15184( 4) - 06-Dec-2018 19:12:40 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15184 Version: 4 Check-in Time: 06-Dec-2018 19:12:40 STScI Edit Number: 0 Title The SN Ia Candidate T Pyxidis: Is The Accretion Rate Declining? ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Edward M. Sion Villanova University Y CoI: Dr. Patrick Godon Villanova University N CoI: Dr. Sumner G. Starrfield Arizona State University N CoI: Dr. Robert E. Williams Space Telescope Science Institute N CoI: Dr. Stella Kafka American Association Of Variable Star N Observers CoI: Dr. R. Mark Wagner University of Arizona N CoI: Dr. Matthew James Darnley Liverpool John Moores University N ------------------------------------------------------------------------------------ Abstract T Pyx is a recurrent nova that unexpectedly went into outburst in 2011. It appears to have declined to its quiescent level 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 4.8kpc (Sokoloski et al. 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. However, our most recent COS spectrum reveals that the flux decline continues and, in fact, has actually fallen to a flux level that is 25% below the FUV flux levels observed with IUE between 1981 and 1996, following the 1966 outburst. Moreover, a new strong emission line (Si III + O I) and strong, broad N V (1238, 1242) absorption line appear, not detected in any prior FUV spectra of T Pyx. We propose to continue spectroscopic observations of T Pyx with HST COS during cycle 25, to obtain the first FUV spectra in early quiescence (only six 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 COS spectra of T Pyx during cycle 25, we will detect further changes, if any, in the continuum slope, in the velocity widths and intensities of the emission lines. We will use our suite of modeling codes to study the evolution of the accretion disk. Our analysis will yield the accretion rate, and help determine whether the WD increases its mass to reach the Chandrasekhar limit. Our observations will solidify the identification of recurrent novae as Type Ia Supernova Progenitors. ------------------------------------------------------------------------------------ Observations Description ------------------------ We request two orbits taken successively with COS of the same target. In the first COS is set to G140L 1105, in the second COS is set to G130M 1055. The second orbit/visit is to follow the first orbit/visit immediately. ------------------------------------------------------------------------------------ 15184( 4) - 06-Dec-2018 19:12:40 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NOVA-PYX-189 STAR, ACCRETION DISK, RA=09H04M41.5000S +/- 0.1", J2000 V = 17.5 0 CLASSICAL NOVA, DWARF DEC=-32D22'47.50" +/- 0.1" NOVA, INTERACTING BINARY Reference Frame: ICRS Extended: NO Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 15184( 4) - 06-Dec-2018 19:12:40 - [ 3] Visit: 01 (first visit) Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NOVA-PYX-18 COS/FUV ACQ/PEA PSA G140L 1105 1 6 S (6 S) 90 KXD ------------------------------------------------------------------------------------------------------------------------------------ 2 NOVA-PYX-18 COS/FUV ACQ/PEA PSA G140L 1105 NUM-POS=5.0, STEP-SIZE=0.9, 1 6 S (6 S) 90 KD CENTER=FLUX-WT-FLR ------------------------------------------------------------------------------------------------------------------------------------ 3 NOVA-PYX-18 COS/FUV TIME-TA PSA G140L 1105 BUFFER-TIME=518, FP-POS=ALL 1 518 S 90 G see below (1876 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NOVA-PYX-1890 1 COS/FUV ACQ/PEA PSA G140L 1105 none none none none 1 N/A KXD NOVA-PYX-1890 2 COS/FUV ACQ/PEA PSA G140L 1105 none none none none 1 N/A KD NOVA-PYX-1890 3 COS/FUV TIME-TA PSA G140L 1105 none none none 1 1 469.0 S G NOVA-PYX-1890 3 COS/FUV TIME-TA PSA G140L 1105 none none none 2 1 469.0 S G NOVA-PYX-1890 3 COS/FUV TIME-TA PSA G140L 1105 none none none 3 1 469.0 S G NOVA-PYX-1890 3 COS/FUV TIME-TA PSA G140L 1105 none none none 4 1 469.0 S G 15184( 4) - 06-Dec-2018 19:12:40 - [ 4] Visit: 02 (second visit) Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NOVA-PYX-18 COS/FUV ACQ/PEA PSA G130M 1291 1 6 S (6 S) 90 KXD ------------------------------------------------------------------------------------------------------------------------------------ 2 NOVA-PYX-18 COS/FUV ACQ/PEA PSA G130M 1291 NUM-POS=5.0, STEP-SIZE=0.9, 1 6 S (6 S) 90 KD CENTER=FLUX-WT-FLR ------------------------------------------------------------------------------------------------------------------------------------ 3 NOVA-PYX-18 COS/FUV TIME-TA PSA G130M 1055 BUFFER-TIME=518, FP-POS=ALL 1 518 S 90 G see below (1836 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NOVA-PYX-1890 1 COS/FUV ACQ/PEA PSA G130M 1291 none none none none 1 N/A KXD NOVA-PYX-1890 2 COS/FUV ACQ/PEA PSA G130M 1291 none none none none 1 N/A KD NOVA-PYX-1890 3 COS/FUV TIME-TA PSA G130M 1055 none none none 1 1 459.0 S G NOVA-PYX-1890 3 COS/FUV TIME-TA PSA G130M 1055 none none none 2 1 459.0 S G NOVA-PYX-1890 3 COS/FUV TIME-TA PSA G130M 1055 none none none 3 1 459.0 S G NOVA-PYX-1890 3 COS/FUV TIME-TA PSA G130M 1055 none none none 4 1 459.0 S G 15184( 4) - 06-Dec-2018 19:12:40 - [ 5] Summary Form for Proposal 15184 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAKD, ACQ/PEAKXD, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=518, CENTER=FLUX-WT-FLR, FP-POS=ALL, NUM-POS=5.0, STEP-SIZE=0.9 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names NOVA-PYX-1890 ------------------------------------------------------------------------------------------------------------------------------------