Astronomy & Astrophysics最新文献

{"title":"Diffuse interstellar bands and ultraviolet extinction bump: A Milky Way perspective on distant galaxies","authors":"R. Lallement","doi":"10.1051/0004-6361/202555260","DOIUrl":"https://doi.org/10.1051/0004-6361/202555260","url":null,"abstract":"<i>Context.<i/> The spectral width and the center wavelength of the ultraviolet (UV) absorption bump measured for at least two z ≃ 7 galaxies were found to differ significantly from Milky Way (MW) values. A decrease in the width by ~45% and a positive shift of the center by ~70-80 Å were measured. Within the MW, the bump amplitude and width do vary; however, such a narrow bump has never been observed and no variability of the peak position has been convincingly found. On the other hand, links have recently been detected between both the amplitude and the width of the bump and the strength of several diffuse interstellar absorption bands (DIBs). The links were found to be limited to the so-called σ-type DIBs and their detection to be strongly favored if the data were limited to monocloud-type lines of sight (LOSs), selected according to 3D maps of dust extinction.<i>Aims.<i/> We aim to extend the study of the links between MW DIBs and UV bump parameters to the center wavelength of the bump and to the ratio between the bump amplitude and the underlying continuum, and to compare the characteristics of the MW variations in the bump parameters to values at a high redshift.<i>Methods.<i/> We used published catalogs of cross-matched measurements of DIBs and reddening law parameters. We assigned monocloud flags to all LOSs. We focused on the strong σ-type DIBs at 5780 and 6284 Å, and <i>ζ<i/>-type DIBs at 5797 and 5850 Å, and searched for trends linking the bump parameters to the DIB strength normalized to the reddening.<i>Results.<i/> Similarly to the case of the bump amplitude and width, the center wavelength of the bump is found to react to the abundance of σ-type DIB carriers and to be insensitive to the abundance of the <i>ζ<i/>-type DIB carriers, which dominate in dense and UV-shielded cloud cores. A strong abundance of σ carriers induces a shift of the bump peak position to longer wavelengths and a decrease in its width. The variability range for these two parameters in the MW is about half the difference between average MW values and values in the distant galaxies. In the MW, an increase in the abundance of σ carriers also corresponds to an increase in the bump amplitude and in the ratio between the amplitude and the underlying continuum.<i>Conclusions.<i/> In the case of the MW, these results reinforce the hypothesis of the existence of individual types of hydrocarbon molecules that are simultaneously responsible for DIBs and part of the UV bump. They show that the majority of species responsible for narrow and positively shifted bumps in distant galaxies have a link with (or are) those producing the σ DIBs and the long-wavelength part of the bump in the MW, and that, on the contrary, species producing the short-wavelength part of the bump in the MW are of a different nature and are absent along the paths to the regions of those distant galaxies that contribute most to the UV emission. These results are based on a limited number (≃95) of MW LOSs","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"13 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144622306","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":"Fine-structure excitation of C2O by He: Rate coefficients and astrophysical modeling","authors":"A. Veselinova, F. Lique, C. T. Bop, L. González-Sánchez, P. G. Jambrina","doi":"10.1051/0004-6361/202555202","DOIUrl":"https://doi.org/10.1051/0004-6361/202555202","url":null,"abstract":"<i>Context.<i/> C<sub>2<sub/>O molecules are very good probes of oxygen chemistry in interstellar molecular clouds. The accurate derivation of their abundance requires non-local thermodynamic equilibrium (LTE) modeling of their emission spectra.<i>Aims.<i/> This study aims to provide highly accurate fine-structure resolved excitation rate coefficients of C<sub>2<sub/>O induced by collisions with He, enabling the improvement of the modeling of C<sub>2<sub/>O emission spectra in (cold) molecular clouds.<i>Methods.<i/> A new potential energy surface for the C<sub>2<sub/>O–He system was calculated using the spin-restricted coupled-cluster method together with a complete atomic basis set extrapolation. Quantum scattering calculations were performed using the exact close-coupling approach, explicitly accounting for the fine structure of C<sub>2<sub/>O. Excitation calculations using a radiative transfer model were conducted in order to interpret observations of C<sub>2<sub/>O in TMC-1.