Astronomy & Astrophysics最新文献

{"title":"Time evolution of o-H2D+, N2D+, and N2H+ during the high-mass star formation process","authors":"G. Sabatini, S. Bovino, E. Redaelli, F. Wyrowski, J. S. Urquhart, A. Giannetti, J. Brand, K. M. Menten","doi":"10.1051/0004-6361/202451659","DOIUrl":"https://doi.org/10.1051/0004-6361/202451659","url":null,"abstract":"<i>Context<i/>. Deuterium fractionation is a well-established evolutionary tracer in low-mass star formation, but its applicability to the high-mass regime remains an open question. In this context, the abundances and ratios of different deuterated species have often been proposed as reliable evolutionary indicators for different stages of the high-mass star formation process.<i>Aims<i/>. In this study, we investigate the role of N<sub>2<sub/>H+ and key deuterated molecules (o-H<sub>2<sub/>D<sup>+<sup/> and N<sub>2<sub/>D<sup>+<sup/>) as tracers of the different stages of the high-mass star formation process. We assess whether their abundance ratios can serve as reliable evolutionary indicators.<i>Methods<i/>. We conducted APEX observations of o-H<sub>2<sub/>D<sup>+<sup/> (1<sub>10<sub/>–1<sub>11<sub/>), N<sub>2<sub/>H<sup>+<sup/> (4−3), and N<sub>2<sub/>D<sup>+<sup/> (3−2) in a sample of 40 high-mass clumps at different evolutionary stages, selected from the ATLASGAL survey. Molecular column densities and abundances relative to H<sub>2<sub/>, <i>X<i/>, were derived through spectral line modelling, both under local thermodynamic equilibrium (LTE) and non-LTE conditions.<i>Results<i/>. The o-H<sub>2<sub/>D<sup>+<sup/> column densities show the smallest deviation from LTE conditions when derived under non-LTE assumptions. In contrast, N<sub>2<sub/>H<sup>+<sup/> shows the largest discrepancy between the column densities derived from LTE and non-LTE. In all the cases discussed, we found that <i>X<i/>(o-H<sub>2<sub/>D<sup>+<sup/>) decreases more significantly with each respective evolutionary stage than in the case of <i>X<i/>(N<sub>2<sub/>D<sup>+<sup/>); whereas <i>X<i/>(N<sub>2<sub/>H<sup>+<sup/>) increases slightly. Therefore, the validity of the <i>X<i/>(o-H<sub>2<sub/>D<sup>+<sup/>)/<i>X<i/>(N<sub>2<sub/>D<sup>+<sup/>) ratio as a reliable evolutionary indicator, recently proposed as a promising tracer of the different evolutionary stages, was not observed for this sample. While the deuteration fraction derived from N<sub>2<sub/>D<sup>+<sup/> and N<sub>2<sub/>H<sup>+<sup/> clearly decreases with clump evolution, the interpretation of this trend is complex, given the different distribution of the two tracers.<i>Conclusions<i/>. Our results suggest that a careful consideration of the observational biases and beam-dilution effects are crucial for an accurate interpretation of the evolution of the deuteration process during the high-mass star formation process.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"23 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142857551","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":"Spatial distributions of extreme-ultraviolet brightenings in the quiet Sun","authors":"C. J. Nelson, L. A. Hayes, D. Müller, S. Musset, N. Freij, F. Auchère, R. Aznar Cuadrado, K. Barczynski, E. Buchlin, L. Harra, D. M. Long, S. Parenti, H. Peter, U. Schühle, P. Smith, L. Teriaca, C. Verbeeck, A. N. Zhukov, D. Berghmans","doi":"10.1051/0004-6361/202346886","DOIUrl":"https://doi.org/10.1051/0004-6361/202346886","url":null,"abstract":"<i>Context.<i/> The identification of large numbers of localised transient extreme ultraviolet (EUV) brightenings, on very small spatial scales, in the quiet Sun corona has been one of the key early results from Solar Orbiter. However, there are still a great deal of unknowns about these events.<i>Aims.<i/> In this work, we aim to better understand EUV brightenings by investigating their spatial distributions. Specifically, we have investigated whether they occur co-spatially with specific line-of-sight (LoS) magnetic field topologies in the photospheric network.<i>Methods.<i/> We detected the EUV brightenings in this work using an automated algorithm applied to a high-cadence (3 s) dataset sampled over ∼30 minutes on 8 March 2022 by the Extreme Ultraviolet Imager’s 17.4 nm EUV High Resolution Imager (HRI<sub>EUV<sub/>). Data from the Solar Dynamics Observatory’s Helioseismic and Magnetic Imager (SDO/HMI) and Atmospheric Imaging Assembly (SDO/AIA) were used to provide context on the LoS magnetic field and for alignment purposes, respectively.