6643( 6) - 08/20/96 15:19 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6643 Version: 6 Check-in Date: 20-Aug-1996 15:15:43 1.Proposal Title: Supersoft sources in the LMC ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle BINARIES AND STAR FOR GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: KLAUS BEUERMANN UNIVERSITAETS-STERNWARTE GOETTINGEN CoI: Boris T. Gaensicke Universitaets-Sternwarte Goettingen Y CoI: Klaus Reinsch Universitaets-Sternwarte Goettingen N CoI: Andre van Teeseling Universitaets-Sternwarte Goettingen N ------------------------------------------------------------------------------------ 6. Abstract 'Supersoft sources' (SSS) have been discovered during the ROSAT mission as a new class of objects characterized by their high luminosity and extremely soft X-ray spectra. A few SSS have been identified as binary systems with a compact primary accreting at high mass-transfer rates. The nature of the primary and the evolutionary status of SSS are still debated. Currently, the most promising model suggests nuclear burning on a white dwarf primary accreting near the Eddington rate. However, models including a black hole or neutron star cannot yet be ruled out. We propose to obtain high-quality UV spectra with the GHRS low-resolution grating G140L of two SSS in the LMC which have been proven to be accreting binary systems. These are the only two very luminous binary SSS which are sufficiently bright to be accessible with HST. Although we request only two s/c orbits, these data will provide important new information about the central sources, the accretion disks, and the winds in these systems. Understanding the nature of supersoft sources is not possible without high- quality data in the FUV. In particular, we wish to separate stellar and interstellar components of the absorption lines of C II, Si II, Si III, Si IV, and N V, search for the presence of stellar LyAlpha absorption and fainter emission or absorption lines due to other ions, search for rotational broadening, derive elemental abundances, and test the combined results against current models of `Supersoft Sources'. ------------------------------------------------------------------------------------ Observations Description ------------------------ The supersoft source CAL 83 and RX J0513 are situated in the Continuous Viewing Zone, reducing the requested amount of spacecraft time to one orbit per object. We will observe both targets with the GHRS using the G140L, covering the wavelength range from 1150--1435 Angstrom which contains numerous diagnostically important emission and absorption lines (e.g. LyAlpha, N V, Si II, C II, Si IV). The UV flux, known from IUE spectra (cf. Fig. 1 and Pakull et al. 1993), is ~2.5*10^-14. As the UV variability is unknown, it will be safest to use FOS/BL assisted acquisition, which leaves ~50 min for science exposures. If the objects are found at the known IUE flux level, the expected countrate at 1400 Angstrom is ~0.41 cts, resulting in a signal-to-noise ratio of ~35. Real Time Justification ----------------------- None. Calibration Justification ------------------------- Real_Time_Justification Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6643( 6) - 08/20/96 15:19 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 CAL83 STAR, INTERACTING RA=05H 43M 34.3S +/- 0.5" , DEC= J2000 V = 17.0+/-0.5 BINARY -68D 22' 22.2" +/- 0.5", PLATE- B-V = 0.0+/-0.1 ID=05ZW E(B-V) = 0.1+/-0.03 F-CONT(1300)=2.3+/-0.8e-14 2 RXJ0513-69 STAR, INTERACTING RA=05H 13M 50.9S +/- 0.5" , DEC= J2000 V = 17.0+/-0.5 BINARY -69D 51' 47.5" +/- 0.5", PLATE- B-V = -0.14+/-0.04 ID=05ZW E(B-V) = 0.1+/-0.03 F-CONT(1300)=3.0+/-1.0e-14 6643( 6) - 08/20/96 15:19 - [ 2] Visit: 01 Visit Requirements: CVZ 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 CAL83 FOS/BL ACQ/PEA 4.3 MIRROR SEARCH-SIZE-X=1,SEARCH-SIZE-Y=3, 1 8 S ONBOARD ACQ FOR 2 K SCAN-STEP-Y=1.23 Comments: FOS search pattern A ------------------------------------------------------------------------------------------------------------------------------------ 2 CAL83 FOS/BL ACQ/PEA 1.0 MIRROR SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2, 1 8.8 S ONBOARD ACQ FOR 3 K SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 Comments: FOS search pattern B1 ------------------------------------------------------------------------------------------------------------------------------------ 3 CAL83 FOS/BL ACQ/PEA 0.5 MIRROR SEARCH-SIZE-X=3,SEARCH-SIZE-Y=3, 1 9.6 S ONBOARD ACQ FOR 4 K SCAN-STEP-X=0.29,SCAN-STEP-Y=0.29 Comments: FOS search pattern C1 ------------------------------------------------------------------------------------------------------------------------------------ 4 CAL83 HRS ACCUM 2.0 G140L 1292 FP-SPLIT=NO,COMB=FOUR, 6 462.4 S STEP-TIME=0.2,STEP-PATT=DEF ------------------------------------------------------------------------------------------------------------------------------------ 6643( 6) - 08/20/96 15:19 - [ 3] Visit: 02 Visit Requirements: CVZ 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 ------------------------------------------------------------------------------------------------------------------------------------ 5 RXJ0513-69 FOS/BL ACQ/PEA 4.3 MIRROR SEARCH-SIZE-X=1,SEARCH-SIZE-Y=3, 1 8 S ONBOARD ACQ FOR 6 K SCAN-STEP-Y=1.23 Comments: FOS search pattern A ------------------------------------------------------------------------------------------------------------------------------------ 6 RXJ0513-69 FOS/BL ACQ/PEA 1.0 MIRROR SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2, 1 8.8 S ONBOARD ACQ FOR 7 K SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 Comments: FOS search pattern B1 ------------------------------------------------------------------------------------------------------------------------------------ 7 RXJ0513-69 FOS/BL ACQ/PEA 0.5 MIRROR SEARCH-SIZE-X=3,SEARCH-SIZE-Y=3, 1 9.6 S ONBOARD ACQ FOR 8 K SCAN-STEP-X=0.29,SCAN-STEP-Y=0.29 Comments: FOS search pattern C1 ------------------------------------------------------------------------------------------------------------------------------------ 8 RXJ0513-69 HRS ACCUM 2.0 G140L 1292 FP-SPLIT=NO,COMB=FOUR, 6 462.4 S STEP-TIME=0.2,STEP-PATT=DEF ------------------------------------------------------------------------------------------------------------------------------------ 6643( 6) - 08/20/96 15:19 - [ 4] Summary Form for Proposal 6643 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 SCAN-STEP-Y=1.23 SCAN-STEP-Y=0.61 SCAN-STEP-Y=0.29 STEP-PATT=DEF SCAN-STEP-X=0.61 SCAN-STEP-X=0.29 STEP-TIME=0.2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category BINARIES AND STAR FORMATION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3 ONBOARD ACQ FOR 4 ONBOARD ACQ FOR 6 ONBOARD ACQ FOR 7 ONBOARD ACQ FOR 8 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names CAL83 RXJ0513-69 ------------------------------------------------------------------------------------------------------------------------------------