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ASAS-SN Confirmation of the Bright Microlensing Event TCP J05074264+2447555

ATel #10923; T. Jayasinghe (OSU), Subo Dong (KIAA-PKU), K. Z. Stanek, C. S. Kochanek, T. A. Thompson (OSU), J. L. Prieto (Diego Portales; MAS), B. J. Shappee (Univ. of Hawaii), T. W.-S. Holoien (Carnegie)
on 2 Nov 2017; 18:57 UT
Credential Certification: Krzysztof Stanek (stanek.32@osu.edu)

Subjects: Optical, Microlensing Event

Referred to by ATel #: 10926, 10934

The transient TCP J05074264+2447555 was first discovered by T. Kojima on UT 2017-10-25.688. The ASAS-SN Sky Patrol light curve (Shappee et al. 2014; Kochanek et al. 2017) and follow-up spectroscopy (ATel #10919) suggested this to be a probable microlensing event. The ASAS-SN light curve for TCP J05074264+2447555 showed no evidence of intrinsic variability. Swift observations (ATel #10921) found no X-ray source at the position of this transient, but reported brightening in the UV similar to the brightening observed in the optical, which is expected for a microlensing event.

The source TCP J05074264+2447555 was first observed by ASAS-SN on UT 2014-12-16.399. The latest ASAS-SN photometry on UT 2017-11-02.411 suggests that TCP J05074264+2447555 is fading, as was predicted by microlensing models. The ASAS-SN light curve is well fit by a single-lens microlensing model with a peak magnitude of V~11.5, time of closest approach t_0=2458058.80 +/- 0.03 days (HJD), impact parameter u_0=0.091 +/- 0.005 and Einstein crossing time t_E = 26.7 +/- 1.2 days for a peak magnification of 11. This best-fit model is consistent with no blending.

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).