Wide binary stars with similar components hosting planets provide a favorable opportunity for exploring the star-planet chemical connection. We perform a detailed characterization of the solar-type stars in the WASP-160 binary system. No planet has been reported yet around WASP-160A while WASP-160B is known to host a transiting Saturn-mass planet, WASP-160B b. For this planet, we also derive updated properties from both literature and new observations. Furthermore, using TESS photometry, we constrain the presence of transiting planets around WASP-160A and additional ones around WASP-160B. The stellar characterization includes, for the first time, the computation of high-precision differential atmospheric and chemical abundances of 25 elements based on high-quality Gemini-GRACES spectra. Our analysis reveals evidence of a correlation between the differential abundances and the condensation temperatures of the elements. In particular, we find both a small but significant deficit of volatiles and an enhancement of refractory elements in WASP-160B relative to WASP-160A. After WASP-94, this is the second stellar pair among the shortlist of planet-hosting binaries showing this kind of peculiar chemical pattern. Although we discuss several plausible planet formation and evolution scenarios for WASP-160A and B that could explain the observed chemical pattern, none of them can be conclusively accepted or rejected. Future high-precision photometric and spectroscopic follow-up, as well as high-contrast imaging observations, of WASP-160A and B, might provide further constraints on the real origin of the detected chemical differences.

Aims. Kepler-278 and Kepler-391 are two of the three evolved stars known to date on the red giant branch (RGB) to host multiple short-period transiting planets. Moreover, the planets orbiting Kepler-278 and Kepler-391 are among the smallest discovered around RGB stars. Here we present a detailed stellar and planetary characterization of these remarkable systems. Methods. Based on high-quality spectra from Gemini-GRACES for Kepler-278 and Kepler-391, we obtained refined stellar parameters and precise chemical abundances for 25 elements. Nine of these elements and the carbon isotopic ratios, 12C∕13C, had not previously been measured. Also, combining our new stellar parameters with a photodynamical analysis of the Kepler light curves, we determined accurate planetary properties of both systems. Results. Our revised stellar parameters agree reasonably well with most of the previous results, although we find that Kepler-278 is ~15% less massive than previously reported. The abundances of C, N, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, and Ce, in both stars, are consistent with those of nearby evolved thin disk stars. Kepler-391 presents a relatively high abundance of lithium (A(Li)NLTE = 1.29 ± 0.09 dex), which is likely a remnant from the main-sequence phase. The precise spectroscopic parameters of Kepler-278 and Kepler-391, along with their high 12C∕13C ratios, show that both stars are just starting their ascent on the RGB. The planets Kepler-278b, Kepler-278c, and Kepler-391c are warm sub-Neptunes, whilst Kepler-391b is a hot sub-Neptune that falls in the hot super-Earth desert and, therefore, it might be undergoing photoevaporation of its outer envelope. The high-precision obtained in the transit times allowed us not only to confirm Kepler-278c’s TTV signal, but also to find evidence of a previously undetected TTV signal for the inner planet Kepler-278b. From the presence of gravitational interaction between these bodies we constrain, for the first time, the mass of Kepler-278b (Mp = 56 −13+37 M⊕) and Kepler-278c (Mp = 35 −21+9.9 M⊕). The mass limits, coupled with our precise determinations of the planetary radii, suggest that their bulk compositions are consistent with a significant amount of water content and the presence of H2 gaseous envelopes. Finally, our photodynamical analysis also shows that the orbits of both planets around Kepler-278 are highly eccentric (e ~ 0.7) and, surprisingly, coplanar. Further observations (e.g., precise radial velocities) of this system are needed to confirm the eccentricity values presented here.

