5868( 0) - 07/18/95 18:22 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5868 Version: ********** Check-in Date: ********** 1.Proposal Title: The Mass of the Classical Cepheid T Mon ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Cool Stars GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Derck Massa Applied Research Corporation CoI: Dr. Nancy Evans York University Y CoI: Dr. K. Carpenter NASA Goddard Space Flight Center N CoI: Dr. R. Robinson Computer Sciences Corporation N ------------------------------------------------------------------------------------ 6. Abstract 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. ------------------------------------------------------------------------------------ 5868( 0) - 07/18/95 18:22 - [ 2] Observations 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 ------------------------- 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. ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: Dr. K. Carpenter*CODE 681*NASA Goddard Space Flight Cente*GREENBELT, MD 20771 Ship Via: UPS Email: evans@nereid.sal.ists.ca , ------------------------------------------------------------------------------------ 5868( 0) - 07/18/95 18:22 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD44990 STAR,COMPOSITE SPECTRAL RA = 06H 25M 13.01S +/- 0.01S, J2000 V = 27. V=6.1+/-0.5 TYPE,CEPHEID DEC = 07D 05' 8.5" +/- 0.1" B-V=1.2+/-0.3 E(B-V)=0.14 +/-0.02 F- CONT(1800)=1.6+/-0.3 E-13 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 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.000 0.0010 0.004 0.00 5868( 0) - 07/18/95 18:22 - [ 4] Visit: 01 Visit Requirements: 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 HD44990 HRS ACQ 2.0 MIRROR-N2 LOCATE=YES, 1 1.8S ONBOARD ACQ FOR 10 BRIGHT=RETURN, SEARCH-SIZE=3 Comments: STEP-TIME=0.20 SEC ------------------------------------------------------------------------------------------------------------------------------------ 10 HD44990 HRS ACQ/PEA 0.25 MIRROR-N2 1 5S ONBOARD ACQ FOR 12-48 KUP ------------------------------------------------------------------------------------------------------------------------------------ 12 WAVE HRS ACCUM SC2 G200M 1860.0 STEP-PATT=3 1 30S SEQ 12-18 NON-INT Comments: CALIB FOR 15 ------------------------------------------------------------------------------------------------------------------------------------ 15 HD44990 HRS ACCUM 0.25 G200M 1860.0 COMB=FOUR, STEP 2 380.8S -PATT=5, DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 18 WAVE HRS ACCUM SC2 G200M 1860.0 STEP-PATT=3 1 30S Comments: CALIB FOR 15 END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 22 WAVE HRS ACCUM SC2 G200M 1860.0 STEP-PATT=3 1 25.6S SEQ 22-28 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 25 HD44990 HRS ACCUM 0.25 G200M 1860.0 COMB=FOUR, STEP 7 326.4S -PATT=5, DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 28 WAVE HRS ACCUM SC2 G200M 1860.0 STEP-PATT=3 1 25.6S Comments: END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 32 WAVE HRS ACCUM SC2 G200M 1860.0 STEP-PATT=3 1 25.6S SEQ 32-38 NON-INT Comments: CALIB FOR 35 ------------------------------------------------------------------------------------------------------------------------------------ 35 HD44990 HRS ACCUM 0.25 G200M 1860.0 COMB=FOUR, STEP 7 326.4S -PATT=5, DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 38 WAVE HRS ACCUM SC2 G200M 1860.0 STEP-PATT=3 1 25.6S Comments: CALIB FOR 35 END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 42 WAVE HRS ACCUM SC2 G200M 1860.0 STEP-PATT=3 1 25.6S SEQ 42-48 NON-INT Comments: CALIB FOR 45 ------------------------------------------------------------------------------------------------------------------------------------ 45 HD44990 HRS ACCUM 0.25 G200M 1860.0 COMB=FOUR, STEP 7 326.4S -PATT=5, DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 48 WAVE HRS ACCUM SC2 G200M 1860.0 STEP-PATT=3 1 25.6S Comments: CALIB FOR 45 END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 5868( 0) - 07/18/95 18:22 - [ 5] Summary Form for Proposal 5868 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAKUP ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters LOCATE=YES BRIGHT=RETURN SEARCH-SIZE=3 STEP-PATT=3 DOPPLER=ON STEP-PATT=5 COMB=FOUR ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Cool Stars ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 10 ONBOARD ACQ FOR 12-48 SEQ 12-18 NON-INT SEQ 22-28 NON-INT SEQ 32-38 NON-INT SEQ 42-48 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G200M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD44990 WAVE ------------------------------------------------------------------------------------------------------------------------------------