The CARMENES search for exoplanets around M dwarfs

The warm super-Earths in twin orbits around the mid-type M dwarfs Ross 1020 (GJ 3779) and LP 819-052 (GJ 1265)^★

¹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
e-mail: rluque@iac.es
² Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
³ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁴ Institut für Astrophysik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
⁵ Institut de Ciències de l’Espai (ICE, CSIC), Campus UAB, c/ de Can Magrans s/n, 08193 Bellaterra, Barcelona, Spain
⁶ Institut d’Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain
⁷ Centro de Astrobiología (CSIC-INTA), ESAC Campus, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
⁸ Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
⁹ Landessternwarte, Zentrum für Astronomie der Universtät Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
¹⁰ Centro Astronómico Hispano-Alemán (CSIC-MPG), Observatorio Astronómico de Calar Alto, Sierra de los Filabres, 04550 Gérgal, Almería, Spain
¹¹ Departamento de Astrofísica y Ciencias de la Atmósfera, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
¹² Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
¹³ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
¹⁴ School of Geosciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel

Received: 14 May 2018
Accepted: 16 October 2018

Abstract

We announce the discovery of two planetary companions orbiting around the low-mass stars Ross 1020 (GJ 3779, M4.0V) and LP 819-052 (GJ 1265, M4.5V). The discovery is based on the analysis of CARMENES radial velocity (RV) observations in the visual channel as part of its survey for exoplanets around M dwarfs. In the case of GJ 1265, CARMENES observations were complemented with publicly available Doppler measurements from HARPS. The datasets reveal two planetary companions, one for each star, that share very similar properties: minimum masses of 8.0 ± 0.5 M_⊕ and 7.4 ± 0.5 M_⊕ in low-eccentricity orbits with periods of 3.023 ± 0.001 d and 3.651 ± 0.001 d for GJ 3779 b and GJ 1265 b, respectively. The periodic signals around 3 d found in the RV data have no counterpart in any spectral activity indicator. Furthermore, we collected available photometric data for the two host stars, which confirm that the additional Doppler variations found at periods of approximately 95 d can be attributed to the rotation of the stars. The addition of these planets to a mass-period diagram of known planets around M dwarfs suggests a bimodal distribution with a lack of short-period low-mass planets in the range of 2–5 M_⊕. It also indicates that super-Earths (>5 M_⊕) currently detected by RV and transit techniques around M stars are usually found in systems dominated by a single planet.