HARPS spectra with signal-to-noise ratios S/N > 600 at 6000 A were analysed with MARCS model atmospheres to obtain 1D LTE abundances of C, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Sr, and Y for 72 nearby solar-type stars with metallicities in the range -0.3 < [Fe/H] < +0.3 and ASTEC stellar models were used to determine stellar ages from effective temperatures, luminosities obtained via Gaia DR2 parallaxes, and heavy element abundances. The resulting age-metallicity distribution appears to consist of two distinct populations: a sequence of old stars with a steep rise of [Fe/H] to about +0.3 dex at an age of ~7 Gyr and a younger sequence with [Fe/H] increasing from -0.3 dex to about +0.2 dex over the last six Gyr. Furthermore, the trends of several abundance ratios, [O/Fe], [Na/Fe], [Ca/Fe], and [Ni/Fe], as a function of stellar age split into two corresponding sequences. The [Y/Mg]-age relation, on the other hand, shows no offset between the two age sequences and has no significant dependence on [Fe/H], but the components of a visual binary star, zeta Reticuli, have a large and puzzling deviation. The split of the age-metallicity distribution into two sequences may be interpreted as evidence of two episodes of accretion of gas onto the Galactic disk with a quenching of star formation in between. Some of the [X/Fe]-age relations support this scenario but other relations are not so easy to explain, which calls for a deeper study of systematic errors in the derived abundances as a function of [Fe/H], in particular 3D non-LTE effects.
The relative chemical abundances between CI meteorites and the solar photosphere exhibit a significant trend with condensation temperature. A trend with condensation temperature is also seen when the solar photospheric abundances are compared to those of nearby solar twins. We use both these trends to determine the alteration of the elemental abundances of the meteorties and the photosphere by fractionation and calculate a new set of primordial Solar System abundances.
We explore the effect of the magnetic field when using realistic three-dimensional convection experiments to determine solar element abundances. By carrying out magnetoconvection simulations with a radiation-hydro code (the Copenhagen stagger code) and through a-posteriori spectral synthesis of three Fe I lines, we obtain evidence that moderate amounts of mean magnetic flux cause a noticeable change in the derived equivalent widths compared with those for a non-magnetic case. The corresponding Fe abundance correction for a mean flux density of 200 G reaches up to ~0.1 dex in magnitude. These r…
The solar chemical abundances studied in considerable detail because of discrepant values of solar metallicity inferred from different indicators, where in the present work we have used 28 suitable atomic spectral solar nitrogen lines, relying on new equivalent widths measurements for determining the nitrogen abundance. Corresponding to 28 solar neutral nitrogen lines, we derived a solar abundance of nitrogen using the Holweger and Muller solar model and the measured equivalent widths from the literature. Our study reported the solar nitrogen abundance result to be of 8.05 (sigma = 0.09) using…
CONTEXT: In recent years, the solar chemical abundances have been studied in considerable detail because of discrepant values of solar metallicity inferred from different indicators, i.e., on the one hand, the "sub-solar" photospheric abundances resulting from spectroscopic chemical composition analyses with the aid of 3D hydrodynamical models of the solar atmosphere, and, on the other hand, the high metallicity inferred by helioseismology. AIMS: After investigating the solar oxygen abundance using a CO5BOLD 3D hydrodynamical solar model in previous work, we undertake a similar approach studyi…
We discuss the level of agreement of a new generation of standard solar models (SSMs), Barcelona 2016 or B16 for short, with helioseismic and solar neutrino data, confirming that models implementing the AGSS09met surface abundances, based on refined three-dimensional hydrodynamical simulations of the solar atmosphere, do not not reproduce helioseismic constraints. We clarify that this solar abundance problem can be equally solved by a change of the composition and/or of the opacity of the solar plasma, since effects produced by variations of metal abundances are equivalent to those produced by…
This is a study of abundances of the elements He, C, N, O, Ne, Mg, Si, S, Ar, Ca, and Fe in solar energetic particles (SEPs) in the 2 - 15 MeV amu-1 region measured on the Wind spacecraft during 54 large SEP events occurring between November 1994 and June 2012. The origin of most of the temporal and spatial variations in abundances of the heavier elements lies in rigidity-dependent scattering during transport of the particles away from the site of acceleration at shock waves driven out from the Sun by coronal mass ejections (CMEs). Variation in the abundance of Fe is correlated with the Fe spe…
