Mkn 463 field observed by BeppoSAX

In this work we present the observation of the Mkn 463 field performed with the MECS instrument on-board BeppoSAX in the 1.8-10.5 keV band. The Mkn 463 field is an example of an extragalactic field crowded with absorbed X-ray sources: apart from the Seyfert 2 galaxy Mkn 463 and the well known QSO PG 1352+183 (the only object showing no absorption), two other objects are detected with a column density in excess to the galactic value. The first 1SAX J1353.9+1820 is a red QSO from the BeppoSAX High Energy Large Area Survey (HELLAS). The second 1SAX J1355.4+1815 is optically unidentified, but its X-ray spectral characteristics indicate that it too is an AGN hidden behind a large column density.Comment: 5 pages, 3 PostScript figures, LaTeX manuscript, new A&A file style included, accepted for publication on Astronomy and Astrophysic

Using X-ray catalogues to find counterparts to unassociated high-energy Fermi/LAT sources

The first Fermi Large Area Telescope (LAT) catalogue of sources (1FHL) emitting at high energies (above 10 GeV) reports the details of 514 objects detected in the first three years of the Fermi mission. Of these, 71 were reported as unidentified in the 1FHL catalogue, although six are likely to be associated with a supernova remnant (SNR), a Pulsar Wind Nebula (PWN) or a combination of both, thereby leaving a list of 65 still unassociated objects. Herein, we report a preliminary analysis on this sample of objects concentrating on nine 1FHL sources, which were found to have a clear optical extragalactic classification. They are all blazar, eight BL Lac and one flat spectrum radio quasar, typically at redshift greater than 0.1.Comment: Proceedings of "Swift: 10 Years of Discovery", December 2-5 2014, Rome, Italy, in Proceedings of Science (SWIFT 10

Swift/XRT counterparts to unassociated Fermi high-energy LAT sources

We report the results from our analysis of a large set of archival data acquired with the X-ray telescope (XRT) onboard Swift, covering the sky region surrounding objects from the first Fermi Large Area Telescope (LAT) catalogue of high-energy sources (1FHL), which still lack an association. Of the 23 regions analysed, ten did not show any evidence of X-ray emission, but 13 were characterised by the presence of one or more objects emitting in the 0.3-10 keV band. Only in a couple of cases is the X-ray counterpart located outside the Fermi positional uncertainty, while in all other cases the associations found are compatible with the high-energy error ellipses. All counterparts we found have been studied in detail by means of a multi-waveband approach to evaluate their nature or class; in most cases, we have been able to propose a likely or possible association except for one Fermi source whose nature remains doubtful at the moment. The majority of the likely associations are extragalactic in nature, most probably blazars of the BL Lac type.Comment: 13 pages, 5 figures, 4 tables. Accepted for publication in A&