! Proposal 6765, submission 1 ! PI: Gordon MacAlpine ! Received Fri Feb 16 15:34:05 EST 1996 ! From: gmm@astro.lsa.umich.edu ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template Proposal_Information Title: A Test For Products of Oxygen Burning in the Crab Nebula Proposal_Category: GO Scientific_Category: INTERSTELLAR MEDIUM Cycle: 6 Investigators PI_name: Gordon MacAlpine PI_Institution: University of Michigan CoI_Name: William Blair CoI_Institution: The Johns Hopkins University Contact: N CoI_Name: Kris Davidson CoI_Institution: University of Minnesota Contact: N CoI_Name: Robert Fesen CoI_Institution: Dartmouth College Contact: N CoI_Name: Richard Henry CoI_Institution: University of Oklahoma Contact: N CoI_Name: Stephen Lawrence CoI_Institution: Universidad Autonoma Nacional de Mexico Contact: N CoI_Name: Alan Uomoto CoI_Institution: The Johns Hopkins University Contact: N Abstract: Young supernova remnants are excellent laboratories for investigating how stars make elements, and the Crab Nebula can provide unique information about the supernova process and associated heavy element production. Existing evidence indicates that the progenitor star initially contained 9-11 solar masses, at the interface between degenerate and nondegenerate core evolution. Some calculations suggest that oxygen burning does not take place in such stars, whereas other models support off-center ignition of oxygen. It is important to determine how far the nuclear reactions progressed and to know whether the nebular gas is significantly contaminated by products of oxygen burning, such as Si and S. In conjunction with an optical and theoretical investigation of regions showing unusually strong S II LambdaLambda6716,6731 lines, we propose a simple, robust test to distinguish whether this emission is a result of filament optical depth characteristics or of significantly increased S abundance. In the former case, the intensities of the S II lines and Mg II Lambda2798 would be directly correlated, whereas they would be strongly anticorrelated if products of oxygen burning are significantly enhanced in the nebula. Questions Observing_Description: We propose to use the FOS for measuring the Mg II Lambda2798 emission at two positions in the Crab Nebula. The targets are to be acquired by offsetting, using WMstar17 (V = 15.2, B-V = 0.8, offset of 44 arcsec) for position NGC1952-LS.SPOT (Low Sulfur emission) and using WMstar18 (V = 16.4, B-V = 1.3, offset of 20 arcsec) for position NGC1952-HS.SPOT (High Sulfur emission). The WMstars are defined in Wyckoff and Murray (1977, MNRAS, 180, 717). The appropriate grating is G270H with the RD camera for the above measurements. In addition, we also plan relatively short exposures with G400H/RD to provide overlap with the ground-based optical spectra which we already have. The appropriate aperture for these observations is the 0.9" circle, which corresponds with the slit widths used for optical observations and which provides the spatial resolution necessary to isolate and analyze lines from one identifiable filament. As noted in the proposal Scientific Justification, we have measured optical line intensities and we have run a series of detailed photoionization model calculations to predict Mg II Lambda2798 fluxes for all plausible situations, taking into account effects of reddening and possible depletion of refractory elements onto grains. Then we determined exposure times as necessary to be able to answer the primary question of whether or not the Crab Nebula contains significant