13196( 2) - 25-Mar-2013 14:38:10 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13196 Version: 2 Check-in Time: 25-Mar-2013 14:38:10 STScI Edit Number: 0 Title The dynamical aftermath of a major gamma-ray flare from the Crab nebula ------------------------------------------------------------------------------------ Type Cycle GO/DD 20 ------------------------------------------------------------------------------------ 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 Mullard Space Science Laboratory N 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. Rolf Buehler Stanford University 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. With the aim of locating the site(s) of the flares, we have organized a multiwavelength program, including a regular monitoring of the source both in X-ray and optical through a joint Chandra-HST project, coupled to pre-planned ToOs with both telescopes in order to react promptly in case of a new brightening in gamma rays. We could take advantage of our program, activating the HST ToO at the onset of a new flare on March 4, 2013. Comparing this ToO observation with a recent monitoring observation allowed us to spot a peculiar, active region, possibly associated to the flaring gamma-ray activity. We ask here for a new HST/ACS observation to be performed on March 25-30, i.e. about 20 days after the flare and 20 days before the next planned observation of our monitoring program (scheduled on April 18, just before the end of the visibility window of the target). Such a sequence of observations will allow us to search for the expected dynamical aftermath of the flare, yielding a crucial piece of information about the location of the flaring site. ------------------------------------------------------------------------------------ Observations Description ------------------------ We ask to observe the Crab pulsar and nebula system to search for surface brightness changes in the inner nebula possibly associated to the dynamical aftermath of a large gamma-ray flare. We will use the same setup we adopted in our ongoing HST monitoring campaign of the Crab, as well as in our recent HST pre-planned ToO. We will use the ACS/WFC with the WFC1 aperture, 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. A box dithering pattern will be implemented to fill the inter-chip gap as well 13196( 2) - 25-Mar-2013 14:38:10 - [ 2] 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 new image will be compared to the one collected in our ToO (performed on March 6, when the flare was ongoing) as well as to the most recent pre-flare image (collected on February 24), as well as to the next observation of our monitoring program, planned for April 18. Such a multi-epoch dataset, thanks to the superb angular resolution of HST, will allow to perform a definitive search for the expected variability related to the aftermath of a gamma-ray flare. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 13196( 2) - 25-Mar-2013 14:38:10 - [ 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 PULSAR DEC=+22D00'52.10" +/- 0.1" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 13196( 2) - 25-Mar-2013 14:38:10 - [ 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 Pattern_Comments: Dithering is aimed at filling the inter-chip gap as well as to rejecting CR hits ------------------------------------------------------------------------------------------------------------------------------------ 13196( 2) - 25-Mar-2013 14:38:10 - [ 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CRAB ACS/WFC ACCUM WFC1 F550M 1 500 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 | ------------------------------------------------------------------------------------------------------------------------------------ CRAB 1 ACS/WFC ACCUM WFC1 F550M 1 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC1 F550M 2 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC1 F550M 3 none none none 1 N/A CRAB 1 ACS/WFC ACCUM WFC1 F550M 4 none none none 1 N/A 13196( 2) - 25-Mar-2013 14:38:10 - [ 6] Summary Form for Proposal 13196 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F550M ------------------------------------------------------------------------------------------------------------------------------------ Target Names CRAB ------------------------------------------------------------------------------------------------------------------------------------