Infrared polarimetry of the microquasars H1743-322, XTE J1550-564 and GRO J1655-40
Laboratoire Leprince-Ringuet, UMR 7638 CNRS, École Polytechnique, 91128 Palaiseau, France e-mail: firstname.lastname@example.org
2 Institut d'Astrophysique de Paris, UMR 7095 CNRS, Université Pierre & Marie Curie - Paris 6, 98bis Bd Arago, 75014 Paris, France
3 AIM - Astrophysique Interactions Multi-échelles (UMR 7158 CEA/CNRS/Université Paris 7 - Denis Diderot), CEA Saclay, DSM/DAPNIA/Service d'Astrophysique, Bât. 709, L'Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France
Accepted: 3 August 2006
Aims.The optical/IR emission from X-ray binaries can be intrinsically polarised because of light scattered within the system or because there is significant synchrotron emission at high frequencies from a compact jet. We report on polarised light observations of three microquasars (X-ray binaries with radio jets).
Methods.Ks band polarimetric observations were obtained at the ESO NTT using SOFI. The linear polarisation of the three systems is derived relative to that of other stars in the field-of-view, so as to distinguish intrinsic polarisation from interstellar polarisation.
Results.H1743-322 was observed in outburst in 2003 and 2004. We measure a linear polarisation of % comparable to that of other nearby stars. The polarisation is very likely interstellar, consistent with the large extinction () along the line-of-sight. GRO J1655-40 was observed in quiescence and shows no evidence for intrinsic polarisation. XTE J1550-564 was observed during a weak X-ray outburst. It shows a higher polarisation (at the 2.5σ level) than neighbouring stars within . Further studies are needed to establish the nature of this possible intrinsic polarisation.
Key words: techniques: polarimetric / binaries: close / infrared: stars / X-rays: binaries
© ESO, 2006