Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4571c Report Date: 09-May-96:19:43 Version: ********** Check-in Date: ********** 1.Proposal Title: SPECTROSCOPIC IDENTIFICATION OF CANDIDATE OPTICAL COUNTERPARTS OF ROSAT X-RAY SOURCES IN THE NEARBY COLLAPSED GLOBULAR CLUSTER NGC6397 CYC3MEDIUM ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID HOT STARS GO Sub Category X-RAY BINARIES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Prof Jonathan E Grindlay HARVARD UNIVERSITY USA 617 4967204 PROF ------------------------------------------------------------------------------------ 7. Abstract We propose to obtain FOS spectra of a candidate counterpart to a faint X-ray source that we have detected in the nearby, collapsed- core globular cluster NGC 6397 using the ROSAT High Resolution Imager (HRI). This object is likely to be either a cataclysmic variables (CVs), that was produced by tidal capture events in the dense core of the cluster, or an RS CVn binary that has been hardened by interactions with other stars. Due to the extreme crowding at the center of NGC 6397, spectroscopic study of faint candidate requires the angular resolution provided by HST. This study will provide a critical test of theories for the formation and evolution in clusters of interacting binaries and their progeny -- CVs, RS CVns, low-mass X-ray binaries (LMXBs), and millisecond pulsars. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 3.40 par: 0 10. Num targs pri: 3 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 4571c PI: Prof Jonathan E Grindlay Proposal Title: SPECTROSCOPIC IDENTIFICATION OF CANDIDATE OPTICAL COUNTERPARTS OF ROSAT X-RAY SOURCES IN THE NEARBY COLLAPSED GLOBULAR CLUSTER NGC6397 CYC3MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Jonathan E. Grindlay 2170 USA Paul J. Callanan 2170 USA Adrienne M. Cool 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), enabling us to cover H-alpha, H-beta and HeII 4686. The sequence of three targets is designed to provide accurate and reliable pointing in the extreme crowding in this globular cluster. The first star is used for pointing exclusively; the second is used to improve the pointing accuracy and to obtain a spectrum of the background light in the vicinity of the third target. The third target is the primary science target, and requires that the pointing be accurate to 0.1" or better. The first target star was chosen because it is isolated enough to allow the use of the ACQ/BINARY target acquisition method reliably. The GASP group at STScI has measured our PC frames containing this star (in PC7) as well as the second and third targets (in PC6) relative to the Guide Star Catalog system. Following ACQ/BINARY (pointing accuracy less or equal to 0.2") on this star, we OFFSET to a second star close to target 3, and do a fine pointing on it using the ACQ/PEAK mode, and the 0.3" circular aperture in order to obtain pointing accurate to less or equal to 0.1", which is critical for the observation of target 3. The 5x5 SPATIAL SCAN we perform with the 0.3" aperture relies on there being an additional error of less than 0.2" due to offsetting and inaccuracies in relative positions of the targets. Following ACQ/PEAK on the second target, we OFFSET FROM IT to the final target (1.3" away). ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The extreme crowding in this globuar cluster field requires the HST (see Question 3). ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. The 5 "exposures" that make up this observation MUST BE DONE IN THE ORDER SPECIFIED (linenum 1 through linenum 5). The ONLY POSSIBLE EXCEPTION to this is that linenum 4 and 5 could be interchanged. 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 three that is sufficiently isolated to permit a reliable intial pointing. Once we have acquired this target we OFFSET to the second target, which we use to improve the accuracy of the pointing (using AQC/PEAK). We then OFFSET from this position to the final (and principal science) target just 1.3" away. Page 3 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. The spectra will be searched for evidence for any emission features which would indicate an interacting binary system. The data will be reduced using the standard IRAF reduction routines: all proposers have experience reducing HST data using IRAF on SUN and VMS systems. ------------------------------------------------------------------------------------ 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 60 GARDEN STREET City: CAMBRIDGE State: MA Zip Code: 02138 Country: USA Telephone: 617-495-7204 Telex (or e-mail): 921428 ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 4571c [ 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 40.639S +/- 2 E(B-V) = 0.2 0.100S, DEC = -53D 40' 01.707" +/- 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 = 0.8622S +/- 0.005S, 2 E(B-V) = 0.2 DEC-OFF = -20.246" +/- 0.05", FROM 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6397- A,161,C,201 PLATE-ID=0688, J2000 1 V = 18 STAR3 RA-OFF = 0.8852S +/- 0.005S, 2 E(B-V) = 0.2 DEC-OFF = -18.960" +/- 0.05", FROM 1 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4571c [ 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 3S 1 1 CYCLE 3 STAR1- BINARY ONBOARD ACQ FOR 2 OFFSET SEQ 1-5 NO GAP ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6397- FOS/RD ACQ/ 0.3 MIRROR TYPE=UP 1 4.5S 1 1 CYCLE 3 STAR2- PEAK SEARCH-SIZE=5 ONBOARD ACQ FOR 3 OFFSET SCAN-STEP=0.2 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6397- FOS/RD ACCUM 0.5 G570H 4571- 1 7M 1 1 CYCLE 3 STAR2- 6815 OFFSET ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC6397- FOS/RD ACCUM 0.5 G570H 4571- 1 50M 1 1 CYCLE 3 STAR3 6815 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC6397- FOS/RD ACQ 4.3 MIRROR 1 2.2M 1 1 CYCLE 3 STAR3 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4571c [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY ACQ/PEAK ACCUM ACQ ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters TYPE=UP SEARCH-SIZE=5 SCAN-STEP=0.2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 3.40 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category X-RAY BINARIES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 3; ONBOARD ACQ FOR 2; SEQ 1-5 NO GAP ONBOARD ACQ FOR 3; CYCLE 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G570H ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC6397-STAR1-OFFSET NGC6397-STAR2-OFFSET NGC6397-STAR3 ------------------------------------------------------------------------------------------------------------------------------------