9183( 7) - 08/20/01 09:41 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9183 Version: 7 Check-in Date: 20-Aug-2001 09:40:57 1.Proposal Title: Completing the Astrometric Orbit for a Pair of Pre-Main Sequence Low-Mass Stars ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: David Soderblom Space Telescope Science Institute CoI: Dr. Fritz Benedict University of Texas at Austin N CoI: Dr. Otto Franz Lowell Observatory N CoI: Dr. David Latham Harvard-Smithsonian Center for N Astrophysics CoI: Dr. Guillermo Torres Harvard-Smithsonian Center for N Astrophysics CoI: Dr. Lawrence Wasserman Lowell Observatory N CoI: Dr. Todd Henry Georgia State University N CoI: Dr. Ed Nelan Space Telescope Science Institute N CoI: Dr. Lionel Siess Laboratoire d'Astrophysique de Grenoble N ------------------------------------------------------------------------------------ 5. Abstract During the past two cycles we have pushed the limits of the FGSs to resolve a visual binary that is part of the closest system of pre-main sequence stars: HD 98800. The system is 50 pc away and this binary has a period just under a year, meaning the separation is about 20 milliarcsec. The two stars have similar brightnesses. The goal is to determine an astrometric orbit which, when combined with radial velocity observations, leads to the first dynamically-determined masses for low-mass pre-main sequence stars. We have succeeded in resolving the pair of stars with FGS1R, but not at all points in the orbit. Now that we have some FGS data in hand, we know the orbit well enough to fill in the missing pieces. With a full data set we can determine the stellar masses to within about 5\ FGS1R can resolve the Ba-Bb pair and can determine the relative orbit and luminosities for the two components. In this program we propose to complete the orbit solution for the HD 98800 Ba-Bb pair by obtaining five visits near apastron. ------------------------------------------------------------------------------------ 9183( 7) - 08/20/01 09:41 - [ 2] Observations Description ------------------------ We will use FGS1R in TRANS and POS mode for this program because that can significantly improve the solution achieved. FGS1R will be used in TRANS mode to measure the separations and position angles of HD 98800 Ba-Bb. Because the period is only 315 days, the remaining observations span five months and can all be done in Cycle 10 (apastron will occur near day 2001.330). Also, TRANS observations measure the magnitude difference of the components to +/- 0.1 mag (Henry et al. 1999), which is helpful for better constraining the models in the analysis phase. Earlier TRANS observations show that the brightness difference between Ba and Bb is ~1.9 mag. Co-Is Franz and Wasserman are experienced in the reduction and analysis of FGS TRANS mode observations. TRANS mode observations combined with ground-based spectroscopy lead directly to the masses of the two stars. The spectroscopic orbit alone yields M \sin^3 i for each component (Ba and Bb), and the inclination angle, i, comes from the TRANS mode measures. The minimum masses already determined from spectroscopy (Torres et al. 1995), together with placement on mass tracks (Soderblom et al. 1998), mean that i lies between 60 and 70 degrees. Note that the spectroscopic masses have uncertainties of about 6\ of 2 degrees (which is eminently achievable), the spectroscopic errors dominate, but will be lessened by our better radial velocity curves. TRANS mode observations yield a semi-major axis (a), the relative orbit, and, when combined with the radial velocity observations, also provide an orbital parallax. We will also use FGS1R in POS mode to define the absolute orbit by placing the system in a grid of surrounding reference stars. POS observations will allow us to refine the parallax to 0.5 mas (about six times better than the 2.86 m as error of Hipparcos). That helps constraint the luminosities. Also, the POS mode solution for the masses is independent of the TRANS mode solution and so provides a critical check of systematic error. Finally, this system has extraordinarily complex motions because there are four stars, all with orbital motion, and all moving across the sky with appreciable proper motion. POS mode data help to provide a significantly better solution for the many variables. In this program, the CfA Co- Is are providing ground- based observations of the radial velocities of the HD 98800 system, as well as their TRICOR software, which is a three-dimensional cross-correlation technique well-suited to complex spectra. The Texas and Lowell groups are, of course, experienced in the reduction and analysis of FGS data, especially in the demanding use we propose here. Dr. Siess will provide his models of pre-main sequence stars that will be used in the analysis, and the PI will direct the program and provide additional Keck spectra of the system to better determine key astrophysical parameters of the individual stars. Real Time Justification ----------------------- Spacing of the observations throughout Cycle 10 is important in order to map the orbit effectively. Five observations spaced by about a month each is needed, centered on apastron (day 2001.330). Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9183( 7) - 08/20/01 09:41 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD98800 STAR, K V-IV RA=11H 22M 5.2898S +/- 0.2", J2000 V = 15.5+/-0.05 DEC=-24D 46' 39.7639" +/- 0.2" Coordinate Source: PPM_STAR_CATALOGUE Comments: binary nature reduces fringe visibility. Hence we set V=15.5, even though V=9.1, to insure fringe capture in POS mode. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 -0.00627 -0.0337 0.2143 2 HD98800-REF- STAR RA=11H 21M 57.05S +/- 0.5", DEC= J2000 V = 10.3+/-0.2 4 -24D 43' 35.54" +/- 0.5" Coordinate Source: PPM_STAR_CATALOGUE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 0.0015 -0.065 0.0 3 HD98800-REF- STAR RA=11H 22M 5.54S +/- 0.5", DEC=- J2000 V = 15.1+/-0.2 2 24D 45' 55.55" +/- 0.5" Coordinate Source: OTHER_SOURCE 4 HD98800-REF- STAR, CALIBRATION RA=11H 22M 14.81S +/- 0.5", DEC= J2000 V = 15.1+/-0.2 3 -24D 49' 5.84" +/- 0.5" Coordinate Source: OTHER_SOURCE 9183( 7) - 08/20/01 09:41 - [ 4] Visit: 01 Visit Priority: Visit Requirements: BETWEEN 20-Dec-2001 AND 25-Dec-2001 SCHED 70% ORIENT 300.6D TO 300.6D 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 HD98800 FGS TRANS PRIME F583W SCANS=15,STEP-SIZE=1 1 750 S SEQ 1-100 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 10 HD98800 FGS POS PRIME F583W FES-TIME=0.05 1 30 S ------------------------------------------------------------------------------------------------------------------------------------ 20 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -2 ------------------------------------------------------------------------------------------------------------------------------------ 30 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -3 ------------------------------------------------------------------------------------------------------------------------------------ 40 HD98800-REF FGS POS PRIME F583W 1 30 S SAME POS AS 10 -4 ------------------------------------------------------------------------------------------------------------------------------------ 50 HD98800 FGS POS PRIME F583W FES-TIME=0.05 1 30 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 70 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -2 ------------------------------------------------------------------------------------------------------------------------------------ 80 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -3 ------------------------------------------------------------------------------------------------------------------------------------ 90 HD98800-REF FGS POS PRIME F583W 1 30 S SAME POS AS 10 -4 ------------------------------------------------------------------------------------------------------------------------------------ 100 HD98800 FGS POS PRIME F583W FES-TIME=0.05 1 30 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 9183( 7) - 08/20/01 09:41 - [ 5] Visit: 02 Visit Priority: Visit Requirements: BETWEEN 20-Dec-2001 AND 25-Dec-2001 SCHED 70% ORIENT 292.5D TO 348.5D 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 HD98800 FGS TRANS PRIME F583W SCANS=15,STEP-SIZE=1 1 750 S SEQ 1-100 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 10 HD98800 FGS POS PRIME F583W FES-TIME=0.05 1 30 S ------------------------------------------------------------------------------------------------------------------------------------ 20 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -2 ------------------------------------------------------------------------------------------------------------------------------------ 30 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -3 ------------------------------------------------------------------------------------------------------------------------------------ 40 HD98800-REF FGS POS PRIME F583W 1 30 S SAME POS AS 10 -4 ------------------------------------------------------------------------------------------------------------------------------------ 50 HD98800 FGS POS PRIME F583W FES-TIME=0.05 1 30 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 70 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -2 ------------------------------------------------------------------------------------------------------------------------------------ 80 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -3 ------------------------------------------------------------------------------------------------------------------------------------ 90 HD98800-REF FGS POS PRIME F583W 1 30 S SAME POS AS 10 -4 ------------------------------------------------------------------------------------------------------------------------------------ 