16046( 5) - 11-Feb-2020 21:12:48 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16046 Version: 5 Check-in Time: 11-Feb-2020 21:12:48 STScI Edit Number: 2 Title Understanding the Instability Strip of Accreting Pulsating White Dwarfs: Followup to a Recent COS Result ------------------------------------------------------------------------------------ Type Cycle GO 27 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Paula Szkody University of Washington Y CoI: Prof. Boris T. Gaensicke The University of Warwick N CoI: Dr. Patrick Godon Villanova University N CoI: Prof. Edward M. Sion Villanova University N CoI: Dr. Stella Kafka American Association Of Variable Star N Observers CoI: Dr. Odette Fabiola Toloza The University of Warwick N Castillo CoI: Dr. Keaton Bell University of Texas at Austin N ------------------------------------------------------------------------------------ Abstract Analysis of August, 2019 COS time-tag ultraviolet spectra shows great promise for confirmation of the physical properties defining the observed wide instability strip for pulsating white dwarfs in close binaries accreting material from their companions. The dwarf nova V386 Ser containing a pulsating white dwarf underwent its first rare large amplitude outburst in January 2019. The August UV spectra 7 months after this outburst implies a large He abundance from a white dwarf ~5000K hotter than at quiescence, with a pulsation period 6 times shorter than its quiescent one. Both the temperature and period fit with a mode driven by a He enriched composition, exactly what is predicted as the cause of the wide instability strip. For the first time, the observations match theoretical predictions! We propose to monitor the cooling during the next 6 months to further constrain the HeII and H/HeI convection zones in pulsating white dwarfs. This information is unique to the few white dwarf pulsators that undergo dwarf nova outbursts, as their heating and cooling only takes months-few years (versus millions of years in single white dwarf pulsators), presenting a rare opportunity to track how a deepening convection zone begins to drive pulsation modes with longer periods. Unfortunately, the January outburst missed the normal Cycle 26 deadline and the August observation (a Cycle 26 mid proposal) took place too late for results to provide a strong case for the Cycle 27 deadline. Due to the decades long recurrence time between outbursts in dwarf novae with pulsating white dwarfs, this is likely the last object HST can follow from outburst to quiescence. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will use COS with the G140L grating (setting 800) in time-tag mode for 3 consecutive HST orbits. This same configuration was used for the 2 orbits in our August 2019 observation which provided a useful spectrum with coverage between 900-1900A and detection of 3% amplitude pulsations. The AAVSO shows the system is currently at 18.5 magnitude, about one-half magnitude above quiescence and a 16046( 5) - 11-Feb-2020 21:12:48 - [ 2] half-magnitude fainter than the previous Aug observation. The 3 orbits will provide an adequate spectrum for determining the temperature which is expected to be somewhat cooler than the 20, 000K determined in August. To maximize the determination of pulsations, the orbits should be consecutive. To maximize the cooling rate, the observations should be conducted as soon as possible within the window when the object is observable from the ground (Feb-March). Target acquisition will be done using the ACQ/IMAGE in the NUV. This is the first outburst since the discovery 19 years ago, meaning the outburst recurrence time is several decades. However, we will determine the precise quiescent magnitude within 24 hrs of the HST observation as done in the past. While the science is optimized if the observations take place as soon as possible (before the object cools to its quiescent temperature), if reduced gyros impact the observation windows, the observations can be made up to August 2020 when it will no longer be visible from the ground. ------------------------------------------------------------------------------------ 16046( 5) - 11-Feb-2020 21:12:48 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 V-V386-SER STAR, DWARF NOVA, RA=16H10M33.6206S +/- 0.0002", J2000 V = 18.5 +/- 0.5 INTERACTING BINARY, DEC=-01D02'23.51" +/- 0.0002" PULSATING VARIABLE Reference Frame: ICRS Extended: NO Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2015.5 -5.34554702006616E-4 -0.01910200003294449 0.00415 ------------------------------------------------------------------------------------------------------------------------------------ 2 TARGET01-SAF UNIDENTIFIED, BLANK RA-OFF=-0.64S, DEC-OFF=1.678", J2000 V = 18.5 +/- 0.5 E-TARGET FIELD FROM 1 Extended: NO Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Ths target is a blank piece of sky which is the bright object safe pointing and is 9.794 arcseconds away at a PA 279.9 degrees from V-V386-SER. ------------------------------------------------------------------------------------------------------------------------------------ 16046( 5) - 11-Feb-2020 21:12:48 - [ 4] Visit: 01 Visit Requirements: ORIENT 115D TO 355 D; AFTER 1A BY 3 D TO 5 D On Hold Comments: Additional Comments: This should be scheduled in evening-local time. Flags need to be cleared during the work day. 