Implications of the recently discovered systematic abundance difference between the Sun and two collections of `solar twins' are discussed. The differences can be understood as an imprint on the abundances of the solar convection zone caused by the lock-up of heavy elements in the planets. Such a scenario also leads naturally to possible solutions of two other abundance peculiarities; 1) the discrepancy between photospheric abundances derived from accurate 3-D models of the solar photosphere and the abundance of heavy elements in the solar interior deduced from helioseismology, and 2) the abun…
The solar abundances have undergone a major downward revision in the last decade, reputedly as a result of employing 3D hydrodynamical simulations to model the inhomogeneous structure of the solar photosphere. The very low oxygen abundance advocated by Asplund et al. (2004), A(O)=8.66, together with the downward revision of the carbon and nitrogen abundances, has created serious problems for solar models to explain the helioseismic measurements. In an effort to contribute to the dispute we have re-derived photospheric abundances of several elements independently of previous analysis. We applie…
We study the solar photospheric abundance of singly ionized neodymium (Nd II) using high resolution spectroscopic data obtained by Fourier transform spectrograph (FTS). Based on the Local Thermodynamical Equilibrium (LTE) assumption, a new value of Nd abundance is derived. We succeed to select of 51 solar Nd II lines with accurate transition probabilities measured experimentally by Den Hartog et al. (2003) and with accurate damping parameters are determined from literature. Relying on atomic data of Opacity Distribution Function (ODF), we construct theoretical photospheric solar model. The mea…
Recent 3D-simulations have shown that the turbulent kinetic flux (TKF) is significant. We discuss the effects of TKF on the size of convection zone and find that the TKF may help to solve the solar abundance problem. The solar abundance problem is that, with new abundances, the solar convection zone depth, sound speed in the radiative interior, the helium abundance and density in the convective envelope are not in agreement with helioseismic inversions. We have done Monte Carlo simulations on solar convective envelope models with different profile of TKF to test the effects. The solar abundanc…
We present new solar models in which we use the latest low abundances and we further include the effects of rotation, magnetic fields and extra-mixing processes. We assume that the extra-element mixing can be treated as a diffusion process, with the diffusion coefficient depending mainly on the solar internal configuration of rotation and magnetic fields. We find that such models can well reproduce the observed solar rotation profile in the radiative region. Furthermore the proposed models can match the seismic constraints better than the standard solar models, also when these include the late…
Solar models using the new lower abundances of Asplund et al. (2005, 2009) or Caffau et al. (2008, 2009) do not agree as well with helioseismic inferences as models that use the higher Grevesse & Noels (1993) or Grevesse & Sauval (1998) abundances. Adopting the new abundances leads to models with sound speed discrepancies of up to 1.4$%$ below the base of the convection zone (compared to discrepancies of less than 0.4$%$ with the old abundances), a convection zone that is too shallow, and a convection zone helium abundance that is too low. Here we review briefly recent attempts to restore agre…
We determine lithium (Li) abundances for solar twins in the M67 open cluster to add valuable information about the correlation between Li depletion and stellar age and, then, better understand stellar structure and evolution. We use high resolution and good signal-to-noise ratio spectra to characterize Li depletion in three solar twins from M67, using spectral synthesis in the region of the asymmetric 6707.75 Å\, Li I feature. The mean Li abundance value of A(Li)$=1.6\pm0.2$ dex for our sample of M67 solar twins (our three stars plus a fourth solar twin from a previous analysis in the literatu…
