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The long-term solar magnetic activity and its cyclical behaviour, which is maintained by a dynamo mechanism, are both still challenging for the astrophysics. In particular, an atypical event occurred between 1645 and 1715 when the solar activity was remarkably decreased and the number of sunspots got extremely reduced. However, it is still unclear what happened to the solar cycle. The discovery of longer activity minima in cool stars may shed light on the nature of the complex mechanisms involved in the long-term behaviour of the solar-stellar dynamo. Our aim is to explore if the G5V solar-like star HD 4915, which showed a striking chromospheric activity pattern in a previous study performed with HIRES data, could be considered a bona fide Maunder Minimum (hereafter MM) candidate. We have analyzed over 380 spectra acquired between 2003 and 2022 using HARPS and HIRES spectrographs. We carried out a detailed search of activity signatures in HD 4915 by using the Mount Wilson and the Balmer H$_{\alpha}$ activity indexes. This task was performed by means of the GLS periodogram. The new HARPS data show that the chromospheric activity of HD 4915 is not decreasing. In fact, the rise of the activity after the broad minimum in three years gets to the level of activity before that phase, suggesting that it is not entering into a MM phase. HD 4915 shows a distinctive activity behaviour initially attributed to a possible and incipient MM phase. The additional HARPS data allow us to discard a MM in the star. Our analysis shows that the complex activity pattern of HD 4915 could be ruled by a multiple activity cycle, being a shorter cycle of 4.8-yr modulated by a potential longer one. More activity surveys with extensive records and suitable cadence are crucial for accurate identification of stars in Magnetic Grand Minima., Comment: (5 pages, 4 figures)

Over the last decade, studies of large samples of binary systems identified chemical anomalies, and showed that they might be attributed to planet formation or planet engulfment. However, both scenarios have primarily been tested in pairs without known exoplanets. In this work, we explore these scenarios in the newly detected planet-hosting wide binary TOI-1173 A/B (projected separation $\sim 11,400$ AU) using high-resolution MAROON-X and ARCES spectra. We determined photospheric stellar parameters both by fitting stellar models and via the spectroscopic equilibrium approach. Both analyses agree and suggest that they are cool main sequence stars located in the thin disc. A line-by-line differential analysis between the components (B$-$A) displays an abundance pattern in the condensation temperature plane where the planet-hosting star TOI-1173 A is enhanced in refractory elements such as iron by more than 0.05 dex. This suggests the engulfment of $\sim$18 M$_{\oplus}$ of rocky material in star A. Our hypothesis is supported by the dynamics of the system detailed in our companion paper Yana Galarza et al. 2024, which suggest that the Super-Neptune TOI-1173 A $b$ might have been delivered to its current short period ($\sim7$ days) through circulatization and von Zeipel-Lidov-Kozai mechanisms, thereby triggering the engulfment of inner rocky exoplanets., Comment: Accepted for publication in the Astronomical Journal on July 29, 2024

Aims.We conduct a high-precision differential abundance analysis of the remarkable binary system HD 240429/30 (Krios and Kronos, respectively), whose difference in metallicity is one of the highest detected in systems with similar components to date (approximately 0.20 dex). A condensation temperature TC trend study was performed to search for possible chemical signatures of planet formation. In addition, other potential scenarios have been proposed to explain this disparity. Methods. Fundamental atmospheric parameters (Te f f , log g, [Fe/H], vturb) were calculated using the latest version of the FUNDPAR code employing high resolution MAROON-X spectra. We applied a full line-by-line differential technique to measure the abundances of 26 elements in both stars with equivalent widths and spectral synthesis taking advantage of the non-solar scaled opacities. Results.We found a difference in metallicity of approximately 0.230 dex, being Kronos more metal rich than Krios. The analysis encompassed the examination of the diffusion effect and primordial chemical differences, concluding that the observed chemical discrepancies in the binary system cannot be solely attributed to any of these processes. The results also shown a noticeable excess of Li by approximately 0.56 dex in Kronos, and an enhancement of refractories with respect to Krios. A photometric study with TESS data was carried out, without finding any signal of possible transiting planets around the stars. Several potential planet formation scenarios were also explored to account for the observed excess in both metallicity and lithium in Kronos. Planetary engulfment is a plausible explanation, considering the ingestion of an exceptionally large mass, approximately approximately 27.8M_Earth, but no scenario is definitively ruled out., Comment: 11 pages, 6 figures