We present a line-by-line differential analysis of a sample of 16 planet-hosting stars and 68 comparison stars using high-resolution, high signal-to-noise ratio spectra gathered using Keck. We obtained accurate stellar parameters and high-precision relative chemical abundances with average uncertainties in T-eff, log g, [Fe/H], and [X/H] of 15 K, 0.034 cm S-2, 0.012 dex, and 0.025 dex, respectively. For each planet host, we identify a set of comparison stars and examine the abundance differences (corrected for Galactic chemical evolution effect) as a function of the dust condensation temperature, T-cond, of the individual elements. While we confirm that the Sun exhibits a negative trend between abundance and T-cond, we also confirm that the remaining planet hosts exhibit a variety of abundance-T-cond trends with no clear dependence upon age, metallicity, or T-eff. The diversity in the chemical compositions of planet-hosting stars relative to their comparison stars could reflect the range of possible planet-induced effects present in these planet hosts, from the sequestration of rocky material (refractory poor) to the possible ingestion of planets (refractory rich). Other possible explanations include differences in the time-scale, efficiency and degree of planet formation, or inhomogeneous chemical evolution. Although we do not find an unambiguous chemical signature of planet formation among our sample, the high-precision chemical abundances of the host stars are essential for constraining the composition and structure of their exoplanets.

ABSTRACT The stellar rotation versus age relation is commonly considered a useful tool to derive reliable ages for Sun-like stars. However, in the light of Kepler data, the presence of apparently old and fast rotators that do not obey the usual gyrochronology relations led to the hypothesis of weakened magnetic breaking in some stars. In this letter, we constrain the solar rotation evolutionary track using solar twins. Predicted rotational periods as a function of mass, age, [Fe/H], and given critical Rossby number (Rocrit) were estimated for the entire rotational sample. Our analysis favours the smooth rotational evolution scenario and suggests that if the magnetic weakened breaking scenario takes place at all, it should arise after Rocrit ≳ 2.29 or ages ≳5.3 Gyr (at 95 per cent confidence level).

We conducted a high-precision elemental abundance analysis of the twin-star comoving pair HIP34407/HIP34426. With mean error of 0.013 dex in the differential abundances (D[X/H]), a significant difference was found: HIP34407 is more metal-rich than HIP34426. The elemental abundance differences correlate strongly with condensation temperature, with the lowest for the volatile elements like carbon around 0.05+/-0.02 dex, and the highest up to about 0.22+/-0.01 dex for the most refractory elements like aluminum. Dissimilar chemical composition for stars in twin-star comoving pairs are not uncommon, thus we compile previously-published results like ours and look for correlations between abundance differences and stellar parameters, finding no significant trends with average effective temperature, surface gravity, iron abundance, or their differences. Instead, we found a weak correlation between the absolute value of abundance difference and the projected distance between the stars in each pair that appears to be more important for elements which have a low absolute abundance. If confirmed, this correlation could be an important observational constraint for binary star system formation scenarios.

We have investigated the thorium (Th) abundance in a sample of 53 thin disc solar twins covering a wide range of ages. These data provide constrains on the mantle energy budget of terrestrial planets that can be formed over the evolution of the Galaxy's thin disc. We have estimated Th abundances with an average precision of 0.025\,dex (in both [Th/H] and [Th/Fe]) through comprehensive spectral synthesis of a Th\,II line present at 4019.1290\,{\AA}, using very high resolution (R\,=\,115,000) high quality HARPS spectra obtained at the ESO La Silla Observatory. We have confirmed that there is a large energy budget from Th decay for maintaining mantle convection inside potential rocky planets around solar twins, from the Galactic thin disc formation until now, because the pristine [Th/H]$_{\rm ZAMS}$ is super-solar on average under a uniform dispersion of 0.056\,dex (varying from +0.037 up to +0.138\,dex based on linear fits against isochrone stellar age). Comparing to neodymium (Nd) and europium (Eu), two others neutron-capture elements, the stellar pristine abundance of Th follows Eu along the Galactic thin disc evolution, but it does not follow Nd, probably because neodymium has a significant contribution from the $s$-process (about 60\,per\,cent).

