Analysis of a Newly Identified Variable Star In Aquarius

Heath Gibson

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Abstract

This report is the result of an independent research project designed to plot the light curves of variable star candidates of an intermediary magnitude range little researched by astronomers. Research was done using two 24” telescopes located at Mt. Wilson and Table Mountain.  One variable star was found, and the data indicates it is an eclipsing binary, that is, two stars which rotate around each other.  My research advisors were Barrett S. Duff, Deputy Director and Project Scientist of Telescopes in Education (TIE); Dr. Robert Korechoff, Physicist, JPL; and Dr. Milan Mijic, Professor of Physics and Astronomy, California State University, Los Angeles.

1. Introduction

This report is the outcome of an experiment begun in August, 1999, to trace the magnitudes and plot the light curves of variable star candidates of an intermediary magnitude range, in order to determine if any were variable stars, and if so, what type(s).  A variable star is one which varies in brightness over a certain period of time.  The period of time in which it varies changes according to the type of variable star; therefore, the star’s period is used to determine its type. There are three different types of variable stars: an intrinsic variable whose change in magnitude occurs as a direct result of a single star’s unstable nature; a cataclysmic variable, whose variability is a consequence of a star either “going nova” or exploding into a supernova; and an eclipsing binary in which one star eclipses another in a binary star system.

Few astronomers have observed variable stars in the intermediary magnitude range, defined as 10.0 to 18.0.  This gap exists because amateur astronomers, with their smaller and less sophisticated equipment, usually focus on bright stars having magnitudes less than 10.0, whereas professional astronomers usually focus on dimmer stars having magnitudes above 18.0.  Because little research has been done on the stars in this intermediate range, no one knows if these variables have characteristics similar to those known variables outside of this magnitude range.  To help fill this information gap, I chose to research variable star candidates from this intermediate range.  My hypothesis was that I would find an intrinsic variable with a short period of a week or two.

To choose variable star candidates for research, I downloaded a file from the U.S. Naval Observatory (USNO) web site that contained approximately 1,600 suspected variables.  My foremost selection criterion was a magnitude range between 10.0 and 18.0.  Then, in order to maximize the number of hours I could work on this project each evening, I searched for stars that would be rising at about thirty-five degrees above the horizon in the east at 8:00 p.m., the approximate time of dusk.  Using this selection criteria, I found four variable star candidates near the celestial equator whose characteristics were unknown.  I examined the change in their brightness over the four months the stars were visible in order to determine whether or not a variable existed in the group.  Once I proved a variable existed, I narrowed my research to that star and then analyzed the data to determine what type of variable it was.

2. Previous Work on the Four Suspected Variable Stars

Before my research was conducted, the four suspected variables had been placed in the USNO-SA2.0 Catalog and had been assigned an average red and blue magnitude; this was the only information that had been collected on them up to then.  The following tables give the equatorial coordinates of each star (suspected variable and reference stars).  For ease of reference, I renamed each variable candidate N, O, P, and Q respectively; each variable candidate has its own two or three reference stars with names A, B, and C.

Table 1. Data for Suspected Variable N (USNO-SA2.0 Catalog #O18030273)

Table 2. Data for Suspected Variable O (USNO-SA2.0 Catalog #O280031312)

 

Table 3. Data for Suspected Variable P (USNO-SA2.0 Catalog #O33020146)

 

Table 4. Data for Suspected Variable Q (USNO-SA2.0 Catalog #O33040049)

3. Materials Used for Project

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