15072( 4) - 08-Mar-2018 17:06:59 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15072 Version: 4 Check-in Time: 08-Mar-2018 17:06:59 STScI Edit Number: 0 Title The classical nova hibernation scenario: a definitive confirmation ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Boris T. Gaensicke The University of Warwick Y CoI: Dr. Paul Chote The University of Warwick N CoI: Dr. JJ Hermes University of North Carolina at Chapel N Hill CoI: Prof. Tom R. Marsh The University of Warwick N CoI: Prof. Detlev G. Koester Universitat Kiel N CoI: Ms. Odette Fabiola Toloza The University of Warwick N Castillo CoI: Dr. Dean Townsley University of Alabama N ------------------------------------------------------------------------------------ Abstract The detached white dwarf plus M-dwarf binary LL Eri exhibits truly unique behaviour within this class of compact binaries. As part of a COS snapshot survey, we detected large-amplitude variability in the ultraviolet flux of the white dwarf, confirmed by extensive ground-based blue-band photometry. The three independent frequencies detected in the light curves clearly identify this variability as non-radial pulsations of the white dwarf. However, with a hydrogen atmosphere and Teff=17200K, this white dwarf is nearly 5000K hotter than the canonical instability strip. The COS spectrum, albeit noisy, reveals that the metal lines typically detected in this class of stars, arising from material captured from the M-dwarf wind, are very broad. If interpreted as rotationally broadened, they imply a spin of only a few minutes. Such a short period could be explained by a past phase of intense accretion of mass and angular momentum. It has been postulated for over thirty years that classical nova eruptions on the white dwarf could cause such switching from a semi-detached to a detached binary configuration, during which the system "hibernates" - yet, to date no hibernating nova has been identified. However, the broad lines could also be due to pulsation-driven surface velocity fields, in which case the nature and past evolution of LL Eri would not be easily linked to any exisiting scenario for compact binary evolution. We propose to obtain a deeper COS observations to unambiguosly determine whether the cause of the observed line broadening is due to rapid rotation, which would unequivocally confirm the hibernation scenario. ------------------------------------------------------------------------------------ Observations Description ------------------------ This is a white dwarf + M-dwarf binary post common envelope binary (PCEB). The white dwarf parameters are Teff=17200K, log g=8.25, and the spectral type of the companion is M2.5V. 15072( 4) - 08-Mar-2018 17:06:59 - [ 2] The white dwarf was observed in the UV with COS as part of a snapshot program in Cycle 19 (LBOVNN010), and the metal lines in the white dwarf photoshpere are significantly broader than in any other PCEB, and the time-tag data reveals short-period non-radial pulsations of the white dwarf. The goal of this program is to obtain high S/N data of the metal lines to determine whether they are broadened due to rapid rotation of the white dwarf, or due to the surface motion of the non-radial pulsations. The Cycle 25 observations are very similar to those carried out in Cycle 19: target acquisition using ACQ/IMAGE (coordinates and proper motions are good), using MIRRORB. The major difference is that we will use the new 1223A setting, which will provide coverage of the red wing of Ly beta as well (which will help to probe for temperature modulations as a function of pulsation phase), and at the same time covers the strongest lines (Si II 1260/65A, C II 1335A, CIII1175A). 2018-Mar-08: changed the target acq. to BOA/MirrorA to pass the M-dwarf clearing procedure. ------------------------------------------------------------------------------------ 15072( 4) - 08-Mar-2018 17:06:59 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 LL-ERI STAR, DA RA=03H32M43.4600S +/- 0.5", J2000 V = 14.60 +/- 0.1 GALEX FUV=5655microJy DEC=-08D55'39.30" +/- 0.5" GALEX NUV=4519microJy Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.008806690674314293 -0.1055 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 15072( 4) - 08-Mar-2018 17:06:59 - [ 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 LL-ERI COS/NUV ACQ/IMA BOA MIRRORA 1 145 S (145 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 LL-ERI COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=500, FLASH=YES, 1 2247 S G FP-POS=1 (2247 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 LL-ERI COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=500, FLASH=YES, 1 2919 S G FP-POS=2 (2919 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 LL-ERI COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=500, FLASH=YES, 1 2919 S G FP-POS=3 (2919 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 LL-ERI COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=500, FLASH=YES, 1 2919 S G FP-POS=4 (2919 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 LL-ERI COS/FUV TIME-TA PSA G130M 1222 BUFFER-TIME=500, FLASH=YES, 1 2919 S G FP-POS=1 (2919 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 | ------------------------------------------------------------------------------------------------------------------------------------ LL-ERI 1 COS/NUV ACQ/IMA BOA MIRRORA none none none none 1 N/A GE LL-ERI 2 COS/FUV TIME-TA PSA G130M 1222 none none none none 1 N/A G LL-ERI 3 COS/FUV TIME-TA PSA G130M 1222 none none none none 2 N/A G LL-ERI 4 COS/FUV TIME-TA PSA G130M 1222 none none none none 3 N/A G LL-ERI 5 COS/FUV TIME-TA PSA G130M 1222 none none none none 4 N/A G LL-ERI 6 COS/FUV TIME-TA PSA G130M 1222 none none none none 5 N/A G 15072( 4) - 08-Mar-2018 17:06:59 - [ 5] Summary Form for Proposal 15072 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures BOA, PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=500, FLASH=YES, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, MIRRORA ------------------------------------------------------------------------------------------------------------------------------------ Target Names LL-ERI ------------------------------------------------------------------------------------------------------------------------------------