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Date + Time ................................ 01/10/2012 - 17:40 UTC
Location ....................................
"Nunki Observatory" - Skiathos
Optics .........................................
Celestron C 11 HD
Tools .......................................... Maxim
Dl
Camera ......................................
SBIG ST 2000 XM
Exposure Time.......................
Clear: 3.8 Hours (bin1X1)
Mount ....................................... Paramount
ME
Guiding .................................... Unguided
Processing Details ................
Maxim , CCDsoft , AIP4WIN
More Details ...........................
Environment Temperature : 22 oC Camera Temperature - 5 οC
Sky Temprature....................... -10 οC
Notes ........................................ Weather:
5/10 Transparence: 3/6 Humidity : 75-80 %
Moon Illumination ............... 97%
Target details .........................
A W Ursae Majoris variable is a type of
eclipsing binary
variable star. These stars are close binaries of spectral types
F, G, or K that share a common envelope of material and are thus in
contact with one another. They are termed
contact binaries because the two stars touch and transfer mass
and energy through the connecting neck, although astronomer R.E.
Wilson argues that the term "overcontact" is more appropriate.
W Ursae Majoris variables are the most common variable stars in the
present day Universe. About 1 percent of all stars belong to this
group.The class is divided into two subclasses: A-type and W-type
(L. Binnendijk, Veroeffentlichungen der Remeis-Sternwarte zu
Bamberg, Nr. 40., p. 36, 1965) A-type W UMa binaries are composed of
two stars both hotter than the Sun, having
spectral types A or F, and
periods of 0.4 to 0.8 day. The W-types have cooler spectral
types of G or K and shorter periods of 0.22 to 0.4 day. The
difference between the surface temperatures of the components is
less than several hundred
kelvins.
A new subclass was introduced in 1978: B-type. The B-types have
larger surface temperature difference. In 2004 the H (high mass
ratio) systems were discovered by Sz. Csizmadia and P. Klagyivik (Astronomy
and Astrophysics, Vol. 426, pp. 1001-1005 (2004)).
Their light curves differ from those of classical
eclipsing binaries, undergoing a constant ellipsoidal variation
rather than discrete
eclipses. This is because the stars are in physical contact and
thus constantly eclipse one another, and also because the stars are
gravitationally distorted by one another. The depths of the
brightness
minima are usually equal because both stars have nearly equal
luminosities.
W Ursae Majoris is the
prototype of this class. *
EW = W UMa. Components almost touching, and primary &
secondary eclipses near-equal. Periods < 1 day.
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