We present and discuss the strong correspondence between evolution of the emission length scale in the lower transition region and in situ measurements of the fast solar wind composition during this most recent solar minimum. We combine recent analyses demonstrating the variance in the (supergranular) network emission length scale measured by SOHO (and STEREO) with that of the Helium abundance (from WIND) and the degree of Iron fractionation in the solar wind (from the ACE and Ulysses). The net picture developing is one where a decrease in the Helium abundance and the degree of Iron fractionat…
We present three-dimensional (3D) non-local thermodynamic equilibrium (non-LTE) radiative transfer calculations for silicon in the solar photosphere, using an extensive model atom that includes recent, realistic neutral hydrogen collisional cross-sections. We find that photon losses in the SiI lines give rise to slightly negative non-LTE abundance corrections of the order -0.01 dex. We infer a 3D non-LTE based solar silicon abundance of 7.51 dex. With silicon commonly chosen to be the anchor between the photospheric and meteoritic abundances, we find that the meteoritic abundance scale remains…
Lithium and beryllium are destroyed at different temperatures in stellar interiors. As such, their relative abundances offer excellent probes of the nature and extent of mixing processes within and below the convection zone. We determine Be abundances for a sample of eight solar twins for which Li abundances have previously been determined. The analyzed solar twins span a very wide range of age, 0.5-8.2 Gyr, which enables us to study secular evolution of Li and Be depletion. We gathered high-quality UVES/VLT spectra and obtained Be abundances by spectral synthesis of the Be II 313 nm doublet. …
We present a new determination of the solar nitrogen abundance making use of 3D hydrodynamical modelling of the solar photosphere, which is more physically motivated than traditional static 1D models. We selected suitable atomic spectral lines, relying on equivalent width measurements already existing in the literature. For atmospheric modelling we used the co 5 bold 3D radiation hydrodynamics code. We investigated the influence of both deviations from local thermodynamic equilibrium (non-LTE effects) and photospheric inhomogeneities (granulation effects) on the resulting abundance. We also co…
Review of the history of solar system elemental abundances with a new assessment of elemental and isotopic abundances from CI-chondrites and solar data. Solar elemental abundances, or solar system elemental abundances refer to the complement of chemical elements in the entire solar system. The sun contains more than 99-percent of the mass in the solar system and therefore the composition of the sun is a good proxy for the composition of the overall solar system. The solar system composition can be taken as the overall composition of the molecular cloud within the interstellar medium from which…
We review a large body of literature for concentrations of halogens in chondrites and stellar halogen data used for solar system abundances (i.e., representative abundances of the solar system at the time of its formation) and associated analytical problems. Claims of lower solar system chlorine, bromine and iodine abundances from recent analyses of CI-chondrites are untenable because of incompatibility of such low values with nuclear abundance systematics and measurements of halogens in the sun and other stars. We suspect analytical problems associated with these peculiar rock types caused lo…
Zirconium (Zr), together with strontium and yttrium, is an important element in the understanding of the Galactic nucleosynthesis. In fact, the triad Sr-Y-Zr constitutes the first peak of s-process elements. Despite its general relevance not many studies of the solar abundance of Zr were conducted. We derive the zirconium abundance in the solar photosphere with the same CO5BOLD hydrodynamical model of the solar atmosphere that we previously used to investigate the abundances of C-N-O. We review the zirconium lines available in the observed solar spectra and select a sample of lines to determin…
Context. The Sun acts as a cornerstone of stellar physics. Thanks to spectroscopic, helioseismic and neutrino flux observations, we can use the Sun as a laboratory of fundamental physics in extreme conditions. The conclusions we draw are then used to inform and calibrate evolutionary models of all other stars in the Universe. However, solar models are in tension with helioseismic constraints. The debate on the ``solar problem'' has hitherto led to numerous publications discussing potential issues with solar models and abundances. Aims. Using the recently suggested high-metallicity abundances f…
Representative abundances of the chemical elements for use as a solar abundance standard in astronomical and planetary studies are summarized. Updated abundance tables for solar system abundances based on meteorites and photospheric measurements are presented.
