12207( 3) - 09-Jul-2010 10:49:45 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12207 Version: 3 Check-in Time: 09-Jul-2010 10:49:45 STScI Edit Number: 0 Title The past and future evolution of the unique double white dwarf binary SDSS1257+5428 ------------------------------------------------------------------------------------ Type Cycle GO 18 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Carles Badenes Weizmann Institute of Science CoI: Dr. Boris T. Gaensicke The University of Warwick N CoI: Dr. Detlev G. Koester Universitat Kiel N CoI: Dr. Danny Steeghs The University of Warwick N CoI: Dr. Carles Badenes Weizmann Institute of Science N CoI: Dr. Avishay Gal-Yam Weizmann Institute of Science N CoI: Dr. Mukremin Kilic Harvard University N CoI: Dr. Fergal Mullally Princeton University N CoI: Dr. Susan Elizabeth Thompson University of Delaware N CoI: Prof. Thomas R. Marsh The University of Warwick Y ------------------------------------------------------------------------------------ Abstract The past 15 years has seen the unmasking of a vast population of close double white dwarfs (DWDs) with over 100 million in our Galaxy alone. So numerous are DWDs that they may themselves be the progenitors of significant populations such as accreting ultra-compact binary stars, isolated millisecond pulsars, hot subdwarfs and Type Ia supernovae. They are also expected to be the dominant sources for space-based gravitational wave astronomy. We have discovered a unique DWD, SDSS1257+5428, composed of two white dwarfs with masses of 0.2 and > 1 Msun, from the low and high-mass extremes of the white dwarf mass distribution. The high mass white dwarf is rapidly rotating, suggestive of accretion-induced spin-up, and yet in current models of the evoluton of such systems in which the low mass white dwarf should have emerged from a common envelope phase, there could not have been time for such spin-up to have occurred. Our current knowledge of the system, particular! ly the fainter high mass white dwarf, is limited by the blending of the two spectra at optical wavelengths. We don't know for instance whether or not the total system mass exceeds the Chandrasekhar mass. We will acquire ultraviolet spectra of SDSS1257+5428 which will pin down the masses and temperatures of the compoanent white dwarfs to define the past and future evolution of this puzzling system. ------------------------------------------------------------------------------------ Observations Description ------------------------ The aim of these observations is to record the FUV/NUV spectrum of the double-degenerate white dwarf SDSS1257+5428, and to use these data to determine accurate masses and temperatures for both components. This binary is composed of a cool, low-mass (~0.2Msun, ~8000K) plus a more massive, somewhat hotter (~0.8Msun, ~12000K) component (see arXiv:0910.2709, arXiv:1002.4677, arXiv:1003.2169). COS/G140L observations will occupy three orbits and cover the quasimolecular H2+ (1400A) and H2 (1600A) absorption lines, which are very temperature/pressure sensitive. Two orbits of STIS/G230L observations will delineate the spectral energy distribution across the NUV range. 12207( 3) - 09-Jul-2010 10:49:45 - [ 2] Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 12207( 3) - 09-Jul-2010 10:49:45 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSSJ125733. STAR, DA RA=12H57M33.6900S +/- 0.083", J2000 V = 16.84 +/- 0.04 Swift: UVW2(2030A) 64+542850.5 DEC=+54D28'50.50" +/- 0.083" 1.3e-15erg/cm2/s/A UVW1(2634A) 1.0e-15erg/cm2/s/A Reference Frame: ICRS Comments: No GALEX data, but the UV fluxes are well-established from Swift/UVOT observations (Swift target 31472, observations 001 - 007). Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 12207( 3) - 09-Jul-2010 10:49:45 - [ 4] 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSSJ125733 COS/NUV ACQ/SEA PSA MIRRORA SCAN-SIZE=2, STEP-SIZE=1.767 1 7 S .64+542850. RCH 5 ------------------------------------------------------------------------------------------------------------------------------------ 2 SDSSJ125733 COS/NUV ACQ/IMA PSA MIRRORA 1 7 S .64+542850. GE 5 ------------------------------------------------------------------------------------------------------------------------------------ 3 SDSSJ125733 COS/FUV TIME-TA PSA G140L 1280 BUFFER-TIME=1500, FLASH=YES, 1 2537 S .64+542850. G FP-POS=1 5 ------------------------------------------------------------------------------------------------------------------------------------ 4 SDSSJ125733 COS/FUV TIME-TA PSA G140L 1280 BUFFER-TIME=1500, FLASH=YES, 1 1830 S .64+542850. G FP-POS=1 5 ------------------------------------------------------------------------------------------------------------------------------------ 5 SDSSJ125733 COS/FUV TIME-TA PSA G140L 1280 BUFFER-TIME=1500, FLASH=YES, 1 1210 S .64+542850. G FP-POS=4 5 ------------------------------------------------------------------------------------------------------------------------------------ 6 SDSSJ125733 COS/FUV TIME-TA PSA G140L 1280 BUFFER-TIME=1500, FLASH=YES, 1 3159 S .64+542850. G FP-POS=4 5 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SDSSJ125733.64+5428 1 COS/NUV ACQ/SEA PSA MIRRORA none none none none 1 N/A 50.5 RCH SDSSJ125733.64+5428 2 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A 50.5 GE SDSSJ125733.64+5428 3 COS/FUV TIME-TA PSA G140L 1280 none none none none 1 N/A 50.5 G SDSSJ125733.64+5428 4 COS/FUV TIME-TA PSA G140L 1280 none none none none 2 N/A 50.5 G SDSSJ125733.64+5428 5 COS/FUV TIME-TA PSA G140L 1280 none none none none 2 N/A 50.5 G SDSSJ125733.64+5428 6 COS/FUV TIME-TA PSA G140L 1280 none none none none 3 N/A 50.5 G 12207( 3) - 09-Jul-2010 10:49:45 - [ 5] Visit: 02 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSSJ125733 STIS/CCD ACQ F28X50LP MIRROR ACQTYPE=POINT 1 5 S .64+542850. 5 ------------------------------------------------------------------------------------------------------------------------------------ 2 SDSSJ125733 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=250 1 1500 S .64+542850. -MAMA G see below 5 ------------------------------------------------------------------------------------------------------------------------------------ 3 SDSSJ125733 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=250 1 1500 S .64+542850. -MAMA G see below 5 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SDSSJ125733.64+5428 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A 50.5 SDSSJ125733.64+5428 2 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 1 2505.0 S 50.5 -MAMA G SDSSJ125733.64+5428 3 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 2 3172.0 S 50.5 -MAMA G 12207( 3) - 09-Jul-2010 10:49:45 - [ 6] Summary Form for Proposal 12207 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.5, F28X50LP, PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV, STIS/CCD, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ, ACQ/IMAGE, ACQ/SEARCH, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT, BUFFER-TIME=1500, BUFFER-TIME=250, FLASH=YES, FP-POS=1, FP-POS=4, SCAN-SIZE=2, STEP-SIZE=1.767 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, G230L, MIRROR, MIRRORA ------------------------------------------------------------------------------------------------------------------------------------ Target Names SDSSJ125733.64+542850.5 ------------------------------------------------------------------------------------------------------------------------------------