Pub Date : 2025-11-27DOI: 10.1051/0004-6361/202556884
Thiebaut Schirmer, Theo Khouri, Wouter Vlemmings, Gunnar Nyman, Matthias Maercker, Ramlal Unnikrishnan, Behzad Bojnordi Arbab, Kirsten K. Knudsen, Susanne Aalto
Context. Mass loss in oxygen-rich asymptotic giant branch (AGB) stars remains a longstanding puzzle, as the dust species detected around these stars appear too transparent to drive winds through the absorption of radiation alone. The current paradigm consists of outflows driven by photon scattering and requires relatively large grains (∼0.3 μm). Whether the necessary number of grains with the required scattering properties exist around AGB stars remains to be determined empirically.Aims. We test whether the dust grains observed around the oxygen-rich AGB star R Doradus can drive its stellar wind by combining, for the first time, polarimetric constraints with elemental abundance limits and force balance calculations. We examine Fe-free silicates (MgSiO3), aluminium oxide (Al2O3), and Fe-bearing silicates (MgFeSiO4) to determine whether any dust species can generate sufficient radiative pressure under physically realistic conditions.Methods. We analysed high-angular-resolution polarimetric observations obtained with SPHERE/ZIMPOL at the Very Large Telescope (VLT) and modelled the circumstellar dust using the radiative transfer code RADMC-3D. Dust optical properties were computed using Optool for both Mie and the distribution of hollow spheres (DHS) scattering theories. By systematically exploring a six-dimensional parameter space, we derived constraints on dust grain sizes, density profiles, and wavelength-dependent stellar radii. For models that successfully fit the observations, we analysed the results taking into consideration recent models for the gas density distribution around R Dor, and applied a multi-criteria zone analysis incorporating gas-depletion constraints and radiation pressure thresholds to assess dust-driven wind viability.Results. We find sub-micron MgSiO3 and Al2O3 grains (up to 0.1 μm) regardless of scattering theory considered, and a two-layer dust envelope with steep density profiles (r−3.4 to r−4.1). Despite matching observed scattered-light patterns, these grains generate insufficient radiative force under physically realistic gas-to-dust mass ratios, even when assuming complete elemental depletion. Silicates containing Fe could theoretically provide adequate force, but would sublimate in critical acceleration regions and require implausibly high silicon-depletion levels.Conclusions. Our findings for R Doradus show insufficient radiation pressure from scattering on grains, suggesting that dust alone cannot drive the wind in this star and that additional mechanisms may be required.
{"title":"An empirical view of the extended atmosphere and inner envelope of the asymptotic giant branch star R Doradus","authors":"Thiebaut Schirmer, Theo Khouri, Wouter Vlemmings, Gunnar Nyman, Matthias Maercker, Ramlal Unnikrishnan, Behzad Bojnordi Arbab, Kirsten K. Knudsen, Susanne Aalto","doi":"10.1051/0004-6361/202556884","DOIUrl":"https://doi.org/10.1051/0004-6361/202556884","url":null,"abstract":"<i>Context.<i/> Mass loss in oxygen-rich asymptotic giant branch (AGB) stars remains a longstanding puzzle, as the dust species detected around these stars appear too transparent to drive winds through the absorption of radiation alone. The current paradigm consists of outflows driven by photon scattering and requires relatively large grains (∼0.3 μm). Whether the necessary number of grains with the required scattering properties exist around AGB stars remains to be determined empirically.<i>Aims.<i/> We test whether the dust grains observed around the oxygen-rich AGB star R Doradus can drive its stellar wind by combining, for the first time, polarimetric constraints with elemental abundance limits and force balance calculations. We examine Fe-free silicates (MgSiO<sub>3<sub/>), aluminium oxide (Al<sub>2<sub/>O<sub>3<sub/>), and Fe-bearing silicates (MgFeSiO<sub>4<sub/>) to determine whether any dust species can generate sufficient radiative pressure under physically realistic conditions.<i>Methods.<i/> We analysed high-angular-resolution polarimetric observations obtained with SPHERE/ZIMPOL at the Very Large Telescope (VLT) and modelled the circumstellar dust using the radiative transfer code RADMC-3D. Dust optical properties were computed using Optool for both Mie and the distribution of hollow spheres (DHS) scattering theories. By systematically exploring a six-dimensional parameter space, we derived constraints on dust grain sizes, density profiles, and wavelength-dependent stellar radii. For models that successfully fit the observations, we analysed the results taking into consideration recent models for the gas density distribution around R Dor, and applied a multi-criteria zone analysis incorporating gas-depletion constraints and radiation pressure thresholds to assess dust-driven wind viability.<i>Results.<i/> We find sub-micron MgSiO<sub>3<sub/> and Al<sub>2<sub/>O<sub>3<sub/> grains (up to 0.1 μm) regardless of scattering theory considered, and a two-layer dust envelope with steep density profiles (r<sup>−3.4<sup/> to r<sup>−4.1<sup/>). Despite matching observed scattered-light patterns, these grains generate insufficient radiative force under physically realistic gas-to-dust mass ratios, even when assuming complete elemental depletion. Silicates containing Fe could theoretically provide adequate force, but would sublimate in critical acceleration regions and require implausibly high silicon-depletion levels.<i>Conclusions.<i/> Our findings for R Doradus show insufficient radiation pressure from scattering on grains, suggesting that dust alone cannot drive the wind in this star and that additional mechanisms may be required.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"115 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145610855","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}
Pub Date : 2025-11-27DOI: 10.1051/0004-6361/202556221
A. Navarro, E. Khomenko, N. Vitas, T. Felipe
Context. Modeling the solar atmosphere is challenging due to its layered structure and dynamic multi-scale processes.Aims. We aim to validate the new radiative magnetohydrodynamic (MHD) code MAGEC—built by integrating the MANCHA3D and MAGNUS codes into a finite-volume, shock-capturing framework—and to explore its capabilities through 2D simulations of magnetoconvection in the solar atmosphere.Methods. The MAGEC code is parallelized with Message Passing Interface (MPI), enabling efficient scalability for large-scale simulations. We have enhanced it with advanced numerical techniques to address the specific complexities of the solar corona, including a module for local thermodynamic equilibrium (LTE) radiative coronal losses. To address the small time steps due to large heat flux values, we adopted the hyperbolic treatment for the thermal conduction of MANCHA3D, which significantly improves the computational times. In addition, we estimated the effective numerical resistivity and viscosity through a dedicated set of experiments. To evaluate the robustness and accuracy of MAGEC, we performed a series of 2D simulations covering a domain extending from 2 Mm below the solar surface to 18.16 Mm into the corona. Simulations