A polarimetric view of the open cluster Lyngå6 and the Cepheid TW Normæ

¹ Facultad de Ciencias Astronómicas y Geofísicas (Universidad Nacional de La Plata), Paseo del Bosque s/n, 1900, La Plata, Argentina
² Instituto de Astrofísica de La Plata (IALP, CONICET), Paseo del Bosque s/n, 1900, La Plata, Argentina
³ Member of the Carrera del Investigador Científico of CONICET
⁴ Visiting Astronomer, Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the Universities of La Plata, Córdoba, and San Juan
⁵ Instituto de Astronomía y Física del Espacio, C. C. 67 Suc. 28, 1428 Buenos Aires, Argentina

Corresponding author: H. G. Marraco, hmarraco@conae.gov.ar

Received: 19 July 2001
Accepted: 16 August 2001

Abstract

We present UBVRI polarimetric observations of stars belonging to the small open cluster Lyngå6 and of TW Nor, a Cepheid which can be seen near the center of the grouping. The wavelength of maximum polarization is computed and then analyzed in the context of its relation to the optical properties and characteristic particle size distribution of the grains responsible for the polarization. The amount and direction of linear polarization is also computed. Results indicate a mean polarization efficiency close to the value found for the interstellar medium. Two out of seven members of Lyngå6 present indications of intrinsic polarization in their measures. We conclude that part of the polarization detected in the light from members of the cluster comes from a dust cloud located in the Local arm, at a distance of about 1 kpc. In general, polarization measurements do not support the membership of TW Nor to Lyngå6.