<i>Results.<i/> We found a total of 5064 EUV brightenings within this dataset that are directly comparable to events reported previously in the literature. These events occurred within around 0.015–0.020% of pixels for any given frame. We compared eight different thresholds to split the EUV brightenings into four different categories related to the LoS magnetic field. Using our preferred threshold, we found that 627 EUV brightenings (12.4%) occurred co-spatially with strong bipolar configurations and 967 EUV brightenings (19.1%) occurred in weak field regions. Fewer than 10% of EUV brightenings occurred co-spatially with the unipolar LoS magnetic field, no matter what threshold was used. Of the 627 strong bipolar EUV Brightenings, 54 were found to occur co-spatially with cancellation, whilst 57 occurred co-spatially with emergence.<i>Conclusions.<i/> EUV brightenings are primarily found to occur co-spatially with the strong LoS magnetic field in the photospheric network. However, they do not predominantly occur co-spatially with (cancelling) bi-poles.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"28 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142857548","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":"Molecular cloud matching in CO and dust in M33","authors":"Eduard Keilmann, Slawa Kabanovic, Nicola Schneider, Volker Ossenkopf-Okada, Jürgen Stutzki, Masato I. N. Kobayashi, Robert Simon, Christof Buchbender, Dominik Riechers, Frank Bigiel, Fatemeh Tabatabaei","doi":"10.1051/0004-6361/202451451","DOIUrl":"https://doi.org/10.1051/0004-6361/202451451","url":null,"abstract":"Understanding the physical properties such as mass, size, and surface mass density of giant molecular clouds or associations (GMCs/GMAs) in galaxies is crucial for gaining deeper insights into the molecular cloud and star formation (SF) processes. We determine these quantities for the Local Group flocculent spiral galaxy M33 using H<i>erschel<i/> dust and archival <sup>12<sup/>CO(2 − 1) data from the IRAM 30 m telescope, and compare them to GMC/GMA properties of the Milky Way derived from CO literature data. For M33, we apply the Dendrogram algorithm on a novel 2D dust-derived <i>N<i/><sub>H<sub>2<sub/><sub/> map at an angular resolution of 18.2″ and on the <sup>12<sup/>CO(2 − 1) data and employ an <i>X<i/><sub>CO<sub/> factor map instead of a constant value. Dust and CO-derived values are similar, with mean radii of ∼58 pc for the dust and ∼68 pc for CO, respectively. However, the largest GMAs have a radius of around 150 pc, similar to what was found in the Milky Way and other galaxies, suggesting a physical process that limits the size of GMAs. The less massive and smaller M33 galaxy also hosts less massive and lower-density GMCs compared to the Milky Way by an order of magnitude. Notably, the most massive (> a few 10<sup>6<sup/> M<sub>⊙<sub/>) GMC population observed in the Milky Way is mainly missing in M33. The mean surface mass density of M33 is significantly smaller than that of the Milky Way and this is attributed to higher column densities of the largest GMCs in the Milky Way, despite similar GMC areas. We find no systematic gradients in physical properties with the galactocentric radius in M33. However, surface mass densities and masses are higher near the center, implying increased SF activity. In both galaxies, the central region contains ∼30% of the total molecular mass. The index of the power-law spectrum of the GMC masses across the entire disk of M33 is <i>α<i/> = 2.3 ± 0.1 and <i>α<i/> = 1.9 ± 0.1 for dust- and CO-derived data, respectively. We conclude that GMC properties in M33 and the Milky Way are largely similar, though M33 lacks high-mass GMCs, for which there is no straightforward explanation. Additionally, GMC properties are only weakly dependent on the galactic environment, with stellar feedback playing a role that needs further investigation.