were conducted with both open and closed magnetic field configurations. For each case, we analyzed the resulting steady-state temperature profiles and examined the energy contributions at different heights. In addition, we investigated the influence of the perpendicular component of thermal conduction in a dedicated simulation.Results. The MAGEC code effectively reproduced expected temperature profiles based on the boundary conditions applied and the imposed magnetic field configuration. All simulations reached a thermally stable state. When using an open vertical magnetic field, the temperature in the middle corona was higher than in the case with a closed, arcade-like magnetic field structure. We quantified the contributions to the internal energy from all explicit and implicit terms in the steady state, both in terms of temporal averages and as functions of height, as well as their relative contributions to total heating and cooling. In a second phase of the study, we investigated the role of the perpendicular component of thermal conduction, which is often neglected in coronal models, and found that it can influence plasma dynamics around reconnection events. Although local effects are modest, their cumulative impact can lead to measurable changes in the average temperature profile.Conclusions. Through detailed validation, MAGEC is a reliable and efficient code for radiative MHD simulations of the solar atmosphere. The integration of shock-capturing methods is particularly well suited to modeling the plasma environment, effectively handling the shocks and discontinuities characteristic of the solar atmosphere. MAGEC is a robust tool for high-fidelity magneto-convection simulations of the solar at
{"title":"Modeling solar atmosphere dynamics with MAGEC","authors":"A. Navarro, E. Khomenko, N. Vitas, T. Felipe","doi":"10.1051/0004-6361/202556221","DOIUrl":"https://doi.org/10.1051/0004-6361/202556221","url":null,"abstract":"<i>Context<i/>. Modeling the solar atmosphere is challenging due to its layered structure and dynamic multi-scale processes.<i>Aims<i/>. We aim to validate the new radiative magnetohydrodynamic (MHD) code MAGEC—built by integrating the MANCHA3D and MAGNUS codes into a finite-volume, shock-capturing framework—and to explore its capabilities through 2D simulations of magnetoconvection in the solar atmosphere.<i>Methods<i/>. The MAGEC code is parallelized with Message Passing Interface (MPI), enabling efficient scalability for large-scale simulations. We have enhanced it with advanced numerical techniques to address the specific complexities of the solar corona, including a module for local thermodynamic equilibrium (LTE) radiative coronal losses. To address the small time steps due to large heat flux values, we adopted the hyperbolic treatment for the thermal conduction of MANCHA3D, which significantly improves the computational times. In addition, we estimated the effective numerical resistivity and viscosity through a dedicated set of experiments. To evaluate the robustness and accuracy of MAGEC, we performed a series of 2D simulations covering a domain extending from 2 Mm below the solar surface to 18.16 Mm into the corona. Simulations were conducted with both open and closed magnetic field configurations. For each case, we analyzed the resulting steady-state temperature profiles and examined the energy contributions at different heights. In addition, we investigated the influence of the perpendicular component of thermal conduction in a dedicated simulation.<i>Results<i/>. The MAGEC code effectively reproduced expected temperature profiles based on the boundary conditions applied and the imposed magnetic field configuration. All simulations reached a thermally stable state. When using an open vertical magnetic field, the temperature in the middle corona was higher than in the case with a closed, arcade-like magnetic field structure. We quantified the contributions to the internal energy from all explicit and implicit terms in the steady state, both in terms of temporal averages and as functions of height, as well as their relative contributions to total heating and cooling. In a second phase of the study, we investigated the role of the perpendicular component of thermal conduction, which is often neglected in coronal models, and found that it can influence plasma dynamics around reconnection events. Although local effects are modest, their cumulative impact can lead to measurable changes in the average temperature profile.<i>Conclusions<i/>. Through detailed validation, MAGEC is a reliable and efficient code for radiative MHD simulations of the solar atmosphere. The integration of shock-capturing methods is particularly well suited to modeling the plasma environment, effectively handling the shocks and discontinuities characteristic of the solar atmosphere. MAGEC is a robust tool for high-fidelity magneto-convection simulations of the solar at","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"204 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145610857","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}
Pub Date : 2025-11-26DOI: 10.1051/0004-6361/202555257
V. Bosch-Ramon, M. V. Barkov
Context. LS 5039 is a system hosting a high-mass star and a compact object of unclear nature. There are hints that the system may host a strongly magnetized neutron star, a scenario that requires a mechanism to power its persistent and strong nonthermal emission.Aims. We investigate a mechanism in which the nonsteady interaction structure of the stellar and the compact object winds can regularly excite neutron star magnetospheric activity, which can release extra energy and fuel the source nonthermal emission.Methods. The neutron star wind shocked by the stellar wind can recurrently touch the neutron star magnetosphere, triggering magnetic instabilities whose growth can release extra energy into the neutron star wind in a cyclic manner. To illustrate and study the impact of these cycles on the two-wind interaction structure on different scales, we performed relativistic hydrodynamics simulations in two and three dimensions with periods of an enhanced power in the neutron star wind along the orbit. We also used analytical tools to characterize processes near the neutron star relevant for the nonthermal emission.Results. As the neutron star wind termination shock touches the magnetosphere energy dissipation occurs, but the whole shocked two-wind structure is eventually driven away, stopping the extra energy injection. However, due to the corresponding drop in the neutron star wind ram pressure, the termination shock propagates back toward the magnetosphere, resuming the process. These cycles of activity excite strong waves in the shocked flows, intensifying their mixing and the disruption of their spiral-like structure produced by orbital motion. Further downstream, the shocked winds can become a quasi-stable, relatively smooth flow.Conclusions. The recurrent interaction between the neutron star magnetosphere and a shocked wind can fuel a relativistic outflow powerful enough to explain the nonthermal emission of LS 5039. A magnetospheric multipolar magnetic field much stronger than the dipolar one may provide the required energetics, and help to explain the lack of evidence of a recent supernova remnant.
