A rapidly-changing jet orientation in the stellar-mass black hole V404 Cygni

Abstract: Powerful relativistic jets are one of the main ways in which accreting black holes provide kinetic feedback to their surroundings. Jets launched from or redirected by the accretion flow that powers them should be affected by the dynamics of the flow, which in accreting stellar-mass black holes has shown increasing evidence for precession due to frame dragging effects that occur when the black hole spin axis is misaligned with the orbital plane of its companion star. Recently, theoretical simulations have suggested that the jets can exert an additional torque on the accretion flow, although the full interplay between the dynamics of the accretion flow and the launching of the jets is not yet understood. Here we report a rapidly changing jet orientation on a timescale of minutes to hours in the black hole X-ray binary V404 Cygni, detected with very long baseline interferometry during the peak of its 2015 outburst. We show that this can be modelled as Lense-Thirring precession of a vertically-extended slim disk that arises from the super-Eddington accretion rate. Our findings suggest that the dynamics of the precessing inner accretion disk could play a role in either directly launching or redirecting the jets within the inner few hundred gravitational radii. Similar dynamics should be expected in any strongly-accreting black hole whose spin is misaligned with the inflowing gas, both affecting the observational characteristics of the jets, and distributing the black hole feedback more uniformly over the surrounding environment.

Rapidly-Changing Jet Orientation in V404 Cygni: Observations and Implications

The research paper titled "A rapidly-changing jet orientation in the stellar-mass black hole V404 Cygni" elucidates a remarkable phenomenon observed during the 2015 outburst of the black hole X-ray binary V404 Cygni. This study reveals the rapid reorientation of jets on timescales of minutes to hours, suggesting a dynamic interaction between the jets and the accretion flow driven by the Lense-Thirring precession of the disk.

The observational study was conducted using the Very Long Baseline Array (VLBA), which provided high-angular resolution radio monitoring. The key finding is the detection of a change in the orientation of the jets, recorded over a range of $-30.6$\degree\ to $+5.6$\degree\ east of north. Such swift variations were unprecedented and indicative of significant dynamical processes at play in the accretion disk-jet systems of black holes.

The research attributes these variations to Lense-Thirring precession, wherein the inner region of a vertically-extended slim disk precesses due to frame-dragging effects from the stellar mass black hole. The phenomena were observed at a super-Eddington accretion rate, suggesting the influence of high accretion rates in modifying the dynamics of jet launching or redirection.

Notably, the study details twelve discrete ejection components captured on June 22, 2015, showcasing a series of variably-directed ejecta that move ballistically outward before subsiding. The authors hypothesize that the inner disk's precession could redirect the jets, an assertion supported by the observed inconsistencies in inclination angles derived from the ejecta pairs (N2/S2, N3/S3, N6/S6).

From a theoretical standpoint, these observations challenge existing models of accretion dynamics and jet emission, suggesting that not only magnetic field lines or the black hole spin but also instabilities in the accretion disk geometry can exert significant influence on jet behavior. The results imply that precessing jets should be anticipated in any black hole system with a significant spin-orbit misalignment, potentially affecting the morphology and detectable signatures of such jets across the electromagnetic spectrum, as well as their kinetic feedback on the host galaxy environment.

The implications of this research extend to broader cosmological phenomena, such as ultraluminous X-ray sources and AGN feedback mechanisms. The precession observed could contribute to the repetitive and isotropic dispersal of energy and matter in galactic environments, offering insights into the mitigation of cooling flows in galaxy clusters and alignment discrepancies in black hole merger events that originate from isolated binary evolution.

Future avenues for exploration include more detailed modeling of the interplay between relativistic jets and accretion flow dynamics and extending these observations to other systems with similar or differing accretion regimes. Such studies could refine our understanding of accretion physics and provide critical parameters for simulating gravitational waveforms from merging black holes. Moreover, continued development in observational technology, such as enhanced very long baseline interferometry, will enable more precise measurements of these phenomena, enriching models sheathing the enigmatic processes occurring in these extreme astrophysical environments.