9449( 5) - 07/18/02 12:32 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9449 Version: 5 Check-in Date: 18-Jul-2002 12:31:12 1.Proposal Title: UV Spectrum of the Massive X-ray Binary LS 5039 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Douglas Gies Georgia State University Research Foundation CoI: Dr. Lex Kaper University of Amsterdam N CoI: Ms. Virginia McSwain Georgia State University N CoI: Dr. Paul Wiita Georgia State University N CoI: Dr. David Wingert Georgia State University N ------------------------------------------------------------------------------------ 5. Abstract LS 5039 is a massive X-ray binary with non-thermal radio emission, relativistic jets, and probably high energy Gamma- ray emission. It appears to be one of the closest of the Galactic microquasars, stellar-sized engines that produce relativistic jets like extragalactic quasars. We recently discovered that the system is a 4.1 day binary with a very eccentric orbit (indicating large mass loss in the supernova event that gave birth to the system). The companion is probably a neutron star, but a black hole companion is viable if the system inclination is small. Here we propose to obtain the first UV observations of the binary to determine fundamental properties about the O6.5 V((f)) optical star and the mass transfer process. The UV spectrophotometry will allow us to measure accurately the interstellar extinction and system distance, and the unreddened spectrum will provide information on the optical star's effective temperature, spectral classification, and surface abundances. The stellar wind lines in the FUV provide the means to measure the O- star's wind terminal velocity and mass loss rate, and these parameters will allow us to determine if the X-ray luminosity can be generated by wind accretion alone. We plan to observe these wind lines at both orbital conjunction phases to search for evidence of changes in the wind structure caused by proximity to the X-ray source's radiation field, accretion disk wind, and jets. ------------------------------------------------------------------------------------ 9449( 5) - 07/18/02 12:32 - [ 2] Observations Description ------------------------ Our primary goals are to (1) obtain the flux distribution over the range 1200 - 3100 Angstrom (for determination of the stellar effective temperative and extinction), (2) identify the main line features in the UV spectrum to search for evidence of abundance anomalies, and (3) model the P Cygni wind lines (to determine the mass loss rate and search for the Hatchett-McCray effect). The main wind features observed in O7 V stars are the N V 1240 and C IV 1550 doublets, and their absorption troughs are expected to extend blueward to -2000 km/s (Howarth & Prinja 1989). Thus, we can study the profiles of the wind lines in relatively low resolution spectra, and we propose here to make these spectra using STIS/FUV with the G140L grating (1150 - 1730 Angstrom with a resolution of Lambda / Delta Lambda = 1000) and STIS/NUV with the G230L grating (1570- 3180 Angstrom with a resolution of Lambda / Delta Lambda = 500). We plan to use the 52X0.05 aperture to obtain the best resolution (2 pixel) with the MAMA detectors. Our strategy will be to obtain the combined FUV/NUV spectra 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. There exist no measurements at present of the UV flux of LS 5039. Instead, we relied on optical estimates of the star's spectral energy distribution and reddening to estimate the required exposure times (using the STIS Exposure Time Calculator). The star has a visual magnitude of V=11.3 (Marti et al. 1998), and the reddening lies in the range E(B-V)=0.8 - 1.26 (Motch et al. 1997) (we conservatively adopted the larger value in our calculations). We then assumed that the UV spectrum looks similar to that of a model O7 V star (Kurucz fluxes) with this reddening and normalized to the V magnitude. We used the STIS ETC to find the integrated counts and S/N per resolution element for each portion of the planned visits. The first visit would begin with a 34 minute FUV exposure in the first orbit, followed by 30 minute FUV and 10 minute NUV exposures in the second orbit. This would yield a S/N ratio in the range 20 - 60 in the NUV spectrum and 20 - 50 in the FUV spectrum. This is much better than what was possible in similar studies done in the past with the International Ultraviolet Explorer Satellite (S/N ~ 10), and these exposure times should easily fulfill our science needs. The second visit at the other conjunction phase would consist of a single FUV exposure of 34 minutes duration (yielding comparable S/N). The observations would not exceed any MAMA count rate limit. The entire program would require 3 orbits. Real Time Justification ----------------------- We need to obtain the STIS spectra near the O-star inferior conjunction (two orbits) and superior conjunction (one orbit). The orbital ephemeris from our work (McSwain et al. 2001) is HJD 2, 451, 822.12 + 4.117E where phase zero corresponds to periastron. We find an eccentricity e=0.41 and a longitude of periastron Omega = 217 degrees, and we can use these values to find the orbital phases corresponding to the conjunctions. The inferior conjunction observation should be scheduled when the star is within +/- 30 degrees of the conjunction in order to observe the portion of the wind unaffected by the X-ray source. This occurs shortly after periastron between orbital phases 0.025 and 0.109 (corresponding to an 8.3 hour observing window each orbital period). The superior conjunction observation should occur closer to the time of conjunction (+/- 20 degrees) in order to observe the maximum changes in the wind line profiles. This orientation occurs between phases 0.686 and 0.836 (yielding an 9449( 5) - 07/18/02 12:32 - [ 3] observing window of 14.8 hours duration each period). 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 ------------------- ------------------------------------------------------------------------------------ 9449( 5) - 07/18/02 12:32 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 LS5039 STAR, MAIN SEQUENCE O, RA=18H 26M 15.07S +/- 0.02S, J2000 V = 4.6 V = 11.32+/-0.02 MXB DEC=-14D 50' 54.4" +/- 0.3", B-V = 0.85+/-0.02 PLATE-ID=064B E(B-V) = 1.2+/-0.1 TYPE=O6.5V((F)) F-CONT(1600)=31+/-4e-15 Coordinate Source: GUIDE_STAR_CATALOG Comments: Coordinates are from GSC, ICRS(2000) RA = 18H 26M 15.0565S, DEC = -14D 50' 54.260" Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) B1986.653 0.000324 -0.0106 0.00034 9449( 5) - 07/18/02 12:32 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PERIOD 4.12078 D AND ZERO-PHASE JD2452446.6615 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 LS5039 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.1 S PHASE 0.025 TO 0.109 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 LS5039 STIS/C ACQ/PEA 52X0.05 MIRROR 1 0.1 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 LS5039 STIS/F ACCUM 52X0.05 G140L 1425 1 2087 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 LS5039 STIS/F ACCUM 52X0.05 G140L 1425 1 1814 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 LS5039 STIS/N ACCUM 52X0.05 G230L 2376 1 600 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9449( 5) - 07/18/02 12:32 - [ 6] Visit: 02 Visit Priority: Visit Requirements: PERIOD 4.12078 D AND ZERO-PHASE JD2452446.6615 AFTER 01 BY 2.3 D TO 7.5 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 LS5039 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.1 S PHASE 0.686 TO 0.836 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 LS5039 STIS/C ACQ/PEA 52X0.05 MIRROR 1 0.1 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 LS5039 STIS/F ACCUM 52X0.05 G140L 1425 1 2087 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9449( 5) - 07/18/02 12:32 - [ 7] Summary Form for Proposal 9449 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.05 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PERIOD 4.12078 D AND ZERO-PHASE JD2452446.6615 PHASE 0.025 TO 0.109 PERIOD 4.12078 D AND ZERO-PHASE JD2452446.6615 AFTER 01 BY 2.3 D TO 7.5 D PHASE 0.686 TO 0.836 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L G230L ------------------------------------------------------------------------------------------------------------------------------------ Target Names LS5039 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 2376 ------------------------------------------------------------------------------------------------------------------------------------