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ALMA OBSERVATION OF THE 658 GHz VIBRATIONALLY EXCITED H<sub>2</sub>O MASER IN ORION KL SOURCE I
Hirota, Tomoya,Kim, Mi Kyoung,Honma, Mareki American Astronomical Society 2016 The Astrophysical journal Vol.817 No.2
<P>We present an observational study of the vibrationally excited H2O line at 658 GHz (v(2) = 1, 1(1,0)-1(0,1)) toward Orion KL using the Atacama Large Millimeter/Submillimeter Array (ALMA). This line is clearly detected at the position of the massive protostar candidate, Source I. The spatial structure is compact, with a size of about 100 AU, and is elongated along the northeast-southwest low-velocity (18 km(-1)) bipolar outflow traced by 22 GHz H2O masers, SiO masers, and thermal SiO lines. A velocity gradient can be seen perpendicular to the bipolar outflow. The overall spatial and velocity structure seems to be analogous to that of the 321 GHz H2O maser line previously detected with ALMA and vibrationally excited SiO maser emission. The brightness temperature of the 658 GHz H2O line is estimated to be higher than 2 x 10(4) K, implying that it is emitted via maser action. Our results suggest that the 658 GHz H2O maser line is emitted from the base of the outflow from a rotating and expanding accretion disk as observed for the SiO masers and the 321 GHz H2O maser. We also search for two other H2O lines at 646 GHz (9(7,3)-8(8,0) and 9(7,2)-8(8,1)), but they are not detected in Orion KL.</P>
ALMA BAND 8 CONTINUUM EMISSION FROM ORION SOURCE I
Hirota, Tomoya,Machida, Masahiro N.,Matsushita, Yuko,Motogi, Kazuhito,Matsumoto, Naoko,Kim, Mi Kyoung,Burns, Ross A.,Honma, Mareki American Astronomical Society 2016 The Astrophysical journal Vol.833 No.2
<P>We have measured continuum flux densities of a high-mass protostar candidate, a radio source. I in the Orion. KL region (Orion Source I) using the Atacama Large Millimeter/Submillimeter Array (ALMA) at band. 8 with an angular resolution of 0 ''.1. The continuum emission at 430, 460, and 490 GHz associated with Source. I shows an elongated structure along the northwest-southeast direction perpendicular to the so-called low-velocity bipolar outflow. The deconvolved size of the continuum source, 90 au x 20 au, is consistent with those reported previously at other millimeter/submillimeter wavelengths. The flux density can be well fitted to the optically thick blackbody spectral energy distribution, and the brightness temperature is evaluated to be 700-800 K. It is much lower than that in the case of proton-electron or H-free-free radiations. Our data are consistent with the latest ALMA results by Plambeck & Wright, in which the continuum emission was proposed to arise from the edge-on circumstellar disk via thermal dust emission, unless the continuum source consists of an unresolved structure with a smaller beam filling factor.</P>