6845( 12) - 05/21/97 11:11 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6845 Version: 12 Check-in Date: 21-May-1997 11:10:08 1.Proposal Title: 51 Pegasi X? ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle COOL STARS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: DAVE SODERBLOM SPACE TELESCOPE SCIENCE INSTITUTE CoI: Keith Noll Space Telescope Science Institute N CoI: Michel Mayor Observatoire de Geneve N CoI: Didier Queloz Observatoire de Geneve N ------------------------------------------------------------------------------------ 6. Abstract Mayor & Queloz have recently discovered a companion to the G dwarf 51 Pegasi, a companion that is likely to have a mass comparable to Jupiter's. There is also evidence for at least one more companion, a 51 Peg X, because the residuals in the radial velocities after the orbit of 51 Peg B are subtracted are large. This program will obtain WFPC2 images of 51 Pegasi at two different orientations with the goal of detecting additional low-mass companions. WFPC2 observations would be capable of detecting faint stellar companions very close to the primary star, a region inaccessible from the ground and to radial velocity searches. ------------------------------------------------------------------------------------ 6845( 12) - 05/21/97 11:11 - [ 2] Observations Description ------------------------ The most important issue for observing 51 Peg is removal of the effects of the PSF because we are looking for a faint companion in the immediate vicinity of the star (more distant objects can be found from the ground). We have therefore selected a well-characterized filter for our observations, F814W, and we will place 51 Peg near the center of the PC chip. To give an idea of what we might hope to detect, note that Jupiter at the distance of 51 Peg (13.5 pc) would have an apparent magnitude of about V = 32. That is clearly beyond the realm of the possible, even before we consider it lying next to a bright star. Any companion to 51 Peg is not isolated and is swamped by the stellar signal. We estimate that 51 Peg itself will be overexposed at even the shortest WFPC2 exposure time (0.11 sec), producing about 50 saturated pixels. At a 60-second exposure time, about 30,000 pixels will be saturated, meaning that we will wish to use CLOCKS=YES. This is equivalent to about 38 saturated columns. Therefore our strategy is to use two orbits of exposures, with a roll angle of 67.5 degrees between them. Rolling 90 degrees takes a companion object out of the saturated columns, and the additional +/-22.5 degrees is needed to get out from behind the diffraction spikes. Each orbit will consist of exposures of 0.11, 1.0, 10, 100, and 300 seconds in F814W\\@. The 100 and 300 second exposures will be repeated to eliminate cosmic rays. This stepped series of expoures allows us to sample well out into the wings of the PSF. Also F814W is a well- characterized filter for this type of observation. 51 Peg A is 5.5 in V or about 4.5 in I. By subtracting the PSF of the central star we expect to be able to reach 10 magnitudes fainter at 1 arcsec and 12 mag at 3 arcsec. These correspond to 14.5 and 16.5 in I, or approximately 14 and 16 in M_I. This corresponds to a spectral type of about M5 on the main sequence. Thus this program should be able to detect very-low-mass stars. Clearly we cannot detect a Jupiter, as such, but other classes of low-mass companions are detectable. Real Time Justification ----------------------- Some scheduling limitations to achieve desired roll angles. None Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address*3700 San Martin Drive*Baltimore*21218 Ship Via: UPS Email: ------------------------------------------------------------------------------------ 6845( 12) - 05/21/97 11:11 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 51PEG STAR,G V-IV RA=22H 57M 27.965S +/- 0.01S, 2000 V = 5.5 DEC=+20D 46' 7.10" +/- 0.1" B-V = 0.67 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 0.0135 0.043 0.074 6845( 12) - 05/21/97 11:11 - [ 4] Visit: 01 Visit Requirements: 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 51PEG WFPC2 IMAGE PC1-FIX F814W 1 0.11 S SEQ 10-19 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 11 51PEG WFPC2 IMAGE PC1-FIX F555W 1 0.11 S ------------------------------------------------------------------------------------------------------------------------------------ 12 51PEG WFPC2 IMAGE PC1-FIX F555W 1 1.0 S ------------------------------------------------------------------------------------------------------------------------------------ 13 51PEG WFPC2 IMAGE PC1-FIX F814W 1 1.0 S ------------------------------------------------------------------------------------------------------------------------------------ 14 51PEG WFPC2 IMAGE PC1-FIX F814W CLOCKS=YES 1 10 S ------------------------------------------------------------------------------------------------------------------------------------ 15 51PEG WFPC2 IMAGE PC1-FIX F439W CLOCKS=YES 1 10 S ------------------------------------------------------------------------------------------------------------------------------------ 16 51PEG WFPC2 IMAGE PC1-FIX F555W CLOCKS=YES 1 10 S ------------------------------------------------------------------------------------------------------------------------------------ 17 51PEG WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=0.5,CR-TOLERANCE=0, 1 200 S CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ 18 51PEG WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=0.5,CR-TOLERANCE=0, 1 200 S CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ 19 51PEG WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=0.5,CR-TOLERANCE=0, 1 600 S CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ 6845( 12) - 05/21/97 11:11 - [ 5] Visit: 02 Visit Requirements: ORIENT 60D TO 75D FROM 1 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 ------------------------------------------------------------------------------------------------------------------------------------ 20 51PEG WFPC2 IMAGE PC1-FIX F814W 1 0.11 S SEQ 20- 29 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 21 51PEG WFPC2 IMAGE PC1-FIX F555W 1 0.11 S ------------------------------------------------------------------------------------------------------------------------------------ 22 51PEG WFPC2 IMAGE PC1-FIX F555W 1 1.0 S ------------------------------------------------------------------------------------------------------------------------------------ 23 51PEG WFPC2 IMAGE PC1-FIX F814W 1 1.0 S ------------------------------------------------------------------------------------------------------------------------------------ 24 51PEG WFPC2 IMAGE PC1-FIX F814W CLOCKS=YES 1 10 S ------------------------------------------------------------------------------------------------------------------------------------ 25 51PEG WFPC2 IMAGE PC1-FIX F439W CLOCKS=YES 1 10 S ------------------------------------------------------------------------------------------------------------------------------------ 26 51PEG WFPC2 IMAGE PC1-FIX F555W CLOCKS=YES 1 10 S ------------------------------------------------------------------------------------------------------------------------------------ 27 51PEG WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=0.5,CR-TOLERANCE=0, 1 200 S CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ 28 51PEG WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=0.5,CR-TOLERANCE=0, 1 200 S CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ 29 51PEG WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=0.5,CR-TOLERANCE=0, 1 600 S CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ 6845( 12) - 05/21/97 11:11 - [ 6] Summary Form for Proposal 6845 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CLOCKS=YES CR-TOLERANCE=0 CR-SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category COOL STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SEQ 10-19 NON-INT ORIENT 60D TO 75D FROM 1 SEQ 20- 29 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F555W F439W ------------------------------------------------------------------------------------------------------------------------------------ Target Names 51PEG ------------------------------------------------------------------------------------------------------------------------------------