- 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.
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- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A76
- Title:
- H{alpha}-activity in the SARG binary survey
- Short Name:
- J/A+A/596/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar activity influences radial velocity (RV) measurements and can also mimic the presence of orbiting planets. As part of the search for planets around the components of wide binaries performed with the SARG High Resolution Spectrograph at the TNG, it was discovered that HD 200466A shows strong variation in RV that is well correlated with the activity index based on H{alpha}. We used SARG to study the H{alpha} line variations in each component of the binaries and a few bright stars to test the capability of the H{alpha} index of revealing the rotation period or activity cycle. We also analysed the relations between the average activity level and other physical properties of the stars. We finally tried to reveal signals in the RVs that are due to the activity. At least in some cases the variation in the observed RVs is due to the stellar activity. We confirm that H{alpha} can be used as an activity indicator for solar-type stars and as an age indicator for stars younger than 1.5Gyr.
- ID:
- ivo://CDS.VizieR/J/A+A/515/A26
- Title:
- H and Ks photometry of Trumpler 14
- Short Name:
- J/A+A/515/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present adaptive optics (AO) near-infrared observations of the core of the Tr 14 cluster in the Carina region obtained with the ESO multi-conjugate AO demonstrator, MAD. Our campaign yields AO-corrected observations with an image quality of about 0.2' across the 2" field of view, which is the widest AO mosaic ever obtained. We detected almost 2000 sources spanning a dynamic range of 10 mag. The pre-main sequence (PMS) locus in the colour-magnitude diagram is well reproduced by Palla & Stahler isochrones with an age of 3 to 5x10^5^yr, confirming the very young age of the cluster. We derive a very high (deprojected) central density n_0_~4.5(+/-0.5)x10^4^pc^-3^ and estimate the total mass of the cluster to be about ~4.3^+3.3^_-1.5_x10^3^M_{sun}_, although contamination of the field of view might have a significant impact on the derived mass. We show that the pairing process is largely dominated by chance alignment so that physical pairs are difficult to disentangle from spurious ones based on our single epoch observation. Yet, we identify 150 likely bound pairs, 30% of these with a separation smaller than 0.5" (~1300AU). We further show that at the 2{sigma} level massive stars have more companions than lower-mass stars and that those companions are respectively brighter on average, thus more massive. Finally, we find some hints of mass segregation for stars heavier than about 10M_{sun}_. If confirmed, the observed degree of mass segregation could be explained by dynamical evolution, despite the young age of the cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/636/A74
- Title:
- HARPS radial velocity database
- Short Name:
- J/A+A/636/A74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph is mounted since 2003 at the ESO 3.6m telescope in La Silla and provides state-of-the-art stellar radial velocity (RV) measurements with a precision down to ~1m/s. The spectra are extracted with a dedicated data-reduction software (DRS) and the RVs are computed by cross correlating with a numerical mask. The aim of this study is three-fold: (i) Create an easy access to the public HARPS RV data set. (ii) Apply the new public SpEctrum Radial Velocity AnaLyser (SERVAL) pipeline to the spectra, and produce a more precise RV data set. (iii) Check whether the precision of the RVs can be further improved by correcting for small nightly systematic effects. For each star observed with HARPS, we downloaded the publicly available spectra from the ESO archive, and recomputed the RVs with SERVAL. This was based on fitting each observed spectrum with a high signal-to-noise ratio template created by co-adding all the available spectra of that star. We then computed nightly zero points (NZPs) by averaging the RVs of quiet stars. Analysing the RVs of the most RV-quiet stars, whose RV scatter is <5m/s, we find that SERVAL RVs are on average more precise than DRS RVs by a few percent. Investigating the NZP time series, we find three significant systematic effects, whose magnitude is independent of the software used for the RV derivation: (i) stochastic variations with a magnitude of ~1m/s; (ii) longterm variations, with a magnitude of ~1m/s and a typical timescale of a few weeks; and (iii) 20-30NZPs significantly deviating by few m/s. In addition, we find small (<~1m/s) but significant intra-night drifts in DRS RVs before the 2015 intervention, and in SERVAL RVs after it. We confirm that the fibre exchange in 2015 caused a discontinuous RV jump, which strongly depends on the spectral type of the observed star: from ~14m/s for late F-type stars, to ~-3m/sx for M dwarfs. The combined effect of extracting the RVs with SERVAL and correcting them for the systematics we find is an improved average RV precision: ~5% improvement for spectra taken before the 2015 intervention, and ~15% improvement for spectra taken after it. To demonstrate the quality of the new RV data set, we present an updated orbital solution of the GJ 253 two-planet system. Our NZP-corrected SERVAL RVs can be retrieved from a user-friendly, public database. It provides more than 212000 RVs for about 3000 stars along with many auxiliary information, such as the NZP corrections, various activity indices, and DRS-CCF products.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A119
- Title:
- HARPS RV and stellar activity
- Short Name:
- J/A+A/575/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Planetary companions of a fixed mass induce reflex motions with a larger amplitude around lower-mass stars, which adds to making M dwarfs excellent targets for extra-solar planet searches. The most recent velocimeters with a stability of can detect very low-mass planets out to the habitable zone of these stars. Low-mass small planets are abundant around M dwarfs, and most of the known potentially habitable planets orbit one of these cool stars. Our M-dwarf radial velocity monitoring with HARPS on the ESO 3.6m telescope at La Silla observatory makes a major contribution to this sample. We present here dense radial velocity (RV) time series for three M dwarfs observed over ~five years: GJ 3293 (0.42M_{sun}_), GJ 3341 (0.47M_{sun}_), and GJ 3543 (0.45M_{sun}_). We extracted these RVs through minimum chi^2^ -matching of each spectrum against a stack of all observed spectra for the same star that has a high S/N ratio. We then compared potential orbital signals against several stellar activity indicators to distinguish the Keplerian variations induced by planets from the spurious signals that result from rotational modulation of stellar surface inhomogeneities and from activity cycles.
