A&A 459, 21-30 (2006)
DOI: 10.1051/0004-6361:20066055

Unveiling the nature of INTEGRAL objects through optical spectroscopy

V. Identification and properties of 21 southern hard X-ray sources

N. Masetti¹, L. Morelli², E. Palazzi¹, G. Galaz², L. Bassani¹, A. Bazzano³, A. J. Bird⁴, A. J. Dean⁴, G. L. Israel⁵, R. Landi¹, A. Malizia¹, D. Minniti², F. Schiavone¹, J. B. Stephen¹, P. Ubertini³ and R. Walter<sup>6

1</sup>  INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, Via Gobetti 101, 40129 Bologna, Italy (formerly IASF/CNR, Bologna)
    e-mail: masetti@iasfbo.inaf.it
²  Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
³  INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica di Roma, Via Fosso del Cavaliere 100, 00133 Rome, Italy (formerly IASF/CNR, Rome)
⁴  School of Physics & Astronomy, University of Southampton, Southampton, Hampshire, SO17 1BJ, UK
⁵  INAF - Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone, Italy
⁶  INTEGRAL Science Data Centre, Chemin d'Ecogia 16, 1290 Versoix, Switzerland

(Received 17 July 2006 / Accepted 2 August 2006 )

Abstract
Optical spectroscopic identification of the nature of 21 unidentified southern hard X-ray objects is reported here in the framework of our campaign aimed at determining the nature of newly-discovered and/or unidentified sources detected by INTEGRAL. Our results show that 5 of these objects are magnetic Cataclysmic Variables (CVs), 4 are High-Mass X-ray Binaries (HMXBs; one of which is in the Large Magellanic Cloud) and 12 are Active Galactic Nuclei (AGNs). When feasible, the main physical parameters for these hard X-ray sources are also computed using the multiwavelength information available in the literature. These identifications further underscore the importance of INTEGRAL in the study of the hard X-ray spectrum of AGNs, HMXBs and CVs, and the usefulness of a strategy of catalogues cross-correlation plus optical spectroscopy to securely pinpoint the actual nature of the X-ray sources detected with INTEGRAL.

Key words: galaxies: Seyfert -- stars: novae, cataclysmic variables -- X-rays: binaries -- techniques: spectroscopic -- X-rays: general

© ESO 2006

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

• If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
• You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
• You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.