UNIONE ASTROFILI ITALIANI - Variable Stars Section

Eclipsing Binary Program

Eclipsing binaries program involves bright variable stars, easily to observe using binoculars.

Our program completely agree to AAVSO Eclipsing Binary Committee and observations must be sent also to the AAVSO EB Committee Chairman, Marvin E. Baldwin.

Our goal is to compute the observed time of minimum light (O) respect to the computed time (C): the so called O-C values. Its variations with time give us the opportunity to follow the physical evolution of binary system and to compute new ephemeris; the following paper is a good example of our activity: 

	Sergio Foglia,
	VW Cephei Times of Minima from Visual Observations
	Journal of the American Association of Variable Stars Observers, vol. 30 no. 2, 2002, 123
	PDF File (98 kB)

Eclipsing binary variable stars enclosed in our program are the following: 

data from Rocznik Astronomiczny Obserwatorium Krakowskiego (SAC - Supplemento ad
Annuario Cracoviense) No 74 for 2003

Variable:	name of variable star
Type:		type of variability
Epoch:		epoch of ephemeris
Period:		period of ephemeris
Magn.:		magnitude at maximum
A1:		amplitude (magn.) of primary minimum
A2:		amplitude (magn.) of secondary minimum
D:		total duration time of primary eclipse in hours
d:		duration of stationary phase (flat bottom of light curve, i.e. total eclipse phase) in hours

Variable Type Epoch Period Magn. A1 A2 D d chart
V822 Aql EB 2442577.333 5.294950 6.87 0.57 0.20 gif
WW Aur EA 2441399.305 2.525019 5.75 0.75 0.64 6.0 0 gif
AR Aur EA 2449706.3615 4.1346653 6.05 B 0.67 0.55 6.9 0 gif
LY Aur EB 2439061.463 4.002496 6.66 0.69 0.60 gif
eps Aur EA 2435629 9892 3.50 B 1.04 790d 366d gif
zet Aur EA 2435470.025 972.176 5.06 B 0.62 40d 37d gif
ZZ Boo EA 2449023.6622 4.9917633 6.79 0.65 0.65 7.2 gif
RZ Cas EA 2448960.2122 1.1952572 6.18 1.54 0.08 4.8 0 gif
TV Cas EA 2441595.3582 1.8125944 7.22 1.04 0.19 8.2 0 gif
V779 Cas EA 6.7 0.4 gif
U Cep EA 2451492.323 2.4930937 6.80 2.30 0.09 9.6 2.3 gif
VV Cep EA 2435931 7430 6.65 p 0.81 490d 450d gif
VW Cep EW 2451814.5506 0.2783109 7.30 0.54 0.33 gif
GT Cep EA 2425628.250 4.908756 8.16 p 0.90 16.5 0 gif
U CrB EA 2442946.728 3.4522279 7.66 1.13 0.06 11.6 0 gif
Y Cyg EA 2452639.564 2.9961669 7.30 0.60 0.45 7.2 0 gif
V367 Cyg EB 2437390.7688 18.59777 7.38 B 0.60 0.40 gif
V1143 Cyg EA 2448409.4182 7.6407538 5.85 0.48 0.23 4.0 0.4 gif
AI Dra EA 2448475.3086 1.1988175 7.05 1.04 0.11 4.4 0 gif
OW Gem EA 2415779.0 1258.59 9.0 B 1.9 0.1 13d? gif
RX Her EA 2432380.7145 1.7785720 7.26 0.63 0.48 6.0 0.9 gif
NQ Her EA 2426894.433 0.870218 8.0 p 0.6 3.1 gif
68 Her EA 2448852.367 2.051021 4.6 p 0.68 0.26 gif
AR Lac EA 2449292.3444 1.9831676 6.11 0.66 0.32 8.4 1.9 gif
del Lib EA 2448788.426 2.327362 4.91 B 1.05 0.07 12.8 gif
bet Lyr EB 2452652.486 12.940489 3.34 0.86 0.47 gif
V505 Mon EB? 2444635.318 53.78055 7.2 p 0.5 gif
U Oph EA 2452066.758 1.6773398 5.88 0.70 0.60 7.0 0 gif
V451 Oph EA 2444834.365 2.19659616 7.86 p 0.60 0.45 6.4 0 gif
V1010 Oph EB 2450963.757 0.6614165 6.10 0.90 0.35 gif
V1016 Ori EA 2442752.022 65.43280 6.5 1.5 18.8 1.6 gif
V1375 Ori E: 6.8 1.4 gif
EE Peg EA 2440286.4349 2.62821423 6.9 0.67 0.20 6.4 0 gif
bet Per EA 2452207.684 2.867328 2.12 1.28 0.07 9.6 0 gif
U Sge EA 2417130.4090 3.3806184 6.58 2.60 0.13 11.4 1.6 gif
CD Tau EA 2448661.4414 3.4351384 7.27 B 0.63 0.63 6.5 0 gif
HU Tau EA 2442412.456 2.056302 5.92 0.78 0.2 7.7 1.0 gif
lam Tau EA 2447185.265 3.952952 3.5 p 0.50 0.09 14.2 0 gif
W UMa EW 2451276.3967 0.33363554 7.76 0.73 0.65 gif
TX UMa EA 2445463.797 3.063291 7.06 1.70 0.07 9.4 0 gif
W UMi EA 2442235.7289 1.70113830 8.7 1.08 0.15 9.8 0 gif
Z Vul EA 2449568.4287 2.4549317 7.38 B 1.82 0.28 10.6 0 gif
RS Vul EA 2432808.257 4.4776635 6.9 p 0.73 0.04 15.1 0 gif

