Astronomy & Astrophysics最新文献

{"title":"A novel optimal transport-based approach for interpolating spectral time series","authors":"Mauricio Ramirez, Giuliano Pignata, Francisco Förster, Santiago González-Gaitán, Claudia P. Gutiérrez, Bastian Ayala, Guillermo Cabrera-Vives, Márcio Catelan, Alejandra M. Muñoz Arancibia, Jonathan Pineda-García","doi":"10.1051/0004-6361/202449170","DOIUrl":"https://doi.org/10.1051/0004-6361/202449170","url":null,"abstract":"<i>Context<i/>. The <i>Vera C. Rubin<i/> Observatory is set to discover 1 million supernovae (SNe) within its first operational year. Given the impracticality of spectroscopic classification at such scales, it is mandatory to develop a reliable photometric classification framework.<i>Aims<i/>. This paper introduces a novel method for creating spectral time series that can be used not only to generate synthetic light curves for photometric classification, but also in applications such as K-corrections and bolometric corrections. This approach is particularly valuable in the era of large astronomical surveys, where it can significantly enhance the analysis and understanding of an increasing number of SNe, even in the absence of extensive spectroscopic data.<i>Methods<i/>. By employing interpolations based on optimal transport theory, starting from a spectroscopic sequence, we derive weighted average spectra with high cadence. The weights incorporate an uncertainty factor for penalizing interpolations between spectra that show significant epoch differences and lead to a poor match between the synthetic and observed photometry.<i>Results<i/>. Our analysis reveals that even with a phase difference of up to 40 days between pairs of spectra, optical transport can generate interpolated spectral time series that closely resemble the original ones. Synthetic photometry extracted from these spectral time series aligns well with observed photometry. The best results are achieved in the <i>V<i/> band, with relative residuals of less than 10% for 87% and 84% of the data for type Ia and II, respectively. For the <i>B<i/>, <i>g<i/>, <i>R<i/>, and <i>r<i/> bands, the relative residuals are between 65% and 87% within the previously mentioned 10% threshold for both classes. The worse results correspond to the <i>i<i/> and <i>I<i/> bands, where, in the case of SN Ia, the values drop to 53% and 42%, respectively.<i>Conclusions<i/>. We introduce a new method for constructing spectral time series for individual SNe starting from a sparse spectroscopic sequence, and demonstrate its capability to produce reliable light curves that can be used for photometric classification.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"15 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142519517","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 tight correlation between PAH and CO emission from z ∼ 0 to 4","authors":"Irene Shivaei, Leindert A. Boogaard","doi":"10.1051/0004-6361/202451826","DOIUrl":"https://doi.org/10.1051/0004-6361/202451826","url":null,"abstract":"<i>Aims.<i/> The cold molecular gas mass is one of the crucial, yet challenging, parameters in galaxy evolution studies. Here, we introduce a new calibration and a method for estimating molecular gas masses using mid-infrared (MIR) photometry. This topic is timely as the <i>James Webb<i/> Space Telescope (JWST) now allows us to detect the MIR emission of typical main-sequence galaxies across a wide range of masses and star formation rates with modest time investments. Additionally, this Letter highlights the strong synergy between ALMA and JWST for studies of dust and gas at cosmic noon.<i>Methods.<i/> We combined a sample of 14 main-sequence galaxies at <i>z<i/> = 1 − 3 with robust CO detections and multi-band MIR photometry, along with a literature sample at <i>z<i/> = 0 − 4 with CO and polycyclic aromatic hydrocarbon (PAH) spectroscopy, to study the relationship between PAH, CO(1–0), and total IR luminosities. PAH luminosities are derived by modelling a wealth of rest-frame UV to sub-millimetre data. The new <i>z<i/> = 1 − 3 sample extends previous high-<i>z<i/> studies to PAH and CO luminosities that are about an order of magnitude lower, into the regime of local starbursts, for the first time.<i>Results.