14128( 2) - 06-Jul-2015 16:10:17 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14128 Version: 2 Check-in Time: 06-Jul-2015 16:10:17 STScI Edit Number: 0 Title The dawn of rocky planet formation ------------------------------------------------------------------------------------ Type Cycle GO 23 ------------------------------------------------------------------------------------ Investigators Contact? PI: Mr. Mark Hollands The University of Warwick Y CoI: Prof. Boris T. Gaensicke The University of Warwick N CoI: Prof. Detlev G. Koester Universitat Kiel N ------------------------------------------------------------------------------------ Abstract The vast majority of all known planet host stars will eventually evolve into white dwarfs. With the parameter space of the known planetary systems ever increasing, it is now clear that a significant fraction of these systems will survive this evolution (including the solar system from Mars outwards). Equally, many of the known white dwarfs were once planet hosts, and some of them very likely still host the remnants of planetary systems. In fact, we already know the signposts of such evolved planetary systems: metal-pollution of the otherwise pristine H/He atmosphere of a white dwarf by accretion of planetary debris. The identification of the coolest and hence oldest metal-polluted white dwarfs opens the exciting potential to investigate the history of rocky planet formation in the Galaxy. Using the Sloan Digital Sky Survey, we are now discovering large numbers of such systems: white dwarfs that have accreted rocky bodies of at least the mass of Ceres, the largest asteroid known in the solar system, and that already finished their main-sequence life when the Earth was just being formed. Precise measurements of the system ages, and accurate chemical abundances of the planetary debris require improved model atmospheres and input physics to deal with the extremely dense atmospheres of these cool white dwarfs, which we have computed. Because the strongest absorption features lie in the near-ultraviolet, we request HST STIS observations of three systems spanning the relevant range of temperatures to test and calibrate our calculations. With those calibrations in hand, we will then be able to analyse the full sample using only the available optical data. ------------------------------------------------------------------------------------ Observations Description ------------------------ The objective of these observations is to obtain NUV spectra of 3 cool metal-polluted white dwarfs covering different temperatures. This wavelength range is previously unobserved for objects of this type, and so line strengths in this region are not well known. Because the degree of absorption in this range leads to radiative backwarming of the optical spectra of these stars, our atmospheric models are currently not well calibratated, and so accuracy of calculated temperatures is model limited. The 3 objects cover a range of temperatures for these stars with the expected UV flux varying correspondingly. SDSS0956+5912 is the faintest object in the optical but has relatively bright UV flux as indicated by its GALEX NUV magnitude of 21.4. In contrast, SDSS1536+1247 is the brightest target in the 14128( 2) - 06-Jul-2015 16:10:17 - [ 2] optical (due to its proximity), but because it is much cooler, there is significant line blanketing in the UV and therefore has the lowest GALEX NUV magnitude of 22.4. Therefore, despite SDSS1536+1247 being the brightest object in the optical we require 4 orbits (rather than 2 for our other targets), to obtain the required signal-to-noise. The observations are fairly straightforward. Each target has one visit which starts with an acquistion. The target is then observed over thr required number of orbits with STIS-NUV, using the G230-L grating and 52x2 slit. ------------------------------------------------------------------------------------ 14128( 2) - 06-Jul-2015 16:10:17 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSS0956+591 STAR, DZ RA=09H56M45.1680S +/- 0.1", J2000 V = 18.4 +/- 0.05 GALEX_NUV = 21.4 2 DEC=+59D12'40.75" +/- 0.1" Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.015225126030799615 -0.04622 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 SDSS1038-003 STAR, DZ RA=10H38M9.1850S +/- 0.1", J2000 V = 17.0 +/- 0.05 6 DEC=-00D36'22.37" +/- 0.1" Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.006502363951678604 0.01751 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 3 SDSS1535+124 STAR, DZ RA=15H35M5.8080S +/- 0.1", J2000 V = 16.0 +/- 0.05 GALEX_NUV =22.4 7 DEC=+12D47'45.13" +/- 0.1" Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.01134850306798157 -0.1866 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 14128( 2) - 06-Jul-2015 16:10:17 - [ 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 SDSS0956+59 STIS/CCD ACQ 50CCD MIRROR 1 4 S (4 S) 12 Comments: We use the 50CCD filter for the acquisition instead of the default F28X50LP as there is a nearby, somewhat fainter, red object - just to be on the safe side that STIS will acquire the brighter / bluer white dwarf target. ------------------------------------------------------------------------------------------------------------------------------------ 2 SDSS0956+59 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=625 1 2503 S 12 -MAMA G (2503 S) Comments: Estimated total count rate (source + target) ~1600, to be a bit more conservative (e.g. higher than expected background level), we assumed twice that rate to calculate the BUFFER-TIME. ------------------------------------------------------------------------------------------------------------------------------------ 3 SDSS0956+59 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=625 1 3181 S 12 -MAMA G (3181 S) Comments: Estimated total count rate (source + target) ~1600, to be a bit more conservative (e.g. higher than expected background level), we assumed twice that rate to calculate the BUFFER-TIME. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SDSS0956+5912 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A SDSS0956+5912 2 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 1 N/A -MAMA G SDSS0956+5912 3 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 2 N/A -MAMA G 14128( 2) - 06-Jul-2015 16:10:17 - [ 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 SDSS1038-00 STIS/CCD ACQ 50CCD MIRROR 1 2 S (2 S) 36 ------------------------------------------------------------------------------------------------------------------------------------ 2 SDSS1038-00 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=625 1 2265 S 36 -MAMA G (2265 S) Comments: Estimated total count rate (source + target) ~1600, to be a bit more conservative (e.g. higher than expected background level), we assumed twice that rate to calculate the BUFFER-TIME. ------------------------------------------------------------------------------------------------------------------------------------ 3 SDSS1038-00 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=625 1 2960 S 36 -MAMA G (2960 S) Comments: Estimated total count rate (source + target) ~1600, to be a bit more conservative (e.g. higher than expected background level), we assumed twice that rate to calculate the BUFFER-TIME. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SDSS1038-0036 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A SDSS1038-0036 2 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 1 N/A -MAMA G SDSS1038-0036 3 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 2 N/A -MAMA G 14128( 2) - 06-Jul-2015 16:10:17 - [ 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSS1535+12 STIS/CCD ACQ 50CCD MIRROR 1 1 S (1 S) 47 ------------------------------------------------------------------------------------------------------------------------------------ 2 SDSS1535+12 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=625 1 2277 S 47 -MAMA G (2277 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SDSS1535+12 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=625 1 2968 S 47 -MAMA G (2968 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SDSS1535+12 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=625 1 2943 S 47 -MAMA G (2943 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 SDSS1535+12 STIS/NUV TIME-TA 52X2 G230L 2376 BUFFER-TIME=625 1 2943 S 47 -MAMA G (2943 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 | ------------------------------------------------------------------------------------------------------------------------------------ SDSS1535+1247 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A SDSS1535+1247 2 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 1 N/A -MAMA G SDSS1535+1247 3 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 2 N/A -MAMA G SDSS1535+1247 4 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 3 N/A -MAMA G SDSS1535+1247 5 STIS/NUV TIME-TA 52X2 G230L 2376 none none none none 4 N/A -MAMA G 14128( 2) - 06-Jul-2015 16:10:17 - [ 7] Summary Form for Proposal 14128 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 50CCD, 52X2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=625 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G230L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names SDSS0956+5912, SDSS1038-0036, SDSS1535+1247 ------------------------------------------------------------------------------------------------------------------------------------