{"title":"Magnetar-like flares behind the high-energy emission in LS 5039","authors":"V. Bosch-Ramon, M. V. Barkov","doi":"10.1051/0004-6361/202555257","DOIUrl":"https://doi.org/10.1051/0004-6361/202555257","url":null,"abstract":"<i>Context.<i/> LS 5039 is a system hosting a high-mass star and a compact object of unclear nature. There are hints that the system may host a strongly magnetized neutron star, a scenario that requires a mechanism to power its persistent and strong nonthermal emission.<i>Aims.<i/> We investigate a mechanism in which the nonsteady interaction structure of the stellar and the compact object winds can regularly excite neutron star magnetospheric activity, which can release extra energy and fuel the source nonthermal emission.<i>Methods.<i/> The neutron star wind shocked by the stellar wind can recurrently touch the neutron star magnetosphere, triggering magnetic instabilities whose growth can release extra energy into the neutron star wind in a cyclic manner. To illustrate and study the impact of these cycles on the two-wind interaction structure on different scales, we performed relativistic hydrodynamics simulations in two and three dimensions with periods of an enhanced power in the neutron star wind along the orbit. We also used analytical tools to characterize processes near the neutron star relevant for the nonthermal emission.<i>Results.<i/> As the neutron star wind termination shock touches the magnetosphere energy dissipation occurs, but the whole shocked two-wind structure is eventually driven away, stopping the extra energy injection. However, due to the corresponding drop in the neutron star wind ram pressure, the termination shock propagates back toward the magnetosphere, resuming the process. These cycles of activity excite strong waves in the shocked flows, intensifying their mixing and the disruption of their spiral-like structure produced by orbital motion. Further downstream, the shocked winds can become a quasi-stable, relatively smooth flow.<i>Conclusions.<i/> The recurrent interaction between the neutron star magnetosphere and a shocked wind can fuel a relativistic outflow powerful enough to explain the nonthermal emission of LS 5039. A magnetospheric multipolar magnetic field much stronger than the dipolar one may provide the required energetics, and help to explain the lack of evidence of a recent supernova remnant.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"255 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145609693","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}
Pub Date : 2025-11-26DOI: 10.1051/0004-6361/202554569
P. Disberg, A. Lankreijer, M. Chruślińska, A. J. Levan, G. Nelemans, N. R. Tanvir, C. R. Angus, I. Mandel
Context. Theoretical models and observations of collapsar-created gamma-ray bursts, typically long-duration gamma-ray bursts (LGRBs), both suggest that these transients cannot occur at high metallicity, likely due to angular momentum losses via stellar winds for potential progenitor stars. However, the precise metallicity threshold (if it is a hard threshold) above which the formation of LGRBs is suppressed is still a topic of discussion.Aims. We investigated observed LGRBs and the properties of their host galaxies to constrain this metallicity dependence.Methods. In order to compute LGRB rates we modelled the cosmic history of star formation as a function of host galaxy metallicity and stellar mass, and added a LGRB efficiency function that can include various shapes including abrupt cutoffs and more gradual variations in the GRB yield with metallicity. In contrast to previous work, this model includes scatters in the relations between mass, metallicity, and star formation rate, as well as a scatter in the metallicity distribution inside galaxies. We then varied both the threshold value and the shape, and compared the results of our model to observed LGRBs and the properties of their host galaxies.Results. In our model a sharp cutoff at an oxygen abundance ZO/H = 12 + log(O/H) = 8.6 ± 0.1 (corresponding to ~0.6 Z⊙) provides the best explanation for the observed LGRB data. In contrast, a lower threshold proposed in the literature (i.e. at ZO/H = 8.3 or ~0.3 Z⊙) fits the observations poorly.Conclusions. We therefore conclude that, in contrast to most theoretical LGRB models, a relatively high metallicity threshold at near solar values provides the best match between our model and observed LGRBs.
