Aims. We present a new upgraded version of ARES. The new version includes a series of interesting new features such as automatic radial velocity correction, a fully automatic continuum determination, ...and an estimation of the errors for the equivalent widths. Methods. The automatic correction of the radial velocity is achieved with a simple cross-correlation function, and the automatic continuum determination, as well as the estimation of the errors, relies on a new approach to evaluating the spectral noise at the continuum level. Results. ARES v2 is totally compatible with its predecessor. We show that the fully automatic continuum determination is consistent with the previous methods applied for this task. It also presents a significant improvement on its performance thanks to the implementation of a parallel computation using the OpenMP library.
Context. The chemical composition of stars that have orbiting planets provides important clues about the frequency, architecture, and composition of exoplanet systems. Aims. We explore the ...possibility that stars from different galactic populations that have different intrinsic abundance ratios may produce planets with a different overall composition. Methods. We compiled abundances for Fe, O, C, Mg, and Si in a large sample of solar neighbourhood stars that belong to different galactic populations. We then used a simple stoichiometric model to predict the expected iron-to-silicate mass fraction and water mass fraction of the planet building blocks, as well as the summed mass percentage of all heavy elements in the disc. Results. Assuming that overall the chemical composition of the planet building blocks will be reflected in the composition of the formed planets, we show that according to our model, discs around stars from different galactic populations, as well as around stars from different regions in the Galaxy, are expected to form rocky planets with significantly different iron-to-silicate mass fractions. The available water mass fraction also changes significantly from one galactic population to another. Conclusions. The results may be used to set constraints for models of planet formation and chemical composition. Furthermore, the results may have impact on our understanding of the frequency of planets in the Galaxy, as well as on the existence of conditions for habitability.
Context.
Ultra-hot Jupiters are excellent laboratories for the study of exoplanetary atmospheres. WASP-121b is one of the most studied; many recent analyses of its atmosphere report interesting ...features at different wavelength ranges.
Aims.
In this paper we analyze one transit of WASP-121b acquired with the high-resolution spectrograph ESPRESSO at VLT in one-telescope mode, and one partial transit taken during the commissioning of the instrument in four-telescope mode.
Methods.
We take advantage of the very high S/N data and of the extreme stability of the spectrograph to investigate the anomalous in-transit radial velocity curve and study the transmission spectrum of the planet. We pay particular attention to the removal of instrumental effects, and stellar and telluric contamination. The transmission spectrum is investigated through single-line absorption and cross-correlation with theoretical model templates.
Results.
By analyzing the in-transit radial velocities we were able to infer the presence of the atmospheric Rossiter–McLaughlin effect. We measured the height of the planetary atmospheric layer that correlates with the stellar mask (mainly Fe) to be 1.052 ± 0.015
R
p
and we also confirmed the blueshift of the planetary atmosphere. By examining the planetary absorption signal on the stellar cross-correlation functions we confirmed the presence of a temporal variation of its blueshift during transit, which could be investigated spectrum-by-spectrum thanks to the quality of our ESPRESSO data. We detected significant absorption in the transmission spectrum for Na, H, K, Li, Ca
II
, and Mg, and we certified their planetary nature by using the 2D tomographic technique. Particularly remarkable is the detection of Li, with a line contrast of ~0.2% detected at the 6
σ
level. With the cross-correlation technique we confirmed the presence of Fe
I
, Fe
II
, Cr
I
, and V
I
. H
α
and Ca
II
are present up to very high altitudes in the atmosphere (~1.44
R
p
and ~2
R
p
, respectively), and also extend beyond the transit-equivalent Roche lobe radius of the planet. These layers of the atmosphere have a large line broadening that is not compatible with being caused by the tidally locked rotation of the planet alone, and could arise from vertical winds or high-altitude jets in the evaporating atmosphere.
Revisiting Proxima with ESPRESSO Suárez Mascareño, A.; Faria, J. P.; Figueira, P. ...
Astronomy and astrophysics (Berlin),
07/2020, Letnik:
639
Journal Article
Recenzirano
Odprti dostop
Context.
The discovery of Proxima b marked one of the most important milestones in exoplanetary science in recent years. Yet the limited precision of the available radial velocity data and the ...difficulty in modelling the stellar activity calls for a confirmation of the Earth-mass planet.
Aims.
We aim to confirm the presence of Proxima b using independent measurements obtained with the new ESPRESSO spectrograph, and refine the planetary parameters taking advantage of its improved precision.
Methods.
