Astronomy and Astrophysics – Astronomy
Scientific paper
Jun 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997apj...482.1086o&link_type=abstract
Astrophysical Journal v.482, p.1086
Astronomy and Astrophysics
Astronomy
15
Errata, Addenda
Scientific paper
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 phi and theta are reversed: the angle phi is the colatitude, and the angle theta is the longitude. Equation (A4) should read g(x, y, z)=[(\frac {∂ Psi }{∂x} )2+(\frac {∂ Psi }{∂y} )2+( \frac {∂ Psi }{∂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 phi are equally spaced in cos phi so that Delta phi = | d(cos phi ) | = sin phi d phi . Thus dS(x, y, z) has the correct form, and the numerical integration over the surface converges. Equation (A10) should read sigma (x, y, z)=\frac {1}{g(x, y, z)} [lx \frac {∂ Psi (x, y, z)}{∂x} +ly \frac {∂ Psi (x, y, z)}{∂y} +lz \frac {∂ Psi (x, y, z)}{∂z} ] . (A10) Equation (A20) should read d(x, y, z)=(1+R2-2Rlx)^{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 Gamma X-ray(x, y, z) (eq. [A21]). The exact expression is Gamma _{{\rm X-ray}}(x, y, z)=\frac {-1}{d(x, y, z)g(x, y, z)} [(x-1)(\frac {∂ Psi }{∂x} )+y(\frac {∂ Psi }{∂y} )+z(\f rac {∂ Psi }{∂z} )] . (A21) Equation (A24) should read Phi (x, y, z)={\rm arctan}(\frac {z {\rm cos} eta }{1-x} ) . (A24) The angle eta was incorrectly defined in the code as arctan(y/x). The correct definition should be eta = 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 LX is not zero. The most complete light curves were from 1966 March, and we adopted LX = 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 LX >> 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.
Bailyn Charles D.
Orosz Jerome A.
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