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

• Published in: The Astrophysical journal Vol. 788; no. 2; pp. 130 - 13
• Main Authors: Chomiuk, Laura, Nelson, Thomas, Mukai, Koji, Sokoloski, J. L., Rupen, Michael P., Page, Kim L., Osborne, Julian P., Kuulkers, Erik, Mioduszewski, Amy J., Roy, Nirupam, Weston, Jennifer, Krauss, Miriam I.
• Format: Journal Article
• Language: English
• Published: United States 20.06.2014
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Delay; DETECTION; Ejecta; Ejection; EV RANGE; HARD X RADIATION; KEV RANGE; Light curve; MASS; Nova; NOVAE; Outbursts; OXYGEN; PHOTOSPHERE; PLASMA; SOFT X RADIATION; VISIBLE RADIATION; WAVELENGTHS; WHITE DWARF STARS; X-rays
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/788/2/130

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 sub([odot])). The late turn-on time of the super-soft component yields a large nova ejecta mass ([gap]10 super(-5) M sub([odot])), 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.