James C. A. Miller Jones

We present IRAM 30 m observations aimed at identifying potential outflow–interstellar medium interaction sites in the vicinity of the black hole X-ray binary Cygnus X-1, which displays persistent relativistic jets and a prominent stellar wind. Using this data set, we construct molecular line emission maps, identifying a never-before-seen molecular structure potentially linked to X-ray-binary-driven feedback. This structure, surrounding the source, exhibits properties consistent with an interaction powered primarily by the stellar wind of the massive stellar companion and further sculpted by the relativistic jets. Our results indicate that multiple outflow mechanisms (stellar winds and relativistic jets) may simultaneously be shaping the interstellar medium around Cygnus X-1 and that molecular line imaging can help to disentangle complex feedback processes in environments where multiple outflows take place.

Relativistic jets from supermassive black holes in active galactic nuclei are amongst the most powerful phenomena in the universe. Similar jets from stellar-mass black holes offer a chance to study the phenomena on accessible observation time scales. However, such comparative studies across black hole masses and time scales remain hampered by the long-standing perception that stellar-mass black hole jets are in a less relativistic regime. Here, we show the detection of two distinct, relativistic jet ejections from the Galactic black hole X-ray binary 4U 1543−47 during a single outburst, with radio interferometry monitoring observations. Our measurements reveal a likely Lorentz factor of approximately 8 and a minimum of 4.6 at launch with 95% confidence, demonstrating that stellar-mass black holes in X-ray binaries can launch jets as relativistic as those seen in active galactic nuclei.

We present a detailed radio study of the tidal disruption events (TDEs) AT 2020zso and AT 2021sdu. Both exhibit transient radio emission beginning shortly after optical discovery and persisting for several years. For AT 2020zso, we identify two distinct radio flares. The first is detected in the radio ∼22 days after the optical peak, reaching a maximum of ∼1 yr post-discovery before fading. The second flare appears ∼800 days after discovery and results in the brief presence of two distinct components in the radio spectra, providing strong evidence for physically separate outflows. Both flares are consistent with nonrelativistic outflows, with velocities of v ≈ 0.1–0.2 c and energies of E ∼ 10 ⁴⁹ erg, propagating through a Bondi-like circumnuclear medium. Our analysis supports a scenario in which the first outflow is accretion driven, launched while the TDE disk is accreting at a relatively high Eddington fraction, whereas the second outflow is associated with a transition to an advection-dominated accretion flow. In contrast, the radio emission from AT 2021sdu is best explained by a slower ( v ≈ 0.03 c ), less energetic outflow ( E ∼ 10 ⁴⁸ erg), combined with diffuse, nonvariable host emission that becomes dominant ∼500 days after discovery. Assuming free expansion, we infer an outflow launch date preceding the optical discovery date. This suggests that the outflow may originate from either the unbound stellar debris ejected during disruption or, alternatively, from a decelerating outflow. Our findings demonstrate the diversity of outflow properties in TDEs and highlight the observational challenges of interpreting late-time radio variability in the presence of host galaxy contamination.

Black hole X-ray binaries (BH XRBs) launch powerful relativistic jets during bright outburst phases. The properties of these outflows change dramatically between different spectral-accretion states. Compact jets are observed during the hard state and are quenched during the soft state, while discrete ejecta are mainly launched during the hard-to-soft state transition. Currently, we do not understand what triggers the formation and/or destruction of compact jets or the launch of discrete ejecta. In this context, finding a unique link between the jet evolution and the properties of the X-ray emission, such as its fast variability, would imply major progress in our understanding of the fundamental mechanisms that drive relativistic outflows in BH XRBs. Here we show that a brief, strong radio re-brightening during a predominantly soft state of the BH XRB MAXI J1348–630 was contemporaneous with a significant increase in the X-ray root-mean-square (rms) variability observed with the Neutron Star Interior Composition Explorer (NICER) in 2019. During this phase, the variability displayed significant changes and, at the same time, MAXI J1348–630 launched two relativistic discrete ejecta that we detected with the MeerKAT and ATCA radio-interferometers. We propose that short-lived compact jets were reactivated during this excursion to the hard-intermediate state and were switched off before the ejecta launch, a behavior that has been very rarely observed in these systems. Interestingly, with the caveat of gaps in our radio and X-ray coverage, we suggest a tentative correspondence between the launch of ejecta and the drop in X-ray rms variability in this source, while other typical X-ray signatures associated with discrete ejections are not detected. We discuss how these results provide us with insights into the complex dynamic coupling between the jets and hot corona in BH XRBs.

