6420( 6) - 07/05/96 10:21 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6420 Version: 6 Check-in Date: 05-Jul-1996 10:16:41 1.Proposal Title: Phase Resolved UV Spectroscopy of the Peculiar Binary V Sge ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle BINARIES AND STAR FOR GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Janet Wood KEELE UNIVERSITY CoI: Jonathan Lockley Keele University N ------------------------------------------------------------------------------------ 6. Abstract The close binary system V Sge is an extremely unusual object. It is thought to be related to cataclysmic variables or low mass X-ray binaries, though it is not clear if the compact accreting star is a white dwarf, neutron star or black hole. The light curve of V Sge shows deep primary and shallow secondary eclipses, while the optical spectra have shown that it is undergoing rapid mass loss in a wind. V Sge may represent a short--lived stage in the evolution of interacting binaries that has otherwise not been observed. It has faded significantly in the last 30 years. Optical spectroscopy and UV studies with IUE have led to contradictory conclusions for the model of the system. This problem is probably due to the low spectral resolution of the time-resolved IUE spectra. We will use the GHRS on HST to obtain high time-resolution, high spectral-resolution UV spectroscopy. With the G160M grating in WSCAN mode we will observe the the CIV 1549Angstrom\ doublet to investigate the mass loss and the HeII 1641Angstrom\ line to relate this to the behaviour of the underlying system. We will use the changes in the line profiles throughout the orbit and through the primary and secondary eclipses to determine the origin of the UV light and the structure of the system. ------------------------------------------------------------------------------------ 6420( 6) - 07/05/96 10:21 - [ 2] Observations Description ------------------------ We will obtain phase resolved spectroscopy through a complete orbital cycle of V Sge including both primary and secondary eclipse. V Sge cannot be observed in the continuuous viewing zone therefore Earth occultations will occur. However, the Earth occultations are short compared to the orbital period (12.34 hrs), and compared to the duration of the eclipses (~ 5 hrs), therefore the phase coverage we obtain will be sufficient. We will use the HRS with the LSA and the G160M grating covering 36Angstrom\\\\\\\\ with a resolution of 0.07Angstrom/diode. Using WSCAN mode we will observe alternately the CIV LambdaLambda 1548,1551Angstrom\\\\\\\\ doublet and the HeII Lambda1640Angstrom\\\\\\\\ line. We note that, the FWZI of the lines in the high state are ~3000 km s^-1 therefore the G160M grating can easily cover the whole of each line. With integration times of 8.6 mins (0.012 in phase), the cycle time for the WSCAN will be 24mins. The orbital period of V Sge is 12.34 hrs therefore we can obtain good phase resolution and covererage using this mode. IUE observations of V Sge 4, 5 show that in the high state the continuum from 1400--1700Angstrom\\\\\\\\ is f_Lambda=6 * 10^-13 ergs s^-1 cm^-2 AA^-1. Therefore we expect 126 counts/diode in each 8.6 min integration i.e. a signal- to-noise ratio of 11 in the continuum. At the peak of the strongest line, the HeII line, f_Lambda=3.6 * 10^-12 ergs s^-1 cm^-2 AA^-1, therefore we expect a maximum count rate of 743 counts/diode in our exposures. If V Sge is in the low state, f_Lambda ~ 3 * 10^-13 ergs s^-1 cm^-2 AA^-1. and hence we expect 63 counts/diode in each 8.6 min integration i.e. a signal-to-noise ratio of 8 in the continuum. At the peak of the HeII line, f_Lambda=2.0 * 10^-12 ergs s^-1 cm^-2 AA^-1, therefore we expect a maximum count rate of 413 counts/diode in the low state. The total exposure time required is dictated by the need to cover one orbital cycle of V Sge, not by the signal-to-noise ratio. This means that using STIS would not save spacecraft time. Since V Sge is so bright with strong emission lines, neutral density filters would probably be necessary with STIS. There is a 14th magnitude star only 10-arcsec away from V Sge therefore the target must be acquired with care. V Sge has an orbital period of 740 mins, therefore, allowing for time to acquire the target and guide stars and instrumental overheads we require 11 spacecraft orbits. Real Time Justification ----------------------- The HST orbits must be consecutive to ensure good phase coverage of the orbital cycle. We will attempt to obtain contemporaneous ground-based observations of V Sge using the 24-inch telescope at Keele. The success of the project does not, however, depend on the ground based observations. Calibration Justification ------------------------- Additional Comments ------------------- It is important that all integrations cover the same fraction of binary phase i.e. they are all the same length and are not paused. The subexposures should NOT be split by the SAA or Earth occultations, though the wscan can be split between the two separate subexposures. The exposure time can be adjusted to make the observation efficient as long as all exposures remain the same length as each other. ------------------------------------------------------------------------------------ 6420( 6) - 07/05/96 10:21 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6420( 6) - 07/05/96 10:21 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 V-SGE STAR,INTERACTING RA=20H 20M 14.71S +/- J2000 Z=0.0 V = 11.5+/-1.5 BINARY,NOVA-LIKE 0.02S,DEC=21D 6' 9.1" +/- B-V = -0.1+/-0.1 0.3",PLATE-ID=02UR E(B-V) = 0.0+/-0.05 F-CONT(1500)=4+/-2e-13 F-LINE(1640)=10+/-1e-13 Comments: There is a V=14 star 10" from V Sge. V Sge is the Eastern of the pair. The magnitude range covers eclipses and intrinsic variability. 6420( 6) - 07/05/96 10:21 - [ 5] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: WSCAN can be split between sub exposures, the exposure times can be altered as long as all exposure times remain equal to each other. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 V-SGE HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN 1 3.6 S ONBOARD ACQ FOR 2-23 Comments: step-time=0.4S expect > 2500 counts ------------------------------------------------------------------------------------------------------------------------------------ 2 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 3 V-SGE HRS ACCUM 2.0 G270M 2800 1 435.2 S ------------------------------------------------------------------------------------------------------------------------------------ 4 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 5 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 6 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 7 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 8 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 9 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 10 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 11 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 12 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 13 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 14 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 15 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 6420( 6) - 07/05/96 10:21 - [ 6] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 16 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 17 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 18 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 19 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 20 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 21 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 22 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 23 V-SGE HRS WSCAN 2.0 G160M 1503.5- FP-SPLIT=NO,WAVE-STEP=91.0 1 1033.6 NO SPLIT 1685.5 ------------------------------------------------------------------------------------------------------------------------------------ 6420( 6) - 07/05/96 10:21 - [ 7] Summary Form for Proposal 6420 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ WSCAN ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=RETURN WAVE-STEP=91.0 FP-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category BINARIES AND STAR FORMATION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2-23 NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G160M G270M ------------------------------------------------------------------------------------------------------------------------------------ Target Names V-SGE ------------------------------------------------------------------------------------------------------------------------------------