ASAS-SN Discovery of a Heavily Reddened Eclipsed Giant Star in a 750 day Orbit
ATel #13745; 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 May 2020; 17:05 UT
Credential Certification: Tharindu Jayasinghe (jayasinghearachchilage.1@osu.edu)
Subjects: Optical, Binary, 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", and "Leavitt", telescopes, we identified an eclipsed giant star in a ~750 day orbit. The ASAS-SN variable source ASASSN-V J182318.71-125848.2 (position from Gaia DR2, source_id=4152751690383952128, d~1.8 kpc, R~43 R_sun, Teff~3431 K, L~227 L_sun) was first observed by ASAS-SN on UT 2015-02-01. The line of sight extinction from the Bayestar19 dust maps (Green et al. 2019) to ASASSN-V J182318.71-125848.2 is significant (A_V~4.29 mag, A_g~4.96 mag) as it is located in the Galactic disk with (l,b)~(18.200,0.215). Assuming a distance of d~1.8 kpc (Bailer-Jones et al., 2018), this source has M_V~-2.9 mag (M_g~-2.4 mag). Presently, ASASSN-V J182318.71-125848.2 has more than ~1570 data points over a baseline of ~1930 days.
ASASSN-V J182318.71-125848.2 has a quiescent mean magnitude of g~13.8 (V~12.7). The eclipse with an ingress on UT 2016-03-14 was observed in the V-band, the eclipse with an ingress on UT 2018-04-12 was observed in both the V and g-bands, and the current on-going eclipse beginning on UT 2020-04-27 is being observed in the g-band . The eclipse depth in the V-band (g-band) is ~0.4 mag (~0.7 mag). We estimate the orbital period and the eclipse duration as P_orb~750 days, and t_ecl ~23 days, respectively. ASASSN-V J182318.71-125848.2 has been in eclipse for 19 days as of UT 2020-05-20. We do not see evidence for significant variability when the system is out-of-eclipse. 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.
