6821( 5) - 04/18/97 13:03 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6821 Version: 5 Check-in Date: 18-Apr-1997 12:55:40 1.Proposal Title: Optical Counterparts for Low-Luminosity X -ray Sources in Globular Clusters ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle BINARIES AND STAR FOR GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: ADRIENNE COOL SAN FRANCISCO STATE UNIVERSITY CoI: Paul Hertz Naval Research Laboratory N CoI: Charles Bailyn Yale University N CoI: Jonathan Grindlay Harvard University N CoI: Paul Callanan Center for Astrophysics N CoI: Haldan Cohn Indiana University N CoI: Phyllis Lugger Indiana University N ------------------------------------------------------------------------------------ 6. Abstract This project uses narrow band H-alpha imaging with the WFPC2 to search for optical counterparts for low-luminosity X-ray sources in the globular cluster Omega Cen. Remarkably little is known about this class of cluster X-ray sources, yet it apparently constitutes the largest known population of compact binary stars in globulars. Optical identifications are the critical first step in learning more about these systems. H-alpha imaging has a proven track record in identifying promising counterparts for low-luminosity X-ray sources in two globular clusters, NGC 6397 and NGC 6752. Optical identifications of the X-ray sources in Omega Cen will increase our database of compact, interacting binaries in clusters, allowing us to address fundamental questions about the formation of binaries and their role in cluster dynamical evolution. ------------------------------------------------------------------------------------ 6821( 5) - 04/18/97 13:03 - [ 2] Observations Description ------------------------ The program consists of images in the R (F675W), H-alpha (F656N), and U (F336W) filters of the core of the globular cluster Omega Cen. The goal is to identify optical counterparts for faint X-ray sources which are expected to be unusually bright in H-alpha vs. R and/or U vs. R. In each orbit we will take two long H- alpha exposures, together with a small number of shorter R, U, and/or H-alpha exposures. All images must be taken at the identical orientation. Several different orientations will allow the error circles of all three sources to be encompassed. However, the allowable orientations are not all contiguous. Since RPS2 allows for only one range of continguous orientations to be specified, and since different target coordinates would be required for each orientation, we have picked the orientation that provides for the maximum contiguous range of possible angles. We have done this in order to minimize the complexity of our Phase II plan. However, if it necessary or advantageous for the scheduling of this program, additional orientations and their corresponding target coordinates can be provided by the PI. For the range of orientations we have specified (67.5D to 82D), one of the three X-ray sources will be placed in the PC1 chip, and the other two in the WF2 and WF4 chips, respectively. In order to achieve a maximum range of orientations, and still encompass the error circles for the three sources, it is necessary to place the source that will fall in PC1 not at the center of the chip, but in one corner. In the system of (x,y) coordinates for the PC1 chip shown in Fig. 9-1 (p.9-14) of the Phase II Proposal Instructions, the required corner is 10 arcsec from the top (outer) edge and 12 arcsec from the left edge (side adjacent to WF2). In order to place the target at this position, we use the PC1-FIX designation, which corresponds to pixel position (420,424), and specify POS TARG -7.5, +7.5. This should cause the target of WFPC2 to shift to the left by 7.5 arcsec and upward by 7.5 arcsec, placing it in the desired corner of the PC1. The individual exposures are as follows. In F656N, a total of 10 exposures with durations of 700-1100s (or longer if visibility times permit) will be obtained, two at each of five positions. In F675W, we will also obtain 2 exposures at four of the five dither position, each of duration 100s. Two exposures at each position will allow for cosmic ray removal. The use of five different target positions will remove ambiguities associated with CCD defects (e.g. hot pixels). We adopt a non- integral offset between four of the five positions ("dithering") in order to effectively enhance the spatial resolution. We designate these four positions using identical target coordinates but different POS TARG values, shifting by 0.25 arcsec between consecutive dither positions. Many stars will be saturated in the 10 "long" F656N exposures. To correct for saturation, we will take, at two of the dither positions, one medium-length (160 sec) and one short exposure (20 sec). Saturation will also be a serious problem in F675W, thus the longest exposures we use are 100s. A total of 8 100s exposures will be obtained for a total exposure time of 800s. When stacked, the F675W images will contain a more than a factor of 4 more counts than the F656N stacked images for typical stars. The strategy adopted with the F336W filter is slightly different, in order to save time. Two "long" exposures (>=260s) will be taken, and offset from each other by an integral number of pixels (in orbit 3). The integral pixels shift will enable both cosmic rays and chip defects to be identified. One short exposure (26s) will suffice to correct for saturation in the 260s exposures. Real Time_Justification: None. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- The orientation contraint we have specified for this program limits the possible dates it can be scheduled to about 32 days during two periods in May- July of 1996, or to a similar number of days in 1997. These dates represent the longest contiguous periods in which the spacecraft orientation will allow the scientific aims of the project to be fully achieved. We respectfully request that the program be scheduled during the period of May-July 1996 if at all possible. The specific dates that are feasible in 1996 are May 8-13 and June 18 through July 15. ------------------------------------------------------------------------------------ 6821( 5) - 04/18/97 13:03 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: Department of Physics and Astronomy*San Francisco State University*San Francisco, CA*94132 Ship Via: UPS Email: ------------------------------------------------------------------------------------ 6821( 5) - 04/18/97 13:03 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5139 STELLAR CLUSTER, RA=13H 26M 53.52S +/- 0.01S,DEC= J2000 V = +232 SURF(V) = 16.8 GLOBULAR CLUSTER -47D 29' 01.40" +/- 0.10", PLATE V = 11 -ID=ZZZR B-V = 0.8 V-R = 0.5 U-B = 0.2 E(B-V) = 0.15 Comments: All images will contain many thousands of stars, the brightest of which will have V magnitudes of 11 to 12. 6821( 5) - 04/18/97 13:03 - [ 5] Visit: 01 Visit Requirements: ORIENT 67.5D TO 82D On Hold Comments: Additional Comments: All exposures in this visit must be done at the identical orientation. Images taken in the same filters are best done as close in time to one- another as possible. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 101 NGC5139 WFPC2 IMAGE PC1-FIX F675W CR-SPLIT=NO 1 100 S POS TARG -7.5000, +7.5000 MIN DUR 100S MAX DUR 100S ------------------------------------------------------------------------------------------------------------------------------------ 102 NGC5139 WFPC2 IMAGE PC1-FIX F675W CR-SPLIT=NO 1 100 S POS TARG -7.5000, +7.5000 MIN DUR 100S MAX DUR 100S ------------------------------------------------------------------------------------------------------------------------------------ 103 NGC5139 WFPC2 IMAGE PC1-FIX F656N CR-SPLIT=NO 1 20 S POS TARG -7.5000, +7.5000 MIN DUR 20S MAX DUR 20S ------------------------------------------------------------------------------------------------------------------------------------ 104 NGC5139 WFPC2 IMAGE PC1-FIX F656N CR-SPLIT=NO 1 160 S POS TARG -7.5000, +7.5000 MIN DUR 160S MAX DUR 160S ------------------------------------------------------------------------------------------------------------------------------------ 105 NGC5139 WFPC2 IMAGE PC1-FIX F656N CR-SPLIT=0.5,CR-TOLERANCE=0.15 1 1800 S POS TARG -7.5000, +7.5000 MIN DUR 1700S ------------------------------------------------------------------------------------------------------------------------------------ 201 NGC5139 WFPC2 IMAGE PC1-FIX F675W CR-SPLIT=NO 1 100 S POS TARG -7.2500, +7.5000 MIN DUR 100S MAX DUR 100S ------------------------------------------------------------------------------------------------------------------------------------ 202 NGC5139 WFPC2 IMAGE PC1-FIX F675W CR-SPLIT=NO 1 1 S POS TARG -7.2500, +7.5000 MIN DUR 1S MAX DUR 1S ------------------------------------------------------------------------------------------------------------------------------------ 203 NGC5139 WFPC2 IMAGE PC1-FIX F675W CR-SPLIT=NO 1 10 S POS TARG -7.2500, +7.5000 MIN DUR 10S MAX DUR 10S ------------------------------------------------------------------------------------------------------------------------------------ 204 NGC5139 WFPC2 IMAGE PC1-FIX F675W CR-SPLIT=NO 1 100 S POS TARG -7.2500, +7.5000 MIN DUR 100S MAX DUR 100S ------------------------------------------------------------------------------------------------------------------------------------ 205 NGC5139 WFPC2 IMAGE PC1-FIX F656N CR-SPLIT=0.5,CR-TOLERANCE=0.15 1 2200 S POS TARG -7.2500, +7.5000 MIN DUR 2100S ------------------------------------------------------------------------------------------------------------------------------------ 301 NGC5139 WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 260 S POS TARG -7.2500, +7.5000 MIN DUR 260S MAX DUR 260S ------------------------------------------------------------------------------------------------------------------------------------ 302 NGC5139 WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 26 S POS TARG -7.2500, +7.5000 MIN DUR 26S MAX DUR 26S ------------------------------------------------------------------------------------------------------------------------------------ 303 NGC5139 WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 1 260 S POS TARG -7.7500, +7.0000 MIN DUR 260S MAX DUR 260S ------------------------------------------------------------------------------------------------------------------------------------ 304 NGC5139 WFPC2 IMAGE PC1-FIX F656N CR-SPLIT=0.5,CR-TOLERANCE=0.15 1 1600 S POS TARG -7.7500, +7.0000 MIN DUR 1500S ------------------------------------------------------------------------------------------------------------------------------------ 401 NGC5139 WFPC2 IMAGE PC1-FIX F675W CR-SPLIT=NO 1 100 S POS TARG -7.5000, +7.2500 MIN DUR 100S MAX DUR 100S ------------------------------------------------------------------------------------------------------------------------------------ 6821( 5) - 04/18/97 13:03 - [ 6] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 402 NGC5139 WFPC2 IMAGE PC1-FIX F675W CR-SPLIT=NO 1 100 S POS TARG -7.5000, +7.2500 MIN DUR 100S MAX DUR 100S ------------------------------------------------------------------------------------------------------------------------------------ 403 NGC5139 WFPC2 IMAGE PC1-FIX F656N CR-SPLIT=NO 1 20 S POS TARG -7.5000, +7.2500 MIN DUR 20S MAX DUR 20S ------------------------------------------------------------------------------------------------------------------------------------ 404 NGC5139 WFPC2 IMAGE PC1-FIX F656N CR-SPLIT=NO 1 160 S POS TARG -7.5000, +7.2500 MIN DUR 160S MAX DUR 160S ------------------------------------------------------------------------------------------------------------------------------------ 405 NGC5139 WFPC2 IMAGE PC1-FIX F656N CR-SPLIT=0.5,CR-TOLERANCE=0.15 1 2000 S POS TARG -7.5000, +7.2500 ------------------------------------------------------------------------------------------------------------------------------------ 501 NGC5139 WFPC2 IMAGE PC1-FIX F675W CR-SPLIT=NO 1 100 S POS TARG -7.2500, +7.2500 MIN DUR 100S MAX DUR 100S ------------------------------------------------------------------------------------------------------------------------------------ 502 NGC5139 WFPC2 IMAGE PC1-FIX F675W CR-SPLIT=NO 1 1 S POS TARG -7.2500, +7.2500 MIN DUR 1S MAX DUR 1S ------------------------------------------------------------------------------------------------------------------------------------ 503 NGC5139 WFPC2 IMAGE PC1-FIX F675W CR-SPLIT=NO 1 10 S POS TARG -7.2500, +7.2500 MIN DUR 10S MAX DUR 10S ------------------------------------------------------------------------------------------------------------------------------------ 504 NGC5139 WFPC2 IMAGE PC1-FIX F675W CR-SPLIT=NO 1 100 S POS TARG -7.2500, +7.2500 MIN DUR 100S MAX DUR 100S ------------------------------------------------------------------------------------------------------------------------------------ 505 NGC5139 WFPC2 IMAGE PC1-FIX F656N CR-SPLIT=0.5,CR-TOLERANCE=0.15 1 2200 S POS TARG -7.2500, +7.2500 MIN DUR 2100S ------------------------------------------------------------------------------------------------------------------------------------ 6821( 5) - 04/18/97 13:03 - [ 7] Summary Form for Proposal 6821 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO CR-TOLERANCE=0.15 CR-SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category BINARIES AND STAR FORMATION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 67.5D TO 82D POS TARG -7.5000, +7.5000 MIN DUR 100S MAX DUR 100S POS TARG -7.5000, +7.5000 MIN DUR 20S MAX DUR 20S POS TARG -7.5000, +7.5000 MIN DUR 160S MAX DUR 160S POS TARG -7.5000, +7.5000 MIN DUR 1700S POS TARG -7.2500, +7.5000 MIN DUR 100S MAX DUR 100S POS TARG -7.2500, +7.5000 MIN DUR 1S MAX DUR 1S POS TARG -7.2500, +7.5000 MIN DUR 10S MAX DUR 10S POS TARG -7.2500, +7.5000 MIN DUR 2100S POS TARG -7.2500, +7.5000 MIN DUR 260S MAX DUR 260S POS TARG -7.2500, +7.5000 MIN DUR 26S MAX DUR 26S POS TARG -7.7500, +7.0000 MIN DUR 260S MAX DUR 260S POS TARG -7.7500, +7.0000 MIN DUR 1500S POS TARG -7.5000, +7.2500 MIN DUR 100S MAX DUR 100S POS TARG -7.5000, +7.2500 MIN DUR 20S MAX DUR 20S POS TARG -7.5000, +7.2500 MIN DUR 160S MAX DUR 160S POS TARG -7.5000, +7.2500 POS TARG -7.2500, +7.2500 MIN DUR 100S MAX DUR 100S POS TARG -7.2500, +7.2500 MIN DUR 1S MAX DUR 1S POS TARG -7.2500, +7.2500 MIN DUR 10S MAX DUR 10S POS TARG -7.2500, +7.2500 MIN DUR 2100S ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F675W F656N F336W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC5139 ------------------------------------------------------------------------------------------------------------------------------------