Astronomy & Astrophysics最新文献

{"title":"Detailed seismic study of Gemma (KIC11026764) using EGGMiMoSA","authors":"M. Farnir, M.-A. Dupret, G. Buldgen","doi":"10.1051/0004-6361/202453380","DOIUrl":"https://doi.org/10.1051/0004-6361/202453380","url":null,"abstract":"<i>Context.<i/> When leaving the main sequence (MS) for the red-giant branch (RGB), subgiant stars undergo fast structural changes. Consequently, their observed oscillation spectra mirror these changes, constituting key tracers of stellar structure and evolution. However, the complexity of their spectra makes their modelling an arduous task, which few authors have undertaken. Gemma (KIC11026764) is a young subgiant with 45 precise oscillation modes observed with Kepler, making it the ideal benchmark for seismic modelling.<i>Aims.<i/> This study is aimed at modelling the subgiant Gemma, taking advantage of most of the precise seismic information available. This approach enables us to pave the way for the seismic modelling of evolved solar-like stars and provide the relevant insights into their structural evolution.<i>Methods.<i/> Using our Levenberg-Marquardt stellar modelling tool, we built a family of models representative of Gemma’s measured seismic indicators obtained via our seismic tool, EGGMiMoSA. We studied the structural information these indicators hold by carefully varying stellar parameters. We also complemented the characterisation with information held by who indicators and non-seismic data.<i>Results.<i/> From the extensive set of models we built and using most of the seismic information at hand, including two <i>ℓ<i/> = 1 and one <i>ℓ<i/> = 2 mixed modes, we were able to probe the chemical transition at the hydrogen-burning shell. Indeed, we have demonstrated that among our models, only the ones with the sharpest chemical gradient are able to reproduce all the seismic information considered. One possibility to account for such a gradient is the inclusion of a significant amount of overshooting, namely <i>α<i/><sub>ov<sub/> = 0.17, which is unexpected for low-mass stars such as Gemma (expected mass of about 1.15 <i>M<i/><sub>⊙<sub/>).","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"99 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143703050","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":"No robust statistical evidence for a population of water worlds in a 2025 sample of planets orbiting M stars","authors":"Silke Dainese, Simon H. Albrecht","doi":"10.1051/0004-6361/202452904","DOIUrl":"https://doi.org/10.1051/0004-6361/202452904","url":null,"abstract":"The study of exoplanets has led to many surprises, one of which is the discovery of planets larger than Earth yet smaller than Neptune, super Earths, and gas dwarfs. No such planet is a member of the Solar System, yet they appear to be abundant in the local neighbourhood. Their internal structure is not well understood. Super Earths presumably are rocky planets with a thin secondary atmosphere, whereas gas dwarfs have a substantial (by volume) primary H/He atmosphere. However, conflicting evidence exists regarding the presence of a third class of planets, so-called water worlds, which are hypothesised to contain a significant mass fraction of water in condensed or steam form. This study examines the evidence for water worlds and presents a sample of 60 precisely measured small exoplanets (less than 4 Earth radii) orbiting M dwarf stars. We combined observational data and unsupervised machine-learning techniques to classify these planets based on their mass, radius, and density. We individually modelled the interior of each planet using the ExoMDN code and classify them into populations based on these models. Our findings indicate that the sample divides into two distinct planet populations, with no clear evidence supporting the existence of water worlds in the current dataset.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"71 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143702925","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 large-scale radio emission enveloping the mini-halo in the most X-ray luminous galaxy cluster RX J1347.5–1145","authors":"D. N. Hoang, M. Brüggen, A. Bonafede, P. M. Koch, G. Brunetti, E. Bulbul, G. Di Gennaro, A. Liu, C. J. Riseley, H. J. A. Röttgering, R. J. van Weeren","doi":"10.1051/0004-6361/202452052","DOIUrl":"https://doi.org/10.1051/0004-6361/202452052","url":null,"abstract":"<i>Context.