- ID:
- ivo://CDS.VizieR/J/ApJS/200/15
- Title:
- HARPS-TERRA project. I.
- Short Name:
- J/ApJS/200/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Doppler spectroscopy has uncovered or confirmed all the known planets orbiting nearby stars. Two main techniques are used to obtain precision Doppler measurements at optical wavelengths. The first approach is the gas cell method, which consists of least-squares matching of the spectrum of iodine imprinted on the spectrum of the star. The second method relies on the construction of a stabilized spectrograph externally calibrated in wavelength. The most precise stabilized spectrometer in operation is the High Accuracy Radial velocity Planet Searcher (HARPS), operated by the European Southern Observatory in La Silla Observatory, Chile. The Doppler measurements obtained with HARPS are typically obtained using the cross-correlation function (CCF) technique. This technique consists of multiplying the stellar spectrum by a weighted binary mask and finding the minimum of the product as a function of the Doppler shift. It is known that CCF is suboptimal in exploiting the Doppler information in the stellar spectrum. Here we describe an algorithm to obtain precision radial velocity measurements using least-squares matching of each observed spectrum to a high signal-to-noise ratio template derived from the same observations. This algorithm is implemented in our software HARPS-TERRA (Template-Enhanced Radial velocity Re-analysis Application). New radial velocity measurements on a representative sample of stars observed by HARPS are used to illustrate the benefits of the proposed method. We show that, compared with CCF, template matching provides a significant improvement in accuracy, especially when applied to M dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A109
- Title:
- HARPS XXXI. The M-dwarf sample
- Short Name:
- J/A+A/549/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Searching for planets around stars with different masses helps us to assess the outcome of planetary formation for different initial conditions. The low-mass M dwarfs are also the most frequent stars in our Galaxy and potentially therefore, the most frequent planet hosts. We present observations of 102 southern nearby M dwarfs, using a fraction of our guaranteed time on the ESO/HARPS spectrograph. We observed for 460 h and gathered 1965 precise (~1-3m/s) radial velocities (RVs), spanning the period from Feb. 11, 2003 to Apr. 1, 2009.
- ID:
- ivo://CDS.VizieR/J/A+A/604/L4
- Title:
- HAT-P-4 and TYC 2569-744-1 abundances and spectra
- Short Name:
- J/A+A/604/L4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore condensation temperature Tc trends and the Li content in the binary system HAT-P-4, to study the possible chemical signature of planet formation. The star HAT-P-4 hosts a hot Jupiter planet detected by transits, while its stellar companion does not have any detected planets. We derived the fundamental parameters and abundances using the differential method. HAT-P-4 is found to be about 0.1dex more metal rich than its companion; it is enhanced in refractory elements and presents a higher Lithium content. We propose a scenario of a possible rocky planet engulfment in HAT-P-4, which explains the higher metallicity, the higher Li content, and the negative Tc trend we detected.
- ID:
- ivo://CDS.VizieR/J/AJ/147/128
- Title:
- HAT-P-44, HAT-P-45, and HAT-P-46 follow-up
- Short Name:
- J/AJ/147/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery by the HATNet survey of three new transiting extrasolar planets orbiting moderately bright (V=13.2, 12.8, and 11.9) stars. The planets have orbital periods of 4.3012, 3.1290, and 4.4631 days, masses of 0.35, 0.89, and 0.49M_J_, and radii of 1.24, 1.43, and 1.28R_J_. The stellar hosts have masses of 0.94, 1.26, and 1.28M_{sun}_. Each system shows significant systematic variations in its residual radial velocities, indicating the possible presence of additional components. Based on its Bayesian evidence, the preferred model for HAT-P-44 consists of two planets, including the transiting component, with the outer planet having a period of 872 days, eccentricity of 0.494+/-0.081, and a minimum mass of 4.0M_J_. Due to aliasing we cannot rule out alternative solutions for the outer planet having a period of 220 days or 438 days. For HAT-P-45, at present there is not enough data to justify the additional free parameters included in a multi-planet model; in this case a single-planet solution is preferred, but the required jitter of 22.5+/-6.3m/s is relatively high for a star of this type. For HAT-P-46 the preferred solution includes a second planet having a period of 78 days and a minimum mass of 2.0M_J_, however the preference for this model over a single-planet model is not very strong. While substantial uncertainties remain as to the presence and/or properties of the outer planetary companions in these systems, the inner transiting planets are well characterized with measured properties that are fairly robust against changes in the assumed models for the outer planets. Continued radial velocity monitoring is necessary to fully characterize these three planetary systems, the properties of which may have important implications for understanding the formation of hot Jupiters.