12571( 2) - 11-Jul-2011 13:30:14 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12571 Version: 2 Check-in Time: 11-Jul-2011 13:30:14 STScI Edit Number: 0 Title The Crab Halo ------------------------------------------------------------------------------------ Type Cycle GO 19 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Peter Lundqvist Stockholm University CoI: Dr. Roger A. Chevalier The University of Virginia N CoI: Dr. Claes Fransson Stockholm University N CoI: Dr. Theodore R. Gull NASA Goddard Space Flight Center N CoI: Dr. George Sonneborn NASA Goddard Space Flight Center Y ------------------------------------------------------------------------------------ Abstract The Crab Nebula, along with its central pulsar and its explosive origin in SN 1054, plays a crucial role in our understanding of the link between supernovae and pulsar formation and activity. Yet, there are fundamental uncertainties in the nature of the event that have not been settled in more than two decades of investigation. The observed mass in the nebula and pulsar is nearly half of the expected initial stellar mass and the observed energy (much of which may come from the central pulsar) is only a few percent of the typical supernova energy. An attractive solution to this ``missing mass'' problem is that this mass is in a high velocity envelope around the observed Crab Nebula. The envelope would have most of the energy of the explosion (roughly 10^{51} ergs), bringing the energy up to that typical of a Type II supernova. The fact that the Crab filaments have a measured acceleration and show no deceleration at the outer edge is consistent with this hypothesis. The lack of an interaction region created by the fast shell can be attributed to a very low density around the supernova. We propose to search for the fast shell by taking a COS spectrum of the Crab pulsar in the region of the C IV 1550 line. We have carried out time-dependent ionization calculations that show that this line should produce a detectable broad, blueshifted absorption if the shell is present. ------------------------------------------------------------------------------------ Observations Description ------------------------ The Crab Nebula, along with its central pulsar and its explosive origin in SN 1054, plays a crucial role in our understanding of the link between supernovae and pulsar formation and activity. Yet, the observed mass in the nebula and pulsar is nearly half of the expected initial stellar mass and the observed energy (much of which may come from the central pulsar) is only a few percent of the typical supernova energy. This observing program searches for the fast, outer shell of the Crab Nebula by taking a COS G160M spectrum of the Crab pulsar in the region of the C IV 1550 line. The 1623 setting of G160M is used to increase the spectral coverage in the continuum on the red side of the C IV 12571( 2) - 11-Jul-2011 13:30:14 - [ 2] 1550 feature. The observation is being executed as two 3-orbit visits to maximize schedulability. In order to maximize exposure time while maintaining good data quality, each 3-orbit visit is executed as three exposures of 2546 sec, one each at FPPOS=2, 3, and 4. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 12571( 2) - 11-Jul-2011 13:30:14 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 M-1 STAR, PULSATING RA=05H34M31.9500S +/- 0.1", J2000 V = 17 +/- .1 VARIABLE DEC=+22D00'52.10" +/- 0.1" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database.This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 12571( 2) - 11-Jul-2011 13:30:14 - [ 4] Visit: 01 Visit Requirements: PCS MODE FINE 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 M-1 COS/FUV ACQ/PEA PSA G160M 1600 SEGMENT=BOTH 1 100 S KXD ------------------------------------------------------------------------------------------------------------------------------------ 2 M-1 COS/FUV ACQ/PEA PSA G160M 1600 SEGMENT=BOTH, NUM-POS=5, 1 100 S KD CENTER=FLUX-WT-FLR, STEP-SIZE=0.9 ------------------------------------------------------------------------------------------------------------------------------------ 