<i/> Diffuse radio sources, known as mini-halos and halos, are detected at the centres of galaxy clusters. These centralised diffuse sources are typically observed individually, with both appearing together only in rare cases. The origin of the diffuse radio sources in such systems remains unclear.<i>Aims.<i/> We investigate the formation of large-scale radio emission in the most X-ray luminous, massive galaxy cluster RXJ 1347.5−1145, which is known to host a mini-halo at its centre, and possibly additional and more extended emission.<i>Methods.<i/> We conducted deep multi-frequency observations of the galaxy cluster using MeerKAT at 1.28 GHz and the uGMRT at 1.26 GHz and 700 MHz. We characterised the brightness and spectral properties of the central diffuse sources and combined our radio observations with <i>Chandra<i/> X-ray data to explore the correlation between the cluster’s non-thermal and thermal emissions.<i>Results.<i/> We confirm the presence of the diffuse emission and find that it extends up to 1 Mpc in size. Our multi-wavelength data reveal that the central diffuse emission consists of two distinct components: a mini-halo located in the cluster core and a larger radio halo extending around it. The correlation between radio and X-ray surface brightness in the two sources indicates a strong connection between the non-thermal and thermal properties of the intracluster medium (ICM). The differing slopes in the <i>I<i/><sub>R<sub/> − <i>I<i/><sub>X<sub/> and <i>α<i/> − <i>I<i/><sub>X<sub/> relations suggest that distinct mechanisms are responsible for the formation of the mini-halo and the halo. The properties of the halo align with the turbulent model, while both turbulent and hadronic processes may contribute to the formation of the mini-halo.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"99 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143702984","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":"Survey of Orion Disks with ALMA (SODA)","authors":"G. Ricciardi, S. E. van Terwisga, V. Roccatagliata, A. Hacar, T. Henning, W. Del Pozzo","doi":"10.1051/0004-6361/202452287","DOIUrl":"https://doi.org/10.1051/0004-6361/202452287","url":null,"abstract":"<i>Context.<i/> Observations of protoplanetary disks within multiple systems in nearby star-forming regions (SFRs) have shown that the presence of a neighboring object influences the evolution of dust in disks. However, the size of the available sample and the separation range covered are insufficient to fully understand the dust evolution in binary systems.<i>Aims.<i/> The goal of this work, based on the Survey of Orion Disks with ALMA (SODA), is to comprehensively characterize the impact of stellar multiplicity on Class II disks in the L1641 and L1647 regions of Orion A (∼1–3 Myr). We characterized the protostellar multiplicity using the Atacama Large Millimeter/submillimeter Array (ALMA), the ESO-VISTA, and the <i>Hubble<i/> Space Telescope. The resulting sample of 65 multiple systems is the largest catalog of wide binary systems to date (projected separation ≥1000 AU) and enables a more robust statistical characterization of the evolution and properties of protoplanetary disks.<i>Methods.<i/> The disk population was observed in the continuum with ALMA at 225 GHz, with a median rms of 1.5 M<sub>⊕<sub/>. We combined these data (resolution of ∼1.1″) with the ESO-VISTA near-infrared survey of the Orion A cloud (resolution of ∼0.7″). From this dataset, multiple-star systems were selected using an iterative inside-out search in projected separation (≥1000 AU).<i>Results.<i/> We identify 61 binary systems, 3 triple systems, and 1 quadruple system. The separation range is between 1000 and 10<sup>4<sup/> AU. The dust mass distributions inferred via the Kaplan-Meier estimator yield a median mass of 3.23<sub>−0.4<sub/><sup>+0.6<sup/> M<sub>⊕<sub/> for primary disks and 3.88<sub>−0.3<sub/><sup>+0.3<sup/> M<sub>⊕<sub/> for secondary disks.<i>Conclusions.<i/> Combining our data with those available for the Lupus and Taurus disks, we identify a threshold separation of about 130 AU, beyond which the previously observed positive correlation between millimeter flux (and hence dust mass) and projected separation is lost. Recent theoretical models confirm that pre- and post-threshold systems are the result of different star formation processes, such as the fragmentation of gravitationally unstable circumstellar disks, the thermal fragmentation of infalling cores, or the turbulent fragmentation of molecular clouds. We can rule out the dependence on different SFRs: the cumulative mass distributions of multiples in SFRs of similar ages are statistically indistinguishable. This result strengthens the hypothesis that there is a universal initial mass distribution for disks.