Study On The Periodicity Of Blazar Radiation

Active galactic nuclei(AGNs)are high-energy celestial radiation sources powered by the accretion of supermassive black holes in galaxies.Their radiation covers the entire electromagnetic waveband and presents unique observational features.Blazars are the most special subclass of AGN,their relativistic jets are directed toward the observer,blazars present obvious and rapid light changes,the full-band spectral energy distribution(SED)presents a double-peak structure,and the low-energy peak is composed of Synchrotron radiation is dominant,and the high-energy peak is dominated by inverse Compton scattering.Current research has found that hadron processes are also involved in high-energy radiation.Blazars include two subcategories of the BL Lacertae object(BL Lac)and the Flat-spectrum Radio Quasar(FSRQ).From BL Lac to FSRQ,the luminosity and accretion rate also show a certain trend of change with the blazar synchronous peak frequencyChapter 1 of this paper introduces active galactic nuclei from essential characteristics,classification,and unified model.Chapter 2 introduces the basic characteristics of blazars,energy spectrum structure,synchrotron radiation and inverse Compton scattering in the lepton process,and the hadron process used to explain the high-energy radiation of blazars.In Chapter 3,we study long-term Quasiperiodic Oscillation(QPO)of blazars.(1)We systematically searched for long-time-scale QPOs in more than 1800 sources monitored by the 40m radio telescope at the Owens Valley Radio Astronomy Observatory for a long time,and found that the BL Lac object CGRa BS J0929+5013 and the FSRQ object CGRa BS J2146-1525 have year-like QPOs in the radio band.Calculation results of Lomb-Scargle periodogram(LSP)and Weighted Wavelet Z-transform(WWZ)methods show that the J0929+5013 and J2146-1525 radio bands have QPOs of 3.93years and 3.62 years,respectively,and the confidence level exceeds 3.In addition,the J2146-1525 high-energy gamma band also has a QPO similar to the radio band(its power is lower).The discrete correlation function(Discrete Correlation Function,DCF)gives very weak correlations between J0929+5013 and J2146-1525 in the radio and gamma bands,revealing that the radiation in the two bands may come from different radiation regions in the jet.The binary black hole system can explain their QPO,and the main black hole masses of J0929+5013 and J2146-1525 are4.3×10~9_⊙and 2.7×10~9_⊙,respectively.In Chapter 3,we study long-term QPO of blazars.(2)We systematically search for long-term standard QPO in more than1,800 sources monitored by the 40m radio telescope at the Owens Valley Radio Astronomy Observatory.The results show that The BL Lac object CGRa BS J0929+5013 and the FSRQ object CGRa BS J2146-1525 have year-like QPOs in the radio band.Calculation results of Lomb-Scargle periodogram(LSP)and Weighted Wavelet Z-transform(WWZ)methods show that the J0929+5013 and J2146-1525radio bands have QPOs of 3.93 years and 3.62 years,respectively,and the confidence level exceeds 3.High-energy gamma-band J2146-1525 also has a radio-like weaker QPO.Discrete Correlation Function(Discrete Correlation Function,DCF)gives J0929+5013 and J2146-1525 radio and gamma bands are weakly correlated,explaining that the radiation comes from different regions.The binary black hole system can explain their QPO,and the main black hole masses of J0929+5013 and J2146-1525 are 4.3×10~9_⊙and 2.7×10~9_⊙,respectively.(2)In order to search for evidence of multi-band QPO and study its radiation source,we studied the radio,optical,gamma,and X-band long-term light variability data of the blazar PG1553+113,and the results showed that its multiple bands There is evidence of QPO,and the QPO is about 2.2 years.The radio,optical,and gamma bands are strongly correlated,and there is a certain delay between them,the gamma band is ahead of the optical band,and the optics are ahead of the radio band.PG 1553+113 has credible QPO in multiple bands to support the supermassive double black hole system in the center of the galaxy.The orbital plane of the secondary black hole has an included angle with the main accretion disk,and the movement of the secondary black hole causes the oscillation of the primary black hole disk,which in turn affects the jet flow Vibration of matter.The strong correlation of multiple bands supports the SSC model,that is,the radiation of multiple bands comes from the same radiation area,and the photons of synchrotron radiation and inverse Compton scattering come from the same batch of photons.In Chapter 4,we searched for monthly QPO among the 1525sources of high variability given by Fermi-Large Area Telescope(Fermi-LAT),and found a transient QPO of 31.3±1.8 days in Te V blazar S5 0716+714,using three methods WWZ,LSP and REDFIT confirmed the signal,we simulated 10~6 light curves based on the power spectral density and probability density function of the original light curve to estimate the confidence,the results show that the confidence is around 4.1.and the seasonal autoregressive moving average model It is revealed that it is an important physical QPO,and the helical jet model can well explain this transient QPO.