Astrometry of H2O Masers in Nearby Star-Forming Regions with VERA III. IRAS22198+6336 in Lynds1204G

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We present results of multi-epoch VLBI observations with VERA (VLBI Exploration of Radio Astrometry) of the 22GHz H₂O masers associated with a young stellar object (YSO) IRAS22198$+$6336 in a dark cloud, L1204G. Based on phase-referencing VLBI astrometry, we derived an annual parallax of IRAS22198$+$6336 to be 1.309±0.047mas, corresponding to the distance of 764±27pc from the Sun. Although the most principal error source of our astrometry is attributed to the internal structure of the maser spots, we successfully reduced the errors in the derived annual parallax by employing position measurements for all of the 26 detected maser spots. Based on this result, we reanalyzed the spectral energy distribution of IRAS22198$+$6336 and found that the bolometric luminosity and total mass of IRAS22198$+$6336 are 450L_ and 7M_, respectively. These values are consistent with an intermediate-mass YSO deeply embedded in the dense dust core, which has been proposed to be an intermediate-mass counterpart of a low-mass Class 0 source. In addition, we obtained absolute proper motions of the H₂O masers for the most blue-shifted components. We propose that the collimated jets aligned along the east-west direction are the most plausible explanation for the origin of the detected maser features.