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ASAS-SN Discovery of a Candidate High-Magnification Microlensing Event Located Close to the Galactic Anticenter

ATel #10677; T. Jayasinghe, C. S. Kochanek, K. Z. Stanek (OSU), Subo Dong (KIAA-PKU), J. V. Shields, T. A. Thompson (OSU), T. W.-S. Holoien, B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS)
on 29 Aug 2017; 18:04 UT
Credential Certification: Krzysztof Stanek (stanek.32@osu.edu)

Subjects: Optical, Microlensing Event

Referred to by ATel #: 10710, 10740

As part of an ongoing effort by ASAS-SN project (Shappee et al. 2014; Kochanek et al. 2017) to characterize and catalog all bright variable stars (e.g., Jayasinghe et al. 2017, ATel #10634), we report the discovery of an apparent high-magnification gravitational microlensing event, located close to the Galactic anticenter.

The source ASASSN-V J044558.57+081444.6 (using position from Gaia, g~16.2) has a somewhat red SED and it is located close to the Galactic anticenter and not in the Galactic plane (l,b=189.71,-23.14). ASAS-SN data show a well defined and symmetric event with a clear peak near 12/29/2014. We fit the standard single-lens microlensing models to the ASAS-SN data and find a best-fit model with peak magnification of 33. The best-fit parameters are the time of closest approach t_0=2457023.3 +/- 0.12 days (HJD), the impact parameter u_0=0.031 +/- 0.006 and the Einstein crossing time t_E = 45.2 +/- 0.7. We find no evidence for blending or finite-source effects or variability in the baseline light curve.

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).