Examinando por Autor "Malizia, A."
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Ítem Evolution of MAXI J1631–479 during the January 2019 outburst observed by INTEGRAL/IBIS(Oxford University Press, 2020-01) Fiocchi, M.; Onori, F.; Bazzano, A.; Bird, A.J; . Bodaghee, A.; Charles, P.A; Lepingwell, V.A; Malizia, A.; Masetti, N.; Natalucci; Natalucci, L.; Ubertini, P.We report on a recent bright outburst from the new X-ray binary transient MAXI J1631– 479, observed in January 2019. In particular, we present the 30–200 keV analysis of spectral transitions observed with INTEGRAL/IBIS during its Galactic plane monitoring program. In the MAXI and BAT monitoring period, we observed two different spectral transitions between the high/soft and low/hard states. The INTEGRAL spectrum from data taken soon before the second transition is best described by a Comptonized thermal component with a temperature of kTe ∼ 30 keV and a high-luminosity value of L2−200 keV ∼ 3 × 1038 erg−1 (assuming a distance of 8 kpc). During the second transition, the source shows a hard, power-law spectrum. The lack of high energy cut-off indicates that the hard X-ray spectrum from MAXI J1631–479 is due to a non-thermal emission. Inverse Compton scattering of soft X-ray photons from a non-thermal or hybrid thermal/non-thermal electron distribution can explain the observed X-ray spectrum although a contribution to the hard X-ray emission from a jet cannot be determined at this stage. The outburst evolution in the hardness-intensity diagram, the spectral characteristics, and the rise and decay times of the outburst are suggesting that this system is a black hole candidateÍtem Restarting activity in the nucleus of PBC J2333.9-2343 An extreme case of jet realignment(EDP Sciences, 2017-07) Hernández-García, L.; Panessa, F.; Giroletti, M.; Ghisellini, G.; Bassani, L.; Masetti, N.; Pović, M.; Bazzano, A.; Ubertini, P.; Malizia, A.; Chavushyan, V.Context. The giant radio galaxy PBC J2333.9-2343 shows different characteristics at different wavebands that are difficult to explain within the actual generic schemes of unification of active galactic nuclei (AGN). It is therefore a good candidate host for different phases of nuclear activity. Aims. We aim at disentangling the nature of this AGN by using simultaneous multiwavelength data. Methods. We obtained data in 2015 from the Very Long Baseline Array (VLBA), the San Pedro Mártir telescope, and the XMM-Newton observatories. This allows the study of the nuclear parts of the galaxy through its morphology and spectra and the analysis of the spectral energy distribution (SED). We also reanalysed previously-presented optical data from the San Pedro Mártir telescope from 2009 to provide a homogeneous comparison. Results. At X-ray frequencies the source is unabsorbed. The optical spectra are of a type 1.9 AGN, both in 2009 and 2015, although showing a broader component in 2015. The VLBA radio images show an inverted spectrum with a self-absorbed, optically thick compact core (αc = 0.40, where Sν ∝ ν+ α) and a steep-spectrum, optically thin jet (αj,8−15 = −0.5). The SED resembles that of typical blazars and is best represented by an external Compton (EC) model with a viewing angle of approximately 3–6°. The apparent size of the large-scale structure of PBC J2333.9-2343 must correspond to an intrinsic deprojected value of approximately 7 Mpc for θv < 10°, and to >13 Mpc for θv < 5°, a value much larger than the biggest giant radio galaxy known, which is 4.5 Mpc. Conclusions. The above arguments suggest that PBC J2333.9-2343 has undergone a new episode of nuclear activity and that the direction of the new jet has changed in the plane of the sky and is now pointing towards us. This changes this source from a radio galaxy to a blazar, a very exceptional case of restarting activity.Ítem 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.Ítem 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.Ítem Variable broad lines and outflow in the weak blazar PBC J2333.9-2343(Oxford University Press, 2018-08) Hernández-García, L.; Vietri, G.; Panessa, F.; Piconcelli, E.; Chavushyan, V.; Jiménez-Andrade, E.F.; Bassani, L.; Bazzano, A.; Cazzoli, S.; Malizia, A.; Masetti, N.; Monaco, L.; Pović, M.; Saviane, I.; Ubertini, P.PBC J2333.9-2343 is a peculiar active nucleus with two giant radio lobes and a weak blazarlike nucleus at their centre. In this work we show new optical, ultraviolet (UV), and X-ray data taken from the San Pedro Mártir telescope, the New Technology Telescope, NTT/EFOSC2, and the Swift/XRT satellite. The source is highly variable at all frequencies, in particular the strongest variations are found in the broad Hα component with a flux increase of 61±4 per cent between 2009 and 2016, following the X-ray flux increase of 62±6 per cent between 2010 and 2016. We also detected a broad Hβ component in 2016, making the optical classification change from type 1.9 to type 1.8 in 1 yr. We have also detected a broad component of the [OIII]λ5007 line, which is blue-shifted and of high velocity, suggesting an origin from a highly disturbed medium, possibly an outflow. The line flux variability and broad widths are indicative of a jet that is, at least in part, responsible for the ionization of the broad line region (BLR) and narrow line region (NLR). © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.