2 Observations

The stars to be observed polarimetrically were selected from the work of Walker ([1961]) covering the central core and some dusty regions north of it, where Turner ([1974]) detected about a dozen stars suffering of an abnormal extinction law.

Observations in the UBVR $_{\rm KC}I_{\rm KC}$ bands (KC: Kron-Cousins, $\lambda_{ U_{\rm eff}}$ = 0.36 $\rm\mu m$, FWHM = 0.05 $\rm\mu m$; $\lambda_{ B_{\rm eff}}$ = 0.44 $\rm\mu m$, FWHM = 0.06 $\rm\mu m$; $\lambda_{ V_{\rm eff}}$ = 0.53 $\rm\mu m$, FWHM = 0.06 $\rm\mu m$; $\lambda_{ R_{\rm eff}}$ = 0.69 $\rm\mu m$, FWHM = 0.18 $\rm\mu m$; $\lambda_{ I_{\rm eff}}$ = 0.83 $\rm\mu m$, FWHM = 0.15 $\rm\mu m$) were carried out using the five-channel photopolarimeter of the Torino Astronomical Observatory, attached to the 2.15 m telescope at the Complejo Astronómico El Leoncito (San Juan, Argentina). They were performed on 4 nights (August 26/29) in 1995 and 2 nights (June 18/19) in 1996, both runs of suitable quality. Standard stars for null polarization and for the zero point of the polarization position angle were taken from Clocchiatti & Marraco ([1988]).

Table 1 lists on its left side, for the 39 observed stars, the percentage polarization ($P_\lambda$), the position angle of the electric vector ( $\theta_\lambda$) in the equatorial coordinate system and their respective mean errors for each filter. We indicate also the number of independent integrations with each filter. Star identifications are taken from the work of Walker ([1961]).