Bibcode
Russell, David M.; Fender, Rob P.
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 387, Issue 2, pp. 713-723.
Advertised on:
6
2008
Número de citas
43
Número de citas referidas
34
Descripción
Near-infrared (NIR) and optical polarimetric observations of a selection
of X-ray binaries are presented. The targets were observed using the
Very Large Telescope and the United Kingdom Infrared Telescope. We
detect a significant level (3σ) of linear polarization in four
sources. The polarization is found to be intrinsic (at the >3σ
level) in two sources; GRO J1655-40 (~4-7 per cent in the H and
Ks bands during an outburst) and Sco X-1 (~0.1-0.9 per cent
in the H and K bands), which is stronger at lower frequencies. This is
likely to be the signature of optically thin synchrotron emission from
the collimated jets in these systems, whose presence indicates that a
partially ordered magnetic field is present at the inner regions of the
jets. In Sco X-1, the intrinsic polarization is variable (and sometimes
absent) in the H and K bands. In the J band (i.e. at higher
frequencies), the polarization is not significantly variable and is
consistent with an interstellar origin. The optical light from GX 339-4
is also polarized, but at a level and position angle consistent with
scattering by interstellar dust. The other polarized source is SS 433,
which has a low level (0.5-0.8 per cent) of J-band polarization, likely
due to local scattering. The NIR counterparts of GRO J0422+32, XTE
J1118+480, 4U 0614+09 and Aql X-1 (which were all in or near quiescence)
have a linear polarization level of <16 per cent (3σ upper
limit, some are <6 per cent). We discuss how such observations may be
used to constrain the ordering of the magnetic field close to the base
of the jet in such systems.
Based on observations collected at the European Southern Observatory,
Chile, under ESO Programme IDs 076.D-0497 and 275.D-5062.
E-mail: davidr [at] science.uva.nl (davidr[at]science[dot]uva[dot]nl) (DMR); rpf [at] phys.soton.ac.uk (rpf[at]phys[dot]soton[dot]ac[dot]uk) (RPF)