{"title":"The metallicity dependence of long-duration gamma-ray bursts","authors":"P. Disberg, A. Lankreijer, M. Chruślińska, A. J. Levan, G. Nelemans, N. R. Tanvir, C. R. Angus, I. Mandel","doi":"10.1051/0004-6361/202554569","DOIUrl":"https://doi.org/10.1051/0004-6361/202554569","url":null,"abstract":"<i>Context<i/>. Theoretical models and observations of collapsar-created gamma-ray bursts, typically long-duration gamma-ray bursts (LGRBs), both suggest that these transients cannot occur at high metallicity, likely due to angular momentum losses via stellar winds for potential progenitor stars. However, the precise metallicity threshold (if it is a hard threshold) above which the formation of LGRBs is suppressed is still a topic of discussion.<i>Aims<i/>. We investigated observed LGRBs and the properties of their host galaxies to constrain this metallicity dependence.<i>Methods<i/>. In order to compute LGRB rates we modelled the cosmic history of star formation as a function of host galaxy metallicity and stellar mass, and added a LGRB efficiency function that can include various shapes including abrupt cutoffs and more gradual variations in the GRB yield with metallicity. In contrast to previous work, this model includes scatters in the relations between mass, metallicity, and star formation rate, as well as a scatter in the metallicity distribution inside galaxies. We then varied both the threshold value and the shape, and compared the results of our model to observed LGRBs and the properties of their host galaxies.<i>Results<i/>. In our model a sharp cutoff at an oxygen abundance <i>Z<i/><sub>O/H<sub/> = 12 + log(O/H) = 8.6 ± 0.1 (corresponding to ~0.6 <i>Z<i/><sub>⊙<sub/>) provides the best explanation for the observed LGRB data. In contrast, a lower threshold proposed in the literature (i.e. at <i>Z<i/><sub>O/H<sub/> = 8.3 or ~0.3 <i>Z<i/><sub>⊙<sub/>) fits the observations poorly.<i>Conclusions<i/>. We therefore conclude that, in contrast to most theoretical LGRB models, a relatively high metallicity threshold at near solar values provides the best match between our model and observed LGRBs.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"8 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145609712","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}
Pub Date : 2025-11-26DOI: 10.1051/0004-6361/202555634
Bhawna Mukhija, Michel Curé, Ignacio Araya, Catalina Arcos, Alejandra Christen
Context. Rapid rotation in massive stars leads to gravity darkening and oblateness, significantly affecting their radiation-driven winds. These effects can alter wind dynamics and play a role in forming slowly equatorial outflowing winds.Aims. This work investigates the transition region where the fast solution (i.e. high terminal velocities) of radiation-driven winds in a massive rotating star, in the frame of the modified-CAK theory, switches to the Ω-slow solutions (a denser and slower wind) when the effects of gravity darkening and oblateness are considered. This Ω-slow solution appears when the rotational speed is ≳75% of the critical rotation speed.Methods. To explore the transition region for various equatorial models of B-type stars, we focus on the co-existence interval where both solutions simultaneously exist and the transition point where fast solutions switch to Ω-slow solutions.Results. Using our stationary numerical code HYDWIND, we first analyse the individual effects of gravity darkening and stellar oblateness caused by high rotational speeds and then examine their combined impact on the wind solutions.Conclusions. We find that for a certain range of rotational speeds, both the fast and Ω-slow solutions can co-exist, and the co-existence range strongly depends on the initial conditions. When only gravity darkening is considered, the co-existing interval shifts towards higher rotational speeds. While in the presence of the oblateness, the co-existing interval also occurs at higher rotational speeds; however, it is less than the gravity darkening effect. We also explored how line-force parameters affect the critical point, the location of the co-existing interval, and where the solution switches.
{"title":"Effect of gravity darkening and oblate factor in rapidly rotating massive stars","authors":"Bhawna Mukhija, Michel Curé, Ignacio Araya, Catalina Arcos, Alejandra Christen","doi":"10.1051/0004-6361/202555634","DOIUrl":"https://doi.org/10.1051/0004-6361/202555634","url":null,"abstract":"<i>Context<i/>. Rapid rotation in massive stars leads to gravity darkening and oblateness, significantly affecting their radiation-driven winds. These effects can alter wind dynamics and play a role in forming slowly equatorial outflowing winds.<i>Aims<i/>. This work investigates the transition region where the fast solution (i.e. high terminal velocities) of radiation-driven winds in a massive rotating star, in the frame of the modified-CAK theory, switches to the Ω-slow solutions (a denser and slower wind) when the effects of gravity darkening and oblateness are considered. This Ω-slow solution appears when the rotational speed is ≳75% of the critical rotation speed.<i>Methods<i/>. To explore the transition region for various equatorial models of B-type stars, we focus on the co-existence interval where both solutions simultaneously exist and the transition point where fast solutions switch to Ω-slow solutions.<i>Results<i/>. Using our stationary numerical code HYDWIND, we first analyse the individual effects of gravity darkening and stellar oblateness caused by high rotational speeds and then examine their combined impact on the wind solutions.<i>Conclusions<i/>. We find that for a certain range of rotational speeds, both the fast and Ω-slow solutions can co-exist, and the co-existence range strongly depends on the initial conditions. When only gravity darkening is considered, the co-existing interval shifts towards higher rotational speeds. While in the presence of the oblateness, the co-existing interval also occurs at higher rotational speeds; however, it is less than the gravity darkening effect. We also explored how line-force parameters affect the critical point, the location of the co-existing interval, and where the solution switches.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145609694","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}
Pub Date : 2025-11-26DOI: 10.1051/0004-6361/202557188
V. D’Orazi, G. Iorio, B. Cseh, C. Sneden, H. Abdollahi, L. Molnár, A. Bobrick, G. Bono, V. F. Braga, A. Karakas, M. Lugaro, S. W. Campbell, M. Fabrizio, G. Fiorentino, I. U. Roederer, N. Storm, M. Tantalo, J. Crestani
Aims. We report the serendipitous discovery of two RR Lyrae stars that exhibit significant s-process element enrichment, a rare class previously represented solely by TY Gruis. Our goal is to characterise these objects chemically and dynamically, and explore their origins and evolutionary histories.Methods. Using high-resolution spectroscopy from HERMES@AAT and UVES@VLT, we derived detailed chemical abundances of key s-process elements (Y, Ba, La, Ce, Nd, and Eu) and carbon, along with α elements (Ca, Mg, and Ti). We also employed Gaia Data Release 3 astrometric data to analyse their kinematics, orbital properties, and classify their Galactic population membership. We compared observational results with theoretical asymptotic giant branch (AGB) nucleosynthesis models to interpret their enrichment patterns.Results. Both stars exhibit clear signatures of s-process enrichment, with significant overabundances in second-peak elements such as Ba and La compared to first-peak Y and Zr. Comparison with AGB nucleosynthesis models suggests their progenitors experienced pollution of s-process-rich material, consistent with early binary interactions. However, notable discrepancies in dilution factors highlight the need for more refined low-metallicity AGB models. We also explore and discuss alternative scenarios, including sub-luminous post-AGB-like evolution or double episodes of mass transfer. In the latter case, the star initially undergoes a mass transfer when it is on the main sequence, accreting material from a former AGB companion. Subsequently, as the star evolves along the red giant branch, it may again transfer mass to its companion before becoming an RR Lyrae star.Conclusions. Our findings confirm the existence of s-process-enhanced RR Lyrae stars and demonstrate the importance of combining chemical and dynamical diagnostics to unveil their complex evolutionary pathways. Future detailed binary evolution modelling and long-term orbital monitoring are essential to resolve their formation scenarios and assess the role of binarity in the evolution of pulsating variables.
