Volume 545, September 2012
|Number of page(s)||14|
|Section||Catalogs and data|
|Published online||13 September 2012|
Accurate classification of 29 objects detected in the 39 month Palermo Swift/BAT hard X-ray catalogue⋆,⋆⋆
INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di
Bologna, via Gobetti
2 Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado Postal 70-264, 04510 México D.F., Mexico
3 Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51-216, 72000 Puebla, Mexico
4 INAF – Istituto di Astrofisica e Planetologia Spaziali di Roma, via del Fosso del Cavaliere 100, 00133 Roma, Italy
5 Physics & Astronomy, University of Southampton, Southampton, Hampshire, SO171 BJ, UK
6 Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
7 European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
8 Specola Vaticana, 00120 Città del Vaticano, Vatican
9 Dipartimento di Astronomia, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padua, Italy
10 South African Astronomical Observatory, PO Box 9, 7935 Observatory, South Africa
11 University of Cape Town, Private Bag X3, 7701 Rondebosch, South Africa
Accepted: 15 June 2012
Through an optical campaign performed at four telescopes located in the northern and the southern hemispheres, plus archival data from two on-line sky surveys, we obtained optical spectroscopy for 29 counterparts of unclassified or poorly studied hard X-ray emitting objects detected with Swift /Burst Alert Telescope (BAT) and listed in the 39 month Palermo catalogue. All these objects also have observations taken with Swift /X-ray Telescope (XRT) or XMM-European Photon Imaging Camera (EPIC) which not only allow us to pinpoint their optical counterpart, but also study their X-ray spectral properties (column density, power law photon index, and F2−10 keV flux). We find that 28 sources in our sample are active galactic nuclei (AGNs); 7 are classified as type 1, while 21 are of type 2; the remaining object is a Galactic cataclysmic variable. Among our type 1 AGNs, we find 5 objects of intermediate Seyfert type (1.2−1.9) and one narrow-line Seyfert 1 galaxy; for 4 out of 7 sources, we are able to estimate the central black hole mass. Three of the type 2 AGNs of our sample display optical features typical of low-ionization nuclear emission-line regions (LINER) and one is a likely Compton thick AGN. All galaxies classified in this work are relatively nearby objects since their redshifts lie in the range 0.008−0.075; the only Galactic object found lies at an estimated distance of 90 pc. We also investigate the optical versus X-ray emission ratio of the galaxies of our sample to test the AGN unified model. For these galaxies, we also compare the X-ray absorption (caused by gas) with the optical reddening (caused by dust): we find that for most of our sources, specifically those of type 1.9−2.0 the former is higher than the latter confirming early results of Maiolino and collaborators; this is possibly due to the properties of dust in the circumnuclear obscuring torus of the AGN.
Key words: atomic data / X-rays: galaxies / X-rays: binaries / novae, cataclysmic variables
Based on observations obtained from the following observatories: the Astronomical Observatory of Bologna in Loiano (Italy), ESO-La Silla Observatory (Chile) under programme 083.D-0110, Observatorio Astronómico Nacional (San Pedro Mártir, Mexico), and the South African Astronomical Observatory (South Africa).
The spectra are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (22.214.171.124) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/545/A101
© ESO, 2012
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