Bibcode
Linares, M.; Chakrabarty, D.; van der Klis, M.
Referencia bibliográfica
The Astrophysical Journal Letters, Volume 733, Issue 2, article id. L17 (2011).
Fecha de publicación:
6
2011
Número de citas
25
Número de citas referidas
21
Descripción
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.