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 925 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 V498 Peg is a slow(er) eclipsing binary variable star with a period of 15.827 hours
and which involves a delta mag of 0.7 (V) magnitudes during this brief time interval. The variable nature of V498 Peg was first reported by
Grzegorz Pojmanski in a
2002 publication outlining some of the all-sky survey results
involving the southern hemisphere. V498 Peg is a â Lyrae-type eclipsing system with ellipsoidal components where one observes a continuously
changing overall apparent system brightness, thus making the onset and termination of the eclipses difficult to predict and, hence, for its
classification, namely "EB".
Further details from the International Variable Star Index are available
here whereas an AAVSO finder chart is available
here.
Variable Star: V498 Peg Other Designation: GSC 01147-00395 RA / Dec: 22h 04m 51s / +14° 46' 19" Magnitude: 12.6 - 13.3 (V) Period: 0.659481 days Variability: EB Comparison Star: GSC 1147:0255 Check Star: GSC 1147:0217 |
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Date: Aug 13-14, 2013 21:45 - 03:20 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 |