<i>Results.<i/> Rate coefficients for transitions up to the rotational state <i>N<i/> = 20 and temperatures up to 70 K were obtained. The analysis of the excitation calculations revealed non-LTE effects of C<sub>2<sub/>O emission lines at typical densities of TMC-1 (<i>n<i/>(H<sub>2<sub/>)∼10<sup>4<sup/> cm<sup>−3<sup/>), reflecting a balance between collisional excitation and radiative relaxation. These effects significantly influence the derived physical conditions. The column density of C<sub>2<sub/>O in TMC-1 was estimated to be <i>N<i/><sub>C<sub>2<sub/>O<sub/> ≈ 9 · 10<sup>11<sup/> cm<sup>−2<sup/>. This refined value, derived using the newly calculated rate coefficients, highlights the limitations of previous LTE-based estimates and underscores the importance of non-LTE modeling.<i>Conclusions.<i/> The new accurate collisional data enable a more confident modeling of C<sub>2<sub/>O excitation in interstellar clouds and improve the interpretation of C<sub>2<sub/>O emission spectra in molecular clouds, highlighting again the necessity of having accurate molecular data in astrochemical studies.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"14 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144622302","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":"Central galaxy alignments","authors":"Facundo Rodriguez, Manuel Merchán, Daniela Galárraga-Espinosa, Agustina V. Marsengo-Colazo, Antonio D. Montero-Dorta, Vicente Izzo Dominguez, Maria Celeste Artale","doi":"10.1051/0004-6361/202554593","DOIUrl":"https://doi.org/10.1051/0004-6361/202554593","url":null,"abstract":"<i>Context.<i/> Observations indicate that central galaxies’ main shape axes are significantly aligned with other galaxies in their group, as well as with the large-scale structure of the Universe. Simulations have corroborated this finding, providing further insights into how the shape of the stellar component aligns with the surrounding dark matter halo. Recent studies have also investigated the evolution of this alignment in bright central galaxies, revealing that the shapes of the dark matter halo and the stellar component can differ. These results suggest that assembly and merger processes have played a crucial role in the evolution of this alignment.<i>Aims.<i/> In this work, we aim to gain a deeper understanding of galaxy alignments by quantifying how this property is related to the mass of the halos hosting central galaxies and to the large-scale environment measured at different scales.<i>Methods.<i/> By studying different angles, we describe how the alignments of central galaxies depend on the masses of the halos they inhabit. We explore how the main axes of central galaxies align across different scales, both in three-dimensional and two-dimensional projections. We examine how halo mass influences these alignments and how they vary in the surrounding large-scale environment. Additionally, we analyse the characteristics of these alignments across different environments within the large-scale structure of the Universe. To conduct this study, we employed TNG300 hydrodynamical simulations and compared our results with spectroscopic data from the Sloan Digital Sky Survey Data Release 18 (SDSS DR18).<i>Results.<i/> Three types of alignment were analysed: between stellar and dark matter components, between satellite galaxies and the central galaxy, and between the central galaxy and its host halo. The results show that the alignment increases with halo mass and varies with the environment (cluster, filament, cluster outskirt, and others). However, after controlling for local density, we found that most of the observed trends disappear, except for a marginal influence of cosmic filaments on some of the considered alignment angles. The SDSS observations confirm a mass dependence similar to the simulations, although observational biases limit the detection of differences between the different environments.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"12 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144622310","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":"Advancing understanding of sunspot penumbra formation with non-linear force-free field extrapolations","authors":"I. Chifu, N. Bello González, J. Jurčák","doi":"10.1051/0004-6361/202554738","DOIUrl":"https://doi.org/10.1051/0004-6361/202554738","url":null,"abstract":"<i>Context.