Effects of radiation field geometry on line driven disc winds

Dyda, Sergei; Proga, Daniel

doi:10.1093/mnras/sty2478

Cited by 5 publications

(1 citation statement)

References 17 publications

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“…This approach allows a more accurate calculation of M (t) and also allows the direction of the acceleration vector in each band to be different; the net acceleration is then simply the vector sum over all three bands. This flexibility allows us to take account of complex illumination geometry which is important for line driven winds in CVs and AGN where the wind probably arises above the UV bright portion of the disk (Dyda & Proga 2018).…”

Section: Methodsmentioning

confidence: 99%

Thermal and radiation driving can produce observable disc winds in hard-state X-ray binaries

Higginbottom

Knigge

Long

et al. 2020

Monthly Notices of the Royal Astronomical Society

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X-ray signatures of outflowing gas have been detected in several accreting black-hole binaries, always in the soft state. A key question raised by these observations is whether these winds might also exist in the hard state. Here, we carry out the first full-frequency radiation hydrodynamic simulations of luminous (L = 0.5 L Edd ) black-hole X-ray binary systems in both the hard and the soft state, with realistic spectral energy distributions (SEDs). Our simulations are designed to describe X-ray transients near the peak of their outburst, just before and after the hard-to-soft state transition. At these luminosities, it is essential to include radiation driving, and we include not only electron scattering, but also photoelectric and line interactions. We find powerful outflows withṀ wind 2Ṁ acc are driven by thermal and radiation pressure in both hard and soft states. The hard-state wind is significantly faster and carries approximately 20 times as much kinetic energy as the soft-state wind. However, in the hard state the wind is more ionized, and so weaker X-ray absorption lines are seen over a narrower range of viewing angles. Nevertheless, for inclinations 80 • , blue-shifted wind-formed Fe xxv and Fe xxvi features should be observable even in the hard state. Given that the data required to detect these lines currently exist for only a single system in a luminous hard state -the peculiar GRS 1915+105 -we urge the acquisition of new observations to test this prediction. The new generation of X-ray spectrometers should be able to resolve the velocity structure.

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Section: Methodsmentioning

confidence: 99%

Thermal and radiation driving can produce observable disc winds in hard-state X-ray binaries

Higginbottom

Knigge

Long

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Stratified disc wind models for the AGN broad-line region: ultraviolet, optical, and X-ray properties

Matthews

Knigge

Higginbottom

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The origin, geometry and kinematics of the broad line region (BLR) gas in quasars and active galactic nuclei (AGN) are uncertain. We demonstrate that clumpy biconical disc winds illuminated by an AGN continuum can produce BLR-like spectra. We first use a simple toy model to illustrate that disc winds make quite good BLR candidates, because they are selfshielded flows and can cover a large portion of the ionizing flux-density (φ H -n H ) plane. We then conduct Monte Carlo radiative transfer and photoionization calculations, which fully account for self-shielding and multiple scattering in a non-spherical geometry. The emergent model spectra show broad emission lines with equivalent widths and line ratios comparable to those observed in AGN, provided that the wind has a volume filling factor of f V 0.1. Similar emission line spectra are produced for a variety of wind geometries (polar or equatorial) and for launch radii that differ by an order of magnitude. The line emission arises almost exclusively from plasma travelling below the escape velocity, implying that 'failed winds' are important BLR candidates. The behaviour of a line-emitting wind (and possibly any 'smooth flow' BLR model) is similar to that of the locally optimally-emitting cloud (LOC) model originally proposed by Baldwin et al (1995), except that the gradients in ionization state and temperature are large-scale and continuous, rather than within or between distinct clouds. Our models also produce UV absorption lines and X-ray absorption features, and the stratified ionization structure can partially explain the different classes of broad absorption line quasars.

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Line-driven winds from variable accretion discs

Anthony

Dyda

Reynolds

2023

Monthly Notices of the Royal Astronomical Society

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We use numerical hydrodynamics simulations to study line driven winds launched from an accreting α −disc. Building on previous work where the driving radiation field is static, we compute a time-dependent radiation flux from the local, variable accretion rate of the disc. We find that prior to the establishment of a steady-state in the disc, variations of $\sim 15\%$ in disc luminosity correlate with variations of ∼2 − 3 in the mass flux of the wind. After a steady state is reached, when luminosity variations drop to $\sim 3\%$, these correlations vanish as the variability in the mass flux is dominated by the intrinsic variability of the winds. This is especially evident in lower luminosity runs where intrinsic variability is higher due to a greater prevalence of failed winds. The changing mass flux occurs primarily due to the formation of clumps and voids near the disc atmosphere that propagate out into the low velocity part of the flow, a process that can be influenced by local variations in disc intensity. By computing the normalised standard deviation of the mass outflow, we show that the impact of luminosity variations on mass outflow is more visible at higher luminosity. However, the absolute change in mass outflow due to luminosity increases is larger for lower luminosity models due to the luminosity-mass flux scaling relation becoming steeper. We further discuss implications for CVs and AGN and observational prospects.

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Effects of radiation field geometry on line driven disc winds

Cited by 5 publications

References 17 publications

Thermal and radiation driving can produce observable disc winds in hard-state X-ray binaries

Thermal and radiation driving can produce observable disc winds in hard-state X-ray binaries

Stratified disc wind models for the AGN broad-line region: ultraviolet, optical, and X-ray properties

Line-driven winds from variable accretion discs

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