Astrometry of the stellar image of U Her amplified by the circumstellar 22 GHz water masers
W. H. T. Vlemmings, H. J. van Langevelde, P. J. Diamond
Abstract
The 22 GHz H2O masers in the circumstellar envelope of the Mira variable star U Her have been observed with MERLIN using a phase referencing technique to determine accurate astrometric positions. The positions were compared with the optical positions obtained with the Hipparcos satellite to an accuracy of 18 mas. The absolute radio position of the brightest H2O maser spot is found to match the optical position, indicating that this spot is the stellar image amplified by the maser screen in front of it. The occurrence of an amplified image in the 22 GHz maser can be used to accurately determine the positions of the H2O with respect to the star as well as with respect to the SiO and OH masers. Our observations seem to indicate that the star is not in the centre of the distribution of maser spots, which has been interpreted as a ring.
Create a lesson
Related papers
On binary pulsars and the force of gravity
Davor Palle
Tidal torques. A critical review of some techniques
Michael Efroimsky, James G. Williams
Dynamics of a Spherical Accretion Shock with Neutrino Heating and Alpha-Particle Recombination
Rodrigo Fernández, Christopher Thompson
Asymptotically FRW black holes
J. T. Firouzjaee, Reza Mansouri
Reaction of Accretion Disks to Abrupt Mass Loss During Binary Black Hole Merger
Sean M. O'Neill, M. Coleman Miller, Tamara Bogdanovic et al.
A Gamma-Ray Burst/Pulsar for Cosmic-Ray Positrons with a Dark Matter-like Spectrum
Kunihito Ioka