Day 1453

Monday.

1808.05552
Least squares two-point function estimation
Tessore

The standard estimator for the 2pt function of a homogeneous and isotropic random field is a special case of a larger class of least squares estimators that interpolate the function values.  Using a different interpolation scheme, 2pt function values can be estimated at specific distances, instead of the binned averages.


1808.05886
The lensing time delay between gravitational and electromagnetic waves
Cremonese, Mörtsell

The recent detection of gravitational waves (GWs) and EM waves originating from the same source makes the start of a new multi-messenger era in astronomy.  The arrival time difference between the GW and EM signal can be used to constrain differences in their propagation speed, and thus gravitational theories.  Study to what extent a non-zero time delay can be explained by gravitational lensing when the line of sight to the source passes near a massive object.  For galaxy scale lenses, this delay becomes relevant for GWs with frequencies between 1e-6 and 1e-9 Hz, sourced by super massive binary black-holes.  In addition to GWs detectable by Pulsar Timing Arrays (PTAs), expect to find also a unique and recognizable EM signal.  Show that the delay between the GW and EM signal can be of the order of days to months; within reach of future observations. The effect may become important in future multi-messenger astronomy probing of gravitational propagation and interactions.