3 M-1 COS/FUV TIME-TA PSA G160M 1623 BUFFER-TIME=6000, FP-POS=2 1 1930 S G ------------------------------------------------------------------------------------------------------------------------------------ 4 M-1 COS/FUV TIME-TA PSA G160M 1623 BUFFER-TIME=6000, FP-POS=2 1 616 S G ------------------------------------------------------------------------------------------------------------------------------------ 5 M-1 COS/FUV TIME-TA PSA G160M 1623 BUFFER-TIME=6000, FP-POS=3 1 2238 S G ------------------------------------------------------------------------------------------------------------------------------------ 6 M-1 COS/FUV TIME-TA PSA G160M 1623 BUFFER-TIME=6000, FP-POS=3 1 308 S G ------------------------------------------------------------------------------------------------------------------------------------ 7 M-1 COS/FUV TIME-TA PSA G160M 1623 BUFFER-TIME=6000, FP-POS=4 1 2546 S G ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ M-1 1 COS/FUV ACQ/PEA PSA G160M 1600 none none none none 1 N/A KXD M-1 2 COS/FUV ACQ/PEA PSA G160M 1600 none none none none 1 N/A KD M-1 3 COS/FUV TIME-TA PSA G160M 1623 none none none none 1 N/A G M-1 4 COS/FUV TIME-TA PSA G160M 1623 none none none none 2 N/A G M-1 5 COS/FUV TIME-TA PSA G160M 1623 none none none none 2 N/A G M-1 6 COS/FUV TIME-TA PSA G160M 1623 none none none none 3 N/A G M-1 7 COS/FUV TIME-TA PSA G160M 1623 none none none none 3 N/A G 12571( 2) - 11-Jul-2011 13:30:14 - [ 5] Visit: 02 Visit Requirements: PCS MODE FINE 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 M-1 COS/FUV ACQ/PEA PSA G160M 1600 SEGMENT=BOTH 1 100 S KXD ------------------------------------------------------------------------------------------------------------------------------------ 2 M-1 COS/FUV ACQ/PEA PSA G160M 1600 SEGMENT=BOTH, NUM-POS=5, 1 100 S KD CENTER=FLUX-WT-FLR, STEP-SIZE=0.9 ------------------------------------------------------------------------------------------------------------------------------------ 3 M-1 COS/FUV TIME-TA PSA G160M 1623 BUFFER-TIME=6000, FP-POS=2 1 1930 S G ------------------------------------------------------------------------------------------------------------------------------------ 4 M-1 COS/FUV TIME-TA PSA G160M 1623 BUFFER-TIME=6000, FP-POS=2 1 616 S G ------------------------------------------------------------------------------------------------------------------------------------ 5 M-1 COS/FUV TIME-TA PSA G160M 1623 BUFFER-TIME=6000, FP-POS=3 1 2238 S G ------------------------------------------------------------------------------------------------------------------------------------ 6 M-1 COS/FUV TIME-TA PSA G160M 1623 BUFFER-TIME=6000, FP-POS=3 1 308 S G ------------------------------------------------------------------------------------------------------------------------------------ 7 M-1 COS/FUV TIME-TA PSA G160M 1623 BUFFER-TIME=6000, FP-POS=4 1 2546 S G ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ M-1 1 COS/FUV ACQ/PEA PSA G160M 1600 none none none none 1 N/A KXD M-1 2 COS/FUV ACQ/PEA PSA G160M 1600 none none none none 1 N/A KD M-1 3 COS/FUV TIME-TA PSA G160M 1623 none none none none 1 N/A G M-1 4 COS/FUV TIME-TA PSA G160M 1623 none none none none 2 N/A G M-1 5 COS/FUV TIME-TA PSA G160M 1623 none none none none 2 N/A G M-1 6 COS/FUV TIME-TA PSA G160M 1623 none none none none 3 N/A G M-1 7 COS/FUV TIME-TA PSA G160M 1623 none none none none 3 N/A G 12571( 2) - 11-Jul-2011 13:30:14 - [ 6] Summary Form for Proposal 12571 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAKD, ACQ/PEAKXD, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=6000, CENTER=FLUX-WT-FLR, FP-POS=2, FP-POS=3, FP-POS=4, NUM-POS=5, SEGMENT=BOTH, STEP-SIZE=0.9 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G160M ------------------------------------------------------------------------------------------------------------------------------------ Target Names M-1 ------------------------------------------------------------------------------------------------------------------------------------