We have confirmed the existence of the transiting super Neptune extrasolar planet HAT-P-11b .
On May 1 , 2009 UT the transit of HAT-P-11b was detected at the University of Arizona ’ s 1.55m Kuiper Telescope with 1.7 millimag rms accuracy .
We find a central transit time of T _ { c } = 2454952.92534 \pm 0.00060 BJD ; this transit occurred 80 \pm 73 seconds sooner than previous measurements ( 71 orbits in the past ) would have predicted .
Hence , our transit timing rules out the presence of any large ( > 200 s ) deviations from the ephemeris of Bakos et al .
( 2009 ) .
We obtain a slightly more accurate period of P = 4.8878045 \pm 0.0000043 days .
We measure a slightly larger planetary radius of R _ { p } = 0.452 \pm 0.020 R _ { J } ( 5.07 \pm 0.22 R _ { \earth } ) compared to Bakos and co-workers ’ value of 0.422 \pm 0.014 R _ { J } ( 4.73 \pm 0.16 R _ { \earth } ) .
Our values confirm that HAT-P-11b is very similar to GJ 436b ( the only other known transiting super Neptune ) in radius and other bulk properties .