16458( 2) - 11-Nov-2020 15:04:49 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16458 Version: 2 Check-in Time: 11-Nov-2020 15:04:49 STScI Edit Number: 0 Title A long gamma-ray burst from the nucleus of an ancient galaxy ------------------------------------------------------------------------------------ Type Cycle GO 28 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Andrew James Levan Radboud Universiteit Nijmegen Y CoI: Dr. Daniel Perley Liverpool John Moores University N CoI: Dr. Ashley Chrimes Radboud Universiteit Nijmegen N CoI: Dr. Daniele Bjorn Malesani Technical University of Denmark-DTU Space N CoI: Prof. Nial Rahil Tanvir University of Leicester N CoI: Dr. Benjamin Paul Gompertz The University of Warwick N CoI: Dr. Samantha Oates University of Birmingham N CoI: Dr. Elizabeth R. Stanway The University of Warwick N CoI: Dr. Andrew S. Fruchter Space Telescope Science Institute N CoI: Kornpob Bhirombhakdi Space Telescope Science Institute N CoI: Dr. Antonio de Ugarte Postigo Instituto de Astrofisica de Andalucia N (IAA) CoI: Prof. Jens Hjorth University of Copenhagen, Niels Bohr N Institute CoI: Prof. Johan P. U. Fynbo University of Copenhagen, Niels Bohr N Institute ------------------------------------------------------------------------------------ Abstract Long-duration gamma-ray bursts are associated with the collapse of massive stars, occurring ubiquitously in star-forming environments. These insights are based on studies of the more than 1000 bursts localised over the past 20 years. However, last year one burst, GRB 191019A, was discovered which appeared to challenge this rule. GRB 191019A is a regular long GRB coincident with the nucleus of an apparently passive galaxy at z=0.248. The probability of chance alignment within 0.1" of the galaxy nucleus is minimal (~10^-6), and so the association appears secure. There is no sign of any underlying supernova (SN) to limits >10 times fainter than typically in GRB supernovae. There is also no indication of nuclear SMBH activity in the galaxy (no X-ray detection to deep limits, or emission lines in the optical spectrum), and the source vanishes within a few hours, too quick for the expected evolution of tidal disruption events. This event may therefore represent a genuinely new route to the creation of a long GRB. Here we request deep UV observations to search for any underlying star formation to limits of <0.01 Msol/yr. The detection of even weak star formation would favour the origin in a massive star, in keeping with other GRBs. In this case, it is likely to provide evidence for the direct collapse of a massive star to a black hole. Alternatively, the absence of star formation may suggest a dynamical channel in the dense nuclear regions of the host galaxy. These HST observations are hence crucial in determining the origin of this new, and possibly so-far unidentified signal of stellar death. ------------------------------------------------------------------------------------ Observations Description ------------------------ 16458( 2) - 11-Nov-2020 15:04:49 - [ 2] We will obtain two orbits of observations of the host galaxy of GRB 191019A with WFC3 UVIS. One orbit will be on obtain in F225W and one in F275W. A standard 4 point dither pattern will be used. The source will be placed close to the corner of the chip to avoid mitigate for CTE, and the chip will be flashed to ~20 electrons. In practice, since the source is extended the CTE is less of a concern. ------------------------------------------------------------------------------------ 16458( 2) - 11-Nov-2020 15:04:49 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB191019A GALAXY, ELLIPTICAL, RA=22H40M5.8700S, J2000 V = 19 +/- 0.5 NUCLEUS DEC=-17D19'40.80" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 16458( 2) - 11-Nov-2020 15:04:49 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 16458( 2) - 11-Nov-2020 15:04:49 - [ 5] Visit: 01 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 GRB191019A WFC3/UVI ACCUM UVIS2 F225W FLASH=19 1 550 S POS TARG -55, -25; S (2200 S) PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ GRB191019A 1 WFC3/UVI ACCUM UVIS2 F225W 1 none none none 1 N/A S GRB191019A 1 WFC3/UVI ACCUM UVIS2 F225W 2 none none none 1 N/A S GRB191019A 1 WFC3/UVI ACCUM UVIS2 F225W 3 none none none 1 N/A S GRB191019A 1 WFC3/UVI ACCUM UVIS2 F225W 4 none none none 1 N/A S 16458( 2) - 11-Nov-2020 15:04:49 - [ 6] Visit: 02 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 GRB191019A WFC3/UVI ACCUM UVIS2 F275W FLASH=19 1 550 S POS TARG -55, -25; S (2200 S) PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ GRB191019A 1 WFC3/UVI ACCUM UVIS2 F275W 1 none none none 1 N/A S GRB191019A 1 WFC3/UVI ACCUM UVIS2 F275W 2 none none none 1 N/A S GRB191019A 1 WFC3/UVI ACCUM UVIS2 F275W 3 none none none 1 N/A S GRB191019A 1 WFC3/UVI ACCUM UVIS2 F275W 4 none none none 1 N/A S 16458( 2) - 11-Nov-2020 15:04:49 - [ 7] Summary Form for Proposal 16458 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=19 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1, POS TARG -55, -25 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F225W, F275W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GRB191019A ------------------------------------------------------------------------------------------------------------------------------------