Final!2104383883Assigned ID: 2146
----- Attempting Submission 1 (Fri Apr 09 19:29:21 GMT 2021) -----
HST Phase I Proposal 2146 successfully submitted.
Receipt: # 2146-1
----- Attempting Submission 2 (Fri Apr 09 23:38:48 GMT 2021) -----Timing requirements based on obtaining data > 1 year from the last orbit monitoring observation from the previous iteration of this long-term program.-265804507----- Attempting Submission 1 (Fri Jul 16 12:48:24 GMT 2021) -----
----- Attempting Submission 2 (Thu Sep 14 12:31:43 GMT 2023) -----Dynamical Masses of the Coldest Brown DwarfsOn 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.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).Dr. Will Best has extensive experience using high-resolution imaging to study brown dwarfs and testing substellar models, and he helped develop this sample.
Dr. Trent Dupuy has expertise on dynamical masses of ultracool dwarfs, astrometry, testing evolutionary and atmospheric models and the binaries in this proposal. He led the work that developed the proposed sample with adaptive optics imaging and HST data.
Dr. Michael Line is an expert on the retrievals approach to modeling ultracool atmospheres, especially spectra of late-T dwarfs.
Dr. Michael Liu is an expert on ultracool atmospheres and dynamical masses of brown dwarfs and was a key contributor in developing the proposed sample, and he led the adaptive optics imaging that discovered these binaries.
Dr. Mark Marley and Dr. Mark Phillips are leading theorists on modeling ultracool atmospheres and will be able provide the latest grid models for use in our analysis.Stellar Physics and Stellar Types6falsefalsefalsefalsefalsefalsefalsefalseSUPPORTEDSTARBROWN DWARFTNOAstrometry measured from je4o01010_drz.fits;
Proper motion and parallax from 2021ApJS..253....7KJ2000J2000J = 20.69STARBROWN DWARFTNOAstrometry measured from je4o03010_drz.fits;
Proper motion and parallax from 2021ApJS..253....7KJ2000J2000J = 17.87STARBROWN DWARFTNOAstrometry measured from je4o05010_drz.fits;
Proper motion and parallax from 2012ApJS..201...19DJ2000J2000J = 19.66STARBROWN DWARFTNOAstrometry measured from je4o09010_drz.fits;
Proper motion and parallax from 2021ApJS..253....7KJ2000J2000J = 16.91ACS/WFCImagingNoNoF850LPACS/WFCImagingNoNoF850LPACS/WFCImagingNoNoF850LPACS/WFCImagingNoNoF850LPACS/WFCImagingNoNoF850LPACS/WFCImagingNoNoF850LPACS/WFCImagingNoNoF850LPACS/WFCImagingNoNoF850LPACS/WFCImagingNoNoF850LPACS/WFCImagingNoNoF850LPACS/WFCImagingNoNoF850LPACS/WFCImagingNoNoF850LPPOS-TARGDITHER3.034LINEfalsefalse385.29ACS-WFC-DITHER-LINE1false/System/Volumes/Data/solaris/user1/royle/OP-cache/17412-v01.xmlThe scheduling data was generated by CASM 31.1.CASM was run in Phase II mode.1719535728000264.64614844989126(Tic-Visit
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