Expansion of the R4 Water Maser Arc Near Cepheus A HW 2

Details Expansion of the R4 Water Maser Arc Near Cepheus A HW 2 Expansion of the R4 Water Maser Arc Near Cepheus A HW 2

2002-11-20

arxiv.org/abs/astro-ph/0211462v2

Astrophys.J. 586 (2003) 306-318

Astronomy and Astrophysics

Astrophysics

16 pages, 12 figures. Accepted for publication in the Astrophysical Journal. Uses emulateapj5.sty. Updated: removed previews f

Scientific paper

10.1086/346266

We present new (April 2000) MERLIN observations of the H2O masers located near the protostar Cepheus A HW2. The MERLIN observations detect many of the structures found in earlier (1996) VLBA observations of Torrelles and collaborators, and the changed positions of these structures are compatible with the VLBA proper motions and astrometric uncertainties. The radius of curvature of the R4 structure of maser arcs appears to have grown by a factor of two, and the displacement of the arcs between 1996 and 2000 are compatible with expansion about a common center. In addition, the MERLIN observations detect red-shifted masers not previously found; taken with the newly discovered masers, the R4 structure now resembles patchy emission from an elliptical ring. We demonstrate that a simple bow-shock model cannot simultaneously account for the shape and the velocity gradient of the R4 structure. A model involving a slow, hydromagnetic shock propagating into a rotating, circumstellar disk better describes the maser spot kinematics and luminosities. In this model, the central mass is 3 solar masses, and we demonstrate that the mass of the disk is negligible in comparison. The expansion velocity of the post-shock gas, roughly 5 km / s, is slow compared to the average shock velocity (roughly 13 km / s) suggesting that the post-shock gas is magnetically supported with a characteristic field strength of roughly 30 mG. We speculate that the expanding maser rings R4 and R5 may be generated by periodic, instability-driven winds from young stars that periodically send spherical shocks into the surrounding circumstellar material.

Affiliated with

Also associated with

No associations

Rating

Expansion of the R4 Water Maser Arc Near Cepheus A HW 2 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Expansion of the R4 Water Maser Arc Near Cepheus A HW 2, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Expansion of the R4 Water Maser Arc Near Cepheus A HW 2 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-54939