<i/> The PAH-to-CO luminosity ratio remains constant across a wide range of luminosities, for various galaxy types, and throughout the explored redshift range. In contrast, the PAH-to-IR and CO-to-IR luminosity ratios deviate from a constant value at high IR luminosities. The intrinsic scatter in the <i>L<i/>(PAH)–<i>L<i/>′(CO) relation is 0.21 dex, with a median of 1.40 and a power-law slope of 1.07 ± 0.04. Both the PAH–IR and CO–IR relations are sub-linear. Given the tight and uniform PAH–CO relation over ∼3 orders of magnitude, we provide a recipe for estimating the cold molecular gas mass of galaxies from PAH luminosities, with a PAH-to-molecular gas conversion factor of <i>α<i/><sub>PAH<sub>7.7<sub/><sub/> = (3.08 ± 1.08)(4.3/<i>α<i/><sub>CO<sub/>) <i>M<i/><sub>⊙<sub/>/<i>L<i/><sub>⊙<sub/>. This method opens a new window to explore the gas content of galaxies beyond the local Universe using multi-wavelength JWST/MIRI imaging.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"264 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142519465","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":"How external photoevaporation changes the chemical composition of the inner disc","authors":"N. Ndugu, B. Bitsch, J. L. Lienert","doi":"10.1051/0004-6361/202451633","DOIUrl":"https://doi.org/10.1051/0004-6361/202451633","url":null,"abstract":"Stars mostly form in cluster environments, where neighbouring stars can have an influence on the evolution of the newly formed protoplanetary discs. Besides gravitational interactions, external photoevaporation can also shape protoplanetary discs. Depending on the strength of external photo-evaporation, discs may be destroyed within 1–2 Myrs, or more gradually, depending on whether the external photo-evaporation field is stronger or weaker, respectively. We used the chemcomp code, which includes a viscous disc evolution model including pebble drift and evaporation to calculate the chemical composition of protoplanetary discs. We extended this code to include external photoevaporation following the FRIED grid. Before external photoevaporation becomes efficient, the disc follows a purely viscous disc evolution, where the C/O ratio in the inner disc initially decreases due to inwardly drifting and evaporating water ice pebbles. Over time, the C/O ratio increases again as water vapour is accreted onto the star and carbon-rich gas gradually migrates inwards. However, once external photo-evaporation commences, the outer disc begins to get dispersed. During this process, the inner disc’s chemical evolution still follows the evolution of a purely viscous disc because the majority of the pebbles have already drifted inwards on timescales shorter than 1 Myr. At low viscosity, the inner disc’s C/O ratio remains sub-solar until the disc is dispersed through external photoevaporation. At a high viscosity, the inner disc’s composition can reach super-solar values in C/O, because the water vapour is accreted onto the star faster and carbon rich gas from the outer disc can move inwards faster as well, as long as the disc can survive a few Myrs. In both cases, there is no visible difference in terms of the chemical composition of the inner disc compared to a purely viscous model, due to the rapid inward drift of pebbles that sets the chemical composition of the disc. Thus, our model predicts that the inner disc chemistry would be similar between discs that are subject to external photoevaporation and discs that are isolated and experience no external photo-evaporation. This finding is in line with observations of protoplanetary discs with JWST.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"61 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142519516","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":"Physical properties of trans-Neptunian object (143707) 2003 UY117 derived from stellar occultation and photometric observations","authors":"M. Kretlow, J. L. Ortiz, J. Desmars, N. Morales, F. L. Rommel, P. Santos-Sanz, M. Vara-Lubiano, E. Fernández-Valenzuela, A. Alvarez-Candal, R. Duffard, F. Braga-Ribas, B. Sicardy, A. Castro-Tirado, E. J. Fernández-García, M. Sánchez, A. Sota, M. Assafin, G. Benedetti-Rossi, R. Boufleur, J. I. B. Camargo, S. Cikota, A. Gomes-Junior, J. M. Gómez-Limón, Y. Kilic, J. Lecacheux, R. Leiva, J. Marques-Oliveira, R. Morales, B. Morgado, J. L. Rizos, F. Roques, D. Souami, R. Vieira-Martins, M. R. Alarcon, R. Boninsegna, O. Çakır, F. Casarramona, J. J. Castellani, I. de