We find that element abundances in energetic ions accelerated by shock waves formed at corotating interaction regions (CIRs) mirror the abundances of the solar wind modified by a decreasing power-law dependence on the mass-to-charge ratio A/Q of the ions. This behavior is similar in character to the well-known power-law dependence on A/Q of abundances in large gradual solar energetic particles (SEP). The CIR ions reflect the pattern of A/Q, with Q values of the source plasma temperature or freezing-in temperature of 1.0 - 1.2 MK typical of the fast solar wind in this case. Thus the relative io…
Properties of the Sun's interior can be determined accurately from helioseismological measurements of solar oscillations. These measurements, however, are in conflict with photospheric elemental abundances derived using 3-D hydrodynamic models of the solar atmosphere. This divergence of theory and helioseismology is known as the $"$solar modeling problem$"$. One possible solution is that the photospheric neon abundance, which is deduced indirectly by combining the coronal Ne/O ratio with the photospheric O abundance, is larger than generally accepted. There is some support for this idea from o…
We present the first detailed chemical abundance analysis of the old 8.2 Gyr solar twin, HIP 102152. We derive differential abundances of 21 elements relative to the Sun with precisions as high as 0.004 dex ($\lesssim$1%), using ultra high-resolution (R = 110,000), high S/N UVES spectra obtained on the 8.2-m Very Large Telescope. Our determined metallicity of HIP 102152 is [Fe/H] = -0.013 $\pm$ 0.004. The atmospheric parameters of the star were determined to be 54 K cooler than the Sun, 0.09 dex lower in surface gravity, and a microturbulence identical to our derived solar value. Elemental abu…
We determine the dependence of the initial helium abundance and the present-day helium abundance in the convective envelope of solar models ($\yim$ and $\ysm$ respectively) on the parameters that are used to construct the models. We do so by using reference standard solar models to compute the power-law coefficients of the dependence of $\yim$ and $\ysm$ on the input parameters. We use these dependencies to determine the correlation between $\yim$ and $\ysm$ and use this correlation to eliminate uncertainties in $\yim$ from all solar model input parameters except the microscopic diffusion rate…
The use of hydrodynamical simulations, the selection of atomic data, and the computation of deviations from local thermodynamical equilibrium for the analysis of the solar spectra have implied a downward revision of the solar metallicity. We are in the process of using the latest simulations computed with the CO5BOLD code to reassess the solar chemical composition. We determine the solar photospheric carbon abundance by using a radiation-hydrodynamical CO5BOLD model, and compute the departures from local thermodynamical equilibrium by using the Kiel code. We measure equivalent widths of atomic…
The chemical composition of the Sun is among the most important quantities in astrophysics. Solar abundances are needed for modelling stellar atmospheres, stellar structure and evolution, population synthesis, and galaxies as a whole. The solar abundance problem refers to the conflict of observed data from helioseismology and the predictions made by stellar interior models for the Sun, if these models use the newest solar chemical composition obtained with 3D and NLTE models of radiative transfer. Here we take a close look at the problem from observational and theoretical perspective. We also …
We present solar photospheric abundances for 12 elements from optical and near-infrared spectroscopy. The abundance analysis was conducted employing 3D hydrodynamical (CO5BOLD) as well as standard 1D hydrostatic model atmospheres. We compare our results to others with emphasis on discrepancies and still lingering problems, in particular exemplified by the pivotal abundance of oxygen. We argue that the thermal structure of the lower solar photosphere is very well represented by our 3D model. We obtain an excellent match of the observed center-to-limb variation of the line-blanketed continuum in…
