Issue |
A&A
Volume 469, Number 1, July I 2007
|
|
---|---|---|
Page(s) | L27 - L30 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361:20077494 | |
Published online | 10 May 2007 |
Letter to the Editor
IGR J17254-3257, a new bursting neutron star
1
Danish National Space Center, Technical University of Denmark, Juliane Maries Vej 30, 2100 Copenhagen, Denmark e-mail: jerome@spacecenter.dk
2
CEA Saclay, DSM/DAPNIA/Service d'Astrophysique (CNRS FRE 2591), 91191, Gif-sur-Yvette, France
3
Unité mixte de recherche Astroparticule et Cosmologie, 11 place Berthelot, 75005 Paris, France
4
ISOC, ESA/ESAC, Urb. Villafranca del Castillo, PO Box 50727, 28080 Madrid, Spain
5
INTEGRAL Science Data Centre, Chemin d'Écogia 16, 1290 Versoix, Switzerland
6
Observatoire de Genève, Université de Genève, 51 ch. des Maillettes, 1290 Sauverny, Switzerland
7
Kavli Institute for Theoretical Physics, Kohn Hall, University of California, Santa Barbara, CA 93106, USA
8
Science Payload and Advance Concepts Office, ESA-ESTEC, Postbus 299, 2200 AG, Noordwijk, The Netherlands
Received:
16
March
2007
Accepted:
3
May
2007
Aims.The study of the observational properties of uncommonly long bursts from low luminosity sources is important when investigating the transition from a hydrogen - rich bursting regime to a pure helium regime and from helium burning to carbon burning as predicted by current burst theories. On a few occasions X-ray bursts have been observed with extended decay times up to several tens of minutes, intermediate between usual type I X-ray bursts and so-called superbursts.
Methods.IGR J17254-3257 is a recently discovered X-ray burster of which only two bursts have been recorded: an ordinary short type I X-ray burst, and a 15 min long burst. The properties of the X-ray bursts observed from IGR J17254-3257 are investigated. The broad-band spectrum of the persistent emission in the 0.3–100 keV energy band is studied using contemporaneous INTEGRAL and XMM-Newton data.
Results.A refined position of IGR J17254-3257 is given and an upper limit to its distance is estimated to about 14.5 kpc. The persistent bolometric flux of 1.110-10 erg cm-2 s-1 corresponds, at the canonical distance of 8 kpc, to 8.41035 erg s-1 between 0.1–100 keV, which translates to a mean accretion rate of about 710-11 yr-1.
Conclusions.The low X-ray persistent luminosity of IGR J17254-3257 seems to indicate the source may be in a state of low accretion rate usually associated with a hard spectrum in the X-ray range. The nuclear burning regime may be intermediate between pure He and mixed H/He burning. The long burst is the result of the accumulation of a thick He layer, while the short one is a prematurate H-triggered He burning burst at a slightly lower accretion rate.
Key words: binaries: close / stars: individual: IGR J17254-3257 (1RXS J172525.5-325717) / stars: neutron / X-rays: bursts
© ESO, 2007
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.