI reduction.REFERENCES Andrews, S. M., Huang, J., P´erez, L. M., et al. 2018, ApJL,869, L41, doi: 10.3847/2041-8213/aaf741Astropy Collaboration, Robitaille, T. P., Tollerud, E. J.,et al. 2013, A&A, 558, A33,doi: 10.1051/0004-6361/201322068Astropy Collaboration, Price-Whelan, A. M., Sip˝ocz, B. M.,et al. 2018, AJ, 156, 123, doi: 10.3847/1538-3881/aabc4fAvenhaus, H., Quanz, S. P., Schmid, H. M., et al. 2014,ApJ, 781, 87, doi: 10.1088/0004-637X/781/2/87Avenhaus, H., Quanz, S. P., Garufi, A., et al. 2018, ApJ,863, 44, doi: 10.3847/1538-4357/aab846 Bae, J., & Zhu, Z. 2018, ApJ, 859, 119,doi: 10.3847/1538-4357/aabf93Baraffe, I., Chabrier, G., Barman, T. S., Allard, F., &Hauschildt, P. H. 2003, A&A, 402, 701,doi: 10.1051/0004-6361:20030252Benisty, M., Stolker, T., Pohl, A., et al. 2017, A&A, 597,A42, doi: 10.1051/0004-6361/201629798Bertrang, G. H. M., Avenhaus, H., Casassus, S., et al. 2018,MNRAS, 474, 5105, doi: 10.1093/mnras/stx3052Bonnefoy, M., Chauvin, G., Lagrange, A. M., et al. 2014,A&A, 562, A127, doi: 10.1051/0004-6361/201118270 Uyama et al.
Bowler, B. P. 2016, PASP, 128, 102001,doi: 10.1088/1538-3873/128/968/102001Brandt, T. D., Rizzo, M., Groff, T., et al. 2017, Journal ofAstronomical Telescopes, Instruments, and Systems, 3,048002, doi: 10.1117/1.JATIS.3.4.048002Brauer, R., Pantin, E., Di Folco, E., et al. 2019, A&A, 628,A88, doi: 10.1051/0004-6361/201935966Canovas, H., Hardy, A., Zurlo, A., et al. 2017, A&A, 598,A43, doi: 10.1051/0004-6361/201629145Casassus, S., Avenhaus, H., P´erez, S., et al. 2018, MNRAS,477, 5104, doi: 10.1093/mnras/sty894Cassen, P., & Moosman, A. 1981, Icarus, 48, 353,doi: 10.1016/0019-1035(81)90051-8Castelli, F., & Kurucz, R. L. 2003, in IAU Symposium, Vol.210, Modelling of Stellar Atmospheres, ed. N. Piskunov,W. W. Weiss, & D. F. Gray, A20.https://arxiv.org/abs/astro-ph/0405087Christiaens, V., Casassus, S., Perez, S., van der Plas, G., &M´enard, F. 2014, ApJL, 785, L12,doi: 10.1088/2041-8205/785/1/L12Cuello, N., Dipierro, G., Mentiplay, D., et al. 2019,MNRAS, 483, 4114, doi: 10.1093/mnras/sty3325Cuello, N., Louvet, F., Mentiplay, D., et al. 2020, MNRAS,491, 504, doi: 10.1093/mnras/stz2938Currie, T., Cloutier, R., Brittain, S., et al. 2015, ApJL, 814,L27, doi: 10.1088/2041-8205/814/2/L27Currie, T., Burrows, A., Itoh, Y., et al. 2011, ApJ, 729,128, doi: 10.1088/0004-637X/729/2/128Currie, T., Debes, J., Rodigas, T. J., et al. 2012, ApJL,760, L32, doi: 10.1088/2041-8205/760/2/L32Currie, T., Burrows, A., Madhusudhan, N., et al. 2013,ApJ, 776, 15, doi: 10.1088/0004-637X/776/1/15Currie, T., Brandt, T. D., Uyama, T., et al. 2018, AJ, 156,291, doi: 10.3847/1538-3881/aae9eaCurrie, T., Marois, C., Cieza, L., et al. 2019, ApJL, 877,L3, doi: 10.3847/2041-8213/ab1b42Cutri, R. M., Skrutskie, M. F., van Dyk, S., et al. 2003,VizieR Online Data Catalog, II/246Dai, F., Facchini, S., Clarke, C. J., & Haworth, T. J. 