We report the detection of the secondary eclipse of HAT-P-11 b , a Neptune-sized planet orbiting an active K4 dwarf .
Using all available short-cadence data of the Kepler mission , we derive refined planetary ephemeris increasing their precision by more than an order of magnitude .
Our simultaneous primary and secondary transit modeling results in improved transit and orbital parameters .
In particular , the precise timing of the secondary eclipse allows to pin down the orbital eccentricity to 0.26459 _ { -0.00048 } ^ { +0.00069 } .
The secondary eclipse depth of 6.09 _ { -1.11 } ^ { +1.12 } ppm corresponds to a 5.5 \sigma detection and results in a geometric albedo of 0.39 \pm 0.07 for HAT-P-11 b , close to Neptune ’ s value , which may indicate further resemblances between these two bodies .
Due to the substantial orbital eccentricity , the planetary equilibrium temperature is expected to change significantly with orbital position and ought to vary between 630 ^ { \circ } K and 950 ^ { \circ } K , depending on the details of heat redistribution in the atmosphere of HAT-P-11 b .