la Cueva, S. Fişek, A. Guijarro, T. Haymes, E. Jehin, S. Kidd, J. Licandro, J. L. Maestre, F. Murgas, E. Pallé, M. Popescu, A. Pratt, M. Serra-Ricart, J. C. Talbot","doi":"10.1051/0004-6361/202451329","DOIUrl":"https://doi.org/10.1051/0004-6361/202451329","url":null,"abstract":"<i>Context<i/>. Trans-Neptunian objects (TNOs) are considered to be among the most primitive objects in our Solar System. Knowledge of their primary physical properties is essential for understanding their origin and the evolution of the outer Solar System. In this context, stellar occultations are a powerful and sensitive technique for studying these distant and faint objects.<i>Aims<i/>. We aim to obtain the size, shape, absolute magnitude, and geometric albedo for TNO (143707) 2003 UY<sub>117<sub/>.<i>Methods<i/>. We predicted a stellar occultation by this TNO for 2020 October 23 UT and ran a specific campaign to investigate this event. We derived the projected profile shape and size from the occultation observations by means of an elliptical fit to the occultation chords. We also performed photometric observations of (143707) 2003 UY<sub>117<sub/> to obtain the absolute magnitude and the rotational period from the observed rotational light curve. Finally, we combined these results to derive the three-dimensional shape, volume-equivalent diameter, and geometric albedo for this TNO.<i>Results<i/>. From the stellar occultation, we obtained a projected ellipse with axes of (282 ± 18) × (184 ± 32) km. The area-equivalent diameter for this ellipse is <i>D<i/><sub>eq,A<sub/> = 228 ± 21 km. From our photometric <i>R<i/> band observations, we derived an absolute magnitude of <i>H<i/><sub><i>V<i/><sub/> = 5.97 ± 0.07 mag using <i>V<i/> − <i>R<i/> = 0.46 ± 0.07 mag, which was derived from a <i>V<i/> band subset of these data. The rotational light curve has a peak-to-valley amplitude of <i>∆m<i/> = 0.36 ± 0.13 mag. We find the most likely rotation period to be <i>P<i/> = 12.376 ± 0.0033 hours. By combining the occultation with the rotational light curve results and assuming a triaxial ellipsoid, we derived axes of <i>a<i/> × <i>b<i/> × <i>c<i/> = (332 ± 24) km × (216 ± 24) km × (180<sub>−24<sub/><sup>+28<sup/>) km for this ellipsoid, and therefore a volume-equivalent diameter of <i>D<i/><sub>eq,V<sub/> = 235 ± 25 km. Finally, the values for the absolute magnitude and for the area-equivalent diameter yield a geometric albedo of <i>p<i/><sub><i>V<i/><sub/> = 0.139 ± 0.027.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"121 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142519469","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":"Population of excited levels of Fe+, Ni+, and Cr+ in exocomets’ gaseous tails","authors":"T. Vrignaud, A. Lecavelier des Etangs","doi":"10.1051/0004-6361/202451183","DOIUrl":"https://doi.org/10.1051/0004-6361/202451183","url":null,"abstract":"The star <i>β<i/> Pictoris is widely known for harbouring a large population of exocomets, which create variable absorption signatures in the stellar spectrum as they transit the star. Although the physical and chemical properties of these objects have long been elusive, the recently developed exocomet curve of growth technique has, for the first time, enabled estimates of exocometary column densities and excitation temperatures, based on absorption measurements in mutliple spectral lines. Using this new tool, we present a refined study of a <i>β<i/> Pic exocomet observed on December 6, 1997 with the <i>Hubble<i/> Space Telescope. We first show that the comet’s signature in Fe II lines is well explained by the transit of two gaseous components, with different covering factors and opacities. Then, we show that the studied comet is detected in the lines of other species, such as Ni II and Cr II. These species are shown to experience similar physical conditions as Fe II (same radial velocity profiles and same excitation temperatures), hinting that they are well mixed. Finally, using almost 100 Fe II lines rising from energy levels between 0 and 33 000 cm<sup>–1<sup/>, we derive the complete excitation diagram