Comment on "Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581"

This document is the Accepted Manuscript Version of the following article: Guillem Anglada-Escude and Mikko Tuomi, 'Comment on "Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581"', Science, Vol 347 (6226), 2015, the final, published version is available online at doi: 10.1126/science.1260796. © 2015 The American Association for the Advancement of Science. All rights reserved.Robertson et al. (Reports, 25 July 2014, p. 440) claimed that activity-induced variability is responsible for the Doppler signal of the proposed planet candidate GJ 581d. We point out that their analysis using periodograms of residual data is inappropriate and promotes inadequate tools. Because the claim challenges the viability of the method to detect exo-Earths, we encourage reanalysis and a deliberation on what the field-standard methods should be.Peer reviewe

Evidence of a massive planet candidate orbiting the young active K5V star BD+20 1790

Original article can be found at: http://www.aanda.org/ Copyright The European Southern Observatory (ESO). DOI: 10.1051/0004-6361/200811000Context. BD+20 1790 is a young active, metal-rich, late-type K5Ve star. We have undertaken a study of stellar activity and kinematics for this star over the past few years. Previous results show a high level of stellar activity, with the presence of prominence-like structures, spots on the surface, and strong flare events, despite the moderate rotational velocity of the star. In addition, radial velocity variations with a semi-amplitude of up to 1 km s-1 were detected. Aims. We investigate the nature of these radial velocity variations, in order to determine whether they are due to stellar activity or the reflex motion of the star induced by a companion. Methods. We have analysed high-resolution echelle spectra by measuring stellar activity indicators and computing radial velocity (RV) and bisector velocity spans. Two-band photometry was also obtained to produce the light curve and determine the photometric period. Results. Based upon the analysis of the bisector velocity span, as well as spectroscopic indices of chromospheric indicators, Ca ii H & K, Hα, and taking the photometric analysis into account, we report that the best explanation for the RV variation is the presence of a substellar companion. The Keplerian fit of the RV data yields a solution for a close-in massive planet with an orbital period of 7.78 days. The presence of the close-in massive planet could also be an interpretation for the high level of stellar activity detected. Since the RV data are not part of a planet search programme, we can consider our results as a serendipitous evidence of a planetary companion. To date, this is the youngest main sequence star for which a planetary candidate has been reported.Peer reviewe

The Carnegie Astrometric Planet Search Program

We are undertaking an astrometric search for gas giant planets and brown dwarfs orbiting nearby low mass dwarf stars with the 2.5-m du Pont telescope at the Las Campanas Observatory in Chile. We have built two specialized astrometric cameras, the Carnegie Astrometric Planet Search Cameras (CAPSCam-S and CAPSCam-N), using two Teledyne Hawaii-2RG HyViSI arrays, with the cameras' design having been optimized for high accuracy astrometry of M dwarf stars. We describe two independent CAPSCam data reduction approaches and present a detailed analysis of the observations to date of one of our target stars, NLTT 48256. Observations of NLTT 48256 taken since July 2007 with CAPSCam-S imply that astrometric accuracies of around 0.3 milliarcsec per hour are achievable, sufficient to detect a Jupiter-mass companion orbiting 1 AU from a late M dwarf 10 pc away with a signal-to-noise ratio of about 4. We plan to follow about 100 nearby (primarily within about 10 pc) low mass stars, principally late M, L, and T dwarfs, for 10 years or more, in order to detect very low mass companions with orbital periods long enough to permit the existence of habitable, Earth-like planets on shorter-period orbits. These stars are generally too faint and red to be included in ground-based Doppler planet surveys, which are often optimized for FGK dwarfs. The smaller masses of late M dwarfs also yield correspondingly larger astrometric signals for a given mass planet. Our search will help to determine whether gas giant planets form primarily by core accretion or by disk instability around late M dwarf stars.Comment: 48 pages, 9 figures. in press, Publ. Astron. Soc. Pacifi

TRIGONOMETRIC PARALLAXES AND PROPER MOTIONS OF 134 SOUTHERN LATE M, L, AND T DWARFS FROM THE CARNEGIE ASTROMETRIC PLANET SEARCH PROGRAM

This work has beensupported in part by NSF grant AST-0352912, NASA Origins of Solar Systems grant NNX09AF62G, and NASA Astrobiology Institute grant NNA09DA81A This publication made use of the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5- 26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts

Measuring the masses of the habitable planets around the 50 closest solar-type stars with Theia

A major goal of exoplanetary science is the search for possible biosignatures on planets where life similar to ours would have emerged and modified the atmosphere. These planets can be detected by remote sensing using spectroscopic observation of O2, O3, H2O, CO2, and CH4 gases, but in the present context of funding, only missions in the range B$1-2 are seen as feasible for the next decades. This cost cap imposes serious constraints on the number of accessible targets limiting the exploration to the 20 nearest systems with space coronagraphy in the visible wavelength range and 40 systems with space interferometers working in thermal IR. It is thus imperative that promising target be identified ahead of time, to minimize several classes of risks intrinsic to the 'blind search' approach. Furthermore, the masses and the three-dimensional orbits of such habitable planets are key elements for deriving exobiological statements in the future, even the most basic ones. The mission called Theia has been submitted to the ESA call for M4 mission in 2015. Theia is a space observatory able to carry out high precision differential astrometry at the sub-microarcsecond level that allows mass determination of Earth-mass habitable planets around the 50 closest Solar-type stars using 15 - 20 % of the time of a three years mission. Theia is a single telescope designed to perform high accuracy astrometry using interferometric calibration and operating in L2. We will present the mission and its capability to measure the mass and orbit characteristics of the 50 closest planetary systems down to the Earth mass in the habitable zone of solar-type stars

A low-mass planet candidate orbiting Proxima Centauri at a distance of 1.5 AU

Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).Our nearest neighbor, Proxima Centauri, hosts a temperate terrestrial planet. We detected in radial velocities evidence of a possible second planet with minimum mass m c sin i c = 5.8 ± 1.9 M ⊕ and orbital period P c = 5.21 - 0.22 + 0.26 years. The analysis of photometric data and spectro-scopic activity diagnostics does not explain the signal in terms of a stellar activity cycle, but follow-up is required in the coming years for confirming its planetary origin. We show that the existence of the planet can be ascertained, and its true mass can be determined with high accuracy, by combining Gaia astrometry and radial velocities. Proxima c could become a prime target for follow-up and characterization with next-generation direct imaging instrumentation due to the large maximum angular separation of ~1 arc second from the parent star. The candidate planet represents a challenge for the models of super-Earth formation and evolution.Peer reviewedFinal Published versio

HiFLEx – a highly flexible package to reduce cross-dispersed Echelle spectra

© 2020 The Astronomical Society of the Pacific. Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence (https://creativecommons.org/licenses/by/3.0/). Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.We describe a flexible data reduction package for high resolution cross-dispersed echelle data. This open-source package is developed in Python and includes optional GUIs for most of the steps. It does not require any pre-knowledge about the form or position of the echelle-orders. It has been tested on cross-dispersed echelle spectrographs between 13k and 115k resolution (bifurcated fiber-fed spectrogaph ESO-HARPS and single fiber-fed spectrograph TNT-MRES). HiFLEx can be used to determine radial velocities and is designed to use the TERRA package but can also control the radial velocity packages such as CERES and SERVAL to perform the radial velocity analysis. Tests on HARPS data indicates radial velocities results within ±3ms−1 of the literature pipelines without any fine tuning of extraction parameters.Peer reviewe