0 Assigned ID: 1201 ----- Attempting Submission 1 (Thu Feb 28 08:41:11 GMT 2013) ----- HST Phase I Proposal 1201 (rxj0439.apt) successfully submitted. ----- Attempting Submission 2 (Fri Mar 01 05:08:14 GMT 2013) ----- Hi Amber, here is my phase II. Cheers, Boris -1316703198 ----- Attempting Submission 1 (Tue Jun 25 21:07:05 GMT 2013) ----- The supersoft X-ray source RXJ0439.8-6809, identified with a faint (V=21.7) very blue star in the direction of the LMC is one of the most extreme stellar objects known. Current models require it to be either: (a) the hottest (Teff~300000K) and most massive known pre-white dwarf. In this case, it would allow a real-time observational test of stellar evolution theory, as it will evolve along the white dwarf cooling track by measurable amounts within a decade; or: (b) the first known double degenerate supersoft X-ray source, i.e. an interacting binary with a shell-burning accreting white dwarf and a degenerate donor star, which would make it a very good candidate for a type Ia supernova progenitor. Alas, despite major observational efforts, including an exploratory 1-orbit Cycle 7 HST low-resolution ultraviolet spectrum, it is so far not possible to distinguish between these two scenarii. We propose to invest a modest amount of HST/COS time to finally determine the true nature of RXJ0439.8-6809. Crucially, we will obtain the first high-resolution ultraviolet spectrum of this system to confirm the LMC membership of RXJ0439.8-6809 from the detection of interstellar absorption lines at the LMC systemic velocity. In addition, we will use this spectrum to obtain a second-epoch effective temperature measurement, which we will compare that from Cycle 7. The excellent flux calibration of HST will easily detect a change of a few 10000K, which is predicted for the evolution of a massive white dwarf over the fifteen-year baseline (Cycle 7 to 21) The aim of this program is to obtain high-resolution far-UV spectroscopy of a hot blue star in the LMC, which is either a hot pre-white dwarf or a stable shell-burning white dwarf in a very compact binary. The co-ordinates are good to ~0.5", and the current Phase II implementation includes an ACQ/SEARCH pattern, however, we will endeavour to provide updated and improved ground-based coordinates that will allow to proceed with an ACQ/Image only. The acquisition is followed G130M spectroscopy using all four FP-POS positions. The object is briefly in the CVZ, which greatly improves the efficiency of the observatory. HOT STARS 12 false true 0.0 0.0 false false false SUPPORTED STAR LMXB NOVA-LIKE This target is either a supersoft X-ray binary (stable shell burning white dwarf) or a hot single pre-white dwarf. We observed it with STIS in November 1998 (data sets O55G01010 & O55G01020). The target has also been observed with GALEX in December 2005, finding it at F(1528A)=8.3+-0.9e-15 erg/cm2/s/AA and F(2271A)=2.3+-0.07e-16 erg/cm2/s/AA, consistent with the STIS observations. J2000 J2000 F(1300A)=1.5e-15 erg/cm2/s/AA, F(1528A)=8.3+-0.9e-15 erg/cm2/s/AA and F(2271A)=2.3+-0.07e-16 erg/cm2/s/AA COS/FUV Spectroscopic No No G130M 1291 The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. 1372192466925 /tmp/OPVisit5974650176106779741.xml (Tic-Visit :proposal-id 13289 :visit-id "01" :proposal-version -1 :trans-version "20130502" :date "25-Jun-2013 21:34:26.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 365520 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13289 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :cvz T :proposal-id 13289 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 16551 :al-overhead-at-end 0 :internal-dur-at-end 366 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 0 :low-sky "N" :pcs-visibility 0 :pcs-gap 0 ) true 3 0