No Bright, Early June 2018 Microlensing Event in MACS1149 Galaxy-Cluster Field
ATel #11724; Patrick Kelly (UMN), Liliya William (UMN), Alex Filippenko (UC Berkeley)
on 16 Jun 2018; 18:15 UT
Credential Certification: Patrick Kelly (plkelly@umn.edu)
Subjects: Optical, Microlensing Event, Transient, Gravitational Lensing
In ATel #11708, we reported the detection of an unresolved source coincident with the position of the lensed star Icarus in a single epoch of ground-based g-band imaging of the MACS J1149 galaxy cluster on June 5, 2018 UT. Given the possibility of a bright and quickly evolving microlensing event, we obtained rapid follow-up imaging. In a detailed subsequent analysis using convolved archival 2011 Hubble Space Telescope (HST) ACS WFC F475W images as a template, we find that an underlying arc and the lensed star with typical magnification of up to hundreds (as opposed to thousands as observed in May 2016) can account for the flux at Icarus' position in June 5, 2018 UT Large Binocular Telescope and follow-up Gemini June 14, 2018 UT optical images.
