While examining RXTE data for the MINBAR project two summers ago, Jean in 't Zand unexpectedly discovered a brand-new bursting source, XMMU J181227.8—181234. Now PhD student Adelle Goodwin's paper on the source has been accepted by MNRAS. The source is quite unusual; distant and hence low-intensity, but apparently a high accretion rate leading to frequent (but weak) bursts. The shape of the bursts strongly implies H-poor accreted composition, but we also found evidence for short recurrence-time bursts, which previously have been seen only in H-rich accretors. Hopefully the source will go into outburst again sometime soon and we can gather more information on it's properties.

Read the paper (MNRAS 486, 4149, 2019)

Labels: 2019, /postgrads

The 5^th Australia-China Workshop on Astrophysics was held in Healesville, VIC at RACV's Country Club resort this April. The meeting continues a series of events intended to foster cooperation between the two countries, and as my first attendance, I was very impressed with the level of cooperation alredy. A host of prominent Chinese and Australian astronomers were in attendance, and presentations were also made by students undertaking projects enabled made possible via cooperative programs. I gave a talk on X-ray binaries and the possibilities for joint observational programs, particularly with Insight-HXMT and the proposed eXTP. Exciting times ahead for cross-country cooperation!

Labels: 2019, /meetings

Longtime collaborator and friend of bursts Yuri Cavecchi visited Monash this month, supported by the MoCA Distinguished Visitor Program. Yuri and I have been working for a few years now on the global properties of thermonuclear bursts, particuarly the ignition conditions and how they respond to changes in accretion rate, motivated by observations with MINBAR. Yuri had already come up with a possible explanation for the drop in burst rates that is observed as accretion rates increase in some sources; during the visit we plan to work on matching the models in more detail to the observations. Stay tuned for exciting results coming soon!

Labels: 2019, /visits

PhD student Adelle Goodwin has been working hard trying to reconcile results of our 1-D time-dependent thermonuclear burst code Kepler with those of a much simpler (and much faster) code while trying to model the bursts from a millisecond pulsar, SAX 1808.4—3658. Continuing failure of this effort led to suspicion about the formula for the nuclear energy yield, and some careful experiments with Kepler revealed that the widely-used approximation for the energy generation adopted for the simpler code substantially overestimated the contribution lost as neutrinos. Adelle's paper on the study has now been published by ApJ. Adelle's work was also highlighted in the 2018 December edition of the JINA-CEE Newsletter.

Read the paper (ApJ 870, 64, 2019)

Labels: 2018, /postgrads

The Large Synoptic Survey Telescope (LSST) is a truly impressive instrument for the next decade. The 8.4m telescope will illuminate a 3200 Mpix camera, and carry out a 10-year survey of the sky expected to provide millions of transient alerts... every night. Many astronomers in Australia are keen to get their hands on the data which is expected to start flowing around 2023. The Australian Science Lead, Sarah Brough (UNSW) along with Astronomy Australia Ltd. is coordinating a joint national membership which would allow access to the data for Australian astronomers, and this week my application to be one of the Principal Investigators was approved! Next step is to join one (or more) of the science groups and think about all the fun we can have when the telescope comes on-line. I'm also hoping to attend theaupcoming LSST@Asia meeting in Sydney, 20—23 May 2019.

Labels: 2018, /transients

Another possible site for the southern counterpart of our GOTO instrument on La Palma is USQ's Mt. Kent observatory. About 30 min drive from Toowoomba, Mt. Kent is significantly easier to get to compared to Siding Spring, via the recently-upgraded Wellcamp airport, and offers comparable observing conditions. Even better, they already have some spare concrete pads that might suit a GOTO-sized instrument! Earlier in the year we submitted a funding proposal to support development of the telescope from 2019 onwards. Fingers crossed!

Labels: 2018, /gravitational waves

The 15^th Nuclei in the Cosmos meeting was held at the Gran Sasso National Laboratory, near Assergi, Italy. Monash had a pretty good showing with PhD students Adelle Goodwin, Zac Johnston and Melanie Hampel all in attendance. I presented a talk bringing together some of our recent work on measuring neutron star properties from thermonuclear bursts. A highlight was the conference banquet, at the wonderful Magione Papale, al fresco dining on a beautiful summer's evening topped off with a remarkable fireworks show.

The meeting setting offered a terrific opportunity to explore the area; from the earthquake-damaged (and still not fully recovered) town of L'Aquila, to the mountains and valleys surrounding the nearby village of Assergi, an unlikely place to find an Australian hotel owner!

Measuring neutron star properties from thermonuclear bursts (8 MB PDF)

Labels: 2018, /meetings

This month I hosted the Burst Environments, Reactions and Numerical modelling workshop at Monash's Prato Centre, near Florence. Inspired by a series of ISSI international teams over the last few years, the meeting featured a selected group of attendees with the goal of bringing together researchers working on observational, numerical and nuclear experimental investigations of thermonuclear (type I) bursts. The centre proved an excellent venue for the great presentations and discussions we had over the week. I'm very grateful to JINA-CEE and MoCA for sponsoring the event, as well as the organising committee as well as Adelle and Zac for the website and their help organising. Hopefully these meetings will continue further, perhaps in Leiden in 2019!

Workshop website

Labels: 2018, /meetings