Astronomy & Astrophysics最新文献

{"title":"Constraints on the possible atmospheres on TRAPPIST-1 b: insights from 3D climate modeling","authors":"Alice Maurel, Martin Turbet, Elsa Ducrot, Jérémy Leconte, Guillaume Chaverot, Gwenael Milcareck, Alexandre Revol, Benjamin Charnay, Thomas J. Fauchez, Michaël Gillon, Alexandre Mechineau, Emeline Bolmont, Ehouarn Millour, Franck Selsis, Jean-Philippe Beaulieu, Pierre Drossart","doi":"10.1051/0004-6361/202554243","DOIUrl":"https://doi.org/10.1051/0004-6361/202554243","url":null,"abstract":"<i>Context.<i/> JWST observations of the secondary eclipse of TRAPPIST-1 b at 12.8 and 15 µm revealed a very bright dayside. These measurements are consistent with an absence of atmosphere. Previous 1D atmospheric modeling also excludes – at first sight – CO<sub>2<sub/>-rich atmospheres. However, only a subset of the possible atmosphere types has been explored, and ruled out, to date. Recently, a full thermal phase curve of the planet at 15 µm with JWST has also been observed, allowing for more information on the thermal structure of the planet.<i>Aims.<i/> We first looked for atmospheres capable of producing a dayside emission compatible with secondary eclipse observations. We then tried to determine which of these are compatible with the observed thermal phase curve.<i>Methods.<i/> We used a 1D radiative-convective model and a 3D global climate model (GCM) to simulate a wide range of atmospheric compositions and surface pressures. We then produced observables from these simulations and compared them to available emission observations.<i>Results.<i/> We found several families of atmospheres compatible at 2σ with the eclipse observations. Among them, some feature a flat phase curve and can be ruled out with the observation, and some produce a phase curve still compatible with the data (i.e., thin N<sub>2<sub/> –CO<sub>2<sub/> atmospheres, and CO<sub>2<sub/> atmospheres rich in hazes). We also highlight different 3D effects that could not be predicted from 1D studies (redistribution efficiency, atmospheric collapse).<i>Conclusions.<i/> The available observations of TRAPPIST-1 b are consistent with an airless planet, which is the most likely scenario. A second possibility is a thin CO<sub>2<sub/>-poor residual atmosphere. However, our study shows that different atmospheric scenarios can result in a high eclipse depth at 15 µm. It may therefore be hazardous, in general, to conclude on the presence of an atmosphere from a single photometric point.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"164 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145059511","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 and dust dynamics in γ Cephei-type disks","authors":"Francesco Marzari, Gennaro D’Angelo","doi":"10.1051/0004-6361/202555533","DOIUrl":"https://doi.org/10.1051/0004-6361/202555533","url":null,"abstract":"<i>Context<i/>. Giant planets are observed orbiting the primary stars of close binary systems. Such planets may have formed in compact circumprimary disks, which once surrounded these stars, under conditions much different than those encountered around single stars.<i>Aims<i/>. In order to quantify the effects of the strong gravitational perturbations exerted on circumprimary disk material, the three-dimensional (3D) dynamics of gas and dust in orbit around the primary star of a compact and eccentric binary system was modeled by applying the stellar and orbital parameters of <i>γ<i/> Cephei, a well-known system that can be representative of a class of close binaries.<i>Methods<i/>. Circumprimary gas was approximated as an Eulerian viscous and compressible fluid and modeled by means of 3D hydrodynamical simulations, assuming locally isothermal conditions in the medium around the primary star. Dust grains were modeled as Lagrangean particles, subjected to gravity and aerodynamic drag forces. Models that include a giant planet were also considered.