amounts of oxygen-burning products. Real_Time_Justification: None. We have used the Hiltner 2.4 m telescope at the Michigan- Dartmouth-MIT Observatory to obtain optical spectra and to select our proposed target positions. We are currently developing improved photoionization modelling analyses for the Crab Nebula using spectroscopic and imaging data obtained with HST for projects GO 5676 and GO 5354. Those data do not provide the information needed for the test described above. Calibration_Justification: Additional_Comments: Fixed_Targets Target_Number: 1 Target_Name: STAR-053433+220230-OFFSET Alternate_Names: GSC1309-3330, WM17 Description: STAR, UNDESIGNATED Position: RA = 5H 34M 33.55S +/- 0.01S, DEC = +22D 2' 30.0" +/- 0.15", PLATE-ID = 000M Equinox: J2000 Epoch: 1983.02 Flux: V = 15.2 +/- 0.3, B-V = 0.8 +/- 0.3 Comments: THIS IS STAR 17 OF WYCKOFF AND MURRAY 1977, MNRAS, 180, 717. MAGNITUDE AND COLOR ARE ESTIMATES FROM CCD IMAGES. Target_Number: 2 Target_Name: NGC1952-LS.SPOT Alternate_Names: CRAB-NEBULA-LS.SPOT Description: ISM, SNR, EJECTA Position: RA-OFF = -0.66S +/- 0.01S, DEC-OFF = -43.0" +/- 0.15", FROM 1 Equinox: J2000 Epoch: 1995.02 Flux: SURF(V) = 20.0 +/- 1.0 E(B-V) = 0.47 +/- 0.03 F-LINE(2800) = 2 +/- 1 E-16 W-LINE(2800) = 1.0 +/- 0.5 F-LINE(4340) = 5 +/- 1 E-16 W-LINE(4340) = 1.0 +/- 0.5 Comments: SPOT IN THE CRAB NEBULA WITH VERY LOW OPTICAL SII EMISSION. SURFACE V BRIGHTNESS IS A GUESS BASED ON CCD IMAGES. MGII LAMBDA2800 LINE FLUX IS LOWER LIMIT BASED ON OPTICAL SPECTROSCOPY AND PHOTOIONIZATION MODELS, TAKING INTO ACCOUNT REDDENING AND POSSIBLE DEPLETION ON GRAINS. Target_Number: 3 Target_Name: STAR-053433+215951-OFFSET Alternate_Names: WM18 Description: STAR, UNDESIGNATED Position: RA = 5H 34M 33.07S +/- 0.01S, DEC = +21D 59' 51.8" +/- 0.15", PLATE-ID = 000M Equinox: J2000 Epoch: 1983.02 Flux: V = 16.4 +/- 0.2, B-V = 1.3 +/- 0.2 Comments: THIS IS STAR 18 OF WYCKOFF AND MURRAY 1977, MNRAS, 180, 717. MAGNITUDE AND COLOR ARE ESTIMATES BASED ON CCD IMAGES. Target_Number: 4 Target_Name: NGC1952-HS.SPOT Alternate_Names: CRAB-NEBULA-HS.SPOT Description: ISM, SNR, EJECTA Position: RA-OFF = +1.20S +/- 0.01S, DEC-OFF = +8.9" +/- 0.15", FROM 3 Equinox: J2000 Epoch: 1995.02 Flux: SURF(V) = 20.0 +/- 1.0 E(B-V) = 0.47 +/- 0.03 F-LINE(2800) = 5 +/- 3 E-17 W-LINE(2800) = 1.0 +/- 0.5 F-LINE(4340) = 4 +/- 1 E-16 W-LINE(4340) = 1.0 +/- 0.5 Comments: SPOT IN THE CRAB NEBULA WITH VERY HIGH OPTICAL SII EMISSION. SURFACE V BRIGHTNESS IS A GUESS BASED ON CCD IMAGES. MGII LAMBDA2800 LINE FLUX IS LOWER LIMIT BASED ON OPTICAL SPECTROSCOPY AND PHOTOIONIZATION MODELS, TAKING INTO ACCOUNT REDDENING AND POSSIBLE DEPLETION ON GRAINS. Visits Visit_Number: 01 Visit_Requirements: On_Hold_Comments: Visit_Comments: Exposure_Number: 1 Target_Name: STAR-053433+220230-OFFSET Config: FOS/RD Opmode: ACQ/BINARY Aperture: 4.3 Sp_Element: MIRROR Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 6.0S Special_Requirements: ONBOARD ACQ FOR 2 Comments: ACQUISITION PATTERN NAME Z. EXPOSURE TIME IS FOR UPPER LIMIT TO V AND B-V ESTIMATES. Exposure_Number: 2 Target_Name: STAR-053433+220230-OFFSET Config: FOS/RD Opmode: ACQ/PEAK Aperture: 0.3 Sp_Element: G400H Wavelength: Optional_Parameters: SCAN-STEP-Y=0.17, SCAN-STEP-X=0.17, SEARCH-SIZE-Y=4, SEARCH-SIZE-X=4 Number_of_Iterations: 1 Time_Per_Exposure: 4.0S Special_Requirements: ONBOARD ACQ FOR 3-6 Comments: ACQUISITION PATTERN NAME E1. EXPOSURE TIME IS FOR UPPER LIMIT TO V AND B-V ESTIMATES. Exposure_Number: 3 Target_Name: NGC1952-LS.SPOT Config: FOS/RD Opmode: ACCUM