6726( 19) - 07/15/97 16:41 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6726 Version: 19 Check-in Date: 15-Jul-1997 16:40:05 1.Proposal Title: PC Astrometry of the Brown Dwarf Candidate PPL 15 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle COOL STARS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: JACK MACCONNELL SPACE TELESCOPE SCIENCE INSTITUTE CoI: Edward Rosenthal Center for Astrophysics N CoI: Wm. van Altena Yale University Observatory N CoI: John Stauffer Center for Astrophysics N CoI: Geoffrey Marcy San Francisco State University N CoI: Gibor Basri University of California - Berkeley N ------------------------------------------------------------------------------------ 6. Abstract We plan to obtain deep, far red PC images of the field around the brown dwarf candidate, PPl 15, in the Pleiades. This low-mass object is the only brown dwarf candidate to date to show Li I in its spectrum thus at least requiring a mass of < 0.1 Msun. Its radial velocity matches that of more massive stars in the Pleiades, but nothing is known of its proper motion which accounts for two of three velocity vectors. Its membership is probable but will remain uncertain until the proper motion is determined. In addition to determining the proper motion, we expect to determine its parallax which will fix its luminosity and definitively answer the question of membership. The PC frames will also be useful to search for any anomalies in the image structure of PPl 15. ------------------------------------------------------------------------------------ 6726( 19) - 07/15/97 16:41 - [ 2] Observations Description ------------------------ We will use the F814W filter which is efficient and a good compromise for the energy distribution of PPl 15 and the unknown reference stars. An exposure of 300s will give a S/N of 55 on PPl 15 without saturating the central pixel. Because a good frame of reference stars is paramount to doing good astrometry, we wish to use the first orbit to take one or more test exposures to permit us to decide what combination of offset and orientation will provide the best reference frame. It is likely that the test exposures can be used in the final astrometric solution. We will then image at the best position with PPl 15 offset from the PC center as little as possible during four orbits separated by about six- month intervals when the parallax factor is near a maximum. The maxima are 21 Aug. and 20 Feb. With the 5-minute exposure times, we will be able to obtain four exposures per 53-minute visibility period after the GS acquisition and overheads, and we will sub- pixel dither between them to improve the spatial resolution and S/N. We will use spatial scans to dither rather than POS TARGs which are less efficient. The multiple images will also be useful for cosmic-ray rejection. Real Time Justification ----------------------- The visits are to be linked by six-month intervals and will be loosely time- critical to the level of a few weeks. Specific orients are expected. None. There are no coordinated observations necessary or planned. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS __Diagnosti Email: ------------------------------------------------------------------------------------ 6726( 19) - 07/15/97 16:41 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PPL-15 STAR,BROWN DWARF RA=3H 48M 4.5S +/- 0.1S, J2000.0 V=+5.6 V = 22.46 DEC=+23D 39' 33" +/- 1" V-I = 4.64 Comments: NO VALUE OF B-V AVAILABLE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1989.5 0.0015 -.045 0.008 2 REV-PPL-15 STAR,BROWN DWARF RA=57.01726D +/- 0.000001851D, J2000.0 V = 22.46 DEC=+23.66215D +/- 0.000278D V-I = 4.64 Comments: NO VALUE OF B-V AVAILABLE, new coordinates from PI on 7/23/96. 3 PPL-15-NEW STAR,BROWN DWARF RA=57.01948D +/- 0.000001851D, J2000.0 V=+5.6 V = 22.46 DEC=+23.66515D +/- 0.000278D V-I = 4.64 Comments: NO VALUE OF B-V AVAILABLE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1989.5 0.0015 -.045 0.008 6726( 19) - 07/15/97 16:41 - [ 4] Visit: 01 Visit Requirements: PCS MODE F BEFORE 12-JUN-1996 On Hold Comments: Additional Comments: This is a test visit to decide on final values of position and ORIENT of tgt. in PC1 so as to maximize number of ref. stars and choose ones not near edges. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PPL-15 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO,SCAN-READ=ALL 1 400 S SPATIAL SCAN 1 ------------------------------------------------------------------------------------------------------------------------------------ 6726( 19) - 07/15/97 16:41 - [ 5] Visit: 02 Visit Requirements: PCS MODE F ON HOLD FOR 1 BETWEEN 2-MAR-1997 AND 17-MAR-1997 ORIENT 70.58D TO 80.58D On Hold Comments: Waiting for analysis of 1st Visit Additional Comments: Desired pos. and ORIENT will be entered for Visit 2 after examining field taken in Visit 1. New coordinates entered and new orientation. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 2 REV-PPL-15 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO,DITHER-TYPE=LINE 2 400 S Comments: Because of requirements for accurate astrometry, Vis. 1/2 must be at same pos. and orient. and close to 1 yr. apart. Vis. 3/4 must be v. close to 6 months after them and oriented 180 deg. from them. ------------------------------------------------------------------------------------------------------------------------------------ 6726( 19) - 07/15/97 16:41 - [ 6] Visit: 03 Visit Requirements: PCS MODE F ORIENT 250.58D to 260.58D BETWEEN 10-AUG-1997 AND 10-SEP-1997 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 ------------------------------------------------------------------------------------------------------------------------------------ 3 PPL-15-NEW WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO,DITHER-TYPE=LINE 2 400 S Comments: The 'between' on V. 3 is for the max. pi factor but is during SM2 - ok if SM2 is delayed. If not, must sched. as late as possible before SM2. ------------------------------------------------------------------------------------------------------------------------------------ 6726( 19) - 07/15/97 16:41 - [ 7] Visit: 04 Visit Requirements: PCS MODE F ORIENT 250.58D TO 260.58D BETWEEN 10-AUG-1998 AND 10-SEP-1998 On Hold Comments: Additional Comments: Use same GS as Visit 3 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 4 PPL-15-NEW WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO,DITHER-TYPE=LINE 2 400 S ------------------------------------------------------------------------------------------------------------------------------------ 6726( 19) - 07/15/97 16:41 - [ 8] Scan Paramters Form ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 1 Exposure Logsheet lines: 1.001 FGS Scan: D Dwell Only: dwell points/line: 2 Seconds per dwell: 1.00 Scan width (arc-secs): 10.0000 Scan length (arc-secs): 10.0000 Angle between sides (degrees) 90.00 Number of lines: 2 Scan rate (arc-sec/sec): 0.0000 PA of first scan line (degrees) 90.000 Scan frame (CEL or S/C): CEL Length Offset (arc-sec): Width Offset (arc-sec): ------------------------------------------------------------------------------------------------------------------------------------ 6726( 19) - 07/15/97 16:41 - [ 9] Summary Form for Proposal 6726 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO SCAN-READ=ALL DITHER-TYPE=LINE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category COOL STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE F BEFORE 12-JUN-1996 SPATIAL SCAN 1 PCS MODE F ON HOLD FOR 1 BETWEEN 2-MAR-1997 AND 17-MAR-1997 ORIENT 70.58D TO 80.58D PCS MODE F ORIENT 250.58D to 260.58D BETWEEN 10-AUG-1997 AND 10-SEP-1997 PCS MODE F ORIENT 250.58D TO 260.58D BETWEEN 10-AUG-1998 AND 10-SEP-1998 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names PPL-15 REV-PPL-15 PPL-15-NEW ------------------------------------------------------------------------------------------------------------------------------------