TOWARD UNDERSTANDING THE ENVIRONMENT OF R MONOCEROTIS FROM HIGH-RESOLUTION NEAR-INFRARED POLARIMETRIC OBSERVATIONS

High-resolution H-band imaging polarimetric observations of R Mon obtained at the Canada-France-Hawaii telescope are presented. These data show a centrosymmetric pattern with elongated intensity contours mostly due to the presence of the companion R Mon B. We also consider published R-band data, which show an extended right-angle conical reflection nebula with an offset in the optical peak. We study the circumstellar environment of R Mon with a radiative transfer Monte Carlo code. The best-fitting model obtained succeeds in reproducing the characteristics seen in the data in the two bands simultaneously. The model indicates the presence of relatively small astronomical silicate grains ranging from 0.04 μm to 0.15 μm distributed into three structures: a small disk, an inner envelope, and an outer envelope. The cavity is modeled by a conical structure with a constant low density and we include a 'throat' to produce the offset of the optical peak. Our model predicts a polarization reversal by 900 between the R and H bands. Observations show that position angles parallel, perpendicular, and also at other angles to the disk can occur over time in the near-infrared.