Crowdsourced x-ray binary observations pay off

The American Association of Variable Star Observers, which coordinates a global network of amateur astronomers who observe variability in stars on a variety of levels, is presently taking part in a scientific campaign. In coordination with the JACPOT collaboration, the AAVSO are making observations of x-ray binary stars.

X-ray binaries are pairs of objects – one very compact and high mass, of the order of white dwarfs, neutron stars and black holes, and the other big, gassy and able to feed that gas to the smaller one. As gas is ripped from what is normally a red or other type of giant star and collected by the compact companion, it forms an accretion disc as particles spiral down towards the companion’s surface. Charged particles spiraling always release energy and this can be in the form of x-rays if they are accelerated fast enough. In some cases, jets of particles also form and these too can emit energy, most normally as radio waves. The accretion of spinning matter by neutron stars in this way has been considered one of the ways of forming pulsars.

But it isn’t really known exactly how the formation of jets differs in the different types of binaries, especially the white dwarf ones whose companions are the least dense and compact of the three. To this end, a series of known binaries has been listed and the AAVSO have been asked to keep an eye on them. When it looks like one is setting off, then professional telescopes can be turned on them to confirm this and then begin to perform proper observations at different wavelengths.

In mid April, the AAVSO amateurs turned their eyes to the dwarf nova SS Cygni and on the 19th reported signs of an outburst. JACPOT then turned the Expanded Very Large Array telescope and the Very Long Baseline Array were turned to view it along with the Swift x-ray space telescope, Faulkes North, the FanCam IR Instrument, PAIRITEL and various other observers. The EVLA and the VLBA will continue their campaign to observe the development of the radio signal from the binary now the others have peeled off, having confirmed the event. The evolution of the signal will be crucial in determining its origin.

Further information, first results and any new results are all posted at this website at the AAVSO. This will not be their last such campaign, so I’d encourage all you skilled amateurs hoping to contribute and do some real science to join in. One place to start might be Citizen Sky, their online citizen science experiment.


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