12865( 3) - 22-Aug-2012 18:58:58 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12865 Version: 3 Check-in Time: 22-Aug-2012 18:58:58 STScI Edit Number: 0 Title HD 188112 - a candidate Supernova Ia progenitor ------------------------------------------------------------------------------------ Type Cycle GO 20 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Ulrich Heber Universitat Erlangen-Nurnberg Y CoI: Dr. Stephan Geier Universitat Erlangen-Nurnberg N CoI: Prof. Wolfgang Hillebrandt Max-Planck-Institut fur Astrophysik N CoI: Prof. Friedrich Roepke Universitat Wurzburg, Astronomisches N Institut CoI: Dr. Markus Kromer Max-Planck-Institut fur Astrophysik N CoI: Dr. Stefan Taubenberger Max-Planck-Institut fur Astrophysik N CoI: Dr. Michael Fink Universitat Wurzburg, Astronomisches N Institut ------------------------------------------------------------------------------------ Abstract Several different explosion channels have been proposed for Type Ia Supernovae (SNe Ia), and tested against observations through hydrodynamic explosion simulations and radiative-transfer calculations. A promising scenario is the double detonation of a sub-Chandrasekhar-mass C/O white dwarf (WD), where a surface detonation in freshly accreted He subsequently triggers a detonation in the C/O core. The companion and He donor would likely be a low-mass He WD. Potential progenitor systems (i.e., binaries of a sufficiently massive C/O WD with a low-mass He WD) have never been observed so far. However, HD~188112 might be part of such a system. HD~188112 is a nearby, bright, radial-velocity variable He WD of 0.24 M$_\odot$, whose unseen companion has been inferred to be another WD of at least 0.73 M$_\odot$. The exact mass of the companion depends on the unknown inclination of the system. Assuming tidally locked rotation, the inclination can be determined measuring the broadening of metal lines due to rotation. Since the metallicity of HD 188112 is extremely low (1/100 solar), this measurement can only be performed in the UV, making the use of HST mandatory. If the mass of the companion of HD 188112 is confirmed to be between 0.95 and 1.05 M$_\odot$, the first candidate double-detonation SN Ia progenitor system has been found. ------------------------------------------------------------------------------------ Observations Description ------------------------ The project requires time series spectroscopy with E140H and E230. Time tag mode ist used for the NUV. The star is too bright in the FUV to use Time Tag mode. Thererfore observations are broken into a series of 22 exposures of 2 minutes duration. Real Time Justification 12865( 3) - 22-Aug-2012 18:58:58 - [ 2] ----------------------- No Calibration Justification ------------------------- standard Additional Comments ------------------- No ------------------------------------------------------------------------------------ 12865( 3) - 22-Aug-2012 18:58:58 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD-188112 STAR, SDB RA=19H54M31.4205S +/- 0.1", J2000 V = 10.22 +/- 0.1 DEC=-28D20'20.67" +/- 0.1" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 12865( 3) - 22-Aug-2012 18:58:58 - [ 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 HD-188112 STIS/CCD ACQ F28X50LP MIRROR 1 0.2 S ------------------------------------------------------------------------------------------------------------------------------------ 2 HD-188112 STIS/CCD ACQ/PEA 0.2X0.09 MIRROR 1 0.1 S K ------------------------------------------------------------------------------------------------------------------------------------ 3 HD-188112 STIS/NUV TIME-TA 0.2X0.09 E230H 2812 BUFFER-TIME=130 1 1040 S -MAMA G ------------------------------------------------------------------------------------------------------------------------------------ 4 HD-188112 STIS/FUV ACCUM 0.2X0.09 E140H 1343 22 120 S -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 5 HD-188112 STIS/NUV TIME-TA 0.2X0.09 E230H 2812 BUFFER-TIME=130 1 2860 S -MAMA G ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ HD-188112 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A HD-188112 2 STIS/CCD ACQ/PEA 0.2X0.09 MIRROR none none none none 1 N/A K HD-188112 3 STIS/NUV TIME-TA 0.2X0.09 E230H 2812 none none none none 1 N/A -MAMA G HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 1 none 1 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 2 none 1 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 3 none 1 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 4 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 5 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 6 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 7 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 8 none 2 N/A -MAMA 12865( 3) - 22-Aug-2012 18:58:58 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 9 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 10 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 11 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 12 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 13 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 14 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 15 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 16 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 17 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 18 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 19 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 20 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 21 none 2 N/A -MAMA HD-188112 4 STIS/FUV ACCUM 0.2X0.09 E140H 1343 none none 22 none 2 N/A -MAMA HD-188112 5 STIS/NUV TIME-TA 0.2X0.09 E230H 2812 none none none none 3 N/A -MAMA G 12865( 3) - 22-Aug-2012 18:58:58 - [ 6] Summary Form for Proposal 12865 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.2X0.09, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/PEAK, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=130 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements E140H, E230H, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD-188112 ------------------------------------------------------------------------------------------------------------------------------------