Astronomy & Astrophysics最新文献

{"title":"Scale-invariant vacuum guided resolution of the 7Li BBN problem","authors":"V. G. Gueorguiev","doi":"10.1051/0004-6361/202556334","DOIUrl":"https://doi.org/10.1051/0004-6361/202556334","url":null,"abstract":"A possible resolution of the <sup>7<sup/>Li problem within the scenario of the standard model big bang nucleosynthesis (BNN) is presented. The key idea originates from the application of the scale-invariant vacuum (SIV) paradigm to the BBN. However, here we arrive at the conclusion that reparametrization-invariant symmetry scaling (RISS) is the more appropriate framework for the epoch of the BBN and use the SIV only as a guidance framework. The outcome is a <i>χ<i/><sup>2<sup/> < 0.04 fit to the observed primordial abundances of <sup>4<sup/>He, D/H, <sup>3<sup/>He/D, and a fit of <i>χ<i/><sup>2<sup/> ≈ 1 when including <sup>7<sup/>Li/H observations. The results are obtained and compared to the known standard BBN values by utilizing the publicly available PRIMAT code. The resolution of the <sup>7<sup/>Li problem requires a SIV-guided deviation from the local thermal equilibrium during BBN, such that the thermal energy of matter and radiation scale differently with respect to the SIV-conformal factor <i>λ<i/> during the BBN epoch. This may be viewed as conformal symmetry breaking due to cooling of plasma and the properties of matter, which means that the framework may be of relevance to the problem of nuclear fusion as well. The deduced baryon matter content is Ω<sub><i>b<i/><sub/> ≈ 12% for unbroken SIV and Ω<sub><i>b<i/><sub/> ≈ 38% for partially broken SIV, but with <i>λ<i/> < 1 in both cases, which signals preference for RISS over the conventional SIV viewpoint. Applying the RISS paradigm results in <i>λ<i/> > 1 and Ω<sub><i>b<i/><sub/> ≈ 10% with a clear departure of <i>n<i/><sub><i>T<i/><sub/> from the naive SIV suggested value. In all the cases where the <sup>7<sup/>Li problem is resolved, the baryon content is significantly higher than the usually accepted value of Ω<sub><i>b<i/><sub/> ≈ 4.9% within the Lambda cold dark matter (ΛCDM) model.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"70 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145188716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic reconnection sustains the mass budget of the solar wind","authors":"Yajie Chen, Hardi Peter, Damien Przybylski, Haruhisa Iijima, Lakshmi Pradeep Chitta","doi":"10.1051/0004-6361/202556696","DOIUrl":"https://doi.org/10.1051/0004-6361/202556696","url":null,"abstract":"The solar wind originates from open magnetic field regions on the Sun, but the processes relevant to its origin remain unsolved. We present a self-consistent numerical model of the source region of the wind, in which jets similar to those observed on the Sun naturally emerge due to magnetic reconnection between closed and open magnetic fields. In this process, material is transferred from closed to open field lines and fed into the solar wind. We quantified the mass flux through the magnetic field connected to the heliosphere and found that it greatly exceeds the amount required to sustain the wind. This supports a decades-old suspicion based on spectroscopic observations, indicating that magnetic reconnection in the low solar atmosphere could sustain the solar wind.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"70 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145188723","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Discovery of the pre-main-sequence eclipsing binary MML 48","authors":"Y. Gómez Maqueo Chew, L. Hebb, H. C. Stempels, F. M. Walter, D. J. James, G. A. Feiden, R. Petrucci, T. Lister, I. Baraffe, M. Brodheim, F. Faedi, D. R. Anderson, R. A. Street, C. Hellier, K. G. Stassun","doi":"10.1051/0004-6361/202555622","DOIUrl":"https://doi.org/10.1051/0004-6361/202555622","url":null,"abstract":"<i>Aims.<i/> We present the discovery of the eclipsing binary MML 48, which is a member of Upper Centaurus Lupus, has an associated age of 16 Myr, and is composed of two young, low-mass stars.<i>Methods.<i/> We used space- and ground-based observations to characterize the system with both time-series photometry and spectroscopy. Given the extreme mass ratio between the stars, <i>q<i/><sub>EB<sub/> = 0.209 ± 0.014, we modeled a single-lined spectroscopic and eclipsing binary system.<i>Results.<i/> The orbital period, 2.0171068 ± 0.0000004 d, is measured from the highest precision light curves. We derive a primary mass of 1.2 ± 0.07 M<sub>⊙<sub/> using stellar models, and with radial velocities we measured a secondary mass of 0.2509 ± 0.0078 M<sub>⊙<sub/>. The radii are large, as expected for pre-main-sequence stars, and are measured as 1.574 ± 0.026 ± 0.050 R<sub>⊙<sub/> and 0.587 ± 0.0095 ± 0.050 R<sub>⊙<sub/>, for the primary and secondary stars, respectively.<i>Conclusions.