Polarimetric Standard Stars
Currently, ISAAC calibration plans do not support observations in SWP mode. In case of service mode SWI Polarimetric observations the night support astronomer will only take care aboutexecuting normal twilight flats with no Wollaston prism and with the same filter as in the science OB. No standard starsare observed in SWP mode by the night support astronomer! The user has to provide his/her own OBs for the standard starobservation, should he/she need it. The user provided standard star must not be brighter than 10.5 mag in thecase of broad band filters, and not brighter than 7.5 mag in the case of narrow band filters.
Given that there is only a Wollaston prism in ISAAC, there is noreal need of polarized standard stars. It is recommended to observe (at least two) unpolarized stars atdifferent parallactic angles (e.g. alpha and alpha+45º) in order to be able to correct for the instrumental polarization and measureindipendently the polarization introduced by ISAAC and that introduced by M3. We provide below a short list of both unpolarized and polarizedstandard that can be used.
The following list of unpolarized standard stars is suitable for ISAAC SWPmode observations. They have been selected among the unpolarized standard stars used for FORS1 calibration plans. . They J Hand K mags are from the 2MASS catalog.