- ID:
- ivo://CDS.VizieR/J/A+A/639/A50
- Title:
- HD 164922 d HARPS-N time series
- Short Name:
- J/A+A/639/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of exoplanetary systems show that a wide variety of architectures are possible. Determining the rate of occurrence of Solar System analogs - with inner terrestrial planets and outer gas giants - is still an open question. In the framework of the Global Architecture of Planetary Systems (GAPS) project we collected more than 300 spectra with HARPS-N at the Telescopio Nazionale Galileo for the bright G9V star HD164922. This target is known to host one gas giant planet in a wide orbit (Pb~1200-days, semi-major axis ~2au) and a Neptune-mass planet with a period Pc~76-days. Our aim was to investigate the presence of additional low-mass companions in the inner region of the system. We compared the radial velocities (RV) and the activity indices derived from the HARPS-N time series to measure the rotation period of the star and used a Gaussian process regression to describe the behaviour of the stellar activity.We exploited this information in a combined model of planetary and stellar activity signals in an RV time-series composed of almost 700 high-precision RVs, both from HARPS-N and literature data. We performed a dynamical analysis to evaluate the stability of the system and the allowed regions for additional potential companions. We performed experiments of injection and recovery of additional planetary signals to gauge the sensitivity thresholds in minimum mass and orbital separation imposed by our data. Thanks to the high sensitivity of the HARPS-N dataset, we detect an additional inner super-Earth with an RV semi-amplitude of 1.3+/-0.2m/s and a minimum mass of m_d_sini=4+/-/1M_{Earth}_. It orbits HD164922 with a period of 12.4580.003 days. We disentangle the planetary signal from activity and measure a stellar rotation period of ~42 days. The dynamical analysis shows the long term stability of the orbits of the three-planet system and allows us to identify the permitted regions for additional planets in the semi-major axis ranges 0.18-0.21au and 0.6-1.4au. The latter partially includes the habitable zone of the system. We did not detect any planet in these regions, down to minimum detectable masses of 5 and 18M_{Earth}_, respectively. A larger region of allowed planets is expected beyond the orbit of planet b, where our sampling rules-out bodies with minimum mass >50MM_{Earth}. The planetary orbital parameters and the location of the snow line suggest that this system has been shaped by a gas disk migration process that halted after its dissipation.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/135/68
- Title:
- HD 189733 differential light curve
- Short Name:
- J/AJ/135/68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present synoptic optical photometry of HD 189733, the chromospherically active parent star of one of the most intensively studied exoplanets. We have significantly extended the timespan of our previously reported observations and refined the estimate of the stellar rotation period by more than an order of magnitude: P=11.953+/-0.009-days. We derive a lower limit on the inclination of the stellar rotation axis of 54{deg} (with 95% confidence), corroborating earlier evidence that the stellar spin axis and planetary orbital axis are well aligned.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A138
- Title:
- HD 80606/80607 equivalent widths
- Short Name:
- J/A+A/614/A138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Differences in the elemental abundances of planet-hosting stars in binary systems can give important clues and constraints about planet formation and evolution. In this study we performed a high-precision, differential elemental abundance analysis of a wide binary system, HD 80606/80607, based on high-resolution spectra with high signal-to-noise ratio obtained with Keck/HIRES. HD 80606 is known to host a giant planet with the mass of four Jupiters, but no planet has been detected around HD 80607 so far. We determined stellar parameters as well as abundances for 23 elements for these two stars with extremely high precision. Our main results are that (i) we confirmed that the two components share very similar chemical compositions, but HD 80606 is marginally more metal-rich than HD 80607, with an average difference of +0.013+/-0.002dex ({sigma}=0.009dex); and (ii) there is no obvious trend between abundance differences and condensation temperature. Assuming that this binary formed from material with the same chemical composition, it is difficult to understand how giant planet formation could produce the present-day photospheric abundances of the elements we measure. We cannot exclude the possibility that HD 80606 might have accreted about 2.5 to 5M_Earth_ material onto its surface, possibly from a planet destabilised by the known highly eccentric giant.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A41
- Title:
- HD 176986 HARPS + HARPS-N data
- Short Name:
