Gamma-ray blazars: The view from AGILE

D’Ammando, F.; Bulgarelli, A.; Chen, Andrew; Donnarumma, I.; Giuliani, A.; Longo, F.; Pacciani, L.; Pucella, G.; Striani, E.; Tavani, M.; Vercellone, S.; Vittorini, V.; Covino, S.; Krimm, H. A.; Raiteri, C. M.; Romano, P.; Villata, M.

doi:10.1016/j.asr.2011.02.011

Cited by 7 publications

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“…We also find that the shape of the particle distribution changes between the low and the hard states, with harder slopes below γ b and steeper above. The synchrotron component, traced by the optical data, does not vary as dramatically as the inverse Compton component (MeV-GeV) in the same time scale, a behavior seen, for instance, in the blazars 3C 279 (see Wehrle et al 1998 andGiuliani et al 2009) and PKS 1454-354 (Ghisellini et al 2009), but different from that of other well monitored blazar sources like 3C 454.3 (Bonning et al 2009;Vercellone et al 2009;Donnarumma et al 2009;Vercellone et al 2010;Pacciani et al 2010) and PKS 1510-089 (Abdo et al 2010e;D'Ammando et al 2010), where the correlated variations in optical and gamma-rays have comparable amplitudes on time scales from days to years (see however Ghisellini et al 2007).…”

Section: Pks 1502+106mentioning

confidence: 74%

INTEGRAL observations of the GeV blazar PKS 1502+106 and the hard X-ray bright Seyfert galaxy Mkn 841

Pian

Ubertini

Bazzano

et al. 2011

A&A

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Context. Extragalactic nuclear activity is most effectively explored with observations at high energies, where the most extreme flux and spectral variations are expected to occur, because of changes in either the accretion flow or the kinematics of the plasma. In active galactic nuclei of blazar type, these variations are the most dramatic. Aims. By following blazar outbursts from their onset and correlating the observed variations at many different wavelengths, we can reconstruct the behavior of the plasma and map out the development of the flare within the jet. Methods. The advent of the Fermi satellite has allowed the start of a systematic and intensive monitoring program of blazars. Blazar outbursts are very effectively detected by the LAT instrument in the MeV-GeV domain, and these can be promptly followed up with other facilities. Based on a Fermi LAT detection of a high MeV-GeV state, we observed the blazar PKS 1502+106 with the INTEGRAL satellite between 9 and 11 August 2008. Simultaneous Swift observations were also accomplished, as well as optical follow-up at the Nordic Optical Telescope. Results. The IBIS instrument onboard INTEGRAL detected a source at a position inconsistent with the optical coordinates of PKS 1502+106, but consistent with those of the Seyfert 1 galaxy Mkn 841, located at 6.8 arcmin south-west of the blazar, which is therefore responsible for all the hard X-ray flux detected by IBIS. At the location of the blazar, IBIS sets an upper limit of ∼10 −11 erg s −1 cm −2 on the 15-60 keV flux, which is consistent with a model of inverse Compton scattering accounting for the soft X-ray and gamma-ray spectra measured by Swift XRT and Fermi LAT, respectively. The gamma-ray spectrum during the outburst indicates substantial variability in the characteristic energy of the inverse Compton component in this blazar. The hard X-ray state of the Seyfert appears to be nearly unchanged with respect to the past. On the other hand, its soft X-ray flux (0.3-10 keV) varies with a ∼50% amplitude on timescales from days to years. On long timescales, this is well correlated with the optical flux, with no measurable delay. Conclusions. In PKS 1502+106, the critical parameters that control variability are the accelerating power transferred to the relativistic electrons, and the magnetic field in the emitting region. The spectrum of Mkn 841 in the 0.3-100 keV range is well described by a power-law with a cutoff at ∼150 keV and a Compton reflected continuum.

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Section: Pks 1502+106mentioning

confidence: 74%

INTEGRAL observations of the GeV blazar PKS 1502+106 and the hard X-ray bright Seyfert galaxy Mkn 841

Pian

Ubertini

Bazzano

et al. 2011

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“…PKS 1510-089 is a nearby (z = 0.36), variable, highly polarized Flat-Spectrum Radio Quasar (FSRQ, Burbidge & Kinman 1966;Stockman et al 1984;Hewitt & Burbidge 1993), well monitored at all bands from the radio to gamma rays (e.g., Malkan & Moore 1986;Thompson et al 1993;Pian & Treves 1993;Sambruna et al 1994;Lawson & Turner 1997;Singh et al 1997;Siebert et al 1998;Tavecchio et al 2000;Dai et al 2001;Gambill et al 2003;Wu et al 2005;Bach et al 2007;Li & Fan 2007;Kataoka et al 2008;Nieppola et al 2008). It is one of the brightest and most variable blazars detected by Fermi LAT (Abdo et al 2009(Abdo et al , 2010aFoschini et al 2013;Ackermann et al 2015a) and AGILE-GRID (Pucella et al 2008;D'Ammando et al 2009D'Ammando et al , 2011, and one of the only six FSRQs detected at very high energies, i.e., up to a few hundred GeV in the observer frame, with 3C 279, 4C 21.35, PKS 1441 +25, S3 0218+35, and PKS 0736+017 (Cohen et al 2003;Albert et al 2008;Aleksić et al 2011;HESS Collaboration 2013;Abeysekara et al 2015;Ahnen et al 2015;Cerruti et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Multiwavelength variability study and search for periodicity of PKS 1510–089