目标。我们报告了两颗偶然发现的天琴座RR星，它们表现出显著的s过程元素富集，这是一个罕见的类别，以前只由TY Gruis代表。我们的目标是用化学和动态的方法来描述这些物体，并探索它们的起源和进化历史。利用HERMES@AAT和UVES@VLT上的高分辨率光谱，我们得到了关键s过程元素（Y, Ba, La, Ce， Nd和Eu）和碳以及α元素（Ca， Mg和Ti）的详细化学丰度。我们还使用了Gaia Data Release 3天文测量数据来分析它们的运动学、轨道特性，并对它们的银河系人口成员进行分类。我们将观测结果与理论渐近巨支（AGB）核合成模型进行了比较，以解释它们的富集模式。这两颗恒星都表现出明显的s过程富集特征，与第一峰元素Y和Zr相比，第二峰元素Ba和La的丰度明显过高。与AGB核合成模型的比较表明，它们的祖先经历了富含s过程物质的污染，与早期的二元相互作用一致。然而，稀释因子的显著差异突出了对更精细的低金属丰度AGB模型的需求。我们还探索和讨论了替代方案，包括亚发光后agb样进化或双重传质。在后一种情况下，当恒星处于主序星时，它最初经历了一次质量传递，从以前的AGB伴星中吸积物质。随后，随着这颗恒星沿着红巨星分支演化，它可能会在成为天琴座RR星之前再次将质量转移给它的伴星。我们的发现证实了s过程增强的天琴座RR恒星的存在，并证明了将化学和动力学诊断相结合以揭示其复杂的进化途径的重要性。未来详细的二元演化建模和长期轨道监测对于解决它们的形成情景和评估二元性在脉动变量演化中的作用至关重要。
{"title":"Rare find: Discovery and chemo-dynamical properties of two s-process-enhanced RR Lyrae stars","authors":"V. D’Orazi, G. Iorio, B. Cseh, C. Sneden, H. Abdollahi, L. Molnár, A. Bobrick, G. Bono, V. F. Braga, A. Karakas, M. Lugaro, S. W. Campbell, M. Fabrizio, G. Fiorentino, I. U. Roederer, N. Storm, M. Tantalo, J. Crestani","doi":"10.1051/0004-6361/202557188","DOIUrl":"https://doi.org/10.1051/0004-6361/202557188","url":null,"abstract":"<i>Aims.<i/> We report the serendipitous discovery of two RR Lyrae stars that exhibit significant s-process element enrichment, a rare class previously represented solely by TY Gruis. Our goal is to characterise these objects chemically and dynamically, and explore their origins and evolutionary histories.<i>Methods.<i/> Using high-resolution spectroscopy from HERMES@AAT and UVES@VLT, we derived detailed chemical abundances of key s-process elements (Y, Ba, La, Ce, Nd, and Eu) and carbon, along with <i>α<i/> elements (Ca, Mg, and Ti). We also employed Gaia Data Release 3 astrometric data to analyse their kinematics, orbital properties, and classify their Galactic population membership. We compared observational results with theoretical asymptotic giant branch (AGB) nucleosynthesis models to interpret their enrichment patterns.<i>Results.<i/> Both stars exhibit clear signatures of s-process enrichment, with significant overabundances in second-peak elements such as Ba and La compared to first-peak Y and Zr. Comparison with AGB nucleosynthesis models suggests their progenitors experienced pollution of s-process-rich material, consistent with early binary interactions. However, notable discrepancies in dilution factors highlight the need for more refined low-metallicity AGB models. We also explore and discuss alternative scenarios, including sub-luminous post-AGB-like evolution or double episodes of mass transfer. In the latter case, the star initially undergoes a mass transfer when it is on the main sequence, accreting material from a former AGB companion. Subsequently, as the star evolves along the red giant branch, it may again transfer mass to its companion before becoming an RR Lyrae star.<i>Conclusions.<i/> Our findings confirm the existence of s-process-enhanced RR Lyrae stars and demonstrate the importance of combining chemical and dynamical diagnostics to unveil their complex evolutionary pathways. Future detailed binary evolution modelling and long-term orbital monitoring are essential to resolve their formation scenarios and assess the role of binarity in the evolution of pulsating variables.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"145 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145609714","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}
Pub Date : 2025-11-26DOI: 10.1051/0004-6361/202556257
Valentina Vaulato, Melissa J. Hobson, Romain Allart, Stefan Pelletier, Joost P. Wardenier, Hritam Chakraborty, David Ehrenreich, Nicola Nari, Michal Steiner, Xavier Dumusque, H. Jens Hoeijmakers, Étienne Artigau, Frédérique Baron, Susana C. C. Barros, Björn Benneke, Xavier Bonfils, François Bouchy, Marta Bryan, Bruno L. Canto Martins, Ryan Cloutier, Neil J. Cook, Nicolas B. Cowan, Jose Renan De Medeiros, Xavier Delfosse, Elisa Delgado-Mena, René Doyon, Jonay I. González Hernández, David Lafrenière, Izan de Castro Leão, Christophe Lovis, Lison Malo, Claudio Melo, Lucile Mignon, Christoph Mordasini, Francesco Pepe, Rafael Rebolo, Jason Rowe, Nuno C. Santos, Damien Ségransan, Alejandro Suárez Mascareño, Stéphane Udry, Diana Valencia, Gregg Wade, José L. A. Aguiar, Khaled Al Moulla, Babatunde Akinsanmi, Nicholas W. Borsato, Charles Cadieux, Yann Carteret, Ana Rita Costa Silva, Eduardo A. S. Cristo, Thierry Forveille, Yolanda G. C. Frensch, Nicole Gromek, Monika Lendl, Bibiana Prinoth, Angelica Psaridi, Atanas K. Stefanov, Brian Thorsbro, Drew Weisserman
Ultra-hot gas giants such as WASP-121b provide unique laboratories for exploring atmospheric chemistry and dynamics under extreme irradiation conditions. Uncovering their chemical composition and atmospheric circulation is critical for tracing planet formation pathways. Here, we present a comprehensive atmospheric characterisation of WASP-121b using high-resolution transit spectroscopy across the optical to infrared with HARPS, NIRPS, and CRIRES+ spanning nine transit events. These observations are complemented with five TESS photometric sectors, two EulerCam light curves simultaneous to the HARPS and NIRPS transits, and an extensive radial velocity dataset in order to refine WASP-121b's orbital parameters. A cross-correlation analysis detected iron (Fe), carbon monoxide (CO) and vanadium (V) absorption signals with SNR of 5.8, 5.0, and 4.7, respectively. Our retrieval analysis constrains the water (H2O) abundance to −6.52−0.68+0.49 dex, although its absorption signal is effectively muted by the hydride (H−) continuum. We constrained the relative abundances of the volatile and refractory elements - which represents a crucial diagnostic of atmospheric chemistry, evolution, and planet formation pathways. The retrieved abundance ratios are broadly consistent with expected values of a solar composition atmosphere in chemical equilibrium, likely indicating minimal disequilibrium chemistry alterations at the probed pressures (∼10−4−10−3 bar). We update the orbital parameters of WASP-121b with its largest radial velocity dataset to date. By comparing orbital velocities derived from both the radial velocity analysis and the atmospheric retrieval, we determined a non-zero velocity offset caused by atmospheric circulation, ΔKp = −15 ± 3 km s−1 (assuming M⋆ = 1.38 ± 0.02 M⊙), consistent with predictions from either drag-free or weak-drag 3D global circulation models, while we caution the non-negligible dependence on the assumed stellar mass. These results place new constraints on the thermal structure, dynamics, and chemical inventory of WASP-121b, highlighting the power of multi-wavelength high-resolution spectroscopy to probe exoplanetary atmospheres.
