14082( 4) - 05-Apr-2016 14:26:39 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14082 Version: 4 Check-in Time: 05-Apr-2016 14:26:39 STScI Edit Number: 0 Title Connecting white dwarf rotation and debris accretion ------------------------------------------------------------------------------------ Type Cycle GO 23 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Dan Maoz Tel Aviv University - Wise Observatory Y CoI: Dr. Eric Agol University of Washington N CoI: Dr. Jay Farihi University College London N CoI: Prof. Boris T. Gaensicke The University of Warwick N CoI: Ms. Na'ama Hallakoun Tel Aviv University - Wise Observatory N CoI: Dr. Mukremin Kilic University of Oklahoma Norman Campus N CoI: Dr. Abraham Loeb Harvard University N CoI: Prof. Tsevi Mazeh Tel Aviv University - Wise Observatory N CoI: Dr. Fergal Mullally NASA Ames Research Center N ------------------------------------------------------------------------------------ Abstract Recent Kepler photometry has revealed that half of white dwarfs have periodic, low-level (~10^-3-10^-4), optical variations. HST UV spectroscopy has shown that half of white dwarfs are actively accreting rocky planetary debris. By obtaining UV spectra of 9 WDs monitored with Kepler, we will test the hypothesis that these two phenomena are causally connected, i.e. that the optical periodic modulation is caused by WD rotation coupled with an inhomogeneous surface distribution of accreted metals. If there is a match between the periodically variable WDs and the WDs with UV line opacity, this will confirm the hypothesis. The Kepler photometric modulation will then be established as the first method that can provide reliable rotation periods for hundreds of normal WDs. WD rotation is a critical observable for understanding stellar evolution, stellar mass loss, Type-Ia supernova progenitors and more, but rotation periods have been measured for only tens of WDs, mainly rare magnetic ones. Furthermore, confirmation of the connection between UV line opacity and optical modulation will provide an inexpensive photometric probe for identifying accretion of rocky debris in large samples of WDs, and mapping its dependence on WD (and progenitor system) properties. If the hypothesis is rejected (there is no match between UV line opacity and optical modulation), this will point to alternative and no-less-interesting explanations for the optical variability, e.g. the abundant presence of close-in companions to WDs, such as giant planets or secondary cool WDs. ------------------------------------------------------------------------------------ Observations Description ------------------------ Sample Selection: To test the correspondence between the existence of periodic optical variability and the presence of UV metal absorption lines in WDs, we will observe 9 WDs that have been monitored for low-level variability with good S/N: four WDs that have clear periodic modulation, and five that do not, with upper limits on any periodic variability at amplitude levels below 100 ppm (i.e. 10^-4 ). Additional selection criteria for all 9 WDs are: visual magnitude < 18 mag, to ensure sufficient S/N; effective temperatures T eff < 32000K, to avoid WDs in which radiative levitation plays a role in the presence 14082( 4) - 05-Apr-2016 14:26:39 - [ 2] of atmospheric metals; surface gravity 7.5 < log g < 8.5, to include only bona-fide normal WDs of the kind whose UV metal pollution has been studied. The choice of 9 WDs will permit, in principle, to significantly reject the null hypothesis that optical modulations and UV metal pollution are unrelated. Assuming that in two of the nine WDs there could be a mismatch between the presence of optical modulation and UV metal lines, due to a different cause for the modulation (e.g. rotation plus magnetic dichroism, or beaming due to a close companion), this would still leave seven WDs with a match between the two effects. Since the probability of any WD to display each effect alone is ~50% (Koester et al., 2014; Maoz et al., 2015), the chance probability for seven matches would be 2^-7 < 1%, and thus seven or more matches will firmly reject the null hypothesis. Observations: Each WD will be observed for one orbit with COS/FUV, except for the three faint WDs with no FUV magnitude measurements, which will be observed for two orbits, in order to achieve higher S/N, as two WDs of our sample were already observed/scheduled for observation by COS. For acquisition we will generally use the COS/NUV ACQ/IMAGE mode with MirrorB. For two of the targets, which are too bright to be acquired with ACQ/IMAGE, we will use instead COS/FUV with ACQ/PEAKXD and ACQ/PEAKD modes. Science exposures will be taken using the TIME-TAG mode by the G130M