Standard solar models (SSM) constructed in accord with low metal abundances disagree with the seismically inferred results. We constructed rotating solar models with low metal abundances that included enhanced settling and convection overshoot. In one of our rotating models, \textbf{AGSSr2a}, the convection overshoot allowed us to recover the radius of the base of convection zone (CZ) at a level of $1σ$. The rotational mixing almost completely counteracts the enhanced settling for the surface helium abundance, but only partially for the surface heavy-element abundance. At the level of $1σ$, th…
Abundance enhancements, during acceleration and transport in both gradual and impulsive solar energetic particle (SEP) events, vary approximately as power laws in the mass-to-charge ratio [A/Q] of the ions. Since the Q-values depend upon the electron temperature of the source plasma, this has allowed a determination of this temperature from the pattern of element-abundance enhancements and a verification of the expected inverse-time dependence of the power of A/Q for diffusive transport of ions from the SEP events, with scattering mean free paths found to be between 0.2 and 1 AU. SEP events de…
The Oxygen abundance in the solar photosphere, and consequently the solar metallicity itself, is still a controversial issue with far-reaching implications in many areas of Astrophysics. This paper presents a new determination obtained by fitting the forbidden OI line at 6300 A with an observational 3D model. The approach presented here is novel because previous determinations were based either on 1D empirical stratifications or on 3D theoretical models. The resulting best-fit abundances are lg E(O)=8.90 and lg E(Ni)=6.15. Nevertheless, introducing minor tweaks in the model and the procedure, …
In the last decade, the photospheric solar metallicity as determined from spectroscopy experienced a remarkable downward revision. Part of this effect can be attributed to an improvement of atomic data and the inclusion of NLTE computations, but also the use of hydrodynamical model atmospheres seemed to play a role. This "decrease" with time of the metallicity of the solar photosphere increased the disagreement with the results from helioseismology. With a CO5BOLD 3D model of the solar atmosphere, the CIFIST team at the Paris Observatory re-determined the photospheric solar abundances of sever…
We have been analyzing a large sample of solar-like stars with and without planets in order to homogeneously measure their photospheric parameters and Carbon abundances. Our sample contains around 200 stars in the solar neighborhood observed with the ELODIE spectrograph, for which the observational data are publicly available. We performed spectral synthesis of prominent bands of C$_{2}$ and C I lines, aiming to accurately obtain the C abundances. We intend to contribute homogeneous results to studies that compare elemental abundances in stars with and without known planets. New arguments will…
The purpose of this work is to better understand the confidence limits of the photospheric solar oxygen abundance derived from three-dimensional models using the forbidden [OI] line at 6300 Å, including correlations with other parameters involved. We worked with a three-dimensional empirical model and two solar intensity atlases. We employed Bayesian inference as a tool to determine the most probable value for the solar oxygen abundance given the model chosen. We considered a number of error sources, such as uncertainties in the continuum derivation, in the wavelength calibration and in the ab…
We present the result of our investigation on the impact of the low Solar abundance of Asplund and collaborators (2004) on the derived ages for the oldest star clusters based on isochrone fittings. We have constructed new stellar models and corresponding isochrones using this new solar mixture with a proper Solar calibration. We have found that the use of the Asplund et al. (2004) metallicity causes the typical ages for old globular clusters in the Milky Way to be increased roughly by 10\%. Although this may appear small, it has a significant impact on the interpretation for the formation epoc…
We compile spectroscopic abundance data from 84 literature sources for 50 elements across 3058 stars in the solar neighborhood, within 150 pc of the Sun, to produce the Hypatia Catalog. We evaluate the variability of the spread in abundance measurements reported for the same star by different surveys. We also explore the likely association of the star within the Galactic disk, the corresponding observation and abundance determination methods for all catalogs in Hypatia, the influence of specific catalogs on the overall abundance trends, and the effect of normalizing all abundances to the same …
