13751( 3) - 05-Sep-2014 13:23:52 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13751 Version: 3 Check-in Time: 05-Sep-2014 13:23:52 STScI Edit Number: 1 Title Imaging the Crab nebula when it is flaring in gamma-rays ------------------------------------------------------------------------------------ Type Cycle GO 22 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Andrea De Luca INAF, Instituto di Astrofisica Spaziale e Y Fisica CoI: Dr. Patrizia A. Caraveo INAF, Instituto di Astrofisica Spaziale e N Fisica CoI: Prof. Giovanni F. Bignami Instituto Universitario de Studi Superiori N Pavia CoI: Dr. Marco Tavani INAF, Instituto di Astrofisica Spaziale e N Fisica CoI: Dr. Roberto Mignani INAF, Instituto di Astrofisica Spaziale e N Fisica CoI: Dr. Martin C. Weisskopf NASA Marshall Space Flight Center N CoI: Dr. Stefan Funk Stanford University N CoI: Dr. Andrea Belfiore University of California - Santa Cruz N CoI: Dr. Claire Ellen Max Lawrence Livermore National Laboratory N CoI: Prof. Dieter Horns Deutsches Elektronen Synchrotron N CoI: Dr. Rolf Buehler Deutsches Elektronen Synchrotron N CoI: Dr. Jeff Kolodziejczak NASA Marshall Space Flight Center N CoI: Prof. Roger D. Blandford Stanford University N CoI: Prof. Roger Romani Stanford University N CoI: Prof. Jonathan Arons University of California - Berkeley N ------------------------------------------------------------------------------------ Abstract One of the most intriguing results of the gamma-ray instruments currently in orbit has been the detection of powerful flares from the Crab Nebula. Such events, with a recurrence time of about once per year, can be so dramatic to make the system the brightest source in the gamma-ray sky, as it occurred in April 2011. Such a discovery challenges our understanding of how pulsar wind nebulae work and defies current astrophysical models for particle acceleration. With the aim of locating the site(s) of the flares, an ad hoc HST strategy have been put in place to be prepared and react promptly in case of a new brightening in gamma rays. We ask here for a triggered TOO observation of the Crab Nebula with ACS/WFC in case a gamma-ray flare is announced by the Agile and/or the Fermi missions. This TOO is crucial part of a multiwavelength program that we have organized, based on lessons learnt from our follow-up observations of previous flares, including a regular (quarterly) monitoring of the source both in X-rays and optical through a joint Chandra-HST proposal. ------------------------------------------------------------------------------------ Observations Description ------------------------ We ask to perform four-epoch imaging of the Crab Pulsar and Nebula, reacting with the fastest possible response time to a trigger provided by the detection 13751( 3) - 05-Sep-2014 13:23:52 - [ 2] of a new gamma-ray flare from the Crab by Fermi-LAT and/or AGILE. The first-epoch observation should be performed as soon as possible after the trigger, the second-epoch observation one week after the first observation, the third one week after the second and the fourth one week after the third. We will use the HST/ACS instrument in its WFC configuration, with the large-band F550M filter, well suited to sample the continuum emission from the system, with almost no contamination from line emission from the SNR filaments. For each epoch, a box dithering pattern will be implemented to fill the inter-chip gap as well as to reject cosmic ray hits. Setting an exposure of 500 s for each position of the dithering pattern results in 2000 s exposure time per visit, which is well suited to achieve our goals and allows for an optimal use of the orbital visibility window. The images collected under this ToO will be completed and compared with images acquired with an identical instrument setup by the quarterly HST monitoring campaign that we have successfully proposed as a joint Chandra-HST program. ------------------------------------------------------------------------------------ 13751( 3) - 05-Sep-2014 13:23:52 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 CRAB STAR, NEUTRON STAR, RA=05H34M31.9500S +/- 0.1", J2000 V = 16.5 +/- 0.1 PULSAR DEC=+22D00'52.10" +/- 0.1" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 13751( 3) - 05-Sep-2014 13:23:52 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 3.5 Line_Spacing 0.5 Coordinate_Frame POS-TARG Pattern_Orient 85.28 Angle_Between_Sides 85.28 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 13751( 3) - 05-Sep-2014 13:23:52 - [ 5] Visit: 01 Visit Requirements: SCHED 80%; ON HOLD ; TOO RESPONSE TIME 1.0D On Hold Comments: This is a target of opportunity observation. The trigger will be provided by the detection of a new gamma-ray flare from the Crab nebula by Fermi-LAT and/or AGILE. 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 CRAB ACS/WFC ACCUM WFC F550M 1 500 S PATTERN 1 1 (2000 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 | ------------------------------------------------------------------------------------------------------------------------------------ CRAB 1 ACS/WFC ACCUM WFC F550M 1 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC F550M 2 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC F550M 3 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC F550M 4 none none none 1 N/A 13751( 3) - 05-Sep-2014 13:23:52 - [ 6] Visit: 02 Visit Requirements: SCHED 80%; AFTER 01 BY 7 D TO 8 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CRAB ACS/WFC ACCUM WFC F550M 1 500 S PATTERN 1 1 (2000 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 | ------------------------------------------------------------------------------------------------------------------------------------ CRAB 1 ACS/WFC ACCUM WFC F550M 1 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC F550M 2 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC F550M 3 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC F550M 4 none none none 1 N/A 13751( 3) - 05-Sep-2014 13:23:52 - [ 7] Visit: 03 Visit Requirements: SCHED 80%; AFTER 02 BY 7 D TO 8 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CRAB ACS/WFC ACCUM WFC F550M 1 500 S PATTERN 1 1 (2000 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 | ------------------------------------------------------------------------------------------------------------------------------------ CRAB 1 ACS/WFC ACCUM WFC F550M 1 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC F550M 2 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC F550M 3 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC F550M 4 none none none 1 N/A 13751( 3) - 05-Sep-2014 13:23:52 - [ 8] Visit: 04 Visit Requirements: SCHED 80% 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 CRAB ACS/WFC ACCUM WFC F550M 1 500 S PATTERN 1 1 (2000 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 | ------------------------------------------------------------------------------------------------------------------------------------ CRAB 1 ACS/WFC ACCUM WFC F550M 1 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC F550M 2 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC F550M 3 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC F550M 4 none none none 1 N/A 13751( 3) - 05-Sep-2014 13:23:52 - [ 9] Summary Form for Proposal 13751 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 7 D TO 8 D, AFTER 02 BY 7 D TO 8 D, ON HOLD , PATTERN 1 1, SCHED 80%, TOO RESPONSE TIME 1.0D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F550M ------------------------------------------------------------------------------------------------------------------------------------ Target Names CRAB ------------------------------------------------------------------------------------------------------------------------------------