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"7 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142849033","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":"Characterizing Jupiter’s interior using machine learning reveals four key structures","authors":"M. Ziv, E. Galanti, S. Howard, T. Guillot, Y. Kaspi","doi":"10.1051/0004-6361/202452383","DOIUrl":"https://doi.org/10.1051/0004-6361/202452383","url":null,"abstract":"<i>Context<i/>. The internal structure of Jupiter is constrained by the precise gravity field measurements by NASA’s Juno mission, atmospheric data from the Galileo entry probe, and Voyager radio occultations. Not only are these observations few compared to the possible interior setups and their multiple controlling parameters, but they remain challenging to reconcile. As a complex, multidimensional problem, characterizing typical structures can help simplify the modeling process.<i>Aims<i/>. We explored the plausible range of Jupiter’s interior structures using a coupled interior and wind model, identifying key structures and effective parameters to simplify its multidimensional representation.<i>Methods<i/>. We used NeuralCMS, a deep learning model based on the accurate concentric Maclaurin spheroid (CMS) method, coupled with a fully consistent wind model to efficiently explore a wide range of interior models without prior assumptions. We then identified those consistent with the measurements and clustered the plausible combinations of parameters controlling the interior.<i>Results<i/>. We determine the plausible ranges of internal structures and the dynamical contributions to Jupiter’s gravity field. Four typical interior structures are identified, characterized by their envelope and core properties. This reduces the dimensionality of Jupiter’s interior to only two effective parameters. Within the reduced 2D phase space, we show that the most observationally constrained structures fall within one of the key structures, but they require a higher 1 bar temperature than the observed value.<i>Conclusions<i/>. We provide a robust framework for characterizing giant planet interiors with consistent wind treatment, demonstrating that for Jupiter, wind constraints strongly impact the gravity harmonics while the interior parameter distribution remains largely unchanged. Importantly, we find that Jupiter’s interior can be described by two effective parameters that clearly distinguish the four characteristic structures and conclude that atmospheric measurements may not fully represent the entire envelope.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"7 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142848989","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":"Accurate sticking coefficient calculation for carbonaceous dust growth through accretion and desorption in astrophysical environments","authors":"D. Bossion, A. Sarangi, S. Aalto, C. Esmerian, S. R. Hashemi, K. K. Knudsen, W. Vlemmings, G. Nyman","doi":"10.1051/0004-6361/202452362","DOIUrl":"https://doi.org/10.1051/0004-6361/202452362","url":null,"abstract":"<i>Context<i/>. Cosmic dust is ubiquitous in astrophysical environments, where it significantly influences the chemistry and the spectra. Dust grains are likely to grow through the accretion of atoms and molecules from the gas-phase onto them. Despite their importance, only a few studies have computed the sticking coefficients for relevant temperatures and species, along with their direct impact on grain growth. Overall, the formation of dust and its growth are not well understood.<i>Aims<i/>. This study is aimed at calculating the sticking coefficients, binding energies, and grain growth rates over a broad range of temperatures, for various gas species interacting with carbonaceous dust grains.<i>Methods<i/>. We performed molecular dynamics simulations with a reactive force field algorithm to compute accurate sticking coefficients and obtain the binding energies. These results were used to build an astrophysical model of nucleation regions to study dust growth.<i>Results<i/>. We present, for the first time, the sticking coefficients of H, H<sub>2<sub/> , C, O, and CO on amorphous carbon structures for temperatures ranging from 50 K to 2250 K. In addition, we estimated the binding energies of H, C, and O in carbonaceous dust to calculate the thermal desorption rates. Combining accretion and desorption allows us to determine an effective accretion rate and sublimation temperature for carbonaceous dust.