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"37 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143702988","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":"Near-infrared spectroscopic characterization of the Pallas family","authors":"P. Chavan, B. Yang, M. Brož, J. Hanuš","doi":"10.1051/0004-6361/202453489","DOIUrl":"https://doi.org/10.1051/0004-6361/202453489","url":null,"abstract":"<i>Context.<i/> Asteroid families hold clues to the collisional processes that shaped the Solar System over billions of years. The Pallas collisional family, named after (2) Pallas, is notable for its high orbital inclination and the distinct blue color of Pallas and a few larger B-type family members. While Pallas itself, as one of the largest asteroids, has been studied in detail, most of its smaller family members still remain unexplored.<i>Aims.<i/> This study aims to characterize the physical properties of medium- to small-sized Pallas family asteroids to investigate the origin of their unusual blueness. We seek to establish connections between asteroid spectra and meteorite analogs. Additionally, we explore the relationship between the Pallas family and the near-Earth object (NEO) (3200) Phaethon.<i>Methods.<i/> We conducted near-infrared (NIR) spectroscopy with the NASA Infrared Telescope Facility (IRTF) to collect reflectance spectra for 22 asteroids, including one from the IRTF Legacy Archive. Spectroscopic and dynamical analyses were carried out to identify outliers, while additional data from NEOWISE and <i>Gaia<i/> were incorporated to examine potential correlations among their physical properties. Meteorite analogs were identified through χ<sup>2<sup/> matching using samples from the RELAB database.<i>Results.<i/> The observed Pallas family asteroids exhibit nearly identical spectral profiles, suggesting a homogeneous composition of ejected material. Small variations in spectral slopes are observed, which may result from different levels of alteration experienced by individual asteroids, with some influence from variations in grain size. Most of the observed spectra of the Pallas asteroids, from 0.8 to 2.2 µm, closely resemble those of the CY and CI meteorites. The blueness of asteroid surfaces is likely due to the presence of magnetite, troilite, or phyllosilicates, which are products of aqueous alteration. The striking spectral similarity between (3200) Phaethon and Pallas family members of comparable sizes suggests a potential common origin.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"35 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143702927","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 new pulsating neutron star in the ultraluminous X-ray source NGC 4559 X7?","authors":"F. Pintore, C. Pinto, G. Rodriguez-Castillo, G. L. Israel, N. O. Pinciroli Vago, S. Motta, F. Barra, D. J. Walton, F. Fuerst, P. Kosec, C. Salvaggio, M. Del Santo, A. Wolter, M. Middleton, A. D’Aì, E. Ambrosi, L. Burderi, M. Imbrogno, R. Salvaterra, A. Robba","doi":"10.1051/0004-6361/202453240","DOIUrl":"https://doi.org/10.1051/0004-6361/202453240","url":null,"abstract":"<i>Context.<i/> Ultraluminous X-ray sources (ULX) are extragalactic objects with observed X-ray luminosities largely above the Eddington limit for a 10 M<sub>⊙<sub/> black hole. Currently, it is believed that ULXs host super-Eddington accreting neutron stars or stellar mass black holes. However, the exact proportion of the two populations of compact objects is not yet known.<i>Aims.<i/> We investigate the properties of the ULX NGC 4559 X7 (hereafter X7), which shows flux variability up to a factor of five on both long (months to years) and short (hours to days) timescales. A flaring activity was also observed during the highest flux epochs of the source. Flares are unpredictable. They have different durations (but similar rising and decay times) and are all flat topped in flux. The latter suggests that at the flare peaks, there is likely a common switch-off mechanism for the accretion onto the compact object.<i>Methods.