We analysed 63 spectroscopic ESPRESSO observations of Proxima (Gl 551) taken during 2019. We obtained radial velocity measurements with a typical radial velocity photon noise of 26 cm s
−1
. We combined these data with archival spectroscopic observations and newly obtained photometric measurements to model the stellar activity signals and disentangle them from planetary signals in the radial velocity (RV) data. We ran a joint Markov chain Monte Carlo analysis on the time series of the RV and full width half maximum of the cross-correlation function to model the planetary and stellar signals present in the data, applying Gaussian process regression to deal with the stellar activity signals.
Results.
We confirm the presence of Proxima b independently in the ESPRESSO data and in the combined ESPRESSO+ HARPS+UVES dataset. The ESPRESSO data on its own shows Proxima b at a period of 11.218 ± 0.029 days, with a minimum mass of 1.29 ± 0.13
M
⊕
. In the combined dataset we measure a period of 11.18427 ± 0.00070 days with a minimum mass of 1.173 ± 0.086
M
⊕
. We get a clear measurement of the stellar rotation period (87 ± 12 d) and its induced RV signal, but no evidence of stellar activity as a potential cause for the 11.2 days signal. We find some evidence for the presence of a second short-period signal, at 5.15 days with a semi-amplitude of only 40 cm s
−1
. If caused by a planetary companion, it would correspond to a minimum mass of 0.29 ± 0.08
M
⊕
. We find that forthe case of Proxima, the full width half maximum of the cross-correlation function can be used as a proxy for the brightness changes and that its gradient with time can be used to successfully detrend the RV data from part of the influence of stellar activity. The activity-induced RV signal in the ESPRESSO data shows a trend in amplitude towards redder wavelengths. Velocities measured using the red end of the spectrograph are less affected by activity, suggesting that the stellar activity is spot dominated. This could be used to create differential RVs that are activity dominated and can be used to disentangle activity-induced and planetary-induced signals. The data collected excludes the presence of extra companions with masses above 0.6
M
⊕
at periods shorter than 50 days.
Context.
Open clusters are recognised as excellent tracers of Galactic thin-disc properties. At variance with intermediate-age and old open clusters, for which a significant number of studies is now ...available, clusters younger than ≲150 Myr have been mostly overlooked in terms of their chemical composition until recently (with few exceptions). On the other hand, previous investigations seem to indicate an anomalous behaviour of young clusters, which includes (but is not limited to) slightly sub-solar iron (Fe) abundances and extreme, unexpectedly high barium (Ba) enhancements.
Aims.
In a series of papers, we plan to expand our understanding of this topic and investigate whether these chemical peculiarities are instead related to abundance analysis techniques.
Methods.
We present a new determination of the atmospheric parameters for 23 dwarf stars observed by the
Gaia
-ESO survey in five young open clusters (
τ
< 150 Myr) and one star-forming region (NGC 2264). We exploit a new method based on titanium (Ti) lines to derive the spectroscopic surface gravity, and most importantly, the microturbulence parameter. A combination of Ti and Fe lines is used to obtain effective temperatures. We also infer the abundances of Fe
I
, Fe
II
, Ti
I
, Ti
II
, Na
I
, Mg
I
, Al
I
, Si
I
, Ca
I
, Cr
I
, and Ni
I
.
Results.
Our findings are in fair agreement with
Gaia
-ESO iDR5 results for effective temperatures and surface gravities, but suggest that for very young stars, the microturbulence parameter is over-estimated when Fe lines are employed. This affects the derived chemical composition and causes the metal content of very young clusters to be under-estimated.
Conclusions.
Our clusters display a metallicity Fe/H between +0.04 ± 0.01 and +0.12 ± 0.02; they are not more metal poor than the Sun. Although based on a relatively small sample size, our explorative study suggests that we may not need to call for ad hoc explanations to reconcile the chemical composition of young open clusters with Galactic chemical evolution models.
Context.
In the last 15 years different ground-based spectroscopic surveys have been started (and completed) with the general aim of delivering stellar parameters and elemental abundances for large ...samples of Galactic stars, complementing
Gaia
astrometry. Among those surveys, the
Gaia
-ESO Public Spectroscopic Survey, the only one performed on a 8m class telescope, was designed to target 100 000 stars using FLAMES on the ESO VLT (both Giraffe and UVES spectrographs), covering all the Milky Way populations, with a special focus on open star clusters.
Aims.
This article provides an overview of the survey implementation (observations, data quality, analysis and its success, data products, and releases), of the open cluster survey, of the science results and potential, and of the survey legacy. A companion article reviews the overall survey motivation, strategy, Giraffe pipeline data reduction, organisation, and workflow.
Methods.
