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 about executing normal twilight flats with no Wollaston prism and with the same filter as in the science OB. No standard stars are observed in SWP mode by the night support astronomer! The user has to provide his/her own OBs for the standard star observation, should he/she need it. The user provided standard star must not be brighter than 10.5 mag in the case 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 no real need of polarized standard stars. It is recommended to observe (at least two) unpolarized stars at different parallactic angles (e.g. alpha and alpha+45º) in order to be able to correct for the instrumental polarization and measure indipendently the polarization introduced by ISAAC and that introduced by M3. We provide below a short list of both unpolarized and polarized standard that can be used.
The following list of unpolarized standard stars is suitable for ISAAC SWP mode observations. They have been selected among the unpolarized standard stars used for FORS1 calibration plans. . They J H and K mags are from the 2MASS catalog.
|OBJ Name||RA||DEC||J||H||K||p% (J)||PAº (J)||p% (H)||PAº (H)||p% (K)||PAº (K)|