5865( 8) - 01/07/96 16:18 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5865 Version: 8 Check-in Date: 07-Jan-1996 16:15:10 1.Proposal Title: NLTE analysis of the hot post-AGB star ZNG1 in the galactic globular cluster M 5 and search for a nebula ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Hot Stars GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Ulrich Heber Astronomisches Institut der Universitaet Erlangen-Nuernberg CoI: Ralf Napiwotzki Astronomisches Institut der Universitaet N Erlangen-Nuernberg CoI: Stefan Haas Astronomisches Institut der Universitaet N Erlangen-Nuernberg CoI: Joachim Koeppen Institut fuer Theoretische Physik u. N Sternwarte der Universitaet Kiel ------------------------------------------------------------------------------------ 6. Abstract UV spectroscopy of the blue star ZNG1 in the galactic globular cluster M 5 shows striking similarities to the two known Central stars in globular clusters (K 648 in M15 and GJJC1 in M22). A forbidden ion NIV emission in the IUE spectrum has led Bohlin et al. (1983, ApJ 267, L89) to postulate a PN around ZNG1. If this could be confirmed, ZNG1 would be only the third known PNN in a globular cluster. Imaging with the ESO-NTT has demonstrated that ZNG1 is double with a cool companion separated by only 0sec point4. Optical spectroscopy of the hot star turned out to be impossible even with the NTT under good seeing conditions. The existing low resolution IUE spectra are of insufficient quality for a fine abundance analysis. We propose to search for a nebula around ZNG1 with PC narrowband photometry. A spectroscopic analysis of GHRS-UV-spectra with state-of-the-art NLTE models is proposed to search amongst halo PAGB stars for correlations with metallicity as predicted by stellar evolution theory. The metallicity of M 5 is considerably larger than of the previously studied stars in M 15 and M 22. ------------------------------------------------------------------------------------ 5865( 8) - 01/07/96 16:18 - [ 2] Observations Description ------------------------ The absolute magnitude of the star can be determined from archival PC images in the V filter by making use of the known cluster distance. An additional PC images will be exposed through the narrowband filters to search for HAlpha emission. The exposure times for these images are estimated not to saturate the possible central star. Exposure time 10 min. for HAlpha. The star is visible for 52min. per orbit. The PC observation can be done in one orbit. Two GHRS exposures using grating G140L are required to cover the strategic metal lines and ionHeII 1640Angstrom. We aim at a S/N=40 (reddest part) to 90 (blue end). UV fluxes are from the IUE low resolution spectrum described by Bohlin et al. (1983). The first setting of the grating will cover 1150 Angstrom to 1436 Angstrom, while the second setting shall cover 1464 Angstrom to 1750 Angstrom. Exposure times required are 11 minutes for the first and 23 min. for the second exposure. The GHRS observations can be carried out during the same visit in a second orbit (guide star reacquisition 6min. + exposure time 34 min. + instrument overhead 8min = 52 min.). The quide star acquisition can be done at the end of the first orbit. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5865( 8) - 01/07/96 16:18 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5904-ZNG1 STAR,SDO RA=15H 18M 34.073S +/- 0.01S, J2000 V = 14.2+/-0.2 DEC=+02D 04' 59.43" +/- 0.01" B-V = -0.2+/-0.2 E(B-V) = 0.03+/-0.01 Comments: HRS TARGET ZNG1 IN GLOBULAR CLUSTER M5 Coordinates have been derived from an archival PC-U-frame Accuracy of the coords. need to be checked. 5865( 8) - 01/07/96 16:18 - [ 4] 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5904- HRS ACQ 2.0 MIRROR-N1 SEARCH- 1 13.5S ONBOARD ACQ FOR 2-3 ZNG1 SIZE=3,BRIGHT=R ETURN Comments: STEP-TIME=1.5S, EXPECT 600 CNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC5904- HRS ACCUM 2.0 G140L 1150- FP- 1 870.4S ZNG1 1436 SPLIT=STD,COMB= FOUR,DOPPLER=ON Comments: Exposure time may be cut to allow exposures#4+5 in orbit2. Cut such that expo#3 remains about 2*expo#2. If to be cut below 10MIN notify PI. ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC5904- HRS ACCUM 2.0 G140L 1464- FP- 1 1632S ZNG1 1750 SPLIT=STD,COMB= FOUR,DOPPLER=ON Comments: Exposure time may be cut to allow exposures#4+5 in orbit2. Cut such that expo#3 remains about 2*expo#2. If to be cut below 20MIN notify PI. ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC5904- WFPC2 IMAGE PC1 F656N 6563 CR-SPLIT=NO 1 200S ZNG1 Comments: Exposure split into two. Do not cut further. ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC5904- WFPC2 IMAGE PC1 F656N 6563 CR-SPLIT=NO 1 300S ZNG1 Comments: Exposure split into two. Do not cut further. ------------------------------------------------------------------------------------------------------------------------------------ 5865( 8) - 01/07/96 16:18 - [ 5] Summary Form for Proposal 5865 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE=3 BRIGHT=RETURN DOPPLER=ON COMB=FOUR CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Hot Stars ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2-3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N1 G140L F656N ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC5904-ZNG1 ------------------------------------------------------------------------------------------------------------------------------------