This work aims to examine in detail the depletion of lithium in solar twins to better constrain stellar evolution models and investigate its possible connection with exoplanets. We employ spectral synthesis in the region of the asymmetric 6707.75 angstrom Li I line for a sample of 77 stars plus the Sun. As in previous works based on a smaller sample of solar twins, we find a strong correlation between Li depletion and stellar age. In addition, for the first time we show that the Sun has the lowest Li abundance in comparison with solar twins at similar age (4.6 +/- 0.5 Gyr). We compare the lithium content with the condensation temperature slope for a subsample of the best solar twins and determine that the most lithium-depleted stars also have fewer refractory elements. We speculate whether the low lithium content in the Sun might be related to the particular configuration of our Solar system.

Context. The benchmark open cluster M67 is known to have solar metallicity and an age similar to that of the Sun. It thus provides us with a great opportunity to study the properties of solar twins, as well as the evolution of Sun-like stars. Aims. Previous spectroscopic studies of M67 reported possible subtle changes in stellar surface abundances throughout the stellar evolutionary phase, namely the effect of atomic diffusion. In this study we attempt to confirm and quantify more precisely the effect of atomic diffusion, and to explore the level of chemical (in)homogeneity in M67. Methods. We presented a strictly line-by-line differential chemical abundance analysis of two groups of stars in M67: three turn-off stars and three subgiants. Stellar atmospheric parameters and elemental abundances were obtained with very high precision using the Keck/HIRES spectra. Results. The subgiants in our sample show negligible abundance variations (<= 0.02 dex), which implies that M67 was born chemically homogeneous. We note that there is a significant abundance difference (similar to 0.1-0.2 dex) between subgiants and turn-off stars, which can be interpreted as the signature of atomic diffusion. Qualitatively stellar models with diffusion agree with the observed abundance results. Some turn-off stars do not follow the general pattern, which suggests that in some cases diffusion can be inhibited, or they might have undergone some sort of mixing event related to planets. Conclusions. Our results pose additional challenges for chemical tagging when using turn-off stars. In particular, the effects of atomic diffusion, which could be as large as 0.1-0.2 dex, must be taken into account in order for chemical tagging to be successfully applied.

Context. It is well known that the magnetic activity of solar-type stars decreases with age, but it is widely debated in the literature whether there is a smooth decline or if there is an early sharp drop until 1-2 Gyr that is followed by a relatively inactive constant phase. Aims. We revisited the activity-age relation using time-series observations of a large sample of solar twins whose precise isochronal ages and other important physical parameters have been determined. Methods. We measured the Can H and K activity indices using approximate to 9000 HARPS spectra of 82 solar twins. In addition, the average solar activity was calculated through asteroids and Moon reflection spectra using the same instrumentation. Thus, we transformed our activity indices into the S Mount Wilson scale (S-MW), recalibrated the Mount Wilson absolute flux and photospheric correction equations as a function of Tell, and then computed an improved bolometric flux normalized activity index log R'(HK) (T-eff) for the entire sample. Results. New relations between activity and the age of solar twins were derived by assessing the chromospheric age-dating limits using log R'(HK) (T-eff). We measured an average solar activity of S-MW = 0.1712 +/- 0.0017 during solar magnetic cycles 23-24 covered by HARPS observations, and we also inferred an average of S-MW = 0.1694 +/- 0.0025 for cycles 10-24, anchored on a sunspot number correlation of S index versus. We also found a simple relation between the average and the dispersion of the activity levels of solar twins. This enabled us to predict the stellar variability effects on the age-activity diagram, and consequently, to estimate the chromospheric age uncertainties that are due to the same phenomena. The age-activity relation is still statistically significant up to ages around 6-7 Gyr, in agreement with previous works using open clusters and field stars with precise ages. Conclusions. Our research confirms that Can H & K lines remain a useful chromospheric evolution tracer until stars reach ages of at least 6-7 Gyr. We found evidence that for the most homogenous set of old stars, the chromospheric activity indices seem to continue to decrease after the solar age toward the end of the main sequence. Our results indicate that a significant part of the scatter observed in the age-activity relation of solar twins can be attributed to stellar cycle modulations effects. The Sun seems to have a normal activity level and variability for its age.

