Scholar Profiles
Linda Watson
Mentor: Ata Sarajedini
College of Liberal Arts and Sciences
" I applied to the USP so I could get a more in-depth understanding of what it is to be an astronomer. I want to see how the science I have learned thus far can be applied to current astronomy, while engaging in the further development of the science. I also hope to get a more structured idea of what branch of astronomy I would be most interested in pursuing."
Linda is a senior majoring in astronomy and physics. She is a member of Alpha Lambda Delta and Phi Eta Sigma and is a recipient of a Wentworth Scholarship and Bright Futures Scholarship. She enjoys reading fantasy and science fiction in her free time.
Research Description:
Photometry of M67
The goal of my project is to determine properties of M67, an
open cluster of stars. The bulk of the work involves photometry,
or measuring the brightness of stars. The images I am reducing
were collected at Kitt Peak National Observatory in February
2000, using the 0.9m telescope. To begin, the point-spread function
(psf) that describes the shape of the stars in an image within
a certain radius must be attained. Were there no atmosphere,
a star should appear as a single point of light on an image.
However, as the atmosphere interferes with the photon's travel
into the telescope, the point acquires shape. Because the stars
in one image are subjected to the atmosphere at the same time,
the psf should be the same for all stars on an image. Using
software developed by Peter B. Stetson, I found the psf in addition
to locating all the stars on the image, thus acquiring the magnitude
(a measure of brightness) of each star.
The next step is aperture correction of stellar magnitude. One
finds the magnitude of flux in an annulus between the psf radius
and a radius that is assumed to contain all the flux from the
star. After finding and applying the variation in this value
to each star, the aperture correction is subtracted from the
psf magnitude (magnitude is inversely proportional to brightness,
so the increased flux added in the annulus decreases the magnitude),
thus achieving the instrumental magnitude of the star.
I will then compare my instrumental magnitudes to standard magnitudes.
I must determine if or how the difference between the magnitudes
varies with the color of the stars.
After completing the reduction process on fifty-five images,
I will produce a color-magnitude diagram, which I can analyze
to determine the age and other properties of M67.
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