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Astron. Astrophys. 339, 575-586 (1998)

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6. Summary and conclusions

In this paper, we present a kinematical study of the molecular and atomic gas of the bipolar outflow associated to HD 200775. Our results can be summarized as follows:

  • The star is located in a biconical cavity of [FORMULA] 1.5 pc [FORMULA] 0.8 pc. The shape of this cavity, as observed in 12CO and 13CO emissions, suggests that it has been excavated by a bipolar outflow. Within the cavity the gas is mainly atomic.

  • There is no evidence for high velocity gas within the cavity. Two HI filaments are detected adjacent to the walls of the cavity in the eastern lobe. A bow shock is found at the tip of one of these filaments. These filaments are very likely high velocity atomic gas that is outflowing at the edges of the cavity. We have not detected any HI filaments in the western lobe.

  • The spatial distribution of the material around the exciting star is not symmetric. The extinction from the star to the western lobe seems to be higher than towards the eastern one. This asymmetric distribution of matter around the star is very likely the responsible of the higher dust temperature found in the eastern lobe and of the asymmetric spatial distribution of the HI emission.

  • We propose that the outflow associated with HD 200775 is in the latest stage of its evolution. Although it was clearly bipolar in previous evolutionary stages, now it is very likely driven by an isotropic wind. To the west, this wind collides with a dense wall producing a cometary outflow.

  • The asymmetric distribution of matter around the star is easily explained if the star has moved away from its initial position during the outflow evolution.

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© European Southern Observatory (ESO) 1998

Online publication: October 21, 1998