* Astronomy

Title: Trigonometric Distance and Proper Motion of IRAS 20056+3350: Massive Star Forming Region on the Solar Circle
Author: Ross A. Burns, Takumi Nagayama, Toshihiro Handa, Toshihiro Omodaka, Akiharu Nakagawa, Hiroyuki Nakanishi, Masahiko Hayashi, Makoto Shizugami

We report our measurement of the trigonometric distance and proper motion IRAS 20056+3350, obtained from the annual parallax of H2O masers. Our distance of D = 4.69 +0.65-0.51 kpc, which is more than two times larger than the near kinematic distance adopted in the literature, places IRAS 20056+3350 at the leading tip of the Local arm, and proximal to the Solar circle. Using our distance we re-evaluate past observations to reveal IRAS 20056+3350 as a site of massive star formation at a young stage of evolution. This result is consistent with the spectral energy distribution of the source evaluated with published photometric data from UKIDSS, WISE, AKARI, IRAS and sub-millimetre continuum. Both analytical approaches reveal the luminosity of the region to be 2.4 x 10^4 L_o, and suggest that IRAS 20056+3350 is forming an embedded star of 16 solar masses. We estimated the proper motion of IRAS 20056+3350 to be (µ_alphacos delta, _delta) = (-2.62±0.33, -5.65±0.52) mas yr^-1 from the group motion of H2O masers, and use our results to estimate the angular velocity of Galactic rotation at the Galactocentric distance of the Sun, Omega₀=28.71±0.63 km s^-1 kpc^-1, which is consistent with the values obtained for other tangent point and Solar circle objects.

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