ASAS-SN Discovery of an Unusually Luminous Cataclysmic Variable Candidate Undergoing a Dimming Episode
ATel #13824; T. Jayasinghe, K. Z. Stanek, C. S. Kochanek, Z. Way, P. Vallely, C. Basinger, T. A. Thompson (OSU), B. J. Shappee (Univ. of Hawaii), T. W.-S. Holoien (Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), Subo Dong (KIAA-PKU)
on 22 Jun 2020; 22:32 UT
Credential Certification: Tharindu Jayasinghe (jayasinghearachchilage.1@osu.edu)
Subjects: Optical, Cataclysmic Variable, Star
During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014, Kochanek et al. 2017), using data from the quadruple 14-cm "Brutus", and "Leavitt", telescopes, we identified a likely cataclysmic variable star undergoing a dimming episode. The ASAS-SN variable source ASASSN-V J205457.73+515731.9 (position from Gaia DR2, source_id=2170074115128375680, d~564 pc, R~0.53 R_sun, Teff~7489 K, L~0.78 L_sun) was first observed by ASAS-SN on UT 2015-03-02. The Gaia temperature estimate is indicative of a hot companion/accretion disk. The line of sight extinction from the Bayestar19 dust maps (Green et al. 2019) to ASASSN-V J205457.73+515731.9 is significant (A_V~1.3 mag, A_g~1.7 mag) as it is located in the Galactic disk with (l,b)~(90.895,4.452). Presently, ASASSN-V J205457.73+515731.9 has more than ~2300 data points over a baseline of ~1930 days.
ASASSN-V J205457.73+515731.9 has a quiescent mean magnitude of g~13.8 (V~13.6). A dimming episode with an ingress on UT 2017-03-27 was observed in the V-band, with the star reaching a minimum brightness of V~13.8 at UT 2017-04-08, and returning to its quiescent state over a total duration of t~30 days. ASASSN-V J205457.73+515731.9 is currently undergoing a dimming episode, beginning on UT 2020-05-28 and is at g~14.4 as of UT 2020-06-22. The current dimming episode is slower and deeper than the previously observed event in the V-band data. We do not see evidence for significant periodic variability when the system is quiescent.
Such dimming episodes are characteristic of VY Scl stars and are the results of low mass transfer episodes from the companion star (Leach 1999). However, ASASSN-V J205457.73+515731.9 is more luminous than typical CVs, with M_V~4.8 mag and M_g~5.0 mag. Further photometric and spectroscopic observations are encouraged.
We also thank Las Cumbres Observatory and its staff for their continued support of ASAS-SN. ASAS-SN is funded in part by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University, NSF grants AST-1515927 and AST-1908570, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, and the Chinese Academy of Sciences South America Center for Astronomy (CASSACA). For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.
