1997A&A...325L..29S

The superluminal source GRO J1655-40 (Nova Scorpii) has been observed in July 1996, when in active phase at X-ray energies, with the multichannel photopolarimeter (UBVRI) of the Torino Observatory, using the 2.15-m telescope of Complejo Astronomico El Leoncito (Argentina). A significant amount of intrinsic linear polarization (>3%) has been detected in the VRI bands, with the polarization direction parallel to the accretion disk plane. The possible origin of the polarized light and its implications on the structure of the system are shortly discussed.