A universal relation for the propeller mechanisms in magnetic rotating stars at different scales
Journal
Date Issued
2018
Author(s)
Abstract
Accretion of matter onto a magnetic, rotating object can be strongly affected by the interaction with its magnetic field. This occurs in a variety of astrophysical settings involving young stellar objects, white dwarfs, and neutron stars. As matter is endowed with angular momentum, its inflow toward the star is often mediated by an accretion disc. The pressure of matter and that originating from the stellar magnetic field balance at the magnetospheric radius: at smaller distances the motion of matter is dominated by the magnetic field, and funnelling towards the magnetic poles ensues. However, if the star, and thus its magnetosphere, is fast spinning, most of the inflowing matter will be halted at the magnetospheric radius by centrifugal forces, resulting in a characteristic reduction of the accretion luminosity. The onset of this mechanism, called the propeller, has been widely adopted to interpret a distinctive knee in the decaying phase of the light curve of several transiently accreting X-ray pulsar systems. By comparing the observed luminosity at the knee for different classes of objects with the value predicted by accretion theory on the basis of the independently measured magnetic field, spin period, mass, and radius of the star, we disclose here a general relation for the onset of the propeller which spans about eight orders of magnitude in spin period and ten in magnetic moment. The parameter-dependence and normalisation constant that we determine are in agreement with basic accretion theory.
Volume
610
Start page
1
Issn Identifier
0004-6361
Ads BibCode
2018A&A...610A..46C
Rights
open.access
File(s)![Thumbnail Image]()
Loading...
Name
aa30769-17.pdf
Description
Pdf editoriale
Size
808.8 KB
Format
Adobe PDF
Checksum (MD5)
cbab25876a40d504e783311ac2f1946a