7484( 10) - 06/25/99 09:50 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7484 Version: 10 Check-in Date: 25-Jun-1999 09:50:21 1.Proposal Title: The Masses of the O-type Binary 15 Monocerotis ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Douglas Gies Georgia State University CoI: Dr. B. Mason Georgia State University N CoI: Dr. W. Hartkopf Georgia State University N CoI: Dr. W. Bagnuolo Georgia State University N CoI: Dr. H. McAlister Georgia State University N CoI: Dr. W. McKibben Oxford College, Emory University N ------------------------------------------------------------------------------------ 5. Abstract The O-type star 15 Mon (HD 47839) was recently discovered to be a speckle and spectroscopic binary with an orbital period of 23.6 years. An analysis of both the radial velocity curve and astrometric orbit yields the masses of the components and distance to the system. Both radial velocity and astrometric measurements are scant at present, but the system is now close to periastron (1996.9) and continued spectroscopic and astrometric monitoring will lead to a definitive orbit and yield important information about the masses of O-type stars. FGS measurements of separation, position angle, and magnitude difference are needed to bridge the gap between current speckle observations and the next generation of optical interferometers. ------------------------------------------------------------------------------------ 7484( 10) - 06/25/99 09:50 - [ 2] Observations Description ------------------------ This is a Continuation Proposal for a long term program which was approved in Cycle 5 (and again in Cycle 6) for 2 orbits in each of Cycles 5 - 7. According to our working set of orbital elements, the binary will remain unresolved by ground-based speckle methods until 2000, and so we propose to extend the project into Cycle 8. Our goal is to obtain FGS TRANS mode measurements of the separation, position angle, and magnitude difference of 15 Mon once each year. We are aiming for a positional accuracy of a few mas and a photometric accuracy of 0.1 mag, both of which have been achieved in recent binary studies with the FGS (see Franz et al. 1992, in Complementary Approaches to Double and Multiple Star Research, ASP Conf. Series 32, ed. McAlister & Hartkopf [San Francisco: ASP], 369). Because of the relative brightness of the star, the observations will be made with the 5 mag neutral density filter, F5ND. We plan to obtain approximately 7 scans in the TRANS mode of operation which should require approximately 35 minutes exposure time. We estimate that an observation of 15 Mon can easily be accomplished in a single orbit. The Cycle 5 observations were successfully made in 1996 February. Our analysis of the 1996 scans indicates that maximum positional accuracy requires an extremely close match for the calibration Transfer Function (TF). There exists only a single set of scans made of a blue star (HD 28149) with the F5ND filter and FGS3 at the nominal central position (Holfeltz 1995, STScI FGS Instrument Science Report No. 31), and we have found that these TFs do not provide an ideal match to our observations of 15 Mon. Because we expect that the separation will be small during Cycles 6 and 7, we need very reliable calibration TFs to interpret the target scans, and we strongly advocate obtaining a calibration observation at the same time and in exactly the same way as the target observation. We selected the OB runaway star, Mu Col (HD 38666; HR 1996; spectral classification O9.5 V), as our new calibration source. This star has a similar magnitude and color (V=5.17, B-V= -0.28) as 15 Mon (V=4.65, B-V= -0.25), and appears to be a truly single star. It has constant radial velocity (Garmany, Conti, & Massey 1980, ApJ, 242, 1063), appears single in our speckle survey (no companion with a separation greater than 30 mas), and is not expected to be binary according to theories for the origin of runaway stars (Gies & Bolton, 1986, ApJS, 61, 419). The FGS calibration observations of Mu Col will be obtained in exactly the same way as those of 15 Mon