Pub Date : 2025-12-03DOI: 10.1051/0004-6361/202556644
Varpu Ahlberg, Anastasiia Bocharova, Alexandra Veledina
Context. Cygnus X-3 is the only known Galactic high-mass X-ray binary with a Wolf-Rayet companion. Recent X-ray polarimetry results with the Imaging X-ray Polarimetry Explorer have revealed it is a concealed ultraluminous X-ray source. It is also the first source for which pronounced orbital variability of X-ray polarization has been detected, notably with only one polarization maximum per orbit.Aims. Polarization caused by scattering of the source X-rays can only be orbitally variable if the scattering angles change throughout the orbit. Since this requires an asymmetrically distributed medium around the compact object, the observed variability traces the intrabinary structures. The single-peaked profile further imposes constraints on the possible geometry of the surrounding medium. Therefore, the X-ray polarization of Cygnus X-3 offers an opportunity to study the wind structures of high-mass X-ray binaries in detail. We aim to uncover the underlying geometry through analytical modeling of the variable polarization. Knowledge of these structures could be extended to other sources with similar wind-binary interactions.Methods. We studied the variability caused by single scattering in the intrabinary bow shock, exploring both the optically thin and optically thick limits. We considered two geometries for the reflecting medium: the axisymmetric parabolic bow shock and the parabolic cylinder shock. Finally, we determined which geometry offers the best match to the X-ray polarimetric data.Results. Qualitatively, we find that the peculiar properties of the data can only be replicated with a cylindrical bow shock with asymmetry across the shock centerline and significant optical depth. This geometry is comparable to shocks formed by the jet-wind or outflow-wind interactions. In addition, the orbital axis is slightly misaligned from the observed orientation of the radio jet in all our model fits.
{"title":"The constraining power of X-ray polarimetry: Detailed structure of the intrabinary bow shock in Cygnus X-3","authors":"Varpu Ahlberg, Anastasiia Bocharova, Alexandra Veledina","doi":"10.1051/0004-6361/202556644","DOIUrl":"https://doi.org/10.1051/0004-6361/202556644","url":null,"abstract":"<i>Context.<i/> Cygnus X-3 is the only known Galactic high-mass X-ray binary with a Wolf-Rayet companion. Recent X-ray polarimetry results with the Imaging X-ray Polarimetry Explorer have revealed it is a concealed ultraluminous X-ray source. It is also the first source for which pronounced orbital variability of X-ray polarization has been detected, notably with only one polarization maximum per orbit.<i>Aims.<i/> Polarization caused by scattering of the source X-rays can only be orbitally variable if the scattering angles change throughout the orbit. Since this requires an asymmetrically distributed medium around the compact object, the observed variability traces the intrabinary structures. The single-peaked profile further imposes constraints on the possible geometry of the surrounding medium. Therefore, the X-ray polarization of Cygnus X-3 offers an opportunity to study the wind structures of high-mass X-ray binaries in detail. We aim to uncover the underlying geometry through analytical modeling of the variable polarization. Knowledge of these structures could be extended to other sources with similar wind-binary interactions.<i>Methods.<i/> We studied the variability caused by single scattering in the intrabinary bow shock, exploring both the optically thin and optically thick limits. We considered two geometries for the reflecting medium: the axisymmetric parabolic bow shock and the parabolic cylinder shock. Finally, we determined which geometry offers the best match to the X-ray polarimetric data.<i>Results.<i/> Qualitatively, we find that the peculiar properties of the data can only be replicated with a cylindrical bow shock with asymmetry across the shock centerline and significant optical depth. This geometry is comparable to shocks formed by the jet-wind or outflow-wind interactions. In addition, the orbital axis is slightly misaligned from the observed orientation of the radio jet in all our model fits.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"137 1","pages":"A127"},"PeriodicalIF":6.5,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697224","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 : 2025-12-03DOI: 10.1051/0004-6361/202556438
J. M. Boxelaar, F. De Gasperin, M. J. Hardcastle, J. H. Croston, L. K. Morabito, R. J. van Weeren, H. Edler
Context. The Low Frequency Array (LOFAR) is uniquely able to perform deep, 15" resolution imaging at frequencies below 100 MHz. Observations in this regime, using the Low Band Antenna (LBA) system, are significantly affected by instrumental and ionospheric distortions. Recent developments in calibration techniques have enabled the routine production of high-fidelity images at these challenging frequencies.Aims. The aim of this study was to obtain images of the radio sources included in the Third Cambridge catalog, second revised version (3CRR), at an observing frequency of 58 MHz, with an angular resolution of 15" and sensitivity to both compact and diffuse radio emission. This work also aimed to produce accurate flux measurements for all sources. This dataset is designed to serve as a reference for low-frequency radio galaxy studies and future spectral aging analyses.Methods. We present the data reduction and calibration procedures developed for narrowband observations of bright sources with the LOFAR LBA. These include tailored direction-independent calibration strategies optimized for mitigating ionospheric phase corruptions and instrumental effects at 58 MHz. Imaging techniques were refined to reliably recover both small- and large-scale radio structures reliably.Results. We deliver 58 MHz radio images that include flux density measurements for the complete 3CRR sample. We determine that the LBA has an accurate flux density scale with an average flux uncertainty of 10%. This is an important confirmation for any future works using the LOFAR LBA system. With these results, we characterized the bright radio galaxy population with new high-resolution low-frequency images. We also provide high-resolution models of these sources, which will be useful for calibrating future surveys.Conclusions. This legacy survey significantly expands the available high-resolution data at low frequencies and is the first fully imaged high-resolution sample at ultra-low frequencies (<100 MHz). It lays the foundation for future studies of radio galaxy physics, low-energy cosmic-ray populations, and the interplay between radio jets and their environments.
