Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 1093c Report Date: 09-May-96:16:08 Version: ********** Check-in Date: ********** 1.Proposal Title: OBSERVATIONS OF ZZ CETI STARS ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID STELLAR ASTROPHYSICS GTO/HSP 1093 Sub Category ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Robert C. Bless WISCONSIN, UNIVERSITY OF USA (608) 262-1715 ------------------------------------------------------------------------------------ 7. Abstract The ZZ Ceti Stars are pulsating DA white dwarfs with temperatures near 11,000K. They are all pulsating in the non-radial g-modes, and are multi-periodic with periods between 200 sec and 1200 sec. Two major uncertainties about the ZZ Ceti stars are first, the exact temperature limits of the ZZ Ceti instability strip, and second, whether the luminosity variations are entirely due to temperature variations - as they should be if the pulsations are g-mode pulsations. We propose to observe the ZZ Ceti stars with the high speed photometer to measure their mean colors (and thus mean temperatures) and their color variations (and thus their temperature variations). Revision History: Received on RPS 9/1/89; Added to SCCS 9/5/89 Updated to V2 prop instr; RPSS V7.2 remote & local; Added data-fmt - SALM 9/7/89; Text changes - SALM 9/28/89; Reduce Texp to 6H - SALM 2/14/90 MJN 3/20/92 - removed prism mode and moved observation to UV2. Split observation to two 3 hour runs in the F184W and F284M filters. ------------------------------------------------------------------------------------ 8. Scientific Key Words: PULSATING WHITE DWARFS ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 7.04 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 1093c PI: Robert C. Bless Proposal Title: OBSERVATIONS OF ZZ CETI STARS ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Edward L. Robinson TEXAS, UNIVERSITY OF USA Robert C. Bless WISCONSIN, UNIVERSITY OF USA G. W. Van Citters NATIONAL SCIENCE FOUNDATION USA Joseph F. Dolan NASA, GODDARD SPACE FLIGHT USA CENTER Richard L. White SPACE TELESCOPE SCIENCE USA INSTITUTE James L. Elliot MASSACHUSETTS INSTITUTE OF USA TECHNOLOGY ------------------------------------------------------------------------------------ 3. Description of proposed observations. We propose to measure the ultraviolet colors (lambda-lambda-1850, 2700 A) of the ZZ Ceti star, G117-B15A over its pulsation cycle (P = 215.2 s) with high accuracy. Simultaneous two-color ultraviolet photometry is planned using the HSP. In order to measure the photometric variations with high precision, we need to observe G117-B15A (B = 15.5 +/- 0.2 mag) for 10 hours, sampling at one second intervals. The high speed photometer is the optimum instrument for this project and G117-G15A is the prime ZZ Ceti candidate owing to the extreme stability of its pulsation period and the relative simplicity of its light curve. Cycle 1 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The temperatures and temperature variations of the ZZ Ceti stars can only be reliably measured at the ultraviolet wavelengths accessible to ST. Absolute temperature determinations for lambda > 4500 A have large uncertainties (+/- 500 K) due both to contamination of the optical region (lambda-lambda 4000 - 6000 A) by Balmer lines and continuum and the temperature insensitivity of working on the Rayleigh-Jeans tail of the energy distribution. It is estimated that a five-fold improvement in the temperature determinations would result from ST observations. ------------------------------------------------------------------------------------ 13. Ultraviolet high speed photometry is proposed for G116-B15 A, a remarkably stable ZZ Ceti star (P = 215.2 sec) in order to precisely determine mean ultraviolet colors (mean temperatures) and color variations (temperature variations). ------------------------------------------------------------------------------------ 11. Address Information Name: EDWARD L. ROBINSON Category: CON Institution: UNIVERSITY OF TEXAS Address: DEPARTMENT OF ASTRONOMY City: AUSTIN State: TX Zip Code: 78712 Country: USA Telephone: (512)471-4461 Telex (or e-mail): ------------------------------------------------------------------------------------ Page 3 Name: ROBERT C. BLESS Category: PI Institution: UNIVERSITY OF WISCONSIN Address: WASHBURN OBSERVATORY 475 N. CHARTER STREET City: MADISON State: WI Zip Code: 53706 Country: USA Telephone: (608)262-1715 Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 1093c [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 G117-B15A ZZ CETI STAR RA = 9H 24M 15.35S +/- 0.4", J2000 COMP 1 V=15.5+/-.2 DEC = +35D 16' 51.0" +/- 0.4" Comments: G117-B15A HAS A CPM COMPANION AT 13.4" DISTANCE WITH A POSITION ANGLE OF 123 DEGREES. POSREF = ROBINSON. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 1093c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 0.5 G117-B15A HSP/ ACQ DATA- 1 60S 1 1 ONBOARD ACQ FOR 1 UV2 FORMAT=WORD CYCLE 2 / 0.5-4 PCS MODE FINE / 0.5-4 ------------------------------------------------------------------------------------------------------------------------------------ 1 G117-B15A HSP/ SINGLE 1.0 F145M SAMPLE- 1 1.5H 1 1 UV2 TIME=0.05 Comments: FOR LINE 1, GAPS DUE TO EARTH OCCULTATION SHOULD BE MINIMIZED. ------------------------------------------------------------------------------------------------------------------------------------ 1.5 G117-B15A HSP/ ACQ DATA- 1 60S 1 1 ONBOARD ACQ FOR 2 UV2 FORMAT=WORD ------------------------------------------------------------------------------------------------------------------------------------ 2 G117-B15A HSP/ SINGLE 1.0 F145M SAMPLE- 1 1.5H 1 1 UV2 TIME=0.05 Comments: FOR LINE 1, GAPS DUE TO EARTH OCCULTATION SHOULD BE MINIMIZED. ------------------------------------------------------------------------------------------------------------------------------------ 2.5 G117-B15A HSP/ ACQ DATA- 1 60S 1 1 ONBOARD ACQ FOR 3 UV2 FORMAT=WORD ------------------------------------------------------------------------------------------------------------------------------------ 3 G117-B15A HSP/ SINGLE 1.0 F184W SAMPLE- 1 1.5H 1 1 UV2 TIME=0.05 Comments: FOR LINE 1, GAPS DUE TO EARTH OCCULTATION SHOULD BE MINIMIZED. ------------------------------------------------------------------------------------------------------------------------------------ 3.5 G117-B15A HSP/ ACQ DATA- 1 60S 1 1 ONBOARD ACQ FOR 4 UV2 FORMAT=WORD ------------------------------------------------------------------------------------------------------------------------------------ 4 G117-B15A HSP/ SINGLE 1.0 F184W SAMPLE- 1 1.5H 1 1 UV2 TIME=0.05 Comments: FOR LINE 1, GAPS DUE TO EARTH OCCULTATION SHOULD BE MINIMIZED. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 1093c [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HSP/UV2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ SINGLE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters DATA-FORMAT=WORD SAMPLE-TIME=0.05 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GTO/HSP ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 7.04 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR ASTROPHYSICS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 1; CYCLE 2 / 0.5-4; PCS MODE FINE / 0.5-4; ONBOARD ACQ FOR 2; ONBOARD ACQ FOR 3; ONBOARD ACQ FOR 4; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F145M F184W ------------------------------------------------------------------------------------------------------------------------------------ Target Names G117-B15A ------------------------------------------------------------------------------------------------------------------------------------