VARIATIONS IN THE BRIGHTNESS AND COLOR OF A STAR DURING ECLIPSING BY A PROTOPLANET

摘要

Changes in the brightness and color of stars obscured by gas-dust protoplanets are studied using Equation (1). In a quite general case, assuming only y that τ(x, y)∈[0, τ~(max) ], it is shown that the ratio (Δm_2~(min)? Δm_1~(min) )/Δm_1~(min) decreases with increasing Δm_1~(min) at the brightness minima. The region where points from the set {E_1; E_2} can lie on an E_2 vs E_1 diagram is localized within a rather narrow parallelogram with a long diagonal given by Eq. (10). If τ(x, y) = τ~(max) (1? (x~2 + y~2 ) / R~2)/(1/2), then the unknown E_2 as a function of E_1 is essentially given by Eq. (10). Calculated "brightness-color" curves are fundamentally different from the interstellar absorption law. If it is held that the color indices increase linearly in Ae/Be Herbig stars with falling brightness, i.e., (Δm_2? Δm_1)/Δm_1=const, and that this ratio is independent of the depth of eclipsing, then it appears that the Algol-like variation in the brightness of Ae/Be Herbig stars cannot be explained in terms of a model of occultation by a protoplanet.