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Start Over Subject exoplanets Validation Level 2
101. GJ 1151 radial velocity curve
ID:
ivo://CDS.VizieR/J/A+A/649/L12
Title:
GJ 1151 radial velocity curve
Short Name:
J/A+A/649/L12
Date:
22 Feb 2022
Publisher:
CDS
Description:
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_{earth}_ planet orbiting GJ 1151 with a 2-day period has been claimed using 69 radial velocities (RVs) from the HARPS-N and HPF instruments. 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. 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. 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 1.50m/s in the RV semi-amplitude, which places upper limits of 0.7M_{earth}_ and 1.2M_{earth}_ on the minimum masses of potential exoplanets with orbital periods of 1 and 5 days, respectively.
102. GJ 3473 (TOI-488) radial velocity curve
ID:
ivo://CDS.VizieR/J/A+A/642/A236
Title:
GJ 3473 (TOI-488) radial velocity curve
Short Name:
J/A+A/642/A236
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the confirmation and characterisation of GJ 3473 b (G 50-16, TOI-488.01), a hot Earth-sized planet orbiting an M4 dwarf star, whose transiting signal (P=1.1980035+/-0.0000018d) was first detected by the Transiting Exoplanet Survey Satellite (TESS). Through a joint modelling of follow-up radial velocity observations with CARMENES, IRD, and HARPS together with extensive ground-based photometric follow-up observations with LCOGT, MuSCAT, and MuSCAT2, we determined a precise planetary mass, M_b_=1.86+/-0.30M_{sun}_, and radius, R_b_=1.264+/-0.050R_{sun}_. Additionally, we report the discovery of a second, temperate, non-transiting planet in the system, GJ 3473 c, which has a minimum mass, M_c_sini=7.41+/-0.91M_{sun}_ and orbital period, P_c_=15.509+/-0.033d. The inner planet of the system, GJ 3473 b, is one of the hottest transiting Earth- sized planets known thus far, accompanied by a dynamical mass measurement, which makes it a particularly attractive target for thermal emission spectroscopy.
103. Gl617A and Gl96 radial velocity curves
ID:
ivo://CDS.VizieR/J/A+A/618/A103
Title:
Gl617A and Gl96 radial velocity curves
Short Name:
J/A+A/618/A103
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the detection of two exoplanets and a further tentative candidate around the M-dwarf stars Gl96 and Gl617A, based on radial velocity measurements obtained with the SOPHIE spectrograph at the Observatoire de Haute-Provence. Both stars were observed in the context of the SOPHIE exoplanet consortium's dedicated M-dwarf subprogramme, which aims to detect exoplanets around nearby M-dwarf stars through a systematic survey. For Gl96 we present the discovery of a new exoplanet at 73.9d with a minimum mass of 19.66 earth masses. Gl96b has an eccentricity of 0.44, placing it among the most eccentric planets orbiting M stars. For Gl617A we independently confirm a recently reported exoplanet at 86.7d with a minimum mass of 31.29 earth masses. Both Gl96 b and Gl617Ab are potentially within the habitable zone, though the high eccentricity of Gl96 b may take it too close to the star at periapsis.
104. Gl 49 radial velocities and activity indicators
ID:
ivo://CDS.VizieR/J/A+A/624/A123
Title:
Gl 49 radial velocities and activity indicators
Short Name:
J/A+A/624/A123
Date:
21 Oct 2021
Publisher:
CDS
Description:
Small planets around low-mass stars often show orbital periods in a range that corresponds to the temperate zones of their host stars which are therefore of prime interest for planet searches. Surface phenomena such as spots and faculae create periodic signals in radial velocities and in observational activity tracers in the same range, so they can mimic or hide true planetary signals. We aim to detect Doppler signals corresponding to planetary companions, determine their most probable orbital configurations, and understand the stellar activity and its impact on different datasets. We analyzed 22 years of data of the M1.5V-type star Gl 49 (BD+61 195) including HARPS-N and CARMENES spectrographs, complemented by APT2 and SNO photometry. Activity indices are calculated from the observed spectra, and all datasets are analyzed with periodograms and noise models. We investigated how the variation of stellar activity imprints on our datasets. We further tested the origin of the signals and investigate phase shifts between the different sets. To search for the best-fit model we maximize the likelihood function in a Markov chain Monte Carlo approach. As a result of this study, we are able to detect the super-Earth Gl 49b with a minimum mass of 5.6M_{earth}_. It orbits its host star with a period of 13.85d at a semi-major axis of 0.090au and we calculate an equilibrium temperature of 350K and a transit probability of 2.0%. The contribution from the spot-dominated host star to the different datasets is complex, and includes signals from the stellar rotation at 18.86d, evolutionary timescales of activity phenomena at 40-80d, and a long-term variation of at least four years.
