2015/01/15 by Safonov, Boris
#FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Instrumentation and Methods for Astrophysics (astro-ph.IM) #Solar and Stellar Astrophysics (astro-ph.SR)
paper · doi:10.48550/arxiv.1501.03807
A method for measuring the difference between centroids of polarized flux and total flux of an astronomical object - \it polaroastrometry - is proposed. The deviation of the centroid of flux corresponding to Stokes parameter Q or U from the centroid of total flux multiplied by dimensionless Stokes parameter q or u respectively, was used as a signal. The efficiency of the method is demonstrated on the basis of observations made in the V band by using an instrument combining features of a two-beam polarimeter with a rotating half-wave plate and a speckle interferometer. The polaroastrometric signal noise is 60-70 μas rms for a total number of accumulated photoelectrons Ne of 109 from a 70-cm telescope; this corresponds to a total integration time of 500 sec and an object magnitude V=6 mag. At smaller Ne the noise increases as ≈ 1.7′′/√(Ne), while at larger Ne it remains the same owing to imperfection of the half-wave plate. For main sequence stars that are unpolarized and polarized by interstellar dust and the Mira type variable R Tri the signal was undetectable. For the Mira type variable χ Cyg the polaroastrometric signal is found to be 310±70 and 300±70 μas for Stokes Q and U respectively; for o Cet these values are 490±100 and 1160±100 μas. The significant value of the polaroastrometric signal provides evidence of the asymmetry of the polarized flux distribution.