  Periodic radial velocity variations in the nearby M-dwarf star Gl411 are
reported, based on measurements with the SOPHIE spectrograph. Current data do
not allow us to distinguish between a 12.95-day period and its one-day alias at
1.08 days, but favour the former slightly. The velocity variation has an
amplitude of 1.6 m/s, making this the lowest-amplitude signal detected with
SOPHIE up to now. We have performed a detailed analysis of the significance of
the signal and its origin, including extensive simulations with both
uncorrelated and correlated noise, representing the signal induced by stellar
activity. The signal is significantly detected, and the results from all tests
point to its planetary origin. Additionally, the presence of an additional
acceleration in the velocity time series is suggested by the current data. On
the other hand, a previously reported signal with a period of 9.9 days,
detected in HIRES velocities of this star, is not recovered in the SOPHIE data.
An independent analysis of the HIRES dataset also fails to unveil the 9.9-day
signal.
  If the 12.95-day period is the real one, the amplitude of the signal detected
with SOPHIE implies the presence of a planet, called Gl411 b, with a minimum
mass of around three Earth masses, orbiting its star at a distance of 0.079 AU.
The planet receives about 3.5 times the insolation received by Earth, which
implies an equilibrium temperature between 255 K and 350 K, and makes it too
hot to be in the habitable zone. At a distance of only 2.5 pc, Gl411 b, is the
third closest low-mass planet detected to date. Its proximity to Earth will
permit probing its atmosphere with a combination of high-contrast imaging and
high-dispersion spectroscopy in the next decade.

Earth and Planetary Astrophysics