School students help astronomers study mysterious X-ray source

April 20, 2011, Royal Astronomical Society
This is an artist's impression of a spinning neutron star (pulsar) approximately 20 kilometres in diameter, accreting material from a companion star. The strong gravity from the dense pulsar attracts material from the companion. The flow of gas from the companion to the pulsar is energetic and glows in X-ray light. Credits: NASA/Dana Berry

( -- Astronomers from Wales and the Netherlands, in collaboration with five schools, have used eight telescopes simultaneously to study the strange behaviour of an X-ray binary star system.  Results were presented by postgraduate student Fraser Lewis at the RAS National Astronomy Meeting in Llandudno, Wales, on Monday 18th April.

IGR J00291+5934 (‘00291’) is a rare X-ray binary system containing a pulsar – a neutron star spinning several hundred times per second – and a normal star. Only 12 such systems are known. In September 2008, 00291 increased in brightness at X-ray wavelengths by a factor of at least a thousand times and in visible wavelengths by a factor of around a hundred times. While this type of outburst is not uncommon for this type of system, the timescale is usually months to years. However 00291, having been in outburst for 20 days, faded away to its normal faint state but then re-brightened within 30 days.
"We had never seen this rapid a turnaround in a system of this type before" said Lewis, of the Faulkes Project at the University of Glamorgan. "To try to understand what was driving this unique behaviour, we gathered data from several telescopes, at different wavelengths, to create a dataset of unprecedented detail."
The group, led by Lewis and Dr. David Russell, of the University of Amsterdam, used data from Faulkes Telescope North, the Isaac Newton Telescope and the Keck Telescope (optical wavelengths), PAIRITEL (infrared), the Westerbork Synthesis Radio Telescope (radio), the Swift GRB mission (UV and X-ray), and the XMM-Newton and RXTE satellites (X-ray).  Five schools, including St. Brigid's School, Denbigh and St Davids College, Cardiff, were involved in collecting the data using Faulkes Telescope North.
In X-ray binary systems, material from the star spirals in towards the pulsar, forming an accretion disc. Friction and gravity heat this material up until it reaches temperature of millions of degrees and emits X-rays.
"The behaviour of 00291 is baffling. Outbursts are thought to be driven by the 'emptying' of the accretion disc, which means that the time between outbursts indicates the time that it takes to fill the disc, and the size of the disc itself. However, for a system as compact as 00291, it’s unlikely that it could replenish its supply within 30 days," said Lewis.
To find a solution to this mystery, Lewis and Russell have turned to a group at the Naval Research Laboratory in Washington led by Dr. Jacob Hartman.  Hartman's group suggests that the outburst is all one event that was interrupted halfway through by a propeller effect.
"The idea is that when the 'propeller' switches on, the material that was spiralling inwards becomes ejected from the system, stopping the outburst. Then the propeller switches off again, the outburst restores itself.  However, there are still many things that we don’t understand," said Lewis.
These results are presented within the wider context of an extensive optical monitoring program of 32 low-mass X-ray binaries using the 2-metre Faulkes Telescopes in Hawaii and Australia.

Explore further: RXTE Homes in on a Black Hole's Jets

Related Stories

RXTE Homes in on a Black Hole's Jets

July 1, 2010

( -- For decades, X-ray astronomers have studied the complex behavior of binary systems pairing a normal star with a black hole. In these systems, gas from the normal star streams toward the black hole and forms ...

Three satellites needed to bring out 'shy star'

July 13, 2005

An international team of scientists has uncovered a rare type of neutron star so elusive that it took three satellites to identify it. The findings, made with ESA’s Integral satellite and two NASA satellites, reveals new ...

Helium pair have regular violent flare ups

May 24, 2010

( -- A team of astronomers led by Dr Gavin Ramsay of Armagh Observatory have spotted violent eruptions from an interacting pair of stars that orbit around each other every 25 minutes. Unusually, these outbursts ...

Eclipsing pulsar promises clues to crushed matter

August 17, 2010

Astronomers using NASA's Rossi X-ray Timing Explorer (RXTE) have found the first fast X-ray pulsar to be eclipsed by its companion star. Further studies of this unique stellar system will shed light on some of the most compressed ...

Recommended for you

NASA powers on new instrument staring at the Sun

March 16, 2018

NASA has powered on its latest space payload to continue long-term measurements of the Sun's incoming energy. Total and Spectral solar Irradiance Sensor (TSIS-1), installed on the International Space Station, became fully ...

Dawn reveals recent changes in Ceres' surface

March 15, 2018

Observations of Ceres have detected recent variations in its surface, revealing that the only dwarf planet in the inner solar system is a dynamic body that continues to evolve and change.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.