<i/> Although sunspots have been extensively studied, the mechanism behind the formation of penumbrae is still not fully understood.<i>Aims.<i/> In this work, we investigate the process of sunspot penumbrae formation from a novel approach based on the analysis of magnetic fields from non-linear force-free field (NLFFF) extrapolations aiming to identifying the key parameters driving this process.<i>Methods.<i/> We calculate NLFFF extrapolations from HMI/SDO data sampling the development of the active region NOAA 12757 before, during, and after penumbra formation. We analyse the resulting magnetic field inclination, magnetic field tension, and the current density evolution in the leading spot. The analysis focuses on the stable part of the sunspot, away from the AR opposite polarity.<i>Results.<i/> The analysis of the extrapolations has revealed that: (1) the magnetic field inclination measured at the footpoints of the extrapolated field lines agrees with the results inferred from inversions, confirming the consistency of the methodology. (2) Penumbra formation is preceded by the continuous emergence of magnetic flux as outlined by serpentine fields observed in the low layers. After emerging, these fields further rise shaping the active region field topology formed by high-lying loops. (3) The emergence of local patches of new flux is characterised by high magnetic tension and significant current densities, primarily concentrated at the protospot boundary. Both the magnetic tension and current densities gradually dissipate as the magnetic loops continue to rise. This flux emergence occurs in regions where the penumbra is not yet formed and the magnetic canopy is not yet developed. (4) With the increase of emerged flux, a magnetic canopy develops and gradually expands around the spot in unison with the forming underlying penumbra. (5) As the penumbra and canopy expand, the surrounding network field, initially present close to the spot boundary, gradually migrates outward, reaching a maximum distance of about 9 Mm. This and the rise of serpentine fields, footpointed by migrating moving magnetic features provide evidence of the connectivity between the sunspot’s core magnetic field and the surrounding network field.<i>Conclusions.<i/> This case study provides clear evidence that the formation of stable penumbra results from a bottom-up approach: the continuous emergence and upward rise of serpentine field lines into the corona during which a sunspot magnetic canopy develops.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"2 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144622309","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":"Observation of the Crab Nebula with the Single-Mirror Small-Size Telescope stereoscopic system at low altitude","authors":"C. Alispach, A. Araudo, M. Balbo, V. Beshley, J. Blažek, J. Borkowski, S. Boula, T. Bulik, F. Cadoux, S. Casanova, A. Christov, J. Chudoba, L. Chytka, P. Čechvala, P. Dědic, D. della Volpe, Y. Favre, M. Garczarczyk, L. Gibaud, T. Gieras, E. Glowacki, P. Hamal, M. Heller, M. Hrabovský, P. Janeček, M. Jelínek, V. Jílek, J. Juryšek, V. Karas, B. Lacave, E. Lyard, E. Mach, D. Mandát, W. Marek, S. Michal, J. Michałowski, M. Miroń, R. Moderski, T. Montaruli, A. Muraczewski, S. R. Muthyala, A. L. Müller, A. Nagai, K. Nalewajski, D. Neise, J. Niemiec, M. Nikołajuk, V. Novotný, M. Ostrowski, M. Palatka, M. Pech, M. Prouza, P. Schovanek, V. Sliusar, Ł. Stawarz, R. Sternberger, M. Stodulska, J. Świerblewski, P. Świerk, J. Štrobl, T. Tavernier, P. Trávníček, I. Troyano Pujadas, J. Vícha, R. Walter, K. Ziętara","doi":"10.1051/0004-6361/202555292","DOIUrl":"https://doi.org/10.1051/0004-6361/202555292","url":null,"abstract":"The Single-Mirror Small-Size Telescope (SST-1M) stereoscopic system is composed of two Imaging Atmospheric Cherenkov Telescopes (IACTs) designed to deliver optimal performance for gamma-ray astronomy in the multi-TeV energy range. It features a 4-m diameter tessellated mirror dish and an innovative SiPM-based camera. Its optical system features a 4-m diameter spherical mirror dish based on the Davies-Cotton design, maintaining a good image quality over a large field of view (FoV), while minimizing optical aberrations. In 2022, two SST-1M telescopes were installed at the Ondřejov Observatory, Czech Republic at an altitude of 510 meters above sea level, collecting data for commissioning and astronomical observations since then. We present the