Studying the periodic flux-variation behavior of blazars is vital for probing supermassive black hole binaries and the kinematics of relativistic jets. In this work, we report the detection of the multi-band possible periodic variations of the blazar PKS J2134-0153, including the infrared ($1.6(\pm0.4)\times 10^3$ days) and optical ($1.8(\pm1)\times 10^3$ days). The periods in the infrared and optical bands are statistically consistent with the period in the radio band ($P_{\mathrm{Radio}}$$ = 1760\pm33$ days, obtained from our previous work). Moreover, flux variations in different bands are correlated with evident inter-band time delays, and the time lags of infrared and optical emission with respect to radio emission are $(3.3\pm2.3)\times10^{2}$ days and $(3.0\pm2.3)\times10^{2}$ days, respectively. The cross-correlations indicate a common origin of radio, infrared, and optical emission. The relative positions between emission regions of infrared and optical emission to radio emission are estimated according to the time lags, i.e., $0.37\pm0.26$ pc and $0.33\pm0.26$ pc. The relative distances seem to be quantitatively consistent with the theoretical prediction.
We present the results of a multifrequency campaign on the high-redshift (z = 3.1) blazar PKS 0537-286. The source was observed at different epochs from 2006 to 2008 with INTEGRAL and Swift, and nearly simultaneously with ground-based near-IR/optical telescopes. The SEDs are compatible with a model based on synchrotron radiation and external inverse Compton scattering. The campaign gives an insight into the physical environment of the blazar.
We present a revised analysis of the photometric reverberation mapping campaign of the narrow-line Seyfert 1 galaxy PKS 0558-504 carried out with the Swift Observatory during 2008--2010. Previously, Gliozzi et al.\ found using the Discrete Correlation Function (DCF) method that the short-wavelength continuum variations lagged behind variations at longer wavelengths, the opposite of the trend expected for thermal reprocessing of X-rays by the accretion disc, and they interpreted their results as evidence against the reprocessing model. We carried out new DCF measurements that demonstrate that t…
Highly energetic, variable and distant sources such as Active Galactic Nuclei provide a good opportunity to evaluate effects due to the emission and the propagation of high energy photons. In this note, a study of possible energy-dependent time-lags with PKS 2155-304 light curve as measured by H.E.S.S. in July 2006 is presented. These time-lags could either come from the emission processes or also sign a Lorentz Symmetry breaking as predicted in some Quantum Gravity models. A Cross-Correlation function and a Wavelet Transform were used to measure the time-lags. The 95% Confidence Limit on the …
We investigate the dichotomy between jetted and non-jetted Active Galactic Nuclei (AGNs), focusing on the fundamental differences of these two classes in the accretion physics onto the central supermassive black hole (SMBH). Our aim is to study and constrain the structure, kinematics and physical state of the nuclear environment in the Broad Line Radio Galaxy (BLRG) PKS 2251+11. The high X-ray luminosity and the relative proximity make such AGN an ideal candidate for a detailed analysis of the accretion regions in radio galaxies. We performed a spectral and timing analysis of a $\sim$64 ks obs…
We have analyzed XMM-Newton observations of the high energy peaked blazar, PKS 2155-304, made on 24 May 2002 in the 0.3 - 10 keV X-ray band. These observations display a mini-flare, a nearly constant flux period and a strong flux increase. We performed a time-resolved spectral study of the data, by dividing the data into eight segments. We fitted the data with a power-law and a broken power-law model, and in some of the segments we found a noticeable spectral flattening of the source's spectrum below 10 keV. We also performed time-resolved cross-correlation analyses and detected significant ha…
PKS 2131-021 -- Discovery of Strong Coherent Sinusoidal Variations from Radio to Optical Frequencies: Compelling Evidence for a Blazar Supermassive Black Hole Binary
Most large galaxies host supermassive black holes in their nuclei and are subject to mergers, which can produce a supermassive black hole binary (SMBHB), and hence periodic signatures due to orbital motion. We report unique periodic radio flux density variations in the blazar PKS~2131$-$021, which strongly suggest an SMBHB with an orbital separation of $\sim 0.001-0.01$ pc. Our 45.1-year radio light curve shows two epochs of strong sinusoidal variation with the same period and phase to within $<2\%$ and $\sim 10\%$, respectively, straddling a 20-year period when this variation was absent. Our …
Atacama Cosmology Telescope: Observations of supermassive black hole binary candidates. Strong sinusoidal variations at 95, 147 and 225 GHz in PKS 2131$-$021 and PKS J0805$-$0111
David A. Dunlap Department of Astronomy & Astrophysics, University of Toronto（多伦多大学）；Specola Vaticana (Vatican Observatory)（梵蒂冈天文台）；Kavli Institute for Astronomy & Astrophysics, Peking University（北京大学）；Department of Astronomy, School of Physics, Peking University（北京大学物理学院天文学系）；Astronomical Observatory, University of Warsaw（华沙大学）；Institute of Theoretical Astrophysics, University of Oslo（奥斯陆大学）；Institute of Astrophysics, Foundation for Research & Technology-Hellas（希腊研究与技术基金会）；Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics, Stanford University（斯坦福大学）；Canadian Institute for Theoretical Astrophysics, University of Toronto（多伦多大学）；Department of Physics & Astronomy, University of Pennsylvania（宾夕法尼亚大学）；Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University（普林斯顿大学）；Department of Astrophysical Sciences, Peyton Hall, Pr（普林斯顿大学）
