Astronomy & Astrophysics最新文献

{"title":"The persistent nature of the Be X-ray binary pulsar 4U 0728-25","authors":"N. La Palombara, L. Sidoli, S. Mereghetti, P. Esposito, G. L. Israel","doi":"10.1051/0004-6361/202554103","DOIUrl":"https://doi.org/10.1051/0004-6361/202554103","url":null,"abstract":"We report the results obtained with a <i>XMM–Newton<i/> observation, performed in April 2023, of the poorly known Galactic Be X-ray binary pulsar 4U 0728-25. It was revealed at a flux level (not corrected for the absorption) <i>f<i/><sub>X<sub/>(0.2–12 keV) = 1.7×10<sup>−11<sup/> erg cm<sup>−2<sup/> s<sup>−1<sup/>, which implies an unabsorbed source luminosity <i>L<i/><sub>X<sub/>≃1.3×10<sup>35<sup/> erg s<sup>−1<sup/>: this is the minimum luminosity ever observed for this source. We measured a pulse period <i>P<i/><sub>spin<sub/> = 103.301(5) s, a value ≃0.15% longer than that estimated in 2016 with <i>AstroSat<i/>. The pulse profile shows a broad single peak at all energies, with a limited energy dependence and a small increase in the pulsed fraction with energy. The time-averaged <i>EPIC<i/> spectrum can be described equally well by four different emission models, either with a single non-thermal component (a partially covered power law or a cut-off power law), or with a thermal component in addition to the non-thermal one (a black body plus a power law, or a collisionally ionised gas plus a cut-off power law). All of them provided an equally good fit and, in the case of the power–law plus black–body model, the thermal component is characterized by a high temperature (<i>kT<i/><sub>BB<sub/>≃1.5 keV) and a small size (<i>R<i/><sub>BB<sub/>≃240 m), comparable with that of the neutron-star polar caps. A spectral variability along the pulse phase is present, which suggests a flux variation of the black-body component. These results show that, for its luminosity level, flux variabilty over long time scales, and spectral properties, 4U 0728-25 is very similar to most of the persistent Be X-ray binaries. Therefore, it can be considered a member of this class of sources.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143853273","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":"JWST observations of exogenic species on Jupiter: HCN, H2O, and CO2","authors":"Pablo Rodríguez-Ovalle, Thierry Fouchet, Thibault Cavalié, Emmanuel Lellouch, Leigh N. Fletcher, Jake Harkett, Vincent Hue, Bilal Benmahi, Imke de Pater","doi":"10.1051/0004-6361/202453575","DOIUrl":"https://doi.org/10.1051/0004-6361/202453575","url":null,"abstract":"<i>Context<i/>. The impact of the Shoemaker-Levy 9 (SL9) comet on Jupiter in 1994 opened up a new field of study focused on the exogenic species within Jupiter’s atmosphere. Among these species, we find H<sub>2<sub/>O, CO, and HCN. It is thought that these species coexist at the same pressure level (∼3 mbar in 2022) and that the interaction between some of them creates daughter molecules such as CO<sub>2<sub/>. However, understanding their complex meridional distributions is still a matter of debate.<i>Aims<i/>. We measured the meridional distribution of H<sub>2<sub/>O, HCN, and CO<sub>2<sub/> to understand the chemistry and dynamics leading to these distributions.<i>Methods<i/>. We used James Webb Space Telescope (JWST) Mid InfraRed Instrument (MIRI) medium-resolution spectroscopy observations from 17<sup>∘<sup/>S to 26<sup>∘<sup/>S, and from 45<sup>∘<sup/>S towards the south pole for CO<sub>2<sub/>, H<sub>2<sub/>O, and HCN. We used a radiative transfer code coupled with an inversion algorithm to retrieve the temperature using the CH<sub>4<sub/> <i>v<i/><sub>4<sub/> band and the abundance of the species for the different latitudes.<i>Results<i/>. We found an increase in H<sub>2<sub/>O in the south polar region, while CO<sub>2<sub/> is found to be depleted, which points towards an exchange of oxygen between H<sub>2<sub/>O and CO<sub>2<sub/> happening in the southern auroral region. The HCN abundance decreases towards the pole, and abundance values are similar to the ones obtained with ALMA in 2017. The depletion of HCN may be due to heterogeneous chemistry related to stratospheric polar aerosols.<i>Conclusions<i/>. The exogenic molecules analysed seem to be influenced either by polar aerosols produced by ion-neutral chemistry (e.g. HCN) or by particle precipitation occurring in the auroral regions (e.g. H<sub>2<sub/>O and CO<sub>2<sub/>). These measurements provide new insights into chemical evolution at a small spatial scale, revealing previously undetected localized trends.