The RESIK instrument on {\em CORONAS-F} spacecraft observed several sulphur X-ray lines in three of its four channels covering the wavelength range 3.8-6.1 Å during solar flares. The fluxes are analyzed to give the sulphur abundance. Data are chosen for when the instrument parameters were optimized. The measured fluxes of the \ion{S}{15} $1s^2-1s4p$ ($w4$) line at 4.089 Å gives $A({\rm S}) = 7.16 \pm 0.17$ (abundances on a logarithmic scale with $A({\rm H}) = 12$) which we consider to be the most reliable. Estimates from other lines range from 7.13 to 7.24. The preferred S abundance estimate i…
The abundance of chlorine is determined from X-ray spectra obtained with the RESIK instrument on {\em CORONAS-F} during solar flares between 2002 and 2003. Using weak lines of He-like Cl, \ion{Cl}{16}, between 4.44 and 4.50 Å, and with temperatures and emission measures from {\em GOES} on an isothermal assumption, we obtained $A({\rm Cl}) = 5.75 \pm 0.26$ on a scale $A({\rm H}) = 12$. The uncertainty reflects an approximately factor 2 scatter in measured line fluxes. Nevertheless our value represents what is probably the best solar determination yet obtained. It is higher by factors of 1.8 and…
The cosmic age is an important physical quantity in cosmology. Based on the radiometric method, a reliable lower limit of the cosmic age is derived to be $15.68\pm 1.95$ Gyr by using the $r$-process abundances inferred for the solar system and observations in metal-poor stars. This value is larger than the latest cosmic age $13.813\pm 0.058$ Gyr from Planck 2013 results, while they still agree with each other within the uncertainties. The uncertainty of $1.95$ Gyr mainly originates from the error on thorium abundance observed in metal-poor star CS 22892-052, so future high-precision abundance …
Carbon, nitrogen, and oxygen are the fourth, sixth, and third most abundant elements in the Sun. Their abundances remain hotly debated due to the so-called solar modelling problem that has persisted for almost $20$ years. We revisit this issue by presenting a homogeneous analysis of $408$ molecular lines across $12$ diagnostic groups, observed in the solar intensity spectrum. Using a realistic 3D radiative-hydrodynamic model solar photosphere and LTE (local thermodynamic equilibrium) line formation, we find $\logε_{C} = 8.47\pm0.02$, $\logε_{N} = 7.89\pm0.04$, and $\logε_{O} = 8.70\pm0.04$. Th…
Coronal elemental abundances are known to deviate from the photospheric values of their parent star, with the degree of deviation depending on the First Ionization Potential (FIP). This study focuses on the coronal composition of stars with super-solar photospheric abundances. We present the coronal abundances of six such stars: 11 LMi, $ι$ Hor, HR 7291, $τ$ Boo, and $α$ Cen A and B. These stars all have high-statistics X-ray spectra, three of which are presented for the first time. The abundances measured in this paper are obtained using the line-resolved spectra of the Reflection Grating Spe…
We revisit in more detail a model for element abundance fractionation in the solar chromosphere, that gives rise to the "FIP Effect" in the solar corona and wind. Elements with first ionization potential below about 10 eV, i.e. those that are predominantly ionized in the chromosphere, are enriched in the corona by a factor 3-4. We model the propagation of Alfven waves through the chromosphere using a non-WKB treatment, and evaluate the ponderomotive force associated with these waves. Under solar conditions, this is generally pointed upwards in the chromosphere, and enhances the abundance of ch…
Northumbria University（诺森比亚大学）；University College London, Mullard Space Science Laboratory（伦敦大学学院穆拉德空间科学实验室）；Donostia International Physics Center（圣塞巴斯蒂安国际物理中心）
We present a new technique for measuring the abundance of europium, a representative r-process element, in solar-metallicity stars. Our algorithm compares LTE synthetic spectra with high-resolution observational spectra using a chi-square-minimization routine. The analysis is fully automated, and therefore allows consistent measurement of blended lines even across very large stellar samples. We compare our results with literature europium abundance measurements and find them to be consistent; we also find our method generates smaller errors.
