Dead discs, unstable discs and the stars they surround
Strong stellar magnetic fields significantly alter the behaviour of surrounding accretion discs. Recent work has demonstrated that at low accretion rates a large amount of mass can remain confined in the disc, contrary to the standard assumption that the magnetic field will expel the disc in an out...
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doaj-93c498a09eb74f92979e7fee6c0b25252021-08-02T17:24:24ZengEDP SciencesEPJ Web of Conferences2100-014X2014-01-01640100310.1051/epjconf/20136401003epjconf_mag2013_01003Dead discs, unstable discs and the stars they surroundD’Angelo Caroline0Instituut Anton Pannekoek, University of Amsterdam Strong stellar magnetic fields significantly alter the behaviour of surrounding accretion discs. Recent work has demonstrated that at low accretion rates a large amount of mass can remain confined in the disc, contrary to the standard assumption that the magnetic field will expel the disc in an outflow (the “propeller regime”). These “dead discs” often become unstable, causing cycles of accretion onto the central star. Here I present the main predictions of this model, and argue that it provides a good explanation for the peculiar behaviour seen in several accreting sources with strong magnetic fields. I will focus in particular on three accreting millisecond X-ray pulsars: SAX J1808.4-3658, NGC 6440 X-2 and IGR J00291+5934. These sources all show low-frequency quasi-periodic oscillations consistent with a variable accretion rate, as well as unusual outburst patterns that suggest gas is confined in the inner disc regions during quiescence. http://dx.doi.org/10.1051/epjconf/20136401003 |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
D’Angelo Caroline |
spellingShingle |
D’Angelo Caroline Dead discs, unstable discs and the stars they surround EPJ Web of Conferences |
author_facet |
D’Angelo Caroline |
author_sort |
D’Angelo Caroline |
title |
Dead discs, unstable discs and the stars they surround |
title_short |
Dead discs, unstable discs and the stars they surround |
title_full |
Dead discs, unstable discs and the stars they surround |
title_fullStr |
Dead discs, unstable discs and the stars they surround |
title_full_unstemmed |
Dead discs, unstable discs and the stars they surround |
title_sort |
dead discs, unstable discs and the stars they surround |
publisher |
EDP Sciences |
series |
EPJ Web of Conferences |
issn |
2100-014X |
publishDate |
2014-01-01 |
description |
Strong stellar magnetic fields significantly alter the behaviour of surrounding accretion discs. Recent work has demonstrated that at low accretion rates a large amount of mass can remain confined in the disc, contrary to the standard assumption that the magnetic field will expel the disc in an outflow (the “propeller regime”). These “dead discs” often become unstable, causing cycles of accretion onto the central star. Here I present the main predictions of this model, and argue that it provides a good explanation for the peculiar behaviour seen in several accreting sources with strong magnetic fields. I will focus in particular on three accreting millisecond X-ray pulsars: SAX J1808.4-3658, NGC 6440 X-2 and IGR J00291+5934. These sources all show low-frequency quasi-periodic oscillations consistent with a variable accretion rate, as well as unusual outburst patterns that suggest gas is confined in the inner disc regions during quiescence.
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url |
http://dx.doi.org/10.1051/epjconf/20136401003 |
work_keys_str_mv |
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