像WASP-121b这样的超高温气体巨行星为探索极端辐射条件下的大气化学和动力学提供了独特的实验室。揭示它们的化学成分和大气环流对于追踪行星的形成路径至关重要。在这里，我们使用高分辨率的透射光谱，包括HARPS， NIRPS和CRIRES+，跨越9个过境事件，在光学到红外波段对WASP-121b进行了全面的大气表征。这些观测得到了5个TESS光度区、2个与HARPS和NIRPS同步的EulerCam光曲线以及一个广泛的径向速度数据集的补充，以完善WASP-121b的轨道参数。互相关分析检测到铁（Fe）、一氧化碳（CO）和钒(V)的吸收信号，信噪比分别为5.8、5.0和4.7。我们的检索分析限制了水（H2O）丰度为- 6.52 - 0.68+0.49指数，尽管它的吸收信号被氢化物（H -）连续体有效地抑制了。我们限制了挥发性和难熔性元素的相对丰度——这代表了大气化学、演化和行星形成途径的关键诊断。得到的丰度比与化学平衡状态下太阳成分大气的期望值大致一致，可能表明在探测压力（~ 10−4−10−3 bar）下，不平衡化学变化最小。我们用迄今为止最大的径向速度数据更新了WASP-121b的轨道参数。通过比较径向速度分析和大气反演得到的轨道速度，我们确定了由大气环流引起的非零速度偏移，ΔKp = - 15±3 km s - 1（假设M - - = 1.38±0.02 M⊙），与无阻力或弱阻力3D全球环流模型的预测一致，同时我们提醒不可忽略的依赖于假设的恒星质量。这些结果对WASP-121b的热结构、动力学和化学成分提出了新的限制，突出了多波长高分辨率光谱探测系外行星大气的能力。
{"title":"Atmospheric composition and circulation of the ultra-hot Jupiter WASP-121b with joint NIRPS, HARPS and CRIRES+ transit spectroscopy","authors":"Valentina Vaulato, Melissa J. Hobson, Romain Allart, Stefan Pelletier, Joost P. Wardenier, Hritam Chakraborty, David Ehrenreich, Nicola Nari, Michal Steiner, Xavier Dumusque, H. Jens Hoeijmakers, Étienne Artigau, Frédérique Baron, Susana C. C. Barros, Björn Benneke, Xavier Bonfils, François Bouchy, Marta Bryan, Bruno L. Canto Martins, Ryan Cloutier, Neil J. Cook, Nicolas B. Cowan, Jose Renan De Medeiros, Xavier Delfosse, Elisa Delgado-Mena, René Doyon, Jonay I. González Hernández, David Lafrenière, Izan de Castro Leão, Christophe Lovis, Lison Malo, Claudio Melo, Lucile Mignon, Christoph Mordasini, Francesco Pepe, Rafael Rebolo, Jason Rowe, Nuno C. Santos, Damien Ségransan, Alejandro Suárez Mascareño, Stéphane Udry, Diana Valencia, Gregg Wade, José L. A. Aguiar, Khaled Al Moulla, Babatunde Akinsanmi, Nicholas W. Borsato, Charles Cadieux, Yann Carteret, Ana Rita Costa Silva, Eduardo A. S. Cristo, Thierry Forveille, Yolanda G. C. Frensch, Nicole Gromek, Monika Lendl, Bibiana Prinoth, Angelica Psaridi, Atanas K. Stefanov, Brian Thorsbro, Drew Weisserman","doi":"10.1051/0004-6361/202556257","DOIUrl":"https://doi.org/10.1051/0004-6361/202556257","url":null,"abstract":"Ultra-hot gas giants such as WASP-121b provide unique laboratories for exploring atmospheric chemistry and dynamics under extreme irradiation conditions. Uncovering their chemical composition and atmospheric circulation is critical for tracing planet formation pathways. Here, we present a comprehensive atmospheric characterisation of WASP-121b using high-resolution transit spectroscopy across the optical to infrared with HARPS, NIRPS, and CRIRES+ spanning nine transit events. These observations are complemented with five TESS photometric sectors, two EulerCam light curves simultaneous to the HARPS and NIRPS transits, and an extensive radial velocity dataset in order to refine WASP-121b's orbital parameters. A cross-correlation analysis detected iron (Fe), carbon monoxide (CO) and vanadium (V) absorption signals with SNR of 5.8, 5.0, and 4.7, respectively. Our retrieval analysis constrains the water (H<sub>2<sub/>O) abundance to −6.52<sub>−0.68<sub/><sup>+0.49<sup/> dex, although its absorption signal is effectively muted by the hydride (H<sup>−<sup/>) continuum. We constrained the relative abundances of the volatile and refractory elements - which represents a crucial diagnostic of atmospheric chemistry, evolution, and planet formation pathways. The retrieved abundance ratios are broadly consistent with expected values of a solar composition atmosphere in chemical equilibrium, likely indicating minimal disequilibrium chemistry alterations at the probed pressures (∼10<sup>−4<sup/>−10<sup>−3<sup/> bar). We update the orbital parameters of WASP-121b with its largest radial velocity dataset to date. By comparing orbital velocities derived from both the radial velocity analysis and the atmospheric retrieval, we determined a non-zero velocity offset caused by atmospheric circulation, ΔK<sub>p<sub/> = −15 ± 3 km s<sup>−1<sup/> (assuming M<sub>⋆<sub/> = 1.38 ± 0.02 M<sub>⊙<sub/>), consistent with predictions from either drag-free or weak-drag 3D global circulation models, while we caution the non-negligible dependence on the assumed stellar mass. These results place new constraints on the thermal structure, dynamics, and chemical inventory of WASP-121b, highlighting the power of multi-wavelength high-resolution spectroscopy to probe exoplanetary atmospheres.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"23 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145609690","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}
Pub Date : 2025-11-26DOI: 10.1051/0004-6361/202555038
M. Kunert-Bajraszewska, D. Kozieł-Wierzbowska, D. Stern, A. Krauze, N. Zafar, T. Connor, M. J. Graham