<i>Results<i/>. Models indicate that spiral density waves excited around pericenter passage propagate toward the inner boundary of the disk, through at least a few pressure scale-heights from the mid-plane, inducing radial and vertical mixing in the gas. However, perturbations imparted to gas, both in terms of eccentricity and precession, are far weaker than previously estimated by two-dimensional (2D) simulations. Models predict small eccentricities, ≲0.03, and slow retrograde precession. The addition of a giant planet does not change the low eccentricity state of the disk. The parameters applied to the disk would lead to the formation of a massive planet, many times the mass of Jupiter, in agreement with some observations. Micron to mm-size dust grains are well coupled to the gas, resulting in similar dynamics and statistically similar distributions of orbital elements. The planet only affects the dust distributions locally. In agreement with outcomes of recent 2D models, the lifetime of an isolated circumprimary disk would be brief, ~10<sup>5<sup/> years, because of its compact nature, requiring a long-term external supply of mass to allow for the in situ formation of a giant planet.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"45 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145059246","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 SPACE Program","authors":"K. Angelique Kahle, Jasmina Blecic, Reza Ashtari, Laura Kreidberg, Yui Kawashima, Patricio E. Cubillos, Drake Deming, James S. Jenkins, Paul Mollière, Seth Redfield, Qiushi Chris Tian, Jose I. Vines, David J. Wilson, Lorena Acuña, Bertram Bitsch, Jonathan Brande, Kevin France, Kevin B. Stevenson, Ian J. M. Crossfield, Tansu Daylan, Ian Dobbs-Dixon, Thomas M. Evans-Soma, Cyril Gapp, Antonio García Muñoz, Kevin Heng, Renyu Hu, Evgenya L. Shkolnik, Keivan G. Stassun, Johanna Teske","doi":"10.1051/0004-6361/202554916","DOIUrl":"https://doi.org/10.1051/0004-6361/202554916","url":null,"abstract":"Sub-Neptune exoplanets are the most abundant type of planet known today. As they do not have a Solar System counterpart, many open questions exist about their composition and formation. Previous spectroscopic studies have ruled out aerosol-free hydrogen-helium dominated atmospheres for many characterized sub-Neptunes but are inconclusive about their exact atmospheric compositions. Here we characterize the hot (T<sub>eq<sub/>=1311 K) sub-Neptune HD 86226 c (R=2.2 R<sub>⊕<sub/>, M=7.25 M<sub>⊕<sub/>), which orbits its G-type host star on a four-day orbit. The planet is located in a special part of the sub-Neptune parameter space: Its high equilibrium temperature prohibits methane-based haze formation, increasing the chances for a clear atmosphere on this planet. We used Hubble Space Telescope data taken with WFC3 and STIS from the Sub-Neptune Planetary Atmosphere Characterization Experiment (SPACE) Program to perform near-infrared (1.1–1.7 μm) transmission spectroscopy and ultraviolet characterization of the host star. We report a featureless transmission spectrum that is consistent within 0.4 <i>σ<i/> with a constant transit depth of 418 ± 14 ppm. The amplitude of this spectrum is only 0.01 scale heights for a H/He-dominated atmosphere, excluding a cloud-free solar-metallicity atmosphere on HD 86226 c with a confidence of 6.5 <i>σ<i/>. Based on an atmospheric retrieval analysis and forward models of cloud and haze formation, we find that the featureless spectrum could be due to metal enrichment [M/H] > 2.3 (3 <i>σ<i/> confidence lower limit) of a cloudless atmosphere, or silicate (MgSiO<sub>3<sub/>), iron (Fe), or manganese sulfide (MnS) clouds. For these species, we performed a detailed investigation of cloud formation in high metallicity, high-temperature atmospheres. Our results highlight that HD 86226 c does not follow the aerosol trend of sub-Neptunes found by previous studies. Follow-up observations with the James Webb Space Telescope could determine whether this planet aligns with the recent detections of metal-enriched atmospheres or if it harbors a cloud species that is otherwise atypical for sub-Neptunes.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"17 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145059248","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 multifluid method for dusty astrophysical flows","authors":"G. Verrier, U. Lebreuilly, P. Hennebelle","doi":"10.1051/0004-6361/202554662","DOIUrl":"https://doi.org/10.1051/0004-6361/202554662","url":null,"abstract":"<i>Context<i/>. Stars and planets form in collapsing clouds of gas and dust. The presence of dust grains and their local distribution play a significant role throughout the protostellar sequence, from the thermodynamics and the chemistry of molecular clouds to the opacity of collapsing protostellar cores and the coupling between the gas and the magnetic field and down to planet formation in young and evolved disks.