Revisiting LS I +61 303 with VLBI astrometry
Abstract
We conducted multi-epoch VLBA phase reference observations of LS I +61 303 in order to study its precessing radio jet. Compared to similar observations in 2006, we find that the observed elliptical trajectory of emission at 8.4 GHz repeats after the 9-year gap. The accurate alignment of the emission patterns yields a precession period of 26.926 +- 0.005 d, which is consistent with that determined by Lomb-Scargle analysis of the radio light curve. We analytically model the projection on the sky plane of the peak position of a precessing, synchrotron-emitting jet, which traces an elliptical trajectory on the sky. Comparing the simulation with the VLBA astrometry we improve our knowledge of the geometry of the system.We measure the LS I +61 303 absolute proper motion to be -0.150 +- 0.006 mas/yr eastward and -0.264 +- 0.006 mas/yr northward. Removing Galactic rotation, this reveals a small, < 20 km/s, non-circular motion, which indicates a very low kick velocity when the black hole was formed.
Keywords
Cite
@article{arxiv.1711.07598,
title = {Revisiting LS I +61 303 with VLBI astrometry},
author = {Y. W. Wu and G. Torricelli-Ciamponi and M. Massi and M. J. Reid and B. Zhang and L. Shao and X. W. Zheng},
journal= {arXiv preprint arXiv:1711.07598},
year = {2017}
}
Comments
10 pages, 10 Figures, 1 Table, MNRAS accepted 2017 November 19