12483( 2) - 10-Jun-2011 17:13:40 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12483 Version: 2 Check-in Time: 10-Jun-2011 17:13:40 STScI Edit Number: 0 Title What is the origin of the hottest known white dwarf? ------------------------------------------------------------------------------------ Type Cycle GO 19 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Klaus Werner Universitat Tubingen, Institut fur Astronomie & Astrophysik CoI: Dr. Thomas Rauch Universitat Tubingen, Institut fur N Astronomie & Astrophysik ------------------------------------------------------------------------------------ Abstract KPD0005+5106 is the hottest known white dwarf (Teff=200, 000 K). It has a helium-dominated atmosphere with trace amounts of light metals. Our recent analysis places the star in a region of the HRD where very weak stellar winds prevent gravitational settling of heavy elements. Therefore, the surface composition allows to conclude on the evolutionary history. We speculate that KPD0005+5106 represents a third post-AGB evolutionary sequence, which is distinct from the canonical hydrogen-rich and hydrogen-deficient sequences. The star could be the long-searched progeny of the RCrB stars, which are believed to be the result of a double-degenerate merger. We found that the metal abundances in KPD0005+5106 are rather similar to those in RCrB stars, however, a claim on the evolutionary link is premature. The abundance determinations for KPD0005+5106 are afflicted with large errors because of the relatively large uncertainty in Teff. Our immediate aim is to use ionization balances of metals in order to determine Teff to high precision, which is a prerequisite to tightly constrain abundances. HST-UV spectroscopy is the only means to reach this goal. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will perform short-slit (0.2"x0.2") medium-dispersion UV spectroscopy of KPD0005 in the STIS/FUV-MAMA and NUV-MAMA configurations with gratings E140M and E230M (two wavelength settings), respectively, in order to cover the wavelength range 1150-3100A. This provides the spectral resolution (~30, 000) needed for the quantitative analysis of narrow metal lines. STIS ETC was used to determine exposure times necessary to achieve the required S/N~20-40. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- 12483( 2) - 10-Jun-2011 17:13:40 - [ 2] ------------------------------------------------------------------------------------ 12483( 2) - 10-Jun-2011 17:13:40 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 KPD0005+5106 STAR, WDO RA=00H08M18.1500S +/- 0.1", J2000 V = 13.32 +/- 0.1 DEC=+51D23'17.00" +/- 0.1" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 12483( 2) - 10-Jun-2011 17:13:40 - [ 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 KPD0005+510 STIS/CCD ACQ F28X50LP MIRROR 1 0.2 S 6 ------------------------------------------------------------------------------------------------------------------------------------ 2 KPD0005+510 STIS/NUV ACCUM 0.2X0.2 E230M 1978 1 300 S 6 -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 3 KPD0005+510 STIS/NUV ACCUM 0.2X0.2 E230M 2707 1 450 S 6 -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 4 KPD0005+510 STIS/FUV ACCUM 0.2X0.2 E140M 1425 1 1215 S 6 -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 5 KPD0005+510 STIS/FUV ACCUM 0.2X0.2 E140M 1425 1 3193 S 6 -MAMA ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ KPD0005+5106 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A KPD0005+5106 2 STIS/NUV ACCUM 0.2X0.2 E230M 1978 none none none none 1 N/A -MAMA KPD0005+5106 3 STIS/NUV ACCUM 0.2X0.2 E230M 2707 none none none none 1 N/A -MAMA KPD0005+5106 4 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none none none 1 N/A -MAMA KPD0005+5106 5 STIS/FUV ACCUM 0.2X0.2 E140M 1425 none none none none 2 N/A -MAMA 12483( 2) - 10-Jun-2011 17:13:40 - [ 5] Summary Form for Proposal 12483 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.2X0.2, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements E140M, E230M, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names KPD0005+5106 ------------------------------------------------------------------------------------------------------------------------------------