Erratum: Optical Observations of GRO J1655-40 in Quiescence. I. A Precise Mass for the Black Hole Primary

In the paper ``Optical Observations of GRO J1655-40 in Quiescence. I. A Precise Mass for the Black Hole Primary'' by Jerome A. Orosz and Charles D. Bailyn (ApJ, 477, 876 [1997]), some typographical errors occurred in the main text and in the Appendix that describes the eclipsing light curve code.

The legend to Figure 1 should read ``open circles'' instead of ``open diamonds.''

In § A1, the definitions of the angles φ and θ are reversed: the angle φ is the colatitude, and the angle θ is the longitude.

Equation (A4) should read g(x, y, z)=[(∂Ψ/∂x)²+(∂Ψ/∂y)²+(∂Ψ/∂z)²]^1/2 . (A4)

The equation giving the element of surface area dS(x, y, z) (eq. [A9]), while correct, contains some unclear notation. The grid spacings in the coordinate φ are equally spaced in cos φ so that Δφ = | d(cos φ) | = sin φdφ. Thus dS(x, y, z) has the correct form, and the numerical integration over the surface converges.

Equation (A10) should read σ(x, y, z)=1/g(x, y, z) [l_x ∂Ψ(x, y, z)/∂x+l_y ∂Ψ(x, y, z)/∂y+l_z ∂Ψ(x, y, z)/∂z] . (A10)

Equation (A20) should read d(x, y, z)=(1+R²-2Rl_x)^1/2 . (A20)There are also two minor changes in the code that need to be made:

An approximation was used to compute the foreshortening factor Γ_X-ray(x, y, z) (eq. [A21]). The exact expression is Γ_X-ray(x, y, z)=-1/d(x, y, z)g(x, y, z) [(x-1)(∂Ψ/∂x)+y(∂Ψ/∂y)+z(∂Ψ/∂z)] . (A21)

Equation (A24) should read Φ(x, y, z)=arctan(z cos η/1-x) . (A24)

The angle η was incorrectly defined in the code as arctan(y/x). The correct definition should be η = arctan[y/(1 - x)].

The changes in equations (A21) and (A24) alter the model light curves only for cases in which the X-ray luminosity L_X is not zero. The most complete light curves were from 1966 March, and we adopted L_X = 0 based on the low X-ray flux observed by ASCA during that time. Therefore, the important geometrical parameters that were derived from the modeling of the 1996 light curves are unchanged. For the model fits to the 1995 March light curves (where L_X >> 0), the changes in equations (A21) and (A24) lead to the revised parameter estimates that are given in the table below (Table 6 from the paper). The main conclusion from the end of § 5 (in which the 1995 light curves were discussed) remains the same, i.e., the basic shapes of the 1995 March V and I light curves can be explained if X-ray heating is included in the model.

The authors thank Sam Phillips of Oxford University for bringing these errors to their attention and for subsequent discussions.