of Fe<sup>+<sup/> in the comet. The transiting gas is found to be populated at an excitation temperature of 8190 ± 160 K, very close to the stellar effective temperature (8052 K). Using a model of radiative and collisional excitation, we show that the observed excitation diagram is compatible with a radiative regime, associated with a close transit distance (≤60 R<sub>⋆<sub/> ∼ 0.43 au) and a low electronic density (≤10<sup>7<sup/> cm<sup>–3<sup/>). In this regime, the excitation of Fe<sup>+<sup/> is controlled by the stellar flux, and does not depend on the local electronic temperature or density. These results allow us to derive the Ni<sup>+<sup/>/Fe<sup>+<sup/> and Cr<sup>+<sup/>/Fe<sup>+<sup/> ratios in the December 6, 1997 comet, at 8.5 ± 0.8 ⋅ 10<sup>–2<sup/> and 1.04 ± 0.15 ⋅10<sup>–2<sup/>, respectively, close to solar abundances.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"10 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142519520","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 shape of dark matter halos: A new fundamental cosmological invariance","authors":"Jean-Michel Alimi, Rémy Koskas","doi":"10.1051/0004-6361/202450845","DOIUrl":"https://doi.org/10.1051/0004-6361/202450845","url":null,"abstract":"In this article, we focus on the complex relationship between the shape of dark matter (DM) halos and the cosmological models underlying their formation. We have used three realistic cosmological models from the DEUS numerical simulation project. These three models have very distinct cosmological parameters (Ω<i><sub>m<sub/><i/>, <i>σ<i/><sub>8<sub/>, and <i>w<i/>) but their cosmic matter fields beyond the scale of DM halos are quasi-indistinguishable, providing an exemplary framework to examine the cosmological dependence of DM halo morphology. First, we developed a robust method for measuring the halo shapes detected in numerical simulations. This method avoids numerical artifacts on DM halo shape measurements, induced by the presence of substructures depending on the numerical resolution or by any spherical prior that does not respect the triaxiality of DM halos. We then obtain a marked dependence of the halo’s shape both on their mass and the cosmological model underlying their formation. As it is well known, the more massive the DM halo, the less spherical it is and we find that the higher the <i>σ<i/><sub>8<sub/> of the cosmological model, the more spherical the DM halos. Then, by reexpressing the properties of the shape of the halos in terms of the nonlinear fluctuations of the total cosmic matter field or only of the cosmic matter field which is internal to the halos, we managed to make the cosmological dependence disappear completely. This new fundamental cosmological invariance is a direct consequence of the nonlinear dynamics of the cosmic matter field. As the universe evolves, the nonlinear fluctuations of the cosmic field increase, driving the dense matter halos toward sphericity. The deviation from sphericity, measured by the prolaticity, triaxiality, and ellipticity of the DM halos, is therefore entirely encapsulated in the nonlinear power spectrum of the cosmic field. From this fundamental invariant relation, we retrieve with remarkable accuracy the root-mean-square of the nonlinear fluctuations and, consequently, the power spectrum of the cosmic matter field in which the halos formed. We also recover the <i>σ<i/><sub>8<sub/> amplitude of the cosmological model that governs the cosmic matter field at the origin of the DM halos. Our results therefore highlight, not only the nuanced relationship between DM halo formation and the underlying cosmology but also the potential of DM halo shape analysis of being a powerful tool for probing the nonlinear dynamics of the cosmic matter field.