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ASAS-SN Discovery of an Unusual Stellar System with Deep Dimming Episodes

ATel #13106; Z. Way, T. Jayasinghe, K. Z. Stanek, C. S. Kochanek, 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), M. Stritzinger (Aarhus)
on 13 Sep 2019; 20:02 UT
Credential Certification: Tharindu Jayasinghe (jayasinghearachchilage.1@osu.edu)

Subjects: Optical, Binary, Star, Variables

Referred to by ATel #: 13111

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 "Paczynski" telescopes, we identified a stellar source undergoing an unusual dimming episode. The source ASASSN-V J190917.06+182837.36 (position from Gaia DR2, source_id=4514564064737161344, d=1.3 kpc) was first observed by ASAS-SN on UT 2015-02-08. Presently, ASASSN-V J190917.06+182837.36 has more than ~1380 data points.

The source ASASSN-V J190917.06+182837.36 has a quiescent mean magnitude of g~13.9 (V~13.2) . The latest ASAS-SN photometry shows that ASASSN-V J190917.06+182837.36 gradually faded from g~13.9 on UT 2019-09-09.85, to g~14.9 on 2019-09-12.15. The source might be returning to its quiescent flux, brightening to g~14.7 on UT 2019-09-12.36. Over the previous ~1670 days there may have been one other dimming episode on UT 2016-09-08.31 in the ASAS-SN V/g-band photometry. If the events are periodic, we estimate the period to be ~1100 days (~3 yrs). There are no matches in Vizier or AAVSO to a known variable star. This event appears similar to the dimming event reported in ATel #12836, where ASASSN-V J213939.3-702817.4 was quiescent at g~12.9 and briefly faded to g~14.2. Additional follow-up observations 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 .