The CARMENES search for exoplanets around M dwarfs. No evidence for a super-Earth in a 2-day orbit around GJ 1151

Context. The interaction between Earth-like exoplanets and the magnetic field of low-mass host stars are considered to produce weak emission signals at radio frequencies. A study using LOFAR data announced the detection of radio emission from the mid M-type dwarf GJ 1151 that could potentially arise from a close-in terrestrial planet. Recently, the presence of a 2.5-M<SUB>⊕</SUB> planet orbiting GJ 1151 with a 2-day period has been claimed using 69 radial velocities (RVs) from the HARPS-N and HPF instruments. <BR /> Aims: We have obtained 70 new high-precision RV measurements in the framework of the CARMENES M-dwarf survey and use these data to confirm the presence of the claimed planet and to place limits on possible planetary companions in the GJ 1151 system. <BR /> Methods: We analysed the periodicities present in the combined RV data sets from all three instruments and calculated the detection limits for potential planets in short-period orbits. <BR /> Results: We cannot confirm the recently announced candidate planet and conclude that the 2-day signal in the HARPS-N and HPF data sets is most probably produced by a long-term RV variability, possibly arising from an outer planetary companion that has yet to be constrained. We calculate a 99.9% significance detection limit of 1.50 m s<SUP>−1</SUP> in the RV semi-amplitude, which places upper limits of 0.7 M<SUB>⊕</SUB> and 1.2 M<SUB>⊕</SUB> on the minimum masses of potential exoplanets with orbital periods of 1 and 5 days, respectively. <P />Table A.1 is only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr/">cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/649/L12">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/649/L12</A>