6889( 6) - 08/13/96 14:22 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6889 Version: 6 Check-in Date: 13-Aug-1996 14:19:15 1.Proposal Title: The accretion region and accretion flow of QS Tel. ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle BINARIES AND STAR FOR GO/DD 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: SIMON ROSEN University of Leicester CoI: Domitilla de Martino Vilspa Y CoI: Martine Mouchet Observatoire de Paris N CoI: Julian Osborne University of Leicester N CoI: Richard Lieu University of Alabama N CoI: Andrew Layden McMaster University N CoI: Jon Mittaz Mullard Space Science Laboratory N ------------------------------------------------------------------------------------ 6. Abstract A short, exploratory HST observation of the AM~Her binary, QS Tel, in 1994 aimed to isolate and quantify the contribution of the accretion region in the UV band. When proposed, QS~Tel was only known to actively accrete at one pole. The subsequent discovery of a two pole accretion mode in our EUV observations and our lack of knowledge of the accretion mode at the time of the HST observation (only securely established via EUV or X-ray data) severely hampers interpretation of the HST data. Our previous work suggests that QS Tel undergoes relatively frequent and dramatic changes of its accretion geometry in comparison to other AM Her stars, offering an excellent opportunity to pin down the causes of such alterations. Here we primarily seek to obtain coordinated EUV and HST coverage of QS Tel to remove the existing ambiguities and precisely relate the UV and EUV emission. At the same time we will quantify the EUV and UV spectral properties of a dip, discovered in the EUV band and (apparently) observed once by HST. This dip probably arises from occultation of the accretion site by the material flowing onto it. Quasi-simultaneous EUV and UV information will help us to more securely establish the absorption mechanism responsible for the dip. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will observe QS~Tel with the FOS (blue digicon). We intend to use the G160L grating to span the 1150-2500A range. Use of the 1.0-Pair (upper) aperture will remove the problems from the instrumental feature near 1500\\AA. FOS RAPID mode will be employed to obtain quasi-continuous sequences of 20s exposures. From our previous observation of QS~Tel, we anticipate achieving a signal of about 0.3, 0.7 and 3.4 cts/s/diode at the 1250, 1500 and 2400\\AA\\ continuum respectively (corresponding to S/N levels of 2.5, 4 and 8/diode) per 20s exposure. To study the underlying binary orbital modulation and to quantify corresponding changes in spectral slope, the data from our 4 allocated HST orbits will be phase-folded into at least 40 phase bins/cycle. Each phase bin would then contain about 300s of effective exposure (assuming uniform sampling), enhancing the S/N by about a factor 4 over that achieved in the 20s integrations. This would be quite adequate for measuring orbitally dependent changes in spectral shape. Light curves will be extracted over coarse (200\\AA) wavelength bins (i.e. combining about 28 wavelength pixels). In each 20s exposure, this would thus improve the S/N estimates above by a factor 5. During the narrow dip (which lasts about 500s in the previous HST observation), we can expect a reduction of perhaps 25\\% in flux. In a 60s time bin (0.007 in phase) in the dip, we would obtain 32 cts/diode at the 1500\\AA\\ continuum. Our 4 orbit allocation may observe 2 dips which when combined, would yield a S/N of about 8/diode in each 0.007 wide phase bin. Corresponding values of S/N at the 1200 and 2400\\AA\\ continuum would be about 5 and 17 respectively, assuming a wavelength independent decline during the dip. Thus we will be sensitive to evolution of the spectral slope during the dip. Combined with EUV and optical/IR data, this will help elucidate the mechanism(s) responsible for the dip in each band. A key point to note is that these HST observations now form part of the most extensive multi-wavelength campaign ever conducted on an AM Her star. Currently, we have been awarded EUVE (EUV) and ASCA (X-ray) observations of the star that are expected to be scheduled and coordinated in the last week of September. We are applying for, and anticipate a succesful outcome for accompanying IR spectroscopic and optical photometric observations, to be made from CTIO. We also expect to secure complementary optical polarimetric observations from SAAO. Thus the HST observations of QS Tel, especially if made very close in time to the ASCA/EUVE/CTIO/SAAO runs, will powerfully underpin the scientific return from the campaign. