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Unusual X-ray burst profiles from 4U/MXB 1636-53During a one day Exosat observation eight X-ray bursts from 4U/MXB 1636-53 are observed. Four of these were very unusual. Their peak fluxes were relatively low, and they showed a distinct double peak in their bolometric flux profiles. These new double-peaked bursts are unexplained by presently available models of X-ray bursts. It is possible that the energy release in these bursts proceeds in two 'steps'. The burst profiles are not the result of an expansion and subsequent contraction of the photosphere of the neutron star. Thus, they are very different from previously observed bursts which do show a double peak in certain energy ranges but not in their bolometric flux profiles; these are satisfactorily explained in terms of photospheric radius expansion and contraction. The anticorrelation between the apparent blackbody radius and blackbody temperature is discussed in terms of the nonPlanckian character of burst spectra and it is concluded that the model calculations reported by London, Taam, and Howard in 1984 give a reasonable first-order description of the observed apparent radius changes in X-ray bursts.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Sztajno, M. (Max-Planck-Inst. fuer Extraterrestrische Physik Garching, Germany)
Truemper, J. (Max-Planck-Inst. fuer Extraterrestrische Physik Garching, Germany)
Pietsch, W. (Max-Planck-Institut fuer extraterrestrische Physik Garching, Germany)
Van Paradijs, J. (Max-Planck-Inst. fuer Extraterrestrische Physik Garching, Germany)
Stollman, G. (Amsterdam, Universiteit Netherlands)
Date Acquired
August 12, 2013
Publication Date
December 1, 1985
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 299
ISSN: 0004-637X
Subject Category
Funding Number(s)
Distribution Limits