<i/> We analysed all available <i>XMM-Newton<i/> and <i>Swift<i/>/XRT observations in order to fully investigate the spectral and temporal evolution of X7, looking for short- and long-term variability. We applied a Lomb-Scargle search to look for long-term periodicities. We also looked for coherent signals through accelerated searches that included orbital corrections. We described the X7 spectral properties with two thermal components plus a cut-off power-law model.<i>Results.<i/> We found three well-defined spectral states where the spectral variability is mainly driven by the two harder components, with the thermal one clearly following a correlation between its temperature and luminosity. In addition, a pulsed signal at 2.6 s–2.7 s was detected in two <i>XMM-Newton<i/> observations. The significance of these coherent signals is relatively weak, but they are found in two different observations with the same parameter space for the orbital properties. If confirmed, the pulsation would imply a high spin-down of 10<sup>−9<sup/> s s<sup>−1<sup/>, which could be extreme amongst the known pulsating ULXs, and X7 would become a new extragalactic ULX pulsar.<i>Conclusions.<i/> We discuss the spectral and temporal results of X7 in the context of super-Eddington accretion onto a stellar-mass compact object. In particular, we suggest that the source might likely host a neutron star.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"33 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143702922","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":"Calibrating chemical mixing induced by internal gravity waves based on hydrodynamical simulations","authors":"J. S. G. Mombarg, A. Varghese, R. P. Ratnasingam","doi":"10.1051/0004-6361/202452956","DOIUrl":"https://doi.org/10.1051/0004-6361/202452956","url":null,"abstract":"<i>Context.<i/> Internal gravity waves (IGWs) have been shown to contribute to the transport of chemical elements in stars with a convective core and radiative envelope. Recent two-dimensional hydrodynamical simulations of convection in intermediate-mass stars have provided estimates of the chemical mixing efficiency of such waves. The chemical diffusion coefficient from IGW mixing is described by a constant <i>A<i/>, times the squared wave velocity. However, the value of <i>A<i/> remains unconstrained by such simulations.<i>Aims.<i/> This work aims to investigate what values <i>A<i/> can take in order to reproduce the observed nitrogen surface abundances of the most nitrogen-enriched massive stars. Furthermore, we discuss the prevalence of IGW mixing compared to rotational mixing.<i>Methods.<i/> We provide an implementation of these (time-dependent) mixing profiles predicted from hydrodynamical simulations in the one-dimensional stellar evolution code MESA. We computed evolution tracks for stars between 3 and 30 M<sub>⊙<sub/> with this new implementation for IGW mixing and studied the evolution for the surface abundances of isotopes involved in the CNO cycle, particularly the nitrogen-14 isotope.<i>Results.<i/> We show that this one-dimensional framework that predicts the chemical diffusion coefficient from IGW mixing yields consistent morphologies of the mixing profile in comparison with hydrodynamical simulations. We find that the value of <i>A<i/> must increase with mass in order to reproduce the most nitrogen-enriched stars. If we assume these calibrated values for <i>A<i/>, mixing by IGWs is a potential mechanism to reproduce well-mixed stars without needing rapid rotation.<i>Conclusions.<i/> We have provided observational limits on the efficiency of IGW mixing for future theoretical studies. Furthermore, future asteroseismic modelling efforts that take IGW mixing into account will be able to place additional constraints on the convective core mass, as our models predict that the convective core would be significantly more massive if IGW mixing is indeed efficient.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"16 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143702923","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":"Comparison of Herschel and ArTéMiS observations of massive filaments","authors":"E. Mannfors, M. Juvela, T. Liu, V.-M. Pelkonen","doi":"10.1051/0004-6361/202346425","DOIUrl":"https://doi.org/10.1051/0004-6361/202346425","url":null,"abstract":"<i>Context.