The X-Ray Outburst of PG 1553+113: A Precession Effect of Two Jets in the Supermassive Black Hole Binary System

Abstract

Blazar PG 1553+113 is thought to be a host of supermassive black hole binary system. A 2.2 yr quasi-periodicity in the γ-ray light curve was detected, possibly a result of jet precession. Motivated by the previous studies based on the γ-ray data, we analyzed the X-ray light curve and spectra observed during 2012–2020. The 2.2 yr quasi-periodicity might be consistent with the main-flare recurrence in the X-ray light curve. When a weak rebrightening in the γ-ray was observed, a corresponding relatively strong brightening in the X-ray light curve can be identified. The harder-when-brighter tendency in both X-ray main and weak flares was shown, as well as a weak softer-when-brighter behavior for the quiescent state. We explore the possibility that the variability in the X-ray band can be interpreted with two-jet precession scenario. Using the relation between jets and accretion disks, we derive the primary black hole mass ≃3.47 × 108 M ☉ and mass of the secondary one ≃1.40 × 108 M ☉, and their mass ratio ∼0.41.

A Geometric Model to Interpret the γ-Ray Quasiperiodic Oscillation of PG 1553+113

“…Yan et al (2018) claimed that the relativistic boost might result in the QPO of PG 1553+113 by cyclically varying Doppler factors. This finding is not at odds with previous studies (e.g., Caproni et al 2017;Cavaliere et al 2017;Sobacchi et al 2017;Tavani et al 2018;Huang et al 2021). However, the origin of the periodical Doppler factor is still under debate.…”

“…Subsequently, Tavani et al (2018) took advantage of 9 yr data of Fermi-LAT and verified the 2.2 yr QPO of γ-ray exists in PG 1553+113. Huang et al (2021) confirmed that the 2.2 yr quasiperiodicity might be consistent with the recurrence of the primary flare on the X-ray light curve.…”

“…The mechanism of QPO in the light curve of a blazar is still unclear and under debate. The most popular explanation is the precession of the jet (e.g., Carrara et al 1993;Abraham 1998;Caproni et al 2017;Sobacchi et al 2017;Britzen et al 2018;Huang et al 2021). Moreover, a few scenarios have been considered such as the helical structure of the jet (e.g., Rieger 2004;Zhou et al 2018), beaming effect (e.g., Villata et al 1998), lighthouse effect (e.g., Camenzind & Krockenberger 1992), and the black hole-disk impaction (e.g., Valtonen et al 2016;Dey et al 2018).…”

“…Moreover, a few scenarios have been considered such as the helical structure of the jet (e.g., Rieger 2004;Zhou et al 2018), beaming effect (e.g., Villata et al 1998), lighthouse effect (e.g., Camenzind & Krockenberger 1992), and the black hole-disk impaction (e.g., Valtonen et al 2016;Dey et al 2018). Recently, the QPO of PG 1553+113 may result from the jet precession in a Binary System of Supermassive Black Holes (e.g., Caproni et al 2017;Cavaliere et al 2017;Sobacchi et al 2017;Tavani et al 2018;Huang et al 2021). Particularly, Tavani et al (2018) identified secondary peaks ("twin peaks") that occur in closely symmetric pairs on both sides of main peaks and are supported by correlated X-ray outbursts.…”

Multiwavelength periodicity search in a sample of $γ$-ray bright blazars

“…(iii) Each black hole hosts a relativistic jet that contributes to the overall emission (Villata et al 1998;Huang et al 2021). The (quasi-)periodic variability is then introduced by the orientations of both jets.…”