Additional polarised standards in the fields of known bright standard stars

Abstract

We present the results based on broad-band (VRI) polarimetric observations of a number of stars that are present towards the fields of already known bright po- larised standard stars namely BD+59° 389, HD 19820, and HD 25443. These three relatively bright stars were observed continuously for various observing programs using ARIES Imaging Polarimeter (AIMPOL) attached with 1-m Sampur- nanand Telescope (ST) since 2006 to correct for any polar- isation position angle offset. Since AIMPOL is an imaging polarimeter with a field-of-view of ∼8 arcmin diameter, we could get polarisation measurements of a number of rela- tively faint stars that are present within the field-of-view of the AIMPOL towards the above three bright polarised stan- dards. Based on these compiled observations for a relatively long duration, we could examine the constancy of the degree of polarisation and position angles of them. With the help of some statistical tests, five stars in the field of BD+59° 389 and two stars in the field of HD 19820 have been identified as stars that could be used as additional polarised standard stars. Since these additional stars are relatively fainter than the known polarised standards, they could be observed with bigger aperture telescopes (like 2-m) without them getting saturated.