Astrophysical Prior Information and Gravitational-wave Parameter
  Estimation
  The detection of electromagnetic counterparts to gravitational waves has
great promise for the investigation of many scientific questions. It has long
been hoped that in addition to providing extra, non-gravitational information
about the sources of these signals, the detection of an electromagnetic signal
in conjunction with a gravitational wave could aid in the analysis of the
gravitational signal itself. That is, knowledge of the sky location,
inclination, and redshift of a binary could break degeneracies between these
extrinsic, coordinate-dependent parameters and the physical parameters, such as
mass and spin, that are intrinsic to the binary. In this paper, we investigate
this issue by assuming a perfect knowledge of extrinsic parameters, and
assessing the maximal impact of this knowledge on our ability to extract
intrinsic parameters. However, we find only modest improvements in a few
parameters --- namely the primary component's spin --- and conclude that, even
in the best case, the use of additional information from electromagnetic
observations does not improve the measurement of the intrinsic parameters
significantly.
