12438( 3) - 10-Jan-2011 00:05:37 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12438 Version: 3 Check-in Time: 10-Jan-2011 00:05:37 STScI Edit Number: 0 Title HST observations of the exceptional Christmas-day gamma-ray burst ------------------------------------------------------------------------------------ Type Cycle GO/DD 18 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Nial R. Tanvir University of Leicester CoI: Dr. Johan P. U. Fynbo University of Copenhagen, Niels Bohr N Institute CoI: Dr. Andrew J. Levan The University of Warwick N CoI: Prof. Jens Hjorth University of Copenhagen, Niels Bohr N Institute CoI: Dr. Daniele Malesani University of Copenhagen, Niels Bohr N Institute CoI: Dr. Dong Xu Weizmann Institute of Science N CoI: Dr. Phillip A. Evans University of Leicester N CoI: Dr. Klaas Wiersema University of Leicester N CoI: Dr. Avishay Gal-Yam Weizmann Institute of Science N CoI: Dr. David Bersier Liverpool John Moores University N ------------------------------------------------------------------------------------ Abstract On Christmas day 2010, Swift detected one of the most unusual gamma-ray bursts (GRBs) ever seen. It apparently persisted for well over 1000s, had an extremely bright, and long lived X-ray afterglow, followed by a remarkably rapid decay, and exhibited an even longer slow decline in its (very blue) optical lightcurve. Recent observations establish a spectroscopic redshift z=0.4, and so GRB 101225 is not a member of the low-luminosity (and hence low-redshift) class as had been suggested. This leads to the natural question of what can produce such an event? Is this a classical GRB from core collapse or an phenomena involving a galactic nucleus (its early lightcurve and optical spectral were reminscent of Blazars)? Could it be an unusual progenitor in a low density medium (e.g. stellar halo), or a chemically extremely unusual system (e.g. ultra-low metallicity). Our proposed HST observations will help to directly address these questions. We will i) track the light curve to late times, directly measuring the total energy of the explosions, and searching for any evidence of an associated supernova - a supernova comparable to those seen in many long-GRBs is already ruled out by the ground data, but is of course the key to definitely associating this burst with a core-collapse event; ii) precisely position the afterglow on its host galaxy using the invariant PSF of HST to obtain positions much more accurately than is possible from the ground, this will allow us to ascertain if the burst is coincident with the galactic nucleus with far greater confidence and relate the burst to any star-forming regions; iii) characterize the nature of the host galaxy in comparison with those of other GRBs, and hence provide critical clues to the nature of the progenitor. ------------------------------------------------------------------------------------ Observations Description ------------------------ The aim of this proposal is to obtain HST observations of GRB 101225A utilizing 12438( 3) - 10-Jan-2011 00:05:37 - [ 2] ACS in B and V. We will use observations in F435W and F606W and a three point dither (#13 from ISR 2001-07) to give us a total of 1020s and 880s in each filter respectively. We have shortened the first F606W exposure to avoid issues of buffer dumps within the single orbit observations, while the dither will allow us to remove cosmic rays and ensure against bad pixels etc. We have included a modest range of orient constraints to avoid diffraction spikes from a nearby bright star (R~19), although in practice these are not close to the available orients for the visit. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 12438( 3) - 10-Jan-2011 00:05:37 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB101225A UNIDENTIFIED, ACCRETION RA=00H00M47.4800S +/- 1", J2000 V = 25 +/- 1 DISK, X-RAY EMITTER DEC=+44D36'1.00" +/- 1" Reference Frame: Other: Swift ------------------------------------------------------------------------------------------------------------------------------------ 12438( 3) - 10-Jan-2011 00:05:37 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.138 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 32.99 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 12438( 3) - 10-Jan-2011 00:05:37 - [ 5] Visit: 01 Visit Requirements: ORIENT 325D TO 35 D; ORIENT 55D TO 125 D; ORIENT 145D TO 215 D; ORIENT 235D TO 305 D 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GRB101225A ACS/WFC ACCUM WFC1 F606W 1 1150 S PATTERN 1 1 see below ------------------------------------------------------------------------------------------------------------------------------------ 2 GRB101225A ACS/WFC ACCUM WFC1 F435W 1 1150 S PATTERN 1 2 see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ GRB101225A 1 ACS/WFC ACCUM WFC1 F606W 1 none none none 1 200 S GRB101225A 1 ACS/WFC ACCUM WFC1 F606W 2 none none none 1 340 S GRB101225A 1 ACS/WFC ACCUM WFC1 F606W 3 none none none 1 340 S GRB101225A 2 ACS/WFC ACCUM WFC1 F435W 1 none none none 1 340 S GRB101225A 2 ACS/WFC ACCUM WFC1 F435W 2 none none none 1 340 S GRB101225A 2 ACS/WFC ACCUM WFC1 F435W 3 none none none 1 340 S 12438( 3) - 10-Jan-2011 00:05:37 - [ 6] Summary Form for Proposal 12438 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 145D TO 215 D, ORIENT 235D TO 305 D, ORIENT 325D TO 35 D, ORIENT 55D TO 125 D, PATTERN 1 1, PATTERN 1 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F435W, F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GRB101225A ------------------------------------------------------------------------------------------------------------------------------------