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 (150 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 variable star GP And is a delta-Scuti pulsating variable with a period of just
under two hours and involving a change of 0.6 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: GP And Other Designation: HIP 4322 RA / Dec: 00h 55m 18s / +23° 09' 49" Magnitude: 10.4 - 11.0 Period: 0.07868270 days Variability: DSCT Spectrum: A3 Comparison Star: GSC 1739:1584 Check Star: GSC 1739:1964 Lunar Phase: N/A |
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Date: Nov 08-09, 2007 22:37 - 02:00 UT+2 Location: Athens, Greece Equipment: AP 160 f/7.5 Starfire EDF AP 1200GTO GEM SBIG ST-2000XM SBIG CFW10 SBIG LRGB filters Integrations:
Temperatures:
Software: CCDSoft V5.00.182 AIP4Win V2.1.10 Processing: Reduction Differential Photometry |