An abbreviated study of W UMa

Introduction

For our CCD imaging project, we decided to study an eclipsing binary system in hopes of producing a light curve. We decided to study W UMa because it is a well known system which allowed us to compare our results with published data. W UMa also has a relatively short period, therefore it is possible to observe a significant portion of the period in one evening.  Theoreticly, we hoped to use the data gathered to determine the period, distance, change in visual magnitude, luminiosity, and temperature of the system.  Unfortunatly, our school's astronomy program is realitivly new so we do not yet have the resources to obtain spectral data. Nevertheless, we were able to obtain the light curve for the primary minima of the system, and therefore determine the period,Vmax,  and change in V.

Method

To obtain the light curve, we used Macalester College's telescope (16 inch cassegrain) and CCD camera (visual filter) to take images of the system. We obtained a total of 38 images of W UMa over two evenings. Our standard star was HD 82862. One separate image of the standard star was taken for every image of W UMa. Our check star was GSC 3810:1252 and was located within the same frame as W UMa in each image. CCDOPS was used to analyze the images in order to determine apparent visual magnitude.
 
 

CCD image (visual filter) of W UMa and check star
 
 
 

CCD image (visual filter) of standard star

Results
 

Graphs
 
 

 The graph above shows the combined data of both nights that we observed. The times for JD 2451307 were
adjusted to match the times on JD 2451300. The error bars represent twice the standard deviation of
the magnitude of the check star on each respective night.
 
 

 This graph shows that our check star did not vary significantly in magnitude. The error bars signify the
standard deviation of all the visual magnitudes of the check star on each respective night.

Above is our data in the form of a phase diagram. The primary minima occurs at the zero point of the phase. The errorbars represent twice the standard deviation of the check star.  We were unable to observe the secondary minima.

Sources

Simbad  http://simbad.harvard.edu

Variable Star Catalog  http://www-astro.physics.uiowa.edu/cgi-bin/sendecl-bin.pl
 

Other Helpful Resources

Kauffman and Friedman.  Universe 5 ed. W.H. Freeman and Company, New York.  1998.

Sterken, C. and Jaschek, C.  Light Curves of Variable Stars. Cambridge U. P., 1996.

Rucinski, S. M. and Duerbeck, H. W.  PASP, 109.  pp. 1340-1350.  Dec. 1997.