Spectroscopic observation of TCP J18325790-1642211
ATel #12633; Hiroyuki Maehara (NAOJ), Miho Kawabata (Kyoto U.), Masayuki Yamanaka (Kyoto U.), Keiichi Maeda (Kyoto U.), Keisuke Isogai (Kyoto U.), Masaru Kino (Kyoto U.)
on 6 Apr 2019; 05:03 UT
Credential Certification: Hiroyuki Maehara (hiroyuki.maehara@nao.ac.jp)
Subjects: Optical, Microlensing Event, Star, Transient, Variables
We report the spectroscopic observation of TCP J18325790-1642211 discovered by T. Kojima on 2019-04-02.7544 UT at 12.5 mag (http://www.cbat.eps.harvard.edu/unconf/followups/J18325790-1642211.html). According to follow-up reports by S. Kiyota and K. Yoshimoto, this object is identical to a 16 mag star Gaia DR2 4102798575018377600. As pointed out by P. Schmeer (vsnet-alert 23123), the light curve of this object from the All-Sky Automated Survey for Supernovae (ASAS-SN; Shappee et al. 2014 and Kochanek et al. 2017) is similar to that of a microlensing event.
We obtained a low-resolution spectrum of the object on 2019-04-03.827 UT using the fiber-fed integral field spectrograph (KOOLS-IFU) mounted on the 3.8-m Seimei telescope at Okayama Observatory, Kyoto University (the Seimei telescope is a new 3.8-meter diameter optical-infrared telescope of Kyoto University located in Okayama, Japan; it started scientific operation since March 2019).The spectrum shows a red continuum with H-alpha, Na I D, and Mg I b absorption lines. No emission features are present in the spectrum. The overall appearance of the spectrum between 450 nm and 800 nm is similar to that of a normal K-type star. This result supports that the object is a microlensing event, rather than a cataclysmic variable or a Mira-type star.
