Proposal_Information Title: A SEARCH FOR THE HELIUM COMPANION OF PHI PERSEI Proposal_Category: GO Scientific_Category: Hot Stars Cycle: 5 Investigators PI_name: Dr. Douglas Gies PI_Institution: Georgia State University CoI_Name: Dr. W. Bagnuolo CoI_Institution: Georgia State University Contact: N CoI_Name: Mr. D. Barry CoI_Institution: Georgia State University Contact: N 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. The best candidate for such a system is Phi Per, a binary with a period of 127 days. Poeckert (1981) found evidence of hot circumstellar gas surrounding the secondary and used the associated velocity curve to derive masses for both stars. We have recently used the Doppler tomography algorithm with IUE high dispersion spectra to reconstruct the individual spectra, and we find a weak secondary spectrum that resembles that of a hot subdwarf. We propose to obtain high S/N ratio spectra of Phi Per with the GHRS at two orbital phases with large relative Doppler shifts of the secondary's spectrum. These spectra will allow us to measure directly the secondary's weak spectral lines in the composite spectrum, which in turn will provide the UV intensity ratio, secondary projected rotational velocity, and a more secure secondary radial velocity curve. By combining results from both spectra, we can reconstruct a high S/N spectrum of the secondary star alone, which will help determine the temperature, gravity, and chemical abundance of the companion. This will provide fundamental data on the nature of the stripped-down companion, in the first detection of a binary that fills the evolutionary gap between systems of massive main sequence stars and the Be/X-ray binaries. Questions Observing_Description: Our goal is to obtain GHRS spectra of Phi Per near the two quadrature phases when the secondary's spectrum displays the largest relative Doppler shift (about 200 km/sec compared to typical secondary line widths of 95 km/sec). We plan to observe the spectral region between 1356 and 1392 Angstroms with the G160M grating (and Large Science Aperture) to record the many strong lines of Fe V, O V, and N IV that are present only in the secondary spectrum (the primary spectrum is relatively featureless in this region). The UV flux at 1360 Angstroms is 2.26e-9 ergs/cm^2/s/A (Code & Meade 1979, ApJS, 39, 195), and we should achieve a count rate of 1570 counts/s/diode with this grating arrangement. We expect a S/N = 1350 per diode for a 20 minute exposure. Even though the secondary contributes only about 12% of the total flux in the FUV, we would still achieve about S/N = 200 in the secondary spectrum reconstructed from both observations. This will be ample to make a spectrum synthesis study of the region (using Hubeny's TLUSTY and SYNSPEC programs) to determine the star's temperature, gravity, and metallic abundances. We need a minimum of two composite spectrum observations with differing orbital velocity shifts to successfully reconstruct the individual primary and secondary spectra. We need to make the observations near the quadrature phases of the orbit to maximize the velocity separation of the secondary features in the composite spectrum. Good separation will be achieved for one observation in each of the orbital phase ranges 0.15 - 0.35 and 0.65 - 0.85 (where phase 0 corresponds to primary superior conjunction). The orbital period and epoch are taken from Bozic et al. (1995, preprint). Real_Time_Justification: Calibration_Justification: Additional_Comments: Fixed_Targets Target_Number: 1 Target_Name: HD10516 Alternate_Names: PHI-PER, HR496, GSC0329102118 Description: STAR, B0-B2 V-IV, BE, INTERACTING BINARY Position: RA=1H 43M 39.63S +/- 0.004S, DEC=+50D 41' 19.5" +/- 0.04" ! Plate-id: 56 => Hipparcos coordinates from GSC Equinox: J2000 RV_or_Z: V = 1 RA_PM: 0.0027 Dec_PM: -0.011 Epoch: B1950 Annual_Parallax: 0.005 Flux: V = 4.07 +/- 0.02, B-V = -0.04 +/- 0.02, TYPE = B2VEP, F-CONT(1360) = 2.26 +/- 0.2 E-9 Comments: SB2 Visits Visit_Number: 1 Visit_Requirements: PERIOD 126.6731D AND ZERO-PHASE JD2435046.73 On_Hold_Comments: Visit_Comments: Exposure_Number: 1 Target_Name: HD10516 Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: MIRROR-A2 Wavelength: Optional_Parameters: BRIGHT=RETURN, SEARCH-SIZE=3 Number_of_Iterations: 1 Time_Per_Exposure: 1.8S Special_Requirements: ONBOARD ACQ FOR 2 Comments: IN ACQ EXPECT ABOUT 74000 CTS/S, STEP-TIME=0.2S Exposure_Number: 2 Target_Name: HD10516 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G160M Wavelength: 1374.0 Optional_Parameters: FP-SPLIT=STD, COMB=FOUR, STEP-PATT=DEF, DOPPLER=DEF, STEP-TIME=0.2 Number_of_Iterations: 3 Time_Per_Exposure: 435.2S Special_Requirements: PHASE 0.15 TO 0.35 Comments: EXPECTED COUNT RATE = 1570, EXPECTED S/N = 1350 Visit_Number: 2 Visit_Requirements: PERIOD 126.6731D AND ZERO-PHASE JD2435046.73 On_Hold_Comments: Visit_Comments: Exposure_Number: 1 Target_Name: HD10516 Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: MIRROR-A2 Wavelength: Optional_Parameters: BRIGHT=RETURN, SEARCH-SIZE=3 Number_of_Iterations: 1 Time_Per_Exposure: 1.8S Special_Requirements: ONBOARD ACQ FOR 2 Comments: IN ACQ EXPECT ABOUT 74000 CTS/S, STEP-TIME=0.2S Exposure_Number: 2 Target_Name: HD10516 Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G160M Wavelength: 1374.0 Optional_Parameters: FP-SPLIT=STD, COMB=FOUR, STEP-PATT=DEF, DOPPLER=DEF, STEP-TIME=0.2 Number_of_Iterations: 3 Time_Per_Exposure: 435.2S Special_Requirements: PHASE 0.65 TO 0.85 Comments: EXPECTED COUNT RATE = 1570, EXPECTED S/N = 1350 Data_Distribution Medium: 8MM Blocking_Factor: 10 Ship_To: PI_Address Ship_Via: UPS __Diagnostic-Sum-Section__ Software-Version (Controller= 2.1) Preprocessor (Errors= 0 Fatal-Errors= 0 ) Validation (Errors= 0 Fatal-Errors= 0 ) Transformation (Errors= 0 Fatal-Errors= 0 ) CASM (Errors= 0 Fatal-Errors= 0 ) __User-Comments__ Dear Denise: I am sending you my Phase II proposal for program 6046, "A search for the Helium Companion of Phi Per". The investigation was originally proposed as a FGS study, but we have changed our strategy to use the GHRS instead. I believe we are still answering the same scientific question posed in our Phase I proposal, but the spectroscopic approach appears to be much more promising. I will send you details for our change of strategy in a separate e-mail message. Cheers, Doug Gies (gies@chara.gsu.,edu)