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"15 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142519463","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":"Drifts of the substellar points of the TRAPPIST-1 planets","authors":"Alexandre Revol, Émeline Bolmont, Mariana Sastre, Gabriel Tobie, Anne-Sophie Libert, Mathilde Kervazo, Sergi Blanco-Cuaresma","doi":"10.1051/0004-6361/202451532","DOIUrl":"https://doi.org/10.1051/0004-6361/202451532","url":null,"abstract":"Accurate modeling of tidal interactions is crucial for interpreting recent JWST observations of the thermal emissions of TRAPPIST-1 b and c and for characterizing the surface conditions and potential habitability of the other planets in the system. Indeed, the rotation state of the planets, driven by tidal forces, significantly influences the heat redistribution regime. Due to their proximity to their host star and the estimated age of the system, the TRAPPIST-1 planets are commonly assumed to be in a synchronization state. In this work, we present the recent implementation of the co-planar tidal torque and forces equations within the formalism of Kaula in the <i>N<i/>-body code Posidonius. This enables us to explore the hypothesis of synchronization using a tidal model well suited to rocky planets. We studied the rotational state of each planet by taking into account their multi-layer internal structure computed with the code Burnman. Our simulations show that the TRAPPIST-1 planets are not perfectly synchronized but oscillate around the synchronization state. Planet-planet interactions lead to strong variations on the mean motion and tides fail to keep the spin synchronized with respect to the mean motion. As a result, the substellar point of each planet experiences short oscillations and long-timescale drifts that lead the planets to achieve a synodic day with periods varying from 55 years to 290 years depending on the planet.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"101 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142519466","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":"Could very low-metallicity stars with rotation-dominated orbits have been driven by the bar?","authors":"Zhen Yuan, Chengdong Li, Nicolas F. Martin, Giacomo Monari, Benoit Famaey, Arnaud Siebert, Rimpei Chiba, Anke Ardern-Arentsen, Federico Sestito, Guillaume F. Thomas, Vanessa Hill, Rodrigo A. Ibata, Georges Kordopatis, Else Starkenburg, Akshara Viswanathan","doi":"10.1051/0004-6361/202348593","DOIUrl":"https://doi.org/10.1051/0004-6361/202348593","url":null,"abstract":"The most metal-poor stars (e.g., [Fe/H] ≤ –2.5) are the ancient fossils from the early assembly epoch of our Galaxy. They very likely formed before the the thick disk. Recent studies have shown that a non-negligible fraction of them have prograde planar orbits, which means that their origin is a puzzle. It has been suggested that a later-formed rotating bar could have driven these old stars from the inner Galaxy outward and transformed their orbits so that they became more dominated by rotation. However, it is unclear whether this mechanism can explain these stars as observed in the solar neighborhood. We explore whether this scenario is feasible by tracing these stars backward in an axisymmetric Milky Way potential with a bar as perturber. We integrated their orbits backward for 6 Gyr under two bar models: one model with a constant pattern speed, and the other with a decelerating speed. Our experiments show that for the constantly rotating bar model, the stars of interest are little affected by the bar and cannot have been driven from a spheroidal inner Milky Way to their current orbits. In the extreme case of a decelerating bar, some of the very metal-poor stars on planar and prograde orbits can be brought from the inner Milky Way, but ∼90% of them were nevertheless already dominated by rotation (<i>J<i/><sub><i>ϕ<i/><sub/> ≥ 1000 km s<sup>−1<sup/> kpc) 6 Gyr ago. The chance that these stars started with spheroid-like orbits with low rotation (<i>J<i/><sub><i>ϕ<i/><sub/> ≲ 600 km s<sup>−1<sup/> kpc) is very low (< 3%). We therefore conclude that within the solar neighborhood, the bar is unlikely to have shepherded a significant fraction of spheroid stars in the inner Galaxy to produce the overdensity of stars on prograde planar orbits that is observed today.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"75 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142519464","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":"Modeling long carbon-chain species formation with porous multiphase models","authors":"Ziwen Song, Qiang Chang, Qingkuan Meng, Xia Zhang","doi":"10.1051/0004-6361/202450647","DOIUrl":"https://doi.org/10.1051/0004-6361/202450647","url":null,"abstract":"<i>Context.