- J/A+A/612/A41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a system of two super-Earths orbiting the moderately active K-dwarf HD 176986. This work is part of the RoPES RV program of G- and K-type stars that combines radial velocity from both HARPS and HARPS-N spectrograph to search for short-period terrestrial planets. HD 176986 b and c are super-Earth mass planets with masses of 5.74 and 9.18 Me, with orbital periods of 6.49 and 16.82 days, at a distances of 0.063 and 0.119AU, in orbits that are consistent with circular. The host star is a K2.5 dwarf, and in spite of its modest level of chromospheric activity log(R'hk)=-4.90+/-0.04, shows a complex activity pattern. Along with the discovery of the planets we study the magnetic cycle and rotation of the star. HD 176986 proves to be suitable to test the available techniques of RV analysis and our understanding of stellar activity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/503/1248
- Title:
- HD 13808 HARPS radial velocities
- Short Name:
- J/MNRAS/503/1248
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive analysis of 10 years of HARPS radial velocities of the K2V dwarf star HD13808, which has previously been reported to host two unconfirmed planet candidates. We use the state-of-the-art nested sampling algorithm PolyChord to compare a wide variety of stellar activity models, including simple models exploiting linear correlations between RVs and stellar activity indicators, harmonic models for the activity signals, and a more sophisticated Gaussian process regression model. We show that the use of overly-simplistic stellar activity models that are not well-motivated physically can lead to spurious `detections' of planetary signals that are almost certainly not real. We also reveal some difficulties inherent in parameter and model inference in cases where multiple planetary signals may be present. Our study thus underlines the importance both of exploring a variety of competing models and of understanding the limitations and precision settings of one's sampling algorithm. We also show that at least in the case of HD 13808, we always arrive at consistent conclusions about two particular signals present in the RV, regardless of the stellar activity model we adopt; these two signals correspond to the previously-reported though unconfirmed planet candidate signals. Given the robustness and precision with which we can characterize these two signals, we deem them secure planet detections. In particular, we find two planets orbiting HD13808 at distances of 0.11, 0.26AU with periods of 14.2, 53.8d, and minimum masses of 11, 10 Earth masses.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A103
- Title:
- HD20794 HARPS radial velocities
- Short Name:
- J/A+A/605/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the feasibility of detecting Earth analogs around Sun-like stars using the radial velocity method by investigating one of the largest radial velocities datasets for the one of the most stable radial-velocity stars HD20794. We proceed by disentangling the Keplerian signals from correlated noise and activity-induced variability. We diagnose the noise using the differences between radial velocities measured at different wavelength ranges, so-called "differential radial velocities", as well as the combination of radial velocities measured for other stars to account for instrumental effects. We apply this method to the radial velocities measured by HARPS, and identify four signals at 18, 89, 147 and 330d. The two signals at periods of 18 and 89d are previously reported and are better quantified in this work. The signal at a period of about 147d is reported for the first time, and corresponds to a super-Earth with a minimum mass of 4.59 Earth mass located 0.51AU from HD20794. We also find a significant signal at a period of about 330d corresponding to a super-Earth or Neptune in the habitable zone. Since this signal is close to the annual sampling period and significant periodogram power in some noise proxies are found close to this signal, further observations and analyses are required to confirm it. The analyses of the eccentricity and consistency of signals provide weak evidence for the existence of the previously reported 43d signal and a new signal at a period of about 11.9d with a semi amplitude of 0.4m/s. We find that the detection of a number of signals with radial velocity variations around 0.5m/s likely caused by low mass planet candidates demonstrates the important role of noise modeling in searching for Earth analogs.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A9
- Title:
- HD17674, HD29021, and HD42012 radial velocities
- Short Name:
- J/A+A/601/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new radial velocity measurements for three low-metallicity solar-like stars observed with the SOPHIE spectrograph and its predecessor ELODIE, both installed at the 193cm telescope of the Haute-Provence Observatory, allowing the detection and characterization of three new giant extrasolar planets in intermediate periods of 1.7 to 3.7yr. All three stars, HD 17674, HD 42012 and HD 29021 present single giant planetary companions with minimum masses between 0.9 and 2.5M_Jup_. The range of periods and masses of these companions, along with the distance of their host stars, make them good targets to look for astrometric signals over the lifetime of the new astrometry satellite Gaia. We discuss the preliminary astrometric solutions obtained from the first Gaia data release.
