ASAS-SN Discovery of a Luminous Star undergoing a Deep Dimming Event
ATel #14007; Z. Way, D. Desai, K. Z. Stanek, T. Jayasinghe, C. S. Kochanek, 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), M. Stritzinger (Aarhus)
on 11 Sep 2020; 21:16 UT
Credential Certification: Tharindu Jayasinghe (jayasinghearachchilage.1@osu.edu)
Subjects: Optical, Star, Variables
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" telescope, we identified a stellar source undergoing an extreme dimming event. The source ASASSN V J193622.23+115244.1 (Gaia DR2: source_id=4315228344710978816, d=2021 pc, L = 9.31 L_sun, Teff=6364 K) was first observed by ASAS-SN on UT 2015-02-12 and identified as a transient on 2020-09-10. The line of sight extinction from the Bayestar19 dust maps (Green et al. 2019) to ASASSN V J193622.23+115244.1 is A_V~0.4 mag (A_g~0.5 mag). ASASSN V J 193622.23+115244.1 is close to the Galactic plane with (l,b)~(48.6499,-4.3470). Presently, ASASSN V J193622.23+115244.1 has more than ~2010 ASAS-SN epochs.
The source ASASSN V J193622.23+115244.1 has a quiescent mean magnitude of g~14.0 (V~13.8). The latest ASAS-SN photometry shows that ASASSN V J193622.23+115244.1 began to dim on UT 2020-09-03 and then reached its latest magnitude of g~15.5 on UT 2020-09-10. This source has displayed previous variability, as is seen in the complete ASAS-SN V/g-band light curve. Other deep, dimming events have occurred (~UT 2015-08-05, ~UT 2019-07-15) but they are not as dramatic as the current event, only losing about half of a magnitude. It has been classified as a dubious variable by ATLAS (Heinze et.al. 2018).
Follow-up observations of this interesting object are strongly encouraged.
We 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 grant AST-1515927, 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.
