6125( 15) - 08/07/96 11:13 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6125 Version: 15 Check-in Date: 07-Aug-1996 11:10:10 1.Proposal Title: Imaging and Spectroscopy of SN 1885 in M31 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Interstellar Medium GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: ROBERT A. FESEN Dartmouth College CoI: Andrew Hamilton University of Colorado N ------------------------------------------------------------------------------------ 6. Abstract We request WFC images and FOS spectra of the remnant of S Andromedae, the historic 1885 supernova which occurred in the M31 bulge. Our 1988 discovery of this remnant as an unresolved dark spot of Fe I 3860 Angstrom \ absorption silhouetted against M31 suggests it contains a large quantity of cold, iron-rich ejecta expanding at up to 5000 km/s. These properties together with its bulge location are consistent with a SN I classification despite a peculiarly fast light curve. , Absorption line studies offer powerful new probes into the dynamical and chemical properties of SN ejecta. FOS Fe I LambdaLambda3720,3860 absorption profiles of the S And remnant will allow the first determination of an SN I's average iron density as a function of radius in the freely expanding ejecta. Only HST makes such a study possible. The remnant's estimated diameter is just 0.3'' - 0.5''. HST's superb PSF, small FOS apertures, and accurate, blind-offset positioning are crucial for this program. Cycle 1's degraded optics and M31's steep continuum fall-off below 3000 Angstrom \ prevented a detection in the UV. Attempted 3000 - 4000 Angstrom \ spectra from the ground have failed due to severe bulge light contamination on this sub-arcsec size target. WFC2 images will provide a precise remnant location for accurate FOS aperture positioning plus Fe I size and expansion asymmetry information. ------------------------------------------------------------------------------------ 6125( 15) - 08/07/96 11:13 - [ 2] Observations Description ------------------------ The orbital visibility of M31 is 54 minutes. We wish to obtain two WFC images of S And in EARLY ACQUISITION mode and then use these to determine accurate offset positioning of the remnant so precise FOS aperture targeting can be made. We would like to have a SNR of 20 or greater to clearly detect the remnant, check for expansion asymmetries, and measure accurate offsets. All WFC exposures will be CR-SPLIT to facilitate removal of the numerous cosmic rays. 1) For estimating WFC image exposures, we used published photometry of the M31 bulge (Kent 1983), IUE and HST flux measurements of the bulge near S And, and our original discovery groundbased 3880 Angstrom \\ images. S And is just 16 arcsec from the nucleus and there is a very steep gradient towards the nucleus (Kent 1983) and several small neighboring dust clouds. The surface brightness of the bulge at S And's position is about V = 14.0 mag. From the WFPC2 Handbook, we find the FQUVN-B filter (that is, the ``on'' band filter for detecting Fe I 3860 blueshifted absorption) has a intQT dLambda/Lambda = 0.00028. With a surface brightness of V = 14 mag/sq arcsec, an AB_V appropriate for the bulge at 3800 Angstrom \\ (Table 6.1; for gE galaxy AB = 2.0), we then calculate using Eq. 6.1 a N(e) = 28 electrons s^-1 arcsec^-2. This means that each 0.1'' WFC pixel will see 1/100 of this or N(e) = 0.28 e^- s^-1 pixel^-1. This agrees within a factor of two with an estimate using our groundbased 3880 Angstrom \\ images. A similar calculation for the ``off-band'' FQUVN-C filter gives N(e) = 0.38 e^- s^-1 pixel^-1. Sky background and readout noise are negligible. With 54 minutes orbital visibility minus the 12 minutes needed for GS Acquisition, that leaves 42 min for exposures and overhead. We can fit three 10 min exposures plus 8 minutes overhead per orbit. Since the count rate is higher for the off-band image, we would take this image in the first orbit, leaving the on-band image (FQUVN-B) for the next orbit which has only a 6 min GS re-acq. This would allow two 19 min CR-SPLIT exposures, each with 5 min OH, completely filling the orbit. This would give a 38 minute total FQUVN-B on-band Fe I image, with total counts around the target at 638 cts/pixel with a SNR = 23. The 30 minute off-band FQUVN-C images will collect 685 cts/pixel with a SNR = 24. Thus 2 orbits are needed for imaging, one for each filter. The remnant will occupy 9 to 25 pixels and should be well detected with these pixel counts. 