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The impact of accretion disc winds on the optical spectra of cataclysmic variables

The impact of accretion disc winds on the optical spectra of cataclysmic variables
The impact of accretion disc winds on the optical spectra of cataclysmic variables
Many high-state non-magnetic cataclysmic variables (CVs) exhibit blueshifted absorption or P-Cygni profiles associated with ultraviolet (UV) resonance lines. These features imply the existence of powerful accretion disc winds in CVs. Here, we use our Monte Carlo ionization and radiative transfer code to investigate whether disc wind models that produce realistic UV line profiles are also likely to generate observationally significant recombination line and continuum emission in the optical waveband. We also test whether outflows may be responsible for the single-peaked emission line profiles often seen in high-state CVs and for the weakness of the Balmer absorption edge (relative to simple models of optically thick accretion discs). We find that a standard disc wind model that is successful in reproducing the UV spectra of CVs also leaves a noticeable imprint on the optical spectrum, particularly for systems viewed at high inclination. The strongest optical wind-formed recombination lines are H α and He II λ4686. We demonstrate that a higher density outflow model produces all the expected H and He lines and produces a recombination continuum that can fill in the Balmer jump at high inclinations. This model displays reasonable verisimilitude with the optical spectrum of RW Trianguli. No single-peaked emission is seen, although we observe a narrowing of the double-peaked emission lines from the base of the wind. Finally, we show that even denser models can produce a single-peaked H α line. On the basis of our results, we suggest that winds can modify, and perhaps even dominate, the line and continuum emission from CVs.
accretion, accretion discs, line: profiles, radiative transfer, methods: numerical, novae, cataclysmic variables, stars: winds, outflows
0035-8711
3331-3344
Matthews, J.H.
8aa37525-32b9-460c-bb83-01c89269ac31
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Long, K.S.
839b3509-5ef3-4126-97fa-912e3357d8ef
Sim, S.A.
7df85a4e-ebca-4700-b95c-90a6427985ea
Higginbottom, N.
c542dcc3-7227-48ca-b50f-fd989eedd8fb
Matthews, J.H.
8aa37525-32b9-460c-bb83-01c89269ac31
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Long, K.S.
839b3509-5ef3-4126-97fa-912e3357d8ef
Sim, S.A.
7df85a4e-ebca-4700-b95c-90a6427985ea
Higginbottom, N.
c542dcc3-7227-48ca-b50f-fd989eedd8fb

Matthews, J.H., Knigge, C., Long, K.S., Sim, S.A. and Higginbottom, N. (2015) The impact of accretion disc winds on the optical spectra of cataclysmic variables. Monthly Notices of the Royal Astronomical Society, 450 (3), 3331-3344. (doi:10.1093/mnras/stv867).

Record type: Article

Abstract

Many high-state non-magnetic cataclysmic variables (CVs) exhibit blueshifted absorption or P-Cygni profiles associated with ultraviolet (UV) resonance lines. These features imply the existence of powerful accretion disc winds in CVs. Here, we use our Monte Carlo ionization and radiative transfer code to investigate whether disc wind models that produce realistic UV line profiles are also likely to generate observationally significant recombination line and continuum emission in the optical waveband. We also test whether outflows may be responsible for the single-peaked emission line profiles often seen in high-state CVs and for the weakness of the Balmer absorption edge (relative to simple models of optically thick accretion discs). We find that a standard disc wind model that is successful in reproducing the UV spectra of CVs also leaves a noticeable imprint on the optical spectrum, particularly for systems viewed at high inclination. The strongest optical wind-formed recombination lines are H α and He II λ4686. We demonstrate that a higher density outflow model produces all the expected H and He lines and produces a recombination continuum that can fill in the Balmer jump at high inclinations. This model displays reasonable verisimilitude with the optical spectrum of RW Trianguli. No single-peaked emission is seen, although we observe a narrowing of the double-peaked emission lines from the base of the wind. Finally, we show that even denser models can produce a single-peaked H α line. On the basis of our results, we suggest that winds can modify, and perhaps even dominate, the line and continuum emission from CVs.

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More information

Published date: 1 July 2015
Keywords: accretion, accretion discs, line: profiles, radiative transfer, methods: numerical, novae, cataclysmic variables, stars: winds, outflows

Identifiers

Local EPrints ID: 430098
URI: http://eprints.soton.ac.uk/id/eprint/430098
ISSN: 0035-8711
PURE UUID: a47630fb-adc4-498c-b2cb-02fb85a4841d

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Date deposited: 11 Apr 2019 16:30
Last modified: 11 Apr 2019 16:30

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