0 Assigned ID: 2677 ----- Attempting Submission 1 (Mon Jan 31 17:10:50 GMT 2022) ----- HST Phase I Proposal 2677 successfully submitted. Receipt: # 2677-1 0 ----- Attempting Submission 1 (Fri Mar 11 16:50:17 GMT 2022) ----- Neutron star mergers are confirmed sites of r-process nucleosynthesis, observationally identified by their kilonovae. In particular, the study of short gamma-ray bursts (SGRBs), which span z~0.1-2, are a promising avenue to uncover kilonovae. Monitoring the temporal and color evolution of SGRB-kilonovae provides quantifiable estimates of their ejecta masses and compositions, of interest to assessing the contribution of such mergers to the universe's heavy element budget. In particular, the identification of nearby (z<0.1) kilonovae provide great distinguishing power. Recently, GRB 211211A was discovered in likely association with a galaxy at 350 Mpc (z=0.076). At this distance, the detection and temporal behavior of an associated NIR transient is fully consistent with a kilonova. If the distance is confirmed, this would make GRB 211211A the most nearby such event beyond the multi-messenger GW170817. We propose 2 orbits of HST imaging to secure the nearby origin of GRB 211211A by placing constraints on an underlying, unseen galaxy. Current ground-based observations have reached their limits, and cannot rule out the full range of known host galaxy luminosities and redshifts. If an underlying galaxy is detected from a higher-redshift origin, the NIR transient would be equally exciting, outshining any known kilonova or supernova to date. This proposal is for 2 orbits of imaging at the position of the afterglow of GRB 211211A with ACS/WFC/F606W (1 orbit) and WFC3/IR/F140W (1 orbit). These observations are to place deep constraints on an underlying host galaxy and to calculate a precise offset between the counterpart and the center of the host galaxy. The expected brightness of the afterglow is > 28 mag. The putative host galaxy is r = 19.8 AB mag. PI Jillian Rastinejad (Northwestern) is a 3rd year PhD student who has published a catalog and aggregate analysis of all previous SGRB kilonova observations (Rastinejad et al. 2021). The data in this proposal will support at least one chapter of her thesis focused on kilonovae from SGRBs and gravitational wave-detected sources. Professors Wen-fai Fong (Northwestern), Andrew Levan (Radboud), Nial Tanvir (Leicester) and Dr. Charles Kilpatrick (Northwestern) are experts in the reduction and analysis of WFC3 observations that probe the environments of GRBs and other transients, and will serve as the scientific supervising team. Dr. Ben Gompertz (Birmingham), Dr. Gavin Lamb (Leicester), and Professor Matt Nicholl (Birmingham) are experts in the modeling of GRB afterglows and kilonovae (e.g., Lamb et al. 2019, Nicholl et al. 2021). Anya Nugent (Northwestern) has extensive experience observing and modeling the host galaxies of SGRBs, and will provide support for the stellar population interpretation of G1. Dr. Daniele Malesani (Radboud), Dr. Alicia Rouco Escorial (Northwestern) and Genevieve Schroeder (Northwestern) have extensive experience reducing and analyzing multi-wavelength observations of GRB afterglows, and have contributed to the multi-wavelength data set on this GRB. Stellar Physics and Stellar Types 3 false false false false false true false SUPPORTED EXT-STAR GAMMA RAY BURSTER NEUTRON STAR J2000 J2000 WFC3/IR Imaging No No F140W ACS/WFC Imaging No No F606W POS-TARG DITHER 0.262 LINE 0.192 false false 68.14 4 18.39 ACS-WFC-DITHER-BOX 1 false POS-TARG DITHER 0.572 LINE 0.365 false false 74.653 4 18.528 WFC3-IR-DITHER-BOX-MIN 3 false /private/var/folders/t6/m9nk5mrn22dbs6gmjwxz9rlm0000gn/T/OPVisit10522269274204526295.xml 1647017263788 The scheduling data was generated by CASM 30.1. CASM was run in Phase II mode. 1-orbit observation with ACS/WFC/F606W. 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