{"title":"LOFAR 58 MHz Legacy Survey of the 3CRR catalog","authors":"J. M. Boxelaar, F. De Gasperin, M. J. Hardcastle, J. H. Croston, L. K. Morabito, R. J. van Weeren, H. Edler","doi":"10.1051/0004-6361/202556438","DOIUrl":"https://doi.org/10.1051/0004-6361/202556438","url":null,"abstract":"<i>Context<i/>. The Low Frequency Array (LOFAR) is uniquely able to perform deep, 15\" resolution imaging at frequencies below 100 MHz. Observations in this regime, using the Low Band Antenna (LBA) system, are significantly affected by instrumental and ionospheric distortions. Recent developments in calibration techniques have enabled the routine production of high-fidelity images at these challenging frequencies.<i>Aims<i/>. The aim of this study was to obtain images of the radio sources included in the Third Cambridge catalog, second revised version (3CRR), at an observing frequency of 58 MHz, with an angular resolution of 15\" and sensitivity to both compact and diffuse radio emission. This work also aimed to produce accurate flux measurements for all sources. This dataset is designed to serve as a reference for low-frequency radio galaxy studies and future spectral aging analyses.<i>Methods<i/>. We present the data reduction and calibration procedures developed for narrowband observations of bright sources with the LOFAR LBA. These include tailored direction-independent calibration strategies optimized for mitigating ionospheric phase corruptions and instrumental effects at 58 MHz. Imaging techniques were refined to reliably recover both small- and large-scale radio structures reliably.<i>Results<i/>. We deliver 58 MHz radio images that include flux density measurements for the complete 3CRR sample. We determine that the LBA has an accurate flux density scale with an average flux uncertainty of 10%. This is an important confirmation for any future works using the LOFAR LBA system. With these results, we characterized the bright radio galaxy population with new high-resolution low-frequency images. We also provide high-resolution models of these sources, which will be useful for calibrating future surveys.<i>Conclusions<i/>. This legacy survey significantly expands the available high-resolution data at low frequencies and is the first fully imaged high-resolution sample at ultra-low frequencies (<100 MHz). It lays the foundation for future studies of radio galaxy physics, low-energy cosmic-ray populations, and the interplay between radio jets and their environments.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"30 1","pages":"A65"},"PeriodicalIF":6.5,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697225","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 : 2025-12-03DOI: 10.1051/0004-6361/202556618
B. Thorsbro, S. Khalidy, R. M. Rich, M. Schultheis, D. Taniguchi, A. M. Amarsi, G. Kordopatis, G. Nandakumar, S. Nishiyama, N. Ryde
Context. The chemical abundances of alpha elements in Galactic Centre (GC) supergiants provide key insights into the chemical enrichment and star formation history of the Milky Way’s nuclear star cluster. Previous studies have reported enhanced alpha-element abundances, which raises questions about the chemical evolution of this unique region.Aims. We aim to reassess the alpha-element abundances in the GC supergiant GCIRS 22 using updated spectral modelling and non-local thermodynamic equilibrium (NLTE) corrections to resolve discrepancies from earlier abundance analyses.Methods. We analysed high-resolution near-infrared spectra of GCIRS 22 using contemporary line lists and precise stellar parameters derived from scandium line diagnostics. We applied comprehensive NLTE corrections to accurately determine the abundances of silicon and calcium.Results. Our analysis reveals solar-scale alpha abundances ([Ca/Fe] = 0.06 ± 0.07; [Si/Fe] = than −0.08 ± 0.20) for GCIRS 22, which are significantly lower than previous local thermodynamic equilibrium (LTE) based findings. NLTE corrections reduce the calcium abundance by approximately 0.3 dex compared to LTE estimates; this aligns our results with recent studies and highlights the importance of accurate NLTE modelling.Conclusions. The solar-scale alpha-element abundances observed in GCIRS 22 suggest that recent star formation in the region has not been dominated by Type II supernovae, such as those expected from a recent starburst. Our findings support a scenario of episodic star formation, characterized by intermittent bursts separated by extended quiescent phases, or potentially driven by gas inflows from the inner disc, funnelled by the Galactic bar. Future comprehensive NLTE studies of additional GC stars will be essential for refining our understanding of the region’s chemical evolution and star formation history.
