Thermal and radiation driving can produce observable disc winds in hard-state X-ray binaries
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 492:4 (2020) 5271-5279
Stratified disc wind models for the AGN broad-line region: ultraviolet, optical and X-ray properties
ArXiv 2001.03625 (2020)
Hot, dense He II outflows during the 2017 outburst of the X-ray transient Swift J1357.2−0933
Monthly Notices of the Royal Astronomical Society: Letters Oxford University Press 489:1 (2019) L47-L52
Abstract:
Time-resolved SALT spectra of the short-period, dipping X-ray transient, Swift J1357.2−0933, during its 2017 outburst has revealed broad Balmer and He II λ4686 absorption features, blueshifted by ∼600 km s−1. Remarkably these features are also variable on the ∼500 s dipping period, indicating their likely association with structure in the inner accretion disc. We interpret this as arising in a dense, hot (≳30 000 K) outflowing wind seen at very high inclination, and draw comparisons with other accretion disc corona sources. We argue against previous distance estimates of 1.5 kpc and favour a value ≳6 kpc, implying an X-ray luminosity LX ≳ 4 × 1036 erg s−1. Hence it is not a very faint X-ray transient. Our preliminary 1D Monte Carlo radiative transfer and photoionization calculations support this interpretation, as they imply a high intrinsic LX, a column density NH ≳ 1024 cm−2, and a low covering factor for the wind. Our study shows that Swift J1357.2−0933 is truly remarkable amongst the cohort of luminous, Galactic X-ray binaries, showing the first example of He II λ4686 absorption, the first (and only) variable dip period and is possibly the first black hole ‘accretion disc corona’ candidate.Cosmic ray acceleration by shocks: spectral steepening due to turbulent magnetic field amplification
Monthly Notices of the Royal Astronomical Society Oxford University Press 488*:2 (2019) 2466-2472
Abstract:
We show that the energy required to turbulently amplify magnetic field during cosmic ray (CR) acceleration by shocks extracts energy from the CR and steepens the CR energy spectrum.Do reverberation mapping analyses provide an accurate picture of the broad-line region?
Monthly Notices of the Royal Astronomical Society Oxford University Press 488:2 (2019) 2780-2799