A Decade of Black-Hole X-ray Binary Transients
Proceedings of Science 401 (2022)
Abstract:
The last decade has seen a significant gain in both space and ground-based monitoring capabilities, producing vastly better coverage of BH X-ray binaries during their (rare) transient events. This interval included two of the three brightest X-ray outbursts ever observed, namely V404 Cyg in 2015, and MAXI J1820+070 in 2018, as well as the outburst of Swift J1357.2-0933, the first such system to show variable period optical dipping. There are now superb multi-wavelength archives of these outbursts, both photometric and spectroscopic, that show substantial outflows in the form of jets and disc winds, and X-ray spectroscopy/timing that reveals how the inner accretion disc evolves. The ground-based AAVSO optical monitoring of the MAXI J1820+070 event was the most extensive ever obtained, revealing periodic variations that evolved as it approached its state transition. These modulations were of an amplitude never seen before, and suggested the development of an irradiation-driven disc warp that persisted through the transition. All these results have demonstrated the power of extensive multi-wavelength photometric and spectroscopic monitoring on all time-scales.How Do Magnetic Field Models Affect Astrophysical Limits on Light Axion-like Particles? An X-Ray Case Study with NGC 1275
The Astrophysical Journal American Astronomical Society 930:1 (2022) 90
The X-ray disc/wind degeneracy in AGN
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 513:1 (2022) 551-572
A persistent ultraviolet outflow from an accreting neutron star binary transient.
Nature 603:7899 (2022) 52-57
Abstract:
All disc-accreting astrophysical objects produce powerful disc winds. In compact binaries containing neutron stars or black holes, accretion often takes place during violent outbursts. The main disc wind signatures during these eruptions are blue-shifted X-ray absorption lines, which are preferentially seen in disc-dominated 'soft states'1,2. By contrast, optical wind-formed lines have recently been detected in 'hard states', when a hot corona dominates the luminosity3. The relationship between these signatures is unknown, and no erupting system has as yet revealed wind-formed lines between the X-ray and optical bands, despite the many strong resonance transitions in this ultraviolet (UV) region4. Here we report that the transient neutron star binary Swift J1858.6-0814 exhibits wind-formed, blue-shifted absorption lines associated with C IV, N V and He II in time-resolved UV spectroscopy during a luminous hard state, which we interpret as a warm, moderately ionized outflow component in this state. Simultaneously observed optical lines also display transient blue-shifted absorption. Decomposing the UV data into constant and variable components, the blue-shifted absorption is associated with the former. This implies that the outflow is not associated with the luminous flares in the data. The joint presence of UV and optical wind features reveals a multi-phase and/or spatially stratified evaporative outflow from the outer disc5. This type of persistent mass loss across all accretion states has been predicted by radiation-hydrodynamic simulations6 and helps to explain the shorter-than-expected duration of outbursts7.How do Magnetic Field Models Affect Astrophysical Limits on Light Axion-like Particles? An X-ray Case Study with NGC 1275
ArXiv 2202.08875 (2022)