Science Results

In addition to daily observation data some minor science results can be derived from the observations of the Vela pulsar.  These include the generation of ephemerides* (which can be viewed in a daily science result text file) and the detection of glitch events. Glitches are a sudden spin-up of the rotating neutron star which interrupt the normal gradual spin-down due to radiation energy loss (see the graphic at the bottom of this page).

* the ephemerides published here are limited in accuracy due to low signal-to-noise and TCXO clock accuracies.  They are of general interest only and should not be used for detailed analyses or investigations.

Glitch Events

Observed spin-ups which can be reasonably classified as glitch events at HawkRAO are those observed positive deviations from the predicted spin frequency which exceed the current 6σ threshold of the HawkRAO observational data.

Detection Threshold

'Detection threshold' refers to the minimum spin-up jump (in ppm) needed to declare a 'glitch event' at the 6σ significance level of the observational data.  This threshold will change over time due to better S/Ns (new antenna array), more data points and improvements in period measurements due to software upgrades. Currently the 6σ threshold is < 1 ppm.

Detected Events

Epoch, magnitude and significance level of candidate glitch events.

Event Epoch Magnitude (ppm) Significance Level
58515.5947 - 58516.5503 2.3 28.7

Glitch Events Summary

A glitch event above the 6σ significance level has been detected MJD 58516 (02 February 2019 UTC).


Note: Ephemerides are derived from HawkRAO observational data and are limited to the accuracy of those observations.

Second-Order Ephemeris Derived from Complete Data Set

After each observation a second-order ephemeris is calculated from a least-squares fit on data from a chosen start MJD to date.  The epoch of this ephemeris is that start MJD.  This second-order ephemeris is detailed at the top of the daily science result text file. Below this data is the current second-order ephemeris used for predicting the fold period.  When the difference between the two ephemerii exceeds 0.1 ppm, the current ephemeris is updated to the latest ephemeris - except after a glitch event.  In that case the pre-glitch ephemeris is locked in and used to track the post-glitch recovery.

First-Order Ephemerides Derived from 28 Day Data Subsets (EPOCH = Start MJD)

Below the second-order ephemeris entry in the daily science result text file are first-order ephemerides calculated from a least-squares fit of 28 day blocks of data. First-order fits are consistent with the smaller number of data points analysed (compared to the full data set second-order fit).

NOTE: the first-order results in the daily science result text file are newest to oldest (top to bottom). Examining F0 from bottom to top shows the gradual spin-down of the Vela pulsar as determined by HawkRAO observational data.

Plot of Vela Pulsar Barycentric Spin Down

From HawkRAO observations a plot is made of the observed barycentric spin down of Vela over time - restarted from MJD 58344 (14th August 2018) with data from the 4 yagi array.

NOTE: refresh this page in your browser to get the latest plot.

HawkRAO Observatory Status

It should be noted that the 'bumps' on the plot are not intrinsic to the Vela pulsar, but are noise on the observation spin frequency measurements made at HawkRAO.  The step change at 58515 is a 'glitch' event.

Looking for Vela Glitches

The spin down for the Vela pulsar is ~ -45 ppm/year. A large Vela glitch is about 1 to 3 ppm and so should be visible in the above plot as a step change upwards in frequency. To observe such a Vela glitch in my data is a primary aim of these observations. A glitch has occurred at MJD 58515.

Look here under 'B0833-45' for the glitch history of Vela.

Previous Spin Down Graphics

Here is the graphic from data obtained from the single yagi array covering from MJD 57874 to MJD 58344.

The above graphic shows the steady spin down of the Vela pulsar over ~1.3 years.