grating of COS/FUV with a central wavelength of 1291A, which will cover the wavelength range 1130-1435A. We will dither the exposures over the four FP-POS settings in order to remove fixed pattern noise. We will fill each orbit with a net exposure time of ~35 min, to get a S/N ~ 10 per resolution element, more than adequate for detecting and measuring the UV metal lines. ------------------------------------------------------------------------------------ 14082( 4) - 05-Apr-2016 14:26:39 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 WD1949+4734 STAR, DA RA=19H49M14.5790S +/- 0.4", J2000 V = 16.2 +/- 0.1 DEC=+47D34'45.98" +/- 0.4" Reference Frame: ICRS Extended: NO Comments: A<50 ppm, T=16kK, DA E(B-V)=0.111 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.0018678639105149113 -0.0167 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1909+4717 STAR, DA RA=19H09M59.3470S +/- 0.4", J2000 V = 16.4 +/- 0.1 GALEX FUV=16.5AB DEC=+47D17'10.00" +/- 0.4" Reference Frame: ICRS Extended: NO Comments: A<70 ppm, T=14kK, DA E(B-V)=0.058 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0013955682096524476 -0.054799999999999995 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 3 WD1927+4219 STAR, DB RA=19H26M46.0110S +/- 0.4", J2000 V = 18.2 +/- 0.1 GALEX FUV=16.7AB, DEC=+42D19'35.32" +/- 0.4" GALEX NUV=16.8AB Reference Frame: ICRS Extended: NO Comments: P=0.6 d, A=500 ppm, T~34kK, DB E(B-V)=0.112 Temperature according to SED Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -4.598820534633434E-4 -0.0027 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 4 WD1855+4207 STAR, DA RA=18H55M46.0330S +/- 0.4", J2000 V = 17.9 +/- 0.1 GALEX FUV=16.2AB DEC=+42D07'4.43" +/- 0.4" Reference Frame: ICRS Extended: NO Comments: P=0.37d, A=800 ppm, T=30.5kK DA E(B-V)=0.081 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -8.98755563276217E-6 -0.0046 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 5 WD1857+4909 STAR, DA RA=18H57M47.1310S +/- 0.4", J2000 V = 16.1 +/- 0.1 GALEX FUV=15.2AB DEC=+49D09'39.25" +/- 0.4" Reference Frame: ICRS Extended: NO Comments: P=0.09 d, A=300 ppm, T=23kK, DA E(B-V)=0.043 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.001101023482116277 0.0689 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 14082( 4) - 05-Apr-2016 14:26:39 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 6 WD1919+3958 STAR, DA RA=19H19M27.6850S +/- 0.4", J2000 V = 15.8 +/- 0.1 DEC=+39D58'39.71" +/- 0.4" Reference Frame: ICRS Extended: NO Comments: A<50 ppm. T=19kK, DA E(B-V)=0.1118 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0010613846672980457 0.044899999999999995 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 7 WD1940+4240 STAR, DA RA=19H40M59.3670S +/- 0.4", J2000 V = 16.6 +/- 0.1 DEC=+42D40'31.30" +/- 0.4" Reference Frame: ICRS Extended: NO Comments: A<80 ppm, T=24kK, DA+DA E(B-V) = 0.1513 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.0036815070773464917 -0.0575 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 14082( 4) - 05-Apr-2016 14:26:39 - [ 5] 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 WD1949+4734 COS/NUV ACQ/IMA PSA MIRRORB 1 34.2 S GE (34.2 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1949+4734 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=3519, FP-POS=ALL 1 3000 S G see below (5437 S) Comments: Exposure time (seconds) = 5, 437.0000 at wavelength 1310.00A gives: SNR = 10.7515 (per resolution element) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WD1949+4734 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE WD1949+4734 2 COS/FUV TIME-TA PSA G130M 1291 none none none 1 1 1252.0 S G WD1949+4734 2 COS/FUV TIME-TA PSA G130M 1291 none none none 2 1 1253.0 S G WD1949+4734 2 COS/FUV TIME-TA PSA G130M 1291 none none none 3 2 1466.0 S G WD1949+4734 2 COS/FUV TIME-TA PSA G130M 1291 none none none 4 2 1466.0 S G 14082( 4) - 05-Apr-2016 14:26:39 - [ 6] 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 WD1909+4717 COS/NUV ACQ/IMA PSA MIRRORB 1 45 S (45 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1909+4717 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=2753, FP-POS=ALL 1 3000 S G see below (2275 S) Comments: Exposure time (seconds) = 2, 275.0000 at wavelength 1310.00A gives: SNR = 10.4222 (per resolution element) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WD1909+4717 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE WD1909+4717 2 COS/FUV TIME-TA PSA G130M 1291 none none none 1 1 568.0 S G WD1909+4717 2 COS/FUV TIME-TA PSA G130M 1291 none none none 2 1 568.0 S G WD1909+4717 2 COS/FUV TIME-TA PSA G130M 1291 none none none 3 1 568.0 S G WD1909+4717 2 COS/FUV TIME-TA PSA G130M 1291 none none none 4 1 571.0 S G 14082( 4) - 05-Apr-2016 14:26:39 - [ 7] 