<i/> Filaments are a fundamental part of the interstellar medium (ISM). Their morphology and fragmentation can offer crucial information on the nature of the ISM and star formation. OMC-3 in the Orion A Cloud is a nearby, high-mass, star-forming region, which offers an ideal opportunity to study massive filaments in detail.<i>Aims.<i/> We analyze how the inclusion of higher resolution data affects estimates of the filament properties, including their widths and fragmentation properties. We also test the robustness of filament fitting routines.<i>Methods.<i/> We combined the ArTéMiS and <i>Herschel<i/> data to create high-resolution images. The column densities and temperatures were estimated via a modified blackbody fitting. We compared the nearby OMC-3 cloud (<i>d<i/> = 400 pc) to the more distant G202 and G17 clouds (<i>d<i/> = 760 and 1850 pc, respectively). We further compared the appearance of the OMC-3 cloud at the <i>Herschel<i/> and ArTéMiS resolution.<i>Results.<i/> Column densities of dense clumps in OMC-3 are higher in the combined ArTéMiS and <i>Herschel<i/> data (FWHM ∼ 8.5′′) when compared to <i>Herschel<i/>-only data (FWHM ∼ 20′′). The estimated filament widths are smaller in the combined maps and also show signs of further fragmentation when observed with the ArTéMiS resolution. In this analysis of <i>Herschel<i/> data, the estimated filament widths are correlated with the distance of the field.<i>Conclusions.<i/> The median filament full width at half maximum (FWHM) in OMC-3 at the higher resolution is 0.05 pc, whereas it is 0.1 pc with the <i>Herschel<i/> resolution, and then 0.3 pc in G202 and 1.0 pc in G17, also at the <i>Herschel<i/> resolution. It is unclear what causes the steep relation between the distance and filament FWHM values, however, likely reasons include the effect of the limited telescope resolution combined with existing hierarchical structure, along with the convolution of large-scale background structures within the ISM. Estimates of the asymptotic power-law index of the filament profile function, <i>p,<i/> are high. When fit with the Plummer function, the individual parameters of the profile function are degenerate, while the FWHM is better constrained. OMC-3 displays negative kurtosis, while all structures but OMC-3 at the <i>Herschel<i/> resolution reveal some asymmetry.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"57 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143703052","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 comprehensive broadband analysis of the high-redshift GRB 240218A","authors":"R. Brivio, S. Campana, S. Covino, M. Ferro, G. Gianfagna, M. G. Bernardini, P. D’Avanzo, S. Giarratana, G. Ghirlanda, Y.-D. Hu, A. Melandri, L. Nava, L. Piro, A. Rossi, O. S. Salafia, C. Salvaggio, R. Salvaterra, T. Sbarrato, B. Sbarufatti, G. Tagliaferri, A. L. Thakur, G. Tovmassian, J. F. Agüí Fernández, G. Bruni, A. J. Castro-Tirado, V. D’Elia, M. De Pasquale, A. de Ugarte Postigo, S. de Wet, D. H. Hartmann, S. Klose, S. Kobayashi, E. Maiorano, D. B. Malesani, E. Marini, A. Martin-Carrillo, A. Nicuesa Guelbenzu, S. B. Pandey, D. Paris, G. Pugliese, A. Rau, R. Ricci, A. Saccardi, R. Sánchez-Ramírez, N. R. Tanvir, C. C. Thöne, T. Zafar","doi":"10.1051/0004-6361/202452748","DOIUrl":"https://doi.org/10.1051/0004-6361/202452748","url":null,"abstract":"<i>Context.<i/> The detection and follow-up observations of high-redshift (<i>z<i/> > 6) gamma-ray bursts (GRBs) provide a unique opportunity to explore the properties of the distant Universe. Unfortunately, they are rather rare, with only a dozen of them identified so far.<i>Aims.<i/> We present here the discovery of the GRB with the second highest spectroscopic redshift measured to date, GRB 240218A at <i>z<i/> = 6.782, and the broadband analysis of its afterglow. Following the detection by high-energy satellites, we obtained multi-epoch and multi-wavelength photometric follow-up observations, from 68 s to ∼48 d after the detection. These data allow us to perform a comprehensive study of the emission and physical properties of this event. We also compare these properties with GRBs observed at high and low redshift.<i>Methods.<i/> We built the X-ray, near-infrared, and radio light curves and studied their temporal evolution. Moreover, we investigated the spectral energy distribution (SED) at different times to trace possible spectral evolution. We also compared the prompt phase properties, X-ray luminosity, and optical extinction of GRB 240218A with those of the long-duration GRB (LGRB) population.<i>Results.