and will require 1 HST orbit. There is also a distant visual companion to 15 Mon at 2.9 arcsec separation and a position angle of 213 degrees. We propose to make long scans to include this distant star as a secondary calibrator. Then, the scan orientation range is selected to avoid overlap of primary and distant star TFs and to assure a separation > 10 mas on one axis. The scan length is selected to include the distant star TF. Real Time Justification ----------------------- None Our group (plus collaborators) will be continuing a program of high S/N spectroscopy of 15 Mon over the next decade to derive an accurate radial velocity curve and mass ratio. The spectra will be obtained primarily with our Multiple- Telescope Telescope (at the GSU Hard Labor Creek Observatory near Atlanta), a 1-m equivalent aperture telescope with a fiber-fed spectrograph and CCD detector. Calibration Justification ------------------------- See "Observing_Description" section above. Additional Comments ------------------- ------------------------------------------------------------------------------------ 7484( 10) - 06/25/99 09:50 - [ 3] Data Distribution Paper Products: Media: DAT Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7484( 10) - 06/25/99 09:50 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD47839 STAR, MAIN SEQUENCE O RA=6H 38M 13.429S +/- 0.035S, B1950 V = 22.0 V = 4.65+/-0.02 DEC=09D 56' 37.02" +/- 0.15" B-V = -0.25+/-0.02 TYPE=O7V((F)) Comments: LONG PERIOD BINARY Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) B1950 0.0001 -0.007 0.001 2 HD38666 STAR, MAIN SEQUENCE O RA=5H 44M 08.324S +/- 0.013S, B1950 V = 109. V = 5.17+/-0.02 DEC=-32D 19' 27.47" +/- 0.18" B-V = -0.28+/-0.02 TYPE=O9.5V Comments: SINGLE STAR, CALIBRATION TARGET Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) B1950 0.0003 -0.025 0.000 7484( 10) - 06/25/99 09:50 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 90D TO 94D BETWEEN 1-FEB-1999 AND 1-MAY-1999 On Hold Comments: Additional Comments: ORIENT 150D TO 190D ALSO ACCEPTABLE, ORIENT 240D TO 280D ALSO ACCEPTABLE, ORIENT 330D TO 10D ALSO ACCEPTABLE Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD47839 FGS TRANS 1 F5ND SCANS=25,STEP-SIZE=0.6 1 2100 S POS TARG 0, 0 Comments: 11120 SAMPLES PER SCAN ------------------------------------------------------------------------------------------------------------------------------------ 7484( 10) - 06/25/99 09:50 - [ 6] Visit: 02 Visit Priority: Visit Requirements: GROUP 1-2 WITHIN 24H 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 HD38666 FGS TRANS 1 F5ND SCANS=25,STEP-SIZE=0.6 1 2100 S POS TARG 0, 0 Comments: 11120 SAMPLES PER SCAN, CALIBRATION TARGET ------------------------------------------------------------------------------------------------------------------------------------ 7484( 10) - 06/25/99 09:50 - [ 7] Visit: 51 Visit Priority: Visit Requirements: ORIENT 270D TO 284D ORIENT 0D TO 14D ORIENT 90D TO 104D BEFORE 30-SEP-1999 On Hold Comments: Additional Comments: ORIENT 0D TO 14D ALSO ACCEPTABLE, ORIENT 90D TO 104D ALSO ACCEPTABLE Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD47839 FGS TRANS 1 F5ND SCANS=24,STEP-SIZE=0.6 1 2016 S POS TARG 0, 0 Comments: 11120 SAMPLES PER SCAN ------------------------------------------------------------------------------------------------------------------------------------ 7484( 10) - 06/25/99 09:50 - [ 8] Summary Form for Proposal 7484 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations FGS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes TRANS ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCANS=25 STEP-SIZE=0.6 SCANS=24 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 90D TO 94D BETWEEN 1-FEB-1999 AND 1-MAY-1999 POS TARG 0, 0 GROUP 1-2 WITHIN 24H ORIENT 270D TO 284D ORIENT 0D TO 14D ORIENT 90D TO 104D BEFORE 30-SEP-1999 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F5ND ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD47839 HD38666 ------------------------------------------------------------------------------------------------------------------------------------