Volume 495, Number 1, February III 2009
|Page(s)||121 - 135|
|Published online||22 December 2008|
Unveiling the nature of INTEGRAL objects through optical spectroscopy*
VII. Identification of 20 Galactic and extragalactic hard X-ray sources
INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, 40129 Bologna, Italy e-mail: email@example.com
2 Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
3 Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado Postal 70-264, 04510 México D.F., México
4 Dipartimento di Astronomia, Università di Padova, Vicolo dell'Osservatorio 3, 35122 Padua, Italy
5 Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51-216, 72000 Puebla, México
6 European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
7 School of Physics & Astronomy, University of Southampton, Southampton, Hampshire, SO17 1BJ, UK
8 INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Roma, via Fosso del Cavaliere 100, 00133 Rome, Italy
9 Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
10 NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
11 Specola Vaticana, 00120 Città del Vaticano
Accepted: 19 November 2008
Within the framework of our program of assessment of the nature of unidentified or poorly known INTEGRAL sources, we present here spectroscopy of optical objects, selected through positional cross-correlation with soft X-ray detections (afforded with satellites such as Swift, ROSAT, Chandra and/or XMM-Newton) as putative counterparts of hard X-ray sources detected with the IBIS instrument onboard INTEGRAL. Using 6 telescopes of various sizes and archival data from two on-line spectroscopic surveys we are able to identify, either for the first time or independent of other groups, the nature of 20 INTEGRAL hard X-ray sources. Our results indicate that: 11 of these objects are active galactic nuclei (AGNs) at redshifts between 0.014 and 0.978, 7 of which display broad emission lines, 2 show narrow emission lines only, and 2 have unremarkable or no emission lines (thus are likely Compton thick AGNs); 5 are cataclysmic variables (CVs), 4 of which are (possibly magnetic) dwarf novae and one is a symbiotic star; and 4 are Galactic X-ray binaries (3 with high-mass companions and one with a low-mass secondary). It is thus again found that the majority of these sources are AGNs or magnetic CVs, confirming our previous findings. When possible, the main physical parameters for these hard X-ray sources are also computed using the multiwavelength information available in the literature. These identifications support the importance of INTEGRAL in the study of the hard X-ray spectrum of all classes of X-ray emitting objects, and the effectiveness of a strategy of multi-catalogue cross-correlation plus optical spectroscopy to securely pinpoint the actual nature of unidentified hard X-ray sources.
Key words: galaxies: Seyfert / quasars: emission lines / X-rays: binaries / stars: novae, cataclysmic variables / techniques: spectroscopic / X-rays: general
Based on observations collected at the following observatories: Cerro Tololo Interamerican Observatory (Chile); Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (Canary Islands, Spain); ESO (La Silla, Chile) under programme 079.A-0171(A); Astronomical Observatory of Bologna in Loiano (Italy); Observatorio Astronómico Nacional (San Pedro Mártir, México); Anglo-Australian Observatory (Siding Spring, Australia); Apache Point Observatory (New Mexico, USA).
© ESO, 2009
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.