The compositions of stars are a critical diagnostic tool for many topics in astronomy such as the evolution of our Galaxy, the formation of planets, and the uniqueness of the Sun. Previous spectroscopic measurements indicate a large intrinsic variation in the elemental abundance patterns of stars with similar overall metal content. However, systematic errors arising from inaccuracies in stellar models are known to be a limiting factor in such studies, and thus it is uncertain to what extent the observed diversity of stellar abundance patterns is real. Here we report the abundances of 30 elements with precisions of 2% for 79 Sun-like stars within 100 pc. Systematic errors are minimized in this study by focusing on solar twin stars and performing a line-by-line differential analysis using high-resolution, high-signal-to-noise spectra. We resolve [X/Fe] abundance trends in galactic chemical evolution at precisions of 10-3 dex Gyr-1 and reveal that stars with similar ages and metallicities have nearly identical abundance patterns. Contrary to previous results, we find that the ratios of carbon-to-oxygen and magnesium-tosilicon in solar-metallicity stars are homogeneous to within 10% throughout the solar neighborhood, implying that exoplanets may exhibit much less compositional diversity than previously thought. Finally, we demonstrate that the Sun has a subtle deficiency in refractory material relative to > 80% of solar twins ( at 2s confidence), suggesting a possible signpost for planetary systems like our own.

Important insights into the formation and evolution of the Galactic disc(s) are contained in the chemical compositions of stars. We analysed high-resolution and high signal-to-noise HARPS spectra of 79 solar twin stars in order to obtain precise determinations of their atmospheric parameters, ages (sigma similar to 0.4 Gyr) and chemical abundances (sigma < 0.01 dex) of 12 neutron-capture elements (Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd and Dy). This valuable data set allows us to study the [X/Fe]-age relations over a time interval of similar to 10 Gyr and among stars belonging to the thin and thick discs. These relations show that (i) the s-process has been the main channel of nucleosynthesis of n-capture elements during the evolution of the thin disc; (ii) the thick disc is rich in r-process elements which suggests that its formation has been rapid and intensive. In addition, the heavy (Ba, La, Ce) and light (Sr, Y, Zr) s-process elements revealed details on the dependence between the yields of AGB stars and the stellar mass or metallicity. Finally, we confirmed that both [Y/Mg] and [Y/Al] ratios can be employed as stellar clocks, allowing ages of solar twin stars to be estimated with an average precision of similar to 0.5 Gyr.

We address the existence and origin of the lithium (Li) desert, a region in the Li - T_eff plane sparsely populated by stars. Here we analyze some of the explanations that have been suggested for this region, including mixing in the late main sequence, a Li dip origin for stars with low Li abundances in the region, and a possible relation with the presence of planets. To study the Li desert, we measured the atmospheric parameters and Li abundance of 227 late-F dwarfs and subgiants, chosen to be in the T_eff range of the desert and without previous Li abundance measurements. Subsequently, we complemented those with literature data to obtain a homogeneous catalog of 2318 stars, for which we compute masses and ages. We characterize stars surrounding the region of the Li desert. We conclude that stars with low Li abundances below the desert are more massive and more evolved than stars above the desert. Given the unexpected presence of low Li abundance stars in this effective temperature range, we concentrate on finding their origin. We conclude that these stars with low Li abundance do not evolve from stars above the desert: at a given mass, stars with low Li (i.e., below the desert) are more metal-poor. Instead, we suggest that stars below the Li desert are consistent with having evolved from the Li dip, discarding the need to invoke additional mixing to explain this feature. Thus, stars below the Li desert are not peculiar and are only distinguished from other subgiants evolved from the Li dip in that their combination of atmospheric parameters locates them in a range of effective temperatures where otherwise only high Li abundance stars would be found (i.e., stars above the desert).

