! Hubble Space Telescope Cycle 5 (1995) Phase II Proposal Template ! $Id: 5854,v 9.1 1996/04/04 15:41:21 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: Cepheid Masses Proposal_Category: GO Scientific_Category: Cool Stars Cycle: 5 Investigators PI_name: Erika Bohm-Vitense PI_Institution: Astronomy Department, University of Washington CoI_Name: Nancy R.Evans CoI_Institution: Institute for Space and Terrestrial Sciences, North York Contact: ! Y or N (designate at most one contact) CoI_Name: Kenneth Carpenter CoI_Institution: NASA-Goddard Space Flight Center Contact: ! Y or N (designate at most one contact) CoI_Name: Rich Robinson CoI_Institution: Computer Science Corporation Abstract: ! Free format text (please update) This is a proposal for the third (and fourth) year of a three year proposal which was accepted for the last two years. The aim is to determine Cepheid masses for binaries with Cepheids. For 2 decades the Cepheid ``mass problem" has persisted: Mass determinations from standard evolutionary tracks and those from pulsation theory gave conflicting results. The luminosity of a Cepheid with given mass depends sensitively on the amount of convective overshoot above the core of the main sequence progenitor. Hence a good mass determination for a Cepheid with known luminosity measures the amount of convective overshoot. This knowledge is important for the interpretation of HR diagrams of populous clusters in the LMC and especially for age determinations. It is also necessary for the understanding of mixing processes in stars. IUE observations have revealed a number of Cepheid binaries with blue companions whose orbits have now been determined by groundbased observations. We propose to measure the orbital radial velocities of altogether 5 blue Cepheid companions for wavelengths shorter than 2000 A. The ratio of the orbital velocity amplitudes for the binary provides the mass ratio for the stars. The effective temperature for the companion is determined from its ultraviolet energy distribution. For main sequence stars this also determines its mass. With good GHRS spectra the velocity ratio and thereby the mass ratio can be determined with an accuracy of +/- 10% Questions ! Free format text (please update) Observing_Description: The purpose of this proposal is to measure the orbital velocities of main sequence companions for a representative sample of classical Cepheids, for which orbits are known. During Cycle 5 we would like to get second spectra for V350 Sgr and U Aql and a first spectrum for V636 Sco. The observations are spread over several observing cycles in order to observe the targets at maximum and minimum radial velocity. This will permit us to observe the whole amplitude to obtain maximum accuracy. At the same time it will eliminate any systematic errors in the velocity measurement because velocity differences will be measured. For V636 Sco and Y Car the phases of maximum or minimum Cepheid velocity will occur during Cycle 6. In Table 3 we list the observing windows for our targets. Within these windows the velocities differ from the optimum value by less than 2 km/s. The highest accuracy will be achieved if the observations can be done in the middle of these observing windows. We plan to use the GHRS with the 0.25" aperture to avoid errors due to imperfect centering in the large entrance aperture. Since high accuracy is so important for an accurate mass determination we think it is worth the extra observing time. We will use the G200M grating and observe the spectral region around 1860 Angstrom, which has some strong lines. A standard comparison star spectrum will have been obtained during cycle 4. This can then also be cross-correlated with the target star spectra to check the accuracy of the velocity determination. In order to obtain an accuracy of 10% (which we consider necessary to distinguish between different amounts of excess mixing) we require a velocity accuracy of 2 km/s. This corresponds to a wavelength accuracy of 0.2 diodes or better. Our measurements of the first Y Car spectrum have shown that this is possible, but accurate centering is necessary. This can be achieved best with the small entrance aperture. Our estimates for the necessary number of orbits takes this into consideration. The long exposures will be broken up into segments of 5 to 6 min. in order to minimize geomagnetic smearing. A wavelength calibration is necessary at the beginning and end of each exposure. We also would like to take one in the middle of one exposure in order to get some estimate of second order terms for the time dependence of the wavelength calibration. After accurate wavelength calibration exposures from the successive orbits will be coadded. Cross-correlation between them will give us some indication about the accuracy of our velocity measurements. The required exposure times were derived using the exposures from Cycle 4 with a signal to noise of about 6 and aiming at a signal to noise of about 10. Real_Time_Justification: We need to observe the Cepheids at the orbital phases of maximum and minimum radial velocity as given in Table 3, in order to measure the maximum possible velocity variation. For a given measuring accuracy of +/- 2 km/s this will give the highest measuring accuracy for the ratio of the orbital velocities. Highest accuracy will be achieved if the observations can be done in the middle of the windows. The orbital periods are typically a few years. If the appropriate phase is missed we have to wait for several years. Additional groundbased radial velocity measurements have been and will be done for improved orbital determinations fore the Cepheid. These will be continued past the time of our HST observations. Calibration_Justification: ! Move appropriate text from Real_Time_Justification We need a wavelength calibration at the beginning (or in the middle) and at the end of each exposure in order to get the wavelength accuracy needed for an accurate determination of the radial velocities. In order to accurately coadd the different subexposures we have to know the wavelength change as a funtion of time during the exposure, which means we also need at least once a wavelength calibration in the middle of one exposure in order to estimate the second order changes. Additional_Comments: Since in the end all exposures of a given target to be taken over several orbits have to be coadded we have been advised by Steve Hulbert that for a given set of wavelength calibrations the exposures should be taken without interruption, which means NON-INT, in order to achieve the velocity accuracy which is needed for a success of our program. !Fixed_Targets ! Section 5.1 ! Target_Number:1 ! Target_Name:HD172167-CALIB !Alternate_Names:HR7001,ALPHA-LYR ! Description:STAR, A0V ! Position:RA=18H 36M 56.13S +/-0.1S, ! Most common specification format is ! DEC=+38D 47' 01" +/-1" ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 ! Equinox:2000 ! RV_or_Z:-14.0 ! RA_PM:0.017096 ! Units are seconds of time per year ! Dec_PM:0.2900 ! Units are seconds of arc per year ! Epoch:2000 !Annual_Parallax:0.12 ! Flux:V=0.01, B-V=0.01, E(B-V)=0.0 ! Include at least V and B-V ! Comments:F-CONT(1860)=5.5E-9 !Fixed_Targets ! Section 5.1 ! Target_Number:2 ! Target_Name:HD91595 !Alternate_Names:Y-CAR-B ! Description:STAR, B9.5V ! Position:RA=10H 33M 10.90S +/-0.1S, ! Most common specification format is ! DEC=-58D 29' 55.7" +/-1", ! RA=0H 0M 0.00S +/- 0S, ! PLATE-ID=06AG ! DEC=0D 0' 0.0" +/- 0", ! ! PLATE-ID=0000 ! Equinox:2000 ! RV_or_Z: ! RA_PM:0.0011 ! Units are seconds of time per year ! Dec_PM:0.001 ! Units are seconds of arc per year ! Epoch:1987.2 !Annual_Parallax:0.001 ! Flux:V=11.93, B-V=0.01, E(B-V)=0.08, F-CONT(1860)=1.E-13 ! Include at least V and B-V ! Comments:We want to observe the B9.5V companion ! of the Cepheid Y Car, which has V=7.5 +/-1, ! B-V=0.7 +/-0.15 Fixed_Targets ! Section 5.1 Target_Number:3 Target_Name:HD183344 Alternate_Names:HR7402, U-AQL-B Description:STAR, A0-A3 V-IV ! Position:RA=19H 29M 21.37S +/-0.1S, ! DEC=-0.7D 02' 37.7", ! PLATE-ID=03UO Position:RA=19H 29M 21.42S +/-0.1S, DEC=-07D 02' 38.5" +/-1" ! PLATE-ID=56 !hipparcos, don't include ID Equinox:2000 RV_or_Z:V=-6.0 RA_PM:0.0014 ! Units are seconds of time per year Dec_PM:0.003 ! Units are seconds of arc per year Epoch:2000 Annual_Parallax:0.001 Flux:V=10.8 +/-1, B-V=0.34 +/-0.05, E(B-V)=0.35, F-CONT(1860)=9.E-14 ! Include at least V and B-V Comments:WE WANT TO OBSERVE THE A1V COMPANION OF THE CEPHEID U-AQL THE CEPHEID HAS V=6.5+/-1, B-V=1.10+/-0.15 Fixed_Targets ! Section 5.1 Target_Number:4 Target_Name:HD173297 Alternate_Names:V350-SGR-B Description:STAR, B6-B9.5 V-IV ! Position:RA=18H 45M 17.48S +/-0.1S, ! DEC=-20D 38' 50.8" +/-1", ! PLATE-ID=06AL Position:RA=18H 45M 17.52S +/-0.1S, DEC=-20D 38' 50.6" +/-1", PLATE-ID=060A !target closer to center of this plate Equinox:2000 RV_or_Z:V=0.0 RA_PM:0.0061 ! Units are seconds of time per year Dec_PM:-0.012 ! Units are seconds of arc per year Epoch:1987 Annual_Parallax:0.001 Flux:V=11.5, B-V=-0.05+/-0.05, E(B-V)=0.30+/-0.1, F-CONT(1860)=5.0E-14 ! Include at least V and B-V Comments:WE WANT TO OBSERVE THE B9V COMPANION OF THE CEPHEID V350 SGR, which has V=8.0+/-1 Fixed_Targets ! Section 5.1 Target_Number:5 Target_Name:HD156979 Alternate_Names:V636-SCO-B Description:STAR, A0-A3 V-IV ! Position:RA=17H 22M 46.50S +/-0.1S, ! DEC=-45D 36' 51.10" +/-1", ! PLATE-ID=06AQ Position:RA=17H 22M 46.47S +/-0.1S, DEC=-45D 36' 51.30" +/-1" ! PLATE-ID=56 !hipparcos, don't include ID Equinox:2000 RV_or_Z:V=1.0 RA_PM:-0.001 ! Units are seconds of time per year Dec_PM:0.00 ! Units are seconds of arc per year Epoch:2000 Annual_Parallax:0.001 Flux:V=11.4, B-V=0.15, E(B-V)=0.20, F-CONT(1860)=7.E-14 ! Include at least V and B-V Comments:WE WANT TO OBSERVE THE A0V COMPANION OF THE CEPHEID V636-SCO, WHICH HAS V-6.8+/-1, B-V=0.8+/-0.1 ! 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:PCS MODE F BETWEEN 11-APR-95 AND 11-AUG-95 ! 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