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 V-V386-SER COS/NUV ACQ/IMA PSA MIRRORB 1 50 S (50 USE OFFSET V1ASAF GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 V-V386-SER COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=1730, FP-POS=1, 1 1841 S USE OFFSET V1ASAF G FLASH=YES (1841 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 V-V386-SER COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=200, FP-POS=2, 1 310 S (310 USE OFFSET V1ASAF G FLASH=YES S) ------------------------------------------------------------------------------------------------------------------------------------ 4 V-V386-SER COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=1430, FP-POS=2, 1 1541 S USE OFFSET V1ASAF G FLASH=YES (1541 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 V-V386-SER COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=970, FP-POS=3, 1 1080 S USE OFFSET V1ASAF G FLASH=YES (1080 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 V-V386-SER COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=660, FP-POS=3, 1 771 S (771 USE OFFSET V1ASAF G FLASH=YES S) ------------------------------------------------------------------------------------------------------------------------------------ 7 V-V386-SER COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=1730, FP-POS=4, 1 1840 S USE OFFSET V1ASAF G FLASH=YES (1840 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 | ------------------------------------------------------------------------------------------------------------------------------------ V-V386-SER 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE V-V386-SER 2 COS/FUV TIME-TA PSA G140L 800 none none none none 1 N/A G V-V386-SER 3 COS/FUV TIME-TA PSA G140L 800 none none none none 1 N/A G V-V386-SER 4 COS/FUV TIME-TA PSA G140L 800 none none none none 2 N/A G V-V386-SER 5 COS/FUV TIME-TA PSA G140L 800 none none none none 2 N/A G V-V386-SER 6 COS/FUV TIME-TA PSA G140L 800 none none none none 3 N/A G V-V386-SER 7 COS/FUV TIME-TA PSA G140L 800 none none none none 3 N/A G 16046( 5) - 11-Feb-2020 21:12:48 - [ 5] Visit: 1A Visit Requirements: ORIENT 115D TO 355 D On Hold Comments: Additional Comments: This visit allocates and set 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 atleast 3 days later. The S/C visit will contain only 1 exposure. Note: weekends are to be avoided since the CS must clear the target within 24 hours of HST execution. 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 V-V386-SER S/C DATA V1 1 5 S (5 S) POS TARG 232.723, -237.515; SAVE OFFSET V1ASAF; SPEC COM INSTR ECSLOTSET; QESIPARM ANGLE 279.9; QESIPARM DIST 9.794 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V-V386-SER 1 S/C DATA V1 none none none none 1 N/A 16046( 5) - 11-Feb-2020 21:12:48 - [ 6] Visit: 1B (SCIENCETARGET-BOP-ONLY) Visit Requirements: ORIENT 115D TO 355 D On Hold Comments: Additional Comments: This visit is for BOP checking the safetarget 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 TARGET01-SA COS/NUV ACQ/IMA PSA MIRRORB 1 50 S (50 FE-TARGET GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 TARGET01-SA COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=1730, FP-POS=1, 1 1841 S FE-TARGET G FLASH=YES (1841 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 TARGET01-SA COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=200, FP-POS=2, 1 310 S (310 FE-TARGET G FLASH=YES S) ------------------------------------------------------------------------------------------------------------------------------------ 4 TARGET01-SA COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=1430, FP-POS=2, 1 1541 S FE-TARGET G FLASH=YES (1541 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 TARGET01-SA COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=970, FP-POS=3, 1 1080 S FE-TARGET G FLASH=YES (1080 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 TARGET01-SA COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=660, FP-POS=3, 1 771 S (771 FE-TARGET G FLASH=YES S) ------------------------------------------------------------------------------------------------------------------------------------ 7 TARGET01-SA COS/FUV TIME-TA PSA G140L 800 BUFFER-TIME=1730, FP-POS=4, 1 1840 S FE-TARGET G FLASH=YES (1840 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 | ------------------------------------------------------------------------------------------------------------------------------------ TARGET01-SAFE-TARGE 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A T GE TARGET01-SAFE-TARGE 2 COS/FUV TIME-TA PSA G140L 800 none none none none 1 N/A T G TARGET01-SAFE-TARGE 3 COS/FUV TIME-TA PSA G140L 800 none none none none 1 N/A T G TARGET01-SAFE-TARGE 4 COS/FUV TIME-TA PSA G140L 800 none none none none 2 N/A T G TARGET01-SAFE-TARGE 5 COS/FUV TIME-TA PSA G140L 800 none none none none 2 N/A T G TARGET01-SAFE-TARGE 6 COS/FUV TIME-TA PSA G140L 800 none none none none 3 N/A T G TARGET01-SAFE-TARGE 7 COS/FUV TIME-TA PSA G140L 800 none none none none 3 N/A T G 16046( 5) - 11-Feb-2020 21:12:48 - [ 7] Summary Form for Proposal 16046 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA, V1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV, S/C ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, DATA, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1430, BUFFER-TIME=1730, BUFFER-TIME=200, BUFFER-TIME=660, BUFFER-TIME=970, FLASH=YES, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 1A BY 3 D TO 5 D, ORIENT 115D TO 355 D, POS TARG 232.723, -237.515, QESIPARM ANGLE 279.9, QESIPARM DIST 9.794, SAVE OFFSET V1ASAF, SPEC COM INSTR ECSLOTSET, USE OFFSET V1ASAF ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names TARGET01-SAFE-TARGET, V-V386-SER ------------------------------------------------------------------------------------------------------------------------------------