Castignani

Pian

Belloni

et al. 2017

A&A

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Context. Blazars are the most luminous and variable active galactic nuclei (AGNs), and thus excellent probes of accretion and emission processes close to the central engine.Aims. We concentrate here on PKS 1510-089 (z = 0.36), a member of the Flat-Spectrum Radio Quasar variety of blazars, an extremely powerful gamma-ray source and one of the brightest in the Fermi LAT catalog, to study the complex variability of its bright multiwavelength spectrum, identify the physical parameters responsible for the variations and the time scales of possible recurrence and quasi-periodicity at high energies.Methods. PKS 1510-089 was observed twice in hard X-rays with the IBIS instrument onboard INTEGRAL during the flares of Jan 2009 and Jan 2010, and simultaneously with Swift and the Nordic Optical Telescope (NOT), in addition to the constant Fermi monitoring. We also measured the optical polarization in several bands on 18 Jan 2010 at the NOT. Using these and archival data we constructed historical light curves at gamma-to-radio wavelengths covering nearly 20 years and applied tests of fractional and correlated variability. We also assembled spectral energy distributions (SEDs) based on these data and compared them with those at two previous epochs, by applying a model based on synchrotron and inverse Compton radiation from blazars. Results. The modeling of the SEDs suggests that the physical quantities that undergo the largest variations are the total power injected into the emitting region and the random Lorentz factor of the electron distribution cooling break, that are higher in the higher gammaray states. This suggests a correlation of the injected power with enhanced activity of the acceleration mechanism. The cooling likely takes place at a distance of ∼1000 Schwarzschild radii (∼0.03 pc) from the central engine, i.e much smaller than the broad line region (BLR) radius. The emission at a few hundred GeV can be reproduced with inverse Compton scattering of highly relativistic electrons off far-infrared photons if these are located much farther than the BLR, i.e., around 0.2 pc from the AGN, presumably in a dusty torus. We determine a luminosity of the thermal component due to the inner accretion disk of L d 5.9 × 10 45 erg s −1 , a BLR luminosity of L BLR 5.3 × 10 44 erg s −1 , and a mass of the central black hole of M BH 3 × 10 8 M . The fractional variability as a function of wavelength follows the trend expected if X-and gamma-rays are produced by the same electrons as radio and optical photons, respectively. Discrete Correlation Function (DCF) analysis between the long-term Steward observatory optical V-band and gamma-ray Fermi LAT light curves yields a good correlation with no measurable delay. Marginal correlation where X-ray photons lag both optical and gamma-ray ones by time lags between 50 and 300 days is found with the DCF. Our time analysis of the RXTE PCA and Fermi LAT light curves reveals no obvious (quasi-)periodicities, at least up to the maximum time scale (a few years) probed by the light curves, which ar...

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“…A prominent peak at optical-UV (rest frame) wavelengths is typical of Seyfert galaxies and is thought to be produced by thermal emission from the AGN accretion disk. However, there is an increasing number of high-power radio-loud blazars for which this emission feature is being reported (e.g, Raiteri et al 2007;Abdo et al 2009;D'Ammando et al 2009;Ghisellini, Tavecchio, Ghirlanda 2009;). Indeed, nearly half of the radio loud blazars in the sample considered by Ghisellini, Tavecchio, Ghirlanda (2009) were recently reported to show a similar optical-UV large excess.…”

Section: The Spectral Energy Distributionmentioning

confidence: 99%

“…Indeed, nearly half of the radio loud blazars in the sample considered by Ghisellini, Tavecchio, Ghirlanda (2009) were recently reported to show a similar optical-UV large excess. There is a consensus to consider this emission to come from thermal emission from the accretion disk (e.g, Raiteri et al 2007;Abdo et al 2009;D'Ammando et al 2009;Ghisellini, Tavecchio, Ghirlanda 2009;, that is not outshined by the synchrotron bump from the jet when such bump peaks at ν << 10 14.5 Hz. We also agree on such explanation for the case of NRAO 150 for the reasons outlined by .…”

Section: The Spectral Energy Distributionmentioning

confidence: 99%

The redshift and broad-band spectral energy distribution of NRAO 150

Acosta–Pulido

Agudo

Barrena

et al. 2010

A&A

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Context. NRAO 150 is one of the brightest radio and mm AGN sources in the northern sky, and is an interesting source to study extreme relativistic jet phenomena. However, its cosmological distance has not yet been calibrated, because of its optical faintness due to strong Galactic extinction. Aims. We measure the redshift of NRAO 150, to enable us to perform quantitative studies of the source. Methods. We conducted spectroscopic and photometric observations of the source in both the near-IR and the optical. Results. All these observations were successful in detecting the source. The near-IR spectroscopic observations exhibit strong Hα and Hβ emission lines from which the cosmological redshift of NRAO 150 (z = 1.517 ± 0.002) is determined for the first time. We classify the source as a flat-spectrum radio-loud quasar, for which we estimate a high supermassive black-hole mass ∼5 × 10 9 M . After extinction correction, the new near-IR and optical data show a high-luminosity continuum-emission excess in the optical (peaking in the rest frame at ∼2000 Å) that we attribute to thermal emission from the accretion disk for which we estimate a high accretion rate of ∼30% the Eddington limit. Conclusions. Comparison of the source properties and its broad-band spectral-energy distribution with those of Fermi blazars allows us to predict that NRAO 150 is among the most powerful of blazars, and hence a high luminosity -although not yet detected -γ-ray emitter.

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Gamma-ray blazars: The view from AGILE

Cited by 7 publications

References 68 publications

INTEGRAL observations of the GeV blazar PKS 1502+106 and the hard X-ray bright Seyfert galaxy Mkn 841

INTEGRAL observations of the GeV blazar PKS 1502+106 and the hard X-ray bright Seyfert galaxy Mkn 841

Multiwavelength variability study and search for periodicity of PKS 1510–089

The redshift and broad-band spectral energy distribution of NRAO 150

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