OPTICAL AND NEAR-INFRARED POLARIMETRY FOR A HIGHLY DORMANT COMET 209P/LINEAR

ABSTRACT We conducted an optical and near-infrared polarimetric observation of the highly dormant Jupiter-Family Comet, 209P/LINEAR. Because of its low activity, we were able to determine the linear polarization degrees of the coma dust particles and nucleus independently, that is Pn = % at = 92 2 and Pn = % at = 99 5 for the nucleus, and Pc = % at = 92 2 and % at = 99 5 for the coma. We detected no significant variation in P at the phase angle coverage of 92 2-99 5, which may imply that the obtained polarization degrees are nearly at maximum in the phase-polarization curves. By fitting with an empirical function, we obtained the maximum values of linear polarization degrees Pmax = 30.8% for the nucleus and Pmax = 29.6% for the dust coma. The Pmax of the dust coma is consistent with those of dust-rich comets. The low geometric albedo of Pv = 0.05 was derived from the slope-albedo relationship and was associated with high We examined Pmax-albedo relations between asteroids and 209P, and found that the so-called Umov law seems to be applicable on this cometary surface.