A complete homogeneous CO survey of northern FU Ori-type objects
- Dr. Péter ÁBRAHÁM
- Dr. Péter ÁBRAHÁM (Konkoly Observatory)
FU Orionis-type stars (FUors) are young stellar objects experiencing large optical outbursts due to highly enhanced accretion from the circumstellar disk onto the star. FUors are often surrounded by massive envelopes, which have a significant role in the outburst mechanism. Conversely, the subsequent eruptions might gradually clear up the obscuring envelope material and drive the protostar on its way to become a disk-only T Tauri star. We conducted a homogeneous survey of seven FUor-type object using the IRAM Plateau de Bure Interferometer and the IRAM 30 m radio telescope. We mapped the spatial and velocity structure of the 13CO and C18O emission using the interferometer, and made a spectral survey of millimeter molecular lines with the single-dish antenna. We detected strong, spectrally and spatially resolved 13CO and C18O emission in all cases. Interestingly, CO emission is usually not centered on the stellar position, but appears to be brightest at some distance from the central source, indicating that photodissociation of CO by the UV photons from the bright erupting source may play a role. Most of the observed sources show a complex velocity structure. The single-dish maps show emission from a wealth of lines: 13CO, C18O, C17O, CS, C2S, HC3N, CN, and SO. Some of these lines come from the FUor envelopes, while others are clearly associated with filaments or clumps in the surrounding interstellar matter. The maps of the molecular emission show different brightness distributions suggesting differences in the chemistry and/or excitation conditions.