<i>Conclusions<i/>. We find that sticking coefficients can differ substantially from what is commonly used in astrophysical models. This offers us new insights into carbonaceous dust grain growth via accretion in dust-forming regions.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"24 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142849031","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":"Cosmography from accurate mass modeling of the lens group SDSS J0100+1818: Five sources at three different redshifts","authors":"A. Bolamperti, C. Grillo, G. B. Caminha, G. Granata, S. H. Suyu, R. Cañameras, L. Christensen, J. Vernet, A. Zanella","doi":"10.1051/0004-6361/202451209","DOIUrl":"https://doi.org/10.1051/0004-6361/202451209","url":null,"abstract":"Systems where multiple sources at different redshifts are strongly lensed by the same deflector allow one to directly investigate the evolution of the angular diameter distances as a function of redshift, and thus to learn about the geometry of the Universe. We present measurements of the values of the total matter density, Ω<sub>m<sub/>, and of the dark energy equation of state parameter, <i>w<i/>, through a detailed strong lensing analysis of SDSS J0100+1818, a group-scale system at <i>z<i/> = 0.581 with five lensed sources, from <i>z<i/> = 1.698 to 4.95. We take advantage of new spectroscopic data from the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope to securely measure the redshift of 65 sources, including the 5 multiply imaged background sources (lensed into a total of 18 multiple images) and 19 galaxies on the deflector plane, all employed to build robust strong lensing models with the software GLEE. The total mass distribution of the deflector is described in a relatively simple way, and includes an extended halo, the brightest group galaxy (BGG) with a measured stellar velocity dispersion of (380.5 ± 4.4) km s<sup>−1<sup/>, and fainter members. We measure in a flat Λ cold dark matter (CDM) model, and and in a flat <i>w<i/>CDM model. Given the presence of different sources angularly close in projection, we quantify through a multiplane approach their impact on the inferred values of the cosmological parameters. We obtain consistent median values, with uncertainties for only Ω<sub>m<sub/> increasing by approximately a factor of 1.5. Thanks to the remarkably wide radial interval where the multiple images are observed, ranging from 15 to 77 kpc from the BGG, we accurately measure the total mass profile and infer the stellar over total mass profile of the deflector. They result in a total mass of (1.55 ± 0.01)×10<sup>13<sup/> M<sub>⊙<sub/> within 50 kpc and a stellar over total mass profile decreasing from at the BGG effective radius to (6.6 ± 1.1)% at <i>R<i/> ≈ 77 kpc. Our results confirm that SDSS J0100+1818 is one of the most massive (lens) galaxies known at intermediate redshift and one of the most distant candidate fossil systems. We also show that group-scale systems that act as lenses for ≥3 background sources at different redshifts enable one to estimate the values of the cosmological parameters Ω<sub>m<sub/> and <i>w<i/> with an accuracy that is competitive with that obtained from lens galaxy clusters.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"14 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142849035","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":"Characterisation of TOI-406 as a showcase of the THIRSTEE program","authors":"G. Lacedelli, E. Pallé, R. Luque, C. Cadieux, J. M. Akana Murphy, F. Murgas, M. R. Zapatero Osorio, H. M. Tabernero, K. A. Collins, C. N. Watkins, A. L’Heureux, R. Doyon, D. Jankowski, G. Nowak, É. Artigau, N. M. Batalha, J. L. Bean, F. Bouchy, M. Brady, B. L. Canto Martins, I. Carleo, M. Cointepas, D. M. Conti, N. J. Cook, I. J. M. Crossfield, J. I. González Hernández, P. Lewin, N. Nari, L. D. Nielsen, J. Orell-Miquel, L. Parc, R. P. Schwarz, G. Srdoc, V. Van Eylen","doi":"10.1051/0004-6361/202452244","DOIUrl":"https://doi.org/10.1051/0004-6361/202452244","url":null,"abstract":"<i>Context<i/>. The exoplanet sub-Neptune population currently poses a conundrum, as to whether small-size planets are volatile-rich cores without an atmosphere, or rocky cores surrounded by a H-He envelope. To test the different hypotheses from an observational point of view, a large sample of small-size planets with precise mass and radius measurements is the first necessary step. On top of that, much more information will likely be needed, including atmospheric characterisation and a demographic perspective on their bulk properties.