AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 50. High Angular Resolution Science with the NRAO Very Long Baseline Array
Display, Tuesday, June 1, 1999, 10:00am-7:00pm, Southwest Exhibit Hall

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[50.10] Protoplanetary Disk and/or Bipolar Outflow Traced by H2O Maser

V.I. Slysh, I.E. Val'tts (ASC Lebedev Physical Institute), V. Migenes (Dep. of Astronomy, University of Guanajuato), E. Fomalont (NRAO), H. Hirabayashi (ISAS), M. Inoue (NRO), T. Umemoto (NAO)

The H2O maser connected with young stellar object in the globule IC1396N has been mapped with the VLBA during its highest state of activity in June 1996. The spectrum of the H2O maser consisted of a dense group of strong low velocity features near the LSR velocity of the globule, and two high velocity features: one red-shifted to 9.3 km s-1 and the other blue-shifted to -14.1 km s-1. The map of low velocity features displays a remarkable chain of at least 8 maser spots located very close to a straight line about 15 AU in extent, with LSR velocities varying linearly along the line. The two high velocity features are offset from the low velocity group by 410 AU and 10,000 AU for the blue and red features, respectively. We discuss the three models which can describe the observed distribution of maser spots: a Keplerian disk with maser emission excited by shock waves travelling in the disk, and the high velocity features arising at the base of the molecular outflow originating from the central 4 solar masses young star or a protostar. The mass of the disk and its angular momentum are similar to those of our planetary system. It is suggested that we are observing a circumstellar accretion disk accumulating the excess angular momentum of the collapsing molecular core, which may give rise to the formation of a planetary system. This model can be tested by measurements of the proper motion and radial velocity variations of the maser spots.

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