Bibcode
Linares, Manuel; Chakrabarty, D.; van der Klis, M.
Bibliographical reference
American Astronomical Society, AAS Meeting #218, #320.06; Bulletin of the American Astronomical Society, Vol. 43, 2011
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5
2011
Citations
0
Refereed citations
0
Description
The neutron star transient and 11 Hz X-ray pulsar IGR J17480-2446,
recently discovered in the globular cluster Terzan 5, showed
unprecedented bursting activity during its 2010 October-November
outburst. We analyzed all X-ray bursts detected with the Rossi X-ray
Timing Explorer and find strong evidence that they all have a
thermonuclear origin, despite the fact that many do not show the
canonical spectral softening along the decay imprinted on type I X-ray
bursts by the cooling of the neutron star photosphere. We show that the
persistent-to-burst power ratio is fully consistent with the
accretion-to-thermonuclear efficiency ratio along the whole outburst, as
is typical for type I X-ray bursts. The burst energy, peak luminosity
and daily-averaged spectral profiles all evolve smoothly throughout the
outburst, in parallel with the persistent (non-burst) luminosity. We
also find that the peak burst to persistent luminosity ratio determines
whether or not cooling is present in the bursts from IGR J17480-2446,
and argue that the apparent lack of cooling is due to the
``non-cooling'' bursts having both a lower peak temperature and a higher
non-burst (persistent) emission. We conclude that the detection of
cooling along the decay is a sufficient, but not a necessary condition
to identify an X-ray burst as thermonuclear. Finally, we compare these
findings with X-ray bursts from other rapidly accreting neutron stars.