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 WD1927+4219 COS/NUV ACQ/IMA PSA MIRRORB 1 32.2 S GE (32.2 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1927+4219 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=2207, FP-POS=ALL 1 3000 S G see below (2227 S) Comments: Exposure time (seconds) = 2, 227.0000 at wavelength 1310.00A gives: SNR = 12.6901 (per resolution element) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WD1927+4219 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE WD1927+4219 2 COS/FUV TIME-TA PSA G130M 1291 none none none 1 1 556.0 S G WD1927+4219 2 COS/FUV TIME-TA PSA G130M 1291 none none none 2 1 556.0 S G WD1927+4219 2 COS/FUV TIME-TA PSA G130M 1291 none none none 3 1 557.0 S G WD1927+4219 2 COS/FUV TIME-TA PSA G130M 1291 none none none 4 1 558.0 S G 14082( 4) - 05-Apr-2016 14:26:39 - [ 8] Visit: 04 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 WD1855+4207 COS/NUV ACQ/IMA PSA MIRRORB 1 50.3 S GE (50.3 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1855+4207 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=2604, FP-POS=ALL 1 3000 S G see below (2218 S) Comments: Exposure time (seconds) = 2, 218.0000 at wavelength 1310.00A gives: SNR = 15.9079 (per resolution element) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WD1855+4207 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE WD1855+4207 2 COS/FUV TIME-TA PSA G130M 1291 none none none 1 1 554 S G WD1855+4207 2 COS/FUV TIME-TA PSA G130M 1291 none none none 2 1 554 S G WD1855+4207 2 COS/FUV TIME-TA PSA G130M 1291 none none none 3 1 555.0 S G WD1855+4207 2 COS/FUV TIME-TA PSA G130M 1291 none none none 4 1 555.0 S G 14082( 4) - 05-Apr-2016 14:26:39 - [ 9] Visit: 05 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 WD1857+4909 COS/NUV ACQ/IMA PSA MIRRORB 1 11.8 S GE (11.8 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1857+4909 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=1420, FP-POS=ALL 1 3000 S G see below (2284 S) Comments: Exposure time (seconds) = 2, 284.0000 at wavelength 1310.00A gives: SNR = 24.2557 (per resolution element) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WD1857+4909 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE WD1857+4909 2 COS/FUV TIME-TA PSA G130M 1291 none none none 1 1 571 S G WD1857+4909 2 COS/FUV TIME-TA PSA G130M 1291 none none none 2 1 571 S G WD1857+4909 2 COS/FUV TIME-TA PSA G130M 1291 none none none 3 1 571 S G WD1857+4909 2 COS/FUV TIME-TA PSA G130M 1291 none none none 4 1 571 S G 14082( 4) - 05-Apr-2016 14:26:39 - [ 10] Visit: 06 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 WD1919+3958 COS/NUV ACQ/IMA PSA MIRRORB 1 16.8 S GE (16.8 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1919+3958 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=2382, FP-POS=ALL 1 3000 S G see below (5275 S) Comments: Exposure time (seconds) = 5, 275.0000 at wavelength 1310.00A gives: SNR = 18.7255 (per resolution element) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WD1919+3958 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE WD1919+3958 2 COS/FUV TIME-TA PSA G130M 1291 none none none 1 1 1223.0 S G WD1919+3958 2 COS/FUV TIME-TA PSA G130M 1291 none none none 2 1 1224.0 S G WD1919+3958 2 COS/FUV TIME-TA PSA G130M 1291 none none none 3 2 1414.0 S G WD1919+3958 2 COS/FUV TIME-TA PSA G130M 1291 none none none 4 2 1414.0 S G 14082( 4) - 05-Apr-2016 14:26:39 - [ 11] Visit: 07 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 WD1940+4240 COS/NUV ACQ/IMA PSA MIRRORB 1 28.3 S GE (28.3 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1940+4240 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=2569, FP-POS=ALL 1 3000 S G see below (5332 S) Comments: Exposure time (seconds) = 5, 332.0000 at wavelength 1310.00A gives: SNR = 17.2929 (per resolution element) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ WD1940+4240 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE WD1940+4240 2 COS/FUV TIME-TA PSA G130M 1291 none none none 1 1 1232.0 S G WD1940+4240 2 COS/FUV TIME-TA PSA G130M 1291 none none none 2 1 1232.0 S G WD1940+4240 2 COS/FUV TIME-TA PSA G130M 1291 none none none 3 2 1434.0 S G WD1940+4240 2 COS/FUV TIME-TA PSA G130M 1291 none none none 4 2 1434.0 S G 14082( 4) - 05-Apr-2016 14:26:39 - [ 12] Summary Form for Proposal 14082 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1420, BUFFER-TIME=2207, BUFFER-TIME=2382, BUFFER-TIME=2569, BUFFER-TIME=2604, BUFFER-TIME=2753, BUFFER-TIME=3519, FP-POS=ALL ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names WD1855+4207, WD1857+4909, WD1909+4717, WD1919+3958, WD1927+4219, WD1940+4240, WD1949+4734 ------------------------------------------------------------------------------------------------------------------------------------