Abstract

VEGA, E. Irene; ORSATTI, Ana María  and  MARTINEZ, Ruben E.. Multicolor U BV RI polarimetry of NGC 4755 and the β Cephei population. Rev. mex. astron. astrofis [online]. 2015, vol.51, n.1, pp.73-88. ISSN 0185-1101.

We present U BV RI polarimetric observations of 66 stars in the direction of NGG 4755, including eleven β cephei stars. About half of these variables show indications of intrinsic polarization, but according to the theory neither radial nor non-radial pulsations could cause such polarizations. From the main characteristics of their P_v vs. λ_v curves we found as a possible origin, in some cases, scattering of light in extended atmospheres and suspected binarity, in some cases. The parameters of the interstellar medium towards the cluster are P_v = 2.76 ± 0.13(%) and θ_v = 76.°6 ± 0.°9; the mean wavelength of maximum polarization amounts to 0.56 ± 0.04 µm. The value of polarization efficiency is higher than the mean, indicating a good alignment of the dust particles. A total of 25 stars were identified as members of NGG 4755; the identification task was improved through the use of polarimetric tools.

Keywords : ISM [dust]; ISM [extinction]; open clusters and associations [NGG 4755]; open clusters and associations [stars]; open clusters and associations [variables]; open clusters and associations [β Cephei].