105. Gl686 RV curves and BVR photometry
ID:
ivo://CDS.VizieR/J/A+A/622/A193
Title:
Gl686 RV curves and BVR photometry
Short Name:
J/A+A/622/A193
Date:
21 Oct 2021
Publisher:
CDS
Description:
The HArps-n red Dwarf Exoplanet Survey is providing a major contribution to the widening of the current statistics of low-mass planets, through the in-depth analysis of precise radial velocity measurements in a narrow range of spectral sub-types. Using the HARPS-N spectrograph we reach the precision needed to detect small planets with a few earth masses. Our survey is mainly focused on the M-dwarf population of the northern hemisphere. As part of that programme, we obtained radial velocity measurements of Gl686, an M1 dwarf at d=8.2pc. These measurements show a dispersion much in excess of their internal errors. The analysis of data obtained within an intensive observing campaign, demonstrates that the excess dispersion is due to a coherent signal, with a period of 15.53d. Almost simultaneous photometric observations were carried out within the APACHE and EXORAP programmes to characterize the stellar activity and to distinguish periodic variations related to activity from signals due to the presence of planetary companions, complemented also with ASAS photometric data. We used a Bayesian framework to estimate the orbital parameters and the planet minimum mass, and to properly treat the activity noise. We took advantage of the available radial velocity measurements for this target from other observing campaigns. The analysis of the radial velocity composite time series from the HIRES, HARPS and HARPS-N spectrographs, consisting of 198 measurements taken over 20 years, enabled us to address the nature of periodic signals and also to characterize stellar physical parameters (mass, temperature and rotation). We report the discovery of a super-Earth orbiting at a distance of 0.092AU from the host star Gl686. Gl686 b has a minimum mass of 7.1+/-0.9M_{Earth} and an orbital period of 15.532+/-0.002d. The analysis of the activity indexes, correlated noise through a Gaussian process framework and photometry, provides an estimate of the stellar rotation period at 37d, and highlights the variability of the spot configuration during the long timespan covering 20yrs. The observed periodicities around 2000d likely point to the existence of an activity cycle.
106. Ground-based spectroscopy of the exoplanet XO-2b
ID:
ivo://CDS.VizieR/J/AJ/157/21
Title:
Ground-based spectroscopy of the exoplanet XO-2b
Short Name:
J/AJ/157/21
Date:
21 Oct 2021
Publisher:
CDS
Description:
Exoplanets orbiting close to their host star are expected to support a large ionosphere, which extends to larger pressures than witnessed in our solar system. These ionospheres can be investigated with ground-based transit observations of the optical signatures of alkali metals, which are the source of the ions. However, most ground-based transit spectra do not systematically resolve the wings of the features and continuum, as needed to constrain the alkali abundances. Here we present new observations and analyses of optical transit spectra that cover the Na doublet in the atmosphere of the exoplanet XO-2b. To assess the consistency of our results, observations were obtained from two separate platforms: Gemini/GMOS and Mayall/KOSMOS. To mitigate the systematic errors, we chose XO-2, because it has a binary companion of the same brightness and stellar type, which provides an ideal reference star to model Earth's atmospheric effects. We find that interpretation of the data is highly sensitive to time-varying translations along the detector, which change according to wavelength and differ between the target and reference star. It was necessary to employ a time-dependent cross-correlation to align our wavelength bins and correct for atmospheric differential refraction. This approach allows us to resolve the wings of the Na line across five wavelength bins at a resolution of ~1.6 nm and limit the abundance of Na. We obtain consistent results from each telescope with an Na amplitude of 521+/-161 and 403+/-186 ppm for GMOS and KOSMOS, respectively. The results are analyzed with a radiative transfer model that includes the effects of ionization. The data are consistent with a clear atmosphere between ~1 and 100 mbar that establishes a lower limit on Na at 0.4_-0.3_^+2^ ppm ([Na/H]=-0.64_-0.6_^+0.78^), consistent with solar. However, we cannot rule out the presence of clouds at ~10 mbar that allow for higher Na abundances, which would be consistent with the stellar metallicity measured for the host star ([Na/H]=0.485+/-0.043).
107. GTC transit light curves of HAT-P-11b
ID:
ivo://CDS.VizieR/J/A+A/622/A172
Title:
GTC transit light curves of HAT-P-11b
Short Name:
J/A+A/622/A172
Date:
21 Oct 2021
Publisher:
CDS
Description:
Rayleigh scattering in a hydrogen-dominated exoplanet atmosphere can be detected using ground- or space-based telescopes. However, stellar activity in the form of spots can mimic Rayleigh scattering in the observed transmission spectrum. Quantifying this phenomena is key to our correct interpretation of exoplanet atmospheric properties. We obtained Gran Telescopio Canarias (GTC) long-slit optical spectroscopy of two transits of HAT-P-11b with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) on August 30, 2016 and September 25, 2017. By fitting both transits together, we find a slope in the transmission spectrum showing an increase of the planetary radius towards blue wavelengths. Closer inspection of the transmission spectrum of the individual data sets reveals that the first transit presents this slope while the transmission spectrum of the second data set is flat. Additionally, we detect hints of Na absorption on the first night, but not on the second. We conclude that the transmission spectrum slope and Na absorption excess found in the first transit observation are caused by unocculted stellar spots. Modeling the contribution of unocculted spots to reproduce the results of the first night we find a spot filling factor of delta=0.62^+0.20^_-0.17_ and a spot-to-photosphere temperature difference of {Delta}T=429^+184^_-299_K.
