Bibcode
Migliari, S.; Miller-Jones, J. C. A.; Russell, D. M.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 415, Issue 3, pp. 2407-2416.
Advertised on:
8
2011
Citations
49
Refereed citations
42
Description
We investigate the role of the compact object in the production of jets
from neutron star X-ray binaries. The goal is to quantify the effect of
the neutron star spin, if any, in powering the jet. We compile all the
available measures or estimates of the neutron star spin frequency in
jet-detected neutron star X-ray binaries. We use as an estimate of the
ranking jet power for each source the normalization of the power law
which fits the X-ray/radio and X-ray/infrared luminosity correlations
Lradio/IR∝LΓX (using
infrared data for which there is evidence for jet emission). We find a
possible relation between spin frequency and jet power (Spearman rank 97
per cent), when fitting the X-ray/radio luminosity correlation using a
power law with slope 1.4; Γ= 1.4 is observed in 4U 1728-34 and is
predicted for a radiatively efficient disc and a total jet power
proportional to the mass accretion rate. If we use a slope of 0.6, as
observed in Aql X-1, no significant relation is found. An indication for
a similar positive correlation is also found for accreting millisecond
X-ray pulsars (Spearman rank 92 per cent), if we fit the X-ray/infrared
luminosity correlation using a power law with slope 1.4. While our use
of the normalization of the luminosity correlations as a measure of the
ranking jet power is subject to large uncertainties, no better proxy for
the jet power is available. However, we urge caution in
over-interpreting the spin-jet power correlations, particularly given
the strong dependence of our result on the (highly uncertain) assumed
power-law index of the luminosity correlations (which span less than 3
orders of magnitude in X-ray luminosity). We discuss the results in the
framework of current models for jet formation in black holes and young
stellar objects and speculate on possible different jet production
mechanisms for neutron stars depending on the accretion mode.