ASAS-SN Discovery of a Likely RCB Variable ASASSN-V J183900.17-405428.9
ATel #13159; 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 2 Oct 2019; 17:57 UT
Credential Certification: Tharindu Jayasinghe (jayasinghearachchilage.1@osu.edu)
Subjects: Star, Variables
As part of an ongoing effort by the ASAS-SN project (Shappee et al. 2014; Kochanek et al. 2017; Jayasinghe et al. 2019) to characterize and catalog all bright variable stars, we report the discovery of a Galactic R Coronae Borealis (RCB) variable candidate.
The source ASASSN-V J183900.17-405428.9 (position from Gaia DR2, source_id=6722717561729838080, g~17.5) was first observed by ASAS-SN on UT 2014-08-27.09. Presently, ASASSN-V J183900.17-405428.9 has more than ~2100 V-band and g-band data points.
We noted the unusual variability of this object as it rose ~1.5 mag in the g-band on UT 2019-09-28. The ASAS-SN Sky Patrol light curve shows that ASASSN-V J183900.17-405428.9 displayed a similar spike of >0.8 mag in the V-band on UT 2015-03-31. Such large and rapid declines are typical of dust production episodes in RCB stars.
This source was previously flagged as a potential RCB star based on its WISE and 2MASS colors (Tisserand et al. 2012). Additionally, it is listed as a Galactic infrared carbon star (Chen et al. 2012). The last 100 days of ASAS-SN light curve data may be found here. Further photometric and spectroscopic observations are 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.
