A variable star, as its name suggests, is a star whose magnitude varies intrinsically, in contrast to eclipsing binaries whose magnitude
varies as a result of one star in the binary system eclipsing the other. True variables are one of five types, namely Mira stars,
semiregular stars, cepheids, eruptive variables and, finally, cataclysmic variables. Minimum to maximum magnitude can range from days to
many months with some variables displaying irregular periods.
A popular method for the study of variable stars, particularly short-term variables, is by the use of the technique known as "differential
photometry". Rather than measure the (variable) magnitude of a variable star on an absolute scale, measurements are made over time relative
to one or more non-variable star(s) and these differences are then plotted so as to study and illustrate the relative or differential
change in magnitude. Due to the very large number of variables stars, the field of differential photometry represents one of the key fields
in astronomy whereby the amateur astronomer can make a meaningful and long-lasting contribution to both science and astronomy.
More recently, the search for extrasolar planets (275 discovered so far) has identified yet another interesting application for the practice
of differential photometry whereby the minute drops in magnitude of a star hosting an exoplanet are studied. Further details for the
interested party are available here.
Note: The eclipsing binary star TZ Boo is a type W UMa variable with a period of just over six hours
and involving a change of 0.59 magnitudes during this time interval. Further details from the General Variable Star Search Gateway
are available
here whereas
an AAVSO finder chart is available
here.
Variable Star: TZ Boo Other Designation: BD +40 2857 RA / Dec: 15h 08m 09s / +39° 58' 13" Magnitude: 10.41 - 11.00 v Period: 0.2971620 days Variability: EW/KW Spectrum: G2V Check Star: GSC 3045:1118 Comparison Star: GSC 3045:959 Lunar Phase: N/A |
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Date: May 27-28, 2008 22:50 - 03:05 UT+3 Location: Athens, Greece Equipment: AP 160 f/7.5 Starfire EDF AP 1200GTO GEM SBIG ST-2000XM SBIG CFW10 SBIG LRGB + IR-block Integrations:
Temperatures:
Software: CCDSoft V5.00.188 AIP4Win V2.2 Processing: Reduction Differential Photometry |