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News Tip


February 10, 2003

For more information on these science news and feature story tips, contact the public information officer listed at (703) 292-8070. Editor: Josh Chamot

Nearly-Naked Stars Boost the Pulse of Asteroseismology

pulsating star
Figure1: A 5x5 arcminute CCD image of the prototype gravity-mode pulsating subdwarf B star, PG1716+426, and nearby comparison stars. North is up and East is to the left. The subdwarf B star pulsator is the brightest star in the northeast quadrant. The image was taken through an R filter at the University of Arizona Mt. Bigelow 1.6 m telescope and is one of hundreds used to measure the light curve of the star.
Photo Credit: Courtesy of Elizabeth Green of Steward Observatory at the University of Arizona and NSF.
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What goes on inside the heart of a star? Astronomers have been developing theories about stars' inner workings for decades, but evidence to confirm the details of those theories has been sparse.

In research supported by NSF, University of Arizona astronomer Elizabeth Green and colleagues have found a new subset of "nearly-naked" stars that dim and brighten due to pulses in their cores. The stars, which may help unlock secrets of advanced stages of stellar evolution, are described in the January 20 Astrophysical Journal Letters.

Chemical and physical changes inside star cores cause the light they emit to pulsate, becoming brighter and dimmer in slowly changing patterns. Analysis of these pulsations would give scientists a better of idea of the processes going on inside stars and help them understand how they change from one type to another. Until now, though, astronomers have been frustrated by the faintness of the pulses.

One problem is that most star cores are wrapped in a thick envelope of hydrogen gas that obscures any pulses that might occur. In 1997, astronomers thought they had found a new approach to the problem when they discovered a new class of pulsating stars, called subdwarf B stars. These stars are very hot evolved stars that have lost that outer envelope and are essentially "naked" cores. However, previous observations of the hottest subdwarf B stars revealed that their pulsations are weak and generally occur only minutes apart, making them hard to measure with conventional telescopes.

Astronomer Elizabeth Green, working with undergraduates from the University of Arizona, has been observing 80 cooler subdwarf B stars and is now releasing eye-opening results. Using a telescope operated by the university's Steward Observatory, the group found that 20 of the cooler stars commonly pulsate at relatively long intervals of about one hour, and that each star also has several pulse patterns. Green's collaborators, researchers Gilles Fontaine of the University of Montreal, and Mike Reed of Southwest Missouri State, say the processes causing the pulses are not yet understood, but that they originate in much deeper layers of the star than pulses in the hotter subdwarf B observed before.

Because they are abundant and easier to observe, the newly discovered stars should expand opportunities for researchers around the world to carry out asteroseismology. Using the multiple pulses, researchers will study the hearts of stars much as seismologists on earth study earthquakes to determine the Earth's interior structure.

Most of what scientists know about stellar interiors is based on theory, but there are competing explanations of why stars like our sun evolve from one type to another. Now that models of star cores will have to explain not just one but several patterns of pulsation in a single star, Green says the new data will narrow the field of theories and help researchers better predict the eventual fate of stars like our own Sun. [Roberta Hotinski]

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Coplink: Bridging Barriers Between Law Enforcement Agencies

As the law enforcement community embraces information technology, police departments face two contradictory problems: having too much information and not having enough information. Too much information could mean losing a key fact buried like a needle in a database haystack. Not enough information could mean never finding a key fact that another division or agency might have tucked away in its databases.

By March 2003, Redmond, Washington, and Boston, Massachussetts, will join the list of sites where law enforcement agencies are starting to solve these problems with COPLINK, developed in part with NSF Digital Government program support. COPLINK systems are currently deployed in Tucson and Phoenix, Arizona; Huntsville, Texas; Polk County/Des Moines, Iowa; and Montgomery County, Maryland. In Montgomery County, according to Chen, COPLINK will help compare the accumulated data relating to the case of the suspected Washington, D.C.-area snipers.

The COPLINK system uses techniques from artificial intelligence and other fields to help sniff out the faint trails woven through vast databases, potentially across police divisions or among agencies, and provide investigators with leads for their cases. The system was created by the University of Arizona's Artificial Intelligence Lab in partnership with the Tucson and Phoenix police departments.

"COPLINK's claim to fame is information sharing," said Hsinchun Chen, director of the Artificial Intelligence Lab. "Once the policy decision has been made to share data, it's easy to incorporate additional data sources." These data sources might be managed by other agencies or shared by other COPLINK installations.

COPLINK has been spun off into a commercial venture, while Chen and the COPLINK team continue to conduct research to improve the detection algorithms, notification capability, and other components. Their recent work includes exploring how to automatically detect deceptive criminal identities.

Because of its obvious application to homeland security, the COPLINK project is also supported by NSF's Knowledge Discovery and Dissemination program, in which NSF projects receive supplemental funding from the U.S. intelligence community.

In June 2003, with support from the NSF and the National Institute of Justice, the COPLINK Center and the Tucson Police Department will host the first NSF/NIJ Symposium on Intelligence and Security Informatics. The participants will discuss the technological, organizational and policy issues in developing advanced information technologies for national security applications. [David Hart]

University of Arizona Artificial Intelligence Lab:
NSF Data Mining and Homeland Security Applications:

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Wireless Internet Project for Native American Reservations Wins a "Wemmie"

The Wireless Communication Association International (WCA) recognized the Dandin Group and its CEO Dewayne Hendricks with a "Wemmie" award January 14 for installing wireless Internet connections to tribal community colleges at Fort Peck, Montana, and Turtle Mountain and Fort Berthold, North Dakota.

The effort was part of NSF's $6 million Advanced Networking Project with Minority Serving Institutions (AN-MSI), which is administered by EDUCAUSE, a nonprofit association whose mission is to advance higher education by promoting the intelligent use of information technology. The Dandin Group partnered with Motorola and received support from the AN-MSI project.

The Wemmie recognized innovation in the first use of Motorola's Canopy wireless technology. For the Dandin Group, the small Canopy antennas were essential because they could withstand brutal winds and winters without causing stress on existing towers. "Using conventional wireless technologies, we would not have been able to do this," Hendricks said.

The tribal college project is testing technology that can be used to converge voice, data and video on a single network that reaches into typically under-served areas, according to Dave Staudt, EDUCAUSE's AN-MSI project director. The project also benefits its participants by providing the hardware, software and training to implement wireless solutions.

The AN-MSI project assists minority-serving institutions -- historically black colleges and universities, Hispanic-serving institutions, and tribal colleges and universities -- as they develop the campus infrastructure and national connections to become and remain full participants in the Internet-based Information Age. [David Hart]

For further information, see, and

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