12869( 3) - 20-Jun-2012 21:06:53 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12869 Version: 3 Check-in Time: 20-Jun-2012 21:06:53 STScI Edit Number: 2 Title The chemical diversity of extra-solar planetary systems ------------------------------------------------------------------------------------ Type Cycle GO 20 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Boris T. Gaensicke The University of Warwick Y CoI: Prof. Detlev G. Koester Universitat Kiel N CoI: Dr. Jay Farihi University of Leicester N CoI: Mr. Jonathan Girven The University of Warwick N ------------------------------------------------------------------------------------ Abstract Over the past few years, it has become increasingly clear that the most plausible scenario to explain the infrared excess observed at ~30 white dwarfs is accretion from rocky planetary material - suggesting that these white dwarfs may have had, or may still have terrestial planets as well. This hypothesis is corroborated through the detection of volatile-depleted abundance patterns in the photospheres of these white dwarfs. We are carrying out a large COS snapshot survey of 150 white dwarfs, with the aim to determine the fraction of remnants of planetary systems around young (20-200Myr) white dwarfs. At the time of writing, we have observed 94 white dwarfs, and find pollution by Si, one of the major constituents of the Earth, in ~25% of them. In about a dozen stars, we detect multiple (up to nine) different elements, and show that their abundance pattern is broadly consistent with that of bulk-Earth: extremely volatile depleted, in particular in C/Si. However, there are two exceptions: WD1013+256 and WD1647+375 show strong lines of both Si and C. We have ruled out accretion from the wind of a nearby low-mass companion, and the only explanation is accretion of planetary debris that is significantly richer in C than the bulk Earth. This discovery is of substantial significance within the current discussion on variations in the exo-planet chemistry. We propose to re-observe these two white dwarfs, doubling the signal-to-noise ratio with respect to our very short Snapshot spectra, to and to determine the abundances of additional elements, including Fe, O, and possibly Ni and N. ------------------------------------------------------------------------------------ Observations Description ------------------------ These COS FUV observations are a follow-up of three targets that were observed in Cycle 18/19 as part of a COS snapshot survey. We will use the same setup (G130M@1291A), but will use all four FP-POS positions to properly account for fixed pattern noise, and increase the total exposure time per target such that we achieve a S/N~30-40 across the entire wavelength range, i.e. in particular also in the wings of the Ly alpha absorption, where several weak, sharp metal absorption lines of interest are located. Real Time Justification ----------------------- 12869( 3) - 20-Jun-2012 21:06:53 - [ 2] Calibration Justification ------------------------- Additional Comments ------------------- Positions and proper motions for all three targets were taken from the PPMXL catalogue, and the Cycle 18/19 observations were successful without the use of an ACQ/SEARCH. We follow here the same strategy. ------------------------------------------------------------------------------------ 12869( 3) - 20-Jun-2012 21:06:53 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 WD0710+741 STAR, DA RA=07H17M9.7800S +/- 0.3", J2000 V = 14.97 +/- 0.1 DEC=+74D00'40.50" +/- 0.3" Reference Frame: ICRS Comments: White dwarf, Teff=19000 logg=7.50. This star has been observed on 2011-12-23 with the same setup (COS/G130M), see data set LBOVNP. The formal error on the position in 2012/13 based on the uncertainty in the historic position and proper motion is ~0.3". The COS observations were successfully acquired without a ACQ/SEARCH. This is also one of the STIS standard stars, and has been observed many times with the G140L / G230L. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.024154536124435307 -0.0862 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1013+256 STAR, DA RA=10H16M16.9500S +/- 0.3", J2000 V = 15.97 +/- 0.1 DEC=+25D24'56.80" +/- 0.3" Reference Frame: ICRS Comments: White dwarf, Teff=21990 logg=8.00. This star has been observed on 2011-04-24 with the same setup (COS/G130M), see data set LBIY9C. The formal error on the position in 2012/13 based on the uncertainty in the historic position and proper motion is ~0.3". The COS observations were successfully acquired without a ACQ/SEARCH. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.0023324033293178345 -0.0070999999999999995 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 3 WD1647+375 STAR, DA RA=16H49M20.2800S +/- 0.4", J2000 V = 15.00 +/- 0.1 DEC=+37D28'21.20" +/- 0.4" Reference Frame: ICRS Comments: White dwarf, Teff=21980 logg=7.89. This star has been observed on 2011-10-05 with the same setup (COS/G130M), see data set LBOVAA.The formal error on the position in 2012/13 based on the uncertainty in the historic position and proper motion is ~0.3". The COS observations were successfully acquired without a ACQ/SEARCH. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.0059052442726889795 -0.0056 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 12869( 3) - 20-Jun-2012 21:06:53 - [ 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 WD0710+741 COS/FUV ACQ/PEA PSA G130M 1291 1 1 S KXD ------------------------------------------------------------------------------------------------------------------------------------ 2 WD0710+741 COS/FUV ACQ/PEA PSA G130M 1291 STEP-SIZE=0.9, NUM-POS=5, 1 1 S KD CENTER=DEF ------------------------------------------------------------------------------------------------------------------------------------ 3 WD0710+741 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=400, FLASH=YES, 1 621 S G FP-POS=1 ------------------------------------------------------------------------------------------------------------------------------------ 4 WD0710+741 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=400, FLASH=YES, 1 621 S G FP-POS=2 ------------------------------------------------------------------------------------------------------------------------------------ 5 WD0710+741 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=400, FLASH=YES, 1 621 S G FP-POS=3 ------------------------------------------------------------------------------------------------------------------------------------ 6 WD0710+741 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=400, FLASH=YES, 1 622 S G FP-POS=4 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WD0710+741 1 COS/FUV ACQ/PEA PSA G130M 1291 none none none none 1 N/A KXD WD0710+741 2 COS/FUV ACQ/PEA PSA G130M 1291 none none none none 1 N/A KD WD0710+741 3 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G WD0710+741 4 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G WD0710+741 5 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G WD0710+741 6 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G 12869( 3) - 20-Jun-2012 21:06:53 - [ 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 WD1013+256 COS/NUV ACQ/IMA PSA MIRRORB 1 12 S GE ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1013+256 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=640, FLASH=YES, 1 2025 S G FP-POS=1 ------------------------------------------------------------------------------------------------------------------------------------ 3 WD1013+256 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=840, FLASH=YES, 1 396 S G FP-POS=2 ------------------------------------------------------------------------------------------------------------------------------------ 4 WD1013+256 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=735, FLASH=YES, 1 1628 S G FP-POS=2 ------------------------------------------------------------------------------------------------------------------------------------ 5 WD1013+256 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=840, FLASH=YES, 1 1224 S G FP-POS=3 ------------------------------------------------------------------------------------------------------------------------------------ 6 WD1013+256 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=660, FLASH=YES, 1 801 S G FP-POS=3 ------------------------------------------------------------------------------------------------------------------------------------ 7 WD1013+256 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=840, FLASH=YES, 1 2051 S G FP-POS=4 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WD1013+256 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE WD1013+256 2 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G WD1013+256 3 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G WD1013+256 4 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G WD1013+256 5 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G WD1013+256 6 COS/FUV TIME-TA PSA G130M 1291 none none none none 3 N/A G WD1013+256 7 COS/FUV TIME-TA PSA G130M 1291 none none none none 3 N/A G 12869( 3) - 20-Jun-2012 21:06:53 - [ 6] Visit: 03 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 WD1647+375 COS/FUV ACQ/PEA PSA G130M 1291 1 1 S KXD ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1647+375 COS/FUV ACQ/PEA PSA G130M 1291 STEP-SIZE=0.9, NUM-POS=5, 1 1 S KD CENTER=DEF ------------------------------------------------------------------------------------------------------------------------------------ 3 WD1647+375 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=222, FLASH=YES, 1 541 S G FP-POS=1 ------------------------------------------------------------------------------------------------------------------------------------ 4 WD1647+375 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=222, FLASH=YES, 1 541 S G FP-POS=2 ------------------------------------------------------------------------------------------------------------------------------------ 5 WD1647+375 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=222, FLASH=YES, 1 541 S G FP-POS=3 ------------------------------------------------------------------------------------------------------------------------------------ 6 WD1647+375 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=222, FLASH=YES, 1 541 S G FP-POS=4 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WD1647+375 1 COS/FUV ACQ/PEA PSA G130M 1291 none none none none 1 N/A KXD WD1647+375 2 COS/FUV ACQ/PEA PSA G130M 1291 none none none none 1 N/A KD WD1647+375 3 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G WD1647+375 4 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G WD1647+375 5 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G WD1647+375 6 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 N/A G 12869( 3) - 20-Jun-2012 21:06:53 - [ 7] Summary Form for Proposal 12869 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, ACQ/PEAKD, ACQ/PEAKXD, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=222, BUFFER-TIME=400, BUFFER-TIME=640, BUFFER-TIME=660, BUFFER-TIME=735, BUFFER-TIME=840, CENTER=DEF, FLASH=YES, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4, NUM-POS=5, STEP-SIZE=0.9 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names WD0710+741, WD1013+256, WD1647+375 ------------------------------------------------------------------------------------------------------------------------------------