VERA and ALMA observations of the H2O supermaser burst in Orion KL

• DOI: 10.1093/pasj/psu110
• Publication Date: 2014-12-10T06:55:13Z
• Authors: Tomoya Hirota; Masato Tsuboi; Yasutaka Kurono; Kenta Fujisawa; Mareki Honma; Mi Kyoung Kim; Hiroshi Imai; Yoshinori Yonekura
• Keywords: Outflow; Submillimeter Array; Maxima; Very-long-baseline interferometry

The 22 GHz H2O maser in Orion KL has shown extraordinary burst events 1979-1985 and 1998-1999, sometimes called supermaser. We have conducted monitoring observations of the supermaser using VERA, VLBI Exploration Radio Astrometry, current third since 2011 March. Three flux maxima are detected 2012 with rising falling timescales 2-7 months. Time variations seem symmetric for all active phases. maximum total density 135000 Jy is observed June while it still one order magnitude lower than those previous bursts. consists two spatially different components at velocities. They elongated along a northwest-southeast direction perpendicular to low-velocity outflow driven by Source I. Proper motions features respect I measured toward west southwest directions, almost parallel outflow. linewidth show an anti-correlation as expected unsaturated emission. located close methylformate (HCOOCH3) line continuum emission peaks Compact Ridge ALMA. broader velocity range weak HCOOCH3 position would be evidence shock front. On other hand, 321 not It can explained qualitatively theoretical excitation models without conditions. Our results support scenario that excited dense gas interacting Ridge. extremely high its time variation phases could beaming effect during amplification process rather changes physical