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"219 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143853334","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":"Kinematics of metallicity populations in Omega Centauri using the Gaia Focused Product Release and Hubble Space Telescope","authors":"N. Vernekar, S. Lucatello, P. Kuzma, L. Spina","doi":"10.1051/0004-6361/202453187","DOIUrl":"https://doi.org/10.1051/0004-6361/202453187","url":null,"abstract":"<i>Context<i/>. Omega Cen is the largest known globular cluster in the Milky Way. It is also a quite complex object with a large metallicity spread and multiple stellar populations. Despite a number of studies over the past several decades, the series of events that led to the formation of this cluster is still poorly understood. One of its peculiarities is the presence of a metal-rich population that does not show the phenomenon of light-element anti-correlations (C-N, Na-O, Mg-Al), a trait that is considered characteristic of Galactic globular clusters and present among more metal-poor Omega Cen stars. This leads to speculation that such an anomalous population was accreted by the cluster.<i>Aims<i/>. We aim to investigate the kinematics of Omega Cen populations to gain insight into the formation scenario of the cluster.<i>Methods<i/>. Using the newly released <i>Gaia<i/> FPR and DR3 catalogue, we conducted a detailed kinematical analysis of cluster members within Omega Cen. The cluster members were divided into four metallicity populations, and their mean proper motion in radial and tangential components were compared with each other. We also performed Gaussian-mixture model fitting on the metallicity distribution to estimate the number of populations within our sample and an independent analysis of the Hubble Space Telescope catalogue as confirmation.<i>Results<i/>. The mean proper motions (<i>μ<i/><sub><i>r<i/><sub/> and <i>μ<i/><sub><i>t<i/><sub/>) of the metallicity populations do not show any significant differences. It is also not dependent on the approach chosen to determine the number of metallicity populations. We do find a clear signature of rotation in all of the populations (including the metal-rich one) with similar velocities.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"13 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143853364","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":"Polarized radiation from the spreading layer of weakly magnetized neutron stars","authors":"Anna Bobrikova, Juri Poutanen, Vladislav Loktev","doi":"10.1051/0004-6361/202452358","DOIUrl":"https://doi.org/10.1051/0004-6361/202452358","url":null,"abstract":"Observations show that the X-ray emission of the accreting weakly magnetized neutron stars is polarized. We developed a theoretical model for polarized radiation from the spreading layer, which is the extension of the accretion flow boundary layer onto the neutron star surface. We calculated the Stokes parameters of the radiation and accounted for relativistic aberration and gravitational light bending in the Schwarzschild metric. We show that regardless of the geometry, the polarization degree of the spreading layer does not exceed 1.5%. Our results have implications with regard to the understanding of the X-ray polarization from weakly magnetized neutron stars observed with the Imaging X-ray Polarimetry Explorer and the future enhanced X-ray Timing and Polarimetry mission.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"13 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143853274","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":"Imaging a ring-like structure and the extended jet of M87 at 86 GHz","authors":"Jong-Seo Kim, Hendrik Müller, Aleksei S. Nikonov, Ru-Sen Lu, Jakob Knollmüller, Torsten A. Enßlin, Maciek Wielgus, Andrei P. Lobanov","doi":"10.1051/0004-6361/202452038","DOIUrl":"https://doi.org/10.1051/0004-6361/202452038","url":null,"abstract":"<i>Context<i/>. The galaxy M87 is one of the prime targets for high resolution radio imaging to investigate the ring-like “shadow” of its supermassive black hole, the innermost regions of accretion flow, and the formation of the relativistic jet. However, it remains challenging to observe them jointly due to the sparsity of the UV coverage and limited array sensitivity. In 2018, global mm-VLBI array (GMVA)+ALMA observations at 86 GHz enabled the simultaneous reconstruction of a ring structure and the extended jet emission. In order to analyze the ring and jet of M87, conventional CLEAN algorithms were mainly employed alongside the regularized maximum likelihood method SMILI in previous work.<i>Aims<i/>. To test the robustness of the reconstructed structures of M87 GMVA+ALMA observations at 86 GHz, we estimate the ring diameter, width, and the extended jet emission with the possible central spine by two different novel imaging algorithms: resolve and DoG-HiT.