Astronomy and Astrophysics – Astrophysics – High Energy Astrophysical Phenomena
Scientific paper
2009-05-27
Astron.Astrophys. 502:871-881,2009
Astronomy and Astrophysics
Astrophysics
High Energy Astrophysical Phenomena
11 pages, 11 figures, accepted for publication in Astronomy and Astrophysics
Scientific paper
10.1051/0004-6361/200911619
Hydrogen and/or helium accreted by a neutron star from a binary companion may undergo thermonuclear fusion. At different mass accretion rates different burning regimes are discerned. Theoretical models predict helium fusion to proceed as a thermonuclear runaway for accretion rates below the Eddington limit and as stable burning above this limit. Observations, however, place the boundary close to 10% of the Eddington limit. We study the effect of rotationally induced transport processes on the stability of helium burning. For the first time detailed calculations of thin helium shell burning on neutron stars are performed using a hydrodynamic stellar evolution code including rotation and rotationally induced magnetic fields. We find that in most cases the instabilities from the magnetic field provide the dominant contribution to the chemical mixing, while Eddington-Sweet circulations become important at high rotation rates. As helium is diffused to greater depths, the stability of the burning is increased, such that the critical accretion rate for stable helium burning is found to be lower. Combined with a higher heat flux from the crust, as suggested by recent studies, turbulent mixing could explain the observed critical accretion rate. Furthermore, close to this boundary we find oscillatory burning, which previous studies have linked to mHz QPOs. In models where we continuously lower the heat flux from the crust, the period of the oscillations increases by up to several tens of percents, similar to the observed frequency drift, suggesting that this drift could be caused by the cooling of deeper layers.
in 't Zand J. M. J.
Keek Laurens
Langer Norbert
No associations
LandOfFree
The effect of rotation on the stability of nuclear burning in accreting neutron stars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The effect of rotation on the stability of nuclear burning in accreting neutron stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The effect of rotation on the stability of nuclear burning in accreting neutron stars will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-528297