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PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only
ID: 6523
Version: 9
Check-in Date: 24-Feb-1997
09:51:47
1.Proposal Title:
The Masses of the O-type Binary 15 Monocerotis
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2. Scientific Category 3. Proposal For 4. Cycle
BINARIES AND STAR FOR GO 6
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5. Investigators
Contact?
PI: Dr. Douglas Gies GEORGIA STATE UNIVERSITY
CoI: Dr. W. Hartkopf Georgia State University N
CoI: Dr. B. Mason Georgia State University N
CoI: Dr. W. Bagnuolo Georgia State University N
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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-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.
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Observations Description
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This is a Continuation Proposal for a long term program which was approved in
Cycle 5 for 2 orbits in each of Cycles 5, 6, and 7. 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 current and next 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 16 scans in the TRANS mode of operation which should require less
than 34 minutes exposure time. We will make observations with a scan
orientation of ~ 45 degrees to the predicted binary position angle in order to
optimize the transfer function in both x and y axes. We estimate that an
observation of 15 Mon can easily be accomplished in a single orbit. The Cycle 5
observation was made on 1996 January 26. The Transfer Function (TF) of the FGS
with the F5ND filter needs to be well determined to analyze the observations,
so we also request a single orbit to observe a reference single star (of
similar brightness and color as 15 Mon) in conjunction with each observation of
the main target. This reference TF will be used in the data reduction procedure
to extract accurately 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). The calibration TF needs to made at the same reference position, with the
same neutral density filter, for a single star with approximately the same flux
distribution as our main target. We have selected the star Mu Col (HD38666,
HR1996; spectral type O9.5V) as our calibration source. This star has a similar
magnitude and color as 15 Mon, and appears to be a truly single star. There are
no known visual companions, and we have found no evidence of a companion in
multiple observations made with the CHARA speckle camera at the KPNO 4-m
telescope. We need to obtain calibration scans in the same way and at about the
same time as the 15 Mon scans.
Real Time Justification
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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
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See "Observing_Description" section above.
Additional Comments
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Data Distribution
Media: 8MM
Blocking Factor: 10
Ship To: PI_Address
Ship Via: UPS
Email:
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TARGET LIST a) Fixed Targets
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Tar| Target | Target | Target |Coord | Radial | Flux data
No | Name | Description | Position |Eqnx | Vel. |
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1 HD47839 STAR, MAIN SEQUENCE O RA=6H 38M 13.429S +/- B1950 V = 22.0 V = 4.65+/-0.02
0.035S,DEC=09D 56' 37.02" +/- B-V = -0.25+/-0.02
0.15" 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 +/- B1950 V = 109. V = 5.17+/-0.02
0.013S,DEC=-32D 19' 27.47" +/- B-V = -0.28+/-0.02
0.18" 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
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Visit: 01
Visit Requirements: ORIENT 221D TO 260D
On Hold Comments: <none>
Additional Comments: <none>
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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1 HD47839 FGS TRANS PRIME F5ND SCANS=7,STEP-SIZE=0.6 1 2125 S POS TARG 0,0
Comments: 17000 SAMPLES PER SCAN
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Visit: 02
Visit Requirements: GROUP 1-2 WITHIN 24H
On Hold Comments: <none>
Additional Comments: <none>
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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1 HD38666 FGS TRANS PRIME F5ND SCANS=7,STEP-SIZE=0.6 1 2125 S POS TARG 0,0
Comments: 17000 SAMPLES PER SCAN, CALIBRATION TARGET
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Summary Form for Proposal 6523
Item Used in this proposal
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Configurations FGS
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Opmodes TRANS
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Optional Parameters SCANS=7 STEP-SIZE=0.6
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Proposal Category GO
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Scientific Category BINARIES AND STAR FORMATION
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Special Requirements ORIENT 221D TO 260D POS TARG 0,0 GROUP 1-2 WITHIN 24H
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Spectral Elements F5ND
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Target Names HD47839 HD38666
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