Aims. We explore different scenarios to explain the chemical difference found in the remarkable giant-giant binary system HD 138202 + CD-30 12303. For the first time, we suggest how to distinguish these scenarios by taking advantage of the extensive convective envelopes of giant stars. Methods. We carried out a high-precision determination of stellar parameters and abundances by applying a full line-by-line differential analysis on GHOST high-resolution spectra. Results. We found a significant chemical difference between the two stars (0.08 dex), which is largely unexpected considering the insensitivity of giant stars to planetary ingestion and diffusion effects. We tested the possibility of engulfment events by using several different combinations of stellar mass, ingested mass, metallicity of the engulfed object and different convective envelopes. However, the planetary ingestion scenario does not seem to explain the observed differences. For the first time, we distinguished the source of chemical differences using a giant-giant binary system. By ruling out other possible scenarios such as planet formation and evolutionary effects between the two stars, we suggest that primordial inhomogeneities might explain the observed differences. This remarkable result implies that the metallicity differences that were observed in at least some main-sequence binary systems might be related to primordial inhomogeneities rather than engulfment events. We also discuss the important implications of finding primordial inhomogeneities, which affect chemical tagging and other fields such as planet formation. We strongly encourage the use of giant-giant pairs. They are a relevant complement to main-sequence pairs for determining the origin of the observed chemical differences in multiple systems. [abridged], Comment: 11 pages, 7 figures, 4 tables. A&A Letters accepted

Am stars are often components of short-period binary systems, where tidal interactions would result in low rotational velocities and help to develop the chemical peculiarities observed. However, the origin of single Am stars and Am stars that belong to wide binary systems is unclear. There is very recent evidence of an Am star hosting a hot-brown dwarf likely synchronized and other possible Am stars hosting hot-Jupiter planets. We wonder if these hot-low mass companions could play a role in the development of an Am star, that is to say, if they could help to mitigate the "single Am" problem. We studied a sample of 19 early-type stars, 7 of them hosting hot-brown dwarfs and 12 of them hosting hot-Jupiter planets. We detected 4 Am stars in our sample (KELT-19A, KELT-17, HATS-70 and TOI-503) and 2 possible Am stars (TOI-681 and HAT-P-69). In particular, we detected the new Am star HATS-70 which hosts a hot-brown dwarf, and rule out this class for the hot-Jupiter host WASP-189, both showing different composition than previously reported. We estimated the incidence of Am stars within stars hosting hot-brown dwarfs (50-75%) and within stars hosting hot-Jupiters (20-42%). The incidence of Am stars hosting hot-brown dwarfs resulted higher than the frequency of Am stars in general. This would imply that the presence of hot-brown dwarfs could play a role in the development of Am stars and possibly help to mitigate the "single Am" problem, different to the case of hot-Jupiter planets. Notably, these results would also indicate that the search for hot-brown dwarfs may be benefited by targeting single Am stars or Am stars in wide binary systems. We encourage the analysis off additional early-type stars hosting hot-companions in order to improve the significance of the initial trends found here. [abridged], Comment: 15 pages, 10 figures, 3 tables (11 tables in the Appendix), A&A accepted

