Astronomy & Astrophysics最新文献

{"title":"Luminosity functions and initial mass function variations from large samples of H II regions and molecular clouds","authors":"J. Braine, E. Corbelli","doi":"10.1051/0004-6361/202557853","DOIUrl":"https://doi.org/10.1051/0004-6361/202557853","url":null,"abstract":"Large high-quality samples of HII regions and their parent giant molecular clouds (GMCs) are now available for local galaxies. It is therefore possible to investigate the links between the CO and H<i>α<i/> luminosity functions and whether massive stars form in GMCs of all masses. The CO luminosity functions, representing the distribution of GMC masses, are consistently steeper than the H<i>α<i/> luminosity functions. The CO luminosity function invariably steepens in the outer disk, where fewer massive GMCs are present beyond the median cloud galactocentric distance. The H<i>α<i/> luminosity function also steepens in the outer disk for most of the galaxies examined. Using Salpeter, Kroupa, and Chabrier initial mass functions (IMFs) along with stellar mass-luminosity-radius relations, we calculate the bolometric luminosity and H<i>α<i/> emission from young star clusters. The cluster masses are linked to the GMC mass by assuming that the cluster mass is a constant fraction (3%) of the parent cloud mass. In particular, results for a fully stochastic IMF are compared to suggestions that very massive stars only form in massive clusters or clouds. Within the limits of the observations - no small molecular clouds or low-luminosity HII regions can be detected at the typical ∼10 Mpc distance of the sample galaxies - we find no evidence for a maximum stellar mass that varies with cloud or cluster mass.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"13 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147735888","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":"Measuring Titan’s rapid orbital expansion combining Cassini radio science normal points and astrometry","authors":"Andrea Magnanini, Valery Lainey, Luis Gomez Casajus, Marco Zannoni, Paolo Tortora","doi":"10.1051/0004-6361/202557884","DOIUrl":"https://doi.org/10.1051/0004-6361/202557884","url":null,"abstract":"Recent analyses of Titan’s orbital migration have yielded conflicting results regarding Saturn’s tidal dissipation (<i>Q<i/>) at Titan’s frequency. While some studies reported a low <i>Q<i/> consistent with resonance locking using independent radio science and astrometric datasets, subsequent work combining multiple mission datasets found a significantly higher <i>Q<i/>, disagreeing notably with the earlier radio science findings. This study re-evaluates Titan’s migration by integrating Cassini radio science data, processed as normal points, with over a century of astrometric observations within a unified dynamical model using NOE software. Our combined analysis confirms the previously reported rapid migration rate and low <i>Q<i/>, thus supporting the nonclassical dissipation mechanisms hypothesis.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"147 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147735891","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":"Gas chemistry in the dust-depleted inner regions of protoplanetary disks","authors":"J. Bethlehem, Ch. Rab, I. Kamp, M. Flock, G. Bourdarot, P. Caselli","doi":"10.1051/0004-6361/202558684","DOIUrl":"https://doi.org/10.1051/0004-6361/202558684","url":null,"abstract":"<i>Context<i/>. The molecular composition inside the dust-sublimation zones of protoplanetary disks is mostly unknown, but important to our understanding of terrestrial planet formation. A few molecules have been observed from this region, specifically CO, H<sub>2<sub/>O, OH, and SiO. The small surface area makes observing this region difficult; hence, modeling is required to disentangle the innermost disk from regions further out.<i>Aims<i/>. We aim to model a protoplanetary disk around a Herbig-type star including the dust-depleted inner region (≈0.1–0.3 au), investigate the chemistry of this region, and explain existing and future observations.<i>Methods<i/>. We post-processed the dust and gas distribution of a magnetohydrostatic model with the radiation thermochemical code ProDiMo to study the chemistry and to produce observables.<i>Results<i/>. We find that the dust-free inner disk is a molecularly rich environment where, besides CO, we also find H<sub>2<sub/>, H<sub>2<sub/>O, and SiO. The gas-temperature profile is complex and fluctuates between 700 and 2000 K, which is warm enough to produce CO overtone line emission. Next to the CO overtone lines, we also find strong high J-level fundamental CO lines between 4.3 and 4.6 μm. The elemental enrichment of Si due to dust sublimation leads to two orders of magnitude more SiO abundance. The SiO gas has average temperatures of ≈1000 K, resulting in strong SiO overtone emission in the spectral range between 4 and 4.3 μm.