While the accreting pulsating white dwarfs in dwarf novae systems only have outbursts recur on 20-30 yr timescales, 4 of the 13 known had outbursts in 2006-2007. The white dwarfs stopped pulsating, as the outburst heating caused them to move out of the instability strip. These outburst events give us the unprecedented opportunity to follow the emergence of the non-radial pulsations as they re-enter the strip. Unlike single white dwarfs, where cooling takes place on thousand year timescales, the cooling rates for white dwarfs following dwarf nova outbursts are only 3-5 yrs, with Cycle 18 ideally suited to catch this transition. Our past HST observations have shown that the UV is critical to a correct temperature determination (the white dwarf dominates over the disk emission in the UV and the Ly alpha turnover provides a crucial constraint) and mode identification (the UV/optical pulsation amplitude is typically 6-17 and indicative of low order modes). We propose to use COS in TIME-TAG mode to obtain the temperatures and UV pulsation amplitudes of the 4 post-outburst systems.

Our primary goal is to obtain a summed spectrum with sufficient S/N to allow a temperature fit with models, with a secondary goal to obtain time-resolved light curves to detect or constrain the UV pulsation amplitude. We plan to use 2 orbits on each of the 4 objects with COS and grating G140L. We expect the white dwarfs in the 4 objects to be between 11,000-15,000K (we know the quiescent temperatures of V455 And and GW Lib from prior HST observations and they may be somewhat hotter post outburst than pre-outburst). We used a Hubeny (1988) model white dwarf for 12,500K white dwarf at 100 pc as input to the COS ETC G140L (grating setting 1105). This provides a S/N of 22 per resolution element at 1500°A for 1 orbit. GW Lib is at a similar distance but has a hotter temperature so it will produce a higher S/N. We expect SDSSJ0745+45 will have a comparable (or hotter) temperature than GW Lib, but its distance is larger by a factor of 4, so the combined two orbits with some binning will be required to achieve a good temperature derivation. For V455 And, the temperature may be down to its quiescent value of 10,500K, in which case the two orbits will provide a good temperature determination. The previous quiescent observation with STIS was done during a snapshot program with only a short 700 sec observation that extended to 1700°A. The better sensitivity and longer redward wavelength coverage of COS is better suited to cooler white dwarfs. In addition, the short snapshot exposure did not allow the determination of the UV pulse amplitude. With COS, the pulse amplitude will be measurable if the amplitude is large (expected for low order modes). For GW Lib, the pulsation periods evident in UV and optical at quiescence were in the 230-650s range and the optical pulsation periods of V455 And are around 340 sec. If the white dwarf driving zones are hotter than pre-outburst, the periods are expected to be shorter than quiescence once they return. Thus, 2 HST orbits (about 80 min total time) with light curves created by summing the time-tag fluxes over several hundred °A and several minutes should be able to detect or place limits on the UV amplitudes. The planned continuation of our ground monitoring observations will be used to delineate the optical pulse periods and amplitudes in all cases. HOT STARS 12 false 0.0 0.0 false false false false AVAILABLE STAR DWARF NOVA PULSATING VARIABLE This objece is in the GSC2 catalog but published ICRS coords and pm by Thorstensen (2003) are used J2000 J2000 F-CONT(1700)=4.0E-15, F-LINE(1550)=9E-15,W-LINE(1550)=6 STAR DWARF NOVA PULSATING VARIABLE Object is in GSC2 catalog but coords and pm from published values by Thorstensen in Araujo-Betancor et al. 2005 J2000 J2000 F-CONT(1700)=4.0E-15,F-LINE(1550)=1.9E-14,W-LINE(1550)=13 STAR DWARF NOVA PULSATING VARIABLE J2000 J2000 F-CONT(1700)=5.8E-16 STAR DWARF NOVA PULSATING VARIABLE J2000 J2000 F-CONT(1700)=1.75E-15 UNIDENTIFIED BLANK FIELD This target is a blank piece of sky which is the bright object safe pointing and is 9.752 arcseconds away at a PA 165.1 degrees from Target #3. J2000 UNIDENTIFIED BLANK FIELD This target is a blank piece of sky which is the bright object safe pointing and is 9.063 arcseconds away at a PA 180.9 degrees from Target #4. J2000 UNIDENTIFIED BLANK FIELD This target is a blank piece of sky which is the bright object safe pointing and is 9.177 arcseconds away at a PA 0.8 degrees from Target #1. J2000 UNIDENTIFIED BLANK FIELD This target is a blank piece of sky which is the bright object safe pointing and is 9.048 arcseconds away at a PA 271.4 from Target #2. COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. 1302353821000 309.1340181099048 (Tic-Visit :proposal-id 12231 :visit-id "01" :proposal-version -1 :trans-version "20100505" :date "08-Jul-2010 13:54:29.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 174016 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12231 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12231 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2885 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12231 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3035 :al-overhead-at-end 0 :internal-dur-at-end 428 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) false 2 0 This visit allocates and sets up the safe position offset slot for visit 01 which will use that slot. 1302041194000 309.134017944 false -1 -1 This visit is for BOP checking the "safe" target only and should not execute onboard HST. (Tic-Visit :proposal-id 12231 :visit-id "01" :proposal-version -1 :trans-version "20100505" :date "08-Jul-2010 13:54:29.