X-ray flashes in recurrent novae: M31N 2008-12A and the implications of the Swift nondetection

Journal Article · Mon Oct 10 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/830/1/40· OSTI ID:22868608

Kato, Mariko ^[1]; Saio, Hideyuki ^[2]; Henze, Martin; Hernanz, Margarita ^[3]; Ness, Jan-Uwe ^[4]; Osborne, Julian P.; Page, Kim L. ^[5]; Darnley, Matthew J.; Bode, Michael F. ^[6]; Shafter, Allen W. ^[7]; Gehrels, Neil ^[8]; Kennea, Jamie ^[9]; Hachisu, Izumi ^[10]

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1. Department of Astronomy, Keio University, Hiyoshi, Yokohama 223-8521 (Japan)
2. Astronomical Institute, Graduate School of Science, Tohoku University, Sendai, 980-8578 (Japan)
3. Institut de Ciències de l’Espai (CSIC-IEEC), Campus UAB, C/Can Magrans s/n, E-08193 Cerdanyola del Valles (Spain)
4. European Space Astronomy Centre, P.O. Box 78, E-28691 Villanueva de la Cañada, Madrid (Spain)
5. X-Ray and Observational Astronomy Group, Department of Physics and Astronomy, University of Leicester, LE1 7RH (United Kingdom)
6. Astrophysics Research Institute, Liverpool John Moores University, IC2 Liverpool Science Park, Liverpool, L3 5RF (United Kingdom)
7. Department of Astronomy, San Diego State University, San Diego, CA 92182 (United States)
8. Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
9. Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States)
10. Department of Earth Science and Astronomy, College of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902 (Japan)

Models of nova outbursts suggest that an X-ray flash should occur just after hydrogen ignition. However, this X-ray flash has never been observationally confirmed. We present four theoretical light curves of the X-ray flash for two very massive white dwarfs (WDs) of 1.380 and 1.385 M{sub ⊙} and for two recurrence periods of 0.5 and 1 yr. The duration of the X-ray flash is shorter for a more massive WD and for a longer recurrence period. The shortest duration of 14 hr (0.6 days) among the four cases is obtained for the 1.385 M{sub ⊙} WD with a 1 yr recurrence period. In general, a nova explosion is relatively weak for a very short recurrence period, which results in a rather slow evolution toward the optical peak. This slow timescale and the predictability of very short recurrence period novae give us a chance to observe X-ray flashes of recurrent novae. In this context, we report the first attempt, using the Swift observatory, to detect an X-ray flash of the recurrent nova M31N 2008-12a (0.5 or 1 yr recurrence period), which resulted in the nondetection of X-ray emission during the period of 8 days before the optical detection. We discuss the impact of these observations on nova outburst theory. The X-ray flash is one of the last frontiers of nova studies, and its detection is essential for understanding the pre-optical-maximum phase. We encourage further observations.

• OSTI ID: 22868608
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 830; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DETECTION
EMISSION
EXPLOSIONS
HYDROGEN
IGNITION
NOVAE
WHITE DWARF STARS