English

An Asymmetric Eclipse Seen Towards the Pre-Main Sequence Binary System V928 Tau

Solar and Stellar Astrophysics 2020-12-02 v1 Earth and Planetary Astrophysics

Abstract

K2 observations of the weak-lined T Tauri binary V928 Tau A+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 hours, one component of the binary dims by around 60%, returning to its normal brightness about 5 hours 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±0.0005R0.9923\,\pm\,0.0005\,R_*, with an inclination of 56.78±0.0356.78\,\pm\, 0.03^\circ, a tilt of 41.22±0.0541.22\,\pm\,0.05^\circ, an impact parameter of 0.2506±0.0002R-0.2506\,\pm\,0.0002\,R_* and an opacity of 1.00. The occulting disk must also move at a transverse velocity of 6.637±0.002Rday16.637\,\pm\,0.002\,R_*\,\mathrm{day}^{-1}, which depending on whether it orbits V928 Tau A or B, corresponds to approximately 73.53 or 69.26 kms1\mathrm{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 which is used to further refine the orbit of the binary, presenting a new lower bound of 67 years, and constraints on the possible orbital periods of the eclipsing companion. The binary is also separated by 18" (\sim2250 au) from the lower mass CFHT-BD-Tau 7, which is likely associated with V928 Tau A+B. We also present new high dispersion optical spectroscopy that we use to characterize the unresolved stellar binary.

Keywords

Cite

@article{arxiv.2010.11199,
  title  = {An Asymmetric Eclipse Seen Towards the Pre-Main Sequence Binary System V928 Tau},
  author = {Dirk van Dam and Matthew Kenworthy and Trevor David and Eric Mamajek and Lynne Hillenbrand and Anne Marie Cody and Andrew Howard and Howard Isaacson and David Ciardi and Luisa Rebull and John Stauffer and Rahul Patel and Andrew Collier Cameron and Joseph Rodriguez and Grzegorz Pojmański and Erica Gonzales and Joshua Schlieder and Franz-Josef Hambsch and Sjoerd Dufoer and Tonny Vanmunster and Franky Dubois and Siegfried Vanaverbeke and Ludwig Logie and Steve Rau},
  journal= {arXiv preprint arXiv:2010.11199},
  year   = {2020}
}

Comments

30 pages, 9 tables, 10 figures, accepted for publication in ApJ, GitHub repository for scripts and figures on https://github.com/dmvandam/v928tau

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