Unveiling the nature of INTEGRAL objects through optical spectroscopy^⋆

X. A new multi-year, multi-observatory campaign

¹ INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, 40129 Bologna, Italy
e-mail: masetti@iasfbo.inaf.it
² INAF – Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, 00133 Rome, Italy
³ Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado Postal 70-264, 04510 México D.F., México
⁴ Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51-216, 72000 Puebla, México
⁵ South African Astronomical Observatory, PO Box 9, Observatory, 7935 Cape, South Africa
⁶ Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 Cape Town, Republic of South Africa
⁷ Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, 22 Santiago, Chile
⁸ School of Physics & Astronomy, University of Southampton, Highfield, SO17 1 BJ Southampton, UK
⁹ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁰ Specola Vaticana, 00120 Città del Vaticano
¹¹ Dipartimento di Fisica ed Astronomia “G. Galilei”, Università di Padova, vicolo dell’Osservatorio 3, 35122 Padova, Italy
¹² INAF-Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padua, Italy

Received: 6 June 2013
Accepted: 20 June 2013

Abstract

Within the framework of our program (running since 2004) of identification of hard X-ray INTEGRAL sources through optical spectroscopy, we present the results concerning the nature of 33 high-energy objects. The data were acquired with the use of six telescopes of different sizes and from one on-line archive. The results indicate that the majority of these objects (23 out of 33) are active galactic nuclei (AGNs), whereas 10 are sources in the local Universe with eight of which in the Galaxy and two in the Small Magellanic Cloud (SMC). Among the identified AGNs, 13 are of Type 1 (i.e., with broad emission lines), eight are of Type 2 (with narrow emissions only), and two are X-ray bright, optically normal galaxies with no apparent nuclear activity in the optical. Six of these AGNs lie at high redshift (z > 0.5). Concerning local objects, we found that five of them are Galactic cataclysmic variables, three are high-mass X-ray binaries (two of which lying in the SMC), one is a low-mass X-ray binary, and one is classified as a flare star that is likely of RS CVn type. The main optical properties and inferred physical characteristics of these sources are presented and discussed.