<i>Conclusions<i/>. We predict that the gas density in the dust-depleted inner disk is high enough to allow for H<sub>2<sub/> formation, resulting in a molecularly rich environment. For our representative Herbig model, the dust-depleted inner disk is responsible for at least 90% of the line emission for CO and H<sub>2<sub/>O between 1 and 28 μm. Next to CO overtone lines, SiO overtone lines are expected to be an important tracer of a dust-free inner disk.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"55 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147735889","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 GRAVITY young stellar object survey","authors":"K. Perraut, J. Bouvier, H. Nowacki, A. Sousa, M. Houllé, J.F. Donati, E. Alecian, S. Alencar, M. Audard, J.-P. Berger, Y.-I. Bouarour, E. Bordier, G. Bourdarot, A. Carmona, A. Caratti o Garatti, C. Dougados, M. Flock, R. Garcia-Lopez, K. Grankin, Á. Kóspál, L. Labadie, C. Moutou, J. Sanchez-Bermudez, H. Shang, M. Takami, A. Amorim, W. Brandner, Y. Clénet, R. Davies, R. Dembet, A. Drescher, A. Eckart, F. Eisenhauer, M. Fabricius, H. Feuchtgruber, N. M. Förster-Schreiber, P. Garcia, E. Gendron, R. Genzel, S. Gillessen, T. Henning, L. Jocou, S. Joharle, P. Kervella, L. Kreidberg, S. Lacour, V. Lapeyrère, J.-B. Le Bouquin, D. Lutz, F. Mang, T. Ott, T. Paumard, G. Perrin, S. Rabien, D. C. Ribeiro, M. Sadun Bordoni, D. Santos, J. Shangguan, T. Shimizu, C. Straubmeier, E. Sturm, L. Tacconi, F. Vincent","doi":"10.1051/0004-6361/202558438","DOIUrl":"https://doi.org/10.1051/0004-6361/202558438","url":null,"abstract":"&lt;i&gt;Context&lt;i/&gt;. Protoplanetary disks around young Sun-like stars are the cradles of the vast majority of detected exoplanets. Probing these disks at multiple spatial scales is key to uncovering how planets form. The inner astronomical unit, the star-disk interaction region, is of utmost importance because most detected exoplanets occupy this zone.&lt;i&gt;Aims&lt;i/&gt;. We aim to spatially and spectrally resolve the inner disk and star-disk interaction region of the M0.3 T Tauri star DO Tau by combining two complementary techniques.&lt;i&gt;Methods&lt;i/&gt;. We used high-resolution near-infrared spectra from CFHT/SPIRou to constrain the magnetospheric star-disk interaction process and optical long-baseline interferometry with ESO VLTI/GRAVITY to determine the sizes of the K-band continuum and Br&lt;i&gt;γ&lt;i/&gt; line emitting regions. From the SPIRou spectra, we measured the veiling in the YJHK bands along with the equivalent widths of the HeI &lt;i&gt;λ&lt;i/&gt;1083, &lt;i&gt;Paβ,&lt;i/&gt; and Br&lt;i&gt;γ&lt;i/&gt; emission lines, from which we estimated the mass accretion rate. We were able to monitor the time variability of these quantities thanks to our long-sequence of observations over about 40 days. We fit the GRAVITY visibilities in the continuum and the differential quantities in the line with geometrical models to obtain the orientation and the size of the inner disk as well as the size and the on-sky displacement of the Br&lt;i&gt;γ&lt;i/&gt; emitting region.&lt;i&gt;Results&lt;i/&gt;. We derived a mass accretion rate of ∼10&lt;sup&gt;−8&lt;sup/&gt;−10&lt;sup&gt;−7&lt;sup/&gt; M&lt;sub&gt;⊙&lt;sub/&gt; yr&lt;sup&gt;−1&lt;sup/&gt;, which confirms that this ∼0.5 M&lt;sub&gt;⊙&lt;sub/&gt; star is a strong accretor. The HI and HeI lines exhibit strong variability on a daily timescale, consistent with the burster classification of DO Tau derived from its K2 light curve. We report a periodic modulation of the intensity of the redshifted high-velocity wings of the Br&lt;i&gt;γ&lt;i/&gt; line profile. The modulation occurs at the rotational period of the star (5.128 d), which suggests the existence of corotating magnetospheric funnel flows. We derived an upper limit of 0.35 on the ratio between the magnetospheric truncation radius and the disk corotation radius, indicative of an ordered unstable accretion regime. The size of the Br&lt;i&gt;γ&lt;i/&gt; line emitting region obtained from GRAVITY is quite small (&lt;i&gt;R&lt;sub&gt;Brγ&lt;sub/&gt;&lt;i/&gt; = 0.011 au ∼ 1.3 R&lt;sub&gt;*&lt;sub/&gt;), and it is much smaller than the K-band continuum emitting region (&lt;i&gt;R&lt;sub&gt;K&lt;sub/&gt;&lt;i/&gt; = 0.09 au ∼ 11 R&lt;sub&gt;*&lt;sub/&gt;). Such a compact Br&lt;i&gt;γ&lt;i/&gt; emission region suggests that most of the line flux originates from the magnetospheric accretion region and/or from an inner wind close to the magnetosphere-disk interface. The on-sky displacements of the blue and red Br&lt;i&gt;γ&lt;i/&gt; line velocity channels suggest a rotation pattern of the emitting gas, as they appear to be nearly aligned along the position angle of the disk. The inclination we derived for the inner