13807( 6) - 03-Feb-2015 14:00:19 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13807 Version: 6 Check-in Time: 03-Feb-2015 14:00:19 STScI Edit Number: 4 Title Unprecedented Tracking of the Unique Dwarf Nova GW Lib from Largest Amplitude Outburst to Quiescent Pulsations ------------------------------------------------------------------------------------ Type Cycle GO 22 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Paula Szkody University of Washington Y CoI: Prof. Edward M. Sion Villanova University N CoI: Dr. Anjum Mukadam University of Washington N CoI: Dr. Dean Townsley University of Alabama N CoI: Prof. Boris T. Gaensicke The University of Warwick N CoI: Dr. Denis J. Sullivan Victoria University of Wellington N CoI: Dr. Matthew Templeton American Association Of Variable Star N Observers ------------------------------------------------------------------------------------ Abstract The unique dwarf nova GW Lib, the prototype of cataclysmic variables containing white dwarfs that exhibit non-radial pulsations at quiescence, underwent the largest known amplitude outburst from an accretion disk instability (9 mag) in 2007. This huge outburst provided an unprecedented opportunity to probe how the interior white dwarf structure reacts to the accretion of mass and angular momentum by using its pulsation spectrum. As the outer envelope cools, the pulsation spectrum evolves, and we obtain the first opportunity to track how a white dwarf evolves through the instability strip on a timescale of just years.We have monitored GW Lib since its outburst with ground and COS observations. For the first 4 years after outburst, GW Lib followed a normal cooling pattern, with a different pulsation period than at quiescence becoming visible by year 3. However, rather than continuing to cool to its quiescent temperature, our latest 2013 COS observation showed a hotter temperature than in 2011, as well as a variable flux, temperature and pulsation amplitude during the HST orbits. As no previous dwarf nova has been followed for more than 3 years after outburst, and it is now obvious that the white dwarf in GW Lib does not cool monotonically, we propose to continue the cooling curve with a COS measurement in 2015. The cooling can only be constrained by an UV spectrum with HST (the optical spectrum is too contaminated by the accretion disk to determine a valid temperature) and the ratio of the UV to optical pulsation amplitude is needed to provide the mode index, essential for modeling the structure of the underlying white dwarf. ------------------------------------------------------------------------------------ Observations Description ------------------------ We have 2 goals in mind for these observations. One is to obtain a summed UV spectrum with sufficient S/N (>10) to allow a temperature determination of the underlying white dwarf by fitting the spectrum to white dwarf models. The second is to obtain time-resolved light curves by summing the background-subtracted TIME-TAG fluxes over several wavelength bands in 3sec intervals to detect and constrain the UV pulsations. From our past observations, we know 13807( 6) - 03-Feb-2015 14:00:19 - [ 2] that both goals can be accomplished by using the COS FUV with the G140 L grating which provides good coverage from 1100-2000A. The orbital period of GW Lib is very short (77 min) and the inclination is low (11 deg) so there is a good view of the white dwarf throughout the GW Lib orbit. Three HST orbits will provide a good spectrum as well as a light curve that will reveal pulsations down to a few percent, and allow further study of the relation between temperature and pulsation changes as observed in 2013. We will continue our ground observing programs on GW Lib to: 1) monitor the pulsation spectrum changes prior to the HST observations, 2) provide confirmation that the objects are close to quiescence at the time of the HST observation (the outburst recurrence time for GW Lib is about 25 yrs and 3) determine the amplitude of the optical pulse for comparison with that from the UV (the UV/optical amplitude ratio allows the mode determination). While