The open cluster M67 has solar metallicity and an age of about 4Gyr. The turn-off mass is close to the minimum mass for which solar metallicity stars develop a convective core during main sequence evolution as a result of the development of hydrogen burning through the CNO-cycle. The morphology of the color-magnitude-diagram (CMD) of M67 around the turn-off shows a clear hook-like feature, direct sign that stars close to the turn-off have convective cores. VandenBerg et al. investigated the possibility of using the morphology of the M67 turn-off to put constraints on the solar metallicity, par…
We want to determine the lithium abundances of solar twin stars as a function of stellar age to provide constraints for stellar evolutions models and to investigate whether there is a connection between low Li abundance and the occurrence of planets. For a sample of 21 solar twins observed with the HARPS spectrograph at high spectral resolution (R~115.000) and very high signal-to-noise ratio (600 < S/N < 2400), precise lithium abundances were obtained by spectral synthesis of the LiI 6707.8 A line and compared to stellar ages, masses, and metallicities determined from a spectroscopic analysis …
We study the impact of new metallicity measurements, from solar wind data, on the solar model. The "solar modelling problem" refers to the persisting discrepancy between helioseismological observations and predictions of solar models computed implementing state-of-the-art photospheric abundances. We critically reassess the problem, in particular considering the new set of abundances of von Steiger \& Zurbuchen 2016, determined through the \textit{in situ} collection of solar wind samples from polar coronal holes. This new set of abundances indicates a solar metallicity $Z_{\odot} \geq 0.0196 \…
16 Cyg A and B are among the brightest stars observed by Kepler. What makes these stars more interesting is that they are solar analogs. 16 Cyg A and B exhibit solar-like oscillations. In this work we use oscillation frequencies obtained using 2.5 years of Kepler data to determine the current helium abundance of these stars. For this we use the fact that the helium ionization zone leaves a signature on the oscillation frequencies and that this signature can be calibrated to determine the helium abundance of that layer. By calibrating the signature of the helium ionization zone against models o…
We report on the determination of chemical abundances of 38 solar analogues, including 11 objects previously identified as super metal-rich stars. We have measured the equivalent widths for 34 lines of 7 different chemical elements (Mg, Al, Si, Ca, Ti, Fe, and Ni) in high-resolution ($\mathcal{R} \sim 80\,000$) spectroscopic images, obtained at the Observatorio Astrofísico Guillermo Haro (Sonora, Mexico), with the Cananea High-resolution Spectrograph. We derived chemical abundances using ATLAS12 model atmospheres and the Fortran code MOOG. We confirmed the super metallicity status of 6 solar a…
The precision differential abundance (PDA) technique is applied to the mid-F stars Procyon and $θ$ Scl using spectra from the ESO UVESPOP library. We relate PDA patterns to endogenous processes related to condensation or to exogenous processes connected to Galactic chemical evolution (GCE). We employ one-dimensional LTE models, but emphasize the use of weaker lines ($\leq$ 20 mÅ) than are typically used in such studies. We compare our results with PDAs of solar-type stars. Abundances and PDAs are determined for 28 elements: C, N, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,…
We examine the composition of the 0.1 - 1 MeV/n interplanetary heavy ions from H to Fe in corotating interaction regions (CIRs) measured by the SIT (Suprathermal Ion Telescope) instrument. We use observations taken on board the two STEREO spacecraft during the unusually long minimum of Solar Cycle 23 from January 2007 through December 2010. During this period instruments on STEREO observed more than 50 CIR events making it possible to investigate CIR ion abundances during solar minimum conditions with unprecedentedly high statistics. The observations reveal annual variations of relative ion ab…
We present a new determination of the solar fluorine abundance together with abundance measurements of fluorine in two Galactic open clusters. We analyzed a sunspot spectrum, observed by L. Wallace and W. Livingston with the FTS at the McMath/Pierce Solar Telescope situated on Kitt Peak and spectra of four giants in the old cluster M 67 ($\sim$4.5 Gyr) and three giants in the young cluster NGC 6404 ($\sim$0.5 Gyr), obtained with the CRIRES spectrograph at VLT. Fluorine was measured through synthesis of the available HF lines. We adopted the recent set of experimental molecular parameters of HF…
Rotational velocity, lithium abundance, and the mass depth of the outer convective zone are key parameters in the study of the processes at work in the stellar interior, in particular when examining the poorly understood processes operating in the interior of solar-analog stars. We investigate whether the large dispersion in the observed lithium abundances of solar-analog stars can be explained by the depth behavior of the outer convective zone masses, within the framework of the standard convection model based on the local mixing-length theory. We also aims to analyze the link between rotatio…
Helioseismic observations have revealed many properties of the Sun: the depth and the helium abundance of the convection zone, the sound-speed and the density profiles in the solar interior. Those constraints have been used to judge the stellar evolution theory. With the old solar composition (e.g., GS98), the solar standard model is in reasonable agreement with the helioseismic constraints. However, a solar model with revised composition (e.g., AGSS09) with low abundance $Z$ of heavy elements cannot be consistent with those constraints. This is the so-called "solar abundance problem", standin…