disk (∼45-55°) differs from that of the outer disk inferred from the ALMA continuum (∼30°). This poin","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"25 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147735893","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":"Data-calibrated point spread function prediction","authors":"Arseniy Kuznetsov, Benoit Neichel, Sylvain Oberti, Thierry Fusco","doi":"10.1051/0004-6361/202557297","DOIUrl":"https://doi.org/10.1051/0004-6361/202557297","url":null,"abstract":"<i>Context<i/>. Precise knowledge of the point spread function (PSF) underpins many data analysis steps in astronomy, from photometry and astrometry to source de-blending and deconvolution. In adaptive optics (AO) observations, however, the PSF is highly variable with wavelength, field position, and observing conditions, making it difficult to model. Traditional PSF reconstruction (PSF-R) requires full AO telemetry and complex infrastructures, limiting its routine use, especially for tomographic systems.<i>Aims<i/>. We present a practical framework for fast, accurate, and data-calibrated PSF modeling that captures the spatial and spectral variability of AO-corrected PSFs without relying on complete AO telemetry.<i>Methods<i/>. Our approach builds on a Fourier-based PSF model inspired by astro-TIPTOP. As inputs, our model uses only a compact set of physically meaningful parameters retrievable from the ESO archive. A lightweight neural network corrects these inputs to achieve the best match with real data. It is trained end to end with the PSF model, allowing it to learn any miscalibrations directly from on-sky data.<i>Results<i/>. The framework achieves high accuracy on on-sky data. On a test set of MUSE-NFM standard stars, it yields median errors of 13.5% in the Strehl ratio and 10.9% in the core full width at half maximum (FWHM). In crowded MUSE-NFM observations of <i>ω<i/> Centauri, the method predicts dozens of off-axis, wavelength-dependent PSFs with a Strehl error of <5% and a FWHM error of 4.6%, enabling source separation without per-star PSF extraction.<i>Conclusions<i/>. Our compact, physics-informed, and data-calibrated model delivers accurate, polychromatic, and field-varying PSFs without relying on full AO telemetry. While demonstrated on MUSE-NFM, the method is still transferable to other AO-assisted instruments.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"246 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147735894","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":"Thermal variability driven by gravity waves in Triton's atmosphere","authors":"Xing Wang, Jun Cui, Zhaoguo He, Hao Gu, Siqi Yi, Xiaoshu Wu","doi":"10.1051/0004-6361/202558830","DOIUrl":"https://doi.org/10.1051/0004-6361/202558830","url":null,"abstract":"<i>Context<i/>. The thermal structure of Triton’s upper atmosphere has been recognized to be primarily influenced by magnetospheric electron precipitation and solar extreme ultraviolet (EUV) radiation. Gravity waves (GWs) may also act as an important mechanism for redistributing thermal energy, although they have not been directly observed in Triton’s atmosphere. Potential sources of GWs include geyser-like plumes near the surface, energetic particle deposition, and solar radiation.<i>Aims<i/>. This study aims to investigate the effects of GWs on the thermal variations in Triton’s upper atmosphere. We investigated the propagation and dissipation of waves with different horizontal wavelengths and phase speeds, and their impacts on the thermospheric temperature structure.<i>Methods<i/>. We used a linear full-wave model, in which a Gaussian source is introduced to represent waves excited by geyser-like plumes near the surface. The model examines wave propagation and dissipation over a broad range of temporal and spatial scales and evaluates the resulting heating and cooling effects on the background atmosphere.<i>Results<i/>. Our simulations indicate that GWs propagate adiabatically in the lower atmosphere, with density and temperature perturbations anti-phased and with horizontal and vertical velocities in phase. Wave dissipation due to molecular viscosity and thermal conduction occurs in the upper atmosphere, resulting in phase shifts between temperature, density, and velocity perturbations. Wave amplitudes increase with horizontal wavelength and phase speed, with peak amplitudes occurring below 200 km for short-wavelength low-phase speed modes and reaching altitudes of up to 300 km for long-wavelength high-phase speed modes. The maximum temperature and density perturbations are below 5% for short-wavelength modes but increase to nearly 10% for waves with longer horizontal wavelengths. Wave-induced heating is dominated by the sensible heat flux, leading to heating in the lower atmosphere and cooling in the upper atmosphere, with rates on the order of 10<sup>−10<sup/> erg cm<sup>−3<sup/> s<sup>−1<sup/> and an associated energy flux of up to 10<sup>−3<sup/> erg cm<sup>−2<sup/> s<sup>−1<sup/>. The associated temperature increase at the exobase ranges from a few kelvins to several tens of kelvins, depending on the horizontal wavelength, and is comparable to heating from solar EUV radiation and magnetospheric particle precipitation.