Ryan Shannon

@astromattmiles.bsky.social (Swinburne, now Vanderbilt) for his thesis “Millisecond pulsar timing and gravitational wave searches with the MeerKAT radio telescope” supervised by @ryanmshannon.bsky.social has been awarded the Charlene Heisler Prize for the most outstanding PhD thesis in astronomy.

With use of radio interferometers and new search strategies, these slowish transients/periodic sources are being found at increasing rate and bound to have a few/many more surprises in store.

This image shows the cover image for the September issue of Nature Astronomy, featuring the ASKAP telescope pointing at a night sky that is split half and half. The left half features a pulsar, with curling purple magnetic field lines; the right half a white dwarf against a starry backdrop.

The winner of cover of the year for 2024 is the September cover connected to the Caleb, Lenc et al. paper! www.nature.com/articles/s41... Congratulations to all involved, particularly Carl Knox @ozgrav.bsky.social and @csiro.bsky.social #NAstroCoverComp #astronomy

Nice way to commute to a conference.

A Lower Mass Estimate for PSR J0348+0432 Based on CHIME/Pulsar Precision Timing The binary pulsar J0348+0432 was previously shown to have a mass of approximately 2\,${\rm M_\odot}$, based on the combination of radial-velocity and model-dependent mass parameters derived from high-...

Our CHIME/Pulsar data imply that a pulsar thought to be very massive... isn't. The previous mass measurement relied on white-dwarf modeling; now we have measured the orbital period decay due to gravitational-wave emission. 🔭

arxiv.org/abs/2412.02850

‘A ship on the ocean of reality’: New maps show universe is even weirder than we thought A decade ago, astronomers observed gravitational waves for the first time. What has emerged since is a picture of the universe as a vast ocean – dark and powerful.

MPTA results written up in today's The Age/Morning Herald as well
www.smh.com.au/national/a-s... @astromattmiles.bsky.social @pinkastrophysicist.bsky.social

Off to the OzGrav retreat/ECR workshop in Brisbane. I'm on a panel in the ECR workshop tomorrow on "making the most of OzGrav". Hopefully I can deliver some insight!

I made this website for the MeerKAT PTA. Check it out! mpta-gw.github.io

Searches for signatures of ultra-light axion dark matter in polarimetry data of the European Pulsar Timing Array Ultra-light axion-like particles (ALPs) can be a viable solution to the dark matter problem. The scalar field associated with ALPs, coupled to the electromagnetic field, acts as an active birefringent...

Similar results from the EPTA as well today:
arxiv.org/abs/2412.02232

First Pulsar Polarization Array Limits on Ultralight Axion-like Dark Matter We conduct the first-ever Pulsar Polarization Array (PPA) analysis to detect the ultralight Axion-Like Dark Matter (ALDM) using the polarization data of 22 millisecond pulsars from the third data rele...

Another day, another PTA result. This from Murriyang:

A novel way to search for axion dark matter by looking for fluctuations in polarisation position angle in pulsars
arxiv.org/abs/2412.02229

You can read @astromattmiles.bsky.social and @pinkastrophysicist.bsky.social's conversation piece here:
theconversation.com/to-map-the-v...

It's been an epic adventure so far for the MPTA. There are more questions to answer!

The good news is that with additional observations we should be able to develop better models for the data, which combined with longer timing baselines such make for an even more sensitive data set.

The evidence for the correlations depends a lot on the model assumptions. We think this is due to the short nature of the MPTA data set.

The data set produced and searched by @astromattmiles.bsky.social show evidence for gravitational waves like other PTA experiments. This includes evidence for Helling-Downs-like correlations

From the 2.5 to 4.5 year data sets, the noise has become more pronounced and prevelent in the pulsar timing data sets.

As data started to accumulate, we started seeing noise in the pulsar timing residuals of the best pulsars. The noise could be consistent with a gravitational wave background.

We then embarked on regular observations of the largest sample of millisecond pulsars possible. This would ensure our sensitivity increased quickly with time. This would become the MeerKAT Pulsar Timing Array (MPTA).

MeerTime MSP timing started in 2019 with a census of the southern millisecond pulsars, led by Swinburne PhD student Renee Spiewak.

When we started MSP precision timing with MeerKAT in 2018, we knew it would be a fantastic telescope for a pulsar timing array, but did not know when it would become sensitive to gravitational waves. The timing baseline with MeerKAT would always be much shorter than other established PTAs.

For the past few years I've been leading the first gravitational wave searches with the MeerKAT Pulsar Timing Array (mpta-gw.github.io/index.html).

It's been an incredibly rewarding experience, and today the research is published!