108. HARPS, HIRES and AAT Radial Velocities of HD 136352
ID:
ivo://CDS.VizieR/J/AJ/160/129
Title:
HARPS, HIRES and AAT Radial Velocities of HD 136352
Short Name:
J/AJ/160/129
Date:
21 Oct 2021
Publisher:
CDS
Description:
Some of the most scientifically valuable transiting planets are those that were already known from radial velocity (RV) surveys. This is primarily because their orbits are well characterized and they preferentially orbit bright stars that are the targets of RV surveys. The Transiting Exoplanet Survey Satellite (TESS) provides an opportunity to survey most of the known exoplanet systems in a systematic fashion to detect possible transits of their planets. HD136352 (Nu Lupi) is a naked-eye (V=5.78) G-type main-sequence star that was discovered to host three planets with orbital periods of 11.6, 27.6, and 108.1days via RV monitoring with the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph. We present the detection and characterization of transits for the two inner planets of the HD136352 system, revealing radii of 1.482_-0.056_^+0.058^ R{Earth} and 2.608_-0.077_^+0.078^ R{Earth} for planets b and c, respectively. We combine new HARPS observations with RV data from the Keck/High Resolution Echelle Spectrometer and the Anglo-Australian Telescope, along with TESS photometry from Sector 12, to perform a complete analysis of the system parameters. The combined data analysis results in extracted bulk density values of {rho}_b_=7.8_-1.1_^+1.2^g/cm3 and {rho}_c_=3.50_-0.36_^+0.41^g/cm3 for planets b and c, respectively, thus placing them on either side of the radius valley. The combination of the multitransiting planet system, the bright host star, and the diversity of planetary interiors and atmospheres means this will likely become a cornerstone system for atmospheric and orbital characterization of small worlds.
109. HARPS-N observations of K2-141 planetary system
ID:
ivo://CDS.VizieR/J/AJ/155/107
Title:
HARPS-N observations of K2-141 planetary system
Short Name:
J/AJ/155/107
Date:
21 Oct 2021
Publisher:
CDS
Description:
Ultra-short period (USP) planets are a class of low-mass planets with periods shorter than one day. Their origin is still unknown, with photo-evaporation of mini-Neptunes and in situ formation being the most credited hypotheses. Formation scenarios differ radically in the predicted composition of USP planets, and it is therefore extremely important to increase the still limited sample of USP planets with precise and accurate mass and density measurements. We report here the characterization of a USP planet with a period of 0.28 days around K2-141 (EPIC 246393474), and the validation of an outer planet with a period of 7.7 days in a grazing transit configuration. We derived the radii of the planets from the K2 light curve and used high-precision radial velocities gathered with the HARPS-N spectrograph for mass measurements. For K2-141b, we thus inferred a radius of 1.51+/-0.05 R_{Earth}_ and a mass of 5.08+/-0.41 M_{Earth}_, consistent with a rocky composition and lack of a thick atmosphere. K2-141c is likely a Neptune-like planet, although due to the grazing transits and the non-detection in the RV data set, we were not able to put a strong constraint on its density. We also report the detection of secondary eclipses and phase curve variations for K2-141b. The phase variation can be modeled either by a planet with a geometric albedo of 0.30+/-0.06 in the Kepler bandpass, or by thermal emission from the surface of the planet at ~3000 K. Only follow-up observations at longer wavelengths will allow us to distinguish between these two scenarios.
110. HARPS-N radial velocities of WASP-47
ID:
ivo://CDS.VizieR/J/AJ/154/237
Title:
HARPS-N radial velocities of WASP-47
Short Name:
J/AJ/154/237
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present precise radial velocity observations of WASP-47, a star known to host a hot Jupiter, a distant Jovian companion, and, uniquely, two additional transiting planets in short-period orbits: a super-Earth in a ~19 hr orbit, and a Neptune in a ~9 day orbit. We analyze our observations from the HARPS-N spectrograph along with previously published data to measure the most precise planet masses yet for this system. When combined with new stellar parameters and reanalyzed transit photometry, our mass measurements place strong constraints on the compositions of the two small planets. We find that, unlike most other ultra-short-period planets, the inner planet, WASP-47 e, has a mass (6.83+/-0.66 M_{Earth}_) and a radius (1.810+/-0.027 R_{Earth}_) that are inconsistent with an Earth-like composition. Instead, WASP-47 e likely has a volatile-rich envelope surrounding an Earth-like core and mantle. We also perform a dynamical analysis to constrain the orbital inclination of WASP-47 c, the outer Jovian planet. This planet likely orbits close to the plane of the inner three planets, suggesting a quiet dynamical history for the system. Our dynamical constraints also imply that WASP-47 c is much more likely to transit than a geometric calculation would suggest. We calculate a transit probability for WASP-47 c of about 10%, more than an order of magnitude larger than the geometric transit probability of 0.6%.