<i>Methods<i/>. We performed Bayesian self-calibration and imaging with uncertainty estimation using resolve. In addition, we reconstructed the image with DoG-HiT, using only interferometric closure quantities.<i>Results<i/>. Overall, reconstructions are consistent with the CLEAN and SMILI images. The ring structure of M87 is resolved at a higher resolution and the posterior distribution of M87 ring features is explored. The resolve images show that the ring diameter is 60.9 ± 2.2 μas and its width is 16.0 ± 0.9 μas. The ring diameter and the ring width measured from the DoG-HiT image are 61.0 μas and 20.6 μas, respectively. The ring diameter is therefore in agreement with the estimation (64<sub>−8<sub/><sup>+4<sup/>μas) by SMILI image reconstructions and visibility domain model fitting. Two bright spots in the ring are reconstructed by four independent imaging methods. Therefore, the substructure in the ring most likely results from the data. A consistent limb-brightened jet structure is reconstructed by resolve and DoG-HiT, albeit with a less pronounced central spine.<i>Conclusions<i/>. Modern data-driven imaging methods confirm the ring and jet structure in M87, and complement traditional VLBI methods with novel perspectives on evaluating the significance of the recovered features. They confirm the result of the previous report.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"17 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143853275","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":"New routes for PN destruction and formation in the interstellar medium via neutral-neutral gas-phase reactions and an extended database for reactions involving phosphorus","authors":"Mateus X. Silva, Edgar Mendoza, Fábio S. L. Ferreira, Alexandre C. R. Gomes, Miguel Carvajal, Jing Li, António J. C. Varandas, Breno R. L. Galvão","doi":"10.1051/0004-6361/202453204","DOIUrl":"https://doi.org/10.1051/0004-6361/202453204","url":null,"abstract":"<i>Context<i/>. Phosphorus plays an essential role in the chemistry of living organisms, being present in several fundamental biomolecules. The investigation of chemical reactions taking place in different astronomical environments involving phosphorus-containing molecules is essential for understanding how these species are produced and destroyed. Ultimately, it can help unravel the pathways that lead to important prebiotic molecules.<i>Aims<i/>. Phosphorus monoxide (PO) and phosphorus nitride (PN) are key reservoirs of phosphorus in the Interstellar Medium (ISM). Understanding their reaction mechanisms and accurately predicting rate coefficients are crucial for modelling phosphorus chemistry in space. This work presents a computational study of the CPN system to identify viable reaction pathways involving atom-diatom collisions and to explore a potential destruction route for PN in the ISM. We also evaluate the role of several neutral-neutral reactions involving PO and PN in chemical models simulating interstellar environments.<i>Methods<i/>. In this work we explore the potential energy landscape of the C(<sup>3<sup/>P) + PN(<sup>1<sup/>Σ<sup>+<sup/>), N(<sup>4<sup/>S) + CP(<sup>2<sup/>Σ<sup>+<sup/>) and P(<sup>4<sup/>S) + CN(<sup>2<sup/>Σ<sup>+<sup/>) reactions by performing high-accuracy ab initio calculations and provide their rate coefficients over a wide range of temperatures. The temperature-dependent rate coefficients were fitted to the modified Arrhenius equation: <i>k<i/>(<i>T<i/>) = <i>α<i/>(<i>T<i/>/300)<sup><i>β<i/><sup/>exp(−<i>γ<i/>/<i>T<i/>). An updated chemical network for P-bearing species was used to model the time-dependent abundances and reaction contributions of P, PO, PN, and PH (phosphinidene) during the chemical evolution of diffuse and translucent clouds and dense clouds.<i>Results<i/>. The only neutral-neutral reaction capable of destroying PN without an activation energy seems to be the PN + C one. We have also shown that reactions between CP and N can yield CN and PN barrierlessly. Chemical models indicate that PO is a crucial species driving the gas-phase formation of PN. Typically, PO/PN ratios exceed 1, though their chemistry is influenced by photon- and cosmic-ray-induced processes. Over time in simulated dense clouds, neutral-neutral reactions such as PO + N, PH + N, P + OH, and PH+O play a significant role in determining the relative abundances of PO and PN.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"17 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143853338","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":"Identifying multiplets of IceCube alert events","authors":"M. Karl, P. Padovani, P. Giommi","doi":"10.1051/0004-6361/202453333","DOIUrl":"https://doi.org/10.1051/0004-6361/202453333","url":null,"abstract":"<i>Context.