- ID:
- ivo://CDS.VizieR/J/A+A/528/A111
- Title:
- GJ3634 radial velocity and 4.5um flux
- Short Name:
- J/A+A/528/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the detection of GJ3634b, a super-Earth of mass msini=7.0+/-0.9 Mearth and period P=2.64561+/-0.00066-day. Its host star is a M2.5 dwarf, has a mass of 0.45+/-0.05M_{sun}_, a radius of 0.43+/-0.03R_{sun}_ and lies 19.8+/-0.6pc away from our Sun. The planet is detected after a radial-velocity campaign using the ESO/Harps spectrograph. GJ3634b had an a priori geometric probability to undergo transit of ~7% and, if telluric in composition, a non-grazing transit would produce a photometric dip of <~0.1%. We therefore followed-up upon the RV detection with photometric observations using the 4.5-um band of the IRAC imager onboard Spitzer. Our six-hour long light curve excludes that a transit occurs for 2sigma of the probable transit window, decreasing the probability that GJ3634b undergoes transit to ~0.5%.
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- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A153
- Title:
- GJ 4276 radial velocity curve
- Short Name:
- J/A+A/622/A153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of a Neptune-mass exoplanet around the M4.0 dwarf GJ 4276 (G 232-070) based on radial velocity (RV) observations obtained with the CARMENES spectrograph. The RV variations of GJ 4276 are best explained by the presence of a planetary companion with a minimum mass of m_b_sini~16M_{sun}_ on a P_b_=13.35-day orbit. The analysis of the activity indicators and spectral diagnostics exclude stellar induced RV perturbations and prove the planetary interpretation of the RV signal. We show that a circular single-planet solution can be excluded by means of a likelihood ratio test. Instead, we find that the RV variations can either be explained by an eccentric orbit or interpreted as a pair of planets on circular orbits near a period ratio of 2:1. Although the eccentric single-planet solution is slightly preferred, our statistical analysis indicates that none of these two scenarios can be rejected with high confidence using the RV time series obtained so far. Based on the eccentric interpretation, we find that GJ 4276 b is the most eccentric (e_b_=0.37) exoplanet around an M dwarf with such a short orbital period known today.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A117
- Title:
- GJ 3998 RVs, S and Halpha indexes
- Short Name:
- J/A+A/593/A117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- M dwarfs are considered ideal targets for Doppler radial velocity searches. Nonetheless, the statistics of frequency of low-mass planets hosted by low mass stars remains poorly constrained. Our M-dwarf radial velocity monitoring with HARPS-N can provide a major contribution to the widening of the current statistics through the in-depth analysis of accurate radial velocity observations in a narrow range of spectral sub-types (79 stars, between dM0 to dM3). Spectral accuracy will enable us to reach the precision needed to detect small planets with a few earth masses. Our survey will bring a contribute to the surveys devoted to the search for planets around M-dwarfs, mainly focused on the M-dwarf population of the northern hemisphere, for which we will provide an estimate of the planet occurence. We present here a long duration radial velocity monitoring of the M1 dwarf star GJ 3998 with HARPS-N to identify periodic signals in the data. Almost simultaneous photometric observations were carried out within the APACHE and EXORAP programs to characterize the stellar activity and to distinguish from the periodic signals those due to activity and to the presence of planetary companions. The radial velocities have a dispersion in excess of their internal errors due to at least four superimposed signals, with periods of 30.7, 13.7, 42.5 and 2.65-days. The analysis of spectral indices based on Ca II H & K and H{alpha} lines demonstrates that the periods of 30.7 and 42.5-days are due to chromospheric inhomogeneities modulated by stellar rotation and differential rotation. The shorter periods of 13.74+/-0.02d and 2.6498+/-0.0008d are well explained with the presence of two planets, with minimum masses of 6.26+/-0.79M_Earth_ and 2.47+/-0.27M_Earth_ and distances of 0.089AU and 0.029AU from the host, respectively.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/563/A21
- Title:
- GJ 1214 Trappist and Spitzer light curves
- Short Name:
- J/A+A/563/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-precision eclipse spectrophotometry of transiting terrestrial exoplanets represents a promising path for the first atmospheric characterizations of habitable worlds and the search for life outside our solar system. The detection of terrestrial planets transiting nearby late-type M-dwarfs could make this approach applicable within the next decade, with soon-to-come general facilities. In this context, we previously identified GJ 1214 as a high-priority target for a transit search, as the transit probability of a habitable planet orbiting this nearby M4.5 dwarf would be significantly enhanced by the transiting nature of GJ 1214 b, the super-Earth already known to orbit the star. Based on this observation, we have set up an ambitious high-precision photometric monitoring of GJ 1214 with the Spitzer Space Telescope to probe the inner part of its habitable zone in search of a transiting planet as small as Mars. We present here the results of this transit search.
- 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.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/781/124
- Title:
- Granulation model for 508 KIC stars
- Short Name:
- J/ApJ/781/124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A large fraction of cool, low-mass stars exhibit brightness fluctuations that arise from a combination of convective granulation, acoustic oscillations, magnetic activity, and stellar rotation. Much of the short-timescale variability takes the form of stochastic noise, whose presence may limit the progress of extrasolar planet detection and characterization. In order to lay the groundwork for extracting useful information from these quasi-random signals, we focus on the origin of the granulation-driven component of the variability. We apply existing theoretical scaling relations to predict the star-integrated variability amplitudes for 508 stars with photometric light curves measured by the Kepler mission. We also derive an empirical correction factor that aims to account for the suppression of convection in F-dwarf stars with magnetic activity and shallow convection zones. So that we can make predictions of specific observational quantities, we performed Monte Carlo simulations of granulation light curves using a Lorentzian power spectrum. These simulations allowed us to reproduce the so-called flicker floor (i.e., a lower bound in the relationship between the full light-curve range and power in short-timescale fluctuations) that was found in the Kepler data. The Monte Carlo model also enabled us to convert the modeled fluctuation variance into a flicker amplitude directly comparable with observations. When the magnetic suppression factor described above is applied, the model reproduces the observed correlation between stellar surface gravity and flicker amplitude. Observationally validated models like these provide new and complementary evidence for a possible impact of magnetic activity on the properties of near-surface convection.
