13290( 3) - 05-Aug-2013 15:21:04 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13290 Version: 3 Check-in Time: 05-Aug-2013 15:21:04 STScI Edit Number: 0 Title The hypervelocity hot subdwarf US 708 - remnant of a double-detonation SN Ia? ------------------------------------------------------------------------------------ Type Cycle GO 21 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Stephan Geier European Southern Observatory - Germany Y CoI: Dr. Ulrich Heber Universitat Erlangen-Nurnberg N ------------------------------------------------------------------------------------ Abstract Type Ia supernovae (SN Ia) are the most important standard candles for measuring the expansion history of the universe. The thermonuclear explosion of a white dwarf can explain their observed properties, but neither the progenitor systems nor any stellar remnants have been conclusively identified. Underluminous SN Ia have been proposed to originate from a so-called double-detonation of a white dwarf. After a critical amount of helium is deposited on the surface through accretion from a close companion, the helium is ignited causing a detonation wave that triggers the explosion of the white dwarf itself. The helium star will then be ejected at so large a velocity that it will escape the Galaxy. The predicted properties of this remnant are an excellent match to the so-called hypervelocity star US 708, a hot, helium-rich star moving at more than 750 km/s, sufficient to leave the Galaxy. Here we propose medium-resolution COS spectroscopy to measure the vsini of the hypervelocity He-sdO US 708 for the first time and to search for abundance anomalies caused by pollution through an SN Ia event. This will allow us to test the double-detonation scenario with sdB donor empirically. ------------------------------------------------------------------------------------ Observations Description ------------------------ Using COS in spectroscopic FUV mode with the G140L grating, we aim at taking $2$ orbits of spectroscopy of US\, 708 ($V=18.8\, {\rm mag}$) to achieve an S/N of $\sim60$ sufficient to perform a full quantitative spectral analysis. At a resolution of $\sim1\, {\rm \AA}$ we will be able to measure $v_{\rm rot}\sin{i}$ with sufficient accuracy, if it exceeds about $100\, {\rm km\, s^{-1}}$. In addition, we will observe the bright, single He-sdO WD\, 0958$-$118 ($V=13.8\, {\rm mag}$) as comparison star. It has similar atmospheric parameters as US\, 708, but is a slow rotator. Using the same setup, we will easily achieve an S/N of $>100$ within one orbit splitting the observation into short single exposures to avoid saturation. There are no scheduling constraints and both sources are non-variable. Real Time Justification ----------------------- Calibration Justification ------------------------- 13290( 3) - 05-Aug-2013 15:21:04 - [ 2] Additional Comments ------------------- ------------------------------------------------------------------------------------ 13290( 3) - 05-Aug-2013 15:21:04 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 BGK2006-HV-2 STAR, SDO RA=09H33M20.8650S +/- 0.005", J2000 V = 18.8 DEC=+44D17'5.52" +/- 0.005" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 2 CD-314800 STAR, SDO RA=07H36M30.1966S +/- 0.00095", J2000 V = 10.56 +/- 0.003 DEC=-32D12'43.68" +/- 0.00122" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.0018367050938164545 0.041409999999999995 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 13290( 3) - 05-Aug-2013 15:21:04 - [ 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BGK2006-HV- COS/FUV ACQ/PEA PSA G140L 1105 1 5 S (5 S) 2 KXD ------------------------------------------------------------------------------------------------------------------------------------ 2 BGK2006-HV- COS/FUV ACQ/PEA PSA G140L 1105 CENTER=FLUX-WT-FLR, NUM-POS=5, 1 12 S (12 2 KD STEP-SIZE=0.9 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 BGK2006-HV- COS/FUV TIME-TA PSA G140L 1105 FLASH=YES, BUFFER-TIME=2740, 1 1200 S 2 G FP-POS=ALL (4800 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 | ------------------------------------------------------------------------------------------------------------------------------------ BGK2006-HV-2 1 COS/FUV ACQ/PEA PSA G140L 1105 none none none none 1 N/A KXD BGK2006-HV-2 2 COS/FUV ACQ/PEA PSA G140L 1105 none none none none 1 N/A KD BGK2006-HV-2 3 COS/FUV TIME-TA PSA G140L 1105 none none none 1 1 N/A G BGK2006-HV-2 3 COS/FUV TIME-TA PSA G140L 1105 none none none 2 1 N/A G BGK2006-HV-2 3 COS/FUV TIME-TA PSA G140L 1105 none none none 3 2 N/A G BGK2006-HV-2 3 COS/FUV TIME-TA PSA G140L 1105 none none none 4 2 N/A G 13290( 3) - 05-Aug-2013 15:21:04 - [ 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CD-314800 COS/FUV ACQ/PEA BOA G140L 1105 1 2.6 S (2.6 KXD S) ------------------------------------------------------------------------------------------------------------------------------------ 2 CD-314800 COS/FUV ACQ/PEA BOA G140L 1105 CENTER=FLUX-WT-FLR, NUM-POS=5, 1 15 S (15 KD STEP-SIZE=0.9 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 CD-314800 COS/FUV TIME-TA BOA G140L 1105 FP-POS=ALL, BUFFER-TIME=336 1 50 S G see below (1732 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 | ------------------------------------------------------------------------------------------------------------------------------------ CD-314800 1 COS/FUV ACQ/PEA BOA G140L 1105 none none none none 1 N/A KXD CD-314800 2 COS/FUV ACQ/PEA BOA G140L 1105 none none none none 1 N/A KD CD-314800 3 COS/FUV TIME-TA BOA G140L 1105 none none none 1 1 433.0 S G CD-314800 3 COS/FUV TIME-TA BOA G140L 1105 none none none 2 1 433.0 S G CD-314800 3 COS/FUV TIME-TA BOA G140L 1105 none none none 3 1 433.0 S G CD-314800 3 COS/FUV TIME-TA BOA G140L 1105 none none none 4 1 433.0 S G 13290( 3) - 05-Aug-2013 15:21:04 - [ 6] Summary Form for Proposal 13290 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures BOA, PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAKD, ACQ/PEAKXD, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=2740, BUFFER-TIME=336, CENTER=FLUX-WT-FLR, FLASH=YES, FP-POS=ALL, NUM-POS=5, STEP-SIZE=0.9 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names BGK2006-HV-2, CD-314800 ------------------------------------------------------------------------------------------------------------------------------------