the outburst timescale for GW Lib is on the order of 25 years, with the last outburst in 2007, HST still requires ground monitoring prior to the HST observations to ensure that it remains at quiescence. To accomplish this (using the AAVSO worldwide network as we have done for our past observations), as well as obtaining near-simultaneous data to compute our UV/opt pulsation amplitude ratio, we need the HST observation scheduled during months when GW Lib can be observed from the ground (Mar to June 2015). The best months would be April or May. ------------------------------------------------------------------------------------ 13807( 6) - 03-Feb-2015 14:00:19 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GW-LIB STAR, DWARF NOVA, RA=15H19M55.3400S +/- 0.1", J2000 V = 16.5 +/- 0.5 PULSATING VARIABLE DEC=-25D00'24.58" +/- 0.1" Reference Frame: ICRS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 -0.004685938653419062 0.0165 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 GW-LIB-SAFE- UNIDENTIFIED, BLANK RA-OFF=0S, DEC-OFF=9.75", FROM 1 J2000 V = 16.5 +/- 0.5 OFFSET FIELD Comments: This target is a blank piece of sky which is the bright object safe offset for GW-LIB. ------------------------------------------------------------------------------------------------------------------------------------ 13807( 6) - 03-Feb-2015 14:00:19 - [ 4] Visit: 01 Visit Requirements: SCHED 100%; ORIENT 200D TO 80 D; AFTER 02 BY 3 D TO 5 D; BETWEEN 22-APR-2015 AND 23-APR-2015; Period 1 D AND ZERO-PHASE HJD2457083.417 On Hold Comments: Additional Comments: This should be scheduled in during the evening - Baltimore time. Flags need to be cleared during the work day. The PHASE requirement will enforce this. 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 GW-LIB COS/FUV ACQ/PEA PSA G140L 1105 1 20 S (20 PHASE 0 TO 0.5; USE KXD S) OFFSET 01SAFE ------------------------------------------------------------------------------------------------------------------------------------ 2 GW-LIB COS/FUV ACQ/PEA PSA G140L 1105 STEP-SIZE=0.9, NUM-POS=5, 1 20 S (20 USE OFFSET 01SAFE KD CENTER=DEF S) ------------------------------------------------------------------------------------------------------------------------------------ 3 GW-LIB COS/FUV TIME-TA PSA G140L 1105 BUFFER-TIME=2168, FLASH=YES, 1 2168 S USE OFFSET 01SAFE G FP-POS=1 (2168 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 GW-LIB COS/FUV TIME-TA PSA G140L 1105 BUFFER-TIME=1708, FP-POS=2, 1 1708 S USE OFFSET 01SAFE G FLASH=YES (1708 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 GW-LIB COS/FUV TIME-TA PSA G140L 1105 BUFFER-TIME=824, FP-POS=3, 1 824 S (824 USE OFFSET 01SAFE G FLASH=YES S) ------------------------------------------------------------------------------------------------------------------------------------ 6 GW-LIB COS/FUV TIME-TA PSA G140L 1105 BUFFER-TIME=804, FP-POS=3, 1 804 S (804 USE OFFSET 01SAFE G FLASH=YES S) ------------------------------------------------------------------------------------------------------------------------------------ 7 GW-LIB COS/FUV TIME-TA PSA G140L 1105 BUFFER-TIME=1728, FP-POS=4, 1 1728 S USE OFFSET 01SAFE G FLASH=YES (1728 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 | ------------------------------------------------------------------------------------------------------------------------------------ GW-LIB 1 COS/FUV ACQ/PEA PSA G140L 1105 none none none none 1 N/A KXD GW-LIB 2 COS/FUV ACQ/PEA PSA G140L 1105 none none none none 1 N/A KD GW-LIB 3 COS/FUV TIME-TA PSA G140L 1105 none none none none 1 N/A G GW-LIB 4 COS/FUV TIME-TA PSA G140L 1105 none none none none 2 N/A G GW-LIB 5 COS/FUV TIME-TA PSA G140L 1105 none none none none 2 N/A G GW-LIB 6 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 N/A G 13807( 6) - 03-Feb-2015 14:00:19 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ GW-LIB 7 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 N/A G 13807( 6) - 03-Feb-2015 14:00:19 - [ 6] Visit: 02 Visit Requirements: ORIENT 200D TO 80 D; Period 7 D AND ZERO-PHASE HJD2457082.5 On Hold Comments: Additional Comments: This visit allocates and sets up the safe position offset slot for visit 01 which will use that slot. This S/C visit should go earlier in the week while visit 01 will be at least 3 days later. The PHASE requirement will ensure that the visit is sheduled on a Sunday. 