! Proposal 6643, submission 1 ! PI: Klaus Beuermann ! Received Fri Feb 2 09:15:58 EST 1996 ! From: boris@uni-sw.gwdg.de Proposal_Information ! Section 4 Title: Supersoft sources in the LMC Proposal_Category: GO Scientific_Category: BINARIES AND STAR FORMATION Cycle: 6 Investigators PI_name: Klaus Beuermann PI_Institution: Universitaets-Sternwarte Goettingen CoI_Name: Boris T. Gaensicke CoI_Institution: Universitaets-Sternwarte Goettingen Contact: Y CoI_Name: Klaus Reinsch CoI_Institution: Universitaets-Sternwarte Goettingen Contact: N CoI_Name: Andre van Teeseling CoI_Institution: Universitaets-Sternwarte Goettingen Contact: N 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'. Questions ! Free format text (please update) Observing_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: Fixed_Targets Target_Number: 1 Target_Name: CAL83 Alternate_Names: Description: STAR, INTERACTING BINARY Position: RA=05H 43M 34.3S +/- 0.5" , DEC=-68D 22' 22.2" +/- 0.5", PLATE-ID=05ZW Equinox: J2000 RV_or_Z: RA_PM: Dec_PM: Epoch: Annual_Parallax: Flux: V=17.0 +/- 0.5 B-V = 0.0 +/- 0.1 E(B-V) = 0.1 +/- 0.03 F-CONT(1300) = 2.3 +/- 0.8e-14 Comments: Target_Number: 2 Target_Name: RXJ0513-69 Alternate_Names: Description: STAR, INTERACTING BINARY Position: RA=05H 13M 50.9S +/- 0.5" , DEC=-69D 51' 47.5" +/- 0.5", PLATE-ID=05ZW Equinox: J2000 RV_or_Z: RA_PM: Dec_PM: Epoch: Annual_Parallax: Flux: V=17.0 +/- 0.5 B-V = -0.14 +/- 0.04 E(B-V) = 0.1 +/- 0.03 F-CONT(1300) = 3.0 +/- 1.0e-14 Comments: Visits Visit_Number: 1 Visit_Requirements: CVZ On_Hold_Comments: Visit_Comments: Exposure_Number: 1 Target_Name: CAL83 Config: FOS/BL Opmode: ACQ/PEAK Aperture: 4.3 Sp_Element: MIRROR Optional_Parameters: SEARCH-SIZE-X=1, SEARCH-SIZE-Y=3, SCAN-STEP-Y=1.23 Number_of_Iterations: 1 Time_Per_Exposure: 8S Special_Requirements: ONBOARD ACQ FOR 2 Comments: FOS search pattern A Exposure_Number: 2 Target_Name: CAL83 Config: FOS/BL Opmode: ACQ/PEAK Aperture: 1.0 Sp_Element: MIRROR Optional_Parameters: SEARCH-SIZE-X=6, SEARCH-SIZE-Y=2, SCAN-STEP-X=0.61, SCAN-STEP-Y=0.61 Number_of_Iterations: 1 Time_Per_Exposure: 8.8S Special_Requirements: ONBOARD ACQ FOR 3 Comments: FOS search pattern B1 Exposure_Number: 3 Target_Name: CAL83 Config: FOS/BL Opmode: ACQ/PEAK Aperture: 0.5 Sp_Element: MIRROR Optional_Parameters: SEARCH-SIZE-X=3, SEARCH-SIZE-Y=3, SCAN-STEP-X=0.29, SCAN-STEP-Y=0.29 Number_of_Iterations: 1 Time_Per_Exposure: 9.6S Special_Requirements: ONBOARD ACQ FOR 4 Comments: FOS search pattern C1 Exposure_Number: 4 Target_Name: CAL83 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140L Wavelength: 1292 Optional_Parameters: FP-SPLIT=NO, COMB=FOUR, STEP-TIME=0.2, STEP-PATT=DEF Number_of_Iterations: 6 Time_Per_Exposure: 462.4S Special_Requirements: Comments: Visit_Number: 2 Visit_Requirements: CVZ On_Hold_Comments: Visit_Comments: Exposure_Number: 5 Target_Name: RXJ0513-69 Config: FOS/BL Opmode: ACQ/PEAK Aperture: 4.3 Sp_Element: MIRROR Optional_Parameters: SEARCH-SIZE-X=1, SEARCH-SIZE-Y=3, SCAN-STEP-Y=1.23 Number_of_Iterations: 1 Time_Per_Exposure: 8S Special_Requirements: ONBOARD ACQ FOR 6 Comments: FOS search pattern A Exposure_Number: 6 Target_Name: RXJ0513-69 Config: FOS/BL Opmode: ACQ/PEAK Aperture: 1.0 Sp_Element: MIRROR Optional_Parameters: SEARCH-SIZE-X=6, SEARCH-SIZE-Y=2, SCAN-STEP-X=0.61, SCAN-STEP-Y=0.61 Number_of_Iterations: 1 Time_Per_Exposure: 8.8S Special_Requirements: ONBOARD ACQ FOR 7 Comments: FOS search pattern B1 Exposure_Number: 7 Target_Name: RXJ0513-69 Config: FOS/BL Opmode: ACQ/PEAK Aperture: 0.5 Sp_Element: MIRROR Optional_Parameters: SEARCH-SIZE-X=3, SEARCH-SIZE-Y=3, SCAN-STEP-X=0.29, SCAN-STEP-Y=0.29 Number_of_Iterations: 1 Time_Per_Exposure: 9.6S Special_Requirements: ONBOARD ACQ FOR 8 Comments: FOS search pattern C1 Exposure_Number: 8 Target_Name: RXJ0513-69 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140L Wavelength: 1292 Optional_Parameters: FP-SPLIT=NO, COMB=FOUR, STEP-TIME=0.2, STEP-PATT=DEF Number_of_Iterations: 6 Time_Per_Exposure: 462.4S Special_Requirements: Comments: Data_Distribution ! 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