16918( 3) - 10-Mar-2023 20:00:41 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16918 Version: 3 Check-in Time: 10-Mar-2023 20:00:41 STScI Edit Number: 0 Title The afterglow and host of GRB 210905A at z=6.3 ------------------------------------------------------------------------------------ Type Cycle GO 29 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Nial Rahil Tanvir University of Leicester Y CoI: Dr. Andrea Rossi INAF-Osservatorio di Astrofisica e Scienza N dello Spazio CoI: Prof. Andrew James Levan Radboud Universiteit Nijmegen N CoI: Dr. Andrew S. Fruchter Space Telescope Science Institute N CoI: Dr. Antonino Cucchiara College of Marin N CoI: Dr. David Kann Thuringer Landessternwarte Tautenburg N (TLS) CoI: Dr. Giovanna Pugliese Universiteit van Amsterdam N CoI: Dr. Darach Watson University of Copenhagen, Niels Bohr N Institute CoI: Dr. Massimiliano De Pasquale Istanbul University Science Faculty, N Department of Astronomy CoI: Dr. Kasper Elm Heintz University of Iceland N CoI: Dr. Susanna Vergani Observatoire de Paris - Section de Meudon N CoI: Dr. Luca Izzo University of Copenhagen, Niels Bohr N Institute CoI: Dr. Daniele Bjorn Malesani Radboud Universiteit Nijmegen N ------------------------------------------------------------------------------------ Abstract The recently discovered GRB 210905A is the highest redshift GRB for which an early, high-S/N, mid-high resolution afterglow spectrum has been obtained. In addition to providing the redshift, this spectrum exhibits numerous metal lines and a complex velocity structure spanning ~360 km/s, and blueshifted by ~1000 km/s from a tentative Ly-a emission line. Modelling of the Lyman-alpha damping wing reveals the host column density, and puts constraints on the neutral fraction of the surrounding intergalactic medium. Analysis of the abundances gives an average metallicity Z~Zsol/20. In addition, the afterglow of this GRB started bright and has declined slowly, implying a late jet break. This suggests a wide jet and hence a particularly high energy event, perhaps indicative of an unusual progenitor star. Here we seek HST WFC3/IR F140W imaging to obtain a final late-time point on the afterglow light curve to constrain any break, and an image after the afterglow has faded, to provide a subtraction template and characterisation of the host galaxy. This would make it the first galaxy at z>6 detected in emission for which detailed absorption line abundances for multiple species are available. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will obtain two vists for observations of GRB 210905A. The first will aim to capture light from the afterglow while the second will search for the host galaxy. Both visits will use F140W. The first will be a two orbit visit while 16918( 3) - 10-Mar-2023 20:00:41 - [ 2] the second will require a 4-orbit exposure. We will use a standard 4 point dither pattern for the 2 orbit visit and a 8-point dither pattern for the 4 orbit visit, acquiring two exposures per orbit. ------------------------------------------------------------------------------------ 16918( 3) - 10-Mar-2023 20:00:41 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB210905A GALAXY, STARBURST RA=20H36M11.5700S, J2000 V = 30 +/- 2 H(AB)~27 DEC=-44D26'24.80" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 16918( 3) - 10-Mar-2023 20:00:41 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-BOX-MIN Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.572 Line_Spacing 0.365 Coordinate_Frame POS-TARG Pattern_Orient 18.528 Angle_Between_Sides 74.653 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 16918( 3) - 10-Mar-2023 20:00:41 - [ 5] Visit: 01 Visit Requirements: SCHED 100%; BEFORE 30-JUN-2022:00:00:00 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB210905A WFC3/IR MULTIAC IR F140W NSAMP=13, SAMP-SEQ=STEP200 1 DEF PATTERN 2 1 CUM (4796.925 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ GRB210905A 1 WFC3/IR MULTIAC IR F140W 1 none none none 1 N/A CUM GRB210905A 1 WFC3/IR MULTIAC IR F140W 2 none none none 1 N/A CUM GRB210905A 1 WFC3/IR MULTIAC IR F140W 3 none none none 2 N/A CUM GRB210905A 1 WFC3/IR MULTIAC IR F140W 4 none none none 2 N/A CUM 16918( 3) - 10-Mar-2023 20:00:41 - [ 6] Visit: 02 Visit Requirements: SCHED 100%; SAME ORIENT AS 01; AFTER 31-MAR-2023:00:00:00 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB210905A WFC3/IR MULTIAC IR F140W NSAMP=13, SAMP-SEQ=STEP200 1 DEF PATTERN 2 1 CUM (4796.925 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ GRB210905A 1 WFC3/IR MULTIAC IR F140W 1 none none none 1 N/A CUM GRB210905A 1 WFC3/IR MULTIAC IR F140W 2 none none none 1 N/A CUM GRB210905A 1 WFC3/IR MULTIAC IR F140W 3 none none none 2 N/A CUM GRB210905A 1 WFC3/IR MULTIAC IR F140W 4 none none none 2 N/A CUM 16918( 3) - 10-Mar-2023 20:00:41 - [ 7] Visit: 03 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB210905A WFC3/UVI ACCUM UVIS2-C1K F775W CR-SPLIT=NO, FLASH=12 1 370 S PATTERN 1 1 S 1C-CTE see below (2440 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 GRB210905A WFC3/UVI ACCUM UVIS2-C1K F775W CR-SPLIT=NO, FLASH=12 1 370 S PATTERN 1 2 S 1C-CTE see below (2432 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ GRB210905A 1 WFC3/UVI ACCUM UVIS2-C1 F775W 1 none none none 1 610.0 S S K1C-CTE GRB210905A 1 WFC3/UVI ACCUM UVIS2-C1 F775W 2 none none none 1 610.0 S S K1C-CTE GRB210905A 1 WFC3/UVI ACCUM UVIS2-C1 F775W 3 none none none 1 610.0 S S K1C-CTE GRB210905A 1 WFC3/UVI ACCUM UVIS2-C1 F775W 4 none none none 1 610.0 S S K1C-CTE GRB210905A 2 WFC3/UVI ACCUM UVIS2-C1 F775W 1 none none none 2 608.0 S S K1C-CTE GRB210905A 2 WFC3/UVI ACCUM UVIS2-C1 F775W 2 none none none 2 608.0 S S K1C-CTE GRB210905A 2 WFC3/UVI ACCUM UVIS2-C1 F775W 3 none none none 2 608.0 S S K1C-CTE GRB210905A 2 WFC3/UVI ACCUM UVIS2-C1 F775W 4 none none none 2 608.0 S S K1C-CTE 16918( 3) - 10-Mar-2023 20:00:41 - [ 8] Summary Form for Proposal 16918 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR, UVIS2-C1K1C-CTE ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO, FLASH=12, NSAMP=13, SAMP-SEQ=STEP200 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 31-MAR-2023:00:00:00, BEFORE 30-JUN-2022:00:00:00, PATTERN 1 1, PATTERN 1 2, PATTERN 2 1, SAME ORIENT AS 01, SCHED 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F140W, F775W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GRB210905A ------------------------------------------------------------------------------------------------------------------------------------