On the Cooling Tails of Thermonuclear X-ray Bursts: The IGR J17480-2446 Link

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 eviden...

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Bibliographic Details
Main Authors: Linares, Manuel Alegret (Contributor), Chakrabarty, Deepto (Contributor), Van Der Klis, M. (Author)
Other Authors: Massachusetts Institute of Technology. Department of Physics (Contributor), MIT Kavli Institute for Astrophysics and Space Research (Contributor)
Format: Article
Language:English
Published: Institute of Physics Publishing, 2012-04-13T15:19:23Z.
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Online Access:Get fulltext
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100 1 0 |a Linares, Manuel Alegret  |e author 
100 1 0 |a Massachusetts Institute of Technology. Department of Physics  |e contributor 
100 1 0 |a MIT Kavli Institute for Astrophysics and Space Research  |e contributor 
100 1 0 |a Chakrabarty, Deepto  |e contributor 
100 1 0 |a Chakrabarty, Deepto  |e contributor 
100 1 0 |a Linares, Manuel Alegret  |e contributor 
700 1 0 |a Chakrabarty, Deepto  |e author 
700 1 0 |a Van Der Klis, M.  |e author 
245 0 0 |a On the Cooling Tails of Thermonuclear X-ray Bursts: The IGR J17480-2446 Link 
260 |b Institute of Physics Publishing,   |c 2012-04-13T15:19:23Z. 
856 |z Get fulltext  |u http://hdl.handle.net/1721.1/70013 
520 |a 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. 
520 |a Netherlands Organization for Scientific Research ((NWO) Rubicon Fellowship) 
546 |a en_US 
655 7 |a Article 
773 |t Astrophysical Journal. Letters