The polarization of starlight in NGC 654 and IC 5146

Optical polarimetric study of open clusters: distribution of interstellar matter towards NGC 654

“…In Table 3, we present previous polarization measurements of stars in the direction of NGC 645 carried out by Samson (1976) and Pandey et al (2005). Samson (1976) observed 14 stars in the direction of NGC 654 using plates with IIa0 emulsion. The IIa0 emulsion has a red cutoff similar to Johnson B band.…”

“…The limiting magnitude was B = 15 mag. In column 1, we give the identification numbers which are adopted from Samson (1976) and Pandey et al (2005). Columns 2, 3, 4, 5, 6, 7, 8, & 9 give P % & θ in B, V, R & I filters, respectively.…”

“…The errors of measurements are given in parenthesis wherever available. Samson (1976) gives polarization in magnitudes (p). We converted p to P % using the relation P % = 46.05p (Whittet 1992).…”

“…We converted p to P % using the relation P % = 46.05p (Whittet 1992). The position angles given by Samson (1976) are w.r.t the east, as deduced from the star #54. We transformed the values to w.r.t the north.…”

“…First polarimetric measurements of the stars towards NGC 654 were made by Samson (1976) with plates using IIa0 emulsion (IIa0 emulsion has a red cutoff similar to Johnson B band). Samson (1976) found certain stars to be very conspicuous because they differed in magnitude or direction of polarization, or both, from the surrounding stars. The star #37 for e.g., was unusual in both the magnitude and direction of polarization.…”