6765( 4) - 11/13/96 10:50 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6765 Version: 4 Check-in Date: 13-Nov-1996 10:46:26 1.Proposal Title: A Test For Products of Oxygen Burning in the Crab Nebula ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle INTERSTELLAR MEDIUM GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: GORDON MACALPINE UNIV. OF MICHIGAN CoI: Stephen Lawrence Universidad Autonoma Nacional de Mexico N CoI: Alan Uomoto The Johns Hopkins University N CoI: William Blair The Johns Hopkins University N CoI: Kris Davidson University of Minnesota N CoI: Robert Fesen Dartmouth College N CoI: Richard Henry University of Oklahoma N ------------------------------------------------------------------------------------ 6. 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. ------------------------------------------------------------------------------------ Observations 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 ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6765( 4) - 11/13/96 10:50 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 STAR- STAR, UNDESIGNATED RA = 5H 34M 33.55S +/- 0.01S, J2000 V = 15.2+/-0.3 053433+22023 DEC = +22D 2' 30.0" +/- 0.15", B-V = 0.8+/-0.3 0-OFFSET PLATE-ID = 000M Comments: THIS IS STAR 17 OF WYCKOFF AND MURRAY 1977, MNRAS, 180, 717. MAGNITUDE AND COLOR ARE ESTIMATES FROM CCD IMAGES. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1983.02 0.0 0.0 0.0 2 NGC1952- ISM, SNR, EJECTA RA-OFF = -0.66S +/- 0.01S, DEC- J2000 SURF(V) = 20.0+/-1.0 LS.SPOT OFF = -43.0" +/- 0.15", FROM 1 E(B-V) = 0.47+/-0.03 F-LINE(2800)=2+/-1e-16 W-LINE(2800)=1.0+/-0.5 F-LINE(4340)=5+/-1e-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. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1995.02 0.0 0.0 0.0 3 STAR- STAR, UNDESIGNATED RA = 5H 34M 33.07S +/- 0.01S, J2000 V = 16.4+/-0.2 053433+21595 DEC = +21D 59' 51.8" +/- 0.15", B-V = 1.3+/-0.2 1-OFFSET PLATE-ID = 000M Comments: THIS IS STAR 18 OF WYCKOFF AND MURRAY 1977, MNRAS, 180, 717. MAGNITUDE AND COLOR ARE ESTIMATES BASED ON CCD IMAGES. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1983.02 0.0 0.0 0.0 4 NGC1952- ISM, SNR, EJECTA RA-OFF = +1.20S +/- 0.01S, DEC- J2000 SURF(V) = 20.0+/-1.0 HS.SPOT OFF = +8.9" +/- 0.15", FROM 3 E(B-V) = 0.47+/-0.03 F-LINE(2800)=5+/-3e-17 W-LINE(2800)=1.0+/-0.5 F-LINE(4340)=4+/-1e-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. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1995.02 0.0 0.0 0.0 6765( 4) - 11/13/96 10:50 - [ 2] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 STAR-053433 FOS/RD ACQ/BIN 4.3 MIRROR 1 6.0 S ONBOARD ACQ FOR 2 +220230-OFF ARY SET Comments: ACQUISITION PATTERN NAME Z. EXPOSURE TIME IS FOR UPPER LIMIT TO V AND B-V ESTIMATES. ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR-053433 FOS/RD ACQ/PEA 0.3 G400H SCAN-STEP-Y=0.17,SCAN-STEP-X=0.17 1 4.0 S ONBOARD ACQ FOR 3-6 +220230-OFF K ,SEARCH-SIZE-Y=4,SEARCH-SIZE-X=4 SET Comments: ACQUISITION PATTERN NAME E1. EXPOSURE TIME IS FOR UPPER LIMIT TO V AND B-V ESTIMATES. ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC1952-LS. FOS/RD ACCUM 1.0 G400H 1 13 M SPOT Comments: EXPOSURE TIME TO GIVE S/N OF ROUGHLY 12 IN 4340 LINE, TAKING INTO ACCOUNT FWHM = 2.23 DIODES FOR EXTENDED SOURCE. ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC1952-LS. FOS/RD ACCUM 1.0 G270H 1 40 M SPOT 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. ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC1952-LS. FOS/RD ACCUM 1.0 G270H 1 40 M SPOT ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC1952-LS. FOS/RD ACCUM 1.0 G270H 1 40 M SPOT ------------------------------------------------------------------------------------------------------------------------------------ 6765( 4) - 11/13/96 10:50 - [ 3] Visit: 02 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 7 STAR-053433 FOS/RD ACQ/BIN 4.3 MIRROR 1 19 S ONBOARD ACQ FOR 8 +215951-OFF ARY SET Comments: ACQUISITION PATTERN NAME Z. EXPOSURE TIME ALLOWS FOR HIGHER THAN NOMINAL V AND B-V. ------------------------------------------------------------------------------------------------------------------------------------ 8 STAR-053433 FOS/RD ACQ/PEA 0.3 G400H SCAN-STEP-Y=0.17,SCAN-STEP-X=0.17 1 14 S ONBOARD ACQ FOR 9-14 +215951-OFF K ,SEARCH-SIZE-Y=4,SEARCH-SIZE-X=4 SET Comments: ACQUISITION PATTERN NAME E1. EXPOSURE TIME ALLOWS FOR HIGHER THAN NOMINAL V AND B-V. ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC1952-HS. FOS/RD ACCUM 1.0 G400H 1 10 M SPOT Comments: EXPOSURE TIME TO GIVE S/N OF ROUGHLY 9 IN 4340 LINE, TAKING INTO ACCOUNT FWHM = 2.23 DIODES FOR EXTENDED SOURCE. ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1952-HS. FOS/RD ACCUM 1.0 G270H 1 40 M SPOT 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. ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC1952-HS. FOS/RD ACCUM 1.0 G270H 1 40 M SPOT ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC1952-HS. FOS/RD ACCUM 1.0 G270H 1 40 M SPOT ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC1952-HS. FOS/RD ACCUM 1.0 G270H 1 40 M SPOT ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC1952-HS. FOS/RD ACCUM 1.0 G270H 1 40 M SPOT ------------------------------------------------------------------------------------------------------------------------------------ 6765( 4) - 11/13/96 10:50 - [ 4] Summary Form for Proposal 6765 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCAN-STEP-Y=0.17 SCAN-STEP-X=0.17 SEARCH-SIZE-Y=4 SEARCH-SIZE-X=4 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category INTERSTELLAR MEDIUM ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3-6 ONBOARD ACQ FOR 8 ONBOARD ACQ FOR 9-14 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G400H G270H ------------------------------------------------------------------------------------------------------------------------------------ Target Names STAR-053433+220230-OFFSET NGC1952-LS.SPOT STAR-053433+215951-OFFSET NGC1952-HS.SPOT ------------------------------------------------------------------------------------------------------------------------------------