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 174016 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12231 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12231 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2885 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12231 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3035 :al-overhead-at-end 0 :internal-dur-at-end 428 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) false 2 0 The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12231 :visit-id "02" :proposal-version -1 :trans-version "20100505" :date "08-Jul-2010 13:54:58.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 174016 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12231 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12231 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2929 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3301 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12231 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3079 :al-overhead-at-end 0 :internal-dur-at-end 428 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3301 :pcs-gap 0 ) false 2 0 This visit allocates and sets up the safe position offset slot for visit 02 which will use that slot. false -1 -1 This visit is for BOP checking the "safe" target only and should not execute onboard HST. (Tic-Visit :proposal-id 12231 :visit-id "02" :proposal-version -1 :trans-version "20100505" :date "08-Jul-2010 13:54:58.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 174016 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12231 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12231 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2929 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3301 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12231 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3079 :al-overhead-at-end 0 :internal-dur-at-end 428 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3301 :pcs-gap 0 ) false 2 0 The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. 1299993725000 114.0 (Tic-Visit :proposal-id 12231 :visit-id "03" :proposal-version -1 :trans-version "20100505" :date "08-Jul-2010 13:55:18.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 174016 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12231 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12231 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3048 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3391 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12231 :visit-id "03" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3169 :al-overhead-at-end 0 :internal-dur-at-end 428 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3391 :pcs-gap 0 ) false 2 0 This visit allocates and sets up the safe position offset slot for visit 03 which will use that slot. 1299715801000 114.0 false -1 -1 This visit is for BOP checking the "safe" target only and should not execute onboard HST. (Tic-Visit :proposal-id 12231 :visit-id "03" :proposal-version -1 :trans-version "20100505" :date "08-Jul-2010 13:55:18.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 174016 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12231 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12231 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3048 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3391 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12231 :visit-id "03" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3169 :al-overhead-at-end 0 :internal-dur-at-end 428 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3391 :pcs-gap 0 ) false 2 0 The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12231 :visit-id "04" :proposal-version -1 :trans-version "20100505" :date "08-Jul-2010 13:55:36.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 174016 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12231 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12231 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3073 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3445 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12231 :visit-id "04" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3223 :al-overhead-at-end 0 :internal-dur-at-end 428 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3445 :pcs-gap 0 ) false 2 0 This visit allocates and sets up the safe position offset slot for visit 04 which will use that slot. false -1 -1 This visit is for BOP checking the "safe" target only and should not execute onboard HST. (Tic-Visit :proposal-id 12231 :visit-id "04" :proposal-version -1 :trans-version "20100505" :date "08-Jul-2010 13:55:36.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 174016 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12231 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12231 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3073 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3445 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12231 :visit-id "04" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3223 :al-overhead-at-end 0 :internal-dur-at-end 428 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3445 :pcs-gap 0 ) false 2 0