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 750 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 GSC 02996-00677 is a quick eclipsing binary variable star with a period of 0.3609
days and which involves a delta mag of approximately 0.34 (C) magnitudes during this brief time interval. The variable nature of GSC 02996-00677
was first reported by Anthony Ayiomamitis in 2014 following
inspection of the field of view for the exoplanet host star KELT-3 in Leo Minor.
GSC 02996-00677 is an W Ursae Majoris-type eclipsing system where the binary components involve main sequence stars with ellipsoidal components
virtually in contact with each other and, hence, for its classification, namely "EW/KW".
The characteristics of the phase light curve based on 38.9 hours of total data suggests that a W-subtype system is involved using
Binnendijk's
criteria between A- and W-type subtypes.
Further details from the International Variable Star Index are available
here.
Variable Star: GSC 2996-0677 Other Designation: N/A RA / Dec: 09h 53m 12s / +40° 08' 19" Magnitude: 13.47 - 13.81 (C) Period: 0.3609 days Variability: EW Comparison Star: GSC 2996:0618 Check Star: GSC 2996:0799 |
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Date: Mar 09-10, 2013 21:50 - 03:50 UT+3 Location: Athens, Greece Equipment: AP 305/f3.8 Riccardi-Honders 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 |