Aperture: 1.0 Sp_Element: G400H Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 13M Special_Requirements: Comments: EXPOSURE TIME TO GIVE S/N OF ROUGHLY 12 IN 4340 LINE, TAKING INTO ACCOUNT FWHM = 2.23 DIODES FOR EXTENDED SOURCE. Exposure_Number: 4 Target_Name: NGC1952-LS.SPOT Config: FOS/RD Opmode: ACCUM Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 40M Special_Requirements: Comments: TOTAL OF EXPOSURE TIMES IN EXPOSURES 4, 5, AND 6 WILL PROVIDE S/N OF ROUGHLY 16 IN THE 2800 LINE IF MODEL ASSUMPTIONS ARE CORRECT, TAKING INTO ACCOUNT FWHM = 2.23 DIODES FOR EXTENDED SOURCE. Exposure_Number: 5 Target_Name: NGC1952-LS.SPOT Config: FOS/RD Opmode: ACCUM Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 40M Special_Requirements: Exposure_Number: 6 Target_Name: NGC1952-LS.SPOT Config: FOS/RD Opmode: ACCUM Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 40M Special_Requirements: Visits Visit_Number: 02 Visit_Requirements: On_Hold_Comments: Visit_Comments: Exposure_Number: 7 Target_Name: STAR-053433+215951-OFFSET Config: FOS/RD Opmode: ACQ/BINARY Aperture: 4.3 Sp_Element: MIRROR Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 19S Special_Requirements: ONBOARD ACQ FOR 8 Comments: ACQUISITION PATTERN NAME Z. EXPOSURE TIME ALLOWS FOR HIGHER THAN NOMINAL V AND B-V. Exposure_Number: 8 Target_Name: STAR-053433+215951-OFFSET Config: FOS/RD Opmode: ACQ/PEAK Aperture: 0.3 Sp_Element: G400H Wavelength: Optional_Parameters: SCAN-STEP-Y=0.17, SCAN-STEP-X=0.17, SEARCH-SIZE-Y=4, SEARCH-SIZE-X=4 Number_of_Iterations: 1 Time_Per_Exposure: 14S Special_Requirements: ONBOARD ACQ FOR 9-14 Comments: ACQUISITION PATTERN NAME E1. EXPOSURE TIME ALLOWS FOR HIGHER THAN NOMINAL V AND B-V. Exposure_Number: 9 Target_Name: NGC1952-HS.SPOT Config: FOS/RD Opmode: ACCUM Aperture: 1.0 Sp_Element: G400H Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 10M Special_Requirements: Comments: EXPOSURE TIME TO GIVE S/N OF ROUGHLY 9 IN 4340 LINE, TAKING INTO ACCOUNT FWHM = 2.23 DIODES FOR EXTENDED SOURCE. Exposure_Number: 10 Target_Name: NGC1952-HS.SPOT Config: FOS/RD Opmode: ACCUM Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 40M Special_Requirements: Comments: TOTAL OF EXPOSURE TIMES IN EXPOSURES 10 THROUGH 14 WILL PROVIDE S/N OF ROUGHLY 8 IN THE 2800 LINE IF MODEL ASSUMPTIONS ARE CORRECT, TAKING INTO ACCOUNT FWHM = 2.23 DIODES FOR EXTENDED SOURCE. Exposure_Number: 11 Target_Name: NGC1952-HS.SPOT Config: FOS/RD Opmode: ACCUM Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 40M Special_Requirements: Exposure_Number: 12 Target_Name: NGC1952-HS.SPOT Config: FOS/RD Opmode: ACCUM Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 40M Special_Requirements: Exposure_Number: 13 Target_Name: NGC1952-HS.SPOT Config: FOS/RD Opmode: ACCUM Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 40M Special_Requirements: Exposure_Number: 14 Target_Name: NGC1952-HS.SPOT Config: FOS/RD Opmode: ACCUM Aperture: 1.0 Sp_Element: G270H Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 40M Special_Requirements: Data_Distribution ! Defaults indicated; change if desired Medium: 8MM ! 8MM or 6250BPI or 1600BPI Blocking_Factor: 10 ! 10 or 1 ! Only astronomers with very old 9- ! track tape drives should consider ! a blocking factor of 1 Ship_To: PI_Address ! STSCI or PI_Address or ! PI Address from Phase I is: ! ! Department of Astronomy ! University of Michigan ! Ann Arbor, MI ! 48109-1090 ! ! Ship_Via: UPS ! UPS (2-day) or OVERNIGHT ! Overnight shipping done at PI expense Recipient_Email: ! Needed if Ship_To: is not PI_Address !