12598( 2) - 11-Jul-2011 13:09:15 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12598 Version: 2 Check-in Time: 11-Jul-2011 13:09:15 STScI Edit Number: 0 Title HST Observations of Astrophysically Important Visual Binaries: Calibrating Sirius and Procyon ------------------------------------------------------------------------------------ Type Cycle GO 19 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Howard E. Bond Space Telescope Science Institute CoI: Prof. Martin Barstow University of Leicester N CoI: Dr. Matthew Burleigh University of Leicester N CoI: Dr. Ronald L. Gilliland Space Telescope Science Institute N CoI: Dr. Terrence M. Girard Yale University N CoI: Dr. Donald H. Gudehus Georgia State University Research N Foundation CoI: Dr. Jay B. Holberg University of Arizona N CoI: Dr. Edmund Nelan Space Telescope Science Institute N CoI: Dr. Gail Schaefer Georgia State University Research N Foundation ------------------------------------------------------------------------------------ Abstract We have an ongoing long-term program, renewed in Cycle 18 for 3 years, in which we are imaging several important visual binaries, including Sirius and Procyon. The aims of this astrometric program are to determine precise dynamical masses for the white-dwarf and main-sequence components of the binaries, and to search for (or set limits on) third bodies in the systems down to planetary masses. With the advent of WFC3 in our program, we are forced to saturate the images of Sirius A and Procyon A, and instead use the diffraction spikes to infer their centroid locations. In order to calibrate the use of the spikes against the conventional method of centroiding an unsaturated image, which is the method used for the much fainter white-dwarf companions, we request one orbit for imaging of a fainter A-type star. For this star it is possible to obtain both unsaturated images for conventional centroiding and deeper saturated images to which we can apply our diffraction-spike algorithm and derive the offsets. We can thus apply corrections to our diffraction-spike-based astrometry of the saturated Sirius A and Procyon A images, reducing the systematic errors to below 1 mas, and setting tight limits on third bodies. We will not request any additional funding if this supplemental request is approved, and we will waive the proprietary period. ------------------------------------------------------------------------------------ Observations Description ------------------------ These observations of an 8th-magnitude A5 V star are being made in order to calibrate the method of using diffraction spikes to centroid images of bright, overexposed stars in WFC3/UVIS images. We have a separate program of imaging of the bright stars Sirius and Procyon with the F953N filter. These images are necessarily overexposed because there is no way to take unsaturated WFC3 images 12598( 2) - 11-Jul-2011 13:09:15 - [ 2] of these very bright stars. To determine whether there are systematic offsets from the true centroids and centroids determined from the diffraction spikes, we will observe the 8th-magnitude star with the same filter and UVIS aperture used for Sirius and Procyon, and will combine unsaturated 5-sec exposures with saturated ~600 sec exposures. We will use the same 4-point dither pattern being used for the two bright stars. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 12598( 2) - 11-Jul-2011 13:09:15 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD23886 STAR, A4-A9 V-IV RA=03H49M25.9833S +/- 0.1", J2000 V = 8.01 +/- 0.02 A5 V DEC=+24D14'51.74" +/- 0.1" Reference Frame: ICRS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000. 0.0015427723746289335 -.0425 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 12598( 2) - 11-Jul-2011 13:09:15 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ 12598( 2) - 11-Jul-2011 13:09:15 - [ 5] Visit: 01 Visit Requirements: PCS MODE FINE; SCHED 30% On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD23886 WFC3/UVI ACCUM UVIS2-C51 F953N CR-SPLIT=NO 1 5 S PATTERN 1 1-2 S 2C-SUB ------------------------------------------------------------------------------------------------------------------------------------ 2 HD23886 WFC3/UVI ACCUM UVIS2-C51 F953N CR-SPLIT=NO 1 500 S S 2C-SUB see below ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ HD23886 1 WFC3/UVI ACCUM UVIS2-C5 F953N 1 none none none 1 N/A S 12C-SUB HD23886 1 WFC3/UVI ACCUM UVIS2-C5 F953N 2 none none none 1 N/A S 12C-SUB HD23886 1 WFC3/UVI ACCUM UVIS2-C5 F953N 3 none none none 1 N/A S 12C-SUB HD23886 1 WFC3/UVI ACCUM UVIS2-C5 F953N 4 none none none 1 N/A S 12C-SUB HD23886 2 WFC3/UVI ACCUM UVIS2-C5 F953N 1 none none none 1 631.0 S S 12C-SUB HD23886 2 WFC3/UVI ACCUM UVIS2-C5 F953N 2 none none none 1 631.0 S S 12C-SUB HD23886 2 WFC3/UVI ACCUM UVIS2-C5 F953N 3 none none none 1 631.0 S S 12C-SUB HD23886 2 WFC3/UVI ACCUM UVIS2-C5 F953N 4 none none none 1 631.0 S S 12C-SUB 12598( 2) - 11-Jul-2011 13:09:15 - [ 6] Summary Form for Proposal 12598 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C512C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1-2, PCS MODE FINE, SCHED 30% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F953N ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD23886 ------------------------------------------------------------------------------------------------------------------------------------