A5012541907- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Radio Astronomy Observations and Technology
- Pulsars and Gravitational Waves Research
- Astronomical Observations and Instrumentation
- Particle Detector Development and Performance
- Stellar, planetary, and galactic studies
- History and Developments in Astronomy
- Particle Accelerators and Free-Electron Lasers
- Astrophysics and Star Formation Studies
- Adaptive optics and wavefront sensing
- Nuclear Physics and Applications
- Advanced X-ray Imaging Techniques
- Geophysics and Gravity Measurements
- Cosmology and Gravitation Theories
- Medical Imaging Techniques and Applications
- Advanced X-ray and CT Imaging
- X-ray Spectroscopy and Fluorescence Analysis
- Computational Physics and Python Applications
- Relativity and Gravitational Theory
- Radio Wave Propagation Studies
- Neutrino Physics Research
Institute for Space Astrophysics and Planetology
2015-2024
Osservatorio Astronomico di Cagliari
2011-2023
Istituto Nazionale di Fisica Nucleare, Sezione di Cagliari
2023
University of Cagliari
2023
University College Cork
2023
National Institute for Astrophysics
2012-2021
University of Amsterdam
2020
Astronomical Observatory of Rome
2020
University of Alaska Anchorage
2018
Providence College
2018
Abstract The Laser Interferometer Space Antenna (LISA) will be a transformative experiment for gravitational wave astronomy, and, as such, it offer unique opportunities to address many key astrophysical questions in completely novel way. synergy with ground-based and space-born instruments the electromagnetic domain, by enabling multi-messenger observations, add further discovery potential of LISA. next decade is crucial prepare community LISA’s first observations. This review outlines...
We report on INTEGRAL observations of the soft $\gamma$-ray repeater SGR 1935+2154 performed between 2020 April 28 and May 3. Several short bursts with fluence $\sim10^{-7}-10^{-6}$ erg cm$^{-2}$ were detected by IBIS instrument in 20-200 keV range. The burst hardest spectrum, discovered localized real time Burst Alert System, was spatially temporally coincident a very bright radio CHIME STARE2 telescopes at 400-800 MHz 1.4 GHz, respectively. Its lightcurve shows three narrow peaks separated...
Abstract We present multifrequency (5–345 GHz) and multiresolution radio observations of 1ES 1927+654, widely considered one the most unusual extreme changing-look active galactic nuclei (CL-AGNs). The source was first designated a CL-AGN after an optical outburst in late 2017 has since displayed considerable changes X-ray emission, including destruction rebuilding corona 2019–2020. Radio prior to 2023 show faint compact typical radio-quiet AGN. Starting February, 1927+654 began exhibiting...
We investigate the relation between X-ray nuclear emission, optical emission line luminosities and black hole masses for a sample of 47 Seyfert galaxies. The sample, which has been selected from Palomar spectroscopic survey nearby galaxies (Ho et al. 1997a, ApJS, 112, 315), covers wide range powers, ~ 1043 erg/s down to very low ( 1038 erg/s). Best available data Chandra, XMM-Newton and, in few cases, ASCA observations have considered. Thanks good spatial resolution these proper modeling...
Results obtained from an X-ray spectral survey of nearby Seyfert galaxies using XMM–Newton are reported. The sample was optically selected, well defined, complete in B magnitude, and distance limited: it consists the nearest ( Mpc) 27 (9 type 1, 18 2) taken Ho et al. (1997a, ApJS, 112, 315) sample. This is one largest atlases hard spectra low-luminosity active ever assembled. All nuclear sources except two 2s detected between 2 10 keV, half for first time ever, average all them. Nuclear...
We present the first data release of high-resolution ($\leq0.2$ arcsec) 1.5-GHz radio images 103 nearby galaxies from Palomar sample, observed with eMERLIN array, as part LeMMINGs survey. This sample includes which are active (LINER and Seyfert) quiescent (HII Absorption line galaxies, ALG), reclassified based upon revised emission-line diagrams. detect emission $\gtrsim$ 0.2 mJy for 47/103 (22/34 LINERS, 4/4 Seyferts, 16/51 HII 5/14 ALGs) sizes typically $\lesssim$100 pc. identify core...
Abstract We present results from a high-cadence multiwavelength observational campaign of the enigmatic changing-look active galactic nucleus 1ES 1927+654 2022 May to 2024 April, coincident with an unprecedented radio flare (an increase in flux by factor ∼60 over few months) and emergence spatially resolved jet at 0.1–0.3 pc scales. Companion work has also detected recurrent quasi-periodic oscillation (QPO) 2–10 keV band increasing frequency (1–2 mHz) same period. During this time, soft...
We present a sample of 17 type 2 Seyfert galaxies which have an X-ray column density lower than 1022 cm-2. The Compton thin nature these sources is strongly suggested by isotropic indicators. estimate the fraction to be in range 10%–30% population galaxies. Furthermore, this appears increase progressively at luminosities. simple formulation Unified Model for not applicable such since pc-scale molecular torus likely responsible low observed; instead absorption observed originate larger...
In this Letter, we report on dual-frequency European VLBI Network observations of the faintest and least luminous radio cores in Seyfert nuclei, going to sub-millijansky flux densities luminosities around 1019 W Hz−1. We detect emission from nuclear region four galaxies (NGC 4051, NGC 4388, 4501, 5033), while one 5273) is undetected at level ∼100 μJy. The detected compact nuclei have rather different properties: spectral indices range steep (α>0.7) slightly inverted (α = −0.1), brightness...