<i>Aims<i/>. We present here the concept and strategy of the THIRSTEE project, which aims to shed light on the composition of the sub-Neptune population across stellar types by increasing their number and improving the accuracy of bulk density measurements, as well as investigating their atmospheres and performing statistical, demographic analysis. We report the first results of the program, characterising a new two-planet system around the M-dwarf TOI-406.<i>Methods<i/>. We analysed TESS and ground-based photometry together with high-precision ESPRESSO and NIRPS/HARPS radial velocities to derive the orbital parameters and investigate the internal composition of the two planets orbiting TOI-406.<i>Results<i/>. TOI-406 hosts two planets with radii and masses of <i>R<i/><sub><i>c<i/><sub/> = 1.32 ± 0.12 R<sub>⊕<sub/>, <i>M<sub>c<sub/><i/> = 2.08<sub>−0.22<sub/><sup>+0.23<sup/> M<sub>⊕<sub/> and <i>R<i/><sub>b<sub/> = 2.08<sub>−0.15<sub/><sup>+0.16<sup/> R<sub>⊕<sub/>, <i>M<i/><sub>b<sub/> = 6.57<sub>−0.90<sub/><sup>+1.00<sup/> M<sub>⊕<sub/>, orbiting with periods of 3.3 and 13.2 days, respectively. The inner planet is consistent with an Earth-like composition, while the external one is compatible with multiple internal composition models, including volatile-rich planets without H/He atmospheres. The two planets are located in two distinct regions in the mass-density diagram, supporting the existence of a density gap among small exoplanets around M dwarfs. With an equilibrium temperature of only <i>T<i/><sub>eq<sub/> = 368 K, TOI-406 b stands up as a particularly interesting target for atmospheric characterisation with JWST in the low-temperature regime.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"51 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142849041","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":"Effects of the grain temperature distribution on the organic chemistry of protostellar envelopes","authors":"Juris Kalvāns, Juris Freimanis","doi":"10.1051/0004-6361/202451858","DOIUrl":"https://doi.org/10.1051/0004-6361/202451858","url":null,"abstract":"<i>Context.<i/> Dust grains in circumstellar envelopes are likely to have a spread-out temperature distribution.<i>Aims.<i/> We investigate how trends in the temperature distribution between small and large grains affect the hot-corino chemistry of complex organic molecules (COMs) and warm carbon-chain chemistry (WCCC).<i>Methods.<i/> A multi-grain multi-layer astrochemical code with an advanced treatment of the surface chemistry was used with three grain-temperature trends: a grain temperature proportional to the grain radius to the power -1/6 (Model M-1/6), to 0 (M0), and to 1/6 (M1/6). The cases of hot-corino chemistry and WCCC were investigated for a total of six models. The essence of these changes is that the main ice reservoir (small grains) has a higher (M-1/6) or lower (M1/6) temperature than the surrounding gas.<i>Results.<i/> The chemistry of COMs agrees better with observations in models M-1/6 and M1/6 than in Model M0. Model M-1/6 agrees best for WCCC because earlier mass-evaporation of methane ice from small grains induces the WCCC phenomenon at lower temperatures.<i>Conclusions.<i/> Models considering several grain populations with different temperatures reproduce the circumstellar chemistry more precisely.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"18 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142848864","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":"Unveiling the ice and gas nature of active centaur (2060) Chiron using the James Webb Space Telescope","authors":"N. Pinilla-Alonso, J. Licandro, R. Brunetto, E. Henault, C. Schambeau, A. Guilbert-Lepoutre, J. Stansberry, I. Wong, J. I. Lunine, B. J. Holler, J. Emery, S. Protopapa, J. Cook, H. B. Hammel, G. L. Villanueva, S. N. Milam, D. Cruikshank, A. C. de Souza-Feliciano","doi":"10.1051/0004-6361/202450124","DOIUrl":"https://doi.org/10.1051/0004-6361/202450124","url":null,"abstract":"<i>Context.