first SST-1M observations of the Crab Nebula, conducted between September 2023 and March 2024 in both mono and stereoscopic modes. During this observation period, 46 hours for the SST-1M-1 and 52 hours for the SST-1M-2 were collected (of which 33 hours were in stereoscopic mode). In this work, we used the Crab Nebula observation to validate the expected performance of the instrument, as evaluated by Monte Carlo (MC) simulations that were carefully tuned to account for instrumental and atmospheric effects. We determined that the energy threshold at the analysis level for the zenith angles below 30° is 1 TeV for mono mode and 1.3 TeV for stereo mode. The energy and angular resolutions were approximately 20% and 0.18° for mono mode and 10% and 0.10° for stereo mode, respectively. We present an off-axis performance assessment of the instrument and a detailed study of the systematic uncertainties. The full simulation results for the telescope and its camera are compared to the data for the first time, enabling a deeper understanding of the SST-1M array performance.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"282 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144622332","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":"Rings and arcs around evolved stars","authors":"B. Montoro-Molina, M. A. Guerrero, G. Ramos-Larios, S. Cazzoli, J. A. Toalá, E. Santamaría","doi":"10.1051/0004-6361/202555063","DOIUrl":"https://doi.org/10.1051/0004-6361/202555063","url":null,"abstract":"<i>Context<i/>. A fraction of planetary nebulae (PNe) presents ring-like features in their halos and outermost envelopes. These are thought to be the relic of the last mass loss gaps at the end of the asymptotic giant branch (AGB) phase, providing information on cyclic mass-loss modulations associated either with stellar pulsations or binary interactions.<i>Aims<i/>. We aim at characterizing the spatial and physical properties of the ring-like features around IC 418, the iconic Spirograph Nebula.<i>Methods<i/>. Deep Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) integral field spectroscopic observations and sharp Hubble Space Telescope (HST) images have been investigated to search for the faintest arc-like features and to characterize their physical properties.<i>Results<i/>. Up to 10 concentric arc-like features are detected, with a notable change in the inter-ring gap, which is smaller for the innermost rings. This is interpreted as evidence of the interaction of the expanding nebula with the arc-like features, which otherwise would expand slower. The nebula proper motion also affects the shape and gap between arc-like features.<i>Conclusions<i/>. The extinction radial profile decreases outward, indicating the presence of dust. Otherwise the electronic temperature (<i>T<i/><sub>e<sub/>) and density (<i>n<i/><sub>e<sub/>) derived both from emission line radial profiles and integrated spectra extracted show values around 10 000 K and 8000 cm<sup>−3<sup/>, respectively. Collectively these results indicate distinct differences between the inner nebula, which is denser and more extincted, and the ring-like structures.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"151 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144622305","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":"Interstellar chemistry of CN radicals on ices: The formation of CH3CN and CH3NC and potential connection to acetamide","authors":"J. Enrique-Romero, T. Lamberts","doi":"10.1051/0004-6361/202555360","DOIUrl":"https://doi.org/10.1051/0004-6361/202555360","url":null,"abstract":"<i>Context<i/>. Among the most significant chemical functional groups of interstellar molecules are the class of nitriles, which are suggested to be key prebiotic molecules due to their chemical connection to the peptide bond after hydrolysis. The <sup>•<sup/>CN radicals, the simplest representative of this group, have been shown to exhibit strong interactions with interstellar water ices, potentially impacting their reactivity with other radicals nearby.<i>Aims<i/>. This study explores (a) whether CN and <sup>•<sup/>CH<sub>3<sub/> radicals can readily react to form methyl cyanide (CH<sub>3<sub/>CN) and its isomer methyl isocyanide (CH<sub>3<sub/>NC) and (b) the feasibility of the reaction (CN···H<sub>2<sub/>O)<sub>hemi<sub/> → <sup>•<sup/>C(OH) = NH and its potential role in the formation of acetamide.<i>Methods<i/>. Following a benchmark, we employed density functional theory to map the potential energy surfaces of these chemical processes, focusing on their reactivity on water and carbon monoxide ices.