2) FOS spectra need to cover the strong optical Fe I resonance lines at 3720 and 3860 Angstrom. The G400H grating with the Red Digicon will do this and actually peaks in sensitivity near these wavelengths (Fig. 1.2.3 FOS Handbook May 1994). To match the expected size of the remnant and to also pickup a neighboring section of the M31 bulge for comparison, we will use the 0.5-pair FOS apertures. These will sample both the target (S And) and sky (bulge light). HST makes studying S And feasible because of its precise positioning (+/- 0.02''; pg 43, HST Call for Proposals book). The early ACQ WFC images will yield accurate remnant size and position information necessary for accurate FOS aperture positioning. Since S And's dark Fe I absorption spot cannot be directly positioned on, we will use (like we did in Cycle 1) an offset star (mag 14) located 17.0'' west and 84.5'' north from S And (these measurements will be improved via the WFC images.) Acquisition of this star (12 min), and the series of four peakup target acquisitions using the 0.5'' apertures will take 7+ 14+ 12 + 17 minutes. Since the orbital visibility for M31 is 54 minutes, all but the last 17 minute stage can be fit into the first orbit (9 min are left unused). In Orbit 2 following re-acq (6 min) and the 17 min fourth stage, 25 minutes is needed to do the blind offset from the offset star to S And (page 18), leaving 6 min lost at the end. On Orbit 3 after re-acq, we can take a 42 minute exposure and still have 6 min for FOS/ACCUM overhead. This will be enough to get us a very good spectrum. The expected FOS count rate from the flux of M31's bulge at the S And site can be estimated directly from the Cycle 1 data. These show a rate N = 0.20 counts per diode at 3700 Angstrom \\ taking into consideration the larger aperture used (1.0'' pair), the higher resolution of the G270H grating vs G400H grating (i.e. 2.05 vs 3.0 Angstrom \\ per diode), and extrapolating from the observed flux at 3200 Angstrom \\ to 3800 Angstrom. This count rate is much larger than the FOS/RD dark signal of 0.01 cts/diode. Using the full 42 minutes we have left available in Orbit 3, the spectrum will have a SNR = 16 with 630 total cts/diode. This should be sufficient to detect weak absorption in the wings of the expected 5000 km/s broad profiles (= 60-70 Angstrom \\ or 20-23 diodes) for the stronger Fe I lines. Real Time Justification ----------------------- None. We have exhausted what can be practically done from the ground. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6125( 15) - 08/07/96 11:13 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6125( 15) - 08/07/96 11:13 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC224- ISM,SNR RA=00H 42M 42.930S +/- 0.1S, J2000 SN1885 DEC=+41D 15' 50.60" +/- 1", PLATE-ID=0738 Comments: Target is absorption "dark" spot in bulge of M31 which is the supernova remnant of 1885. 2 SN1885- STAR RA=00H 42M 41.312S +/- 0.2S, J2000 V = 15.0+/-1.5 OFFSET DEC=+41D 15' 24.13" +/- 1", PLATE-ID=0738 Comments: Off-setting star is 15.0 mag star SW of SN 1885. 3 SN1885 ISM,SNR RA=00H 42M 42.882S +/- 0.001S, J2000 V = 17.0+/-1.0 DEC=+41D 16' 05.02" +/- 0.01", PLATE-ID=0738 Comments: Target is a blind offset from 14 mag star (target 2). 4 NGC224 GALAXY,SPIRAL RA=00H 42M 44.190S +/- 0.1S, J2000 V = 14.0+/-2.0 DEC=+41D 16' 08.15" +/- 1", PLATE-ID=0738 Comments: Target is background M31 bulge light near nucleus. 6125( 15) - 08/07/96 11:13 - [ 5] 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC224-SN18 WFPC2 IMAGE WF3-FIX FQUVN 3916 1 400 S 85 ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC224-SN18 WFPC2 IMAGE WF3-FIX FQUVN 3916 1 400 S 85 ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC224-SN18 WFPC2 IMAGE WF3-FIX FQUVN 3916 1 400 S POS TARG -0.50,-0.50 85 ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC224-SN18 WFPC2 IMAGE WF3-FIX FQUVN 3916 1 400 S POS TARG -0.50,-0.50 85 ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC224-SN18 WFPC2 IMAGE WF4-FIX FQUVN 3839 CR-SPLIT=NO 1 500 S 85 ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC224-SN18 WFPC2 IMAGE WF4-FIX FQUVN 3839 CR-SPLIT=NO 1 500 S 85 ------------------------------------------------------------------------------------------------------------------------------------ 