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 +/- 0.002 dex (sigma = 0.009 dex); 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 5 M-Earth material onto its surface, possibly from a planet destabilised by the known highly eccentric giant.

The six planets of the Kepler-11 system are the archetypal example of a population of surprisingly low-density transiting planets revealed by the Kepler mission. We have determined the fundamental parameters and chemical composition of the Kepler-11 host star to unprecedented precision using an extremely high-quality spectrum from Keck-HIRES (R similar or equal to 67,000, S/N per pixel similar or equal to 260 at 600 nm). Contrary to previously published results, our spectroscopic constraints indicate that Kepler-11 is a young main-sequence solar twin. The revised stellar parameters and new analysis raise the densities of the Kepler-11 planets by between 20% and 95% per planet, making them more typical of the emerging class of "puffy" close-in exoplanets. We obtain photospheric abundances of 22 elements and find that Kepler-11 has an abundance pattern similar to that of the Sun with a slightly higher overall metallicity. We additionally analyze the Kepler light curves using a photodynamical model and discuss the tension between spectroscopic and transit/TTV-based estimates of stellar density.

Using standard 1D-LTE model atmosphere analysis, we provide an in-depth investigation of iron abundance as derived from neutral and singly ionization iron lines (Fe I, II) in nearby star clusters. Specifically, we replicate the discrepancy regarding Delta[Fe/H], wherein the difference of Fe II-Fe I increases for stars of the same cluster with decreasing T-eff, reaching an astonishing 1.0 dex at T-eff similar to 4000 K. Previous studies have investigated this anomaly in the Pleiades and Hyades clusters with no concrete solution. In this analysis, we probe two samples: 63 wide binary field stars where the primary star is of Sun-like temperatures and the secondary is a K-dwarf, ranging from 4231 K <= T-eff <= 6453 K, and 33 Hyades stars of temperatures 4268 K <= T-eff <= 6072 K. Previous studies have found discrepancies on the order of 1.0 dex. However, we find that these studies have neglected line-blending effects of certain Fe II lines, namely lambda = {4508.29 angstrom, 4993.34 angstrom, 5197.58 angstrom, 5325.55 angstrom, 5425.26 angstrom, 6456.38 angstrom}. When these lines are removed from the line-list, we find Delta[Fe/H] decreases to similar to 0.6 dex in the field binaries and similar to 0.3 dex in the Hyades. The reason for this remaining trend is investigated by probing NLTE effects, as well as age and activity considerations using Ca II H+K emission and Li absorption, but these results appear to be small to negligible.

Previous studies on the rotation of Sun-like stars revealed that the rotational rates of young stars converge towards a well-defined evolution that follows a power-law decay. It seems, however, that some binary stars do not obey this relation, often by displaying enhanced rotational rates and activity. In the Solar Twin Planet Search program, we observed several solar twin binaries, and found a multiplicity fraction of 42 per cent similar to 6 per cent in the whole sample; moreover, at least three of these binaries (HIP 19911, HIP 67620 and HIP 103983) clearly exhibit the aforementioned anomalies. We investigated the configuration of the binaries in the program, and discovered new companions for HIP 6407, HIP 54582, HIP 62039 and HIP 30037, of which the latter is orbited by a 0.06 M-circle dot brown dwarf in a 1 m long orbit. We report the orbital parameters of the systems with well-sampled orbits and, in addition, the lower limits of parameters for the companions that only display a curvature in their radial velocities. For the linear trend binaries, we report an estimate of the masses of their companions when their observed separation is available, and a minimum mass otherwise. We conclude that solar twin binaries with low-mass stellar companions at moderate orbital periods do not display signs of a distinct rotational evolution when compared to single stars. We confirm that the three peculiar stars are double-lined binaries, and that their companions are polluting their spectra, which explains the observed anomalies.

