VLT spectroscopic observations of highly magnified Galactic Disk microlensing event Gaia18bmt
ATel #11719; L. Wyrzykowski, M. Gromadzki, K. Kruszynska, K. A. Rybicki, P. Zielinski (Warsaw University Astronomical Observatory)
on 15 Jun 2018; 08:54 UT
Credential Certification: Lukasz Wyrzykowski (wyrzykow@astrouw.edu.pl)
Subjects: Optical, Microlensing Event, Transient
Gaia18bmt (Ra, Dec = 14:16:03.55, -56:54:48.24) was found by Gaia Science Alerts programme on 2018-06-11 (http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia18bmt/) as a significant brigthening by more than 2 mag on a 15.5 mag star in the Galactic Disk (l,b = 314.32362, 4.07498).
Gaia low-resolution spectra (BP/RP) indicate no significant change in colour of the star while getting brighter. The light curve composed of multiple Gaia observations shows a fast rise to about G=12.95 on 2018-06-13.13. The microlensing model (Paczynski's curve) fit to Gaia data suggests Einstein crossing time tE of about 50 days. The peak of the event is expected to happen between 14.June and 18.June.
The target was observed with ESO VLT/XSHOOTER instrument on 2018-06-13. The high quality spectrum shows a G/K-type giant star with a significant amount of extinction.
Further follow-up observations in the next days as the event passes through its peak brightness are strongly encouraged.
We acknowledge ESA Gaia, DPAC and the Photometric Science Alerts Team (http://gsaweb.ast.cam.ac.uk/alerts).
We thank ESO/VLT staff for support. Observations were carried out under
ESO programmes 0101.D.0035(A), PI: Wyrzykowski.
