X-ray variability of SS 433: Evidence for supercritical accretion

Abstract

We study the X-ray variability of SS 433 based on data from the ASCA observatory and the MAXI and RXTE/ASM monitoring missions. Based on the ASCA data, we have constructed the power spectrum of SS 433 in the frequency range from 10 −6 to 0.1 Hz, which confirms the presence of a flat portion (flat-topped noise) in the spectrum at frequencies 3 × 10 −5 − 10 −3 Hz. The periodic variability (precession, nutation, eclipses) begins to dominate significantly over the stochastic variability at lower frequencies, which does not allow the stochastic variability to be studied reliably. The best agreement with the observations is reached by the model with the flat portion extending to 9.5 × 10 −6 Hz and a power-law spectrum with index of 2.6 below that frequency. The jet nutation with a period of about three days suggests that the time for the passage of material through the disk is less than this value. Therefore, at frequencies below 4 × 10 −6 Hz, the power spectrum probably does not reflect the disk structure. It may depend on other factors, for example, a variable mass accretion rate supplied by the donor. The flat portion may arise from a rapid decrease in the viscous time in the supercritical or radiative disk zones. It could be related to the variability of the X-ray jets that are formed in the supercritical region.

Periodic Fast Radio Bursts from Luminous X-ray Binaries

“…A similar model was proposed to explain the 164 d jet precession timescale of SS433 (Sarazin et al 1980;Katz 1981). Superorbital periods in the range of tens of days to 100 d, which could be attributed to precession 19 , have been observed in several ULXs (e.g., Mioduszewski et al 2004;Grisé et al 2013;Atapin & Fabrika 2016;Luangtip et al 2016;Brightman et al 2019Brightman et al , 2020Vasilopoulos et al 2020; see Weng & Feng 2018 for a systematic search with Swift observatory).…”

“…SS433 in fact exhibits X-ray emission with evidence for precession in the light curve(Atapin & Fabrika 2016), which are believed to arise from the jet rather than the accretion disk.16 Making such systems stable also reduces the predicted rate of binary BH mergers from population synthesis models, bringing them into better accord with observations by LIGO/Virgo.…”

Ultraluminous X-Ray Sources

“…However, continued monitoring revealed that the modulation phase changed by 0.4 after a major outburst and was interpreted as evidence in favor of a superorbital origin (Pasham & Strohmayer 2013a). However, the phase of the X-ray minima of the 13 day orbital modulation of SS 433 is known to depend on the 162 day precession period of the jets (Atapin & Fabrika 2016), hence the orbital interpretation is not excluded.…”

Ultraluminous X-ray sources with flat-topped noise and QPO

“…Examining the fast X-ray variability of SS 433 (Revnivtsev et al 2006), it has been found that its power density spectrum is well-fitted by a broken power-law with a flat component (P ∝ f 0 ) below 10 −3 Hz (Atapin et al 2015;Atapin & Fabrika 2016). This type of variability is similar to the flat-topped noise (hereafter FTN) observed in BHBs at the state of low accretion rate, i.e.…”

“…The linear rms-flux relation is observed in binary systems with black holes and neutron stars (Uttley & McHardy 2001;Gleissner et al 2004;Uttley 2004), active galactic nuclei (Vaughan et al 2003b gests that this mechanism must work in these systems as well. Moreover, the Lyubarskii's model was successfully applied to the variability of the supercritical accretion disc of SS 433 (Revnivtsev et al 2006;Atapin et al 2015;Atapin & Fabrika 2016).…”