SWIFT X-RAY AND ULTRAVIOLET MONITORING OF THE CLASSICAL NOVA V458 VUL (NOVA VUL 2007)
- European Space Astronomy Centre, P.O. Box 78, 28691 Villanueva de la Canada, Madrid (Spain)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom)
- BAA VSS, 5 Silver Lane, West Challow, Wantage, OX12 9TX (United Kingdom)
- Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD (United Kingdom)
- AAVSO, 5 Melba Drive, Hudson, NH 03051 (United States)
- Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)
- Department of Physics, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501 (Japan)
- School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom)
- BAA VSS, Furzehill House, Ilston, Swansea SA2 7LE (United Kingdom)
- Isaac Newton Group, PO Ap. de Correos 321, 38700 Sta. Cruz de la Palma (Spain)
- Department of Geology and Astronomy, West Chester University, West Chester, PA 19383 (United States)
- CBA Flanders, Alan Guth Observatory, Koningshofbaan 51, Hofstade, Aalst (Belgium)
- Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)
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 2.3 x 10{sup 34} erg s{sup -1} during days 71-140. The X-ray spectrum at this time requires a low Fe abundance (0.2{sup +0.3} {sub -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{sup +9} {sub -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 white dwarf 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 analyzed owing to pile-up contamination from the bright SSS component.
- OSTI ID:
- 21269199
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 137, Issue 5; Other Information: DOI: 10.1088/0004-6256/137/5/4160; Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
Similar Records
A PREDICTION FORMULA OF SUPERSOFT X-RAY PHASE OF CLASSICAL NOVAE
EVOLUTION OF THE SYMBIOTIC NOVA PU VUL-OUTBURSTING WHITE DWARF, NEBULAE, AND PULSATING RED GIANT COMPANION
Related Subjects
COSMOLOGY AND ASTRONOMY
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ABUNDANCE
COUNTING RATES
HARD COMPONENT
HARD X RADIATION
LUMINOSITY
NOVAE
PHOTON EMISSION
PHOTOSPHERE
PROBABILITY
SOFT COMPONENT
SOFT X RADIATION
ULTRAVIOLET RADIATION
WHITE DWARF STARS
X-RAY SPECTRA