{"title":"Supergiant GCIRS 22 in the Milky Way nuclear star cluster: Revised alpha abundances","authors":"B. Thorsbro, S. Khalidy, R. M. Rich, M. Schultheis, D. Taniguchi, A. M. Amarsi, G. Kordopatis, G. Nandakumar, S. Nishiyama, N. Ryde","doi":"10.1051/0004-6361/202556618","DOIUrl":"https://doi.org/10.1051/0004-6361/202556618","url":null,"abstract":"<i>Context<i/>. The chemical abundances of alpha elements in Galactic Centre (GC) supergiants provide key insights into the chemical enrichment and star formation history of the Milky Way’s nuclear star cluster. Previous studies have reported enhanced alpha-element abundances, which raises questions about the chemical evolution of this unique region.<i>Aims<i/>. We aim to reassess the alpha-element abundances in the GC supergiant GCIRS 22 using updated spectral modelling and non-local thermodynamic equilibrium (NLTE) corrections to resolve discrepancies from earlier abundance analyses.<i>Methods<i/>. We analysed high-resolution near-infrared spectra of GCIRS 22 using contemporary line lists and precise stellar parameters derived from scandium line diagnostics. We applied comprehensive NLTE corrections to accurately determine the abundances of silicon and calcium.<i>Results<i/>. Our analysis reveals solar-scale alpha abundances ([Ca/Fe] = 0.06 ± 0.07; [Si/Fe] = than −0.08 ± 0.20) for GCIRS 22, which are significantly lower than previous local thermodynamic equilibrium (LTE) based findings. NLTE corrections reduce the calcium abundance by approximately 0.3 dex compared to LTE estimates; this aligns our results with recent studies and highlights the importance of accurate NLTE modelling.<i>Conclusions<i/>. The solar-scale alpha-element abundances observed in GCIRS 22 suggest that recent star formation in the region has not been dominated by Type II supernovae, such as those expected from a recent starburst. Our findings support a scenario of episodic star formation, characterized by intermittent bursts separated by extended quiescent phases, or potentially driven by gas inflows from the inner disc, funnelled by the Galactic bar. Future comprehensive NLTE studies of additional GC stars will be essential for refining our understanding of the region’s chemical evolution and star formation history.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"4 1","pages":"A62"},"PeriodicalIF":6.5,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697227","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 : 2025-12-03DOI: 10.1051/0004-6361/202556012
A. D. Nekrasov, T. Dauser, J. A. García, D. J. Walton, C. M. Fromm, A. J. Young, F. J. E. Baker, A. M. Joyce, O. König, S. Licklederer, J. Häfner, J. Wilms
Context. The reflection of X-rays at the inner accretion disk around black holes imprints relativistically broadened features in the observed spectrum. Aside from the black hole properties and the ionization and density of the accretion disk, these features also depend on the location and geometry of the primary source of X-rays, often referred to as the corona.Aims. We present a fast general relativistic model for spectral fitting of a radially extended, ring-like corona above the accretion disk.Methods. A common approach used to explain observed X-ray reflection spectra is the lamp post geometry, which assumes a point-like source on the rotational axis of the black hole. While it is typically able to explain the observations, this geometric model does not allow for any constraint to be placed on the radial size of the corona. We therefore extended the publicly available relativistic reflection model RELXILL by implementing a radially extended, ring-like primary source.Results. With the new RELXILL model allowing us to vary the position of the primary source in two dimensions, we present simulated line profiles and spectra and discuss the implications of carrying out a data fitting, in comparison to the lamp post model. We applied this extended RELXILL model to XMM-Newton and NuSTAR data of the radio-quiet Seyfert-2 active galactic nucleus (AGN) ESO 033-G002. The new model describes the data well and we are able to constrain the distance of the source to the black hole to be less than three gravitational radii, while the angular position of the source is poorly constrained.Conclusions. We show that a compact, radially extended corona close to the innermost stable circular orbit is able to explain the observed relativistic reflection as well as the lamp post corona does. This model has been made freely available to the community.
