Subjects: Astronomy >> Astrophysical processes submitted time 2023-12-06 Cooperative journals: 《天文研究与技术》
Abstract： Multi band correlation analysis is of great significance to the study of the physical model and radiation mechanism of Blazars. In order to study the physical model of TeV Blazars, we search and sort out their γ-ray band data and optical band data according to the names and coordinates of their counterparts of 78 TeV Blazars in the 4FGL-DR3 catalogue, and find that there are 56 TeV Blazars with both optical band and γ-ray band data. The Discrete Correlation Function (DCF) is used to calculate the correlation between the optics and γ-ray of each Blazar. The calculation results show that 20 sources show weak γ-ray-optical correlation, 30 sources show strong γ-ray-optical correlation, and 6 sources show no γ-ray-optical correlation. Among sources that exhibit strong correlation. there is also varying degrees of time delay between the optical and γ-ray bands. These results support that the high-energy photons of TeV Blazar mainly come from synchronous self Compton radiation of lepton model. However, we also find that there are some “orphan flares” in both the optical and γ-ray bands, which may indicate that the source of low energy photons is not unique.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-12-06 Cooperative journals: 《天文研究与技术》
Abstract： We study the characteristics of radio galaxy (RDG) and Narrow line Seyfert 1 (NLSY1) in the fourth Fermi LAT catalogue, the distribution characteristics of γ-ray flux and the RMS-Flux linear relationship. Based on these two types of active galactic nuclei in the data processing of γ-ray flux, the Gaussian function and log-normal distribution function are used to fit the flux distribution. By K-S test, S-W test, and reduced chi square χ2. It is found that the distributions of RDG and NLSY1 are more consistent with the log-normal distribution than the Gaussian distribution, which indicates that their light variability may have nonlinear and multiplicative properties. In addition, linear fitting is also performed on two different groups of RMS-Flux for these two types of sources, and it is found that RMS-Flux has a strong linear correlation and its slopes are both positive.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-11-27 Cooperative journals: 《天文研究与技术》
Abstract： We find that the optical band light curve of the blazar PKS 0422 + 004 observed by the Transiting Exoplanet Survey Satellite (TESS) has a quasiperiodic oscillation (QPO) of about 7.4 days in sector 32. We use the Lomb-Scargle Periodogram (LSP) method to search for significant periods, and further validate them using the Weighted Wavelet Z-transform (WWZ) method for time-frequency domain analysis. Finally, based on Schwarzschild black hole (a=0) and extreme Kerr black hole (a=0. 998 2) models, we estimate the mass of the central black hole of this blazar. We obtain black hole masses of 1. 11 × 109 M☉ (Schwarzschild black hole) and 7.07 × 109M☉ (extreme Kerr black hole) with a main period of 7.4 days.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-11-17 Cooperative journals: 《天文研究与技术》
Abstract： The variability is one of the most fundamental observational features of Blazars, the generation of Intra-Day Variability (IDV) is still a controversial issue. In this paper, we combine the 4LAC-DR2 catalog with the fifth Roma-BZCAT catalog to study the characteristics of mid-infrared IDV of different classes of Blazars using data from the ALLWISE project. The results show that: (1) The IDV of Low Synchrotron Peaked Blazars (LSPs) exhibit larger variability amplitudes compared to Intermediate Synchrotron Peaked Blazars (ISPs) and High Synchrotron Peaked Blazars (HSPs); (2) The IDV of Flat Spectrum Radio Quasars(FSRQs) also exhibit larger variability amplitudes compared to BL Lacertae objects (BL Lacs), and the color changes of both tend to become bluer when brighter; (3) The IDV of Fermi-detected Blazars exhibits a smaller variability amplitude compared to Non-Fermi￣detected Blazars. Based on the study of the above results, we suggest that Blazars′ observed emission in the mid-infrared band may come from a spatial scale range of ~10-4 pc, that its IDV production may be related to physical processes intrinsic the jet, and that the amplitudes of the IDV may be closely related to the synchrotron peak of the Spectral Energy Distribution (SED).
Subjects: Astronomy >> Astrophysical processes submitted time 2023-10-20 Cooperative journals: 《天文研究与技术》
Abstract： The variability is an important observational feature of Blazars. In order to study the multiband optical variability of Blazar, we collected the light curves of PKS 1424-41 of the gamma-ray band (0.1-100GeV), optical R band, near infrared K band, X band and radio band, released by Fermi LAT, SMARTS, SWIFT (XRT) and Submillimeter Array (SMA). Discrete correlation function is used to analyze the correlation between the light curves. The results show that the gamma-ray band, X-band, optical R-band, near-infrared K-band and radio band are strongly correlated with each other, and there is a time delay between the bands. This result supports the “single region” lepton radiation model. The LSP (Lomb-Scargle Periodogram) method is used to analyze the Quasi-periodic Oscillations (QPO) of PKS 1424-41 for the γ band Light Curve in a flare period (MJD56100-MJD56500). It is found that there are two QPOs in this period: ~75 days and ~50 days, with a ratio of 3∶2. The helical structure of the jet itself and the radiation of high-energy plasma matter moving within it may be the origin of this monthly QPO.
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