9307( 3) - 09/25/01 10:18 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9307 Version: 3 Check-in Date: 25-Sep-2001 10:18:11 1.Proposal Title: Possible Resolution of Gravitationally Lensed Images Due to an Intermediate Black Hole in the Galactic Disk ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO/DD 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: David Bennett University of Notre Dame CoI: Prof. Sun Hong Rhie University of Notre Dame N CoI: Dr. Przemyslaw R. Wozniak Los Alamos National Laboratory N ------------------------------------------------------------------------------------ 5. Abstract We propose WFPC2 images of microlensing event MACHO-99-BLG-22/OGLE-1999-BUL-32 which is likely to be a black hole. A likelihood analysis of this event reveals two likelihood function peaks based upon the data for this event and a standard Galactic model: he highest peak indicates a lens of ~130 Msun at a distance of ~500 pc, and the 2nd peak indicates a lens of 3-4 Msun at a distance of 6 kpc. These two different peaks are for lenses with disk and bulge kinematics, respectively. If the high-mass model is correct, then HST observations will reveal the two lensed images with magnitudes of I = 19.2 and I = 22.1 separated by about 0.12 arc sec. We have asked for two orbits for BVI observations to confirm the microlensing achromaticity prediction and to get the higher resolution available at shorter wavelengths.If we succeed in resolving the microlensing event, the separation measurement, when combined with the microlensing parallax measurement, will tell us the mass of the lens to 10-20% accuracy. ------------------------------------------------------------------------------------ 9307( 3) - 09/25/01 10:18 - [ 2] Observations Description ------------------------ Target: Microlensing Event MACHO-99-BLG-22/OGLE-1999-BUL-3218 Coordinates: RA 05 05.3 DEC -28 34 42 (J2000) Instrument: WFPC2 Filters: F450W, F555W, and F814W exposure times: F450W - 1 full orbit F555W - 2/3 of an orbit F814W - 1/3 of an orbit Real Time Justification ----------------------- The proposed observations are time critical since the lensing event is nearly over and the minor image will soon be very faint and very difficult to observe. If the proposed observations can be taken before the source crosses the Sun- avoidance line in early November, the minor image will be less than 3 magnitudes fainter than the major image which is expected to be about ~0.12 arc sec away. But if we wait until the start of Cycle 11 observations, the minor image will be at least 4 magnitudes fainter. While the 4-magnitude contrast at a separation of ~0.12 arc sec may still be detectable, the early observations will provide a much higher signal-to-noise test of lens properties like achromaticity. Also, the separation prediction is not very certain. If the true separation is smaller, then our chances of detecting the minor image will be much better if we can get an image as soon as possible. This proposal was not possible before the recent OGLE collaboration paper: astro-ph/0108312. It is our further analysis of this event made possible by the data release accompanying this paper that has revealed this opportunity. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9307( 3) - 09/25/01 10:18 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 99-BLG-22 STAR, BULGE, G V-IV RA=18H 5M 5.3S +/- 2", DEC=-28D J2000 V = 21.0+/-0.2 34' 42" +/- 2" V-I = 1.4+/-0.1 Coordinate Source: IMAGE_TIED_TO_GSC_FRAME 9307( 3) - 09/25/01 10:18 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type SPIRAL Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.023 Coordinate_Frame POS-TARG Pattern_Orient 0 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFPC2-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.559017 Coordinate_Frame POS-TARG Pattern_Orient 26.565051 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 9307( 3) - 09/25/01 10:18 - [ 5] Visit: 01 Visit Priority: Visit Requirements: BETWEEN 20-Sep-2001 AND 08-Nov-2001 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 99-BLG-22 WFPC2 IMAGE PC1 F814W ATD-GAIN=7 1 400 S PATTERN 2 10 ------------------------------------------------------------------------------------------------------------------------------------ 20 99-BLG-22 WFPC2 IMAGE PC1 F555W ATD-GAIN=7 1 400 S PATTERN 2 20 ------------------------------------------------------------------------------------------------------------------------------------ 9307( 3) - 09/25/01 10:18 - [ 6] Summary Form for Proposal 9307 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ATD-GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO/DD ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 20-Sep-2001 AND 08-Nov-2001 PATTERN 2 10 PATTERN 2 20 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names 99-BLG-22 ------------------------------------------------------------------------------------------------------------------------------------