Suchergebnisse

Small low-mass stars are favourable targets for the detection of rocky habitable planets. In particular, planetary systems in the solar neighbourhood are interesting and suitable for precise characterization. The RedDots campaigns seek to discover rocky planets orbiting nearby low-mass stars. The 2018 campaign targeted GJ 1061, which is the 20th nearest star to the Sun. For three consecutive months we obtained nightly, high-precision radial velocity measurements with the HARPS spectrograph. We analysed these data together with archival HARPS data. We report the detection of three planet candidates with periods of 3.204 +/- 0.001, 6.689 +/- 0.005, and 13.03 +/- 0.03 d, which are close to 1:2:4 period commensurability. After several considerations related to the properties of the noise and sampling, we conclude that a fourth signal is most likely explained by stellar rotation, although it may be due to a planet. The proposed three-planet system (and the potential four-planet solution) is long-term dynamically stable. Planet-planet gravitational interactions are below our current detection threshold. The minimum masses of the three planets range from 1.4 +/- 0.2 to 1.8 +/- 0.3 M-circle plus. Planet d, with msin i = 1.64 +/- 0.24 M-circle plus, receives a similar amount of energy as Earth receives from the Sun. Consequently it lies within the liquid-water habitable zone of the star and has a similar equilibrium temperature to Earth. GJ 1061 has very similar properties to Proxima Centauri but activity indices point to lower levels of stellar activity. ; German Research Foundation (DFG) FOR2544 DR 281/32-1 JE 701/3-1 DFG priority program SPP 1992 'Ex-ploring the Diversity of Extrasolar Planets' RE 1664/18 Spanish Agencia Estatal de Investigacion AYA201679425-C3-3-P ESP2017-87676-C5-2-R ESP2017-87143-R Centre of Excellence 'Severo Ochoa' Instituto de Astrof'rasolar Planets' SEV-2017-0709 Science & Technology Facilities Council (STFC) ST/P000584/1 3180405 Spanish Ministry for Science, Innovation and Universities (MCIU) European Union (EU) ESP2016-80435-C2-1-R ESP2016-80435-C2-2-R Generalitat de Catalunya/CERCA programme STFC Consolidated Grant ST/P000592/1 Alfried Krupp von Bohlen und Halbach Foundation Mc Donald Observatory of the University of Texas at Austin National Research Foundation - South Africa 072.C-0488 183.C-0437 0101.C-0516(A) 198.C-0838(A)

The search for Earth-like planets around late-type stars using ultrastable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, since these phenomena induce radial velocity (RV) signals that can be misinterpreted as planetary signals. Among the nearby stars, we have selected Barnard's Star (Gl 699) to carry out a characterization of these phenomena using a set of spectroscopic data that covers about 14.5yr and comes from seven different spectrographs: HARPS, HARPS-N, CARMENES, HIRES, UVES, APF, and PFS; and a set of photometric data that covers about 15.1yr and comes from four different photometric sources: ASAS, FCAPT-RCT, AAVSO, and SNO. We have measured different chromospheric activity indicators (H alpha, CaiiHK, and Nai D), as well as the full width at half-maximum (FWHM), of the cross-correlation function computed for a sub-set of the spectroscopic data. The analysis of generalized Lomb-Scargle periodograms of the time series of different activity indicators reveals that the rotation period of the star is 145 +/- 15d, consistent with the expected rotation period according to the low activity level of the star and previous claims. The upper limit of the predicted activity-induced RV signal corresponding to this rotation period is about 1ms(-1). We also find evidence of a long-term cycle of 10 +/- 2yr that is consistent with previous estimates of magnetic cycles from photometric time series in other M stars of similar activity levels. The available photometric data of the star also support the detection of both the long-term and the rotation signals.© 2019 The Author(s).Published by Oxford University Press on behalf of the Royal Astronomical Society ; This work has been financed by the Spanish Ministry of Science, Innovation and Universities (MICIU) through the grant AYA2017-86389-P. BTP acknowledges Fundacion La Caixa for the financial support received in the form of a Ph.D. contract. JIGH acknowledges financial support from the Spanish MICIU under the 2013 Ramon y Cajal program MICIU RYC-2013-14875. ASM acknowledges financial support from the Swiss National Science Foundation (SNSF). The IAA-CSIC and UCM teams acknowledge support by the Spanish Ministry of Economy and Competitiveness (MINECO) through grants AYA2016-79425-C3-1-P, AYA2016-79425-C3-2-P, AYA2016-79425-C3-3-P, ESP2014-54362P, and ESP2017-87143R. IR, JCM, MP, and EHacknowledge support from the Spanish MINECO and the Fondo Europeo de Desarrollo Regional (FEDER) through grant ESP2016-80435-C2-1-R, as well as the support of the Generalitat de Catalunya/CERCA program. GAE research is funded via the STFC Consolidated Grants ST/P000592/1, and a Perren foundation grant. The results of this paper were based on observations made with the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the INAF-Fundacion Galileo Galilei at the Roque de Los Muchachos Observatory of the Instituto de Astrofisica de Canarias (IAC); observations made with the HARPS instrument on the ESO 3.6 m telescope at La Silla Observatory (Chile); observations made with the CARMENES instrument at the 3.5 m telescope of the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain), funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union, and the CARMENES Consortium members. This paper made use of the IAC Supercomputing facility HTCondor (http://research.cs.wisc.edu/htcondor/), partly financed by the Ministry of Economy and Competitiveness with FEDER funds, code IACA13-3E-2493. We are grateful to all the observers of the projects whose data we are using for the following spectrographs: HARPS (072.C-0488, 183.C-0437, 191.C-0505, 099.C-0880), HARPS-N (CAT14A_43, A27CAT_83, CAT13B_136, CAT16A_109, CAT17A_38, CAT17A_58), CARMENES (CARMENES GTO survey), HIRES (U11H, U11H, N12H, N10H, A264Hr, A288Hr, C168Hr, C199Hr, C205Hr, C202Hr, C232Hr, C240Hr, C275Hr, C332Hr, H174Hr, H218Hr, H238Hr, H224Hr, H244Hr, H257Hr, K01H, N007Hr, N014Hr, N024, N054Hr, N05H, N06H, N085Hr, N086Hr, N095Hr, N108Hr, N10H, N112Hr, N118Hr, N125Hr, N129HR, N12H, N12H, N131Hr, N131Hr, N136Hr, N141Hr, N145Hr, N148Hr, N14H, N157Hr, N15H, N168Hr, N19H, N20H, N22H, N28H, N32H, N50H, N59H, U014Hr, U01H, U023Hr, U027Hr, U027Hr, U030Hr, U052Hr, U058Hr, U05H, U064Hr, U077Hr, U078Hr, U07H, U082Hr, U084Hr, U08H, U10H, U115Hr, U11H, U12H, U131Hr, U142Hr, U66H, Y013Hr, Y065Hr, Y283Hr, Y292Hr), UVES (65.L-0428, 66.C-0446, 267.C-5700, 68.C0415, 69.C-0722, 70.C-0044, 71.C-0498, 072.C0495, 173.C-0606, 078.C-0829), APF (LCES/APF planet survey), and PFS (Carnegie-California survey).