EDP Sciences
Free access
Volume 388, Number 1, June II 2002
Page(s) 293 - 297
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20020546

A&A 388, 293-297 (2002)
DOI: 10.1051/0004-6361:20020546

The broad band X-ray spectrum of the black hole candidate GRS 1758-258

L. Sidoli and S. Mereghetti

Istituto di Astrofisica Spaziale e Fisica Cosmica - Sezione di Milano "G. Occhialini" - CNR via Bassini 15, 20133 Milano, Italy

(Received 11 February 2002 / Accepted 8 April 2002 )

We present the results of a BeppoSAX observation of the black hole candidate GRS 1758-258 carried out in 1997, while the source was in its low/hard state. The X-ray spectrum, simultaneously observed over the broad energy range from 0.1 to 200 keV, can be well described by a Comptonized emission model with electron temperature $kT_{\rm e} = 31.4 ^{+3.4} _{-2.5}$ keV and optical depth $\tau = 4.0 ^{+0.2}_{-0.3}$ (spherical geometry), although a cut-off power-law and a reflection model cannot be excluded. Additionally, a broad iron line at 6.4 keV with equivalent width EW = 67 +80 -40 eV has been marginally detected. The 0.1-200 keV luminosity is $1.4\times10^{37}$ erg s -1 for an assumed distance of 8 kpc. The soft and hard luminosities are such that the source falls inside the so-called "burster box". No evidence for a soft excess is present.

Key words: accretion, accretion disks -- stars: individual: GRS 1758-258 -- X-rays: general

Offprint request: L. Sidoli, sidoli@ifctr.mi.cnr.it

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