We present a high-precision chemical analysis of iota Hor (iota Horologii), a planet-host field star thought to have formed in the Hyades. Elements with atomic number 6 <= Z <= 30 have abundances that are in excellent agreement with those of the cluster within the +/- 0.01 dex (or similar or equal to 2%) precision errors. Heavier elements show a range of abundances such that about half of the Z > 30 species analyzed are consistent with those of the Hyades, while the other half are marginally enhanced by 0.03 +/- 0.01 dex (similar or equal to 7 +/- 2%). The lithium abundance, A(Li), is very low compared to the well-defined A(Li)-T-eff relation of the cluster. For its T-eff, iota Hor's lithium content is about half the Hyades'. Attributing the enhanced lithium depletion to the planet would require a peculiar rotation rate, which we are unable to confirm. Our analysis of iota Hor's chromospheric activity suggests P-rot = 5 days, which is significantly shorter than previously reported. Models of Galactic orbits place iota Hor hundreds of parsecs away from the cluster at formation. Thus, we find the claim of a shared birthplace very difficult to justify.

We report the detection of two new long-period giant planets orbiting the stars HD 95872 and HD 162004 (psi1 Draconis B) by the McDonald Observatory planet search. The planet HD 95872b has a minimum mass of 4.6 M_Jup and an orbital semi-major axis of 5.2 AU. The giant planet psi1 Dra Bb has a minimum mass of 1.5 M_Jup and an orbital semi-major axis of 4.4 AU. Both of these planets qualify as Jupiter analogs. These results are based on over one and a half decades of precise radial velocity measurements collected by our program using the McDonald Observatory Tull Coude spectrograph at the 2.7 m Harlan J. Smith telescope. In the case of psi1 Draconis B we also detect a long-term non-linear trend in our data that indicates the presence of an additional giant planet, similar to the Jupiter-Saturn pair. The primary of the binary star system, psi1 Dra A, exhibits a very large amplitude radial velocity variation due to another stellar companion. We detect this additional member using speckle imaging. We also report two cases - HD 10086 and HD 102870 (beta Virginis) - of significant radial velocity variation consistent with the presence of a planet, but that are probably caused by stellar activity, rather than reflexive Keplerian motion. These two cases stress the importance of monitoring the magnetic activity level of a target star, as long-term activity cycles can mimic the presence of a Jupiter-analog planet.

Context. Studies based on high-precision abundance determinations revealed that chemical patterns of solar twins are characterised by the correlation between the differential abundances relative to the Sun and the condensation temperatures (T-c) of the elements. It has been suggested that the origin of this relation is related to the chemical evolution of the Galactic disk, but other processes, associated with the presence of planets around stars, might also be involved.Aims. We analyse HIRES spectra of 14 solar twins and the Sun to provide new insights on the mechanisms that can determine the relation between [X/H] and T-c.Methods. Our spectroscopic analysis produced stellar parameters (T-eff, log g, [Fe/H], and xi), ages, masses, and abundances of 22 elements (C, O, Na, Mg, Al, Si, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, and Ba). We used these determinations to place new constraints on the chemical evolution of the Galactic disk and to verify whether this process alone can explain the different [X/H]-T-c slopes observed so far.Results. We confirm that the [X/Fe] ratios of all the species correlate with age. The slopes of these relations allow us to describe the effect that the chemical evolution of the Galactic disk has on the chemical patterns of the solar twins. After subtracting the chemical evolution effect, we find that the unevolved [X/H]-T-c slope values do not depend on the stellar ages anymore. However, the wide diversity among these [X/H]-T-c slopes, covering a range of +/- 4 x 10(-5) dex K-1, indicates that processes in addition to the chemical evolution may affect the [X/H]-T-c slopes.Conclusions. The wide range of unevolved [X/H]-T-c slope values spanned at all ages by our sample could reflect the wide diversity among exo-planetary systems observed so far and the variety of fates that the matter in circumstellar disks can experience.