<i>Conclusions<i/>. This study demonstrates that GWs play a critical role in modulating the thermal structure of Triton’s upper atmosphere.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"21 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147735892","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":"Charge-aware machine learning for the infrared spectra of interstellar polycyclic aromatic hydrocarbons","authors":"Jiang He, Xinghong Mai, Zhao Wang","doi":"10.1051/0004-6361/202659248","DOIUrl":"https://doi.org/10.1051/0004-6361/202659248","url":null,"abstract":"<i>Aims<i/>. Polycyclic aromatic hydrocarbons (PAHs) are among the most abundant molecules in the interstellar medium. Their characteristic infrared (IR) emission acts as a sensitive probe of astrophysical environments, yet detailed spectral analyses have been limited by the high computational cost of density functional theory (DFT) calculations. This constraint has hindered a systematic exploration of how spectral features such as the aromatic IR bands depend on a PAH's charge state and molecular structure.<i>Methods<i/>. Our goal is to develop a computationally efficient machine learning model capable of predicting IR spectra for PAHs across charge states, and to critically reassess established interpretations of how ionization influences these spectra.<i>Results<i/>. We developed a neural network framework to predict PAH IR spectra across four charge states, utilizing a dataset of 12599 species. Molecular structures were represented by topological fingerprints, with charge states integrated via learnable embeddings. Additionally, a random forest classifier was implemented to infer charge states directly from spectral data.<i>Conclusions<i/>. The model achieves near-DFT accuracy in predicting IR spectra while offering orders-of-magnitude acceleration in computation. It reliably handles PAHs containing up to 150 carbon atoms, including anions, neutrals, cations, and di-cations. The predictive capability for larger molecules is currently limited by the available training data. The classifier predicts charge states with over 99% accuracy. Our analysis of the DFT-computed spectra shows that anions exhibit strong emission across multiple bands, often matching or exceeding cation intensities, and the 11.2 micrometer band shows a distinct charge dependence.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"9 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147735890","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":"A possible impact lull in the middle of the Eratosthenian period suggested by the Chang’e-5 and 6 missions","authors":"Minggang Xie, Yan Li","doi":"10.1051/0004-6361/202558759","DOIUrl":"https://doi.org/10.1051/0004-6361/202558759","url":null,"abstract":"<i>Context<i/>. It was generally believed that lunar impact flux over the past 3.5 billion years has been almost constant. However, there are still considerable age gaps, causing the evolution of impact flux to remain elusive. Recently, the Chang’e-5 and 6 missions collected samples from the Moon, and the respective ages of the mare basalt units containing the landing sites were dated to be 2.0 and 2.8 billion years ago (Ga).<i>Aims<i/>. With this work, we aim to investigate the constancy of the lunar impact flux.<i>Methods<i/>. We measured the densities of craters in both Chang’e-5 and 6 landing mare basalt units.<i>Results<i/>. We find that the density of craters with diameters ranging from about 200 m to 1 km in the Chang’e-6 unit is almost identical to that of the Chang’e-5 unit. The density similarity suggests an impact lull (relatively few impacts on average) between 2.0 and 2.8 Ga. Consequently, the population of near-Earth objects (NEOs) is not in a quasi-steady state, with this being supported by a spike found at about 2.8-3.4 Ga. The results suggest that large, rare asteroid family-forming events in the main asteroid belt, rather than background main belt asteroids, are the main (>90 ± 2%; 1σ uncertainty) source of subhectometer NEOs. Alternatively, to be compatible with a constant flux, the strength of the Chang’e-5 mare basalt has to be about 30% lower than that of Chang’e-6.