<i>Aims<i/>. We aim to simulate the dynamics of the dust, considering the whole range of grain sizes, from few nanometers to millimeters.<i>Methods<i/>. We implemented a neutral pressureless multifluid that samples the dust size distribution in the RAMSES code. This multi-fluid is dynamically coupled to the gas via a drag source term and self-gravity, relying on the Eulerian approach.<i>Results<i/>. We designed a Riemann solver for the gas and dust mixture that prevents unphysical dust-to-gas ratio variations for well coupled grains. We illustrated the capacities of the code by performing simulations of a protostellar collapse down to the formation of a first hydrostatic core, both for small and large dust grains. Grains over 100 microns significantly decouple from the gas. The spatial maps and the probability density functions indicate that dust enrichment within the first hydrostatic core and in some locations of the envelope increases as a function of the grain size and the level of initial turbulence.<i>Conclusions<i/>. Thanks to the novel Riemann solver, we recovered the terminal velocity regime, even at low resolution. Moreover, we successfully extended it to regimes where the grain inertia matters. The multifluid module performs the coupling between the dust and the gas self-consistently all through the dynamical scales. The dust enrichment in the first hydrostatic core and the envelope have been revised here, assuming the initial turbulence and grain sizes. This enables us to probe new potential locations, epochs, and initial conditions for planet formation.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"34 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145059249","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":"Planet formation in chemically diverse and evolving discs","authors":"E. Pacetti, E. Schisano, D. Turrini, C. P. Dullemond, S. Molinari, C. Walsh, S. Fonte, U. Lebreuilly, R. S. Klessen, P. Hennebelle, S. L. Ivanovski, R. Politi, D. Polychroni, P. Simonetti, L. Testi","doi":"10.1051/0004-6361/202554012","DOIUrl":"https://doi.org/10.1051/0004-6361/202554012","url":null,"abstract":"Protoplanetary discs are dynamic environments where the interplay between chemical processes and mass transport shapes the composition of gas and dust available for planet formation. We investigate the combined effects of volatile chemistry (including both gas-phase and surface reactions), viscous gas evolution, and radial dust drift on the composition of planetary building blocks. We explore scenarios of chemical inheritance and reset under varying ionisation conditions and dust grain sizes in the submillimetre regime. We simulated the disc evolution using a semi-analytical 1D model that integrates chemical kinetics with gas and dust transport, accounting for viscous heating, turbulent mixing, and refractory organic carbon erosion. We find that mass transport plays a role in the chemical evolution of even sub-μm grains, especially in discs that have experienced strong heating or are exposed to relatively high levels of ionising radiation. The radial drift of relatively small (~100 μm) icy grains can yield significant volatile enrichment in the gas phase within the snowlines, increasing the abundances of species like H<sub>2<sub/>O, CO<sub>2<sub/>, and NH<sub>3<sub/> by up to an order of magnitude. Early planetesimal formation can lead to volatile depletion in the inner disc on timescales shorter than 0.5 Myr, while the erosion of refractory organic carbon can lead to markedly superstellar gas-phase C/O and C/N ratios. Notably, none of the analysed scenarios were able to reproduce the classical monotonic radial trend of the gas-phase C/O ratio predicted by early models. Our results also show that a pairwise comparison of elemental ratios, in the context of the host star’s composition, is key to isolating signatures of different scenarios in specific regions of the disc. We conclude that accurate models of planet formation must concurrently account for the chemical and dynamical evolution of discs, as well as the possible diversity of their initial chemical and physical conditions.