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

Abstract

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...

Two-zone Emission Modeling of PKS 1510-089 during the High State of 2015

“…The peak observed at the edge of the DCF can be discarded. A time lag of 50 days between gamma-rays and X-rays has been seen by Castignani et al (2017) in PKS 1510-089. This time lag between gamma-rays and X-rays suggests that the X-rays might have been produced far away from the region of gamma-ray emission in the jet.…”

A comprehensive power spectral density analysis of astronomical time series I: the Fermi-LAT gamma-ray light curves of selected blazars

“…More recently, Sandrinelli et al (2016) were looking for QPOs in multiwavelength data of PKS 1510−089, uncovering a HE γ-ray periodicity with a period of 115 days at the 2.58σ significance level, and two optical peaks at 345 and 575 days. On the other hand, neither Castignani et al (2017) nor Gupta et al (2019) found any QPOs in 8-years-long and 7-years-long Fermi -LAT LCs, respectively.…”

Broad line region and black hole mass of PKS 1510-089 from spectroscopic reverberation mapping

“…Similar to other radio-loud AGNs, PKS 1510-089 shows strong flux variation across the entire electromagnetic spectrum from radio to γ ray (e.g., Malkan & Moore 1986;Tavecchio et al 2000;Bach et al 2007;Abdo et al 2010a;Marscher et al 2010;Orienti et al 2013;H.E.S.S. Collaboration 2013;Kushwaha et al 2016;Beaklini et al 2017;Castignani et al 2017;Prince et al 2019). However, the BLR of PKS 1510-089 remains poorly studied due to its strong radio emission, although the size of its BLR is an important model parameter in the multi-band SED fitting.…”

“…Using UV data, Abdo et al (2010a) estimated a black hole mass for PKS 1510-089 as M BH = 5.4 × 10 8 M . On the other hand, Castignani et al (2017), using the Shakura & Sunyaev (1973) model, estimated a black hole mass of 2.4 × 10 8 M . Therefore, a large range of black hole masses, 1−9 × 10 8 M , for PKS 1510-089 has been reported in the literature.…”