Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5497 Report Date: 18-Jul-95:17:32 Version: ********** Check-in Date: ********** 1.Proposal Title: SPECTROSCOPIC IDENTIFICATION OF CANDIDATE CATACLYSMIC VARIABLE STARS NEAR THE CENTER OF THE POST-CORE-COLLAPSE GLOBULAR CLUSTER NGC 6397: CYCLE4 HIGH ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID HOT STARS GO 1 Long Term yrs Sub Category X-RAY BINARIES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Jonathan E Grindlay 2170 USA 617-495-7204 ------------------------------------------------------------------------------------ 7. Abstract We propose to obtain FOS spectra of three candidate cataclysmic variables (CVs) near the center of the nearby post-core-collapse globular cluster NGC 6397. These objects are located in the error circles of faint x-ray sources discovered with the ROSAT High Resolution Imager (HRI), and thus represent possible optical counterparts. We discovered these CV candidates in an imaging study of NGC 6397 in H-alpha and "R" filters performed with the HST Planetary Camera (PC). Photometry we have performed of the roughly 2200 stars in the PC field indicates that these three stars have absolute magnitudes and H-alpha emission line strengths typical of CVs. These stars also have the UV-excesses expected of CVs, as determined from a comparison of the PC data to several archival HST-FOC images of the cluster in UV filters. These objects are excellent candidates to be the long-sought CVs in globular clusters; spectroscopy is required to test this hypothesis. Due to the extreme crowding at the center of NGC 6397, spectroscopy of these faint candidates requires the angular resolution provided by HST. This study, which represents the final stage of our efforts to identify compact binaries in globular clusters, will provide a critical test of theories for the formation and evolution in clusters of interacting binaries and their progeny -- CVs, low-mass X-ray binaries, and millisecond pulsars. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 5.12 par: 0 10. Num targs pri: 3 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5497 PI: Jonathan E Grindlay Proposal Title: SPECTROSCOPIC IDENTIFICATION OF CANDIDATE CATACLYSMIC VARIABLE STARS NEAR THE CENTER OF THE POST-CORE-COLLAPSE GLOBULAR CLUSTER NGC 6397: CYCLE4 HIGH ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Jonathan E Grindlay 2170 USA Adrienne M. Cool 2170 USA Paul J. Callanan 2170 USA Charles D. Bailyn 3900 USA Haldan N. Cohn 2270 USA Phyllis M. Lugger 2270 USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. We propose to use the FOS with the red detector and G570H grating, covering the wavelength range 4571-6820 A. The target sequence is designed to provide reliable pointing at three science targets, which given their faintness and the extreme crowding in this globular cluster, cannot be acquired directly. The first target is a bright star which is sufficiently isolated that we can use the ACQ/BINARY target acquisition method. The remaining 6 targets consist of three pairs. The first star in each pair is a bright neighbor of a science target; the second star is the science target itself. We peak up (ACQ/PEAK) on the bright neighbor of each science target, then offset a small distance to the science target. The ACQ/PEAKs will be done using the 0.3" (0.26") aperture and .16-.18" steps to provide pointing to <= 0.13". We assume that the small offsets (1.3"-- 2.7") to the science targets will result in negligible additional uncertainty in the pointing. We use the 0.5" (0.43") aperture on all science targets, so that pointing uncertainties up to 0.2" can be tolerated. Given the anticipated 3 sigma uncertainty of 0.45" in the pointing following ACQ/BINARY, we use a 6x6 scan on the first "neighbor" star. For the other two "neighbor" stars we use 5x5 scans and 0.16" steps, as the uncertainty following the offsets to these stars should be less than 0.2". After each science target exposure, we take an "ACQ image" to provide a check on the pointing position. Coordinates have been measured by us and by the GASP group at STScI relative to the GSC. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The extreme crowding in this globular cluster field requires the HST (see Question 3). ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. The 11 "exposures" that make up this observation MUST BE DONE IN THE ORDER SPECIFIED (linenum 1 through linenum 11). This sequence (SEQ) is designed to obtain reliable and accurate pointing in this very crowded field at the center of a globular cluster (see Question 3). We give absolute positions of only the first target (measured for us at STScI relative to the GSC on PC frames we had previously obtained). It is the only target of the 7 that is sufficiently isolated to permit a reliable intial pointing. Once we have acquired this target we OFFSET to our other targets. See question 3 above for a detailed explanation of the observing strategy. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. Page 3 ------------------------------------------------------------------------------------ 9. Description of previous HST work. We have successfully proposed for two photometry proposals and one archival research proposal for work related to this investigation: Cycle 1: Program P2555, ``Cataclysmic Variables and Millisecond Pulsars in Globular Cluster Cusps" (J. Grindlay, PI). Cycle 2: Program GO-3851, ``Deep Search for CVs and Compact Binaries in the Collapsed Close Globular NGC6397" (J. Grindlay, PI). Cycle 2, archival research: Program AR-3793, ``Comparison of HST Data on Globular Clusters with Other Data Sets" (C. Bailyn, PI). The P2555 program was for a preliminary H- alpha vs. R image of the core of NGC6752. A total of about 2 hours exposure was obtained with PC, yielding a senistivity limit of about Mv = 5. The data were incorrectly processed (at STScI) originally in that the wrong bias frames were used. The re-processed bias frames and flats were received only in January 1992, and we are currently still in the process of carrying out a DAOPHOT analsysis of the images. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). CfA is fully equipped to reduce HST data (with IRAF). Co-I's also have access to similar HST data reduction facilities. ------------------------------------------------------------------------------------ 11. Address Information Name: JONATHAN E GRINDLAY Category: PI Institution: 2170 Address: HARVARD COLLEGE OBSERVATORY CENTER FOR ASTROPHYSICS MAIL STOP 6 City: CAMBRIDGE State: MA Zip Code: 02138 Country: USA Telephone: 617-495-7204 Telex (or e-mail): 921428; INTERNET: JOSH@CFA255.HARVARD.EDU ------------------------------------------------------------------------------------ Name: Category: CON Institution: Address: City: State: Zip Code: Country: Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5497 [ 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 NGC6397- A,138,C,201 PLATE-ID=0688, J2000 1 V = 14, B-V=0.85, TYPE=G5III STAR1-OFFSET RA = 17H 40M 40.57S +/- 2 E(B-V) = 0.2 0.100S, DEC = -53D 40' 01.1" +/- 1.00" ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6397- A,138,C,201 PLATE-ID=0688, J2000 1 V = 14, B-V=0.85, TYPE=G5III STAR2-OFFSET RA-OFF = 0.91S +/- 0.005S, 2 E(B-V) = 0.2 DEC-OFF = -20.0" +/- 0.05", FROM 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6397- A,161,C,201 PLATE-ID=0688, J2000 1 V = 18 STAR3 RA-OFF = 0.93S +/- 0.005S, 2 E(B-V) = 0.2 DEC-OFF = -18.8" +/- 0.05", FROM 1 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC6397- A,138,C,201 PLATE-ID=0688, J2000 1 V = 15.8, B-V=0.7, TYPE=F8IV STAR4-OFFSET RA-OFF = 1.81S +/- 0.005S, 2 E(B-V) = 0.2 DEC-OFF = -21.0" +/- 0.05", FROM 1 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC6397- A,161,C,201 PLATE-ID=0688, J2000 1 V = 20 STAR5 RA-OFF = 1.99S +/- 0.005S, 2 E(B-V) = 0.2 DEC-OFF = -18.7" +/- 0.05", FROM 1 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC6397- A,138,C,201 PLATE-ID=0688, J2000 1 V = 14.4, B-V=0.18, TYPE=A0V STAR6-OFFSET RA-OFF = 1.67S +/- 0.005S, 2 E(B-V) = 0.18 DEC-OFF = -30.9" +/- 0.05", FROM 1 ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC6397- A,161,C,201 PLATE-ID=0688, J2000 1 V = 18.8 STAR7 RA-OFF = 1.64S +/- 0.005S, 2 E(B-V) = 0.2 DEC-OFF = -28.1" +/- 0.05", FROM 1 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5497 [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6397- FOS/RD ACQ/ 4.3 MIRROR 1 2.1S 1 1 CYCLE 4 STAR1- BINARY ONBOARD ACQ FOR 2 OFFSET SEQ 1-11 NO GAP ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6397- FOS/RD ACQ/ 0.3 MIRROR TYPE=UP 1 2.0S 1 1 CYCLE 4 STAR2- PEAK SEARCH-SIZE-X=5 ONBOARD ACQ FOR 3 OFFSET SEARCH-SIZE-Y=5 SCAN-STEP- X=0.18 SCAN-STEP- Y=0.18 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6397- FOS/RD ACCUM 0.5 G570H 4571- 1 60S 1 1 CYCLE 4 STAR2- 6815 OFFSET ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC6397- FOS/RD ACCUM 0.5 G570H 4571- 1 25M 1 1 CYCLE 4 STAR3 6815 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC6397- FOS/RD ACQ 4.3 MIRROR 1 32S 1 1 CYCLE 4 STAR3 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC6397- FOS/RD ACQ/ 0.3 MIRROR TYPE=UP 1 7S 1 1 CYCLE 4 STAR4- PEAK SEARCH-SIZE-X=5 ONBOARD ACQ FOR 7 OFFSET SEARCH-SIZE-Y=5 SCAN-STEP- X=0.16 SCAN-STEP- Y=0.16 ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC6397- FOS/RD ACCUM 0.5 G570H 4571- 1 75M 1 1 CYCLE 4 STAR5 6815 ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC6397- FOS/RD ACQ 4.3 MIRROR 1 6M 1 1 CYCLE 4 STAR5 ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC6397- FOS/RD ACQ/ 0.3 MIRROR TYPE=UP 1 2S 1 1 CYCLE 4 STAR6- PEAK SEARCH-SIZE-X=5 ONBOARD ACQ FOR 10 OFFSET SEARCH-SIZE-Y=5 SCAN-STEP- X=0.16 SCAN-STEP- Y=0.16 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC6397- FOS/RD ACCUM 0.5 G570H 4571- 1 28M 1 1 CYCLE 4 STAR7 6815 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC6397- FOS/RD ACQ 4.3 MIRROR 1 60S 1 1 CYCLE 4 STAR7 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5497 [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY ACQ/PEAK ACCUM ACQ ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters TYPE=UP SEARCH-SIZE-X=5 SEARCH-SIZE-Y=5 SCAN-STEP-X=0.18 SCAN-STEP-Y=0.18 SCAN-STEP-X=0.16 SCAN-STEP-Y=0.16 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 5.12 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category X-RAY BINARIES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4; ONBOARD ACQ FOR 2; SEQ 1-11 NO GAP ONBOARD ACQ FOR 3; ONBOARD ACQ FOR 7; ONBOARD ACQ FOR 10; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G570H ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC6397-STAR1-OFFSET NGC6397-STAR2-OFFSET NGC6397-STAR3 NGC6397-STAR4-OFFSET NGC6397-STAR5 NGC6397-STAR6-OFFSET NGC6397-STAR7 ------------------------------------------------------------------------------------------------------------------------------------