The 2011 outburst of recurrent nova T Pyx: X-ray observations expose the white dwarf mass and ejection dynamics

Laura Chomiuk, Thomas Nelson, Koji Mukai, J. L. Sokoloski, Michael P. Rupen, Kim L. Page, Julian P. Osborne, Erik Kuulkers, Amy J. Mioduszewski, Nirupam Roy, Jennifer Weston, Miriam I. Krauss

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

Original languageEnglish (US)
Article number130
JournalAstrophysical Journal
Issue number2
StatePublished - Jun 20 2014


  • X-rays: stars
  • novae, cataclysmic variables
  • stars: individual (T Pyxidis)
  • white dwarfs


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