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Fri Feb 05, 2021

MINBAR burst interface visualisation

The web interface to the MINBAR burst sample is the result of a collaboration with the Monash eResearch Centre. The interface offers data selection and filtering tools, as well as output as ASCII for offline analysis and basic plotting.

We'd always envisaged offering more visualisation capabilities, but had not managed to implement them, until now. When you search the burst interface, you'll see a "wiki" link for each entry. Clicking on this link will bring up a page listing all the analysis results for this event, along with a dynamic plot of the burst lightcurve, and link to the time-resolved spectroscopy (where available). Click here (#2582) for a beautiful example from GX 17+2.

The same lightcurve files are now also accessible via the Python repository, using the get_lc method. We're also working on a method to return the time-resolved spectroscopy.

Labels: 2021, /thermonuclear bursts

Thu Apr 30, 2020

MINBAR paper accepted!

In late February we submitted the paper describing data release 1 (DR1) of the Multi-Instrument Burst Archive (MINBAR) to Astrophysical Journal Supplements. In a remakably quick turnaround we got a referee's report in less than a month, and the lightly revised version of the paper is now accepted!

Accompanying the paper is the online repository hosted at Monash's Bridges (formerly figshare) service. Here you can download the ASCCI files with the complete contents of the catalog, and (in future) will also provide links to software used to access and analyse the data.

Another way to access the data is via the web interface at, which allows basic searching and plotting facility, and you can download subsets of the data for offline analysis too.

Read the paper (arXiv:2003.00685)

Labels: 2020, /thermonuclear bursts

Fri Jun 01, 2018

A new burst oscillation source

The legacy of NASA's Rossi X-ray Timing Explorer continues to grow with the discovery of another burst oscillation in archival data from bursts observed more than 10 years ago, from the faint transient SAX J1810.8--2609. These burst oscillations, revealed by the careful work of Anya Bilous, confirm the spin frequency of the neutron star in this system at 532 Hz (that's an amazing 532 rotations every second!). This discovery adds to only a few tens of such measurements amongst the more than 100 known bursting sources. Anya's paper is now accepted by ApJ.

A Millisecond Oscillation in the Bursting X-Ray Flux of SAX J1810.8-2609 (Bilous et al. 2018) via NASA ADS

Labels: 2018, /thermonuclear bursts

Mon Apr 09, 2018

The influence of stellar spin on thermonuclear runaways

Many burst sources exhibit inexplicable decreases in burst rate even as the accretion rate increases. However, not all burst sources show the same type of behaviour, which hasn't been understood to date. Using the MINBAR sample, we measured the burst rate as a function of accretion rate, from seven neutron stars with known spin rates. At the highest accretion rates, the burst rate is lower for faster spinning stars. The observations imply that fast (> 400 Hz) rotation encourages stabilization of nuclear burning, suggesting a dynamical dependence of nuclear ignition on the spin rate. This dependence is unexpected, because faster rotation entails less shear between the surrounding accretion disk and the star. Although we don't yet fully understand this behaviour, it's hoped that further analysis and simulations will help to explain it. Our paper has now been accepted by ApJL.

Read the paper arXiv:1804.03380

Labels: 2018, /thermonuclear bursts

Tue Mar 20, 2018

Simulating X-ray bursts during a transient accretion event

Thermonuclear burst modelling has to date focused on stable accretion rates, but bursts are also observed during episodes of transient accretion. The accretion-powered millisecond pulsar SAX J1808.4—3658 exhibited four helium-rich X-ray bursts during the outburst of 2002 October. Monash student Zac Johnston undertook the first multizone simulations of X-ray bursts throughout the outburst, incorporating a time-varying accretion rate, to try to match the observations. The model, with an accreted hydrogen fraction of X = 0.44 and a CNO metallicity of 0.02, reproduces the observed burst arrival times and fluences well, and offers the prospects of more detailed future simulations of such outbursts. Zac's paper reporting the modeling has now been accepted by MNRAS.

Read the paper arXiv:1711.03970

Labels: 2018, /thermonuclear bursts

Fri Dec 15, 2017

Thermonuclear bursts in the spotlight

It's been a few years now since a review of thermonuclear bursts came out, so a little while ago Tomaso Belloni and Mariano Mendez commissioned Laurens Keek and I to write one. It's a big job to try to cover the literature in such a broad field, and this took (unfortunately) a lot longer than we expected. Tomaso and Mariano were very patient, and I'm pleased to announce that the review is finally ready! You can read it for yourself on the arXiv, or wait for it as part of "Timing Neutron Stars: Pulsations, Oscillations and Explosions", in Springer's ASSL series, edited by Tomaso and Mariano

Read the paper arXiv:1712.06227

Labels: 2017, /thermonuclear bursts

Wed Nov 29, 2017

Cracking the code of burst rates

It's been a long-standing mystery, how for some burst sources, the burst rate decreases even as the accretion rate increases. Theory and numerical models both predict that as you dial up the accretion rate, the burst ignition point should be reached earlier and earlier (up to the point when burning becomes stable and bursts stop), so that the burst rate should always increase. Yuri Cavecchi recently came up with an alternative explanation, related to the way that the burst ignition point moves from the equator to higher latitudes at higher accretion rates. If this movement is sufficiently fast, a decrease in burst rate can result even as the accretion rate continues to increase. Yuri's paper (also with longtime burst expert Anna Watts) was just accepted by ApJ

Read the paper arXiv:1711.04389

Labels: 2017, /thermonuclear bursts

Tue Sep 05, 2017

Analysing the cooling tails of thermonuclear bursts

When the upper layer of an accreting neutron star experiences a thermonuclear runaway of helium and hydrogen, it exhibits an X-ray burst with a cool-down phase of typically 1 minute. Analysis of light curves of 1254 X-ray bursts observed by the Rossi X-ray Timing Explorer shows that the decay is described as a power-law with index in the range 1.3—2.1, with a Gaussian component also required for half of the bursts. The Gaussian appears consistent with being due to the rp process, which consists of rapid proton captures and slow beta-decays of proton-rich isotopes, and is expected to be prominent in bursts with a significant fraction of hydrogen in the fuel. The Gaussian fluence fraction suggests that the layer where the rp process is active is underabundant in H by a factor of at least five with respect to cosmic abundances. Jean's paper reporting the analysis is now accepted by A&A.

Read the paper arXiv:1708.08644

Labels: 2017, /thermonuclear bursts