16997( 3) - 18-Apr-2023 13:23:46 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16997 Version: 3 Check-in Time: 18-Apr-2023 13:23:46 STScI Edit Number: 0 Title Dynamical Masses of the Coldest Brown Dwarfs ------------------------------------------------------------------------------------ Type Cycle GO 30 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Trent J. Dupuy University of Edinburgh, Institute for Y Astronomy CoI: Dr. William Best University of Texas at Austin N CoI: Dr. Michael C. Liu University of Hawaii N CoI: Dr. Michael Line Arizona State University N CoI: Dr. Mark S. Marley University of Arizona N CoI: Mr. Mark William Phillips University of Hawaii at Manoa N ------------------------------------------------------------------------------------ Abstract On the cusp of the JWST era, we are still lacking mass measurements for the coldest brown dwarfs, even though mass is crucial for testing substellar models. We propose a 3-year orbit monitoring program to obtain the first sample of dynamical masses at temperatures of 400-800 K. With projected separations of only 1-3 AU, our targets are among the tightest and faintest substellar visual binaries ever found, discovered at the extreme limits of existing facilities. Resolved astrometry, combined with existing parallax data, is needed to measure their orbits, and only HST can deliver the high-precision monitoring required. These systems, composed entirely of T8-Y0 dwarfs, are likely to be the only such binaries amenable to direct mass measurements within the decade. ------------------------------------------------------------------------------------ Observations Description ------------------------ The goal of our observations is to obtain precise relative astrometry (~3-5 mas) for four brown dwarf binaries. Our data spanning 3 cycles will allow us to determine their orbits and thereby measure their dynamical masses. ACS/WFC offers a finer pixel scale than WFC3/IR and better sensitivity than WFC3/UVIS, both of which (high SNR, and better deblending of our tight 0.07"-0.11" binaries) are key to achieving our science goals. We use a standard 3-position dither sequence to guard against cosmic rays and to sample different parts of the detector in case our target lands on a bad pixel in a single pointing. We set the exposure times to fill the time available in each visit, which will yield SNR of ~30 for our faintest target (WISE0146, J=20.7) and will still be far from saturating any other of our sources in F850LP (the brightest is J=16.9). ------------------------------------------------------------------------------------ 16997( 3) - 18-Apr-2023 13:23:46 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 WISEJ014656. STAR, BROWN DWARF, T RA=01H46M56.2824S +/- 0.1", J2000 J = 20.69 66+423410.0 DEC=+42D34'9.66" +/- 0.1" Reference Frame: ICRS Extended: NO Comments: Astrometry measured from je4o01010_drz.fits; Proper motion and parallax from 2019ApJS..240...19K Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2020.542 -0.04091650775168676 -0.028 0.052 ------------------------------------------------------------------------------------------------------------------------------------ 2 WISEJ090649. STAR, BROWN DWARF, T RA=09H06M48.7872S +/- 0.1", J2000 J = 17.87 35+473538.5 DEC=+47D35'31.06" +/- 0.1" Reference Frame: ICRS Extended: NO Comments: Astrometry measured from je4o03010_drz.fits; Proper motion and parallax from 2019ApJS..240...19K Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2020.951 -0.05397342333954833 -0.710 0.048 ------------------------------------------------------------------------------------------------------------------------------------ 3 CFBDSIRJ1458 STAR, BROWN DWARF, T RA=14H58M29.4888S +/- 0.1", J2000 J = 19.66 29+101343 DEC=+10D13'37.96" +/- 0.1" Reference Frame: ICRS Extended: NO Comments: Astrometry measured from je4o05010_drz.fits; Proper motion and parallax from 2012ApJS..201...19D Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2020.489 0.011787283488098897 -0.380 0.031 ------------------------------------------------------------------------------------------------------------------------------------ 