Featured Research

from universities, journals, and other organizations

Unique eclipsing binary star system discovered

Date:
June 2, 2010
Source:
University of California - Santa Barbara
Summary:
Astrophysicists have identified two white dwarf stars in an eclipsing binary system, allowing for the first direct radius measurement of a rare white dwarf composed of pure helium.

In this artist conception of the unique binary star NLTT 11748, the larger but less massive helium white dwarf star is partially eclipsed by the smaller but more massive normal white dwarf, which is about the size of the earth.
Credit: Steve Howell/Pete Marenfeld/NOAO

Astrophysicists at UC Santa Barbara are the first scientists to identify two white dwarf stars in an eclipsing binary system, allowing for the first direct radius measurement of a rare white dwarf composed of pure helium. The results will be published in the Astrophysical Journal Letters. These observations are the first to confirm a theory about a certain type of white dwarf star.

Related Articles


The story began with observations by Justin Steinfadt, a UCSB physics graduate student who has been monitoring white dwarf stars as part of his Ph.D. thesis with Lars Bildsten, a professor and permanent member of UCSB's Kavli Institute for Theoretical Physics, and Steve Howell, an astronomer at the National Optical Astronomy Observatory (NOAO) in Tucson, Ariz.

Brief eclipses were discovered during observations of the star NLTT 11748 with the Faulkes Telescope North of the Las Cumbres Observatory Global Telescope (LCOGT), a UCSB-affiliated institution. NLTT 11748 is one of the few very low-mass, helium-core white dwarfs that are under careful study for their brightness variations. Rapid snapshots of the star -- about one exposure every minute -- found a few consecutive images where the star was slightly fainter. Steinfadt quickly realized the importance of this unexpected discovery. "We've been looking at a lot of stars, but I still think we got lucky!" he said.

Avi Shporer, a postdoctoral fellow at UCSB and LCOGT, assisted with the observations and quickly brought his expertise to the new discovery. "We knew something was unusual, especially as we confirmed these dips the next night," Shporer said. The scientists observed three-minute eclipses of the binary stars twice during the 5.6-hour orbit.

The excitement of the discovery and the need to confirm it rapidly led to the use of the 10-meter Keck Telescope, located on Mauna Kea in Hawaii, just five weeks after the first observation. The team also brought in David Kaplan, a Hubble Fellow and KITP postdoctoral fellow. Bildsten and Kaplan arranged for use of the Keck by swapping time they had reserved for another project with Geoff Marcy at UC Berkeley.

During that night, the scientists were able to measure the changing Doppler shift of the star NLTT 11748 as it orbited its faint, but more massive, white dwarf companion. "It was amazing to witness the velocity of this star change in just a few minutes," said Kaplan, who was present at the Keck telescope during the observations.

These observations led to the confirmation of an important theory about white dwarf stars. Stars end their lives in many ways. "The formation of such a binary system containing an extremely low mass helium white dwarf has to be the result of interactions and mass loss between the two original stars," said Howell. White dwarf stars are the very dense remnants of stars like the sun, with dimensions comparable to the earth. A star becomes a white dwarf when it has exhausted its nuclear fuel and all that remains is the dense inner core, typically made of carbon and oxygen.

One of the stars in the newly discovered binary is a relatively rare helium-core white dwarf with a mass only 10 to 20 percent of that of the sun. The existence of these special stars has been known for more than 20 years. Theoretical work predicted that these stars burn hotter and are larger than ordinary white dwarfs. Until now, their size had never been measured. The observations of the star NLTT 11748 by this research group have yielded the first direct radius measurement of an unusual white dwarf that confirms this theory.

The other star in the binary is also a white dwarf, albeit a more ordinary one, composed of mostly carbon and oxygen with about 70 percent of the mass of the sun. This star is more massive and also much smaller than the other white dwarf. The light it gives off is 30 times fainter than that of its partner star in the binary.

Bildsten credits the scientific collaborations at UCSB for the success of this work, noting that the original team was expanded to include KITP, the Physics Department, and LCOGT to quickly respond to the new discovery.

"A particularly intriguing possibility to ponder is what will happen in 6 to 10 billion years," said Bildsten. "This binary is emitting gravitational waves at a rate that will force the two white dwarfs to make contact. What happens then is anybody's guess."

The National Science Foundation, LCOGT, and NASA supported this work.


Story Source:

The above story is based on materials provided by University of California - Santa Barbara. Note: Materials may be edited for content and length.


Journal Reference:

  1. Justin D. R. Steinfadt, David L. Kaplan, Avi Shporer, Lars Bildsten, Steve B. Howell. Discovery of the Eclipsing Detached Double White Dwarf Binary NLTT 11748. The Astrophysical Journal, 2010; 716 (2): L146 DOI: 10.1088/2041-8205/716/2/L146

Cite This Page:

University of California - Santa Barbara. "Unique eclipsing binary star system discovered." ScienceDaily. ScienceDaily, 2 June 2010. <www.sciencedaily.com/releases/2010/05/100519092704.htm>.
University of California - Santa Barbara. (2010, June 2). Unique eclipsing binary star system discovered. ScienceDaily. Retrieved December 20, 2014 from www.sciencedaily.com/releases/2010/05/100519092704.htm
University of California - Santa Barbara. "Unique eclipsing binary star system discovered." ScienceDaily. www.sciencedaily.com/releases/2010/05/100519092704.htm (accessed December 20, 2014).

Share This


More From ScienceDaily



More Space & Time News

Saturday, December 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Spokesman: 'NORAD Ready to Track Santa'

Spokesman: 'NORAD Ready to Track Santa'

AP (Dec. 19, 2014) Pentagon spokesman Rear Adm. John Kirby said that NORAD is ready to track Santa Claus as he delivers gifts next week. Speaking tongue-in-cheek, he said if Santa drops anything off his sleigh, "we've got destroyers out there to pick them up." (Dec. 19) Video provided by AP
Powered by NewsLook.com
NASA's Planet-Finding Kepler Mission Isn't Over After All

NASA's Planet-Finding Kepler Mission Isn't Over After All

Newsy (Dec. 18, 2014) More than a year after NASA declared the Kepler spacecraft broken beyond repair, scientists have figured out how to continue getting useful data. Video provided by Newsy
Powered by NewsLook.com
Rover Finds More Clues About Possible Life On Mars

Rover Finds More Clues About Possible Life On Mars

Newsy (Dec. 17, 2014) NASA's Curiosity rover detected methane on Mars and organic compounds on the surface, but it doesn't quite prove there was life ... yet. Video provided by Newsy
Powered by NewsLook.com
Evidence of Life on Mars? NASA Rover Finds Methane, Organic Chemicals

Evidence of Life on Mars? NASA Rover Finds Methane, Organic Chemicals

Reuters - US Online Video (Dec. 16, 2014) NASA's Mars Curiosity rover finds methane in the Martian atmosphere and organic chemicals in the planet's soil, the latest hint that Mars was once suitable for microbial life. Linda So reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins