6116( 9) - 07/31/95 14:43 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6116 Version: 9 Check-in Date: ********** 1.Proposal Title: A search for the optical counterpart of the triple pulsar system PSR B1620-26 in M4 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Hot Stars GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Charles Bailyn Yale University CoI: Terrence M. Girard Yale University N CoI: Frederic A. Rasio Institute for Advanced Study N CoI: Brian Yanny Fermi National Accelerator Laboratory N ------------------------------------------------------------------------------------ 6. Abstract The accurate optical identification of the millisecond pulsar B1620-26 in the globular cluster M4 (NGC6121) is crucial for determining the nature of this unique hierarchical triple system. Ground based imaging has revealed a potential condidate, which may well be blended and/or a chance superposition. We propose a short WF/PC II observation which will unambiguously demonstrate whether an optical counterpart exists, and if so, determine its magnitude and color. The results will be of great interest both for issues relating to the origin of pulsars, and in terms of dynamical processes in globular clusters. ------------------------------------------------------------------------------------ 6116( 9) - 07/31/95 14:43 - [ 2] Observations Description ------------------------ We wish to detect or rule out the presense of a V=23th magnitude object without overly saturating nearby stars (1sec point 5 to 5'', corresponding to 30 to 100 pixels from the target), which have magnitude 16. A 16th magnitude star saturates in the F555W filter (hereafter ``V'') in about 10 seconds (based on the exposure time calculations given in the WFPC-2 Instrument Handbook and on previous WFPC-2 images of the globular cluster M30, Yanny et al 1994b). To reach V=23 with S/N=10, requires a total exposure of about 120 secs. Additionally, to determine the color of the object, which if a star, will be quite red, we request I (F814W) exposures of the same field. The sensitivity of the WFPC-2 in the I filter is about half that of the V band and so we require similar exposure times for objects with colors expected to have V-I~ 1. Several short exposures in F555W and F814W will be used to model the PSF and subtract the wings of the target's bright neighboring stars. Then a series of longer exposure in both filters will be used to obtain the full required S/N for faint objects. Thus we request three 10 sec and three 40 second exposures in each filter, for a total exposure time of 5 minutes. With acquisition time of 12 minutes, and overhead of 3* 12=36 minutes, all the exposures can be completed in one 53 minute orbit. Real Time Justification ----------------------- In order to avoid bleeding and diffraction spikes from a very bright saturated V=13.0 mag star onto the target 5 arcseconds distant, we request that the roll angle of the spacecraft be such that the orientation of the y-axis of the WFPC- 2/PC CCD with respect to the east-west axis be less than 25 degrees. New photographic plates are scheduled to be taken with the double astrograph of the Yale Southern Observatory at El Leoncito Argentina next spring. This plate material will serve to tie the optical images to a standard system without the need for proper motion corrections. We also hope to obtain improved ground based CCD images (deeper and better seeing) when the WIYN telescope comes on line next spring. With these new data, we expect to be able to tie the PC data requested here to the FK5 astrometric system with an accuracy better than 0sec point1. Thus the dominant systematic error in locating the pulsar position on the PC image will be the accuracy of the transformation between the solar system ephemeris used to determine the pulsar timing positions, and the FK5 system. This error is estimated to be ~ 0sec point1 (Standish, 1990). Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6116( 9) - 07/31/95 14:43 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6116( 9) - 07/31/95 14:43 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PSR-B1620-26 STAR, pulsar RA=16H 23M 38.22S +/- 0.1S, DEC= 2000 V=21 +/- 2 -26D 31' 53.7" +/- 0.2", PLATE- ID=02J6 6116( 9) - 07/31/95 14:43 - [ 5] Visit: 01 Visit Requirements: ORIENT 18D TO 72D On Hold Comments: <none> Additional Comments: The orientation requirement is to avoid bleeding from a 13th magnitude star located 5" due north of the target. Also, we are informed by our scientific contact (Howard Lanning) that the diagnostic relating to overfull tape recorders can be waived for orbits containing up to 14 WFPC2 images, since a second tape recorder was installed during the refurbishment mission. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PSR-B1620- WFPC2 IMAGE PC1 F555W 1 40S 26 ------------------------------------------------------------------------------------------------------------------------------------ 2 PSR-B1620- WFPC2 IMAGE PC1 F814W 1 40S 26 ------------------------------------------------------------------------------------------------------------------------------------ 3 PSR-B1620- WFPC2 IMAGE PC1 F555W 1 3S 26 ------------------------------------------------------------------------------------------------------------------------------------ 4 PSR-B1620- WFPC2 IMAGE PC1 F555W 1 3S 26 ------------------------------------------------------------------------------------------------------------------------------------ 5 PSR-B1620- WFPC2 IMAGE PC1 F555W 1 3S 26 ------------------------------------------------------------------------------------------------------------------------------------ 6 PSR-B1620- WFPC2 IMAGE PC1 F555W 1 40S 26 ------------------------------------------------------------------------------------------------------------------------------------ 7 PSR-B1620- WFPC2 IMAGE PC1 F555W 1 120S 26 ------------------------------------------------------------------------------------------------------------------------------------ 11 PSR-B1620- WFPC2 IMAGE PC1 F814W 1 120S 26 ------------------------------------------------------------------------------------------------------------------------------------ 12 PSR-B1620- WFPC2 IMAGE PC1 F814W 1 40S 26 ------------------------------------------------------------------------------------------------------------------------------------ 13 PSR-B1620- WFPC2 IMAGE PC1 F814W 1 3S 26 ------------------------------------------------------------------------------------------------------------------------------------ 14 PSR-B1620- WFPC2 IMAGE PC1 F814W 1 3S 26 ------------------------------------------------------------------------------------------------------------------------------------ 15 PSR-B1620- WFPC2 IMAGE PC1 F814W 1 3S 26 ------------------------------------------------------------------------------------------------------------------------------------ 16 PSR-B1620- WFPC2 IMAGE PC1 F814W 1 40S 26 ------------------------------------------------------------------------------------------------------------------------------------ 17 PSR-B1620- WFPC2 IMAGE PC1 F555W 1 40S 26 ------------------------------------------------------------------------------------------------------------------------------------ 6116( 9) - 07/31/95 14:43 - [ 6] Summary Form for Proposal 6116 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Hot Stars ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 18D TO 72D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names PSR-B1620-26 ------------------------------------------------------------------------------------------------------------------------------------