<i>Results<i/>. The results show that CN reacts with <sup>•<sup/>CH<sub>3<sub/> radicals on water ices, efficiently forming CH<sub>3<sub/>CN and CH<sub>3<sub/>NC. However, these reactions are driven by diffusion of <sup>•<sup/>CH<sub>3<sub/> towards the reactive site and subsequently compete with back-diffusion of <sup>•<sup/>CH<sub>3<sub/> from that site. The formation of the radical intermediate <sup>•<sup/>C(OH) = NH on water ice requires quantum tunnelling, and assuming that acetimidic acid forms via CH<sub>3<sub/> + <sup>•<sup/>C(OH) = NH → CH<sub>3<sub/>C(OH) = NH, it can also only isomerise into acetamide through a sizeable barrier thanks to quantum tunnelling. Both quantum tunnelling-driven reactions are highly dependent on the local structure of the water ice. Finally, radical coupling reactions on carbon monoxide ices are found to be barrierless for all cases, and again both the cyanide and the isocyanide are formed.<i>Conclusions<i/>. This work reinforces the conclusion that <sup>•<sup/>CN radicals on interstellar grain surfaces are highly reactive and unlikely to persist unaltered.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"38 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144622329","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":"Impact of the Tayler magnetic instability on the surface abundance of boron in massive stars","authors":"L. Asatiani, P. Eggenberger, M. Marchand, F. D. Moyano, G. Meynet, A. Choplin","doi":"10.1051/0004-6361/202555163","DOIUrl":"https://doi.org/10.1051/0004-6361/202555163","url":null,"abstract":"<i>Context.<i/> The surface abundances of massive stars show evidence of internal mixing, while asteroseismic data suggest that efficient angular momentum (AM) transport occurs in stellar interiors. It is of interest to find a consistent physical framework that is able to account for both of these effects simultaneously.<i>Aims.<i/> We investigate the impact of the Tayler magnetic instability on the surface abundance of boron in massive B-type stars as predicted by rotating stellar models accounting for the advective nature of meridional currents.<i>Methods.<i/> We used the Geneva stellar evolution code (GENEC) to compute models of 9, 12, and 15 <i>M<i/><sub>⊙<sub/> stars at different rotational velocities and with and without magnetic fields. We compared the surface boron abundances predicted by these models with those of observed B-type stars to test the consistency between AM transport constrained by asteroseismology and chemical mixing constrained by boron abundances.<i>Results.<i/> We find that models with only hydrodynamic transport processes overestimate the amount of boron depletion for stars with high rotation rates, in disagreement with observational constraints. We show that this excessively high mixing efficiency is a direct consequence of the high degree of differential rotation predicted by purely hydrodynamic models. We thus conclude that, similarly to asteroseismic measurements, surface abundances of boron also indicate that a more efficient AM transport is needed in stellar radiative zones. We then studied the impact of the magnetic Tayler instability as a possible physical explanation to this issue. These magnetic models, which correctly reproduce asteroseismic constraints on AM transport, are found to be in good agreement with constraints on surface boron abundances, the evolutionary state, and the projected rotational velocity of moderately and fast-rotating B-type stars. We thus conclude that models accounting for the simultaneous impact of the magnetic Tayler instability and the advective nature of meridional currents offer a coherent and physically motivated theoretical framework that reproduces chemical mixing as revealed by boron abundances of fast-rotating stars and AM transport as constrained by asteroseismology. Finally, we note that at low rotational velocities (<i>v<i/> sin <i>i<i/> ≲ 50 km/s), models with magnetic fields do not predict sufficient depletion to be consistent with the observations, which are more compatible with non-magnetic models. This could suggest that the current prescriptions for transport by the Tayler instability somewhat overestimate the AM transport efficiency in slowly rotating B-type stars.