Nondetection of the Neptune-mass planet reported around GJ 176

Endl et al. reported a Neptune-mass planet in a 10.24 day orbit around GJ 176. This planet has raised interest because of its low mass (Msin i = 24 M Earth), correspondingly small velocity amplitude (K = 11.7 m s^-1), and because GJ 176 is an M star. We report 41 precise Doppler measurements of GJ 176 obtained with the Keck-HIRES spectrometer over a 10 year time span. These measurements show no evidence of the 10.24 day companion, at a threshold of 4 m s^-1, a factor of 3 less than the amplitude reported by Endl et al. The Keck velocities are consistent with instrumental noise and stellar jitter. The existence of the planet is thus called into question.