Artist's impression of the eclipsing, pulsating binary star J0247-25
Credit:
Keele University
A team of astronomers from the UK, Germany and Spain have observed the remnant of a stellar collision and discovered that its brightness varies in a way not seen before on this rare type of star. By analysing the patterns in these brightness variations, astronomers will learn what really happens when stars collide. This discovery will be published in the 27 June 2013 issue of the journal Nature.
Stars like our Sun expand and cool to become red giant stars when
the hydrogen that fuels the nuclear fusion in their cores starts to run
out. Many stars are born in binary systems so an expanding red giant
star will sometimes collide with an orbiting companion star. As much
as 90% of the red giant star’s mass can be stripped off in a stellar
collision, but the details of this process are not well understood. Only
a few stars that have recently emerged from a stellar collision are
known, so it has been difficult to study the connection between stellar
collisions and the various exotic stellar systems they produce. When an
eclipsing binary system containing one such star turned up as a
by-product of a search for extrasolar planets, Dr Pierre Maxted and his
colleagues decided to use the high-speed camera ULTRACAM to study the
eclipses of the star in detail. These new high-speed brightness
measurements show that the remnant of the stripped red giant is a new
type of pulsating star.
Many stars, including our own Sun, vary in brightness because of
pulsations caused by sound waves bouncing around inside the star. For
both the Sun and the new variable star, each pulsation cycle takes about
5 minutes. These pulsations can be used to study the properties of a
star below its visible surface. Computer models produced by the
discovery team show that the sound waves probe all the way to the centre
of the new pulsating star. Further observations of this star are now
planned to work out how long it will be before the star starts to cool
and fade to produce a stellar corpse (“white dwarf’”) of abnormally low
mass.
Dr Pierre Maxted from Keele University, who led the study, said “We
have been able to find out a lot about these stars, such as how much
they weigh, because they are in a binary system. This will really help
us to interpret the pulsation signal and so figure out how these stars
survived the collision and what will become of them over the next few
billion years.”
PR Contacts
Chris Stone,
Press and Publicity Officer,
Keele University
Tel: 01782 733375
E-mail: c.w.stone@keele.ac.uk
Contacts
Dr Pierre Maxted,
Keele University
Tel: 01782 733457
E-mail: p.maxted@keele.ac.uk
Links
Further information, including facts-and-figures about this new star,
a short sound clip and an animated visualisation are available on the
following web page: http://www.astro.keele.ac.uk/~pflm/J0247/ . ULTRACAM web site: http://www.vikdhillon.staff.shef.ac.uk/ultracam
Notes for editors
The team involved in the discovery are: Dr Pierre Maxted and Dr
Barry Smalley (Keele University, UK); Dr Aldo Serenelli (CSIC-IEEC,
Spain); Andrea Miglio (University of Birmingham, UK); Prof. Thomas Marsh
and Dr Elmé Breedt (University of Warwick, UK), Prof. Ulrich Heber and
Veronika Schaffenroth (Dr. Karl Remeis-Observatory & ECAP, Germany),
Prof. Vikram Dhillon and Dr Stuart Littlefair (University of Sheffield,
UK), Dr Chris Copperwheat (Liverpool John Moores University, UK).
ULTRACAM is a high-speed, 3-channel CCD camera for astrophysical
research ULTRACAM was funded by PPARC and is a collaboration between,
Professor Tom Marsh (University of Warwick) Professor Vik Dhillon
(Sheffield) and the Astronomy Technology Centre (Edinburgh).
The observations were made using the 3.6-m New Technology Telescope at the European Southern Observatory (ESO).
Source: Keele University