We made use of the information recorded and archived in the observing blocks; during the observing runs; in a number of relevant documents; in the spectra and master catalogue of spectra; in the parameters delivered by the analysis nodes and the working groups; in the final catalogue; and in the science papers. Based on these sources, we critically analyse and discuss the output and products of the Survey, including science highlights. We also determined the average metallicities of the open clusters observed as science targets and of a sample of clusters whose spectra were retrieved from the ESO archive.
Results.
The Gaia-ESO Survey has determined homogeneous good-quality radial velocities and stellar parameters for a large fraction of its more than 110 000 unique target stars. Elemental abundances were derived for up to 31 elements for targets observed with UVES. Lithium abundances are delivered for about 1/3 of the sample. The analysis and homogenisation strategies have proven to be successful; several science topics have been addressed by the
Gaia
-ESO consortium and the community, with many highlight results achieved.
Conclusions.
The final catalogue will be released through the ESO archive in the first half of 2022, including the complete set of advanced data products. In addition to these results, the
Gaia
-ESO Survey will leave a very important legacy, for several aspects and for many years to come.
Thanks to the importance that the star-planet relation has to our understanding of the planet formation process, the precise determination of stellar parameters for the ever increasing number of ...discovered extra-solar planets is of great relevance. Furthermore, precise stellar parameters are needed to fully characterize the planet properties. It is thus important to continue the efforts to determine, in the most uniform way possible, the parameters for stars with planets as new discoveries are announced. In this paper we present new precise atmospheric parameters for a sample of 48 stars with planets. We then take the opportunity to present a new catalogue of stellar parameters for FGK and M stars with planets detected by radial velocity, transit, and astrometry programs. The compiled catalogue is available online. The data can be used for statistical studies of the star-planet correlation, as well as for the derivation of consistent properties for known planets.
Context.
Despite swift progress in the characterisation of exoplanet atmospheres in composition and structure, the study of atmospheric dynamics has not progressed at the same speed. While ...theoretical models have been developed to describe the lower layers of the atmosphere, and independently, the exosphere, little is known about the intermediate layers up to the thermosphere.
Aims.
We aim to provide a clearer picture of atmospheric dynamics for the class of ultra-hot Jupiters, which are highly irradiated gas giants, based on the example of WASP-76 b.
Methods.
We jointly analysed two datasets that were obtained with the HARPS and ESPRESSO spectrographs to interpret the resolved planetary sodium doublet. We then applied the MERC code, which retrieves wind patterns, speeds, and temperature profiles on the line shape of the sodium doublet. An updated version of MERC, with added planetary rotation, also provides the possibility of modelling the latitude dependence of the wind patterns.
Results.
We retrieve the highest Bayesian evidence for an isothermal atmosphere, interpreted as a mean temperature of 3389 ± 227 K, a uniform day- to nightside wind of 5.5
−2.0
+1.4
km s
−1
in the lower atmosphere with a vertical wind in the upper atmosphere of 22.7
−4.1
+4.9
km s
−1
, switching atmospheric wind patterns at 10
−3
bar above the reference surface pressure (10 bar).
Conclusions.
Our results for WASP-76 b are compatible with previous studies of the lower atmospheric dynamics of WASP-76 b and other ultra-hot Jupiters. They highlight the need for vertical winds in the intermediate atmosphere above the layers probed by global circulation model studies to explain the line broadening of the sodium doublet in this planet. This work demonstrates the capability of exploiting the resolved spectral line shapes to observationally constrain possible wind patterns in exoplanet atmospheres. This is an invaluable input to more sophisticated 3D atmospheric models in the future.
ABSTRACT
Stellar parameters of 25 planet-hosting stars and abundances of Li, C, O, Na, Mg, Al, S, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, Zn, Y, Zr, Ba, Ce, Pr, Nd, Sm, and Eu were studied based on ...homogeneous high-resolution spectra and uniform techniques. The iron abundance Fe/H and key elements (Li, C, O, Mg, Si) indicative of the planet formation, as well as the dependences of El/Fe on Tcond, were analysed. The iron abundances determined in our sample stars with detected massive planets range within –0.3 < Fe/H < 0.4. The behaviour of C/Fe, O/Fe, Mg/Fe, and Si/Fe relative to Fe/H is consistent with the Galactic Chemical Evolution trends. The mean values of C/O and C/O are $\langle$C/O$\rangle$ = 0.48 ± 0.07 and $\langle$C/O$\rangle$ = –0.07 ± 0.07, which are slightly lower than solar ones. The Mg/Si ratios range from 0.83 to 0.95 for four stars in our sample and from 1.0 to 1.86 for the remaining 21 stars. Various slopes of El/Fe versus Tcond were found. The dependences of the planetary mass on metallicity, the lithium abundance, the C/O and Mg/Si ratios, and also on the El/Fe–Tcond slopes were considered.
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