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An Asymmetric Eclipse Seen toward the Pre-main-sequence Binary System V928 Tau

van Dam, Dirk M. and Kenworthy, Matthew A. and David, Trevor J. and Mamajek, Eric E. and Hillenbrand, Lynne A. and Cody, Ann Marie and Howard, Andrew W. and Isaacson, Howard and Ciardi, David R. and Rebull, Luisa M. and Stauffer, John R. and Patel, Rahul and Cameron, Andrew Collier and Rodriguez, Joseph E. and Pojmański, Grzegorz and Gonzales, Erica J. and Schlieder, Joshua E. and Hambsch, Franz-Josef and Dufoer, Sjoerd and Vanmunster, Tonny and Dubois, Franky and Vanaverbeke, Siegfried and Logie, Ludwig and Rau, Steve (2020) An Asymmetric Eclipse Seen toward the Pre-main-sequence Binary System V928 Tau. Astronomical Journal, 160 (6). Art. No. 285. ISSN 1538-3881.

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K2 observations of the weak-lined T Tauri binary V928 Tau A and B show the detection of a single, asymmetric eclipse, which may be due to a previously unknown substellar companion eclipsing one component of the binary with an orbital period >66 days. Over an interval of about 9 hr, one component of the binary dims by around 60%, returning to its normal brightness about 5 hr later. From modeling of the eclipse shape, we find evidence that the eclipsing companion may be surrounded by a disk or a vast ring system. The modeled disk has a radius of 0.9923 ± 0.0005 R*, with an inclination of 56 78 ± 0 03, a tilt of 41 22 ± 0 05, an impact parameter of −0.2506 ± 0.0002 R*, and an opacity of 1.00. The occulting disk must also move at a transverse velocity of 6.637 ± 0.002 R* day⁻¹, which, depending on whether it orbits V928 Tau A or B, corresponds to approximately 73.53 or 69.26 km s⁻¹. A search in ground-based archival data reveals additional dimming events, some of which suggest periodicity, but no unambiguous period associated with the eclipse observed by K2. We present a new epoch of astrometry that is used to further refine the orbit of the binary, presenting a new lower bound of 67 yr, and constraints on the possible orbital periods of the eclipsing companion. The binary is also separated by 18'' (~2250 au) from the lower-mass CFHT-BD-Tau 7, which is likely associated with V928 Tau A and B. We also present new high-dispersion optical spectroscopy that we use to characterize the unresolved stellar binary.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Kenworthy, Matthew A.0000-0002-7064-8270
David, Trevor J.0000-0001-6534-6246
Mamajek, Eric E.0000-0003-2008-1488
Cody, Ann Marie0000-0002-3656-6706
Howard, Andrew W.0000-0001-8638-0320
Isaacson, Howard0000-0002-0531-1073
Ciardi, David R.0000-0002-5741-3047
Rebull, Luisa M.0000-0001-6381-515X
Stauffer, John R.0000-0003-3595-7382
Patel, Rahul0000-0002-5025-6827
Rodriguez, Joseph E.0000-0001-8812-0565
Gonzales, Erica J.0000-0002-9329-2190
Schlieder, Joshua E.0000-0001-5347-7062
Additional Information:© 2020 The American Astronomical Society. Received 2020 July 18; revised 2020 October 14; accepted 2020 October 17; published 2020 November 26. We thank Dan Foreman-Mackey, Ian Czekala, and Sarah Blunt for helpful discussions on the astrometric modeling. This paper includes data collected by the Kepler mission and obtained from the MAST data archive at the Space Telescope Science Institute (STScI). Funding for the Kepler mission is provided by the NASA Science Mission Directorate. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 526555. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). T.J.D. and E.E.M. gratefully acknowledge support from the Jet Propulsion Laboratory Exoplanetary Science Initiative and NASA award 17-K2GO6-0030. Some of the data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This work has made use of data from the Asteroid Terrestrial-impact Last Alert System (ATLAS) project. ATLAS is primarily funded to search for near-Earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; byproducts of the NEO search include images and catalogs from the survey area. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queen's University Belfast, the Space Telescope Science Institute, and the South African Astronomical Observatory. Software: EVEREST (v2.0; Luger et al. 2016, 2018), lightkurve (v1.9.0; Lightkurve Collaboration et al. 2018), exoplanet (Foreman-Mackey et al. 2020), PyMC3 (v3.8; Salvatier et al. 2016), Scipy (v1.4.1; Virtanen et al. 2020), Matploltib (v3.2.2; Hunter 2007), Astropy (v4.0; Astropy Collaboration et al. 2013; Price-Whelan et al. 2018), Numpy (v1.18.1; Harris et al. 2020), jktld (v3.0; Southworth 2015).
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASANAS 5-26555
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:Planetary rings ; Pre-main sequence stars ; Astrometric binary stars ; Eclipses ; Substellar companion stars
Issue or Number:6
Classification Code:Unified Astronomy Thesaurus concepts: Planetary rings (1254); Pre-main sequence stars (1290); Astrometric binary stars (79); Eclipses (442); Substellar companion stars (1648)
Record Number:CaltechAUTHORS:20201103-103003753
Persistent URL:
Official Citation:Dirk M. van Dam et al 2020 AJ 160 285
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106391
Deposited By: Tony Diaz
Deposited On:04 Nov 2020 17:50
Last Modified:03 Dec 2020 22:35

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