How to observe, when observe, how to submit observations

UAI VSS Circulars

Classification from General Catalogue of Variable Stars, 1985
Close Binary Eclipsing Systems

   We adopt a triple system of classifying eclipsing binary systems: according
to the shape of the combined light curve, as well as to physical and
evolutionary characteristics of their components. The classification based on
light curves is simple, traditional, and suits the observers; the second and
third classification methods take into account positions of the binary-system
components in the (MV ,B-V) diagram and the degree of inner Roche lobe filling.
Estimates are made by applying the simple criteria proposed by Svechnikov and
Istomin (1979). The symbols for the types of eclipsing binary systems that we
use are given below.

a) Classification based on the shape of the light curve

E        Eclipsing binary systems. These are binary systems with orbital planes
         so close to the observer's line of sight (the inclination i of the
         orbital plane to the plane orthogonal to the line of sight is close to
         90 deg) that both components (or one of them) periodically eclipse
         each other. Consequently, the observer finds changes of the apparent
         combined brightness of the system with the period coincident with that
         of the components' orbital motion.

EA       Algol (Beta Persei)-type eclipsing systems. Binaries with spherical or
         slightly ellipsoidal components. It is possible to specify for their
         light curves the moments of the beginning and end of the eclipses.
         Between eclipses the light remains almost constant or varies
         insignificantly because of reflection effects, slight ellipsoidality
         of components, or physical variations. Secondary minima may be absent.
         An extremely wide range of periods is observed, from 0.2 to >= 10000
         days. Light amplitudes are also quite different and may reach several
         magnitudes.

EB       Beta Lyrae-type eclipsing systems. These are eclipsing systems having
         ellipsoidal components and light curves for which it is impossible to
         specify the exact times of onset and end of eclipses because of a con-
         tinuous change of a system's apparent combined brightness between
         eclipses; secondary minimum is observed in all cases, its depth usually
         being considerably smaller than that of the primary minimum; periods
         are mainly longer than 1 day. The components generally belong to early
         spectral types (B-A). Light amplitudes are usually < 2 mag in V.

EW       W Ursae Majoris-type eclipsing variables. These are eclipsers with
         periods shorter than 1 days, consisting of ellipsoidal components al-
         most in contact and having light curves for which it is impossible to
         specify the exact times of onset and end of eclipses. The depths of
         the primary and secondary minima are almost equal or differ insignifi-
         cantly. Light amplitudes are usually < 0.8 mag in V. The components
         generally belong to spectral types F-G and later.




b) Classification according to the components' physical characteristics

GS       Systems with one or both giant and supergiant components; one of the
         components may be a main sequence star.

PN       Systems having, among their components, nuclei of planetary nebulae
         (UU Sge).

RS       RS Canum Venaticorum-type systems. A significant property of these
         systems is the presence in their spectra of strong Ca II H and K emis-
         sion lines of variable intensity, indicating increased chromospheric
         activity of the solar type. These systems are also characterized by
         the presence of radio and X-ray emission. Some have light curves that
         exhibit quasi sine waves outside eclipses, with amplitudes and posi-
         tions changing slowly with time. The presence of this wave (often
         called a distortion wave) is explained by differential rotation of the
         star, its surface being covered with groups of spots; the period of
         the rotation of a spot group is usually close to the period of orbital
         motion (period of eclipses) but still differs from it, which is the
         reason for the slow change (migration) of the phases of the distortion
         wave minimum and maximum in the mean light curve. The variability of
         the wave's amplitude (which may be up to 0.2 mag in V) is explained by
         the existence of a long-period stellar activity cycle similar to the
         11-year solar activity cycle, during which the number and total area
         of spots on the star's surface vary.

WD       Systems with white-dwarf components.

WR       Systems having Wolf-Rayet stars among their components (V 444 Cyg).

c) Classification based on the degree of filling of inner Roche lobes

AR       Detached systems of the AR Lacertae type. Both components are
         subgiants not filling their inner equipotential surfaces.

D        Detached systems, with components not filling their inner Roche lobes.

DM       Detached main-sequence systems. Both components are main-sequence
         stars and do not fill their inner Roche lobes.

DS       Detached systems with a subgiant. The subgiant also does not fill its
         inner critical surface.

DW       Systems similar to W UMa systems in physical properties (KW, see
         below), but not in contact.

K        Contact systems, both components filling their inner critical
         surfaces.

KE       Contact systems of early (O-A) spectral type, both components being
         close in size to their inner critical surfaces.

KW       Contact systems of the W UMa type, with ellipsoidal components of F0-K
         spectral type. Primary components are main-sequence stars and
         secondaries lie below and to the left of the main sequence in the
         (MV,B-V) diagram.

SD       Semidetached systems in which the surface of the less massive com-
         ponent is close to its inner Roche lobe.

   The combination of the above three classification systems for eclipsers
results in the assignment of multiple classifications for object types. These
are separated by a solidus ("/") in the data field. Examples are: E/DM,
EA/DS/RS, EB/WR, EW/KW, etc.