Detection of Periodic Radio Signal from the Blazar J1043+2408

Abstract

Search for periodic signals from blazars has become widely discussed topic in recent years. In the scenario that such periodic changes originate from the innermost regions of blazars, the signals bear imprints of the processes occurring near the central engine, which is mostly inaccessible to our direct view. Such signals provide insights into various aspect of blazar studies including disk-jet connection, magnetic field configuration and, more importantly, strong gravity near the supermassive black holes and release of gravitational waves from the binary supermassive black hole systems. In this work, we report detection of a periodic signal in the radio light curve of the blazar J1043+2408 spanning ∼10.5 years. We performed multiple methods of time series analysis, namely, epoch folding, Lomb-Scargle periodogram, and discrete auto-correlation function. All three methods consistently reveal a repeating signal with a periodicity of ∼ 560 days. To robustly account for the red-noise processes usually dominant in the blazar variability and other possible artifacts, a large number of Monte Carlo simulations were performed. This allowed us to estimate a high significance (99.9% local and 99.4% global) against possible spurious detection. As possible explanations, we discuss a number of scenarios including binary supermassive black hole system, Lense-Thirring precession and jet precession.

Is OJ 287 a Single Supermassive Black Hole?

“…The precession of a slowly rotating black hole with a high mass accretion rate and a low α vis (as confirmed by observations [49]) can occur with the found period. On the other hand, it is possible that misalignment of the black hole and accretion disc rotation axes can cause precession of the outer part of the accretion disc with a period [48]:…”

Study of Periodic Signals from Blazars

“…As a result, the hunt for periodic signals in blazar light curves has become an active field of research: blazar OJ 287 is famous for its ∼12-year periodicity detected in its historical optical light curve [6,7] and another famous source PG 1553 + 113 is found to show 2.18-year periodic modulations in its γ-ray observations from the Fermi/LAT, which was first reported in [8]. In addition, several authors have reported the existence of QPOs of various characteristic timescales in numerous blazar multi-frequency light curves including the four cases of QPO detection by our research group see [4,[9][10][11] and the references therein.…”

“…As an illustration, for blazars having typical radio spectral index (α = 0.6) and viewing angles in the 1-5 • range, a slight change in the viewing angle e.g., ∼1.5 • , is sufficient to produce observed maxima twice as bright as minima in the light curves refer to Figure 4 in [10].…”

“…In order to estimate the significance of the detection, a large number of Monte Carlo simulations were performed. This resulted in a significance of 99.9% 99.4% local and global, respectively, for details see [10].…”