Detection of a Microlensing Event of a Magnified Star at Redshift z = 1.5
ATel #11708; Patrick Kelly (UMN), Jose Maria Diego (IFCA), Liliya Williams (UMN), Pablo Perez-Gonzalez (UCM), Alexei V. Filippenko (UC Berkeley), Masamune Oguri (Tokyo), Alberto Molino Benito (IAG), Jens Hjorth (DARK)
on 12 Jun 2018; 03:36 UT
Credential Certification: Patrick Kelly (pkelly@astro.berkeley.edu)
Subjects: Optical, Request for Observations, Microlensing Event, Star, Transient, Gravitational Lensing
Referred to by ATel #: 11724
On June 5, 2018 UT, we acquired simultaneous g and r broadband imaging of the MACS J1149 galaxy cluster (redshift z = 0.54) field with the Large Binocular Telescope (LBT). We report the detection of a bright unresolved source with a position consistent with the image (or likely counterimage) of Lensed Star 1 (LS1), a highly magnified blue supergiant star at z = 1.49 (Kelly et al. 2018). We measure preliminary magnitudes of g = 26.9 +/- 0.2 mag AB and r = 26.4 +/- 0.3 mag AB, which imply a color statistically consistent with that of LS1. The measured optical flux densities are comparable to those observed during LS1's May 2016 microlensing peak, when the star's magnification likely reached several thousand. A Gemini Director's Discretionary Time program (GN-2018A-DD-107) for imaging follow up has been approved, and all observations of the microlensing event are encouraged.