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"3 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147726683","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":"Solar System material reaching neighboring star systems","authors":"L. Neslušan, F. Janák, R. Nagy, M. Hajduková","doi":"10.1051/0004-6361/202558649","DOIUrl":"https://doi.org/10.1051/0004-6361/202558649","url":null,"abstract":"<i>Context<i/>. In our Solar System, few macroscopic objects have been observed to be moving in hyperbolic orbits and, thus, they must have originated from interstellar space. Some meteoroids are also suspected to have an interstellar origin. Analogously, some cometary nuclei have left the Solar System and a similar behavior can be expected for a number of meteoroids.<i>Aims<i/>. We investigate whether meteoroids ejected from the Solar System have the capacity to reach neighboring stars in the future. We also study the minimum distances between these stars and real comets that have managed to escape the Sun’s potential.<i>Methods<i/>. The trajectories of hypothetical meteoroid particles and real cometary nuclei were integrated numerically. To estimate the precision of the integration, we simultaneously used two integration algorithms: the Runge-Kutta method and the symplectic integrator known as Leapfrog. We employed the CNS5 catalog of neighboring stars and the CODE catalog of future orbits of comets.<i>Results<i/>. Since the heliocentric speeds of the meteoroids leaving the Solar System are relatively low, only 5 of the 3893 considered stars can be approached by these meteoroids within 10 au. The other stars are too fast and end up escaping from the vicinity of the system before any particle approaches their innermost region. Of the 123 considered comets, 14 are predicted to approach a star within 50 000 au during the next 5 Myr, but none of them will end up closer than 4633 au. Because of the relatively large uncertainty of the determination of input parameters of considered stars, our result unfortunately suffers from a large uncertainty.<i>Conclusions<i/>. Our results indicate that only a very small amount of material from the Solar System can be delivered to the systems of neighboring stars.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"136 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147726709","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":"A deep HST view of the open cluster NGC2158: Binaries, mass functions, and M-dwarf discontinuity","authors":"A. V. Marchuk, F. Muratore, A. P. Milone, M. V. Legnardi, F. D’Antona, G. Cordoni, A. Mastrobuono-Battisti, E. Bortolan, F. Dell’Agli, E. Dondoglio, E. P. Lagioia, A. F. Marino, M. Tailo, C. Ventura, P. Ventura, T. Ziliotto","doi":"10.1051/0004-6361/202558150","DOIUrl":"https://doi.org/10.1051/0004-6361/202558150","url":null,"abstract":"A significant fraction of stars in both the Galactic field and stellar clusters belong to binary systems. Understanding their properties is therefore fundamental for a comprehensive picture of stellar structure, stellar evolution, and cluster dynamics. Despite extensive work on binaries in clusters, key questions remain open, particularly concerning photometric binaries among low-mass stars. While the binary fraction among field stars shows a strong dependence on stellar mass, studies of star clusters have so far suggested an approximately constant fraction across the limited mass range explored. Moreover, the mass function (MF) of very low-mass stars remains poorly constrained in clusters older than a few hundred million years. In this work, we used deep <i>Hubble<i/> Space Telescope imaging of the intermediate-age open cluster NGC 2158 to investigate its binary population and derive the luminosity and MFs down to ∼0.14 <i>M<i/><sub>⊙<sub/>. This dataset enables the first detailed study of binaries in this cluster. We obtained a global binary fraction of 38%, which is consistent with that observed in other open clusters, and detected a clear mass dependence: the fraction decreases from ∼52% at 1.0<i>M<i/><sub>⊙<sub/> to ∼11% at 0.2<i>M<i/><sub>⊙<sub/>. This trend mirrors that seen in the Galactic field, which suggests that binaries in NGC 2158 and field populations share similar properties. The MF of NGC 2158 is best described by three regimes: high-mass stars (<i>α<i/> = −2.49 ± 0.19), low-mass stars (<i>α<i/> = −1.11 ± 0.09), and very low-mass stars (<i>α<i/> = −0.08 ± 0.07). The slope change near 1.0 <i>M<i/><sub>⊙<sub/> agrees with recent open cluster surveys, although we find a deficit of stars at the lowest masses (<i>M<i/> ≲ 0.3 <i>M<i/><sub>⊙<sub/>). Finally, we identify a discontinuity in the main sequence around <i>M<i/> ∼ 0.3 <i>M<i/><sub>⊙<sub/>. We explore the possibility that this feature traces the <sup>3<sup/>He-driven instability predicted by stellar models, analogous to the ‘Jao Gap’ observed in the colour–magnitude diagram of nearby field stars.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"426 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147726711","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}