ASAS-SN Discovery of a Bright UXOR Candidate
ATel #13881; 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 20 Jul 2020; 16:46 UT
Credential Certification: Tharindu Jayasinghe (jayasinghearachchilage.1@osu.edu)
Subjects: Optical, Star, Variables, Young Stellar Object, Pre-Main-Sequence 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 "Cassius" and "Cecilia Payne-Gaposchkin" telescopes, we identified a likely intermediate mass UXOR candidate undergoing a series of dimming episodes. The ASAS-SN variable source ASASSN-V J170615.23-322944.7 (position from Gaia DR2, source_id=5980061430703488384, d~1270 pc, R~4.4 R_sun, Teff~5829 K, L~19.8 L_sun) was first observed by ASAS-SN on UT 2016-03-09. The Gaia temperature and luminosity estimates are indicative of a young intermediate mass star approaching the ZAMS. We do not see evidence of an infrared excess in the SED. The line of sight extinction (Schlafly & Finkbeiner 2011) to ASASSN-V J170615.23-322944.7 is significant (A_V~1.6 mag, A_g~1.9 mag) as it is located in the Galactic disk with (l,b)~(352.314,5.024). Presently, ASASSN-V J170615.23-322944.7 has more than ~1700 data points over a baseline of ~1590 days.
ASASSN-V J170615.23-322944.7 has a quiescent mean magnitude of V~12.25 . The star gradually began dimming on UT 2017-06-22, and shows irregular light curve behavior beyond this epoch. ASASSN-V J170615.23-322944.7 underwent a major dimming episode in the g-band data beginning on UT 2019-04-14 at g~12.7, dropping to g~13.4 on UT 2020-03-09 and has recovered to g~12.5 as of UT 2020-07-19. We do not see evidence for significant periodic variability. Such irregular dimming episodes are characteristic of UXOR stars and are the results of variable extinction caused by circumstellar dust around young intermediate mass (Herbig Ae) stars (Natta et al. 1997). 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.
