Examinando por Autor "Landi, R."

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    The nature of 50 Palermo Swift -BAT hard X-ray objects through optical spectroscopy
    (EDP Sciences, 2017-06) Rojas, A.F.; Masetti, N.; Minniti, D.; Jiménez-Bailón, E.; Chavushyan, V.; Hau, G.; McBride, V.A.; Bassani, L.; Bazzano, A.; Bird, A.J.; Galaz, G.l.; Gavignaud, I.; Landi, R.; Malizia, A.; Morelli, L.; Palazzi, E.; Patiño-Álvarez, V.; Stephen, J.B.; Ubertini, P.
    We present the nature of 50 hard X-ray emitting objects unveiled through an optical spectroscopy campaign performed at seven telescopes in the northern and southern hemispheres. These objects were detected with the Burst Alert Telescope (BAT) instrument onboard the Swift satellite and listed as of unidentified nature in the 54-month Palermo BAT catalogue. In detail, 45 sources in our sample are identified as active galactic nuclei of which, 27 are classified as type 1 (with broad and narrow emission lines) and 18 are classified as type 2 (with only narrow emission lines). Among the broad-line emission objects, one is a type 1 high-redshift quasi-stellar object, and among the narrow-line emission objects, one is a starburst galaxy, one is a X-ray bright optically normal galaxy, and one is a low ionization nuclear emission line region. We report 30 new redshift measurements, 13 confirmations and 2 more accurate redshift values. The remaining five objects are galactic sources: three are Cataclismic Variables, one is a X-ray Binary probably with a low mass secondary star, and one is an active star.
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    Update of the INTEGRAL/IBIS active galactic nuclei catalogue: Deeper on the Galactic plane and wider beyond
    (EDP Sciences, 2023-03) Malizia, A.; Bassani, L.; Landi, R.; Molina, M.; Masetti, N.; Palazzi, E.; Bruni, G.; Bazzano, A.; Ubertini, P.; Bird, A.J.
    In this work we have updated the list of active galactic nuclei (AGN) detected by INTEGRAL taking into account the new objects listed in the last published INTEGRAL/IBIS survey. We have collected 83 new AGN, increasing the number of INTEGRAL-detected active galaxies (436) by 19%. Half of these new additions are located behind the Galactic plane, and for most of them we have full X-ray coverage, obtained through archival data from Swift/XRT, XMM-Newton, and NuSTAR. The soft X-ray data allowed us to associate each high-energy emitter with a single or multiple X-ray counterpart(s) and characterise the spectral shape of these new AGN by estimating the photon index, the intrinsic absorption, and the 2-10 keV flux. A few cases where two soft X-ray counterparts fall within the INTEGRAL error circle and at least one is classified as an AGN have been found and discussed in detail. Thirty-four sources originally listed as AGN candidates or unidentified objects have been recognised as AGN by employing three diagnostic tests: WISE colours, radio emission, and morphology. For 12 sources among the 34 AGN candidates, we reduced the optical spectra and confirmed their AGN nature, providing also their optical class and redshift. This paper is part of an ongoing effort to keep the INTEGRAL AGN catalogue updated in order to provide the scientific community with a hard X-ray selected sample of well-classified and spectrally characterised active galaxies. © 2023 The Authors.