We present the optical and infrared properties of a sample of 24 radio transient sources discovered in the Very Large Array Sky Survey (VLASS). Previous studies of their radio emission showed that these sources resemble young gigahertz-peaked spectrum (GPS) radio sources, but they are less powerful and characterized by low-power jets. The bursts of radio activity in most cases are likely due to intrinsic changes in the accretion processes. However, for a few sources in this sample, we cannot rule out the possibility that their radio variability results from a tidal disruption event (TDE). In this work, we extended our analysis to the optical and infrared regimes, confirming that our sample of radio transients is not homogeneous in terms of their optical and infrared properties either. The host galaxies of most of these sources are massive ellipticals with emission dominated by active galactic nuclei (AGNs). They host supermassive black holes (SMBHs) with masses typical of radio-loud AGNs (> 107 M⊙), but they exhibit very low accretion activity. In contrast, the sources for which a TDE origin is suspected are either pure star-forming galaxies or show significant ongoing star formation, similar to radio-selected, optically detected TDEs. Additionally, two of them exhibit infrared flares characteristic of TDEs, while the remaining sources do not display significant variability outside the radio regime. Moreover, the evolution of their radio brightness in the W3−radio diagnostic diagram – which we employed in our analysis – also sets our TDE candidates apart from the rest of the sample and resembles the radio variability seen in optically discovered TDEs with radio emission. Finally, based on our findings, we hypothesize that the W3−radio relation can serve as a tool to distinguish between radio transients caused by TDEs and those originating from intrinsic AGN variability.
{"title":"Identifying tidal disruption events among radio transient galaxies","authors":"M. Kunert-Bajraszewska, D. Kozieł-Wierzbowska, D. Stern, A. Krauze, N. Zafar, T. Connor, M. J. Graham","doi":"10.1051/0004-6361/202555038","DOIUrl":"https://doi.org/10.1051/0004-6361/202555038","url":null,"abstract":"We present the optical and infrared properties of a sample of 24 radio transient sources discovered in the Very Large Array Sky Survey (VLASS). Previous studies of their radio emission showed that these sources resemble young gigahertz-peaked spectrum (GPS) radio sources, but they are less powerful and characterized by low-power jets. The bursts of radio activity in most cases are likely due to intrinsic changes in the accretion processes. However, for a few sources in this sample, we cannot rule out the possibility that their radio variability results from a tidal disruption event (TDE). In this work, we extended our analysis to the optical and infrared regimes, confirming that our sample of radio transients is not homogeneous in terms of their optical and infrared properties either. The host galaxies of most of these sources are massive ellipticals with emission dominated by active galactic nuclei (AGNs). They host supermassive black holes (SMBHs) with masses typical of radio-loud AGNs (> 10<sup>7<sup/> M<sub>⊙<sub/>), but they exhibit very low accretion activity. In contrast, the sources for which a TDE origin is suspected are either pure star-forming galaxies or show significant ongoing star formation, similar to radio-selected, optically detected TDEs. Additionally, two of them exhibit infrared flares characteristic of TDEs, while the remaining sources do not display significant variability outside the radio regime. Moreover, the evolution of their radio brightness in the W3−radio diagnostic diagram – which we employed in our analysis – also sets our TDE candidates apart from the rest of the sample and resembles the radio variability seen in optically discovered TDEs with radio emission. Finally, based on our findings, we hypothesize that the W3−radio relation can serve as a tool to distinguish between radio transients caused by TDEs and those originating from intrinsic AGN variability.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"110 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145609691","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}
Pub Date : 2025-11-26DOI: 10.1051/0004-6361/202556029
A. de Dios-Cubillas, O. Prieto-Ballesteros, I. López, M. Fernández-Sampedro, F. Rull, L. J. Bonales
Carbonates have been identified on the surfaces of several ocean worlds, although their formation processes remain poorly understood and are currently the subject of debate. Theoretical models have suggested the presence of clathrate hydrates in the subsurface of these ocean worlds and their dissociation could not only trigger the formation of certain kinds of surface geological features, but also contribute to the precipitation of authigenic carbonates emplaced on them. These authigenic carbonates, when derived from clathrate hydrate dissociation, are known as clathrites, which, to date, have only been reported on Earth along continental margins where clathrate hydrate deposits are present. In this work, we investigated whether the hypothetical precipitation of planetary clathrites could occur through the reaction between carbon molecules released after clathrate hydrate dissociation and brines or cryomagmas. We reproduced experimentally the formation process of clathrites from CO2-clathrate hydrates, monitoring in situ formation with Raman spectroscopy, and additionally characterised the mineral products ex situ by X-ray diffraction and IR spectroscopy. Here we show that carbon can be transferred from the dissociated clathrate hydrate molecules to the forming carbonates under the temperature-pressure conditions of the subsurface of ocean worlds. These high-pressure experimental results demonstrate that clathrites can form under crustal conditions of ocean worlds and that a genesis linked to clathrate hydrates should be considered, if the occurrence of these phases in the subsurface cannot be ruled out.
