14600( 4) - 26-Dec-2016 16:18:18 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14600 Version: 4 Check-in Time: 26-Dec-2016 16:18:18 STScI Edit Number: 0 Title SDSS 1240+6710: a partially burnt supernova remnant ------------------------------------------------------------------------------------ Type Cycle GO 24 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Boris T. Gaensicke The University of Warwick Y CoI: Dr. Souza Oliveira Kepler Universidade Federal do Rio Grande do Sul N CoI: Prof. Detlev G. Koester Universitat Kiel N ------------------------------------------------------------------------------------ Abstract We have recently (Kepler et al. 2016, Science 352, 6281, April 1 issue) identified SDSSJ124043.01+671034.68 as a white dwarf with most peculiar characterstics. Instead of the usual hydrogen or helium, its atmosphere is composed almost purely of oxygen, the only other trace elements detected are neon, magnesium, and silicon; and it has a large transverse velocity of ~340km/s. The relatively low mass, 0.6Msun, and the non-detection of carbon strongly argue against SDSSJ1240+6710 being a canonical oxygen-neon core formed from the evolution of a single progenitor star with a mass of ~6.5-10Msun. The detection of silicon suggests that the progenitor of this white dwarf may have initiated oxygen-burning, and we argue that SDSSJ1240+6710 is the partially burnt remnant of an unusual thermonuclear supernova, of which a variety have been discovered by the ongoing large transient surveys. We propose to obtain COS ultraviolet spectroscopy of SDSSJ1240+6710 to measure (1) the abundances of phosphorus and sulfur, two other products of oxygen-burning, (2) significantly improve the upper limits on hydrogen (from Ly alpha) and carbon (1330/1335A resonance lines), (3) probe for traces of other nuclear burning, including nitrogen, iron, and nickel, and (4) accurately measure its effective temperature and mass. SDSSJ1240+6710 provides so far the unique opportunity to test the predictions of the rapidly growing number of theoretical stellar explosion models producing gravitationally bound remnants. ------------------------------------------------------------------------------------ Observations Description ------------------------ The purpose of this program is to obtain a S/N~20 spectrum of the white dwarf SDSS1240+6710 to improve on the photospheric abundances of O, Si, and Mg, and to search for absorption lines of S, P, and C. The target is located in the continiuous viewing zone (requested in Phase I), which allows to efficiently pack the required exposure time into four orbits. The star has GALEX FUV and NUV fluxes, and we carried out the ETC simulations with a model spectrum computed based on the abundances measured from optical spectroscopy. The star will be acquired with NUV imaging, after which G140L spectroscopy will be obtained using all four FP-POS settings. ------------------------------------------------------------------------------------ 14600( 4) - 26-Dec-2016 16:18:18 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSSJ124043. STAR, DZ RA=12H40M43.4424S +/- 0.069", J2000 V = 18.2 +/- 0.1 GALEX FUV=17.92 GALEX 00+671034.6 DEC=+67D10'35.94" +/- 0.096" NUV=17.5 Reference Frame: ICRS Extended: NO Comments: 2016/09/29: updated the proper motions from Gould et al. 2004ApJS..152..103G Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.03146930181601044 -0.0933 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 14600( 4) - 26-Dec-2016 16:18:18 - [ 3] Visit: 02 (SDSS1240+6710 COS G140L) Visit Requirements: CVZ On Hold Comments: Additional Comments: 2016-12-22: Updated target acquisition to use MIRRORB to avoid BOP violation. 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 SDSSJ124043 COS/NUV ACQ/IMA PSA MIRRORB 1 75 S (75 .00+671034. GE S) 6 Comments: Updated to use MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ 2 SDSSJ124043 COS/FUV TIME-TA PSA G140L 1105 FP-POS=1, BUFFER-TIME=1052 1 5357 S .00+671034. G (5357 S) 6 ------------------------------------------------------------------------------------------------------------------------------------ 3 SDSSJ124043 COS/FUV TIME-TA PSA G140L 1105 FP-POS=2, BUFFER-TIME=1052 1 5356 S .00+671034. G (5356 S) 6 ------------------------------------------------------------------------------------------------------------------------------------ 4 SDSSJ124043 COS/FUV TIME-TA PSA G140L 1105 FP-POS=3, BUFFER-TIME=1052 1 5356 S .00+671034. G (5356 S) 6 ------------------------------------------------------------------------------------------------------------------------------------ 5 SDSSJ124043 COS/FUV TIME-TA PSA G140L 1105 FP-POS=4, BUFFER-TIME=1052 1 5356 S .00+671034. G (5356 S) 6 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SDSSJ124043.00+6710 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A 34.6 GE SDSSJ124043.00+6710 2 COS/FUV TIME-TA PSA G140L 1105 none none none none 1 N/A 34.6 G SDSSJ124043.00+6710 3 COS/FUV TIME-TA PSA G140L 1105 none none none none 2 N/A 34.6 G SDSSJ124043.00+6710 4 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 N/A 34.6 G SDSSJ124043.00+6710 5 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 N/A 34.6 G 14600( 4) - 26-Dec-2016 16:18:18 - [ 4] Summary Form for Proposal 14600 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1052, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names SDSSJ124043.00+671034.6 ------------------------------------------------------------------------------------------------------------------------------------