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 GW-LIB S/C POINTIN V1 1 5 S (5 S) POS TARG 235.158, G -235.01; PHASE 0 TO 0.143; SAVE OFFSET 01SAFE; SPEC COM INSTR ECSLOTSET; QESIPARM ANGLE 0; QESIPARM DIST 9.75 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ GW-LIB 1 S/C POINTIN V1 none none none none tbd N/A G 13807( 6) - 03-Feb-2015 14:00:19 - [ 7] Visit: 03 Visit Requirements: SCHED 100%; ORIENT 200D TO 80 D; BETWEEN 01-MAR-2015:00:00:00 AND 30-JUN-2015:00:00:00 On Hold Comments: Additional Comments: This visit is for BOP checking the safe target only and should not execute onboard HST. 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 GW-LIB-SAFE COS/FUV ACQ/PEA PSA G140L 1105 1 20 S (20 -OFFSET KXD S) ------------------------------------------------------------------------------------------------------------------------------------ 2 GW-LIB-SAFE COS/FUV ACQ/PEA PSA G140L 1105 STEP-SIZE=0.9, NUM-POS=5, 1 20 S (20 -OFFSET KD CENTER=DEF S) ------------------------------------------------------------------------------------------------------------------------------------ 3 GW-LIB-SAFE COS/FUV TIME-TA PSA G140L 1105 BUFFER-TIME=2168, FLASH=YES, 1 2168 S -OFFSET G FP-POS=1 (2168 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 GW-LIB-SAFE COS/FUV TIME-TA PSA G140L 1105 BUFFER-TIME=1708, FP-POS=2, 1 1708 S -OFFSET G FLASH=YES (1708 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 GW-LIB-SAFE COS/FUV TIME-TA PSA G140L 1105 BUFFER-TIME=824, FP-POS=3, 1 824 S (824 -OFFSET G FLASH=YES S) ------------------------------------------------------------------------------------------------------------------------------------ 6 GW-LIB-SAFE COS/FUV TIME-TA PSA G140L 1105 BUFFER-TIME=804, FP-POS=3, 1 804 S (804 -OFFSET G FLASH=YES S) ------------------------------------------------------------------------------------------------------------------------------------ 7 GW-LIB-SAFE COS/FUV TIME-TA PSA G140L 1105 BUFFER-TIME=1728, FP-POS=4, 1 1728 S -OFFSET G FLASH=YES (1728 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 | ------------------------------------------------------------------------------------------------------------------------------------ GW-LIB-SAFE-OFFSET 1 COS/FUV ACQ/PEA PSA G140L 1105 none none none none 1 N/A KXD GW-LIB-SAFE-OFFSET 2 COS/FUV ACQ/PEA PSA G140L 1105 none none none none 1 N/A KD GW-LIB-SAFE-OFFSET 3 COS/FUV TIME-TA PSA G140L 1105 none none none none 1 N/A G GW-LIB-SAFE-OFFSET 4 COS/FUV TIME-TA PSA G140L 1105 none none none none 2 N/A G GW-LIB-SAFE-OFFSET 5 COS/FUV TIME-TA PSA G140L 1105 none none none none 2 N/A G GW-LIB-SAFE-OFFSET 6 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 N/A G GW-LIB-SAFE-OFFSET 7 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 N/A G 13807( 6) - 03-Feb-2015 14:00:19 - [ 8] Summary Form for Proposal 13807 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA, V1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, S/C ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAKD, ACQ/PEAKXD, POINTING, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1708, BUFFER-TIME=1728, BUFFER-TIME=2168, BUFFER-TIME=804, BUFFER-TIME=824, CENTER=DEF, FLASH=YES, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4, NUM-POS=5, STEP-SIZE=0.9 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 02 BY 3 D TO 5 D, BETWEEN 01-MAR-2015:00:00:00 AND 30-JUN-2015:00:00:00, BETWEEN 22-APR-2015 AND 23-APR-2015, ORIENT 200D TO 80 D, PHASE 0 TO 0.143, PHASE 0 TO 0.5, POS TARG 235.158, -235.01, Period 1 D AND ZERO-PHASE HJD2457083.417, Period 7 D AND ZERO-PHASE HJD2457082.5, QESIPARM ANGLE 0, QESIPARM DIST 9.75, SAVE OFFSET 01SAFE, SCHED 100%, SPEC COM INSTR ECSLOTSET, USE OFFSET 01SAFE ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names GW-LIB, GW-LIB-SAFE-OFFSET ------------------------------------------------------------------------------------------------------------------------------------