{"title":"The formation of clathrites under planetary conditions of ocean worlds: The case of Ceres and implications for future missions","authors":"A. de Dios-Cubillas, O. Prieto-Ballesteros, I. López, M. Fernández-Sampedro, F. Rull, L. J. Bonales","doi":"10.1051/0004-6361/202556029","DOIUrl":"https://doi.org/10.1051/0004-6361/202556029","url":null,"abstract":"Carbonates have been identified on the surfaces of several ocean worlds, although their formation processes remain poorly understood and are currently the subject of debate. Theoretical models have suggested the presence of clathrate hydrates in the subsurface of these ocean worlds and their dissociation could not only trigger the formation of certain kinds of surface geological features, but also contribute to the precipitation of authigenic carbonates emplaced on them. These authigenic carbonates, when derived from clathrate hydrate dissociation, are known as clathrites, which, to date, have only been reported on Earth along continental margins where clathrate hydrate deposits are present. In this work, we investigated whether the hypothetical precipitation of planetary clathrites could occur through the reaction between carbon molecules released after clathrate hydrate dissociation and brines or cryomagmas. We reproduced experimentally the formation process of clathrites from CO<sub>2<sub/>-clathrate hydrates, monitoring in situ formation with Raman spectroscopy, and additionally characterised the mineral products ex situ by X-ray diffraction and IR spectroscopy. Here we show that carbon can be transferred from the dissociated clathrate hydrate molecules to the forming carbonates under the temperature-pressure conditions of the subsurface of ocean worlds. These high-pressure experimental results demonstrate that clathrites can form under crustal conditions of ocean worlds and that a genesis linked to clathrate hydrates should be considered, if the occurrence of these phases in the subsurface cannot be ruled out.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"21 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145609715","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}
Pub Date : 2025-11-26DOI: 10.1051/0004-6361/202555872
Zhu-Ling Deng, Xiang-Dong Li, Yong Shao, Ying-Han Mao, Long Jiang
Context. PSR J1928+1815, the first recycled pulsar-helium (He) star binary discovered by the Five-hundred-meter Aperture Spherical radio Telescope, consists of a 10.55 ms pulsar and a companion star with mass 1 − 1.6 M⊙ in a 0.15-day orbit. Theoretical studies suggest that this system originated from a neutron star (NS) intermediate-mass or high-mass X-ray binary that underwent common envelope (CE) evolution, leading to the successful ejection of the giant envelope. The traditional view is that hypercritical accretion during the CE phase may have recycled the NS. However, the specific mechanism responsible for accelerating its spin period remains uncertain due to the complex processes involved in CE evolution.Aims. In this study, we investigate the influence of Roche lobe overflow (RLO) accretion that takes place prior to the CE phase on the spin evolution of NSs. Our primary objective is to clarify how this process affects the spin characteristics of pulsars.Methods. We utilized the stellar evolution code MESA and the binary population synthesis code BSE to model the formation and evolution of NS-He star binaries. We calculated the distributions of the orbital period, He star mass, NS spin period, and magnetic field for NS + He star systems in the Galaxy.Results. Our results indicate that RLO accretion preceding the CE phase could spin up NSs to millisecond periods through super-Eddington accretion. Considering a range of CE efficiencies αCE from 0.3 to 3, we estimate the birthrate (total number) of NS + He star systems in our Galaxy to be 9.0 × 10−5 yr−1 (626 systems) to 1.9 × 10−4 yr−1 (2684 systems).
{"title":"Formation of millisecond pulsar-helium star binaries","authors":"Zhu-Ling Deng, Xiang-Dong Li, Yong Shao, Ying-Han Mao, Long Jiang","doi":"10.1051/0004-6361/202555872","DOIUrl":"https://doi.org/10.1051/0004-6361/202555872","url":null,"abstract":"<i>Context.<i/> PSR J1928+1815, the first recycled pulsar-helium (He) star binary discovered by the Five-hundred-meter Aperture Spherical radio Telescope, consists of a 10.55 ms pulsar and a companion star with mass 1 − 1.6 <i>M<i/><sub>⊙<sub/> in a 0.15-day orbit. Theoretical studies suggest that this system originated from a neutron star (NS) intermediate-mass or high-mass X-ray binary that underwent common envelope (CE) evolution, leading to the successful ejection of the giant envelope. The traditional view is that hypercritical accretion during the CE phase may have recycled the NS. However, the specific mechanism responsible for accelerating its spin period remains uncertain due to the complex processes involved in CE evolution.<i>Aims.<i/> In this study, we investigate the influence of Roche lobe overflow (RLO) accretion that takes place prior to the CE phase on the spin evolution of NSs. Our primary objective is to clarify how this process affects the spin characteristics of pulsars.<i>Methods.<i/> We utilized the stellar evolution code MESA and the binary population synthesis code BSE to model the formation and evolution of NS-He star binaries. We calculated the distributions of the orbital period, He star mass, NS spin period, and magnetic field for NS + He star systems in the Galaxy.<i>Results.<i/> Our results indicate that RLO accretion preceding the CE phase could spin up NSs to millisecond periods through super-Eddington accretion. Considering a range of CE efficiencies <i>α<i/><sub>CE<sub/> from 0.3 to 3, we estimate the birthrate (total number) of NS + He star systems in our Galaxy to be 9.0 × 10<sup>−5<sup/> yr<sup>−1<sup/> (626 systems) to 1.9 × 10<sup>−4<sup/> yr<sup>−1<sup/> (2684 systems).","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"102 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145609717","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}
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