  In previous hydrodynamical simulations, we found a mechanism for nearly
circular binary stars, like Kepler-413, to trap two planets in a stable 1:1
resonance. Therefore, the stability of coorbital configurations becomes a
relevant question for planet formation around binary stars. Here, we
investigate the coorbital planet stability using a Kepler-413 analogue as
example and then expanding the parameters to study general n-body stability of
planet pairs in eccentric horseshoe orbits around binaries. The stability is
tested by evolving the planet orbits for $10^5$ binary periods with varying
initial semi-major axes and planet eccentricities. The unstable region of a
single circumbinary planet is used as a comparison to the investigated
coorbital configurations in this work. We confirm previous findings on the
stability of single planets and find a first order linear relation between
orbit eccentricity and pericentre to identify stable orbits for various binary
configurations. Such a linear relation is also found for the stability of 1:1
resonant planets around binaries. Stable orbits for eccentric horseshoe
configurations exist with a pericentre closer than seven binary separations
and, in the case of Kepler-413, the pericentre of the first stable orbit can be
approximated by $r_{c,peri} = (2.88 e_p + 2.46) a_{bin}$.