<i/> Recent studies show that multiphase models trap too many volatile species such as CH<sub>4<sub/> inside ice mantles, so they usually underestimate the abundances of long carbon-chain species observed toward warm carbon-chain chemistry (WCCC) sources.<i>Aims.<i/> We propose a new multiphase model that allows more volatile species to diffuse out of the ice mantle upon warming. The new multiphase model is used to study the synthesis of long carbon-chain molecules in WCCC sources.<i>Methods.<i/> We included porous structure in the ice mantles. The porous structure can enlarge the active layers of ice mantles so that fewer volatile species are trapped. The porous multiphase models were simulated using an accelerated Gillespie algorithm.<i>Results.<i/> The abundances of long carbon-chain species predicted by the porous multiphase models can be more than one order of magnitude higher than those predicted by the multiphase model at temperatures relevant to WCCC sources. Moreover, the porous multiphase models predict more abundant long carbon-chain species as the porosity of the ice mantles increases. On the other hand, the two-phase model still estimates higher long carbon-chain species abundances than the porous multiphase models do. The abundances of long carbon-chain species predicted by our porous multiphase models agree reasonably well with observations toward three WCCC sources, L483, L1527, and B228.<i>Conclusions.<i/> Our porous multiphase model solves the problem of too many volatile species being trapped in ice mantles in the multiphase models.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"246 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142519468","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":"XUV irradiation of young planetary atmospheres. Results from a joint XMM-Newton and HST observation of HIP67522","authors":"A. Maggio, I. Pillitteri, C. Argiroffi, D. Locci, S. Benatti, G. Micela","doi":"10.1051/0004-6361/202451582","DOIUrl":"https://doi.org/10.1051/0004-6361/202451582","url":null,"abstract":"<i>Context<i/>. The evaporation and the chemistry of the atmospheres of warm and hot planets are strongly determined by the high-energy irradiation they receive from their parent stars. This is more crucial among young extra-solar systems because of the high activity of stars at early ages. In particular, the extreme-ultraviolet (EUV) part of the stellar spectrum drives significant processes of photochemical interaction, but it is not directly measurable because of strong interstellar absorption and a lack of sufficiently sensitive instrumentation. An alternative approach is to derive synthetic spectra from the analysis of far-ultraviolet (FUV) and X-ray emission lines, which allow us to estimate the missed flux in the EUV band.<i>Aims<i/>. We performed joint and simultaneous spectroscopy of HIP 67522 with <i>XMM-Newton<i/> and the <i>Hubble<i/> Space Telescope in order to reconstruct the full high-energy spectrum of this 17 Myr-old solar-type (G0) star, which is the youngest transiting multiplanet system known to date.<i>Methods<i/>. We performed a time-resolved spectral analysis of the observations, including quiescent emission and flaring variability. We then derived the emission measure distribution (EMD) versus temperature of the chromospheric and coronal plasma from the high-resolution spectra obtained in X-rays with RGS and in FUV with COS.<i>Results<i/>. We derived broad-band X-ray and EUV luminosities from the synthetic spectrum based on the EMD, which allowed us to test alternative EUV versus X-ray scaling laws available in the literature. We also employed the total X–EUV flux received by the inner planet of the system to estimate its instantaneous atmospheric mass-loss rate.<i>Conclusions<i/>. We confirm that HIP 67522 is a very active star with a hot corona, reaching plasma temperatures above 20 MK even in quiescent state. Its EUV/X-ray flux ratio falls in between the predictions of the two scaling laws we tested, indicating an important spread in the stellar properties, which requires further investigation.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"29 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142489000","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}