EPoS Contribution
EPoS Contribution
New Embedded Eruptive Variable YSO UKIDSS-J185318.36+012454.5

Elena Nikoghosyan
BAO, Yerevan, AM
Eruptions of young stellar objects are the phenomenon that, from the point of view of the modern theory of star formation, is the result of the variability of accretion activity. However, this event is rare. Therefore, a new outburst is always noteworthy. Nevertheless, the number of verified eruptive variable YSOs stars remains too small. However, as a result of significant developments of infrared observations that allow us to penetrate in embedded and distant star-forming regions, there has been some progress in this regard. A number of new deeply embedded eruptive variables with very steep spectral energy distributions and a higher accretion rate have been identified. Apparently, these objects are at an earlier evolutionary stage than the optically defined EXor and FUor classical eruptive subclasses. Among them there are the objects which show a mixture of characteristics of EXor and FUor objects. For this type of the eruptive YSOs the label MNOr has been proposed.
We report the discovery of a strong outburst of the embedded young stellar object UKIDSS-J185318.36+012454.5 (or G034.4035+00.2282A), located in the star-forming region associated with IRAS 18507+0121 and the ultra-compact H II region GAL 034.4+00.23. The amplitude of the outburst, which apparently started between May 2003 and April 2004, is at least ΔKs = 5.0 mag. According to the near- and mid-infrared colors and the spectral energy distribution, we classify the object as an intermediate-mass YSO with Class 0/I evolution stage and an age of < 105 yr. The ratio between the mass, total luminosity, and age of our object, as well as the disk accretion and envelope infall rates, correlates well with the several embedded eruptive variable YSOs (VVV v20, v815, VVV v405, v473, and v800). The summation of the photometric and spectral data allows classifying UKIDSS-J185318.36+012454.5 as an MNor type object.
Caption: Images of UKIDSS-J185318.36+012454.5 in the K band, obtained in 2003 (left panel) and 2006 (right panel). The position of IRAS 18507+0121 is marked by the white cross.
Collaborators:
N. Azatyan, BAO, AM
Key publication

Suggested Session: Star formation "laws" and IMF