9646( 4) - 05/24/02 15:32 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9646 Version: 4 Check-in Date: 24-May-2002 15:32:25 1.Proposal Title: Wind Accretion and State Transitions in the Black Hole Binary Cyg X-1 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO/DD 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Douglas Gies Georgia State University Research Foundation CoI: Dr. Tom Bolton University of Toronto N CoI: Dr. Robert Fender University of Amsterdam N CoI: Dr. Lex Kaper University of Amsterdam N CoI: Ms. Virginia McSwain Georgia State University N CoI: Mr. James Thomson University of Toronto N CoI: Ms. Debra Wallace Georgia State University N CoI: Dr. Paul Wiita Georgia State University N ------------------------------------------------------------------------------------ 5. Abstract The black hole binary, Cyg X-1, is now (May 2002) in the high/soft X-ray state, the first one to occur since 1996. Models predict that this state corresponds to a high mass transfer phase in the binary, but several lines of observational evidence cast doubt on this assumption. The best test of this hypothesis is to observe the UV P Cygni lines of the supergiant that are formed in its wind outflow. We propose to obtain the first ever high resolution UV spectra of the system using STIS to determine (1) the mass loss rate and the dynamical (density and velocity) structure of the wind of the supergiant star in both X-ray states, and (2) how the X-ray source ionizes the wind. These spectra will be useful for many investigations and will form an important resource for many in the research community. ------------------------------------------------------------------------------------ 9646( 4) - 05/24/02 15:32 - [ 2] Observations Description ------------------------ Our primary goal is to measure the P Cygni type line profiles in the UV spectrum of Cyg X-1. The main features include N V 1240, Si IV 1400, and C IV 1550, and we need a resolving power of approximately 10, 000 in order to measure accurately the wind terminal velocity and profile distortions caused by X-ray ionization. This is best accomplished with STIS using the E140M echelle grating. This set up covers the entire range of interest at somewhat higher resolving power (R=45, 000 which we can rebin later to a lower resolution to increase the signal-to-noise ratio). We used the STIS Exposure Time Calculator with an input low resolution spectrum of Cyg X-1 obtained from IUE to determine that we would attain a S/N = 10 in the science exposure time available in 2 orbits (or S/N = 22 if the resolving power is degraded to 10, 000). This S/N ratio will meet the scientific requirements of the program. No HST spectroscopic observations of Cyg X-1 are listed in the archives. The observations would not exceed any MAMA count rate limit. Our strategy will be to obtain the FUV spectrum near the conjunction when the optical star is in the foreground and relatively unaffected by the high energy flux from the companion and its environs. A second visit and FUV observation will take place at the opposite conjunction phase when the relativistic companion is in the foreground and its effect on the wind lines of the O-star can be clearly observed. Real Time Justification ----------------------- We need to obtain the STIS spectra near the two conjunction phases of the binary during the current the high/soft state. Note that spectroscopic phase zero corresponds to maximum radial velocity of the O-supergiant, which occurs at HJD 2, 451, 356.6608 + 5.599829E. The high/soft states usually lasts a few months, and since the current one began in September, 2001, it is important to schedule these two visits as soon as possible. Both conjunction observations should be scheduled when the star is within +/- 36 degrees of the conjunction time in order to observe the greatest changes in the wind lines due to X-ray ionization. The second visit should occur within 1.5 orbital cycles of the first so that we can compare changes due to orbital orientation and not long term wind variations. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9646( 4) - 05/24/02 15:32 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HDE226868 STAR, SUPERGIANT O, MXB RA=19H 58M 21.67S +/- 0.02S, J2000 V = -7.0 V = 8.95+/-0.02 DEC=35D 12' 6.1" +/- 0.3", PLATE B-V = 0.84+/-0.02 -ID=004C E(B-V) = 1.06+/-0.1 TYPE=O9.5IAB F-CONT(1600)=23+/-2e-14 Coordinate Source: GUIDE_STAR_CATALOG Comments: Coordinates are from Hipparcos, ICRS(2000) RA = 19H 58M 21.6756S, DEC = +35D 12' 05.775", GSC: 2678 791 19 58 21.67 +35 12 6.1 0.3 8.79 0.41 1 03 004C 1 TFTFFFFF 1983.614 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1983.614 -0.000312 -0.00762 0.00058 9646( 4) - 05/24/02 15:32 - [ 4] Visit: 01 Visit Priority: Visit Requirements: PERIOD 5.599829 D AND ZERO-PHASE JD2451356.660800 SCHED 100% BEFORE 01-Jul- 2002 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 HDE226868 STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 1.0 S PHASE 0.15 TO 0.35 CD ------------------------------------------------------------------------------------------------------------------------------------ 2 HDE226868 STIS/F ACCUM 0.2X0.2 E140M 1425 1 2172 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 HDE226868 STIS/F ACCUM 0.2X0.2 E140M 1425 1 2676 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9646( 4) - 05/24/02 15:32 - [ 5] Visit: 02 Visit Priority: Visit Requirements: PERIOD 5.599829 D AND ZERO-PHASE JD2451356.660800 SCHED 100% AFTER 01 BY 1.7 D TO 9.5 D 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 HDE226868 STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 1.0 S PHASE 0.65 TO 0.85 CD ------------------------------------------------------------------------------------------------------------------------------------ 2 HDE226868 STIS/F ACCUM 0.2X0.2 E140M 1425 1 2172 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 HDE226868 STIS/F ACCUM 0.2X0.2 E140M 1425 1 2676 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9646( 4) - 05/24/02 15:32 - [ 6] Summary Form for Proposal 9646 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F25ND3 0.2X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO/DD ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PERIOD 5.599829 D AND ZERO-PHASE JD2451356.660800 SCHED 100% BEFORE 01-Jul-2002 PHASE 0.15 TO 0.35 PERIOD 5.599829 D AND ZERO-PHASE JD2451356.660800 SCHED 100% AFTER 01 BY 1.7 D TO 9.5 D PHASE 0.65 TO 0.85 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HDE226868 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------