ROOFTOP TELESCOPE PROVIDES BEST INFORMATION YET ON BINARY STAR

FAYETTEVILLE, Ark. - A rooftop telescope has taken a record number of observations of a binary star, allowing researchers to more closely compare observational statistics with theories of stellar evolution to test their validity.

Physics professor Claud Lacy and researchers Guillermo Torres from the Harvard-Smithsonian Center for Astrophysics and Antonio Claret at the Instituto de Astrofsica de Andaluca, Spain, will report their findings in the February issue of the Astronomical Journal.

Lacy, with help from graduate student Jeff Sabby and undergraduate students Ben Hood and Amber Straughn, made 5,759 observations of the binary star system WW Camelopardalus (WW Cam) in about five months.

"No other binary has been observed this completely," Lacy said.

The images show the relative brightness of the stars in relation to one another and to the background, and the telescope takes images approximately every 80 seconds. In eclipsing binary systems, the brightness dims when one star eclipses the other. From the light curve generated by these observations, the researchers can calculate the sizes of the two stars relative to the distance between them, the tilt of the orbital plane and the relative surface brightness of the two stars.

While this data generates a lot of information about the stars, the brightness observations combined with spectral data provide a more complete portrait of the star system, Lacy said.

"You have to gather information from different sources to get all the pieces of the puzzle," he said.

With the Harvard-Smithsonian Center for Astrophysics, Lacy and Sabby made a total of 85 spectral observations of WW Cam. From this they could determine the velocities of the stars. That plus the photometric observations allow the researchers to calculate the masses of the stars and the distance between them in kilometers.

Astronomers know of about 6,000 eclipsing binary star systems, of which the properties of about 100 have been determined. Lacy helped calculate the data on about 24 of the 100 eclipsing binary star systems.

Scientists believe that the stars in these systems were born at the same time - therefore they can test theories about stellar evolution by looking at stars known to be the same age and comparing their properties.

Hood, who recently won a Marshall Scholarship, purchased the telescope with funds from his Bodenhamer Fellowship. Lacy brought together department funds and a National Science Foundation grant to purchase a CCD camera for the observations.

The ten-inch remotely operated telescope, a Meade LX200, has produced 7,500 images in the last year, generating 30 gigabytes of data.

Lacy created a computer program that calculates the brightness of the star in question by comparing it to the background brightness in the image and to two other selected stars. The program can calculate the brightness of about two images per second, which helps when the camera has taken about 600 images in one night.

"We can measure a whole nights worth of data in a matter of minutes," he said.

The rooftop telescope has succeeded well with only one drawback - it resides in the middle of Fayetteville, a community of about 60,000 people. This limits the types of stars that can be observed because light pollution obscures many of the fainter ones.

"It’s like having a full moon every night," Lacy said.