100 HD98800 FGS POS PRIME F583W FES-TIME=0.05 1 30 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 9183( 7) - 08/20/01 09:41 - [ 6] Visit: 03 Visit Priority: Visit Requirements: BETWEEN 27-Jan-2002 AND 02-Feb-2002 SCHED 70% ORIENT 292.5D TO 348.5D 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 HD98800 FGS TRANS PRIME F583W SCANS=15,STEP-SIZE=1 1 750 S SEQ 1-100 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 10 HD98800 FGS POS PRIME F583W FES-TIME=0.05 1 30 S ------------------------------------------------------------------------------------------------------------------------------------ 20 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -2 ------------------------------------------------------------------------------------------------------------------------------------ 30 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -3 ------------------------------------------------------------------------------------------------------------------------------------ 40 HD98800-REF FGS POS PRIME F583W 1 30 S SAME POS AS 10 -4 ------------------------------------------------------------------------------------------------------------------------------------ 50 HD98800 FGS POS PRIME F583W FES-TIME=0.05 1 30 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 70 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -2 ------------------------------------------------------------------------------------------------------------------------------------ 80 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -3 ------------------------------------------------------------------------------------------------------------------------------------ 90 HD98800-REF FGS POS PRIME F583W 1 30 S SAME POS AS 10 -4 ------------------------------------------------------------------------------------------------------------------------------------ 100 HD98800 FGS POS PRIME F583W FES-TIME=0.05 1 30 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 9183( 7) - 08/20/01 09:41 - [ 7] Visit: 04 Visit Priority: Visit Requirements: BETWEEN 25-Feb-2002 AND 04-Mar-2002 SCHED 70% ORIENT 292.5D TO 348.5D 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 HD98800 FGS TRANS PRIME F583W SCANS=15,STEP-SIZE=1 1 750 S SEQ 1-100 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 10 HD98800 FGS POS PRIME F583W FES-TIME=0.05 1 30 S ------------------------------------------------------------------------------------------------------------------------------------ 20 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -2 ------------------------------------------------------------------------------------------------------------------------------------ 30 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -3 ------------------------------------------------------------------------------------------------------------------------------------ 50 HD98800 FGS POS PRIME F583W FES-TIME=0.05 1 30 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 70 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -2 ------------------------------------------------------------------------------------------------------------------------------------ 80 HD98800-REF FGS POS PRIME F583W 1 52 S SAME POS AS 10 -3 ------------------------------------------------------------------------------------------------------------------------------------ 100 HD98800 FGS POS PRIME F583W FES-TIME=0.05 1 30 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 9183( 7) - 08/20/01 09:41 - [ 8] Visit: 05 Visit Priority: Visit Requirements: BETWEEN 28-Apr-2002 AND 02-May-2002 SCHED 70% 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 HD98800 FGS TRANS PRIME F583W SCANS=36,STEP-SIZE=1 1 1800 S POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 9183( 7) - 08/20/01 09:41 - [ 9] Summary Form for Proposal 9183 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PRIME ------------------------------------------------------------------------------------------------------------------------------------ Configurations FGS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes TRANS POS ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCANS=15 STEP-SIZE=1 FES-TIME=0.05 SCANS=36 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 20-Dec-2001 AND 25-Dec-2001 SCHED 70% ORIENT 300.6D TO 300.6D SEQ 1-100 NON-INT SAME POS AS 10 BETWEEN 20-Dec-2001 AND 25-Dec-2001 SCHED 70% ORIENT 292.5D TO 348.5D BETWEEN 27-Jan-2002 AND 02-Feb-2002 SCHED 70% ORIENT 292.5D TO 348.5D BETWEEN 25-Feb-2002 AND 04-Mar-2002 SCHED 70% ORIENT 292.5D TO 348.5D BETWEEN 28-Apr-2002 AND 02-May-2002 SCHED 70% POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F583W ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD98800 HD98800-REF-2 HD98800-REF-3 HD98800-REF-4 ------------------------------------------------------------------------------------------------------------------------------------