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Date + Time ................................
11/7/2015 - 20:20 UTC
Location ....................................
"Nunki Observatory" - Skiathos
Optics .........................................
Officina Stellare Advanced RILA 400 f/5.25
Tools .......................................... THE SKY
X
Camera ......................................
SBIG
STXL11002 with FW8G-STXL (Astrodon
filters)
Exposure Time.........................
Lum: 3.5 Hours
Mount ....................................... Paramount
ME
Guiding .................................... Self guided
Processing Details .................. Maxim , AIP4WIN
More Details ...........................
Environment Temperature : 21 oC Camera Temperature -30 οC
Sky temperature ..................... -6. οC
Notes ........................................ Weather:
Clear Transparence:
Medium
Humidity : 80-85 %
Moon Illumination ............... 18%
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.
KW
= primary is a yellow main-sequence star, secondary is a hotter
subdwarf. |