<i/> The IceCube Neutrino Observatory publishes “alert events”, which are detections of high-energy neutrinos with a moderate-to-high probability of being of astrophysical origin. While some events are produced in the atmosphere, a fraction of alert events should point back to their astrophysical sources.<i>Aims.<i/> We aim to identify multiple alert events possibly related to a single astrophysical counterpart by searching for spatial and temporal clusterings in 13 years of alert data.<i>Methods.<i/> We identify spatial clusters (“multiplets”) by checking for events overlapping within their uncertainty regions. In order to reduce chance coincidences and to improve the signal purity of our sample, we apply different thresholds. We investigate the weighted mean position of these multiplets for an over-fluctuation of <i>γ<i/>-ray counterparts. As a final step, we apply expectation maximization to search for temporal clusters around the identified weighted mean positions.<i>Results.<i/> We find no statistically significant clustering of alert events around a specific origin direction or in time.<i>Conclusions.<i/> This could be because the selections are still dominated by atmospheric background. Another possibility is that we are not yet sensitive enough and only detect single events from sources. In this case, we need more data in order to observe a clustering of events around their origin.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"11 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143853331","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 COSMOS-Web ring: Spectroscopic confirmation of the background source at z = 5.1","authors":"Marko Shuntov, Shuowen Jin, Wilfried Mercier, Jeyhan S. Kartaltepe, Rebecca Larson, Ali Ahmad Khostovan, Raphaël Gavazzi, James W. Nightingale, Olivier Ilbert, Rafael Arango-Toro, Maximilien Franco, Hollis B. Akins, Caitlin M. Casey, Henry Joy McCracken, Laure Ciesla, Georgios E. Magdis, Aristeidis Amvrosiadis, Andrea Enia, Andreas L. Faisst, Anton M. Koekemoer, Clotilde Laigle, Damien Le Borgne, Richard Massey, Thibaud Moutard, Mattia Vaccari","doi":"10.1051/0004-6361/202554273","DOIUrl":"https://doi.org/10.1051/0004-6361/202554273","url":null,"abstract":"We report the spectroscopic confirmation of the background source of the most distant Einstein ring known to date, the COSMOS-Web ring. This system consists of a complete Einstein ring at <i>z<i/> = 5.1, which is lensed by a massive early-type galaxy at <i>z<i/> ∼ 2. The redshift <i>z<i/> = 5.1043 ± 0.0004 is unambiguously identified with our NOEMA and Keck/MOSFIRE spectroscopy; the NOEMA observations reveal the CO(4–3) and CO(5–4) lines at > 8<i>σ<i/>, and the MOSFIRE data detect [O II] at ∼6<i>σ<i/>. Using multiwavelength photometry spanning near-infrared to radio bands, we find that the lensed galaxy is a dust-obscured starburst (<i>M<i/><sub>⋆<sub/> ∼ 1.8 × 10<sup>10<sup/> M<sub>⊙<sub/>, SFR<sub>IR<sub/> ∼ 60 M<sub>⊙<sub/> yr<sup>−1<sup/>) with a high star formation efficiency (gas depletion time <i>τ<i/><sub>dep<sub/> < 100 Myr), as indicated by the [C I](1–0) non-detection. The redshift confirmation re-validates that the total lens mass budget within the Einstein radius is fully accounted for by the stellar and dark matter components, without the need of modifying the initial mass function or dark matter distribution profile. This work paves the way for detailed studies and future follow-ups of this unique lensing system, which is an ideal laboratory for studying mass distribution at <i>z<i/> ∼ 2 and physical conditions of star formation at <i>z<i/> ∼ 5.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"11 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143853272","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":"Revisiting the SATIRE-S irradiance reconstruction: Heritage of Mt Wilson magnetograms and Ca II K observations","authors":"Theodosios Chatzistergos, Natalie A. Krivova, Sami K. Solanki, Kok Leng Yeo","doi":"10.1051/0004-6361/202554044","DOIUrl":"https://doi.org/10.1051/0004-6361/202554044","url":null,"abstract":"<i>Context.<i/> Accurate information on long-term variations in solar irradiance, important for understanding the solar influence on Earth’s climate, cannot be derived from direct irradiance measurements due to the comparatively short lifetimes of space-borne experiments. Models using measurements of the solar photospheric magnetic field as input can provide an independent assessment of the changes.<i>Aims.