Abstract
The Swift GRB satellite is an excellent facility for studying novae. Its rapid response time and sensitive X-ray detector provides an unparalleled opportunity to investigate the previously poorly sampled evolution of novae in the X-ray regime. This paper presents Swift observations of 52 Galactic/Magellanic Cloud novae. We included the XRT (0.3-10 keV) X-ray instrument count rates and the UVOT (1700-8000 Angstroms) filter photometry. Also included in the analysis are the publicly available pointed observations of 10 additional novae the X-ray archives. This is the largest X-ray sample of Galactic/Magellanic Cloud novae yet assembled and consists of 26 novae with super soft X-ray emission, 19 from Swift observations. The data set shows that the faster novae have an early hard X-ray phase that is usually missing in slower novae. The Super Soft X-ray phase occurs earlier and does not last as long in fast novae compared to slower novae. All the Swift novae with sufficient observations show that novae are highly variable with rapid variability and different periodicities. In the majority of cases, nuclear burning ceases less than 3 years after the outburst begins. Previous relationships, such as the nuclear burning duration vs. t_2 or the expansion velocity of the eject and nuclear burning duration vs. the orbital period, are shown to be poorly correlated with the full sample indicating that additional factors beyond the white dwarf mass and binary separation play important roles in the evolution of a nova outburst. Finally, we confirm two optical phenomena that are correlated with strong, soft X-ray emission which can be used to further increase the efficiency of X-ray campaigns.
Highlights
Novae occur in binary systems in which a Roche lobe filling secondary is losing hydrogen-rich material through the inner Lagrangian point onto a white dwarf (WD) primary
Into the interstellar medium (ISM), a mixture of material accreted from the companion star, highly processed material from the underlying WD, and products of nucleosynthesis occurring during the thermonuclear runaway (TNR)
The lower limit is set by Strope et al (2010), who find that 93 well-sampled American Association of Variable Star Observers (AAVSO) novae have the large dip in their visual light curves indicative of strong dust formation
Summary
Novae occur in binary systems in which a Roche lobe filling secondary is losing hydrogen-rich material through the inner Lagrangian point onto a white dwarf (WD) primary. The decay of 22Na (half-life 2.6 years) generates a 1275 keV emission line but only >1.25 M WDs are predicted to produce sufficient 22Na during the TNR This line has not yet been definitively detected by satellites (Hernanz 2008) but there is a recent claim by Suzuki & Shigeyama (2010) that their models with Compton decay of 22Na can account for the hard X-ray flux in V2491 Cyg provided an exceptionally large amount of 22Na, 3 × 10−5 M , was synthesized. We present a summary of all the Galactic/Magellanic Cloud Swift nova observations from launch (2004 November 20) to 2010 July 31 using the XRT (0.3–10 keV) X-ray instrument (count rates and hardness ratios) and the available UVOT (1700–8000 Å) filter photometry.
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