A look with BeppoSAX at the low-luminosity Galactic X-ray source 4U 2206+54

¹ Istituto di Astrofisica Spaziale e Fisica Cosmica – Sezione di Bologna, CNR, via Gobetti 101, 40129 Bologna, Italy e-mail: masetti@bo.iasf.cnr.it
² Istituto Tecnologie e Studio sulla Radiazione Extraterrestre, CNR, via Gobetti 101, 40129 Bologna, Italy
³ Istituto di Astrofisica Spaziale e Fisica Cosmica – Sezione di Palermo, CNR, via La Malfa 153, 90146 Palermo, Italy
⁴ Dipartimento di Fisica, Università di Ferrara, via Paradiso 12, 44100 Ferrara, Italy

Received: 16 February 2004
Accepted: 16 April 2004

Abstract

A pointed observation of the low-luminosity galactic source 4U 2206+54 was carried out in November 1998 with BeppoSAX. The light curve of 4U 2206+54 shows erratic variability on a timescale of ~1 h; neither hardness variations nor time periodicities are detected throughout this 67 ks long observation. Thanks to the wide spectral coverage capabilities of BeppoSAX we could observe the source X-ray continuum over three energy decades, from 0.6 to 60 keV. The spectrum could be equally well fitted either with a blackbody plus Comptonization or with a high energy cutoff power law. No iron emission around 6.5 keV was detected, while a tentative detection of a cyclotron resonant feature in absorption is presented. Comparison of the present BeppoSAX data with the information available in the literature for this source suggests that 4U 2206+54 is a close binary system in which a (possibly magnetized) NS is accreting from the companion star wind.