9278( 2) - 07/16/01 08:19 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9278 Version: 2 Check-in Date: 16-Jul-2001 08:19:24 1.Proposal Title: The Next Geminga: A Neutron Star Identification for the Egret Source 3EG J1835+5918 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Prof. Jules Halpern Columbia University ------------------------------------------------------------------------------------ 5. Abstract 3EG J1835+5918 is the brightest of the so-called unidentified EGRET sources at intermediate Galactic latitude (l, b)=(89, 25). We obtained complete radio, optical, and X-ray coverage of its error box, discovering a faint ultrasoft X-ray source that can only be a nearby neutron star. 3EG J1835+5918 may thus become the prototype of an hypothesized population of older pulsars, born in the Gould belt, that can account for as many as 40 local EGRET sources. We propose to prove that it is a neutron star and assess its point of origin by obtaining precise coordinates with Chandra and deep HST images to measure its color and proper motion. X-ray spectral information will address its temperature, age, distance, and thus its gamma-ray efficiency. ------------------------------------------------------------------------------------ 9278( 2) - 07/16/01 08:19 - [ 2] Observations Description ------------------------ Our goal is to reach the faintest limits possible for detection of a point source, and to obtain gross information about the spectral shape of the continuum. This is best accomplished with the STIS CCD clear filter and long- pass filter. Since the target is in the continuous viewing zone (CVZ), we assume that the full 96 minute orbit will be available. We request a total of four CVZ orbits in one visit, with two allocated to the clear filter and two to the long-pass filter. After accounting for guide-star acquisition and other overheads, approximately 10, 000 s of exposure will be available for each filter. These will be subdivided into approximately 12 exposures for each filter in a dither pattern to aid in rejection of cosmic rays and hot pixels. The estimated limiting magnitude achieved with the open filter is thus V=28.0 at a signal-to-noise ratio of 10. The long-pass filter will provide the basic information about whether the source is red or blue. The idea is to subtract the long-pass filter from the open filter to obtain two non-overlapping photometric points. There will be many objects in this field that can be used for astrometric transfer to our ground based CCD images, which themselves were obtained under excellent seeing of 0.8 arcseconds. The brightest object in the field will be a late K star of V=20.7 which is 11 arcseconds west of the target area, and which presents no special problems. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9278( 2) - 07/16/01 08:19 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 RXJ1836.2+59 UNIDENTIFIED, X-RAY RA=18H 36M 13.72S +/- 3.", J2000 V = 27.0+/-1.5 25 EMITTER, STAR, NEUTRON DEC=59D 25' 30.05" +/- 3.", B-V = 0.5+/-1.0 STAR PLATE-ID=00T3 Coordinate Source: IMAGE_TIED_TO_GSC_FRAME 9278( 2) - 07/16/01 08:19 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type STIS-CCD-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.567 Coordinate_Frame POS-TARG Pattern_Orient 26.6 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 9278( 2) - 07/16/01 08:19 - [ 5] Visit: 01 Visit Priority: Visit Requirements: CVZ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 RXJ1836.2+5 STIS/C ACCUM F28X50L MIRROR GAIN=1,CR-SPLIT=4 1 2600 S PATTERN 1 10 NO SPLIT 925 CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 RXJ1836.2+5 STIS/C ACCUM 50CCD MIRROR GAIN=1,CR-SPLIT=4 1 2600 S PATTERN 1 20 NO SPLIT 925 CD ------------------------------------------------------------------------------------------------------------------------------------ 9278( 2) - 07/16/01 08:19 - [ 6] Summary Form for Proposal 9278 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 50CCD ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters GAIN=1 CR-SPLIT=4 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ PATTERN 1 10 NO SPLIT PATTERN 1 20 NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names RXJ1836.2+5925 ------------------------------------------------------------------------------------------------------------------------------------