6471( 11) - 12/12/96 16:37 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6471 Version: 11 Check-in Date: 12-Dec-1996 16:35:53 1.Proposal Title: A bolometric light curve for pulsating helium star LSS3184 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle HOT STARS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: SIMON JEFFERY UNIVERSITY OF ST. ANDREWS ------------------------------------------------------------------------------------ 6. Abstract LSS 3184 is an extreme helium star, that is, a `post-AGB' star with negligible hydrogen and significant overabundances of carbon, nitrogen and alpha-capture products in its atmosphere. In confirmation of a theoretical prediction, LSS 3184 was recently discovered to vary with a period of 2.5 hours, identical to that for the pulsating helium star V652 Her. Ground-based observations to verify the dicovery, define the visual (BVR) light curve and to establish the radial velocity curve were undertaken during May 1995. Ultraviolet observations are required to measure the bolometric light curve and the variation in Teff throughout the pulsation cycle. These will allow the stellar radius to be measured independent of distance. Only HST can provide the photometric precision necessary to make a direct test of stellar pulsation theory and an indirect test of modern opacities. These observations will also allow the first direct mass determination for a `bona fide' extreme helium star, vital for determining their evolutionary status. ------------------------------------------------------------------------------------ Observations Description ------------------------ NOTE ( 9 December, 1996 ): The PERIOD and PHASE requirements in the original program have been dropped at the request of the PI in order to give the program a second chance at being pulled from the pool and scheduled in the wake of its loss with the calendar which was interrupted by the November 1996 FOS safing. The text below this is the old, original text. - RAL In order to determine the bolometric light curve for LSS 3184 it is necessary to obtain time-resolved UV spectrophotometry throughout the pulsation cycle (0.1066 days =153 minutes). Observations will be made with the FOS in RAPID mode, using grating G160L, reading out the spectrum every 20s. These spectra will be coadded into 100s and 100Angstrom bins to provide S/N>~100/(100Angstrom)/(100s) between 1200 and 2500Angstrom. The 20s readout will allow us to identify short duration events (eg shocks at minimum radius) and to fine-tune the binnning procedure. Good pointing accuracy (~0.04") is needed to ensure precise photometry so, because the target is bright, a four-stage peak up requiring one orbit will be used to acquire the target. Observations will then be carried out during three subsequent orbits. Allowing for guide star reacquisition and earth occultation, on target time will cover 88% of the pulsation cycle, with two phase gaps of 6% each and 6% redundancy. Real Time Justification ----------------------- NOTE ( ( December, 1996 ): The PERIOD and PHASE requirements in the original program have been dropped at the request of the PI in order to give the program a second chance at being pulled from the pool and scheduled in the wake of its loss with the calendar which was interrupted by the November 1996 FOS safing. The text below this is the old, original text. - RAL Because the light curve coverage is not complete, it is necessary to schedule the observations carefully so that photometry is available for 0.05 cycles either side of predicted light maximum and minimum. This submission contains the best available optical ephemeris: Tmax = 2449477.46930 + 0.1066092 E +\\- 0.0018 0.0000005 Further ground-based observations in May 1996 will double the existing ephemeris base-line and will be made available immediately they become available. UV light maximum and minimum are estimated to occur at optical phases 0.1 and 0.7 respectively (by analogy with V652 Her). To ensure coverage of the crucial phases, the first science exposure must start within ONE of the phase windows 0.00-0.03, 0.20-0.43, 0.58-0.65 or 0.80-1.00. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: , ------------------------------------------------------------------------------------ 6471( 11) - 12/12/96 16:37 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 LSS3184 STAR,BP,PULSATING RA=14H 01M 36.62S +/- 0.03S,DEC= J2000 V = -89 V = 12.56+/-0.013 VARIABLE -66D 09' 55.8" +/- 0.5", PLATE- B = 12.64+/-0.019 ID=060Y E(B-V) = 0.27+/-0.2 F(1275)=3.10+/-0.23e-13 F(1675)=2.08+/-0.19e-13 F(2400)=1.17+/-0.23e-13 6471( 11) - 12/12/96 16:37 - [ 2] Visit: 01 Visit Requirements: 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 LSS3184 FOS/BL ACQ/PEA 4.3 G160L 1100-25 SCAN-STEP-Y=1.23,SEARCH-SIZE-Y=3, 1 1.5 S ONBOARD ACQ FOR 20 K 00 SEARCH-SIZE-X=1 Comments: FOS Handbook Table 2-1 Pattern A Wavelength range used to avoid wrap-around problem in zeroth order spike during ACQ/PEAK as per Keyes. ------------------------------------------------------------------------------------------------------------------------------------ 20 LSS3184 FOS/BL ACQ/PEA 1.0-PAI G160L 1100-25 SCAN-STEP-Y=0.61,SCAN-STEP-X=0.61 1 1.5 S ONBOARD ACQ FOR 30 K R-A 00 ,SEARCH-SIZE-Y=2,SEARCH-SIZE-X=6 Comments: FOS Handbook Table 2-1 Pattern B2 Uses STEP-PATT=SINGLE by default. Wavelength range used to avoid wrap-around problem in zeroth order spike during ACQ/PEAK as per Keyes. ------------------------------------------------------------------------------------------------------------------------------------ 30 LSS3184 FOS/BL ACQ/PEA 0.5-PAI G160L 1100-25 SCAN-STEP-Y=0.29,SCAN-STEP-X=0.29 1 1.5 S ONBOARD ACQ FOR 40 K R-A 00 ,SEARCH-SIZE-Y=3,SEARCH-SIZE-X=3 Comments: FOS Handbook Table 2-1 Pattern C2 Uses STEP-PATT=SINGLE by default. Wavelength range used to avoid wrap-around problem in zeroth order spike during ACQ/PEAK as per Keyes. ------------------------------------------------------------------------------------------------------------------------------------ 40 LSS3184 FOS/BL ACQ/PEA 0.25-PA G160L 1100-25 SCAN-STEP-Y=0.11,SCAN-STEP-X=0.11 1 13 S ONBOARD ACQ FOR 50 K IR-A 00 ,SEARCH-SIZE-Y=4,SEARCH-SIZE-X=4 Comments: FOS Handbook Table 2-1 Pattern P4 Uses STEP-PATT=SINGLE by default. Wavelength range used to avoid wrap-around problem in zeroth order spike during ACQ/PEAK as per Keyes. Exposure time dropped slightly in 4th stage as per Keyes in order to make all 4 stages fit in first orbit in current system. ------------------------------------------------------------------------------------------------------------------------------------ 50 LSS3184 FOS/BL RAPID 1.0-PAI G160L STEP-PATT=SINGLE,READ-TIME=20 1 8540 S R-A ------------------------------------------------------------------------------------------------------------------------------------ 6471( 11) - 12/12/96 16:37 - [ 3] Summary Form for Proposal 6471 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK RAPID ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCAN-STEP-Y=1.23 SEARCH-SIZE-Y=3 SEARCH-SIZE-X=1 SEARCH-SIZE-X=6 SEARCH-SIZE-X=3 SEARCH-SIZE-X=4 READ-TIME=20 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 20 ONBOARD ACQ FOR 30 ONBOARD ACQ FOR 40 ONBOARD ACQ FOR 50 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G160L ------------------------------------------------------------------------------------------------------------------------------------ Target Names LSS3184 ------------------------------------------------------------------------------------------------------------------------------------