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"16 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145059245","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":"Mid-infrared extinction curve for protostellar envelopes from JWST-detected embedded jet emission: The case of TMC1A","authors":"K. D. Assani, Z.-Y. Li, J. P. Ramsey, Ł. Tychoniec, L. Francis, V. J. M. Le Gouellec, A. Caratti o Garatti, T. Giannini, M. McClure, P. Bjerkeli, H. Calcutt, H. Beuther, R. Devaraj, X. Liu, A. Plunkett, M. G. Navarro, E. F. van Dishoeck, D. Harsono","doi":"10.1051/0004-6361/202555016","DOIUrl":"https://doi.org/10.1051/0004-6361/202555016","url":null,"abstract":"&lt;i&gt;Context&lt;i/&gt;. Dust grains are fundamental components of the interstellar medium (ISM), playing a crucial role in star formation as catalysts for chemical reactions and planetary building blocks. Extinction curves can serve as a tool for characterizing dust properties, however mid-infrared (MIR) extinction remains less constrained in protostellar environments. Gas-phase line ratios from embedded protostellar jets offer a spatially resolved method for measuring the extinction from protostellar envelopes, complementing traditional background starlight techniques.&lt;i&gt;Aims&lt;i/&gt;. We aim to derive MIR extinction curves along the lines of sight toward a protostellar jet embedded within an envelope and to assess whether they differ from those inferred from dense molecular clouds.&lt;i&gt;Methods&lt;i/&gt;. We analyzed JWST NIRSpec IFU and MIRI MRS observations, focusing on four locations along the blue-shifted TMC1A jet. After extracting observed [Fe II] line intensities, we modeled the intrinsic line ratios using the Cloudy spectral synthesis code across a range of electron densities and temperatures. By comparing observed near-IR (NIR) and MIR line ratios to intrinsic ratios predicted with Cloudy, we were able to infer the relative extinction between the NIR and MIR wavelengths.&lt;i&gt;Results&lt;i/&gt;. The electron densities (&lt;i&gt;n&lt;i/&gt;&lt;sub&gt;&lt;i&gt;e&lt;i/&gt;&lt;sub/&gt;) derived from NIR [Fe II] lines range from ~5 × 10&lt;sup&gt;4&lt;sup/&gt; to ~5 × 10&lt;sup&gt;3&lt;sup/&gt; cm&lt;sup&gt;−3&lt;sup/&gt; along the jet axis at scales ≲350 AU, serving as reference points for comparing the relative NIR and MIR extinction. The derived MIR extinction results display a higher reddening than empirical dark cloud curves at the corresponding &lt;i&gt;n&lt;i/&gt;&lt;sub&gt;&lt;i&gt;e&lt;i/&gt;&lt;sub/&gt; values and temperatures (from a few 10&lt;sup&gt;3&lt;sup/&gt; to ~10&lt;sup&gt;4&lt;sup/&gt; K) adopted from shock models. While both the electron density and temperature influence the NIR-to-MIR [Fe II] line ratios, the ratios are more strongly dependent on &lt;i&gt;n&lt;i/&gt;&lt;sub&gt;&lt;i&gt;e&lt;i/&gt;&lt;sub/&gt; over the adopted range. If the MIR emission originates from gas that is less dense and cooler than the NIR-emitting region, the inferred extinction curves remain consistent with background star-derived values.&lt;i&gt;Conclusions&lt;i/&gt;. This study introduces a new line-based method for deriving spatially resolved MIR extinction curves towards embedded protostellar sources exhibiting a bright [Fe II] jet. These results suggest that protostellar envelopes may contain dust with a modified grain size distribution, such as an increased fraction of larger grains (potentially due to grain growth) if the MIR and NIR lines originate from similar regions along the same sight lines. Alternatively, if the grain size distribution has not changed (i.e., there is no grain growth), the MIR lines may trace cooler, less dense gas than the NIR lines along the same sight lines. This method provides a novel approach for studying dust properties in star-forming regions that could be extended to other protostellar systems to refine extincti","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"24 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145059250","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":"Adding colour to the Zernike wavefront sensor: Advantages of including multi-wavelength measurements for wavefront reconstruction","authors":"M. Darcis, S. Y. Haffert, V. Chambouleyron, D. S. Doelman, P. J. de Visser, M. A. Kenworthy","doi":"10.1051/0004-6361/202555464","DOIUrl":"https://doi.org/10.1051/0004-6361/202555464","url":null,"abstract":"<i>Context<i/>. To directly image Earth-like planets, contrast levels of 10<sup>−8<sup/>−10<sup>−10<sup/> are required. The next generation of instruments will need wavefront control below the nanometer level to achieve these goals. The Zernike wavefront sensor (ZWFS) is a promising candidate thanks to its sensitivity, which reaches the fundamental quantum information limits. However, its highly non-linear response restricts its practical use case.