The SN Ia Candidate T Pyxidis: The Mystery of its High Accretion Rate

0 Assigned ID: 701 ----- Attempting Submission 1 (Fri Apr 10 19:19:35 GMT 2015) ----- INEFFICIENT ORDERING OF FP-POS POSITIONS INEFFICIENT ORDERING OF FP-POS POSITIONS The phase II has been checked and optimized by Steve Penton. We were told to ignore the warnings. 1004919556 ----- Attempting Submission 1 (Mon Jul 13 16:59:27 GMT 2015) ----- The phase II has been checked, optimized and approved by Steve Penton (penton@stsci.edu) and we were told to ignore the warnings. The SN Ia Candidate T Pyxidis: The Mystery of its High Accretion Rate T Pyx is a recurrent nova that unexpectedly went into outburst in 2011. It has now declined to its quiescent level but it appears to be accreting at a very high rate, possibly driven by irradiation of the donor star by the hot white dwarf or by the hot inner disk. Our team (Godon et al. 2014) has shown, using the light echo distance of 4.8 kpc (Sokoloski 2013), that the white dwarf in T Pyx is actually growing in mass and might be on its way to exploding as a Type Ia supernova. We propose to continue spectroscopic monitoring of T Pyx with HST COS during Cycle 23, to obtain the first FUV spectrum early in the quiescent period (only four years after its 44 years-delayed outburst). The first FUV spectra of T Pyx following its 1967 outburst were a full 13 years later, in 1980, when IUE was launched. By obtaining FUV spectra with COS at the beginning and at the end of Cycle 23, we will detect any changes in the continuum slope, in the velocity widths and intensities of emission lines. We will use our extensive suite of modeling codes to study the evolution of the accretion disk and also model the stellar photosphere, if detected. Our analysis will yield the accretion rate, WD temperature and elemental abundances. We will compare these data to our values obtained on the decline from outburst and transition into quiescence. Our observations will provide fiducial spectra from 1800A down to 912A for this puzzling and pivotal recurrent nova, and would solidify the identification of recurrent novae as Type Ia Supernova progenitors. T Pyx is the only target. We request that T Pyx be observed at two epochs. The first epoch at the beginning of Cycle 23. The second epoch toward the end of Cycle 23. The observations for the first and second epoch are identical. Each epoch consists of two consecutive observations, each of which lasts only one orbit (so that each epoch lasts only 2 orbits, for a total of 4 orbits). Each epoch consists of two consecutive observations as follows: A first observation/orbit with COS in the FUV spectroscopic configuration G140L central wave 1105A, directly followed by another COS observation/orbit in the FUV spectroscopic configuration G130 at wave 1055A. HOT STARS 12 false true false false SUPPORTED STAR RECURRENT NOVA NO This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G130M 1055 COS/FUV Spectroscopic No No G130M 1055 E:\Patrick\ciao\ciao2\tex\papers\proposals\HST\2015\Tpyx\OP-cache\14111_v0-v01.xml 1436465243413 The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14111 :visit-id "01" :proposal-version -1 :trans-version "20150609" :date "09-Jul-2015 14:07:23.0" :trans-errors '(:WARNINGS 1 :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 435120 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14111 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14111 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2911 :al-overhead-at-end 0 :internal-dur-at-end 114 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3245 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14111 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3023 :al-overhead-at-end 0 :internal-dur-at-end 341 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3245 :pcs-gap 0 ) true 2 0 2 s should be sufficient, but use 7s in case the target has faded 2 s should be sufficient, but use 7s in case the target has faded ETC BT is 2704, 2/3 of this is 1800, 1000 just to safe (and efficient) ETC BT=8936, 2/3 of which is 6000. Just 800 to match Orbit 2 Use BT=ET-110 for max efficiency. ETC gives BT=6000. (shorter is ok) Use BT=ET-110 for max efficiency. ETC gives BT=6000. (shorter is ok) Use BT=ET-110 for max efficiency. ETC gives BT=6000. (shorter is ok) 1436457280732 The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. E:\Patrick\ciao\ciao2\tex\papers\proposals\HST\2015\Tpyx\OP-cache\14111_v0-v02.xml (Tic-Visit :proposal-id 14111 :visit-id "02" :proposal-version -1 :trans-version "20150609" :date "09-Jul-2015 11:54:40.0" :trans-errors '(:WARNINGS 1 :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 435120 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14111 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14111 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2911 :al-overhead-at-end 0 :internal-dur-at-end 114 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3245 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14111 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3023 :al-overhead-at-end 0 :internal-dur-at-end 341 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3245 :pcs-gap 0 ) true 2 0 2 s should be sufficient, but use 7s in case the target has faded 2 s should be sufficient, but use 7s in case the target has faded ETC BT is 2704, 2/3 of this is 1800, 1000 just to safe (and efficient) ETC BT=8936, 2/3 of which is 6000. Just 800 to match Orbit 2 Use BT=ET-110 for max efficiency. ETC gives BT=6000. (shorter is ok) Use BT=ET-110 for max efficiency. ETC gives BT=6000. (shorter is ok) Use BT=ET-110 for max efficiency. ETC gives BT=6000. (shorter is ok)