Diffraction-limited bispectrum speckle interferometry of the Herbig Be star R Mon
Gerd Weigelt, Yuri Y. Balega, Karl-Heinz Hofmann, Thomas Preibisch
Astronomy and Astrophysics, Vol. 392, pp.937-943 (2002)
We explore the structures immediately surrounding the intermediate-mass young stellar object R Mon with bispectrum speckle interferometry, conventional near-infrared imaging and by analyzing optical HST archive data. Our near-infrared speckle images with unprecedented diffraction-limited resolution of 55 mas ( ~ 44 AU; H-band) and 76 mas ( ~ 61 AU; K-band) represent the highest resolution R Mon images obtained so far and exhibit previously unseen complex structures. While the binary companion R Mon B appears as an unresolved point source in our speckle images, the image of the primary R Mon A is marginally extended in the K-band and significantly extended in the H-band. The most prominent new feature is a bright arc-shaped structure, pointing away from R Mon in north-western direction. We interpret this feature as the surface of a dense structure near the thick circumstellar disk or torus around R Mon. Our images also reveal several twisted filaments of helical shape which are similar to the twisted filaments in the outer parts of the nebula. We identify structures which probably are responsible for casting pronounced shadows in the outer regions of the NGC 2261 reflection nebula. Finally, we discuss the relation of the observed features, in particular the arc-shaped speckle feature, to the wind and outflow activity (Herbig-Haro objects and jets) of R Mon. Part of the results presented in this paper are based on observations obtained at the German-Spanish Astronomical Centre, Calar Alto, operated by the Max-Planck-Institute for Astronomy, Heidelberg, jointly with the Spanish National Commission for Astronomy. The speckle data were collected at the Special Astrophysical Observatory with the 6 m telescope.