<i>Aims<i/>. We aim to demonstrate the improvement in robustness of the ZWFS by reconstructing the wavefront based on multi-wavelength measurements facilitated by technologies such as the microwave kinetic inductance detectors (MKIDs).<i>Methods<i/>. We performed numerical simulations using an accelerated multi-wavelength gradient descent reconstruction algorithm. Three aspects are considered: dynamic range, photon noise sensitivity, and phase unwrapping. We examined both the scalar and vector ZWFS.<i>Results<i/>. Firstly, we find that using multiple wavelengths improves the dynamic range of the scalar ZWFS. However, for the vector ZWFS, its already extended range was not further increased. In addition, a multi-wavelength reconstruction allowed us to take advantage of a broader bandpass, which increases the number of available photons, making the reconstruction more robust to photon noise. Finally, multi-wavelength phase unwrapping enabled the measurement of large discontinuities such as petal errors with a trade-off in noise performance.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"72 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145059251","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":"Kinematic viscosity in solar convection simulations","authors":"Johannes Tschernitz, Philippe-A. Bourdin","doi":"10.1051/0004-6361/202452583","DOIUrl":"https://doi.org/10.1051/0004-6361/202452583","url":null,"abstract":"<i>Context.<i/> Numerical models are often used to improve our understanding of solar and stellar convection. To keep models numerically stable, direct numerical simulations (DNS) use various types of diffusivities. The kinematic viscosity, for example, is often chosen to be several orders of magnitude higher than realistic values. These high viscosities may distort the DNS results.<i>Aims.<i/> We test the effects of kinematic viscosity, hyperviscosity, and shock viscosity on the numerical stability for solar convection simulations with a finite-difference code. We investigated how their value ranges affect the size of the convection cells and the vertical plasma motions at grid distances of about 125 km.<i>Methods.<i/> We ran sets of convection simulations using the Pencil Code together with a density and temperature stratification that resembles the Sun. For simplicity and better understanding of the viscosity effects, we only used hydrodynamic simulations in a two-dimensional vertical plane with Cartesian coordinates, but allowed velocity vectors with three components (2.5D). Our physical domain included the upper 20 Mm of the convection zone and another 25 Mm of the solar atmosphere above the photosphere. To study each type of viscosity separately, we tested several parameters individually.<i>Results.<i/> We found differences in the length scale of the granules that depend on the kinematic viscosity <i>ν<i/>. We also found that an asymptotic behavior develops for sufficiently low values of <i>ν<i/>. An important numerically stabilizing factor is the shock viscosity, which acts in places where the kinematic viscosity is insufficient. Hyperviscosity has no significant effect on the numeric stability and length scales of the convection cells in our simulation runs.<i>Conclusions.<i/> We conclude that a kinematic viscosity of <i>ν<i/> = 1.34 ⋅ 10<sup>8<sup/> m<sup>2<sup/>/s or lower should be used for convection simulations with grid distances of about 125 km. The simulations became unstable when the kinematic viscosity was much lower than this. Shock viscosity provides additional numerical stability.