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 (over 500 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 large-amplitude short-period pulsating star GSC 04923-00693 is a fast pulsating variable star with a period
of 95.83 minutes and which involves a delta mag of 0.76 (V) magnitudes during this brief time interval. GSC 04923-00693 was discovered by
Pojmanski et al in 2002 during a wideangle survey
of the southern hemisphere.
Further details from the International Variable Star Index are available
here
whereas an AAVSO finder chart is available
here.
Note: Ten measurements were omitted due to thick clouds and which made photometry impossible.
Variable Star: GSC 4923-0693 Other Designation: ASAS 112518-0047.3 RA / Dec: 11h 25m 18s / -00° 47' 18" Magnitude: 13.34 - 14.10 Period: 0.066549 days Variability: DSCT Comparison Star: GSC 4923:716 Check Star: GSC 4923:792 |
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Date: Apr 03-04, 2011 21:30 - 01:31 UT+3 Location: Athens, Greece Equipment: AP 160 f/7.5 Starfire EDF AP 1200GTO GEM SBIG ST-10XME SBIG CFW10 SBIG LRGB filters Integrations:
Temperatures:
Software: CCDSoft V5.00.201 AIP4Win V2.4.0 Processing: Reduction Differential Photometry |