16286( 2) - 10-Jun-2020 14:17:25 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16286 Version: 2 Check-in Time: 10-Jun-2020 14:17:25 STScI Edit Number: 0 Title The First Double Helium White Dwarf LISA Verification Source ------------------------------------------------------------------------------------ Type Cycle GO 28 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Mukremin Kilic University of Oklahoma Norman Campus Y CoI: Dr. Warren R. Brown Smithsonian Institution Astrophysical N Observatory ------------------------------------------------------------------------------------ Abstract We propose to obtain low resolution ultraviolet spectroscopy of the newly identified 1201 s orbital period detached binary J2322+0509. This is the third shortest-period detached binary known, and it contains two He-core white dwarfs at a ~27 degree inclination. The low-inclination results in no visible photometric effects (e.g., eclipses, ellipsoidal variations), but makes this one of the strongest sources of gravitational waves in the mHz frequency range. Located 760 pc from the Sun, this binary has an estimated LISA 4-yr signal-to-noise ratio of 40. J2322+0509 is the first He+He white dwarf LISA verification binary, a source class that is predicted to account for one-third of all LISA ultra-compact binary detections. Here we request HST STIS observations in the far-ultraviolet to constrain the physical parameters of this binary precisely. The optical data on this system reveals about 15% contribution from the cooler secondary white dwarf, limiting the precision of our model atmosphere analysis on the primary white dwarf. The primary star is hot, and it dominates in the far-ultraviolet. Our STIS data will enable us to constrain the temperature and mass of the primary precisely, which in turn will constrain the radius and mass of the secondary star, and the inclination of the system. Well-measured white dwarf binaries will be among the best electromagnetic + gravitational wave laboratories for understanding the formation of compact objects, dynamical interactions and tides in binaries. J2322+0509 is one of the best such systems. ------------------------------------------------------------------------------------ Observations Description ------------------------ Our goal is to obtain low-resolution STIS spectroscopy of J2322+0509 in the TIME-TAG mode. Since our target has GALEX FUV=18.52 mag, we will obtain low resolution observations with the G140L grating. A S/N =20 STIS spectrum will enable us to constrain the mass of the primary white dwarf in this system precisely. Given the relatively low-amplitude of the radial velocity variations and the broad Lyman alpha line, orbital smearing will have no effect on our analysis of the STIS data. ------------------------------------------------------------------------------------ 16286( 2) - 10-Jun-2020 14:17:25 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 J2322+0509 STAR, DA RA=23H22M30.2030S, J2000 V = 18.6 GALEX FUV = 18.52 DEC=+05D09'42.06" Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 16286( 2) - 10-Jun-2020 14:17:25 - [ 3] Visit: 01 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 J2322+0509 STIS/CCD ACQ F28X50LP MIRROR ACQTYPE=POINT 1 5 S (5 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 J2322+0509 STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=5170 1 2205 S -MAMA G (2205 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 J2322+0509 STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=5170 1 2725 S -MAMA G (2725 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 J2322+0509 STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=5170 1 2725 S -MAMA G (2725 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 J2322+0509 STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=5170 1 2725 S -MAMA G (2725 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 | ------------------------------------------------------------------------------------------------------------------------------------ J2322+0509 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A J2322+0509 2 STIS/FUV TIME-TA 52X0.2 G140L 1425 none none none none 1 N/A -MAMA G J2322+0509 3 STIS/FUV TIME-TA 52X0.2 G140L 1425 none none none none 2 N/A -MAMA G J2322+0509 4 STIS/FUV TIME-TA 52X0.2 G140L 1425 none none none none 3 N/A -MAMA G J2322+0509 5 STIS/FUV TIME-TA 52X0.2 G140L 1425 none none none none 4 N/A -MAMA G 16286( 2) - 10-Jun-2020 14:17:25 - [ 4] Summary Form for Proposal 16286 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.2, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT, BUFFER-TIME=5170 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names J2322+0509 ------------------------------------------------------------------------------------------------------------------------------------