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Abstract: In this work, we investigate the accuracy of various approximate expressionsfor the transit duration of a detached binary against the exact solution, foundthrough solving a quartic equation. Additionally, a new concise approximationis derived, which offers more accurate results than those currently in theliterature. Numerical simulations are performed to test the accuracy of thevarious expressions. We find that our proposed expression show yields a >200%improvement in accuracy relative to the most previously employed expression. Wederive a new set of equations for retrieving the lightcurve parameters andconsider the effect of falsely using circular expressions for eccentric orbits,with particularly important consequences for transit surveys. The newexpression also allows us to propose a new lightcurve fitting parameter set,which minimizes the mutual correlations and thus improves computationalefficiency. The equation is also readily differentiated to provide analyticexpressions for the transit duration variation TDV due to secular variationsin the system parameters, for example due to apsidal precession induced byperturbing planets.



Author: David M. Kipping

Source: https://arxiv.org/







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