6045( 0) - 07/18/95 19:37 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6045 Version: ********** Check-in Date: ********** 1.Proposal Title: The Masses of the O-type Binary 15 Monocerotis ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Hot Stars GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Douglas Gies Georgia State University CoI: Dr. W. Hartkopf Georgia State University N CoI: Mr. B. Mason Georgia State University N CoI: Dr. W. Bagnuolo Georgia State University N ------------------------------------------------------------------------------------ 6. Abstract The O-type star 15 Mon (HD 47839) was recently discovered to be a speckle and spectroscopic binary with an orbital period of 25 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 approaching periastron (1998.8) and continued spectroscopic and astrometric monitoring will lead to a definitive orbit and yield important information about the masses of O 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. ------------------------------------------------------------------------------------ 6045( 0) - 07/18/95 19:37 - [ 2] Observations Description ------------------------ Our goal is to obtain FGS TRANS mode measurements of the separation, position angle, and magnitude difference of 15 Mon once each year over the next three observing cycles. 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 10 scans in the TRANS mode of operation which should require less than 10 minutes exposure time. Because the orbit is still loosely defined, we wish to make observations at two scan orientations in the sky to yield high accuracy in the derived positions. This will require a spacecraft roll of less than 30 degrees. According to the Cycle 5 Phase I Proposal Instructions, such a manuever counts as a separate visit, but according to FGS Scientist Larry Taff (STScI), the roll manuever and two sets of scans should require no more than the 52 minutes of visibility during one orbit, so we estimate that an observation of 15 Mon can be accomplished in a single orbit. The Transfer Functions (TF) of the FGS with the F5ND filter have not yet been fully calibrated by STScI scientists, so we also request a single orbit to observe a reference single star, HR1399 (of similar brightness and color as 15 Mon), in conjunction with each observation of the main target. The reference TF will be used in the data reduction to accurately extract the binary components in the composite TF of 15 Mon (see Lattanzi et al. 1992, in Complementary Approaches to Double and Multiple Star Research, ASP Conf. Series 32, ed. McAlister & Hartkopf, San Francisco: ASP, 377). 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 ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6045( 0) - 07/18/95 19:37 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD47839 STAR, MAIN SEQUENCE O RA=06H 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 HD28149 STAR, B6-B9.5 V-IV RA=4H 24M 17.800S +/- 0.013S, B1950 V = 13.7 V = 5.53 +/- 0.02 DEC=+22D 53' 07.12" +/- 0.18" B-V = -0.10 +/- 0.02 TYPE = B7V Comments: SINGLE STAR, CALIBRATION TARGET Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) B1950 0.0005 -0.015 0.007 6045( 0) - 07/18/95 19:37 - [ 4] Visit: 01 Visit Requirements: ORIENT 52D TO 72D On Hold Comments: Additional Comments: ORIENTATIONS AT 90D, 180D, 270D TO ABOVE 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 3 F5ND SCANS=14, STEP- 1 1750S POS TARG 0,0 SIZE=0.3, DATA- RATE=32 Comments: 5000 SAMPLES PER SCAN ------------------------------------------------------------------------------------------------------------------------------------ 6045( 0) - 07/18/95 19:37 - [ 5] Visit: 02 Visit Requirements: ON HOLD On Hold Comments: PENDING DECISION AS STSCI CALIBRATION TARGET 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 HD28149 FGS TRANS 3 F5ND SCANS=14, STEP- 1 1750S POS TARG 0,0 SIZE=0.3, DATA- RATE=32 Comments: 5000 SAMPLES PER SCAN, CALIBRATION TARGET ------------------------------------------------------------------------------------------------------------------------------------ 6045( 0) - 07/18/95 19:37 - [ 6] Summary Form for Proposal 6045 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FGS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes TRANS ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCANS=14 STEP-SIZE=0.3 DATA-RATE=32 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Hot Stars ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 52D TO 72D POS TARG 0,0 ON HOLD ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F5ND ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD47839 HD28149 ------------------------------------------------------------------------------------------------------------------------------------