9394( 2) - 02/15/02 10:27 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9394 Version: 2 Check-in Date: 15-Feb-2002 10:27:02 1.Proposal Title: Halo Microlensing: Direct Detection of a Microlens ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Kem Cook Lawrence Livermore National Laboratory CoI: Ms. Cailin Nelson Lawrence Livermore National Lab N CoI: Dr. Andrew Drake Lawrence Livermore National Lab N CoI: Dr. Stefan Keller Lawrence Livermore National Lab N ------------------------------------------------------------------------------------ 5. Abstract The MACHO project has recently released 5.7 years of LMC microlensing data, presenting 17 candidate microlensing events. These events suggest an 8-50\ MACHO halo and a most likely MACHO mass of 0.2-0.9 M_\odot. However, nearly a decade after the first reported event (Alcock et al. 1993) there still remains much debate about the nature and location of the lensing matter. MACHO has also obtained WFPC2 follow- up data of the microlensing source stars, to date we have observed 16 candidates with HST. The WFPC2 follow-up data of MACHO event LMC-5 provided unexpected insight into the nature of the lens. This image revealed a very red, faint object displaced by 0.134^ from the source star which may well be the first direct detection of the dark matter component (lens) of a microlensing event. A second epoch of WFPC2 photometry will verify the proper motion of the lens and allow for a parallax measurement of its distance. ------------------------------------------------------------------------------------ 9394( 2) - 02/15/02 10:27 - [ 2] Observations Description ------------------------ We propose to obtain two epochs of one field in the LMC with ACS in order to determine both the proper motion and parallactic motion of the lens component of the MACHO event LMC-5 microlensing system. A previous WFPC2 image of this system will serve as a first epoch. We will use HRC of the ACS for maximum sampling of the stellar PSF. The observations will consist of 1 visit of 2 orbits to obtain well dithered images in two colors, followed approximately six months later by 1 visit of 1 orbit to obtain a second HRC epoch in just one color. The first of these visits should be scheduled such that the parallactic motion is maximally perpendicular to the proper motion over the six month separation period (see Figure 1). Each of the two visits will image the target in the F606W bandpass. This bandpass is a compromise designed to critically sample the PSF while minimizing possible red halo problems in the redder bandpasses. One visit will also image the target in the F814W bandpass to obtain a (V-I) color. Each orbit will consist of 6 x 300 second exposures which will yield better then 1\ and microlens and allow astrometry accurate to better then 1/50 of a pixel. Real Time Justification ----------------------- The 3 orbits of observations of MACHO event LMC-5 (STAR-0516- 7029) are time critical. We wish to solve for both the proper motion and parallactic motion of the lens by combining two HRC epochs with a previous Cycle 7 WFPC2 epoch. In order to accomplish this the two HRC epochs must be spaced approximately 6 months apart and scheduled such that the parallactic motion over this time period is maximally perpendicular to the proper motion. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9394( 2) - 02/15/02 10:27 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 STAR-0516- STAR, M V-IV RA=05H 16M 41S +/- 1S, DEC=-70D J2000 V = 22.7+/-0.1 7029 29' 18" +/- 1" V-I = 3.2+/-0.1 Coordinate Source: HST_IMAGE 9394( 2) - 02/15/02 10:27 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-HRC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 6 Point_Spacing 0.198 Coordinate_Frame POS-TARG Pattern_Orient 44.28 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 9394( 2) - 02/15/02 10:27 - [ 5] Visit: 01 Visit Priority: Visit Requirements: BETWEEN 30-Jun-2002 AND 28-Jul-2002 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 STAR-0516-7 ACS/HR ACCUM HRC F606W GAIN=2,CR-SPLIT=NO 1 400 S PATTERN 1 1 029 C ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR-0516-7 ACS/HR ACCUM HRC F814W GAIN=2,CR-SPLIT=NO 1 400 S PATTERN 1 2 029 C ------------------------------------------------------------------------------------------------------------------------------------ 9394( 2) - 02/15/02 10:27 - [ 6] Visit: 02 Visit Priority: Visit Requirements: BETWEEN 02-Jan-2003 AND 01-Feb-2003 ORIENT 179D TO 181D FROM 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 STAR-0516-7 ACS/HR ACCUM HRC F606W GAIN=2,CR-SPLIT=NO 1 400 S PATTERN 1 1 029 C ------------------------------------------------------------------------------------------------------------------------------------ 9394( 2) - 02/15/02 10:27 - [ 7] Summary Form for Proposal 9394 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures HRC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/HRC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters GAIN=2 CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 30-Jun-2002 AND 28-Jul-2002 PATTERN 1 1 PATTERN 1 2 BETWEEN 02-Jan-2003 AND 01-Feb-2003 ORIENT 179D TO 181D FROM 01 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names STAR-0516-7029 ------------------------------------------------------------------------------------------------------------------------------------