<i/> The SED analysis reveals a typical afterglow-like behaviour at late times. The origin of the early-time emission is uncertain, with the probable presence of an additional contribution on top of the afterglow emission. From the broadband physical modelling of the afterglow, we identify a narrow Gaussian jet seen slightly off-axis, , and pinpoint the presence of a possible jet break ∼0.86 d after the trigger.<i>Conclusions.<i/> The results of the analysis and the comparison with other high-<i>z<i/> GRBs reveal that we can consider GRB 240218A as a ‘standard’ high-redshift LGRB: the prompt phase properties, the X-ray luminosity, and the optical extinction are consistent with the values derived for the LGRB population. The jet opening angle is narrower but compatible with those of high-<i>z<i/> bursts, possibly pointing to more collimated jets at high redshift.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"41 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143702991","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":"Chemistry and ro-vibrational excitation of HeH+ in the Planetary Nebula NGC 7027","authors":"M. Sil, A. Faure, H. Wiesemeyer, P. Hily-Blant, J. Loreau, K. D. Pérez, R. Čurík, F. Lique","doi":"10.1051/0004-6361/202453173","DOIUrl":"https://doi.org/10.1051/0004-6361/202453173","url":null,"abstract":"<i>Context.<i/> The helium hydride cation (HeH<sup>+<sup/>) holds the distinction of being the first molecule to form in the metal-free Universe after the Big Bang. Following its first circumstellar detection via the pure rotational <i>J<i/> = 1 → 0 transition in the young and dense planetary nebula NGC 7027, its presence is further confirmed by detecting the <i>υ<i/> = 1 → 0 <i>P<i/>(l) and <i>P<i/>(2) ro-vibrational line emissions.<i>Aims.<i/> HeH<sup>+<sup/> belongs to the class of “reactive” ions that can be destroyed so quickly that chemical formation and destruction rates may compete with inelastic rates and should be considered when solving the statistical equilibrium equations. This so-called chemical “pumping” or “excitation” effect is investigated here for the first time in HeH<sup>+<sup/>.<i>Methods.<i/> The chemical evolution of HeH<sup>+<sup/> in NGC 7027 is modeled with the CLOUDY photoionization code using updated reaction rate coefficients. The electron temperature and atomic-molecular densities are modeled as a function of position in the nebula. The non-local thermodynamic equilibrium (NLTE) analysis of the three observed HeH<sup>+<sup/> emission lines is then performed with the CLOUDY and RADEX codes using an extensive set of spectroscopic and inelastic collisional data suitable for the specific high-temperature environment of NGC 7027. In a second approach, chemical formation and destruction rates of HeH<sup>+<sup/> are implemented in RADEX. This code is combined with a Markov Chain Monte Carlo (MCMC) sampling (performed on the RADEX-parameters space) in order to extract the best-fit HeH<sup>+<sup/> column density and physical conditions from the observed line fluxes.<i>Results.<i/> The CLOUDY and RADEX NLTE results are found to be in good agreement, and they reproduce the observed HeH<sup>+<sup/> line fluxes to within a factor of 2–5, and the <i>υ<i/> = 1 → 0 <i>P<i/>(2)/<i>P<i/>(l) line ratio to better than 20%. Agreement to better than a factor of 2.3 is obtained when including the reaction between He(2<sup>3<sup/><i>S<i/>) and H as an additional source of HeH<sup>+<sup/> in the chemical model. The RADEX-MCMC model with chemical pumping is found to reproduce both the observed line fluxes and the line ratio to 20%. However, while the best-fit parameters agree rather well with the model predictions, the posterior distributions are poorly constrained, suggesting that additional HeH<sup>+<sup/> lines must be detected in NGC 7027 to better constrain the physical conditions via NLTE models. On the other hand, uncertainties in collisional (reactive and inelastic) data of HeH<sup>+<sup/> have been largely reduced in this work. We also show that the three observed lines are not sensitive to chemical pumping while excited “short-lived” levels are significantly overpopulated with respect to a NLTE model neglecting chemical excitation. The corresponding full-line spectrum predicted for NGC 7027 is provided.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"61 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143702928","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}