23 NGC224-SN18 WFPC2 IMAGE WF4-FIX FQUVN 3839 CR-SPLIT=NO 1 500 S POS TARG -0.50,-0.50 85 ------------------------------------------------------------------------------------------------------------------------------------ 24 NGC224-SN18 WFPC2 IMAGE WF4-FIX FQUVN 3839 CR-SPLIT=NO 1 500 S POS TARG -0.50,-0.50 85 ------------------------------------------------------------------------------------------------------------------------------------ 6125( 15) - 08/07/96 11:13 - [ 6] Visit: 02 Visit Requirements: ON HOLD FOR 1 On Hold Comments: Waiting for EARLY ACQ of VISIT 1 WFPC2 IMAGING for precise positional information to insure detection with FOS apertures. Additional Comments: The WFPC2 images will guide the FOS spectral observations in target offset positioning and aperature selection. The ACQ/PEAK 4 obs. could be dropped and exposure 105 lengthened if target is larger than 0.5 arcsec in dia. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 101 SN1885-OFFS FOS/RD ACQ/PEA 4.3 G400H 4000 SCAN-STEP-Y=1.204,SEARCH-SIZE-X=1 1 1.0 S ONBOARD ACQ FOR 102 ET K ,SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 102 SN1885-OFFS FOS/RD ACQ/PEA 1.0 G400H 4000 SCAN-STEP-X=.602,SCAN-STEP-Y=.602 1 1.0 S ONBOARD ACQ FOR 103 ET K ,SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 103 SN1885-OFFS FOS/RD ACQ/PEA 0.5 G400H 4000 SCAN-STEP-X=.172,SCAN-STEP-Y=.172 1 1.0 S ONBOARD ACQ FOR 104 ET K ,SEARCH-SIZE-X=5,SEARCH-SIZE-Y=5 ------------------------------------------------------------------------------------------------------------------------------------ 104 SN1885-OFFS FOS/RD ACQ/PEA 0.3 G400H 4000 SCAN-STEP-X=.05,SCAN-STEP-Y=.05, 1 10.0 S ONBOARD ACQ FOR 105 ET K SEARCH-SIZE-X=5,SEARCH-SIZE-Y=5 ------------------------------------------------------------------------------------------------------------------------------------ 105 SN1885 FOS/RD ACCUM 0.5 G400H 4000 1 3000 S ------------------------------------------------------------------------------------------------------------------------------------ 106 NGC224 FOS/RD ACCUM 1.0 G400H 4000 1 530 S ------------------------------------------------------------------------------------------------------------------------------------ 6125( 15) - 08/07/96 11:13 - [ 7] Visit: 51 Visit Requirements: On Hold Comments: Additional Comments: HOPR Repeat Visit for failed visit 02. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 200 NGC224 FOS/RD ACCUM 1.0 G400H 1 420 S EXPAND ------------------------------------------------------------------------------------------------------------------------------------ 201 SN1885-OFFS FOS/RD ACQ/PEA 4.3 G570H SCAN-STEP-Y=1.23,SEARCH-SIZE-X=1, 1 2.3 S ONBOARD ACQ FOR 202 ET K SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 202 SN1885-OFFS FOS/RD ACQ/PEA 1.0 G570H SCAN-STEP-X=.61,SCAN-STEP-Y=.61, 1 2.5 S ONBOARD ACQ FOR 203 ET K SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 203 SN1885-OFFS FOS/RD ACQ/PEA 0.5 G570H SCAN-STEP-X=.29,SCAN-STEP-Y=.29, 1 2.6 S ONBOARD ACQ FOR 204 ET K SEARCH-SIZE-X=3,SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 204 SN1885-OFFS FOS/RD ACQ/PEA 0.3 G570H SCAN-STEP-X=.11,SCAN-STEP-Y=.11, 1 30.0 S ONBOARD ACQ FOR 205 ET K SEARCH-SIZE-X=4,SEARCH-SIZE-Y=4 ------------------------------------------------------------------------------------------------------------------------------------ 205 SN1885 FOS/RD ACCUM 0.5 G400H 1 4200 S EXPAND ------------------------------------------------------------------------------------------------------------------------------------ 6125( 15) - 08/07/96 11:13 - [ 8] Summary Form for Proposal 6125 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO SEARCH-SIZE-Y=3 SEARCH-SIZE-Y=2 SEARCH-SIZE-Y=5 SEARCH-SIZE-X=5 SEARCH-SIZE-X=1 SEARCH-SIZE-X=6 SEARCH-SIZE-X=3 SEARCH-SIZE-Y=4 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Interstellar Medium ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG -0.50,-0.50 ON HOLD FOR 1 ONBOARD ACQ FOR 102 ONBOARD ACQ FOR 103 ONBOARD ACQ FOR 104 ONBOARD ACQ FOR 105 EXPAND ONBOARD ACQ FOR 202 ONBOARD ACQ FOR 203 ONBOARD ACQ FOR 204 ONBOARD ACQ FOR 205 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements FQUVN G400H G570H ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC224-SN1885 SN1885-OFFSET NGC224 ------------------------------------------------------------------------------------------------------------------------------------