2015,MNRAS, 449, 1996, doi: 10.1093/mnras/stv403Debes, J. H., Poteet, C. A., Jang-Condell, H., et al. 2017,ApJ, 835, 205, doi: 10.3847/1538-4357/835/2/205Demidova, T. V., & Shevchenko, I. I. 2015, ApJ, 805, 38,doi: 10.1088/0004-637X/805/1/38Dodson-Robinson, S. E., & Salyk, C. 2011, ApJ, 738, 131,doi: 10.1088/0004-637X/738/2/131Dong, R., Fung, J., & Chiang, E. 2016, ApJ, 826, 75,doi: 10.3847/0004-637X/826/1/75Dong, R., Najita, J. R., & Brittain, S. 2018a, ApJ, 862,103, doi: 10.3847/1538-4357/aaccfc Dong, R., Zhu, Z., Rafikov, R. R., & Stone, J. M. 2015,ApJL, 809, L5, doi: 10.1088/2041-8205/809/1/L5Dong, R., Liu, S.-y., Eisner, J., et al. 2018b, ApJ, 860, 124,doi: 10.3847/1538-4357/aac6cbDullemond, C. P., K¨uffmeier, M., Goicovic, F., et al. 2019,A&A, 628, A20, doi: 10.1051/0004-6361/201832632Fukagawa, M., Tamura, M., Itoh, Y., et al. 2006, ApJL,636, L153, doi: 10.1086/500128Fukagawa, M., Hayashi, M., Tamura, M., et al. 2004, ApJL,605, L53, doi: 10.1086/420699Gaia Collaboration, Brown, A. G. A., Vallenari, A., et al.2018, A&A, 616, A1, doi: 10.1051/0004-6361/201833051Grady, C. A., Muto, T., Hashimoto, J., et al. 2013, ApJ,762, 48, doi: 10.1088/0004-637X/762/1/48Haffert, S. Y., Bohn, A. J., de Boer, J., et al. 2019, NatureAstronomy, 3, 749, doi: 10.1038/s41550-019-0780-5Hammel, B., & Sullivan-Molina, N. 2020,bdhammel/least-squares-ellipse-fitting: v2.0.0, v2.0.0,Zenodo, doi: 10.5281/zenodo.3723294Hashimoto, J., Tamura, M., Muto, T., et al. 2011, ApJL,729, L17, doi: 10.1088/2041-8205/729/2/L17Itoh, Y., Tamura, M., Hayashi, S. S., et al. 2002, PASJ, 54,963, doi: 10.1093/pasj/54.6.963Itoh, Y., Oasa, Y., Kudo, T., et al. 2014, Research inAstronomy and Astrophysics, 14, 1438,doi: 10.1088/1674-4527/14/11/007Jovanovic, N., Guyon, O., Martinache, F., et al. 2015,ApJL, 813, L24, doi: 10.1088/2041-8205/813/2/L24Keppler, M., Benisty, M., M¨uller, A., et al. 2018, A&A,617, A44, doi: 10.1051/0004-6361/201832957Keppler, M., Penzlin, A., Benisty, M., et al. 2020, A&A,639, A62, doi: 10.1051/0004-6361/202038032Krist, J. E., Stapelfeldt, K. R., & Watson, A. M. 2002,ApJ, 570, 785, doi: 10.1086/339777Lafreni`ere, D., Marois, C., Doyon, R., & Barman, T. 2009,ApJL, 694, L148, doi: 10.1088/0004-637X/694/2/L148Lafreni`ere, D., Marois, C., Doyon, R., Nadeau, D., &Artigau, ´E. 2007, ApJ, 660, 770, doi: 10.1086/513180Laws, A. S. E., Harries, T. J., Setterholm, B. R., et al.2020, ApJ, 888, 7, doi: 10.3847/1538-4357/ab59e2Marino, S., Perez, S., & Casassus, S. 2015, ApJL, 798, L44,doi: 10.1088/2041-8205/798/2/L44Marois, C., Lafreni`ere, D., Doyon, R., Macintosh, B., &Nadeau, D. 2006, ApJ, 641, 556, doi: 10.1086/500401Mawet, D., Milli, J., Wahhaj, Z., et al. 2014, ApJ, 792, 97,doi: 10.1088/0004-637X/792/2/97M´enard, F., Cuello, N., Ginski, C., et al. 2020, A&A, 639,L1, doi: 10.1051/0004-6361/2020383567