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Wed Oct 18, 2017

Detection of an optical counterpart to a binary neutron star merger

The milestones just keep coming this year for the burgeoning field of gravitational wave astronomy. Closely following the first "triple coincidence" detection of a black hole merger (with the two LIGO instruments joined by the Italian Virgo instrument), comes the announcement yesterday of the first detection of a binary neutron-star merger, which was — spectacularly — accompanied by a gamma-ray transient detected by Fermi GBM. Things just got more exciting when an optical counterpart was detected for the gamma-ray and gravitational-wave source, with the Swope Telescope in Chile. The counterpart, named SSS17a, was subsequently followed by an estimated 70 different observational groups (including a range of Australian facilities coordinated via the OzGRav Centre of Excellence). A literal frenzy of activity followed, culminating in the LIGO press release in the early hours (Australian time) yesterday, and followed by our own press event at Old Parliament House yesterday morning. It is hard to quantify the impact of this event; the announcement was accompanied by an estimated 76 papers (with likely more to come). Sadly, our own GOTO telescope missed out on this event, but the optical brightness indicates that future events will be easily detectable, and validates our instrumental design. The prospects for additional detections when O3 begins (in late 2018) are excellent.

Labels: 2017, /gravitational waves

Thu Sep 08, 2016

ARC Centre of Excellence for Gravitational Wave Discovery approved

The Australian Research Council announced this morning the outcomes of the Centres of Excellence scheme, and I'm delighted to report that our Centre for Gravitational Wave Discovery, aka OzGRav, was approved! The Centre, led by Swinburne's Prof. Matthew Bailes, will support research into detecting gravitational waves with interferometric detectors like Advanced LIGO as well as the Parkes Pulsar Timing Array. Nineteen Chief Investigators from six Australian universities will join with 15 partners from Australia and all over the world, in a program extending for the next 7 years. A great time to be a gravitational wave astronomer!

Labels: 2016, /gravitational waves

Tue May 03, 2016

Tuning up for Gravitational Wave Discoveries part II

Shakya Premachandra's paper on the orbital ephemeris of Cyg X-2, the next-best candidate LMXB (after Sco X-1) for continuous gravitational waves, has now been accepted by ApJ. Systems like Cyg X-2 and Sco X-1 may produce detectable gravitational radiation from "mountains" on the rapidly rotating neutron star, and precise knowledge of the system parameters (including the orbital period and neutron star spin frequency) may be critical for optimal GW searches with LIGO. However, many of the candidates are rather poorly known, so Shakya's analysis assembled the available data on the source to improve this situation. The accepted paper is available now at arXiv:1604.03233.

Labels: 2016, /gravitational waves

Fri Feb 12, 2016

First detection of gravitational waves

This morning, the LIGO Scientific Consortium has announced that it has made the first detection of gravitational waves. The signal was detected within 7 ms by both LIGO detectors in the US on September 14, 2015, and has been shown to be consistent with the merger of a pair of 30 solar mass black holes. The discovery was made possible by the enhanced capabilities of Advanced LIGO, a major upgrade that increases the sensitivity of the instruments compared to the first generation LIGO detectors. Amazingly, the detection was made prior to the first official observing run, instead being seen in an "engineering run" in which the instruments were otherwise operating optimally. This incredible achievement has kicked off an entirely new way of gathering information about the universe around us, and makes electromagnetic followup projects like our own Gravitational-wave Optical Transient Observer (GOTO) possible

Labels: 2016, /gravitational waves

Mon Nov 16, 2015

Hunting Gravitational Waves with Multi-Messenger Counterparts: Australia's Role

The first observations by a worldwide network of advanced interferometric gravitational wave detectors offer a unique opportunity for the astronomical community. At design sensitivity, these facilities will be able to detect coalescing binary neutron stars to distances approaching 400 Mpc, and neutron star-black hole systems to 1 Gpc. Eric Howell's paper, recently accepted by the Publications of the Astronomical Society of Australia, describes how Australian astronomical facilities and collaborations with the gravitational wave community can contribute to this new era of discovery, via contemporaneous follow-up observations from the radio to the optical and high energy. The preprint is now available at arXiv:1511.02959

Labels: 2015, /gravitational waves

Thu May 14, 2015

Searches for gravitational waves from Sco X-1

Sco X-1 is the brightest X-ray source (excluding the sun) in the sky, and is potentially also the brightest source of continuous gravitational waves. Chris Messenger led a multi-year project aimed at determining the relative benefits of a number of search algorithms that will likely be applied to aLIGO data. The mock-data challenge provided simulated data including signals at a range of strains, and each algorithm then attempted to find the signals. Encouragingly, the faintest detected signal is only a factor of two stronger than the estimated torque balance limit, which indicates that this limit may be beaten with improved algorithms, data, and also perhaps system parameter precision.

Read the paper (arXiv:1504.05889)

Labels: 2015, /gravitational waves

Mon Jan 06, 2014

Improved precision on Sco X-1 orbital parameters

Sco X-1 field with Uhuru Our program Precision Ephemeridies for Gravitational wave Searches (PEGS) posted it's first result this month, with the publication of refined orbital parameters for the X-ray binary Sco X-1. This remarkable source was the first X-ray binary ever discovered, and it's 19 hr orbital period was already known to unusually high precision thanks to 89 years of photometric observations. Thanks to new spectroscopic measurements from 2011, analysed by Monash PhD student Shakya Premachandra,we made a significantly more precise measurement, and also projected the uncertainties (including the effects of additional observations) forward into the Advanced LIGO/Virgo observing epoch. The paper is out this month in the Astrophysical Journal.

Read the paper

Labels: 2014, /gravitational waves

Tue Jun 12, 2012

GWPAW 2012, Hannover, Germany

Last week I visited Hannover for the Gravitational Wave Physics and Astronomy workshop, hosted by AEI-Hannover. I first attended this series of meetings, previously GWDAW, back in 2011; the attendees are a very interesting confluence of astrophysicists and gravitational-wave experimentalists. I presented the recent work with Shakya Premachandra on the orbital period of Sco X-1. I was also called in at the last minute to give a talk on the status and capabilities of the Australian Square Kilometre Array Pathfinder and the Mileura Widefield Array, replacing David Kaplan, who had to leave. The prospects for radio followup of future detections of graviational waves with advanced interferometers are very exciting! We also had the chance to visit the GEO600 interferometric gravitational wave detector, just outside Hannover, which was great (although rainy).

Tuning up for Gravitational Wave Detection in Accreting Neutron Stars: a progress report (3.2MB PDF)
Searching for Radio Transients with ASKAP (and MWA) (18.7MB PDF)

Labels: 2012, /gravitational waves