A Rapid Change in X-Ray Variability and a Jet Ejection in the Black Hole Transient MAXI J1820+070

Abstract

We present Neutron Star Interior Composition Explorer X-ray and Arcminute Microkelvin Imager Large Array radio observations of a rapid hard-to-soft state transition in the black hole X-ray transient MAXI J1820+070. During the transition from the hard state to the soft state a switch between two particular types of quasiperiodic oscillations (QPOs) was seen in the X-ray power density spectra, from type-C to type-B, along with a drop in the strength of the broadband X-ray variability and a brief flare in the 7-12 keV band. Soon after this switch (∼1.5-2.5 hr) a strong radio flare was observed that corresponded to the launch of superluminal ejecta. Although hints of a connection between QPO transitions and radio flares have been seen in other black hole X-ray transients, our observations constitute the strongest observational evidence to date for a link between the appearance of type-B QPOs and the launch of discrete jet ejections. are usually recognized: the hard state, which shows strong rapid (subsecond) X-ray variability and a spectrum dominated by Comptonized power-law emission, and the soft state, in which rapid X-ray variability is weak and where a thermal disk blackbody component dominates the spectrum. The transitions between these two spectral states, during which sources are often classified as being in an intermediate state, are accompanied by strong evolution of the X-ray variability properties. As a source starts the transition from the hard state to the soft state, strong (type-C) low-frequency quasi-periodic oscillations (QPOs) are usually present in the power density spectra (see Wijnands et al. 1999;Remillard et al. 2002;Casella et al. 2005, for the various low-frequency QPO types). Their frequencies increase from ∼0.01 Hz to ∼10 Hz as the spectrum softens. At some point during the transition the type-C QPOs and arXiv:2003.01012v1 [astro-ph.HE]

MAXI J1820+070 with NuSTAR – II. Flaring during the hard to soft state transition with a long soft lag

“…The NuSTAR data from the initial hard state are analysed in Buisson et al (2019), showing that the evolution is governed by changes in coronal rather than disc geometry, agreeing with the trend in reverberation lags seen in NICER data (Kara et al 2019). Several phenomena during the transition have already been reported, including a bipolar radio plasma ejection (Bright et al 2020) and a type B QPO (Homan et al 2020). The jet ejecta were also observed in X-rays (Espinasse et al 2020).…”

“…The variability in MAXI J1820+070 analysed here occurs close to but distinct in time to several other features in the state change. There may be some association with the jet: around 1 day before the flaring variability, there is a jet ejection coincident with a type B QPO (Bright et al 2020;Espinasse et al 2020;Homan et al 2020). The flaring is too late to be directly associated with the ejection but could represent settling from the post-ejection state to an equilibrium.…”

Disk, Corona, Jet Connection in the Intermediate State of MAXI J1820+070 Revealed by NICER Spectral-timing Analysis

“…MAXI J1820+070 is one of the brightest BHBs detected so far, and has exhibited a great amount of activity in radio (Bright et al 2020;Homan et al 2020), NIR (Sánchez-Sierras & Muñoz-Darias 2020), optical (Muñoz-Darias et al 2019;Paice et al 2019;Shidatsu et al 2019;Veledina et al 2019), ultraviolet (UV; Kajava et al 2019), and X-ray (Buisson et al 2019;Kara et al 2019;Espinasse et al 2020;Wang et al 2020b;Buisson et al 2021;You et al 2021;Zdziarski et al 2021). In the hard state, reverberation analysis using the Neutron Star Interior Composition Interior Explorer (NICER; Gendreau et al 2016) showed that while the broad iron line profile remained constant (and only the narrow component decreased), the frequency range where the (soft) reverberation lag dominated increased (Kara et al 2019).…”

“…This hypothesis has been later confirmed by reflection spectroscopy in the context of a dual-lamppost, where the height of the upper lamppost decreased while the lower one stayed constant (Buisson et al 2019), and by the increase of the peak frequency of the quasi-periodic oscillations (QPOs; Ingram & Motta 2019). During the hard-to-soft transition, an extremely powerful superluminal ejection was observed in the radio band (Bright et al 2020) very close in time with a small flare in the 7-12 keV band and a transition from type-C to type-B QPO (Homan et al 2020).…”

The Binary Mass Ratio in the Black Hole Transient MAXI J1820+070

“…Fabian et al 2020). During the state transition, a change on the type of X-ray quasi-periodic oscillations was observed and immediately followed by the launch of a relativistic jet (Homan et al 2020;.…”