6649( 12) - 10/28/96 15:07 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6649 Version: 12 Check-in Date: 28-Oct-1996 15:03:01 1.Proposal Title: Calibrating Boron Abundances with RR Lyrae ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle COOL STARS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Ruth C. Peterson ASTROPHYSICAL ADVANCES CoI: Bruce Carney University of North Carolina N CoI: Horace Smith Michigan State University N ------------------------------------------------------------------------------------ 6. Abstract We propose to obtain high-resolution GHRS ECH-B spectra of the boron region near 2495Angstrom\ of RR Lyrae, the prototype pulsating variable star, to establish the characteristics of possible blends affecting B I lines. GHRS spectra of B I lines have been obtained for a wide variety of stars, from Procyon (F4 IV) to giants such as the Hyades (K0 III) and to extremely metal-poor stars. The resulting boron abundances shed light on mixing and dilution processes during stellar evolution and the early history of light-element abundances in the oldest stars. These results are compromised if unidentified lines contaminate the B I features of interest. For example, the ECH -B observations of Procyon yield only an upper limit in two separate investigations because of this possibility. We will establish the nature of any such blends by observing RR Lyrae, a moderately-metal-poor star which undergoes a temperature change of about 1000K during the course of each cycle (0.57 day). Being a core-helium-burning star whose current photosphere was once buried deep in the convective zone, RR Lyrae is expected to have a very low boron abundance and is sharp-lined at almost all phases, so blends will stand out. By mapping the strength of any absorption near the B I line positions with phase and therefore temperature, we will be able to discern whether blends are present and how they strengthen and weaken at other temperatures and abundances. This knowledge will lead to more accurate boron abundances for stars with existing HRS spectra. ------------------------------------------------------------------------------------ Observations Description ------------------------ Our plan is to monitor the boron spectral region around the cycle of RR Lyrae with the 90,000 resolution of HRS ECH-B. We must time the start carefully to cover phases 0.07-0.57, to hit both the high-temperature (7000K) and low- temperature (6000K) phases while lines are quite sharp, with rotational velocity less than 10 km/s. Because the photospheric velocity is changing with phase, though, we are restricted to 15 minute exposures. We have selected RR Lyrae itself for this study because it is about four times brighter than any other RR Lyrae star. Its period is 0.5668 day, and varies somewhat because of the Blazhko effect, the modulation of the temperature and velocity range during a pulsation cycle seen in many RR Lyrae stars, which occurs in RR Lyrae with a 40.8 day period. The correct phasing is critical. Carney and Smith will monitor RR Lyrae photometrically to improve the ephemeris of the fundamental mode pulsation. The photometry and the spectroscopic radial velocities from the HST spectra will provide accurate phase information and temperature estimates for each of the HST observations. The wavelength stability of sequential HST observations is important in this regard. Exposure levels may be estimated by comparing RR Lyrae at maximum to a relatively cool field horizontal branch star of approximately the same temperature. Such a star is HD 86986, with V = 8.0, B -V = 0.12, and U-B = 0.16 (Kodaira, Greenstein, & Oke 1969). According to IUE observations discussed by Cacciari (1985), HD 86986 has a flux of 1.2 * 10^-12 erg/s/cm^2/Angstrom\\ at 2495Angstrom. RR Lyrae at maximum has V = 7.2, B-V = 0.16, and U-B = 0.13. Approximating the 2495Angstrom\\ difference by the U difference of 0.8 magnitudes indicates a flux for RR Lyrae at maximum of 2.5 * 10^-12 erg/s/cm^2/Angstrom\\ at 2495Angstrom. According to the inverse sensitivity of 13.4 * 10^11 per erg/s/cm^2/Angstrom\\ for ECH-B, GHRS Handbook v.\\ 6.0 Table 8 -4, further reduced by a factor of four for the blaze function at 2497Angstrom, we would expect 0.9 ct/s/diode for RR Lyrae at maximum. We will obtain 10-15 minute integrations to prevent velocity smearing. A single 15 minute exposure should produce 800 cts/diode, for a S/N = 30 per diode (3 km/s). At minimum, RR Lyrae is fainter, but the change in temperature takes place more slowly, so multiple exposures may be summed (with appropriate velocity shifts). Four such exposures should give S/N = 30 per diode at minimum as well. Real Time Justification ----------------------- Beginning in the spring of 1996, Carney and Smith will begin monitoring RR Lyrae photometrically to improve the ephemeris of the fundamental mode pulsation, using the 0.6-meter telescopes and CCD systems at the University of North Carolina and Michigan State University. The photometry will be absolute or differential, depending upon conditions. When the HST observations are actually scheduled, photometric monitoring will be intensified to compensate for the 40.8-day Blazhko effect and achieve good estimates for the temperatures of the star for each of the HST observations. After the first data are taken, we will examine the spectra and make phase corrections if necessary for the subsequent observations. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6649( 12) - 10/28/96 15:07 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD182989 STAR, RR LYRAE STAR RA=19H 25M 28.09S +/- 0.1S, DEC= J2000 V = 7.4+/-0.5 +42D 47' 07.5" +/- 0.2", PLATE- B-V = .2+/-0.1 ID=01KC E(B-V) = 0.02+/-2 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1982. -0.010 -0.184 0.0 6649( 12) - 10/28/96 15:07 - [ 2] Visit: 01 Visit Requirements: PERIOD 0.566839D AND ZERO-PHASE JD2446654.368 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 HD182989 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN,SEARCH-SIZE=3 1 1.8 S ONBOARD ACQ FOR 2 SEQ 1-4 NON-INT Comments: STEP-TIME =0.2S ------------------------------------------------------------------------------------------------------------------------------------ 2 HD182989 HRS ACQ/PEA 0.25 MIRROR-N2 SEARCH-SIZE=5 1 5.0 S ONBOARD ACQ FOR 3-14 KUP Comments: STEP-TIME = 0.2S ------------------------------------------------------------------------------------------------------------------------------------ 3 WAVE HRS ACCUM SC2 ECH-B 2495 SPYBAL=YES 1 54.4 S ------------------------------------------------------------------------------------------------------------------------------------ 4 HD182989 HRS ACCUM 0.25 ECH-B 2495 FP-SPLIT=NO,STEP-PATT=DEF 3 380.8 S ------------------------------------------------------------------------------------------------------------------------------------ 5 WAVE HRS ACCUM SC2 ECH-B 2495 SPYBAL=YES 1 54.4 S SEQ 5-6 NON-INT PHASE 0.04 TO 0.08 ------------------------------------------------------------------------------------------------------------------------------------ 6 HD182989 HRS ACCUM 0.25 ECH-B 2495 FP-SPLIT=NO,STEP-PATT=DEF 4 598.4 S ------------------------------------------------------------------------------------------------------------------------------------ 7 WAVE HRS ACCUM SC2 ECH-B 3130 SPYBAL=YES 1 54.4 S SEQ 7-8 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 8 HD182989 HRS ACCUM 0.25 ECH-B 3130 FP-SPLIT=NO,STEP-PATT=DEF 4 598.4 S ------------------------------------------------------------------------------------------------------------------------------------ 9 WAVE HRS ACCUM SC2 ECH-B 3130 SPYBAL=YES 1 54.4 S SEQ 9-10 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 10 HD182989 HRS ACCUM 0.25 ECH-B 3130 FP-SPLIT=NO,STEP-PATT=DEF 3 816. S ------------------------------------------------------------------------------------------------------------------------------------ 11 WAVE HRS ACCUM SC2 ECH-B 2495 SPYBAL=YES 1 54.4 S SEQ 11-12 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 12 HD182989 HRS ACCUM 0.25 ECH-B 2495 FP-SPLIT=NO,STEP-PATT=DEF 3 816. S ------------------------------------------------------------------------------------------------------------------------------------ 13 WAVE HRS ACCUM SC2 ECH-B 2495 SPYBAL=YES 1 54.4 S SEQ 13-14 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 14 HD182989 HRS ACCUM 0.25 ECH-B 2495 FP-SPLIT=NO,STEP-PATT=DEF 3 816. S ------------------------------------------------------------------------------------------------------------------------------------ 6649( 12) - 10/28/96 15:07 - [ 3] Visit: 02 Visit Requirements: PERIOD 0.566839D AND ZERO-PHASE JD2446654.368 ON HOLD FOR 1 On Hold Comments: Verify exposures 4 and 6 of visit 1 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 ------------------------------------------------------------------------------------------------------------------------------------ 21 HD182989 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN,SEARCH-SIZE=3 1 1.8 S ONBOARD ACQ FOR 22 SEQ 21-24 NON-INT Comments: STEP-TIME =0.2S ------------------------------------------------------------------------------------------------------------------------------------ 22 HD182989 HRS ACQ/PEA 0.25 MIRROR-N2 SEARCH-SIZE=5 1 5.0 S ONBOARD ACQ FOR 23-26 KUP Comments: STEP-TIME = 0.2S ------------------------------------------------------------------------------------------------------------------------------------ 23 WAVE HRS ACCUM SC2 ECH-B 2495 SPYBAL=YES 1 54.4 S ------------------------------------------------------------------------------------------------------------------------------------ 24 HD182989 HRS ACCUM 0.25 ECH-B 2495 FP-SPLIT=NO,STEP-PATT=DEF 3 380.8 S ------------------------------------------------------------------------------------------------------------------------------------ 25 WAVE HRS ACCUM SC2 ECH-B 2495 SPYBAL=YES 1 54.4 S SEQ 25-26 NON-INT PHASE 0.04 TO 0.08 ------------------------------------------------------------------------------------------------------------------------------------ 26 HD182989 HRS ACCUM 0.25 ECH-B 2495 FP-SPLIT=NO,STEP-PATT=DEF 4 598.4 S ------------------------------------------------------------------------------------------------------------------------------------ 6649( 12) - 10/28/96 15:07 - [ 4] Summary Form for Proposal 6649 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAKUP ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=RETURN SEARCH-SIZE=3 SEARCH-SIZE=5 SPYBAL=YES STEP-PATT=DEF FP-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category COOL STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PERIOD 0.566839D AND ZERO-PHASE JD2446654.368 ONBOARD ACQ FOR 2 SEQ 1-4 NON-INT ONBOARD ACQ FOR 3-14 SEQ 5-6 NON-INT PHASE 0.04 TO 0.08 SEQ 7-8 NON-INT SEQ 9-10 NON-INT SEQ 11-12 NON-INT SEQ 13-14 NON-INT PERIOD 0.566839D AND ZERO-PHASE JD2446654.368 ON HOLD FOR 1 ONBOARD ACQ FOR 22 SEQ 21-24 NON-INT ONBOARD ACQ FOR 23-26 SEQ 25-26 NON-INT PHASE 0.04 TO 0.08 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 ECH-B ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD182989 WAVE ------------------------------------------------------------------------------------------------------------------------------------