Multiband Variability Analysis of Mrk 421

Abstract

We have assembled the historical variability data of Mrk 421 at radio 15 GHz, X-ray and γ-ray bands, spanning about 6.3, 10.3 and 7.5 yr, respectively. We analyzed the variability by using three methods. The results indicated that there is a period of 287.6 ± 4.4 days for 15 GHz, 309.5 ± 5.8 days for X-ray and 283.4 ± 4.7 days for γ-ray, respectively. This period can be reasonably explained by the nonballistic helical motion of the emitting material. The correlation analysis suggested that the variabilities of radio 15 GHz, X-ray and γ-ray are remarkable correlated, and the emission of radio 15 GHz lags behind that of X-ray, and the X-ray flux lags behind the γ-ray. This suggests that the γ-ray derives from inverse Compton (IC) scattering of the synchrotron photons, supporting the synchrotron self-Compton (SSC) model. Moreover, the time delay between different wavebands could be explained by the shock-in-jet models, in which a moving emission region produces the radio to γ-ray activity, implying that the emission region of γ-ray is closer to the center than ones of X-ray and radio emission.

The Nature of γ-Ray Variability in Blazars

“…The LSP along with 90% and 99% are shown in panel b) of Figure 6 and the tentative peaks of the oscillation are marked with vertical lines drawn at an interval nearly equal to the period as shown in the panel b) of Figure 5. The detection supports the previous claim by Li et al (2016) who reported the exact same period in the γ-ray band along with the similar one in 15 GHz radio observations. However, in the analysis presented by Sandrinelli et al (2017), it was not found to be significant enough.…”

Gamma-ray and optical oscillations of 0716+714, MRK 421, and BL Lacertae

“…On a similar timescale, a strong and persistent quasi-periodic signal was also detected in the flat spectrum radio quasar PKS 1156+295 (Wang et al 2014). Recently, searching for periodicities in inhomogeneous covered light curves, Li et al (2016) found oscillations of 290-to 300-day duration in the X-ray and γ-ray light curves of MRK 421 at ∼ 2.5σ over the red noise and a faint signal in radio, which were ascribed to helical motions of the emitting material. In the X-ray domain, a 420-day quasi-periodicity in 1ES 2321+419 was reported by Rani et al (2009).…”

Optical Quasi-periodic Oscillation of the BL Lacertae Object S5 0716+714 during the Faint State

“…The fitting result shows a possible QPO=0.035 day (50.4 min). The Lomb-Scargle method (Lomb 1976 andScargle 1982) is commonly used to detect periodicity in the spectrum of time series including unevenly sampled time series (Li et al 2016;Xiong et al 2017). We also employ hour ≃ 57 min) in the spectrum of a time series is significant against the red-noise background from an AR1 process, with 99% χ 2 significance levels (bottom panel in Fig.…”

“…The fitting result shows a possible QPO=0.035 day (50.4 min). The Lomb-Scargle method (Lomb 1976 andScargle 1982) is commonly used to detect periodicity in the spectrum of time series including unevenly sampled time series (Li et al 2016;Xiong et al 2017). We also employ the Lomb-Scargle method to analyze the possible QPO on March 19 2010 (middle panel in Fig.…”