From Multiwavelength to Mass Scaling: Accretion and Ejection in Microquasars and AGN

Abstract

A solid theoretical understanding of how inflowing, accreting plasma around black holes and other compact objects gives rise to outflowing winds and jets is still lacking, despite decades of observations. The fact that similar processes and morphologies are observed in both X-ray binaries as well as active galactic nuclei has led to suggestions that the underlying physics could scale with black hole mass, which could provide a new handle on the problem. In the last decade, simultaneous broadband campaigns of the fast-varying X-ray binaries particularly in their microquasar state have driven the development of, and in some cases altered, our ideas about the inflow/outflow connection in accreting black holes. Specifically the discovery of correlations between the radio, infrared and X-ray bands has revealed a remarkable connectivity between the various emission regions, and argued for a more holistic approach to tackling questions about accretion. This article reviews the recent major observational and theoretical advances that focus specifically on the relation between the two "sides" of the accretion process in black holes, with an emphasis on how new tools can be derived for comparisons across the mass scale.

Accelerating AGN jets to parsec scales using general relativistic MHD simulations

“…This is similar to the distances at which the synchrotron break is estimated to occur for both AGN and X-ray binary jets (e.g., Markoff et al 2001Markoff et al , 2005Russell et al 2013;Lucchini et al 2018). The break arises when the synchrotron emission of a compact jet shifts from its characteristic power-law profile to a flat/inverted spectrum due to self-absorption, transitioning from an optically thin regime at higher frequencies to optically thick (Blandford & Königl 1979; for a review, see Markoff 2010;Romero et al 2017) and is generally attributed to non-thermal emission from particle acceleration caused by e.g., shocks (e.g., Sironi & Spitkovsky 2009) or magnetic reconnection (e.g., Spruit et al 2001;Drenkhahn & Spruit 2002;Sironi & Spitkovsky 2014;Sironi et al 2015) in the jet. Given that pinching sets off magnetic reconnection in our simulations, we suggest that the start of the pinch region may potentially be an ideal site for particle acceleration to occur for the first time and hence, can manifest itself as a break in the synchrotron spectrum.…”

VLBA images of the precessing jet of LS I +61°303

“…At ν obs , the emission of the segment will dominate, whose spectrum peaks at that frequency plus small contributions from neighboring segments (see Fig. 1 in Markoff 2010). With the engine being close to the "infraredcore", it is clear that the 3.6 cm-core can be displaced away from the orbit (as segment 2 is in Fig.…”

ALMA observations of A0620–00: fresh clues on the nature of quiescent black hole X-ray binary jets

“…It should be noted that, to first order, the jet break frequency is expected to scale inversely with the black hole mass (Falcke & Biermann 1995;Heinz & Sunyaev 2003); as jet breaks are often observed in the GHz/sub-mm regime in active galactic nuclei, they are expected to occur in the IR-optical band for 10 5−7 times lighter objects. At the same time, additional parameters are thought to affect the exact jet break frequency for a given system: e.g., the exact value is known to vary with the overall luminosity level as well as X-ray photon index (Homan & Belloni 2005;Gandhi et al 2011;Koljonen et al 2015;Vincentelli et al 2018), likely reflecting changes in the magnetic field energy density, particle density and/or mass loading at the jet base (Markoff 2010;Russell et al 2013a;Markoff et al 2015). While an optical jet break for a system at nine orders of magnitude sub-Eddington remains somewhat challenging in the context of basic scale-invariant jet models, recent developments allow for more nuanced solutions.…”