9371( 3) - 02/18/02 10:44 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9371 Version: 3 Check-in Date: 18-Feb-2002 10:43:51 1.Proposal Title: A Definitive Test of the Nature of SN 1961V: Supernova vs. Luminous Blue Variable ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: You-Hua Chu University of Illinois at Urbana - Champaign CoI: Dr. John Cowan University of Oklahoma N CoI: Dr. Robert Gruendl University of Illinois Y CoI: Dr. Chris Stockdale Naval Research Laboratory N CoI: Dr. Scott Teare New Mexico Institute of Mining and N Technology ------------------------------------------------------------------------------------ 5. Abstract The most massive stars evolve into luminous blue variables (LBVs) and end their lives in supernovae (SNe). Studies of the late evolutionary stages of the most massive stars will aid our understanding of the chemical enrichment and stellar energy feedback in a galaxy. The final days of the most massive stars can be confusing, as LBV outbursts often mimic SN explosions. The nature of three SNe have been called into question: SN 1954J and SN 1997bs are most likely LBVs, but the nature of SN 1961V is still debatable. SN 1961V is a peculiar SN in a complex environment. Its decaying nonthermal radio emission is consistent with a radio supernova, while its optical light curve and initial expansion velocity suggest an LBV outburst similar to Eta Car. HST WFC1 images could not conclusively identify the LBV. SN 1961V is either a bona fide SN related to exotic hypernovae or failed supernovae, or a superluminous LBV that is the most massive star known. We request STIS observations, necessary for their high spatial resolution, to use emission lines to identify LBV candidates and to discriminate among LBV ejecta nebula, decades-old SN/SNR, and mature SNR that are present within 1" from SN 1961V. ------------------------------------------------------------------------------------ 9371( 3) - 02/18/02 10:44 - [ 2] Observations Description ------------------------ We will use STIS/CCD observations with the 52"x2" slit to search for emission- line objects near the position of SN 1961V. Two STIS configurations will be used. The first configuration will use the G750M grating with the central wavelength 6581 A, in order to observe H-Alpha, [OI] 6300, [NII] 6548, 6584, and [SII] 6716, 6731 simultaneously. The second configuration will use the G430M grating with the central wavelength 4961 A, in order to observe H-Beta and [OIII] 4959, 5007 simultaneously. The 52"x2" slit should be oriented with a position angle between 119 and 140 degrees (along either the +y or -y axis of STIS in order to cover all sources near the position of SN 1961V with minimal confusion. Due to the complexity of the field, we will use the recommended sequence for STIS slitless spectroscopy. Therefore we will also need to image the field STIS/CCD without a grating. We have used the WFPC2 F658N [NII] observations of Eta Car by Smith et al. (2000, AJ, 120, 920) to estimate the exposure time necessary to detect SN1961V. The total F658N flux for the inner 20" of Eta Car is 4.85E-9 ergs/s/cm^2. At the distance of NGC 1058 this corresponds to an unresolved source with total flux ~3E-16 ergs/s/cm^2. For a nitrogen-enriched LBV nebula, the [NII] 6584 line will have roughly the same brightness as the H-Alpha emission. Using the STIS spectroscopic exposure time calculator we find that we can detect such an unresolved source with S/N of ~20 with a 1800 s CR-SPLIT exposure, if the line width is 1.5 A (~ 70 km/s). For [OIII] (using the G430M grating), a line with similar brightness and width as the [NII] line would be detected with S/N of ~10 with a 2100 second exposure. We therefore request one orbit for each STIS configuration. We have used the STIS imaging ETC to determine the exposure time needed to detect the faintest source in the region of interest in the spectroscopic exposures. The faintest source is estimated to have V=25.5 mag (Filippenko, 1995, AJ, 110, 2261). We will use the CLEAR (50CCD) to image the field requires and thus a 900 second exposure is necessary to obtain a S/N of ~10. Real Time Justification ----------------------- None. N.A. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9371( 3) - 02/18/02 10:44 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SN1961V- STAR RA=2H 43M 36.93S +/- 0.05S, J2000 V = 18.4 OFFSET DEC=37D 21' 09.36" +/- 0.1", PLATE-ID=031L Coordinate Source: IMAGE_TIED_TO_GSC_FRAME Comments: STAR-024337+372109 will be used for ACQ. Position is based on same WF/PC I image as Target 2. V mag is measured from a WFPC2 F606W snapshot image. Colors are unknown. The ACQ exposure time calculator predicts that a 5 second exposure will have S/N > 40. 2 SN1961V EXT-STAR, Supernova RA=2H 43M 36.478S +/- 0.05S, J2000 V=+518 V = 25.6 Type II DEC=37D 20' 42.8" +/- 0.1", B-V = 1.6 PLATE-ID=031L E(B-V) = 0.15 Coordinate Source: IMAGE_TIED_TO_GSC_FRAME Comments: Position is based on WF/PC I image tied to the GSC1.0 frame. V and B-V are based on Filippenko et al. 1995, AJ, 110, 2261. (Note: we are searching for nebular line emission from the source, not continuum) 9371( 3) - 02/18/02 10:44 - [ 4] Visit: 01 Visit Priority: Visit Requirements: ORIENT 164D TO 185D; ORIENT 344D TO 5D On Hold Comments: Additional Comments: Orient needed is such that the STIS slit has its + or -y axis between the position angles 119 and 140 (note the values given in this comment are PAs not directions for the U3 axis). Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 SN1961V-OFF STIS/C ACQ 50CCD MIRROR 1 5 S SET CD ------------------------------------------------------------------------------------------------------------------------------------ 20 SN1961V STIS/C ACCUM 52X2 G750M 6581 CR-SPLIT=4 1 3600 S EXPAND CD ------------------------------------------------------------------------------------------------------------------------------------ 30 SN1961V STIS/C ACCUM 50CCD MIRROR CR-SPLIT=4 1 1800 S CD Comments: This exposure is designed to take an image of the targets in the slit. ------------------------------------------------------------------------------------------------------------------------------------ 40 SN1961V STIS/C ACCUM 52X2 G430M 4961 CR-SPLIT=4 1 3600 S EXPAND CD ------------------------------------------------------------------------------------------------------------------------------------ 9371( 3) - 02/18/02 10:44 - [ 5] Summary Form for Proposal 9371 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 50CCD 52X2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=4 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 164D TO 185D; ORIENT 344D TO 5D EXPAND ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G750M G430M ------------------------------------------------------------------------------------------------------------------------------------ Target Names SN1961V-OFFSET SN1961V ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 6581 4961 ------------------------------------------------------------------------------------------------------------------------------------