V0873 Aql

 

   

IMAGE DETAILS

Object ............................................ V0873  Aql
Constellation ..............................  Aquila
V. Magnitude + Variability......... 12.89- 13.49 / EW/KW

RA / DEC ..................................... 18h:45m.00sec / +00 34m.04sec
Period ...........................................  0.35757534  days

Comparison star .........................  GSC 447:78
Check star .................................... G
SC  448:649

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.

Nikos Paschalis