Issue |
A&A
Volume 496, Number 2, March III 2009
|
|
---|---|---|
Page(s) | 333 - 342 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361/200811091 | |
Published online | 09 February 2009 |
The new intermediate long-bursting source XTE J1701-407
1
CEA Saclay, DSM/IRFU/Service d'Astrophysique (CNRS FRE 2591), 91191 Gif-sur-Yvette, France e-mail: mfalanga@cea.fr
2
AIM - Unité Mixte de Recherche CEA - CNRS - Université Paris 7, Paris, France
3
Physics Department, McGill University, 3600 rue University, Montreal QC, H3A 2T8, Canada
4
INAF - Osservatorio Astronomico di Roma, Via Frascati 33, 00044 Rome, Italy
5
Dipartimento di Fisica - Universitá di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Rome, Italy
6
National Space Institute, Technical University of Denmark, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
Received:
6
October
2008
Accepted:
17
December
2008
Aims. XTE J1701-407 is a newly discovered X-ray transient source. We investigate its flux variability and study the intermediate long- and short-bursts discovered by Swift on July 17, and 27, 2008, respectively.
Methods. Only one intermediate long-burst, of duration ≈18 min and ten days later a short burst, have been recorded from XTE J1701-407. We analyzed the public available data from Swift and RXTE, and compared the observed properties of the intermediate long-burst with theoretical ignition condition and light curves to investigate the possible nuclear-burning processes.
Results. The intermediate long-burst may have exhibited a photospheric radius expansion,
allowing us to derive the source distance at 6.2 kpc, assuming the
empirically derived Eddington luminosity for pure helium.
The intermediate long-burst decay was described most accurately by using two exponential
functions with e-folding times of = 40±3 s and
= 221±9 s.
The bursts occurred at a persistent luminosity of
= 8.3
1036 erg s-1 (≈2.2% of the Eddington
luminosity).
For the intermediate long-burst, the mass accretion rate per unit area
onto the neutron star was
≈4
103 g cm-2 s-1, and the total energy
released was Eburst≈3.5
1040 erg. This corresponds
to an ignition column depth of yign≈1.8
109 g cm-2,
for a pure helium burning. We find that the energetics of this burst
can be modeled in different
ways, as (i) pure helium ignition, as the result of either pure helium
accretion or depletion of hydrogen by steady burning during
accumulation; or (ii) as ignition of a thick layer of hydrogen-rich
material in a source of low metallicity. However, comparison of the
burst duration with model light curves suggests that hydrogen burning
plays an important role during the burst, and therefore that this source is a low
accretion-rate burster with a low metallicity in the accreted
material.
Key words: stars: binaries: close / stars: individual: XTE J1701-407 / stars: neutron / X-rays: bursts
© ESO, 2009
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