0 Assigned ID: 392 ----- Attempting Submission 1 (Fri Apr 05 10:39:42 GMT 2019) ----- INEFFICIENT ORDERING OF FP-POS POSITIONS 0 ----- Attempting Submission 1 (Fri Jul 19 07:15:25 GMT 2019) ----- The warning concern the FP-POS switching, which is no concern as the FP-POS movement happen during Earth occultation White dwarfs are the end states of all stars less massive than 8-10 solar masses. Encrypted inside these stellar remnants is a record of the evolutionary history of the progenitor stars, providing a wealth of information about the evolution of stars, star formation, and the age of a variety of stellar populations. However, the internal structure and composition of white dwarfs are hidden by their high gravities, which causes all elements, apart from hydrogen and helium, to settle out of their atmospheres. An exciting system has recently been discovered, the first pulsating white dwarf in an eclipsing binary. Both binary modeling and asteroseismology of the pulsation periods are available to reveal the core composition of this roughly 0.35 solar-mass stellar remnant. Current modeling can constrain the radius of this white dwarf to around 5%, but by constraining the limb darkening via the temperature of the primary we can obtain a factor of five improvement to roughly 1% uncertainty. Only by measuring the temperature of the hotter star in the binary with COS FUV spectroscopy can we unlock the full potential of this unique system to accurately constrain the core composition of a 0.35 solar-mass white dwarf, accurately testing whether it has a helium-, carbon-oxygen, or even hybrid core composition. It will serve as a powerful benchmark to empirically constrain the core composition of low-mass stellar remnants and investigate the effects of close binary evolution on the internal structure of white dwarfs. The goal of this proposal is to obtain phase-resolved far-ultraviolet spectroscopy of the eclipsing double-white dwarf binary SDSS1152+0248. This data will be used to (1) measure the effective temperature and surface gravity from the well-calibrated COS/G140L spectrum, and (2) obtain high-quality far-ultraviolet light curves of the primay eclipse, from which we will measure the stellar radii. The target will be acquired using COS/NUV imaging, followed by time-tagged COS/G140L spectroscopy. During the primary eclipse, the ultraviolet flux will drop dramitcally, hence we need to ensure via a phase constraint that the target acqusition occurs outside the primary eclipse. The ephemeris is HJD(UTC) = 2457461.1502539(10) + 0.09986526542(10)E and we need to acquire somewhere in the phase interval 0.15 - 0.85. In principle, the phase constraint only applies to the first exposure, the short NUV acquisition image - however, the scheduling software doesn't cope well with periods shorter than the visit duration. Therefore we provide APT with three times the orbital period, 0.3994610617, and the phase window 0.05 - 0.285. This will probably reduce the number of scheduling opportunities by a factor three as well - if that becomes a problem, we need to re-think the strategy again. APT warns about the inefficien sequence of the FP-POS changes, but that's not a problem as we switch FP-POS during Earth occultation. Our team possesses the knowledge and expertise to achieve the results outlined in our case. In particular, we highlight the cases presented in Bours et al. 2015 (MNRAS, 448, 601) and Bours et al. 2015 (MNRAS, 450, 3966), where we established the expertise required to analyse UV spectroscopy of double white dwarf binaries specifically with the aim of accurately determining the temperatures of both white dwarfs. The aim of this proposal is identical to those previously published by our team. Our team includes: Prof. Gaensicke, an expert in the reduction and analysis of HST STIS spectroscopic data. Prof. Gaensicke has extensive experience fitting the far-UV spectra of white dwarfs and will be responsible for reducing the data and fitting it with the latest state-of-the-art white dwarf models. Dr. Parsons, Dr. Littlefair, Prof. Dhillon and Prof. Marsh are all experts in the observation and analysis of white dwarf binary systems and have carried out the ground-based observations that lead to the discovery of pulsations in this system. They will be responsible for combining the HST and ground-based results to determine precise physical parameters for the pulsating white dwarf. Dr. Hermes is an expert in the observation and analysis of pulsating white dwarfs. Once the physical paramters of the white dwarf have been measured Dr. Hermes will perform the asteroseismic analysis. All members of our team are experienced Hubble users. Stellar Physics 6 false false true false false false false SUPPORTED STAR DA NO J2000 J2000 FUV=17.962+/-0.069, NUV=18.270+/-0.048 COS/FUV Spectroscopic No No G140L 800 1563519878130 /tmp/OPVisit12174733346413454347.xml Phase windows are not calculated when the gap between schedulable intervals is less than 1 days, assuming no scheduling restrictions for constraint Phase 0.050/0.285. The scheduling data was generated by CASM 27.2. CASM was run in Phase II mode. 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