- ID:
- ivo://CDS.VizieR/J/A+A/585/A134
- Title:
- HD1461, HD40307, and HD204313 radial velocities
- Short Name:
- J/A+A/585/A134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of the entire HARPS observations of three stars that host planetary systems: HD1461, HD40307, and HD204313. The data set spans eight years and contains more than 200 nightly averaged velocity measurements for each star. This means that it is sensitive to both long-period and low-mass planets and also to the e ects induced by stellar activity cycles. We modelled the data using Keplerian functions that correspond to planetary candidates and included the short- and long-term effects of magnetic activity. A Bayesian approach was taken both for the data modelling, which allowed us to include information from activity proxies such as log(R'_HK_) in the velocity modelling, and for the model selection, which permitted determining the number of significant signals in the system. The Bayesian model comparison overcomes the limitations inherent to the traditional periodogram analysis. We report an additional super-Earth planet in the HD1461 system. Four out of the six planets previously reported for HD40307 are confirmed and characterised. We discuss the remaining two proposed signals. In particular, we show that when the systematic uncertainty associated with the techniques for estimating model probabilities are taken into account, the current data are not conclusive concerning the existence of the habitable-zone candidate HD40307 g. We also fully characterise the Neptune-mass planet that orbits HD204313 in 34.9 days.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A58
- Title:
- HD20794, HD85512, HD192310 HARPS radial velocities
- Short Name:
- J/A+A/534/A58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In 2009 we started, within the dedicated HARPS-Upgrade GTO program, an intense radial-velocity monitoring of a few nearby, slowly-rotating and quiet solar-type stars. The goal of this campaign is to gather, with high cadence and continuity, very-precise radial-velocity data in order to detect tiny signatures of very-low-mass stars potentially in the habitable zone of their parent stars. 10 stars have been selected among the most stable stars of the original HARPS high-precision program, uniformly spread in hour angle, such that three to four of them are observable at any time of the year. For each star we record 50 data points spread over the observing season. The data point consists of three nightly observations of a total integration time of 10 minutes each and separated by 2 hours. This is an observational strategy adopted to minimize stellar pulsation and granulation noise. In this paper we present the first results of this ambitious program. The radial-velocity data and the orbital parameters of five new and one confirmed low-mass planets around the stars HD 20794, HD 85512 and HD 192310, respectively, are reported and discussed, among which a system of three super-Earths and one harboring a 3.6-Earth-mass planet at the inner edge of the habitable zone. This result already confirms previous indications that low-mass planets seem to be very frequent around solar-type stars and that this occurrence frequency may be higher than 30%.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A6
- Title:
- HD 219134 light and RV curves and code
- Short Name:
- J/A+A/635/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By analysing the transit light-curve of a planet-hosting star or the induced radial velocity oscillations, many useful information on the planet may be retrieved. However, inferring the physical parameters of the planet (mass, size, semi-major axis, etc.) requires the preliminary knowledge of some parameters of the host star, especially its mass and/or radius, that are generally inferred through theoretical evolutionary models. The paper aims at presenting and testing a whole algorithm devoted to the complete characterization of an exoplanetary system thanks to the global analysis of photometric and/or radial velocity time-series combined to observational stellar parameters derived either from spectroscopy or photometry. We developed an integrated tool called MCMCI that combines the Markov Chain Monte Carlo (MCMC) approach for analysing photometric and/or radial velocity time-series with a proper interpolation within stellar evolutionary isochrones and tracks (known as Isochrone placement) to be performed at each chain step, to retrieve stellar theoretical parameters, such as age, mass and radius. We tested the MCMCI both on the HD 219134 multiplanetary system hosting two transiting rocky super-Earths and on WASP-4, that hosts a bloated hot Jupiter. Even considering different input approaches, a final convergence was reached within the code, we found good agreement with the results already stated in the literature and we obtained more precise output parameters, especially concerning planetary masses. The MCMCI tool offers the opportunity of performing an integrated analysis of an exoplanetary system, without splitting it into the preliminary stellar characterization through theoretical models, but rather favouring a close interaction between the light-curve analysis and the isochrones, so that the parameters recovered at each step of the MCMC enter as input of the Isochrone placement.
