Algol type eclipsing variable

When a colder star passes before a hotter star , part of the light of the hotter star is eclipsed, and the total brightness of the pair temporarily decreases. In this case, the primary minimum is noted on the brightness curve. The general brilliance also falls in the case when a hotter star passes before a colder one. But in this case, the brightness drops much less and a secondary minimum appears on the light curve , which is more than an order of magnitude less than the primary one.

The period, i.e., the time between two primary minima, is very constant, because it is determined exclusively by the time of revolution of one star around the other.

Variables of the Algol type are fairly close systems and, accordingly, the eclipse period is small, usually several days. The best known short period is 0.117 days (2 hours 48 minutes) for VW HW ^[1] , the longest - 9892 days (27 years) for Voznichsky ε . If partial eclipses occur in the system, then the minima on the light curve have a pointed shape, since the brightness in this case is constantly changing. And if there are total eclipses, then, depending on the relative sizes of the system components, the minimum of the light curve represents a more or less long segment ^[2] .

Stars in such systems have a spherical or slightly ellipsoidal shape, which distinguishes them from eclipsing variables of other types, for example, eclipsing variables like β Lyrae or eclipsing variables like W Ursa Major , in which gravitational effects are so strong that they lead to serious deformations of both stars. In view of this, the sections of the maximum on the light curve are rectilinear, and not smoothly rounded ^[2] .

The amplitudes of the brightness variations of the variables are usually of the order of one magnitude . The strongest known amplitude is 3.4 magnitudes ( V342 Eagles ). The binary system components may belong to different spectral classes , but in most cases the brighter star belongs to classes B, A, F, and G.

The prototype of this class of stars was the star Algol , β Perseus . Its variability was first described in the scientific literature in 1667 by Giminiano Montanari . And the mechanism of variability was first correctly explained by John Goodrayk in 1783 .

Currently, more than 3500 variables of the Algol type are known, which is 9% of the total number of variable stars.

• Eclipsing Binary Stars Stephen F. Austin State University (Eclipsing Binary Stars Stephen F. Austin State University)

• Bronshten V.A. Eclipsing variables // Quantum. - 1972. - No. 9 . - S. 22-29 .