6714( 5) - 06/28/96 14:50 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6714 Version: 5 Check-in Date: 28-Jun-1996 14:44:56 1.Proposal Title: Be + HELIUM STAR BINARIES ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle BINARIES AND STAR FOR GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Douglas Gies GEORGIA STATE UNIVERSITY CoI: Dr. G. Peters University of Southern California N CoI: Dr. W. Bagnuolo Georgia State University N CoI: Mr. A. Kaye Georgia State University N CoI: Ms. L. Penny Georgia State University N CoI: Ms. M. Thaller Georgia State University N ------------------------------------------------------------------------------------ 6. Abstract Mass transfer during the evolution of intermediate-mass stars in a close binary system can result in a rejuvenated and spun- up secondary star which can appear as a rapidly rotating Be star. Models suggest that many bright Be stars may be binaries with unseen, stripped-down, helium star companions. One of the best candidates for such systems is the long period binaries Phi Per (127 d). We have recently used the Doppler tomography algorithm with IUE high dispersion spectra to reconstruct the individual spectra of the Phi Per system, and we find a weak secondary spectrum that resembles that of a hot subdwarf. Here we propose to obtain high S/N ratio spectra of this binaries with the GHRS at 3 orbital phases with differing orbital Doppler shifts. These spectra will allow us to detect and measure directly the secondary's weak spectral lines in the composite spectrum, which in turn will provide estimates of the mass ratio, the UV intensity ratio, and secondary projected rotational velocity. By combining results from all 3 spectra, we can reconstruct a higher S/N spectrum of the secondary star alone, which will help determine the temperature, gravity, and chemical abundance of the companion. This program will provide fundamental data on the nature of the stripped-down companion, and will yield the first direct detection of a binary that fills the evolutionary gap between systems of massive main sequence stars and the Be/X-ray binaries. ------------------------------------------------------------------------------------ 6714( 5) - 06/28/96 14:50 - [ 2] Observations Description ------------------------ Our goal is to obtain GHRS spectra of our targets at 3 orbital phases of relatively large orbital Doppler shift (especially near quadratures). Because the velocity shifts are of the order of 100 km/s and the profile widths are similar or larger, we can use the moderate dispersion G160M grating and Large Science Aperture. We plan to observe in two main spectral regions: (1) between 1356 and 1392 Angstroms where the hot helium stars should have many strong lines of Fe V, O V, and N IV; the Be star spectra, on the other hand, are relatively featureless in this region; and (2) between 1630 and 1664 Angstroms to record lines of He II 1640 and Fe IV (plus the strong interstellar line C I 1657). A comparison of the Fe ions in these two regions will help establish the effective temperature, and we will be able to estimate abundances for He, N, O, and Fe. We also wish to obtain a single exposure in the 1735 Angstrom region to record the important nitrogen features, N IV 1718 and N III 1748, 1752. The line depths in the spectrum of the helium star should be ~ 50% of the secondary flux, and thus for a 5 sigma detection we need observations of the composite spectrum with a S/N ratio given by 10/r, where r=F_s/F_p, the UV flux ratio. Then for S/N =1000, we should be able to detect secondaries that contribute only 1% of the UV flux (Delta m_UV = 5). Our current flux ratio estimate for Phi Per is r=0.14, so the final S/N ratio of the reconstructed secondary spectrum should reach 200 (a sqrt(n) improvement occurs through tomographic reconstruction of n composite spectra). Fortunately, the target is bright, and count rates (per pixel per sec) are given below based on UV fluxes from the TD- 1 satellite. Exposure times (given in minutes) for S/N = 1000 range from 14 to 32 minutes. TABLE - COUNT RATES AND EXPOSURE TIMES Lambda (Angstroms) Counts Exp. 1374 1190 14 1647 526 32 We need to make a minimum of 3 observations at differing velocity shifts in order to use the Doppler tomography algorithm to reconstruct the individual spectra. We have been granted time in Cycle 5 to obtain 2 GHRS observations of Phi Per in the 1374 Angstrom region only, so we need 2 additional observations of the 1647 Angstrom region (2 orbits) plus one further observation of both regions (2 orbits). Thus we are requesting a total of 4 orbits to complete this program. The spectra need to be made at 3 differing orbital phases. There are several orbital cycles of Phi Per during the available time for GHRS in Cycle 6, so there will be many scheduling options to complete the observations. Our group (plus collaborators) will be pursuing a program of high S/N optical spectroscopy of these Be stars over the next year to derive accurate radial velocities for the primaries and to follow changes in the Balmer emission lines formed in the disks. 