4 WISEPCJ20154 STAR, BROWN DWARF, T RA=20H15M46.5384S +/- 0.1", J2000 J = 16.91 6.27+664645. DEC=+66D46'48.90" +/- 0.1" 1 Reference Frame: ICRS Extended: NO Comments: Astrometry measured from je4o09010_drz.fits; Proper motion and parallax from 2019ApJS..240...19K Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2020.435 0.04903717438449096 0.428 0.43 ------------------------------------------------------------------------------------------------------------------------------------ 16997( 3) - 18-Apr-2023 13:23:46 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 3.034 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 85.29 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 16997( 3) - 18-Apr-2023 13:23:46 - [ 4] Visit: 01 (WISE0146) Visit Requirements: AFTER 01-MAR-2023:00:00:00 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WISEJ014656 ACS/WFC ACCUM WFC1-CTE F850LP 1 700 S PATTERN 1 1 .66+423410. see below 0 (2310 S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WISEJ014656.66+4234 1 ACS/WFC ACCUM WFC1-CTE F850LP 1 none none none 1 770.0 S 10.0 WISEJ014656.66+4234 1 ACS/WFC ACCUM WFC1-CTE F850LP 2 none none none 1 770.0 S 10.0 WISEJ014656.66+4234 1 ACS/WFC ACCUM WFC1-CTE F850LP 3 none none none 1 770.0 S 10.0 16997( 3) - 18-Apr-2023 13:23:46 - [ 5] Visit: 02 (WISE0906) Visit Requirements: 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WISEJ090649 ACS/WFC ACCUM WFC1-CTE F850LP 1 700 S PATTERN 1 1 .35+473538. see below 5 (2358 S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WISEJ090649.35+4735 1 ACS/WFC ACCUM WFC1-CTE F850LP 1 none none none 1 786.0 S 38.5 WISEJ090649.35+4735 1 ACS/WFC ACCUM WFC1-CTE F850LP 2 none none none 1 786.0 S 38.5 WISEJ090649.35+4735 1 ACS/WFC ACCUM WFC1-CTE F850LP 3 none none none 1 786.0 S 38.5 16997( 3) - 18-Apr-2023 13:23:46 - [ 6] Visit: 03 (CFBDSIR1458) Visit Requirements: AFTER 10-MAY-2023:00:00:00 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CFBDSIRJ145 ACS/WFC ACCUM WFC1-CTE F850LP 1 700 S PATTERN 1 1 829+101343 see below (2220 S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ CFBDSIRJ145829+1013 1 ACS/WFC ACCUM WFC1-CTE F850LP 1 none none none 1 740.0 S 43 CFBDSIRJ145829+1013 1 ACS/WFC ACCUM WFC1-CTE F850LP 2 none none none 1 740.0 S 43 CFBDSIRJ145829+1013 1 ACS/WFC ACCUM WFC1-CTE F850LP 3 none none none 1 740.0 S 43 16997( 3) - 18-Apr-2023 13:23:46 - [ 7] Visit: 04 (WISE2015) Visit Requirements: AFTER 01-MAY-2023:00:00:00 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WISEPCJ2015 ACS/WFC ACCUM WFC1-CTE F850LP 1 700 S PATTERN 1 1 46.27+66464 see below 5.1 (2559 S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WISEPCJ201546.27+66 1 ACS/WFC ACCUM WFC1-CTE F850LP 1 none none none 1 853.0 S 4645.1 WISEPCJ201546.27+66 1 ACS/WFC ACCUM WFC1-CTE F850LP 2 none none none 1 853.0 S 4645.1 WISEPCJ201546.27+66 1 ACS/WFC ACCUM WFC1-CTE F850LP 3 none none none 1 853.0 S 4645.1 16997( 3) - 18-Apr-2023 13:23:46 - [ 8] Visit: 05 (WISE0906 Repeat) Visit Requirements: 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WISEJ090649 ACS/WFC ACCUM WFC1-CTE F850LP 1 700 S PATTERN 1 1 .35+473538. see below 5 (2358 S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WISEJ090649.35+4735 1 ACS/WFC ACCUM WFC1-CTE F850LP 1 none none none 1 786.0 S 38.5 WISEJ090649.35+4735 1 ACS/WFC ACCUM WFC1-CTE F850LP 2 none none none 1 786.0 S 38.5 WISEJ090649.35+4735 1 ACS/WFC ACCUM WFC1-CTE F850LP 3 none none none 1 786.0 S 38.5 16997( 3) - 18-Apr-2023 13:23:46 - [ 9] Summary Form for Proposal 16997 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC1-CTE ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01-MAR-2023:00:00:00, AFTER 01-MAY-2023:00:00:00, AFTER 10-MAY-2023:00:00:00, PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F850LP ------------------------------------------------------------------------------------------------------------------------------------ Target Names CFBDSIRJ145829+101343, WISEJ014656.66+423410.0, WISEJ090649.35+473538.5, WISEPCJ201546.27+664645.1 ------------------------------------------------------------------------------------------------------------------------------------