Constraining Orbital Eccentricity of a Supermassive Black Hole Binary Candidate PKS 2131-0211
Joint Astronomy Programme, Department of Physics, Indian Institute of Science（印度科学研究所物理系联合天文学项目）；Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research（塔塔基础研究院天文与天体物理学系）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Department of Physical Sciences, Indian Institute of Science Education and Research Kolkata（加尔各答印度科学教育研究所物理科学系）
Flat spectrum radio quasars (FSRQs) can suffer strong absorption above E = 25/(1+z) GeV, due to gamma-gamma interaction if the emitting region is at sub-parsec scale from the super-massive black hole (SMBH). Gamma-ray flares from these astrophysical sources can investigate the location of the high-energy emission region and the physics of the radiating processes. We present a remarkable gamma-ray flaring activity from FSRQ PKS 2023-07 during April 2016, as detected by both AGILE and Fermi satellites. An intensive multi-wavelength campaign, triggered by Swift, covered the entire duration of the…
PKS 1510-089 is one of the most variable blazars in the third Fermi-LAT source catalog. During 2015, this source has shown four flares identified as flare A, B, C, and D in between three quiescent states Q1, Q2, and Q3. The multi-wavelength data from Fermi-LAT, Swift-XRT/UVOT, OVRO, and SMA observatory are used in our work to model these states. Different flux doubling times have been observed in different energy bands which indicate there could be multiple emission zones. The flux doubling time from the gamma-ray and X-ray light curves are found to be 10.6 hr, 2.5 days, and the average flux d…
We study the long-term behavior of the bright gamma-ray blazar PKS 0402-362. We collected approximately 13 years of Fermi-LAT data between Aug 2008 to Jan 2021 and identified three bright $γ$-ray activity epochs. The second was found to be the brightest epoch ever seen in this source. We observed most of the $γ$-ray flare peaks to be asymmetric in profile suggesting a slow cooling time of particles or the varying Doppler factor as the main cause of these flares. The $γ$-ray spectrum is fitted with PL and LP spectral models, and in both cases, the spectral index is very steep. The $γ$-ray spect…
The profiles of the broad emission lines of active galactic nuclei (AGNs) and the time delays in their response to changes in the ionizing continuum ("lags") give information about the structure and kinematics of the inner regions of AGNs. Line profiles are also our main way of estimating the masses of the supermassive black holes (SMBHs). However, the profiles often show ill-understood, asymmetric structure and velocity-dependent lags vary with time. Here we show that partial obscuration of the broad-line region (BLR) by outflowing, compact, dusty clumps produces asymmetries and velocity-depe…
20 years of monitoring: PKS 2155-304 and PKS 1510-089 in the eyes of Swift and Fermi. I. The case of PKS 2155-304
Institute of Nuclear Physics, Polish Academy of Sciences（波兰科学院核物理研究所）；Landessternwarte, Universität Heidelberg（海德堡大学州立天文台）；Centre for Space Research, North-West University（西北大学空间研究中心）
Blazar jets are renowned for their rapid violent variability and multiwavelength flares, however, the physical processes responsible for these flares are not well understood. In this paper we develop a time-dependent inhomogeneous fluid jet emission model for blazars. We model optically thick radio flares for the first time and show that they are delayed with respect to the prompt optically thin emission by ~ months to decades, with a lag that increases with the jet power and observed wavelength. This lag is caused by a combination of the travel time of the flaring plasma to the optically thin…
We present multi-wavelength spectral and temporal variability analysis of PKS 0027-426 using optical griz observations from DES (Dark Energy Survey) between 2013-2018 and VOILETTE (VEILS Optical Light curves of Extragalactic TransienT Events) between 2018-2019 and near infrared (NIR) JKs observations from VEILS (VISTAExtragalactic Infrared Legacy Survey) between 2017-2019. Multiple methods of cross-correlation of each combination of light curve provides measurements of possible lags between optical-optical, optical-NIR, and NIR-NIR emission, for each observation season and for the entire obser…
We have used a stringy model of quantum space-time foam to suggest that the vacuum may exhibit a non-trivial refractive index depending linearly on gamma-ray energy: eta -1 ~ E_gamma/M_QG1, where M_QG1 is some mass scale typical of quantum gravity that may be ~ 10^18 GeV: see Phys. Lett. B 665, 412 (2008) and references therein. The MAGIC, HESS and Fermi gamma-ray telescopes have recently probed the possible existence of such an energy-dependent vacuum refractive index. All find indications of time-lags for higher-energy photons, but cannot exclude the possibility that they are due to intrinsi…
Multiwavelength quasi-periodic variability of the blazar Ton 599
Special Astrophysical Observatory of the Russian Academy of Sciences（俄罗斯科学院特别天文台）；Xinjiang Astronomical Observatory, CAS（中国科学院新疆天文台）；Crimean Astrophysical Observatory of the Russian Academy of Sciences（俄罗斯科学院克里米亚天文台）；State Key Laboratory of Radio Astronomy and Technology, Shanghai Astronomical ObservatoryChinese Academy of Sciences（中国科学院上海天文台射电天文与技术国家重点实验室）；Guizhou Radio Astronomical Observatory, Guizhou University（贵州大学贵州天文台）；Lebedev Physical Institute of Russian Academy of Sciences（俄罗斯科学院列别捷夫物理研究所）；Institute for Nuclear Research, Russian Academy of Sciences（俄罗斯科学院核物理研究所）