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 (Bagnuolo et al. 1990, PASP, 102, 604). Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6714( 5) - 06/28/96 14:50 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6714( 5) - 06/28/96 14:50 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD10516 STAR, B0-B2 V-IV, BE, RA=1H 43M 39.63S +/- J2000 V = 1 V = 4.07+/-0.02 INTERACTING BINARY 0.004S,DEC=50D 41' 19.5" +/- B-V = -0.04+/-0.02 0.04" TYPE=B2VEP F-CONT(1360)=2.26+/-0.2e-9 Comments: SB2 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) B1950 0.0027 -0.011 0.005 6714( 5) - 06/28/96 14:50 - [ 5] Visit: 01 Visit Requirements: PERIOD 126.6731D AND ZERO-PHASE JD2435046.730000 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 HD10516 HRS ACQ 2.0 MIRROR-A2 BRIGHT=RETURN,SEARCH-SIZE=3 1 1.8 S ONBOARD ACQ FOR 2 Comments: IN ACQ EXPECT ABOUT 74000 CTS/S, STEP-TIME=0.2S ------------------------------------------------------------------------------------------------------------------------------------ 2 HD10516 HRS ACCUM 2.0 G160M 1647.0 FP-SPLIT=STD,COMB=FOUR, 3 435.2 S PHASE 0.13 TO 0.37 STEP-PATT=DEF,DOPPLER=DEF, STEP-TIME=0.2 Comments: EXPECTED COUNT RATE = 526, EXPECTED S/N = 830 ------------------------------------------------------------------------------------------------------------------------------------ 6714( 5) - 06/28/96 14:50 - [ 6] Visit: 02 Visit Requirements: PERIOD 126.6731D AND ZERO-PHASE JD2435046.730000 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 HD10516 HRS ACQ 2.0 MIRROR-A2 BRIGHT=RETURN,SEARCH-SIZE=3 1 1.8 S ONBOARD ACQ FOR 2 Comments: IN ACQ EXPECT ABOUT 74000 CTS/S, STEP-TIME=0.2S ------------------------------------------------------------------------------------------------------------------------------------ 2 HD10516 HRS ACCUM 2.0 G160M 1647.0 FP-SPLIT=STD,COMB=FOUR, 3 435.2 S PHASE 0.63 TO 0.87 STEP-PATT=DEF,DOPPLER=DEF, STEP-TIME=0.2 Comments: EXPECTED COUNT RATE = 526, EXPECTED S/N = 830 ------------------------------------------------------------------------------------------------------------------------------------ 6714( 5) - 06/28/96 14:50 - [ 7] Visit: 03 Visit Requirements: PERIOD 126.6731D AND ZERO-PHASE JD2435110.06655 On Hold Comments: Additional Comments: Added 1/2 period to zero-phase and 0.5 to phase requirement Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD10516 HRS ACQ 2.0 MIRROR-A2 BRIGHT=RETURN,SEARCH-SIZE=3 1 1.8 S ONBOARD ACQ FOR 2 Comments: IN ACQ EXPECT ABOUT 74000 CTS/S, STEP-TIME=0.2S ------------------------------------------------------------------------------------------------------------------------------------ 2 HD10516 HRS ACCUM 2.0 G160M 1374.0 FP-SPLIT=STD,COMB=FOUR, 3 435.2 S PHASE 0.38 TO 0.62 STEP-PATT=DEF,DOPPLER=DEF, STEP-TIME=0.2 Comments: EXPECTED COUNT RATE = 1190, EXPECTED S/N = 1250 PHASE 0.88 TO 1.00 ALSO ACCEPTABLE ------------------------------------------------------------------------------------------------------------------------------------ 3 HD10516 HRS ACCUM 2.0 G160M 1647.0 FP-SPLIT=STD,COMB=FOUR, 3 435.2 S STEP-PATT=DEF,DOPPLER=DEF, STEP-TIME=0.2 Comments: EXPECTED COUNT RATE = 526, EXPECTED S/N = 830 PHASE 0.88 TO 1.00 ALSO ACCEPTABLE ------------------------------------------------------------------------------------------------------------------------------------ 4 HD10516 HRS ACCUM 2.0 G160M 1735.0 FP-SPLIT=STD,COMB=FOUR, 2 435.2 S STEP-PATT=DEF,DOPPLER=DEF, STEP-TIME=0.2 Comments: EXPECTED COUNT RATE = 461, EXPECTED S/N = 630 PHASE 0.88 TO 1.00 ALSO ACCEPTABLE ------------------------------------------------------------------------------------------------------------------------------------ 6714( 5) - 06/28/96 14:50 - [ 8] Summary Form for Proposal 6714 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=RETURN SEARCH-SIZE=3 STEP-TIME=0.2 DOPPLER=DEF STEP-PATT=DEF COMB=FOUR FP-SPLIT=STD ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category BINARIES AND STAR FORMATION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PERIOD 126.6731D AND ZERO-PHASE JD2435046.730000 ONBOARD ACQ FOR 2 PHASE 0.13 TO 0.37 PHASE 0.63 TO 0.87 PERIOD 126.6731D AND ZERO-PHASE JD2435110.06655 PHASE 0.38 TO 0.62 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-A2 G160M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD10516 ------------------------------------------------------------------------------------------------------------------------------------