2007A&A...462..621V

We present (UBVRI) multicolor linear polarimetric data for 31 of the brightest stars in the area of the open cluster NGC 5749 considered to study the properties of the interstellar medium (ISM) towards the cluster. Our data yield a mean polarization percentage of P_V∼1.7%, close to the polarization value produced by the ISM with normal efficiency (P(%)=3.5E_(B–V)^0.8) for a mean color excess of E_B–V=0.42. The mean angle of polarization vectors, θ=74°, agrees quite well with the expected angle produced by dust particles aligned in the direction of the galactic disk (and the magnetic field) in the region. Our analysis indicates that the visual absorption affecting the stars in NGC 5749 is partially produced by a dust layer located up to 300pc from the Sun and also by a second layer of dust closer to the cluster (located at least at 700pc). The observed photometry and our polarization data are consistent with the existence of dust within the cluster. We also show in this work how polarimetry could be an excellent technique for identifying nonmember stars.