We present the results of correlation between nuclear 2–10 keV X-ray and radio (at 2 cm, 6 20 cm) luminosities for a well-defined sample local Seyfert galaxies. use low luminosity galaxies (LLRGs) comparison. In both LLRG samples, are significantly correlated over 8 orders magnitude, indicating that emission sources strongly coupled. Moreover, samples show similar regression slope, LX , but three magnitude less luminous in band than LLRGs. This suggests either physical mechanisms responsible...
Winds outflowing from active galactic nuclei (AGNs) may carry significant amounts of mass and energy out to their host galaxies. In this paper we report the detection a sub-relativistic outflow observed in narrow line Seyfert 1 galaxy IRAS 17020+4544 as series absorption lines corresponding at least five components with an unprecedented wide range associated column densities ionization levels velocities 23,000–33,000 km s−1, detected X-ray high spectral resolution (E/ΔE ∼ 1000) ESA's...
We present the results of a multiwavelength campaign FRB 20201124A, third closest repeating fast radio burst recently localized in nearby (z=0.0978) galaxy. Deep VLA observations led to detection quiescent emission, also marginally visible X-rays with Chandra. Imaging at 22 GHz allowed us resolve source on scale $\gtrsim$ 1 arcsec and locate it position FRB, within an error 0.2 arcsec. EVN e-MERLIN sampled small angular scales, from 2 100 mas, providing tight upper limits presence compact...
The nearby type-II AGN 1ES1927+654 went through a violent changing-look (CL) event beginning December 2017 during which the optical and UV fluxes increased by four magnitudes over few months, broad emission lines newly appeared in optical/UV. By July 2018 X-ray coronal had completely vanished, only to reappear months later. In this work we report evolution of radio, optical, X-rays from pre-flare state mid-2021 with new archival data Very Long Baseline Array (VLBA), European VLBI Network,...
Using 8 telescopes in the northern and southern hemispheres, plus archival data from two on-line sky surveys, we performed a systematic optical spectroscopic study of 39 putative counterparts unidentified or poorly studied INTEGRAL sources order to determine at least better assess their nature. This was implemented within framework our campaign reveal nature newly-discovered and/or detected by INTEGRAL. Our results show that 29 these objects are active galactic nuclei (13 which Seyfert 1...
We study the NH distribution in a complete sample of 88 AGN selected 20-40 keV band from INTEGRAL/IBIS observations. find that fraction absorbed (NH > 10^{22} cm^2) sources is 43% while Compton thick comprise 7% sample. While these estimates are fully compatible with previous soft gamma-ray surveys, they would appear to be contrast results reported by Risaliti et al. (1999) using an optically This apparent difference can explained as being due selection bias caused reduction high energy flux...
We present a census of sub-pc scale properties the very long baseline interferometry (VLBI) cores in complete sample local Seyfert galaxies. Out 23 sources with Very Large Array (VLA) detection, 17 are detected also VLBI at 1.7 GHz and/or 5 GHz, an average monochromatic radio luminosity log[P5 GHz/W Hz−1] = 19.4. Radio heterogeneous nature, majority them showing elongated structures or accompanied by extra components, broad ranges brightness temperatures (105–1010 K) and spectral indices...
In this paper we report on the broad-band X-ray properties of a complete sample absorbed Seyfert galaxies hard selected with INTEGRAL. Our is composed 33 sources, which 15 are newly discovered active galactic nuclei (AGN) above 20 keV (IGR sources), while 18 already known type 2 AGN ('known'). For 17 sources (15 IGR + 'known' sources) have performed analysis using both XMM–Newton, and INTEGRAL-IBIS data. To full view then complemented 16 remaining existing studies in same range. The...
We report on simultaneous optical and X-ray observations of the Seyfert galaxy, NGC 3147. The XMM–Newton spectrum shows that source is unabsorbed in X-rays (NH < 5 × 1020 cm−2). On other hand, no broad lines are present spectrum. origin this optical/X-rays misclassification (with respect to Unification Model) cannot be attributed variability, since two bands simultaneous. Moreover, a Compton-thick nature object can rejected basis low-equivalent width iron Kα line (≃130 eV) large ratio...
Narrow-line Seyfert 1 (NLS1) galaxies are very interesting objects which display peculiar properties when compared to their broad-line analogues (BLS1). Although well studied in many wavebands, behaviour at >10 keV is poorly and yet important discriminate between models invoked explain the complexity observed X-ray band. Here, we present for first time high-energy observations (17–100 keV) of five NLS1 (three bona fide two candidates) detected by INTEGRAL/Imager on Board INTEGRAL Satellite...
We have observed the hard X-ray selected Narrow-Line Seyfert 1 galaxy SWIFT J2127.4+5654 with Suzaku. report detection of a broad relativistic iron emission line from inner accretion disc. By assuming that edge disc corresponds to innermost stable circular orbit black hole spacetime, profile enables us measure spin a= 0.6\pm0.2. However, non-rotating Schwarzschild spacetime is excluded at just above 3 sigma level, while maximally spinning Kerr ~5 level. The intermediate we may indicate...
In this paper we discuss the broad-band X-ray characteristics of a complete sample 36 type 1 active galactic nuclei (AGN), detected by INTEGRAL in 20–40 keV band above 5.5σ level. We present, for all objects sample, (1–110 keV) spectral analysis obtained using INTEGRAL/Swift/Burst Alert Telescope observations together with XMM–Newton, Chandra, ASCA and Swift/X-Ray data. also present general average properties i.e. distribution photon indices, high-energy cut-offs, reflection fractions...