THE 2011 OUTBURST OF RECURRENT NOVA T Pyx: X-RAY OBSERVATIONS EXPOSE THE WHITE DWARF MASS AND EJECTION DYNAMICS

摘要

The recurrent nova T Pyx underwent its sixth historical outburst in 2011, and became the subject of an intensive\udmulti-wavelength observational campaign. We analyze data from the Swift and Suzaku satellites to produce a detailed\udX-ray light curve augmented by epochs of spectral information. X-ray observations yield mostly non-detections\udin the first four months of outburst, but both a super-soft and hard X-ray component rise rapidly after Day 115.\udThe super-soft X-ray component, attributable to the photosphere of the nuclear-burning white dwarf, is relatively\udcool (∼45 eV) and implies that the white dwarf in T Pyx is significantly below the Chandrasekhar mass (∼~1 M☉ ).\udThe late turn-on time of the super-soft component yields a large nova ejecta mass (~> 10^−5 M☉), consistent with\udestimates at other wavelengths. The hard X-ray component is well fit by a ∼1 keV thermal plasma, and is attributed\udto shocks internal to the 2011 nova ejecta. The presence of a strong oxygen line in this thermal plasma on Day 194\udrequires a significantly super-solar abundance of oxygen and implies that the ejecta are polluted by white dwarf\udmaterial. The X-ray light curve can be explained by a dual-phase ejection, with a significant delay between the first\udand second ejection phases, and the second ejection finally released two months after outburst. A delayed ejection\udis consistent with optical and radio observations of T Pyx, but the physical mechanism producing such a delay\udremains a mystery.