Printer Friendly

A record-breaking star with flare.

The binary star V711 Tau, about 100 light-years from Earth, belongs to a class of binaries that have relatively high magnetic fields. Noting that the sun and other magnetically active stars produce flares with the sudden release of stored magnetic energy, researchers reasoned that sooner or later, V711 Tau might erupt. But after 15 years of study -- the last eight with a robotic telescope on Arizona's Mount Hopkins -- astronomers found no evidence that this star or any of the other 110 binaries in the same class that the observed had ever undergone such sudden brightening.

V711 Tau's status changed irrevocably on Dec. 14, 1989. Astronomers at the Beijing (China) Astronomical Observatory noted a rapid brightening of the star over just a few hours. After years of negative results, Gregory W. Henry of nennessee State University in Nashville figured the Chinese had erred. But checking with the Mount Hopkins telescope, he found that 12 hours after the Beijing observation, the star had undergone another, more intense jump in luminosity. That flare may represent not only the first observed in this stellar class, but also the most intense observed on any star, Henry says.

At the peak of the flare-up, which lasted about six hours, the total amount of energy released by the star climbed to 5 X [10.sup.34] ergs/second -- a rate about 10 times as large as the sun's total output and 100 million times as intense as a typical white-light solar flare, report Henry and Douglas S. Hall of Vanderbilt University in Nashville.

They also found that the star's overall luminosity remained slightly elevated for three months after the record-breaking outburst. This, coupled with the star's orientation relative to Earth, indicates that the flare may have temporarily erased a large, light-obscuring spot -- perhaps similar to a sunspot -- believed to reside at one of the star's poles, Henry says. The luminosity slowly returned to normal levels, perhaps as the spot began to build back up, he adds.

The flare's origin remains unclear. Because its intensity far exceeded that of a solar flare, it may well have arisen from processes that differ from those causing outbursts on the sun. Even so, V711 Tau's magnetic activity might possibly undergo fluctuations resembling the 11-year sunspot cycle, Henry says.
COPYRIGHT 1991 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:binary star V711 produces flare
Author:Cowen, Ron
Publication:Science News
Date:Jun 15, 1991
Previous Article:Virgo images suggest smaller universe.
Next Article:LDEF maps orbiting junk.

Related Articles
Cyg X-3: photinos, quark nuggets?
Fastest pulsar so far.
A dizzying orbit for a binary star.
Further findings on flare phenomena.
Fantastic fortnight of active region 5395.
The ups and downs of solar flares.
Low-budget stellar spectroscopy.
An outburst of stellar knowledge.
Fortnight of flares dazzles astronomers.
An X-ray burster's visible trail.

Terms of use | Copyright © 2016 Farlex, Inc. | Feedback | For webmasters