Swift X-ray and UV monitoring of the Classical Nova V458 Vul (Nova Vul 2007)

Abstract

We describe the highly variable X-ray and UV emission of V458 Vul (Nova Vul 2007), observed by Swift between 1 and 422 days after outburst. Initially bright only in the UV, V458 Vul became a variable hard X-ray source due to optically thin thermal emission at kT=0.64 keV with an X-ray band unabsorbed luminosity of 2.3x10^{34} erg s^{-1} during days 71-140. The X-ray spectrum at this time requires a low Fe abundance (0.2^{+0.3}_{-0.1} solar), consistent with a Suzaku measurement around the same time. On day 315 we find a new X-ray spectral component which can be described by a blackbody with temperature of kT=23^{+9}_{-5} eV, while the previous hard X-ray component has declined by a factor of 3.8. The spectrum of this soft X-ray component resembles those typically seen in the class of supersoft sources (SSS) which suggests that the nova ejecta were starting to clear and/or that the WD photosphere is shrinking to the point at which its thermal emission reaches into the X-ray band. We find a high degree of variability in the soft component with a flare rising by an order of magnitude in count rate in 0.2 days. In the following observations on days 342.4-383.6, the soft component was not seen, only to emerge again on day 397. The hard component continued to evolve, and we found an anticorrelation between the hard X-ray emission and the UV emission, yielding a Spearman rank probability of 97%. After day 397, the hard component was still present, was variable, and continued to fade at an extremely slow rate but could not be analysed owing to pile up contamination from the bright SSS component.

arXiv comment10 pages, 6 figures; accepted for AJ

References in corpus (18)

• On the Absorption of X-rays in the Interstellar Medium
• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• The Swift X-ray Telescope
• Collisional Plasma Models with APEC/APED: Emission Line Diagnostics of Hydrogen-like and Helium-like Ions
• The Swift Ultra-Violet/Optical Telescope
• Photometric Calibration of the Swift Ultraviolet/Optical Telescope
• Swift observations of the 2006 outburst of the recurrent nova RS Ophiuchi: I. Early X-ray emission from the shocked ejecta and red giant wind
• The Super-Soft X-ray Phase of Nova RS Ophiuchi 2006
• The early X-ray emission from V382 Velorum (=Nova Vel 1999): An internal shock model
• The Extraordinary X-ray Light Curve of the Classical Nova V1494 Aquilae (1999 #2) in Outburst: The Discovery of Pulsations and a "Burst"
• A planetary nebula around nova V458 Vul undergoing flash ionization
• Swift X-ray Observations of Classical Novae
• High-resolution X-ray spectroscopy of the evolving shock in the 2006 outburst of RS Ophiuchi
• The X-ray emission from Nova V382 Velorum: I. The hard component observed with BeppoSAX
• The Chandra Observation of the Shell of Nova Persei 1901 (GK Persei): Detection of localized Non-thermal X-ray Emission from a Miniature Supernova Remnant
• An X-ray emission line spectrum of Nova V382 Velorum 1999
• On the nature of the X-ray source in GK Per
• X-Ray Spectroscopy of the Classical Nova V458 Vulpeculae with Suzaku

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