We present the longest and the densest quasi-simultaneous radio, X-ray, and optical campaign of the black hole low-mass X-ray binary GX 339−4, covering five years of weekly GX 339−4 monitoring with MeerKAT, Swift/XRT, and MeerLICHT, respectively. Complementary high-frequency radio data with the Australia Telescope Compact Array are presented to track in more detail the evolution of GX 339−4 and its transient ejecta. During the five years, GX 339−4 has been through two ‘hard-only’ outbursts and two ‘full’ outbursts, allowing us to densely sample the rise, quenching, and re-activation of the compact jets. Strong radio flares were also observed close to the transition between the hard and the soft states. Following the radio flare, a transient optically thin ejection was spatially resolved during the 2020 outburst, and was observed for a month. We also discuss the radio/X-ray correlation of GX 339−4 during this five year period, which covers several states in detail from the rising phase to the quiescent state. This campaign allowed us to follow ejection events and provide information on the jet proper motion and its intrinsic velocity. With this work, we publicly release the weekly MeerKAT L-band radio maps from data taken between 2018 September and 2023 October.

We present Atacama Large Millimeter/submillimeter Array observations aimed at identifying potential jet–interstellar medium (ISM) interaction sites in the vicinity of the transient black hole X-ray binaries MAXI J1348−630 and MAXI J1820+070, both of which have recently undergone an outburst, and displayed powerful large-scale jets. Using this dataset, we construct molecular line emission maps. By analyzing the morphological, spectral, and kinematic properties of the detected emission, we identify a molecular structure that provides compelling evidence for a jet-driven cavity in the local environment of MAXI J1348−630 but find no significant emission in the local environment of MAXI J1820+070. We use the properties of the detected molecular emission surrounding MAXI J1348−630 to constrain the jet power, finding our results to be consistent with other independent studies of this source, and further validating the utility of astrochemistry for constraining jet energetics. Additionally, our findings provide the first assessment on the formation timescales for jet–ISM interaction regions in the transient black hole X-ray binary population.

For over a decade, both theoretical predictions and observational studies have suggested that ω Centauri ( ω Cen), the most massive Milky Way globular cluster, might harbor an intermediate-mass black hole (IMBH). Recently, identification of fast-moving stars in the core of ω Cen provided the strongest evidence to date for the presence of such an IMBH. One of the key questions in the study of IMBHs is their accretion efficiency, which determines their radio and X-ray signatures. We investigate the accretion signature of the IMBH in ω Cen with ultradeep radio continuum observations of the central region of the cluster. Using approximately 170 hr of Australia Telescope Compact Array observations, we achieve a root-mean-square noise of 1.1 μ Jy at 7.25 GHz, making this the most sensitive radio image of the cluster to date. We detect no radio emission at any of the proposed centers of the cluster, imposing stringent constraints on the presence of an accreting IMBH in ω Cen. Considering the fundamental plane of black hole activity, our findings indicate that the accretion efficiency around the black hole is exceptionally low (with a conservative 3 σ upper limit of ϵ ≲ 4 × 10 ⁻³ ).

Jets provide an important channel for kinetic feedback from accreting black holes into their environment, without which models of the formation of large-scale structure in the universe fail to reproduce the observed properties of galaxies. Hence, an accurate measurement of jet power is critical for understanding black hole growth through accretion and also for quantifying the impact of kinetic feedback. However, the absence of instantaneous jet power measurements has precluded direct comparisons with the accretion luminosity, forcing kinetic feedback models to rely on ad hoc assumptions about how much jet power is released per accreted amount of mass. Here we report the detection of stellar wind-induced bending of the jets in the black hole X-ray binary Cygnus X-1, using 18 years of high-resolution radio imaging. By modeling jet-wind interactions, we determine the current kinetic instantaneous power of the jet to be log$_{10}(L_{\rm jet}/{\rm erg\,s}^{-1}) = 37.3_{-0.2}^{+0.1}$, comparable to the accretion energy determined from its bolometric X-ray luminosity. This result critically places prevailing assumptions about the energetics of black hole powered jets in both galaxy formation simulations, and in scaling models of black hole accretion, on a firm empirical footing.