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"84 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144622285","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":"Non-transiting exoplanets as a means of understanding star–planet interactions in close-in systems","authors":"C. Gourvès, S. N. Breton, A. Dyrek, A. F. Lanza, R. A. García, S. Mathur, Â. R. G. Santos, A. Strugarek","doi":"10.1051/0004-6361/202553791","DOIUrl":"https://doi.org/10.1051/0004-6361/202553791","url":null,"abstract":"Previous studies showed evidence of a dearth of close-in exoplanets around fast rotators, which can be explained by the combined action of intense tidal and magnetic interactions between planets and their host star. Detecting more exoplanets experiencing such interactions, with orbits evolving on short timescales, is therefore crucial to improve our understanding of the underlying physical mechanisms. For this purpose, we performed a new search for close-in non-transiting substellar companions in the <i>Kepler<i/> data, focusing on orbital periods below 2.3 days. We focused on main-sequence solar-type stars and subgiant stars for which a surface rotation period was measured. For each star, we looked for an excess in the power spectral density of the light curve, which could correspond to the signature of a close-in non-transiting companion. We compared our candidates with existing catalogues to eliminate potential contaminants in our sample, and we visually inspected the phase-folded light curve and its wavelet decomposition. We identify 88 stars exhibiting a signature consistent with the presence of a close non-transiting substellar companion. We show that the objects in our sample are located mostly within the dearth zone, emphasising the importance of performing follow-up of such systems in order to gather observational evidence of star-planet interactions.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"7 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144622308","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":"Intrinsic galaxy alignments in the KiDS-1000 bright sample: Dependence on colour, luminosity, morphology, and galaxy scale","authors":"Christos Georgiou, Nora Elisa Chisari, Maciej Bilicki, Francesco La Barbera, Nicola R. Napolitano, Nivya Roy, Crescenzo Tortora","doi":"10.1051/0004-6361/202554134","DOIUrl":"https://doi.org/10.1051/0004-6361/202554134","url":null,"abstract":"The intrinsic alignment of galaxies is a major astrophysical contaminant to weak gravitational lensing measurements, and the study of its dependence on galaxy properties helps provide meaningful physical priors that aid cosmological analyses. This work studied for the first time the dependence of intrinsic alignments on galaxy structural parameters. We measured the intrinsic alignments of bright galaxies, selected on apparent <i>r<i/>-band magnitude <i>r<i/><20, in the Kilo-Degree Survey (KiDS). Machine-learning-based photometric redshift estimates are available for this galaxy sample that helped us obtain a clean measurement of its intrinsic alignment signal. We supplemented this sample with a catalogue of structural parameters from Sérsic profile fits to the surface-brightness profiles of the galaxies. We split the sample on galaxy intrinsic colour, luminosity, and Sérsic index, and we fitted the non-linear linear alignment model to galaxy position–shape projected correlation function measurements on large scales. We observe a power-law luminosity dependence of the large-scale intrinsic alignment amplitude, <i>A<i/><sub>IA<sub/>, for both the red and high-Sérsic-index (<i>n<i/><sub>s<sub/>>2.5) samples, and find no significant difference between the two. We measure an ∼1.5<i>σ<i/> lower <i>A<i/><sub>IA<sub/> for red galaxies that also have a Sérsic index of <i>n<i/><sub>s<sub/><4 compared to the expected amplitude predicted using the sample's luminosity. We also probe the intrinsic alignment of red galaxies as a function of galaxy scale by varying the radial weight employed in the shape measurement. On large scales (above 6 Mpc/<i>h<i/>), we do not detect a significant difference in the alignment. On smaller scales, we observe that alignments increase with galaxy scale, with outer galaxy regions showing stronger alignments than inner regions. Finally, for intrinsically blue galaxies, we find <i>A<i/><sub>IA<sub/>=−0.67±1.00, which is consistent with previous works, and we find alignments to be consistent with zero for the low-Sérsic-index (<i>n<i/><sub>s<sub/><2.5) sample.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"22 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144602899","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}