! Hubble Space Telescope Cycle 5 (1995) Phase II Proposal Template ! $Id: 5868,v 4.1 1995/06/13 15:09:31 pepsa Exp $ ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Karla Peterson ! Phone: 410 338-4774, E-mail: peterson@stsci.edu ! ! This partially completed template was generated from your Phase I proposal. ! Proposal_Information ! Section 4 Title: The Mass of the Classical Cepheid T Mon Proposal_Category: GO Scientific_Category: Cool Stars Cycle: 5 Investigators PI_name: Derck Massa PI_Institution: Applied Research Corporation CoI_Name: Dr. Nancy Evans CoI_Institution: York University Contact: Y ! Y or N (designate at most one contact) CoI_Name: Dr. K. Carpenter CoI_Institution: NASA Goddard Space Flight Center Contact: N ! Y or N (designate at most one contact) CoI_Name: Dr. R. Robinson CoI_Institution: Computer Sciences Corporation Contact: N ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) This is a proposal to derive the mass of the long period (27^d) binary Cepheid T Mon (=HD 44990). Because it is a high luminosity star, it is particularly relevant to the stars used in extragalactic distance calibration. We will measure the velocity of the companion using a G200M spectrum in a wavelength region uncontaminated by the Cepheid (1800 Angstrom) with an accuracy approaching 1 kms. Since we are continuing to measure the change of the orbital velocity of the Cepheid from the ground, the ratio of the change of the orbital velocities of the Cepheid and the companion at two epochs is the inverse mass ratio. Combining the mass ratio with the mass of the companion from IUE spectral type yields the mass of the Cepheid. The first GHRS velocity will be used to determine the mass ratio using IUE data from 1985. A subsequent HST velocity in 5 to 10 years will bring major improvement to the accuracy of the mass ratio. We stress that from arguments about the observed orbital motion, the current epoch is a window of opportunity to observe the phase of minimum Cepheid orbital velocity which will not recur for at least 100 years. In addition, the fact that the stars are probably near periastron means that the mass ratio can be determined more quickly than at other phases. In the future, the system can be resolved but the mass ratio from this proposal is necessary to interpret these observations. Questions ! Free format text (please update) Observing_Description: The purpose of this proposal is to measure the velocity of the T Mon. In order to get the highest velocity accuracy possible with the G200M grating, we will include a wavelength calibration at the beginning and end of each orbit. We want to observe from 1840 to 1880 Angstrom, a region selected for a previous study of Cepheid masses because the A0 V companion has numerous lines in this region. Since this is the same region as used in the previous proposal, we will be able to use the same standard star (Alpha Lyr) for comparison, since it is to be observed with a wavelength calibration to insure wavelength accuracy. T Mon and the standard star will be cross-correlated in order to determine the velocity difference between them. The estimated accuracy of a velocity from a single line in this configuration is 2 kms. However, since the spectral region we have selected contains a number of lines, the accuracy for cross-correlation should approach 1 kms. In reducing previous Cepheid observations, it has been found that the observing seqments (to reduce geomagnetic smearing) can be added by assuming a linear relation between wavelength calibrations (since the individual exposures are too noisy to align by cross- correlation). The flux of T Mon B at 1850 Angstrom is known from an IUE spectrum. We have determined our exposure time in order to get S/N of 11, which should give us the required velocity accuracy in the cross-correlation (1 kms). Real_Time_Justification: none Calibration_Justification: ! Move appropriate text from Real_Time_Justification The success of the proposal depends on the accuracy with which the wavelength (velocity) is known. For this reason, we request wavelength calibrations at the beginning and end of the observations for each orbit. Evans has been obtaining radial velocity observations of T Mon at David Dunlap Observatory since 1970. This program will be continued, with particular emphasis on getting solid coverage of orbital velocity minimum. Additional_Comments: These observations must be obtained in 4 contiguous orbits. Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: HD44990 Alternate_Names: GSC0145-00875, T-MON Description: STAR,COMPOSITE SPECTRAL TYPE,CEPHEID Position: RA = 06H 25M 13.01S +/- 0.01S, DEC = 07D 05' 8.5" +/- 0.1", Equinox: J2000 RV_or_Z: V = 27. RA_PM: 0.0010 ! Units are seconds of time per year Dec_PM: 0.004 ! Units are seconds of arc per year Epoch: 2000.000 Annual_Parallax: 0.00 Flux: V=6.1+/-0.5, B-V=1.2+/-0.3 E(B-V)=0.14 +/-0.02 F-CONT(1800)=1.6+/-0.3 E-13 ! Include at least V and B-V Comments: This is a binary Cepheid system. The Cepheid dominates at visual wavelengths so V mag can change by +/- 0.5 mag; the A0 companion dominates at the region where observations are to be made. Coordinates are from Hipparcos INCA ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number: 1 Visit_Requirements: ! Section 7.1 ! Uncomment or copy visit level special requirements needed ! Most of these requirements (including ORIENT) will limit scheduling ! PCS MODE [Fine | Gyro] ! GUIDing TOLerance ! ORIENTation TO ! ORIENTation TO FROM ! ORIENTation TO FROM NOMINAL ! SAME ORIENTation AS ! CVZ ! PARallel ! AFTER [BY [TO ]] ! AFTER ! BEFORE ! BETWEEN AND ! GROUP WITHIN