<i/> MML 48 joins the short list of known low-mass, pre-main-sequence eclipsing binaries (EBs), being one of only five systems with intermediate ages (15−25 Myr), and the system with the most extreme mass ratio. The primary star is currently at the “fusion bump”, undergoing an over-production of energy in the core due to the build-up of <sup>3<sup/>He before reaching its equilibrium abundance set by the proton-proton (p-p) I chain. MML 48 A is the first young star in an eclipsing system that has been found during its fusion bump. MML 48 is thus an important benchmark for low-mass stellar evolution at a time when the stars are rapidly changing, which allows for a tight constraint on the corresponding isochrone given the uneven mass ratio.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"155 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145182867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Alfvén wave propagation from the photosphere to the corona: Temporal evolution against stationary results","authors":"Roberto Soler","doi":"10.1051/0004-6361/202556264","DOIUrl":"https://doi.org/10.1051/0004-6361/202556264","url":null,"abstract":"Recent observations have confirmed that a significant fraction of the coronal Alfvénic wave spectrum originates in the photosphere. These waves travel from the photosphere to the corona, overcoming the barriers of reflection and dissipation posed by the chromosphere. Previous studies have theoretically calculated the chromospheric reflection, transmission, and absorption coefficients for pure Alfvén waves under the assumption of stationary propagation. Here, we relax that assumption and investigate the time-dependent propagation of Alfvén waves driven at the photosphere. Using an idealized chromospheric background model, we compared the coefficients obtained from time-dependent simulations with those derived under the stationary approximation. Additionally, we examined the impact of the spatial resolution in the numerical simulations. Considering a spatial resolution of 250 m, we find that the time-dependent transmission coefficient converges to the stationary value across the entire frequency range after only a few chromospheric Alfvén crossing times, and the reflectivity convergences well for frequencies below 30 mHz. The absorption coefficient also converges for wave frequencies above 1 mHz, for which chromospheric dissipation is significant. In contrast, at lower frequencies, wave energy dissipation is weak and the time-dependent simulations typically overestimate the absorption. Inadequate spatial resolution artificially increases the chromospheric reflectivity, reduces wave transmission to the corona, and poorly describes the wave energy absorption. Overall, the differences between the stationary and time-dependent approaches are only minor and gradually decrease as spatial resolution and simulation time increase, which reinforces the validity of the stationary approximation.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145182819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Compact groups of galaxies in the TNG100 simulation","authors":"Bruno M. Celiz, José A. Benavides, Mario G. Abadi","doi":"10.1051/0004-6361/202555375","DOIUrl":"https://doi.org/10.1051/0004-6361/202555375","url":null,"abstract":"Using the TNG100 cosmological simulation, we study the formation and evolution of compact groups of galaxies. Over a redshift range of 0 ≲ <i>z<i/> ≲ 0.2, we identify these compact groups as Friends-of-Friends galaxy groups with a high mean surface brightness ( ) and a minimum of four galaxy members. Typically, our compact groups have a median characteristic size of ∼150 kpc, 1D velocity dispersions of 150 km s<sup>−1<sup/>, and stellar masses around 2 × 10<sup>11<sup/> <i>M<i/><sub>⊙<sub/>. Roughly 1% of galaxies that have a stellar mass above 10<sup>9<sup/> <i>M<i/><sub>⊙<sub/> lie in physically dense compact groups. We found that these systems do not constitute a separate category within the broader population of galaxy groups; instead, they represent the lower end of the size distribution in the sequence of galaxy group sizes. We traced their evolution backward in time, revealing that they initially form as galaxy systems with a mean low surface brightness that systematically increases to a peak value before stabilizing over time, exhibiting oscillatory behaviour over the following several gigayears during which mergers may occur. Mergers often transform compact groups with typically four members into galaxy pairs or triplets, which eventually can again increase their number of members by accreting a new galaxy. Nevertheless, the full merging of all constituent galaxies into a single massive galaxy is a rare phenomenon.