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"77 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145043401","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":"Investigating the capability to infer the magnetic field from non-local thermodynamic equilibrium inversions of the Mg I 12.32 μm line","authors":"Mohamed Sedik, Xianyong Bai, Wenxian Li, Yuanyong Deng","doi":"10.1051/0004-6361/202556165","DOIUrl":"https://doi.org/10.1051/0004-6361/202556165","url":null,"abstract":"We study the diagnostic potential of the Mg I 12.32 μm spectral line for probing solar magnetic fields through inversions of Stokes profiles derived from a three-dimensional magnetohydrodynamic (3D MHD) simulation. Using the STockholm inversion Code (STiC), we synthesized and inverted the Stokes profiles of the Mg I 12.32 μm from a Bifrost simulation, focusing on a region with diverse magnetic field strengths. Our analysis evaluates the accuracy of retrieved atmospheric parameters under varying noise levels. The minimum discrepancy between inferred and original atmospheres occurs at log (<i>τ<i/><sub>500<sub/>) = − 2.9, aligning with the formation height of the Mg I 12.32 μm line. The results demonstrate robust temperature recovery even for a noise level of 1 × 10<sup>−2<sup/> relative to the continuum intensity (<i>I<i/><sub>c<sub/>), while the magnetic field components exhibit strong agreement with the simulation for noise levels up to 1 × 10<sup>−3<sup/> <i>I<i/><sub>c<sub/>. This study highlights the Mg I 12.32 μm line’s utility in diagnosing solar magnetic fields, underscoring the importance of observations at high signal-to-noise ratios for future instruments.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"28 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145043787","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":"Ionic emission from and activity evolution in comet C/2020 F3 (NEOWISE): Insights from long-slit spectroscopy and photometry","authors":"K. Aravind, E. Jehin, S. Hmmidouch, M. Vander Donckt, S. Ganesh, P. Rousselot, P. Hardy, D. Sahu, J. Manfroid, Z. Benkhaldoun","doi":"10.1051/0004-6361/202554842","DOIUrl":"https://doi.org/10.1051/0004-6361/202554842","url":null,"abstract":"<i>Aims<i/>. The long-period comet C/2020 F3 (NEOWISE) was the brightest comet in the northern hemisphere since C/1995 O1 (Hale-Bopp). These comets offer a unique opportunity to study their composition and the spatial variation in the different emission in detail. We conducted long-slit low-resolution spectroscopy and narrow-band photometry to track the evolution of its activity and composition during several weeks after perihelion. The images were used to compute the production rates of neutral molecular species and dust, and the spectrum was used to analyse the variation in the emission along the spatial axis in the sunward and anti-sunward directions to detect ionic emission.<i>Methods<i/>. Narrow-band (OH[3090 Å], NH[3362 Å], CN[3870 Å], C<sub>2<sub/>[5140 Å], C<sub>3<sub/>[4062 Å], BC[4450 Å], GC[5260 Å], and RC[7128 Å]) and broad-band (Johnson-Cousins B, V, Rc, Ic) images of comet C/2020 F3 were taken with TRAPPIST-North from 22 July to 10 September 2022 to track the production rates, the evolution of the chemical mixing ratios with solar distance, and the proxy to the dust production (A(0)f<i>ρ<i/>). A long-slit low-resolution spectrum was obtained on 24 July 2020 using HFOSC on the 2 m HCT at IAO, Hanle. Spectra extracted along the spatial axis in the sunward and anti-sunward directions enabled a comparative analysis of the emission in both directions.<i>Results<i/>. We report production rates and mixing ratios of OH, NH, CN, C<sub>2<sub/>, C<sub>3<sub/>, and NH<sub>2<sub/> and used the flux density of the forbidden oxygen line to derive the water-production rate. Ionic emission from N<sub>2<sub/><sup>+<sup/>, CO<sup>+<sup/>, CO<sub>2<sub/><sup>+<sup/>, and H<sub>2<sub/>O<sup>+<sup/> was detected at 4 × 10<sup>4<sup/> km to 1 × 10<sup>5<sup/> km from the photocentre in the tail direction. The average N<sub>2<sub/><sup>+<sup/>/CO<sup>+<sup/> ratio for the CO<sup>+<sup/> (3-0) and (2-0) bands measured from the spectrum was (3.0 ± 1.0) × 10<sup>–2<sup/>, which we further refined to (4.8 ± 2.4) × 10<sup>–2<sup/> using fluorescence modelling techniques. We measured the CO<sub>2<sub/><sup>+<sup/>/CO<sup>+<sup/> ratio to be 1.34 ± 0.21. Combining the N<sub>2<sub/><sup>+<sup/>/CO<sup>+<sup/> and CO<sub>2<sub/><sup>+<sup/>/CO<sup>+<sup/> ratios, we suggest the comet to have formed in the cold mid-outer nebula (~50–70 K). Furthermore, the average rotation period of the comet was calculated to be 7.28 ± 0.79 hours with a CN gas outflow velocity of 2.40 ± 0.25 km/s.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"36 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145043737","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}