! Proposal 6718, submission 1 ! PI: Peter Lundqvist ! Received Thu Feb 15 11:39:53 EST 1996 ! From: jesper@astro.su.se Proposal_Information Title: The Missing Mass of the Crab Nebula Proposal_Category: GO Scientific_Category: INTERSTELLAR MEDIUM Cycle: 6 Investigators PI_name: Peter Lundqvist PI_Institution: Stockholm Observatory CoI_Name: Roger Chevalier CoI_Institution: University of Virginia CoI_Name: Robert Fesen CoI_Institution: Dartmouth College CoI_Name: Claes Fransson CoI_Institution: Stockholm Observatory CoI_Name: Jesper Sollerman CoI_Institution: Stockholm Observatory CoI_Name: George Sonneborn CoI_Institution: Goddard Space Flight Center Abstract: ! Free format text (please update) 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 less than half of the expected initial stellar mass and the observed energy is only a few percent of the typical supernova energy. Resting on the assumption that the ``missing mass'' is in a high velocity envelope around the observed nebula, we propose to search for this fast shell by taking an FOS spectrum of the Crab pulsar in the region of the C IV Lambda1550 line. According to time-dependent ionization calculations this line should produce a detectable broad, blueshifted absorption if the shell is present. Our spectrum will also narrow significantly the gap of the pulsar spectrum between the optical/UV and X-ray range. Questions ! Free format text (please update) Observing_Description: To search for the C IV absorption line, expected to be of width ~ 5000 km/s, we will use the FOS/BL G130H disperser. (G160L is more sensitive but has flat-field problems around 1550 Angstrom.) To reach an optical depth of 0.1 at 3 Sigma for the predicted absorption line a S/N = 15 is required. At 1240 Angstrom we estimate a S/N = 8 for the continuum. The pulsar continuum is therefore expected to be traced with good signal-to-noise over the full range of the FOS. We will use the 1.0 aperture to maximize the signal throughput. Initial target acquistion using a four stage ACQ/PEAK is broken up into A+B1+C1+F1 target acquisition pointing patterns. This can be done during the first orbit. In the remaining five (5) orbits, we can then observe the target for a total of 12,100 seconds. Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: CRAB-PULSAR Alternate_Names: PSR0531+21 Description: STAR,PULSAR Position: RA=05H 31M 31.47S +/- 0.02S, DEC=+21D 58' 55.4" +/- 0.1", PLATE-ID=000M Equinox: 1950.0 RA_PM: Dec_PM: Epoch: Flux: V=16.4 +/- 0.3 B-V=0.5 ! Include at least V and B-V Comments: Visits ! Section 6 Visit_Number: 1 Visit_Requirements: ! Section 7.1 Exposure_Number: 1 ! Section 6.5 Target_Name: CRAB-PULSAR Config: FOS/BL Opmode: ACQ/PEAK Aperture: 4.3 Sp_Element: MIRROR Wavelength: Optional_Parameters: SEARCH-SIZE-X=1, SEARCH-SIZE-Y=3 SCAN-STEP-Y=1.204 Number_of_Iterations: 1 Time_Per_Exposure: 5.0S Special_Requirements: ! Section 7.2 ONBOARD ACQ FOR 2 Comments: 1 OF 4 STAGES FOR ACQ/PEAK TARGET ACQUISITION A+B1+C1+F1 SEQUENCE Exposure_Number: 2 ! Section 6.5 Target_Name: CRAB-PULSAR Config: FOS/BL Opmode: ACQ/PEAK Aperture: 1.0 Sp_Element: MIRROR Wavelength: Optional_Parameters: SEARCH-SIZE-X=6, SEARCH-SIZE-Y=2 SCAN-STEP-X=0.602, SCAN-STEP-Y=0.602 Number_of_Iterations: 1 Time_Per_Exposure: 7.5S Special_Requirements: ! Section 7.2 ONBOARD ACQ FOR 3 Exposure_Number: 3 ! Section 6.5 Target_Name: CRAB-PULSAR Config: FOS/BL Opmode: ACQ/PEAK Aperture: 0.5 Sp_Element: MIRROR Wavelength: Optional_Parameters: SEARCH-SIZE-X=3, SEARCH-SIZE-Y=3 SCAN-STEP-X=0.29, SCAN-STEP-Y=0.29 Number_of_Iterations: 1 Time_Per_Exposure: 9S Special_Requirements: ! Section 7.2 ONBOARD ACQ FOR 4 Exposure_Number: 4 Target_Name: CRAB-PULSAR Config: FOS/BL Opmode: ACQ/PEAK Aperture: 0.3 Sp_Element: MIRROR Wavelength: Optional_Parameters: SEARCH-SIZE-X=3, SEARCH-SIZE-Y=3 SCAN-STEP-X=0.17, SCAN-STEP-Y=0.17 Number_of_Iterations: 1 Time_Per_Exposure: 15S Special_Requirements: ! Section 7.2 ONBOARD ACQ FOR 5 Exposure_Number: 5 ! Section 6.5 Target_Name: CRAB-PULSAR Config: FOS/BL Opmode: ACCUM Aperture: 1.0 Sp_Element: G130H Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 12100S Special_Requirements: ! Section 7.2 Data_Distribution ! Defaults indicated; change if desired Medium: 8MM ! 8MM or 6250BPI or 1600BPI Blocking_Factor: 10 ! 10 or 1 ! 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