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"155 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145182829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Photochemical modeling of Ar+ ions in the Martian dayside ionosphere: Implications for ionospheric modeling on Mars","authors":"Long Cheng, Erik Vigren, Robert Lillis, Moa Persson","doi":"10.1051/0004-6361/202555806","DOIUrl":"https://doi.org/10.1051/0004-6361/202555806","url":null,"abstract":"The Martian dayside ionosphere has been widely modeled using photochemical equilibrium calculations. These efforts have mostly focused on dominant ion species in order to make comparisons with orbital observations and on displaying non-negligible model-observation discrepancies. In this study, we investigate Ar<sup>+<sup/>ions in the Martian dayside ionosphere, an ion species with a relatively simple chemistry, and perform both case-by-case orbital comparisons and a statistical comparison over five years of observations by the Neutral Gas and Ion Mass Spectrometer (NGIMS) on the Mars Atmosphere and Volatile Evolution (MAVEN) mission. Statistically, the ratio of modeled to observed Ar<sup>+<sup/>densities increases from ∼1 near 130 km to ∼4 at 220 km, with notable variations as a function of the solar zenith angle. Pressure-dependent discrepancies show a weaker correlation with the solar zenith angle. Model performance improves when incorporating (i) a higher reaction rate coefficient for the charge transfer between Ar<sup>+<sup/>and CO<sub>2<sub/> and/or (ii) reduced solar irradiance. At altitudes above 200 km, Ar<sup>+<sup/>loss via reactions with H<sub>2<sub/> becomes increasingly important. However, we find that model-observation agreement varies between orbits: Some show strong consistency, particularly during Deep Dip campaigns, while others exhibit systematic deviations or significant discrepancies. We suggest that while systematic adjustments to reaction rate coefficients, ionization cross sections, solar irradiance, or background neutral densities may improve model fidelity for certain orbits, capturing the dynamic and time-varying nature of the Martian ionosphere requires further comprehensive investigations.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"3 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145182852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The binary fraction of blue horizontal branch stars","authors":"Yanjun Guo, Kun Chen, Zhenwei Li, Jie Ju, Chao Liu, Xiangxiang Xue, Matti Dorsch, Zhanwen Han, XueFei Chen","doi":"10.1051/0004-6361/202555002","DOIUrl":"https://doi.org/10.1051/0004-6361/202555002","url":null,"abstract":"<i>Context.<i/> Blue horizontal branch (BHB) stars are old, low-mass, metal-poor stars that serve as important tracers of the Galactic halo structure, kinematics, and evolution. Understanding their binary properties provides key insights into their formation channels and the role of binary interactions in the evolution of horizontal branch stars.<i>Aims.<i/> We investigated the intrinsic binary fraction of BHB stars and its dependences on metallicity, kinematics, and effective temperature.<i>Methods.<i/> We collected 299 BHB stars from LAMOST with multiple radial velocity (RV) measurements and classified the sample into halo-like and disk-like BHBs based on their kinematics and metallicity, and into bluer and redder BHBs based on their effective temperature. We then investigated the observed binary fraction for each group based on the radial velocity variations and applied a set of Monte Carlo simulations, assuming distributions of <i>f<i/>(<i>P<i/>)∝<i>P<i/><sup><i>π<i/><sup/> and <i>f<i/>(<i>q<i/>)∝<i>q<i/><sup><i>κ<i/><sup/>, to correct the observed binary fraction for observational biases and to derive the intrinsic binary fraction.<i>Results.<i/> The observed binary fraction of BHB stars is 18%±2% for cases with <i>n<i/> ≥ 2 and 21%±3% for cases with <i>n<i/> ≥ 3, where n represents the number of observation times. After correcting for observational biases, the intrinsic binary fraction increases to 31%±3% for <i>n<i/> ≥ 2 and 32%±3% for <i>n<i/> ≥ 3. A clear contrast is observed between halo-like and disk-like BHB stars, with halo-like BHBs exhibiting a lower intrinsic binary fraction (28%±3% for <i>n<i/> ≥ 2 and 29%±3% for <i>n<i/> ≥ 3) compared to disk-like BHBs (46%±11% and 51%±11%, respectively), indicating different formation pathways. In particular, halo-like BHB stars are more likely to have formed via a single-star evolution channel, whereas disk-like BHB stars may predominantly result from binary evolution processes. Additionally, we find that bluer BHB stars exhibit a significantly higher binary fraction (42%±6% for <i>n<i/> ≥ 2 and 45%±6% for <i>n<i/> ≥ 3) than redder BHB stars (24%±5% and 23%±5%, respectively), which suggests a possible link between binarity and the effective temperature, although more samples are required to confirm this. No correlation is found between <i>π<i/> (<i>κ<i/>) and metallicity or kinematics, nor between <i>π<i/> (<i>κ<i/>) and the effective temperature of BHB stars.