The CARMENES search for exoplanets around M dwarfs

Abstract

Context. Detecting a planetary companion in a short-period orbit through radio emission from the interaction with its host star is a new prospect in exoplanet science. Recently, a tantalising signal was found close to the low-mass stellar system GJ 1151 using LOFAR observations. Aims. We studied spectroscopic time-series data of GJ 1151 in order to search for planetary companions, investigate possible signatures of stellar magnetic activity, and to find possible explanations for the radio signal. Methods. We used the combined radial velocities measured from spectra acquired with the CARMENES, HARPS-N, and HPF instruments, extracted activity indices from those spectra in order to mitigate the impact of stellar magnetic activity on the data, and performed a detailed analysis of Gaia astrometry and all available photometric time series coming from the MEarth and ASAS-SN surveys. Results. We found a M>10.6 M ⊕ companion to GJ 1151 in a 390d orbit at a separation of 0.57 au. Evidence for a second modulation is also present; this could be due to long-term magnetic variability or a second (substellar) companion. The star shows episodes of elevated magnetic activity, one of which could be linked to the observed LOFAR radio emission. We show that it is highly unlikely that the detected GJ 1151 b, or any additional outer companion is the source of the detected signal. We cannot firmly rule out the suggested explanation of an undetected short-period planet that could be related to the radio emission, as we establish an upper limit of 1.2 M ⊕ for the minimum mass.

Hunting for exoplanets via magnetic star–planet interactions: geometrical considerations for radio emission

“…This is consistent with the driving mechanism being magnetospheric in origin. Yet, none of these stars are known to host close-in planets, leaving the interpretation ambiguous (see ho we ver the recent detection by Blanco-Pozo et al 2023 ). If the detected emission from these systems is in fact due to the presence of undisco v ered companions, there is the question of is there something special about these systems?…”

Forming Gas Giants around a Range of Protostellar M-dwarfs by Gas Disk Gravitational Instability

“…Over the last decade, Doppler surveys are increasingly extending their target lists to include M-dwarfs (Bonfils et al 2013;Feng et al 2020) or are exclusively targetting M-dwarfs (Mahadevan et al 2014;Kotani et al 2018;Sabotta et al 2021). M-dwarf exoplanets have been found by Doppler spectroscopy with minimum masses ranging from Earth-mass (e.g., Kossakowski et al 2023), to Neptune-mass (e.g., Blanco-Pozo et al 2023;Stefansson et al 2023), to Jupiter-mass (e.g., Endl et al 2022), to super-Jupiter-mass (e.g., Sozzetti et al 2023). In comparison to the constrained Kepler fields of view, the Transiting Exoplanet Survey Satellite (TESS) mission targets stars distributed across the entire sky, and hence can detect the transiting exoplanets orbiting relatively bright nearby M-dwarfs (Muirhead et al 2018).…”

The CARMENES search for exoplanets around M dwarfs

“…Time series like this have been provided by the CARMENES survey for more than 300 M-dwarf stars (Reiners et al 2018). In recent years, our individual telluric-corrected spectra as well as telluric-corrected template spectra have been used in the context of planet detection (e.g., Polanski et al 2021;Blanco-Pozo et al 2023;Kossakowski et al 2023), atmospheric characterization (e.g., Nortmann et al 2018Salz et al 2018;Alonso-Floriano et al 2019;Palle et al 2020;Orell-Miquel et al 2022, magnetic field measurements (Shulyak et al 2019;Reiners et al 2022), photospheric parameter determinations (Passegger et al 2019(Passegger et al , 2020Marfil et al 2020Marfil et al , 2021, abundance analyses (Abia et al 2020;Shan et al 2021), or chromospheric activity studies (Fuhrmeister et al 2019(Fuhrmeister et al , 2020(Fuhrmeister et al , 2022(Fuhrmeister et al , 2023Hintz et al 2020Hintz et al , 2023. Here, we apply TDTM, which is publicly available 3 , to the CARMENES survey spectra and subsequently construct telluric-free template spectra with a high signal-to-noise ratio (S/N) for the stars in our sample.…”