<i/> The Spectral And Total Irradiance Reconstruction in the satellite era (SATIRE-S) model does just that. Unfortunately, the magnetogram archives used by SATIRE-S to recover irradiance variations are also relatively short-lived and have short mutual overlapping periods, making it difficult to evaluate their consistency. To overcome this and bridge the various archives more reliably, we include additional input data sets.<i>Methods.<i/> We improve SATIRE-S total solar irradiance (TSI) reconstruction by firstly incorporating magnetograms from the Mt Wilson Observatory as well as unsigned magnetograms reconstructed from Meudon, Rome, and San Fernando Ca II K data, and secondly, by re-analysing all periods of overlaps between the various archives.<i>Results.<i/> Our combined daily irradiance reconstruction from all eight input archives returns an excellent agreement with direct measurements of irradiance, in particular we find a correlation coefficient of 0.98 when compared to TSIS1/TIM (Total and Spectral Solar Irradiance Sensor Total Irradiance Monitor) data. The minimum-to-minimum TSI difference between 1976 and 2019 is −0.2 ± 0.17 Wm<sup>−2<sup/>, while the TSI difference between the 1986 and 2019 minima is statistically insignificant (−0.06 ± 0.13 Wm<sup>−2<sup/>). Our analysis also sheds light on the trend shown by the TSI over the so-called ACRIM gap, disfavouring a hypothesised increasing trend in TSI in that period.<i>Conclusions.<i/> By including more direct and indirect magnetogram time series, we have made the TSI reconstructed by SATIRE-S more robust and accurate. The new series shows a reduced trend of decreasing TSI over the last half century, which agrees well with most composites of measured TSI.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"4 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143853333","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":"Dynamic spectra of solar radio emissions from weak-turbulence simulation","authors":"M. Lazar, L. F. Ziebell, P. H. Yoon, R. A. López, S. Poedts","doi":"10.1051/0004-6361/202553752","DOIUrl":"https://doi.org/10.1051/0004-6361/202553752","url":null,"abstract":"<i>Context.<i/> In recent decades, serious efforts have been made in the analytical and numerical modeling of solar radio bursts generated by the electron beam interacting with the background plasma, including the dynamic spectra with decreasing frequency over time/space. These are type II and type III radio bursts, with the fundamental components at the local plasma frequency (<i>ω<i/><sub><i>p<i/><sub/> = 2<i>πf<i/><sub><i>p<i/><sub/>) and the harmonics (<i>nω<i/><sub><i>p<i/><sub/> = 2<i>πnf<i/><sub><i>p<i/><sub/>). Synthetic spectra built for a number of radio events were able to reproduce the decreasing frequency profiles reasonably well, despite the limitations of the approximate analytical theory.<i>Aims.<i/> We propose new modeling of dynamic radio emission spectra using weak-turbulence (WT) theory. This novel approach also aims at a self-consistent and quantitative evaluation of radio emissions, based on first-principles modeling of electron beam plasma instabilities and nonlinear wave interaction.<i>Methods.<i/> We performed the WT simulation, which has the ability to quantitatively describe the standard plasma emission involving the nonlinear interaction of Langmuir (<i>L<i/>), ion-sound (<i>S<i/>), and transverse electromagnetic (<i>T<i/>) waves. The composite dynamic spectra are constructed for type II- and type III-like events, against the background electron density model that behaves as an inverse square of the distance from the solar source.<i>Results.<i/> The new dynamic spectra are obtained distinctly, with a rapid frequency shift for type III emissions (generated by fast electron beams from coronal sources), as well as a less steep frequency drop for type II spectra (whose sources move away from the Sun along with interplanetary shocks). Upon making a qualitative comparison with typical solar radio emission events, we find that our first-principle-based synthetic dynamic spectra are in good agreement.<i>Conclusions.<i/> The findings of the present study demonstrate that the theoretical approach taken in this paper can be further applied to obtain (i) quantitatively relevant predictions and replications of the observed dynamic spectra of radio bursts, and (ii) more realistic large-scale models of the solar radio source, for example the type II and type III source models computed from the large-scale magnetohydrodynamics (MHD) simulations or even from direct spacecraft observations.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"41 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143853276","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}