ASAS-SN Detection of a Dramatic Dimming Episode of the Galactic Wolf-Rayet Star WR96

ATel #12488; T. Jayasinghe, K. Z. Stanek, C. S. Kochanek, P. Vallely, J. V. Shields, 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 10 Feb 2019; 00:24 UT
Credential Certification: Krzysztof Stanek (stanek.32@osu.edu)

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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 "Cassius" and "Paczynski" telescopes in CTIO, Chile, we detected a deep (delta_g ~>2 mag) dimming episode in the Galactic Wolf-Rayet star WR96, most likely due to dust formation in its wind/circumstellar region.

The source WR96 is a known Galactic Wolf-Rayet star with a spectral type of WC9d and has a quiescent mean magnitude of g~14.6 (V~13.6) in ASAS-SN data. WR96 was first observed by ASAS-SN on UT 2016-03-09 and has >1700 epochs of ASAS-SN photometry over a >1000 day baseline. Prior to the current dimming episode, we do not detect significant intrinsic variability or eclipses . The latest ASAS-SN photometry suggests that WR96 has faded by >2 mag in the g-band (g<16.5). To our knowledge, previous dimming episodes were not observed for this source (Williams 2014). WCd stars that are monitored over long baselines commonly show these ``eclipses'' that are likely due to clumps in the circumstellar regions (Becker 2015). Additional follow-up observations are strongly encouraged.

We would like to 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, the Chinese Academy of Sciences South America Center for Astronomy (CASSACA), and the Villum Fonden (Denmark).