Hawkesbury Radio Astronomy Observatory

Vela Pulsar Observations

Observing PSR B0833-45 with a Small Aperture Antenna


Science Results

In addition to daily observation data some minor science results can be derived from the observations of the Vela pulsar.  These include detection of glitch events and generation of ephemerides. Glitches are a sudden spin-up of the rotating neutron star which interrupt the normal gradual spin-down due to radiation energy loss.

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 5σ and 6σ thresholds of the HawkRAO observational data - see table below.

Detection Thresholds

The minimum spin-up jump in ppm to declare a 'glitch event' at the 5σ and 6σ significance levels of the observational data (last update MJD 58024).  These thresholds will change over time due to better S/Ns (new antenna array), more data points and improvements in period measurements due to software upgrades.

Significance Level Current Threshold (ppm)
0.79
0.95

Detected Events

Epoch, magnitude and significance level of candidate glitch events.

Event Epoch Magnitude (ppm) Significance Level
- - -

Glitch Events Summary

No glitch events above the 5σ/6σ significance levels have been detected since MJD 57874 (01 May 2017 UTC).

Ephemerides

Ephemerides are derived from HawkRAO observational data.

Second-Order Ephemeris Derived from Complete Data Set

After each observation a second-order ephemeris is calculated from a least-squares fit on all data to date.  The epoch of this ephemeris is the start MJD.  This second-order ephemeris is detailed at the top of the daily science result text file.

Spot Cross-check Against Ephemeris from a Professional Radio Astronomy Source

As a cross-check a calculation can be made for the HawkRAO observational second-order ephemeris for a future epoch (e.g., 58050) and the result compare to that from a professional ephemeris (courtesy of Jim Palfreyman - UTAS).

Observatory Epoch of Ephemeris Target MJD Elapsed Days Spin Frequency
HawkRAO 57874 58050 176 11.1860218686
UTAS 57883 58050 167 11.1860224571

The difference between the prediction of spin frequency for MJD 58050 made by the HawkRAO ephemeris and the UTAS ephemeris is...

((11.1860224571 / 11.1860218686 ) - 1) x 10-6 = 0.0526 ppm.

This is well within the error measurement band and is a good result. An agreement within ±0.5 ppm is considered to be a good result.

Note that the above 'future epoch' will eventually become a past epoch - so the above numbers are a one-off cross-check taken mid-September 2017 and may not agree with the current values.

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.