<i/> (2060) Chiron is a large centaur that has been reported active on multiple occasions at relatively large heliocentric distances, including during aphelion passage. Studies of Chiron’s coma during active periods have resulted in the detection of C≡N and CO outgassing. Additionally, Chiron is surrounded by a disk of debris that varies with time. Significant work remains to be undertaken to comprehend the activation mechanisms on Chiron and the parent molecules of the gas phases detected.<i>Aims.<i/> This work reports the study of the ices on Chiron’s surface and coma and seeks spectral indicators of volatiles associated with the activity. Additionally, we discuss how these detections could be related to the activation mechanism for Chiron and, potentially, other centaurs.<i>Methods.<i/> In July 2023, the <i>James Webb<i/> Space Telescope (JWST) observed Chiron when it was active near its aphelion. We present JWST/NIRSpec spectra from 0.97 to 5.27 μm with a resolving power of ∼1000, and compare them with laboratory data for identification of the spectral bands.<i>Results<i/> We report the first detections on Chiron of absorption bands of several volatile ices, including CO<sub>2<sub/>, CO, C<sub>2<sub/>H<sub>6<sub/>, C<sub>3<sub/>H<sub>8<sub/>, and C<sub>2<sub/>H<sub>2<sub/>. We also confirm the presence of water ice in its amorphous state. A key discovery arising from these data is the detection of fluorescence emissions of CH<sub>4<sub/>, revealing the presence of a gas coma rich in this hyper-volatile molecule, which we also identify to be in non-local thermal equilibrium (non-LTE). CO<sub>2<sub/> gas emission is also detected in the fundamental stretching band at 4.27 μm. We argue that the presence of CH<sub>4<sub/> emission is the first proof of the desorption of CH<sub>4<sub/> due to a density phase transition of amorphous water ice at low temperature in agreement with the estimated temperature of Chiron during the JWST observations (61 K). Detection of photolytic and proton irradiation products of CH<sub>4<sub/> and CO<sub>2<sub/> on the surface, in the coma ice grains, or in the ring material is also detected via a forest of absorption features from 3.5 to 5.3 μm.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"115 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142848990","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":"Fate and detectability of rare gas hydride ions in nova ejecta","authors":"M. Sil, A. Das, R. Das, R. Pandey, A. Faure, H. Wiesemeyer, P. Hily-Blant, F. Lique, P. Caselli","doi":"10.1051/0004-6361/202348445","DOIUrl":"https://doi.org/10.1051/0004-6361/202348445","url":null,"abstract":"HeH<sup>+<sup/> was the first heteronuclear molecule to form in the metal-free Universe after the Big Bang. The molecule gained significant attention following its first circumstellar detection in the young and dense planetary nebula NGC 7027. We target some hydride ions associated with the noble gases (HeH<sup>+<sup/>, ArH<sup>+<sup/>, and NeH<sup>+<sup/>) to investigate their formation in harsh environments like the nova outburst region. We use a photoionization modeling (based on previously published best-fit physical parameters) of the moderately fast ONe type nova, QU Vulpeculae 1984, and the CO type novae, RS Ophiuchi and V1716 Scorpii. Our steady-state modeling reveals a convincing amount of HeH<sup>+<sup/>, especially in the dense clump of RS Ophiuchi and V1716 Scorpii. The calculated upper limit on the surface brightness of HeH<sup>+<sup/> transitions suggests that the <i>James Webb<i/> Space Telescope (JWST) could detect some of them, particularly in sources like RS Ophiuchi and V1716 Scorpii, which have similar physical and chemical conditions and evolution. It must be clearly noted that the sources studied are used as templates, and not as targets for observations. The detection of these lines could be useful for determining the physical conditions in similar types of systems and for validating our predictions based on new electron-impact ro-vibrational collisional data at temperatures of up to 20 000 K.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"58 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142848992","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}