1. Periodic gamma-ray modulation of the blazar PG 1553+113 confirmed by Fermi-LAT and multiwavelength observationsS. Abdollahi, L. Baldini, G. Barbiellini, R. Bellazzini, B. Berenji, E. Bissaldi, R. D. Blandford, R. Bonino, P. Bruel, Gabrijela Zaharijas, 2024, izvirni znanstveni članek Opis: Abstract
A 2.1 yr periodic oscillation of the gamma-ray flux from the blazar PG 1553+113 has previously been tentatively identified in ∼7 yr of data from the Fermi Large Area Telescope. After 15 yr of Fermi sky-survey observations, doubling the total time range, we report >7 cycle gamma-ray modulation with an estimated significance of 4σ against stochastic red noise. Independent determinations of oscillation period and phase in the earlier and the new data are in close agreement (chance probability <0.01). Pulse timing over the full light curve is also consistent with a coherent periodicity. Multiwavelength new data from Swift X-Ray Telescope, Burst Alert Telescope, and UVOT, and from KAIT, Catalina Sky Survey, All-Sky Automated Survey for Supernovae, and Owens Valley Radio Observatory ground-based observatories as well as archival Rossi X-Ray Timing Explorer satellite-All Sky Monitor data, published optical data of Tuorla, and optical historical Harvard plates data are included in our work. Optical and radio light curves show clear correlations with the gamma-ray modulation, possibly with a nonconstant time lag for the radio flux. We interpret the gamma-ray periodicity as possibly arising from a pulsational accretion flow in a sub-parsec binary supermassive black hole system of elevated mass ratio, with orbital modulation of the supplied material and energy in the jet. Other astrophysical scenarios introduced include instabilities, disk and jet precession, rotation or nutation, and perturbations by massive stars or intermediate-mass black holes in polar orbit.
Ključne besede: gamma rays, AGNs
Objavljeno v RUNG: 13.01.2025; Ogledov: 706; Prenosov: 10
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2. A gamma-ray pulsar timing array constrains the nanohertz gravitational wave backgroundM. Ajello, W. B. Atwood, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, R. Bellazzini, A. Berretta, B. Bhattacharyya, Gabrijela Zaharijas, 2022, izvirni znanstveni članek Ključne besede: pulsar timing array, gravitational waves
Objavljeno v RUNG: 15.01.2024; Ogledov: 1926; Prenosov: 0
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3. Gamma rays from fast black-hole windsM. Ajello, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, R. Bellazzini, A. Berretta, E. Bissaldi, R. D. Blandford, E. D. Bloom, Gabrijela Zaharijas, 2021, izvirni znanstveni članek Ključne besede: active galactic nuclei, galactic winds, gamma-rays
Objavljeno v RUNG: 17.02.2022; Ogledov: 3127; Prenosov: 113
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4. Fermi Large Area Telescope fourth source catalogS. Abdollahi, Fabio Acero, M. Ajello, W. B. Atwood, M. Axelsson, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, Gabrijela Zaharijas, 2020, izvirni znanstveni članek Ključne besede: astronomy, gamma rays, sky surveys
Objavljeno v RUNG: 22.05.2020; Ogledov: 4218; Prenosov: 207
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5. The spectrum and morphology of the Fermi bubblesGabrijela Zaharijas, M. Ackermann, Adrien Albert, W. B. Atwood, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, R. Bellazzini, E. Bissaldi, R. D. Blandford, 2014, izvirni znanstveni članek Ključne besede: high energy astrophysics, gamma-rays, diffuse background
Objavljeno v RUNG: 09.05.2017; Ogledov: 5468; Prenosov: 23
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