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- The EUVE run is for 20ksecs (ID=051; PI=ROSEN). The ASCA observation is for 20ksecs (ID =43015 (sequence ID=34012000); PI=ROSEN). The two observations are to be coordinated, provisionally in the last week of September 96. Both observations will span a total interval of about 14 hours. HST simultaneity would be ideal but observations within 1 or 2 days (if possible) of the ASCA/EUVE runs will be acceptable, even if simultaneity is not feasible. Contacts for EUVE and ASCA are Ron Oliversen (OLIVERSEN@STARS.GSFC.NASA.GOV - 1st port of call) and Paul Hilton (paul@astro.isas.ac.jp) respectively. ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6889( 6) - 08/13/96 14:22 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 QS-TEL STAR, INTERACTING RA=19H 38M 35.76S +/- 1.0", DEC= J2000 V = 15.5+/-0.5 BINARY, Polar (AM Her -46D 12' 56.34" +/- 1.0", PLATE- B-V = 0.00+/-0.3 Star) ID=04FS E(B-V) = 0.0+/-0.1 F-CONT(1250)=2.0+/-1.5e-14 F-CONT(1550)=1.6+/-0.8e-14 F-CONT(2400)=1.0+/-0.5e-14 F-LINE(1550)=1.4+/-5.0e-13 W-LINE(1550)=8+/-3 Comments: Flux estimates are based on our previous observation. RA, DEC and PLATE-ID are from our cycle 4 proposal 6889( 6) - 08/13/96 14:22 - [ 2] Visit: 01 Visit Requirements: BETWEEN 23-SEP-96 AND 30-SEP-96 On Hold Comments: Additional Comments: To complement our already accepted EUVE and ASCA observations of QS Tel and planned IR, optical and polarimetry programmes which are likely to be coordinated together in the last week of September, an HST scheduling around this time is sought, if possible. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 QS-TEL FOS/BL ACQ/PEA 4.3 G400H SCAN-STEP-Y=1.23,SEARCH-SIZE-X=1, 1 2 S ONBOARD ACQ FOR 2 SEQ 1-4 K SEARCH-SIZE-Y=3 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 QS-TEL FOS/BL ACQ/PEA 1.0-PAI G400H SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 1 2 S ONBOARD ACQ FOR 3 K R-A ,SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 3 QS-TEL FOS/BL ACQ/PEA 0.5-PAI G400H SCAN-STEP-X=0.29,SCAN-STEP-Y=0.29 1 10 S ONBOARD ACQ FOR 4-7 K R-A ,SEARCH-SIZE-X=3,SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 4 QS-TEL FOS/BL RAPID 1.0-PAI G160L READ-TIME=20,STEP-PATT=SINGLE 1 500 S R-A Comments: Use upper aperture to avoid 1500-1550 instrumental feature ------------------------------------------------------------------------------------------------------------------------------------ 5 QS-TEL FOS/BL RAPID 1.0-PAI G160L READ-TIME=20,STEP-PATT=SINGLE 1 2800 S R-A ------------------------------------------------------------------------------------------------------------------------------------ 6 QS-TEL FOS/BL RAPID 1.0-PAI G160L READ-TIME=20,STEP-PATT=SINGLE 1 2801 S R-A ------------------------------------------------------------------------------------------------------------------------------------ 7 QS-TEL FOS/BL RAPID 1.0-PAI G160L READ-TIME=20,STEP-PATT=SINGLE 1 2802 S R-A ------------------------------------------------------------------------------------------------------------------------------------ 6889( 6) - 08/13/96 14:22 - [ 3] Summary Form for Proposal 6889 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK RAPID ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCAN-STEP-Y=1.23 SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 SEARCH-SIZE-Y=2 SEARCH-SIZE-X=3 STEP-PATT=SINGLE READ-TIME=20 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO/DD ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category BINARIES AND STAR FORMATION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 23-SEP-96 AND 30-SEP-96 ONBOARD ACQ FOR 2 SEQ 1-4 NON-INT ONBOARD ACQ FOR 3 ONBOARD ACQ FOR 4-7 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G400H G160L ------------------------------------------------------------------------------------------------------------------------------------ Target Names QS-TEL ------------------------------------------------------------------------------------------------------------------------------------