# Reanalysis of Dispersion Measure Periodicity for Fast Radio Bursts and Perytons¶

# A Blog post and Open Notebook¶

tl;dr:

- Analysis with FRB DMs as of November 2015 shows that whatever small significance for periodicity in the DM distribution has totally disappeared.
- This notebook is available as a "binder" that can be run with modifications (or new FRBs!) at http://mybinder.org/repo/caseyjlaw/FRB-dm-periodicity.

The study of Fast Radio Bursts (FRBs) was stirred by an article on the arxiv by Hippke et al (http://arxiv.org/pdf/1503.05245v2.pdf). This article performed a meta-analysis of the Dispersion Measures (DMs; the frequency-dependent time of arrival of the impulse) and arrival times of published FRBs. That analysis had flaws, as I described in an earlier post and in a Dinah review I posted (http://dinah-peer-review.appspot.com).

However, the knee-jerk reaction against the Hippke et al analysis was unfair to some degree as there was a modest (~5%) chance that there was a periodicity in the measured DMs. Also, disconcertingly, that underlying period was similar to that revealed by a similar analysis on the apparent DM of Perytons, a related, but decidedly non-astrophysical phenomenon (http://labs.adsabs.harvard.edu/adsabs/abs/2015MNRAS.451.3933P).

Here, we perform the DM periodicity analysis again with the latest and greatest sample of measured DMs. For bonus fun, we built and tested this notebook as a "binder", a tool for reproducible science.

Primary motivating questions:

- Is there a significant "periodicity" in the dispersion measures of FRBs?
- Are there shared properties (particularly dispersion measure) between Perytons and FRBs?

```
import numpy as n
import os, glob
from bokeh.plotting import figure, show
from bokeh.io import output_notebook, gridplot
from bokeh.charts.utils import cycle_colors
output_notebook()
```