TCP J05074264+2447555: the new transient (10.8 mag) in Taurus is a microlensing event

Association Francaise des Observateurs d'Etoiles Variables (AFOEV)
Tue, 10/31/2017 - 22:05

TCP J05074264+2447555

RA 05h07m42.64s, DEC +24°47'55.5" (J2000.0)

2017 Sept. 2.762 UT, 13.0 mag
2017 Oct. 25.688 UT, 11.7 mag
2017 Oct. 31.734 UT, 10.8 mag
(all CCD, unfiltered)

Discoverer: Tadashi Kojima, Gunma-ken, Japan

2017 10 31.734 UT
Discovered by T. Kojima, Gunma-ken, Japan, who found this on three frames taken using Canon EOS 6D + 135-mm f3.2 lens with the limiting mag.= 13.0. Star is visible on 2017 Sept. 2.762 (mag.= 13.0) and on Oct. 25.688 (mag.= 11.7) UT. Also this star is cataloged on USNO-A2 as mag.= B14.7 and R13.6. An image at

Follow up-reports:

Clear skies,

Association Francaise des Observateurs d'Etoiles Variables (AFOEV)
Microlensing event

Sebastian Otero's suggestion of a microlensing event is supported by Ulisse Munari's (INAF Padova) report: "Just taken a spectrum of the star at the provided coordinates. Nothing unusual, normal absorption stellar spectrum." (BAAVSS alert message)

American Association of Variable Star Observers (AAVSO)
Sketch and estimation

Thank you Patrick

As always you propose us an interresting observation to do.  And here an exotic one, I like it!

Tonight my best visual estimation despite the lunar presence was 12.4, between 12.0 and 12.6.

Here under a sketch of the field