Our aim is to test the accretion scenario of lambda Boo stars. This model predicts that a binary system with two early-type stars passing through a diffuse cloud should both display the same superficial peculiarity. We carried out a detailed abundance determination of three multiple systems hosting a candidate lambda Boo star: the remarkable triple system HD 15164/65/65C and the binary systems HD 193256/281 and HD 198160/161. The abundance analysis of HD 15164/65/65C shows a clear lambda Boo object (HD 15165) and two objects with near solar composition (HD 15164 and 15165C). Notably, the presence of a lambda Boo star (HD 15165) together with a near solar early-type object (HD 15164) is difficult to explain under the accretion scenario. Also, the solar-like composition derived for the late-type star of the system (HD 15165C) could be used, for the first time, as a proxy for the initial composition of the lambda Boo stars. Then, by reviewing abundance analysis of all known binary systems with candidate lambda Boo stars from literature and including the systems analyzed here, we find no binary/multiple system having two clear "bonafide" lambda Boo stars, as expected from the accretion scenario. The closer candidates to show two lambda Boo-like stars are HD 84948, HD 171948 and HD 198160; however, in our opinion they show mild rather than clear lambda Boo patterns. Our results brings little support to the accretion scenario. Then, there is an urgent need of additional binary and multiple systemsto be analyzed through a detailed abundance analysis.[abridged], Comment: A&A accepted, 14 pages, 9 Figures, 9 Tables

Solar twins are key in different areas of astrophysics, however only just over a hundred were identified and well-studied in the last two decades. In this work, we take advantage of the very precise \textit{Gaia} (DR2/EDR3), Tycho and 2MASS photometric systems to create the Inti survey of new solar twins in the Northern Hemisphere. The spectra of our targets were initially obtained with spectrographs of moderate resolution (ARCES and Goodman spectrographs with $R$ = 31500 and 11930, respectively) to find the best solar twin candidates and then observed at McDonald Observatory with higher resolving power (TS23, $R$ = 60000) and signal-to-noise ratio (SNR $\sim$ 300-500). The stellar parameters were estimated through the differential spectroscopic equilibrium relative to the Sun, which allow us to achieve a high internal precision ($\sigma(T_{\rm{eff}})$ = 15 K, $\sigma(\log g)$ = 0.03 dex, $\sigma$([Fe/H]) = 0.01 dex, and $\sigma(v_{t})$ = 0.03 km s$^{-1}$). We propose a new class of stars with evolution similar to the Sun: \textit{solar proxy}, which is useful to perform studies related to the evolution of the Sun, such as its rotational and magnetic evolution. Its definition is based on metallicity ($-$0.15 dex $\leq$ [Fe/H] $\leq$ +0.15 dex) and mass (0.95 M$_{\odot}$ $\leq$ M $\leq$ 1.05 M$_{\odot}$) constraints, thus assuring that the star follows a similar evolutionary path as the Sun along the main sequence. Based on this new definition, we report 70 newly identified solar proxies, 46 solar analogs and 13 solar-type stars. In addition, we identified 9 \textit{close solar twins} whose stellar parameters are the most similar to those of the Sun., Comment: 15 pages and 9 figures

Aims. To explore the chemical pattern of early-type stars with planets, searching for a possible signature of planet formation. In particular, we study a likely relation between the lambda Bootis chemical pattern and the presence of giant planets. Methods. We performed a detailed abundance determination in a sample of early-type stars with and without planets via spectral synthesis. Results. We compared the chemical pattern of the stars in our sample (13 stars with planets and 24 stars without detected planets) with those of lambda Bootis and other chemically peculiar stars. We have found four lambda Bootis stars in our sample, two of which present planets and circumstellar disks (HR 8799 and HD 169142) and one without planets detected (HD 110058). We have also identified the first lambda Bootis star orbited by a brown dwarf (zeta Del). This interesting pair lambda Bootis star + brown dwarf could help to test stellar formation scenarios. We found no unique chemical pattern for the group of early-type stars bearing giant planets. However, our results support, in principle, a suggested scenario in which giant planets orbiting pre-main-sequence stars possibly block the dust of the disk and result in a lambda Bootis-like pattern. On the other hand, we do not find a lambda Bootis pattern in different hot-Jupiter planet host stars, which do not support the idea of possible accretion from the winds of hot-Jupiters, recently proposed in the literature. Then, other mechanisms should account for the presence of the lambda Bootis pattern between main-sequence stars. Finally, we suggest that the formation of planets around lambda Bootis stars such as HR 8799 and HD 169142 is also possible through the core accretion process and not only gravitational instability [abridged], Comment: 21 pages, 12 figures, 4 tables, A&A accepted

