0 Assigned ID: 586 ----- Attempting Submission 1 (Fri Apr 11 16:47:48 GMT 2014) ----- This is a resubmission, with adjustments to the FUV aperture to ensure photometric accuracy for the time series observation of LS IV-14 116, and a slight adjustment to the central wavelength of the NUV echelle to maximise wavelength coverage. -1585994348 ----- Attempting Submission 1 (Fri Jul 18 13:55:10 GMT 2014) ----- HST Phase II Proposal 13800 (ls4s14_phase2.apt) successfully submitted. ----- Attempting Submission 2 (Fri Jul 18 13:55:59 GMT 2014) ----- HST Phase II Proposal 13800 (ls4s14_phase2.apt) successfully submitted. ----- Attempting Submission 3 (Tue Jul 22 17:35:07 GMT 2014) ----- Heavy-metal, extreme chemistry and puzzling pulsation: ultraviolet clues to the formation of hot subdwarfs Subdwarf B stars are low-mass core-helium burning stars with a very thin hydrogen envelope; in most cases, surface helium and light elements are depleted, heavy elements are enhanced by a factor ten. It is argued that normal He-poor sdB stars evolve from giants which have been stripped almost to the core to reveal helium-enriched material. As the star ignites helium and contracts to the extreme horizontal branch, radiative processes re-stratify the internal chemistry of the atmosphere and the helium sinks. When does this happen, how long does it take, and what does it look like? A small number of sdB stars have intermediate helium abundances (He-sdB) and a few have extraordinary surface compositions. The pulsating "zirconium" star LS IV-14 116 shows a four dex overabundance of zirconium, yttrium and strontium. Two other He-sdBs show a four dex overabundace of lead. Such stars are almost completely unexplored in the space ultraviolet. We will observe the ultraviolet spectrum of LS IV-14 116 and two other chemically peculiar hot subdwarfs in order to determine: (a) the impact of extraordinary composition on their overall flux distribution and hence on measurements of their effective temperatures, (b) the degree of stratification in the atmosphere (how thick is the enhanced layer?), and (c) the abundances of species not observable in the visible. (d) the ultraviolet lightcurve due to the principle pulsation modes of LS IV-14 116. The observations will allow us to explore the processes that lead to heavily stratified atmospheres and to the transformation of red giants with helium-enriched surface into horizontal-branch stars with helium-poor surfaces. 1. Description of Observations. We require wide spectral coverage observations of ALS-11634 (LS IV-14 116), PG 0909+276 and [CW83] 0512-08, in the NUV and FUV at a spectral resolution sufficient to resolve narrow lines in crowded spectral regions. A S/N ratio better than 30 at a spectral resolution 30000 is normally required to establish chemical abundances with confidence. The required data are provided by the medium-resolution echelle E230M and E140M grisms centered at 1978 A and 1425 A to cover the wavelength ranges 1700-2370 A and 1160-1730 A respectively. We also require time-resolved FUV spectroscopy of ALS-11634 (LS IV-14 116) in order to measure the flux variation due to the principal pulsation mode (P = 1957 s). The pulsation amplitude is 0.27% in white light (22), and is expected to be more than this in the FUV by a factor of a few, so we require < 0.1% photometric precision with a time resolution better than 10/P, i.e. texp ~ 180s. Photometric precision can be achieved by a combination of binning over wavelength and/or phase. FUV times-series spectroscopy will also be obtained with the medium-resolution echelle and E140M grism centered at 1425 A, using repeated 180 s exposures. The observations will be obtained on 3 visits comprising a total of 7 orbits as allocated. Visit 1: 1 Orbit: TYC-5331-1560-1 = CW 0512-08 to acquire both NUV and FUV spectra in the same orbit. Visit 2: 2 Orbits: TYC-1954-398-1 = PG 0909+276 to acquire both NUV and FUV spectra, one in each orbit. Visit 3. 4 Orbits: ALS-11364 = LS IV -14 116 to acquire the mean NUV spectrum (one orbit) and time-resolved exposures of the FUV spectrum (three orbits). 2, Justification of Real-time Observations and Special Scheduling We have no real-time or special scheduling requirements. We will endeavour to obtain simultaneous, or near-simultaneous ground-based observations for Visit 3 if the likely schedule is known sufficiently well in advance. 3. Justification of Special Calibration Requirements No special calibrations are required, except that for the repeated FUV spectra of LS IV -14 116 we ask that WAVECAL exposures are carried out during the Earth Occultation periods in or der to maximise on-target exposure times. 4. Additional Comments HOT STARS Default false true false false false SUPPORTED STAR PULSATING VARIABLE SDO This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 STAR SDO This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 STAR SDO This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/NUV-MAMA Spectroscopic No No E230M 1978 STIS/FUV-MAMA Spectroscopic No No E140M 1425 STIS/NUV-MAMA Spectroscopic No No E230M 1978 STIS/FUV-MAMA Spectroscopic No No E140M 1425 STIS/NUV-MAMA Spectroscopic No No E230M 1978 The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13800 :visit-id "01" :proposal-version -1 :trans-version "20140605" :date "22-Jul-2014 18:30:07.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 174512 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13800 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13800 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2888 :al-overhead-at-end 0 :internal-dur-at-end 394 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3222 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13800 :visit-id "02" :proposal-version -1 :trans-version "20140605" :date "22-Jul-2014 18:30:18.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 191952 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13800 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13800 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2908 :al-overhead-at-end 0 :internal-dur-at-end 113 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3241 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13800 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3019 :al-overhead-at-end 194 :internal-dur-at-end 319 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3241 :pcs-gap 0 ) true 2 0 /private/var/folders/0c/5011wfl508g14lx4917hgxmr0006vr/T/OPVisit7642541764440809884.xml The scheduling data was generated by CASM 22.2. CASM was run in Phase II mode. 53 (Tic-Visit :proposal-id 13800 :visit-id "03" :proposal-version -1 :trans-version "20140605" :date "07-Jan-2015 12:35:19.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 4 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 2870928 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13800 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13800 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2847 :al-overhead-at-end 0 :internal-dur-at-end 113 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3180.0 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13800 :visit-id "03" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2951 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3180.0 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13800 :visit-id "03" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2955 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3180.0 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13800 :visit-id "03" :orbit-number 4 :pcs-time 222 :si-vis-utilization 2955 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3180.0 :pcs-gap 0 ) true 4 0 0.2x0.2 aperture chosen for photometric precision.