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"74 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145182851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tidally induced bar-like galaxies in simulated clusters","authors":"Ewa L. Łokas","doi":"10.1051/0004-6361/202555503","DOIUrl":"https://doi.org/10.1051/0004-6361/202555503","url":null,"abstract":"One of the scenarios for bar formation in galaxies involves their interaction with a more massive companion. The stellar component is then transformed from a disk into a bar-like prolate spheroid. I investigated a subsample of 77 bar-like galaxies tidally induced in the cluster environment, selected among the previously studied sample of bar-like galaxies from the IllustrisTNG simulations. I present six clear, convincing examples of bar-like galaxies formed after an interaction with a progenitor of a massive brightest cluster galaxy (BCG) and describe the properties of their bars. For the whole sample, the time of bar formation is strongly correlated with and typically slightly greater than the time of the pericenter passage. All galaxies are strongly stripped of dark matter and gas, and their rotation is similarly diminished. A larger pericenter distance typically requires a higher host mass in order to transform the galaxy, but the interactions show no preference for prograde configurations. The final strength of the bars does not correlate with the amount of tidal stripping experienced because of the variety of initial properties of the progenitors and the subsequent evolution over the next pericenter passages. In spite of difficulties in the interpretation of some cases involving mergers and multiple interactions, the results confirm in the cosmological context the reality of tidal bar formation in cluster environments previously studied using controlled simulations.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"20 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145182838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ARDENT: A Python package for fast dynamical detection limits with radial velocities","authors":"M. Stalport, M. Cretignier, L. Naponiello, V. Van Grootel","doi":"10.1051/0004-6361/202556044","DOIUrl":"https://doi.org/10.1051/0004-6361/202556044","url":null,"abstract":"The architecture of planetary systems is a key piece of information to our understanding of their formation and evolution. This information also allows us to place the Solar System in the exoplanet context. An important example is the impact of outer giant planets on the formation of inner super-Earths and sub-Neptunes. Radial velocity (RV) surveys aim at drawing statistical insights into the (anti-)correlations between giants and inner small planets, which remain unclear. These surveys are limited by the completeness of the systems, namely, the sensitivity of the data to planet detections. Here, we show that we can improve the completeness by accounting for orbital stability. We introduce the Algorithm for the Refinement of DEtection limits via N-body stability Threshold (ARDENT), an open-source Python package for detection limits that include the stability constraint. The code computes the classic data-driven detection limits, along with the dynamical limits via both analytical and numerical stability criteria. We present the code strategy and illustrate its performance on TOI-1736 using published SOPHIE RVs. This system contains an eccentric cold giant on a 570-day orbit and an inner sub-Neptune on a 7-day orbit. We demonstrate that no additional planet can exist in this system beyond 150 days due to the gravitational influence of the giant. This outcome allows us to significantly refine the system completeness and also carries implications for RV follow-ups. ARDENT is user-friendly and can be employed across a wide variety of systems to refine our understanding of their architecture.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"18 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145182857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New line-driven wind mass-loss rates for OB stars with metallicities down to 0.01 Z⊙","authors":"J. Krtička, J. Kubát, I. Krtičková","doi":"10.1051/0004-6361/202556234","DOIUrl":"https://doi.org/10.1051/0004-6361/202556234","url":null,"abstract":"We provide new line-driven wind models for OB stars with metallicities down to 0.01 <i>Z<i/><sub>⊙<sub/>. The models were calculated with our global wind code METUJE, which solves the hydrodynamical equations from nearly hydrostatic photosphere to supersonically expanding stellar wind together with the equations of statistical equilibrium and the radiative transfer equation. The models predict the basic wind parameters, namely, the wind mass-loss rates and terminal velocities just from the stellar parameters. In general, the wind mass-loss rates decrease with decreasing metallicity and this relationship steepens for very low metallicities, <i>Z<i/> ≲ 0.1 <i>Z<i/><sub>⊙<sub/>. Down to metallicities corresponding to the Magellanic Clouds and even lower, the predicted mass-loss rates reasonably agree with observational estimates. However, the theoretical and observational mass-loss rates for very low metallicities exhibit significant scatter. We show that the scatter of observational values can be caused by inefficient shock cooling in the stellar wind, which leaves a considerable fraction of the wind at too high temperatures with waning observational signatures. The scatter of theoretical predictions is caused by a low number of lines that effectively accelerate the wind at very low metallicities.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"99 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145182831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}