Context. It is well known that from 1645 to 1715 solar activity was notably low and the number of sunspots was extremely reduced. This epoch is known as the Maunder Minimum (MM). The study of stars in prolonged activity minima like the MM could help to shed light on this enigmatic epoch. Aims. To explore if the star $\zeta^{2}$ Ret, which belongs to a binary system, is in a state similar to the MM. We have collected more than 430 spectra acquired between 2000 and 2019 with the HARPS, REOSC, UVES, and FEROS spectrographs. Methods. We performed a detailed long-term activity study of both components using the Mount Wilson index, which is obtained from the Ca II H\&K lines. To search for signs of an activity cycle, we analyzed the resulting time-series with the Generalized Lomb-Scargle and CLEAN periodograms. Results. Our spectroscopic analysis shows a high activity level for zet01 Ret and a significant decrease in the magnetic activity cycle amplitude of $\zeta^{2}$ Ret. Thus, the activity difference between both components has been slightly increased ($\Delta$log (RHK) $\sim$0.24 dex), when compared to the previously reported value. The long series analyzed here allowed us to recalculate and constrain the period of $\zeta^{2}$ Ret to $\sim$7.9 yr. We also detected a long-term activity cycle of $\sim$4.2 yr in $\zeta^{1}$ Ret. Conclusions. By analogy with the scenario that proposes a weak solar cycle during the MM, we suggest that activity signatures showed by $\zeta^{2}$ Ret, i.e., a very low activity level when compared to its stellar companion, a notably decreasing amplitude ($\sim$47%), and a cyclic behaviour, are possible evidence that this star could be in a MM state. It is, to our knowledge, the first MM candidate star detected through a highly discrepant activity behaviour in a binary system., Comment: 12 pages and 3 figures

Context. The detection of planets orbiting chemically peculiar stars is very scarcely known in the literature. Aims. To determine the detailed chemical composition of the remarkable planet host star KELT-17. This object hosts a hot-Jupiter planet with 1.31 MJup detected by transits, being one of the more massive and rapidly rotating planet hosts to date. We aimed to derive a complete chemical pattern for this star, in order to compare it with those of chemically peculiar stars. Methods. We carried out a detailed abundance determination in the planet host star KELT-17 via spectral synthesis. Stellar parameters were estimated iteratively by fitting Balmer line profiles and imposing the Fe ionization balance, using the program SYNTHE together with plane-parallel ATLAS12 model atmospheres. Specific opacities for an arbitrary composition and microturbulence velocity vmicro were calculated through the Opacity Sampling (OS) method. The abundances were determined iteratively by fitting synthetic spectra to metallic lines of 16 different chemical species using the program SYNTHE. The complete chemical pattern of KELT-17 was compared to the recently published average pattern of Am stars. We estimated the stellar radius by two methods: a) comparing the synthetic spectral energy distribution with the available photometric data and the Gaia parallax, and b) using a Bayesian estimation of stellar parameters using stellar isochrones. Results. We found overabundances of Ti, Cr, Mn, Fe, Ni, Zn, Sr, Y, Zr, and Ba, together with subsolar values of Ca and Sc. Notably, the chemical pattern agrees with those recently published of Am stars, being then KELT-17 the first exoplanet host whose complete chemical pattern is unambiguously identified with this class. The stellar radius derived by two different methods agrees to each other and with those previously obtained in the literature., Comment: 5 pages, 8 figures, 2 tables, A&A accepted

We explore the probable chemical signature of planet formation in the remarkable binary system HD 106515. The A star hosts a massive long-period planet with 9 MJup detected by radial velocity. We also refine stellar and planetary parameters by using non-solar-scaled opacities when modeling the stars. Methods. We carried out a simultaneous determination of stellar parameters and abundances, by applying for the first time non-solar-scaled opacities in this binary system, in order to reach the highest possible precision. Results. The stars A and B in the binary system HD 106515 do not seem to be depleted in refractory elements, which is different when comparing the Sun with solar-twins. Then, the terrestrial planet formation would have been less efficient in the stars of this binary system. Together with HD 80606/7, this is the second binary system which does not seem to present a (terrestrial) signature of planet formation, and hosting both systems an eccentric giant planet. This is in agreement with numerical simulations, where the early dynamical evolution of eccentric giant planets clear out most of the possible terrestrial planets in the inner zone. We refined the stellar mass, radius and age for both stars and found a notable difference of 78% in R compared to previous works. We also refined the planet mass to mp sini = 9.08 +/- 0.20 MJup, which differs by 6% compared with literature. In addition, we showed that the non-solar-scaled solution is not compatible with the classical solar-scaled method, and some abundance differences are comparable to NLTE or GCE effects specially when using the Sun as reference. Then, we encourage the use of non-solar-scaled opacities in high-precision studies such as the detection of Tc trends.[abridged], Comment: 9 pages, 10 figures, A&A accepted. arXiv admin note: text overlap with arXiv:1507.08125

We implemented non-solar-scaled opacities in a simultaneous derivation of fundamental parameters and abundances. We carried out a high-precision stellar parameters and abundance determination by applying non-solar-scaled opacities and model atmospheres. Our sample is composed by 20 stars including main-sequence and evolved objects. Opacities for an arbitrary composition and vmicro were calculated through the Opacity Sampling method. We obtained a small difference in stellar parameters derived with non-solar-scaled opacities compared to classical solar-scaled models. The differences in Teff, log g and [Fe/H] amount up to 26 K, 0.05 dex and 0.020 dex for the stars in our sample. These differences could be considered as the first estimation of the error due to the use of classical solar-scaled opacities to derive stellar parameters with solar-type and evolved stars. Some chemical species could also show an individual variation higher than those of the [Fe/H] (up to 0.03 dex) and varying from one specie to another, obtaining a chemical pattern difference between both methods. This means that condensation temperature Tc trends could also present a variation. We include an example showing that using non-solar-scaled opacities, the classical solution cannot always verify the excitation and ionization balance conditions required for a model atmosphere. We consider that the use of the non-solar-scaled opacities is not mandatory in every statistical study with large samples of stars. However, for those high-precision works whose results depend on the mutual comparison of different chemical species (such as Tc trends), we consider that it is worthwhile its application. To date, this is probably one of the more precise spectroscopic methods of stellar parameters derivation [abridged]., Comment: 8 pages, 2 tables, 3 figures. A&A accepted

Context. The detection of chromospheric activity cycles in solar-analogue and twin stars, can be used to put in context the solar cycle. However, there is a relatively low percentage of these stars with activity cycles detected. It is well known that the cores of Ca II H&K lines are modulated by stellar activity. The behaviour of Balmer and other optical lines with stellar activity is not yet completely understood. Aims. To search for Ca II H&K, Balmer and Fe II line variations modulated by the stellar activity. In particular, we apply a novel strategy to detect possible shape variations in the H{\alpha} line. Methods. We analyse activity signatures in HD 38858 by using HARPS and CASLEO spectra obtained between 2003 and 2017. We calculate the Mount Wilson index (S$_{MW}$), log($\mathrm{R}'_\mathrm{HK}$) and the statistical moments of Ca II H&K, Balmer and other optical lines. We search for periodicities by using the generalized Lomb-Scargle periodogram. Results. We detect a long-term activity cycle of 10.8 yr in Ca II H&K and H{\alpha}, being HD 38858 one of the most similar stars to the Sun for which a cycle has been detected. In contrast, this cycle is marginally detected in the Fe II lines. Also, we detect a noticeable radial velocity variation, which seems to be produced by stellar activity. Conclusions. HD 38858 is the second solar-analogue star where we find a clear activity cycle which is replicated by Balmer lines. Spectral indexes based on the shape of H{\alpha} seems to be more realiable than the fluxes in the same line to detect activity variations. On the other hand, the cyclic modulation detected gives place to a radial velocity variation, previously associated to a super-Earth planet. Finally, due to the similarity of HD 38858 with the Sun, we recommend to continue monitoring this star., Comment: 9 pages and 14 figures