{"title":"Relativistic reflection within an extended hot plasma geometry","authors":"A. D. Nekrasov, T. Dauser, J. A. García, D. J. Walton, C. M. Fromm, A. J. Young, F. J. E. Baker, A. M. Joyce, O. König, S. Licklederer, J. Häfner, J. Wilms","doi":"10.1051/0004-6361/202556012","DOIUrl":"https://doi.org/10.1051/0004-6361/202556012","url":null,"abstract":"<i>Context.<i/> The reflection of X-rays at the inner accretion disk around black holes imprints relativistically broadened features in the observed spectrum. Aside from the black hole properties and the ionization and density of the accretion disk, these features also depend on the location and geometry of the primary source of X-rays, often referred to as the corona.<i>Aims.<i/> We present a fast general relativistic model for spectral fitting of a radially extended, ring-like corona above the accretion disk.<i>Methods.<i/> A common approach used to explain observed X-ray reflection spectra is the lamp post geometry, which assumes a point-like source on the rotational axis of the black hole. While it is typically able to explain the observations, this geometric model does not allow for any constraint to be placed on the radial size of the corona. We therefore extended the publicly available relativistic reflection model RELXILL by implementing a radially extended, ring-like primary source.<i>Results.<i/> With the new RELXILL model allowing us to vary the position of the primary source in two dimensions, we present simulated line profiles and spectra and discuss the implications of carrying out a data fitting, in comparison to the lamp post model. We applied this extended RELXILL model to <i>XMM-Newton<i/> and <i>NuSTAR<i/> data of the radio-quiet Seyfert-2 active galactic nucleus (AGN) ESO 033-G002. The new model describes the data well and we are able to constrain the distance of the source to the black hole to be less than three gravitational radii, while the angular position of the source is poorly constrained.<i>Conclusions.<i/> We show that a compact, radially extended corona close to the innermost stable circular orbit is able to explain the observed relativistic reflection as well as the lamp post corona does. This model has been made freely available to the community.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"32 1","pages":"A129"},"PeriodicalIF":6.5,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697209","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 : 2025-12-03DOI: 10.1051/0004-6361/202556497
Vincent Piétu, Roberto García, Dominique Broguière, Michael Bremer, Jan Wagner, Emmanuel Obermeyer, Rémi Sassella, Olivier Gentaz
Aims. With its large collecting area, the NOrthern Extended Millimeter Array (NOEMA) is a prime candidate for a highly sensitive very long baseline interferometry (VLBI) station in the millimeter range. In this work, we describe the phasing system used for coherently adding the 12 antennas of the array.Methods. We developed and installed VLBI dedicated hardware and a new correlator firmware mode to achieve this goal. We also developed an active phasing software to compensate in real time for tropospheric phase variations across the array.Results. This phasing system enabled the NOEMA array to achieve a level of sensitivity equivalent to a ∼50 m single dish antenna. Since 2021, phased NOEMA has been participating regularly in VLBI observations as part of the existing millimeter VLBI networks: the Global Millimeter VLBI Array (GMVA) and the Event Horizon Telescope (EHT).
{"title":"The NOEMA phasing system","authors":"Vincent Piétu, Roberto García, Dominique Broguière, Michael Bremer, Jan Wagner, Emmanuel Obermeyer, Rémi Sassella, Olivier Gentaz","doi":"10.1051/0004-6361/202556497","DOIUrl":"https://doi.org/10.1051/0004-6361/202556497","url":null,"abstract":"<i>Aims<i/>. With its large collecting area, the NOrthern Extended Millimeter Array (NOEMA) is a prime candidate for a highly sensitive very long baseline interferometry (VLBI) station in the millimeter range. In this work, we describe the phasing system used for coherently adding the 12 antennas of the array.<i>Methods<i/>. We developed and installed VLBI dedicated hardware and a new correlator firmware mode to achieve this goal. We also developed an active phasing software to compensate in real time for tropospheric phase variations across the array.<i>Results<i/>. This phasing system enabled the NOEMA array to achieve a level of sensitivity equivalent to a ∼50 m single dish antenna. Since 2021, phased NOEMA has been participating regularly in VLBI observations as part of the existing millimeter VLBI networks: the Global Millimeter VLBI Array (GMVA) and the Event Horizon Telescope (EHT).","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"55 1","pages":"A86"},"PeriodicalIF":6.5,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697236","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 : 2025-12-03DOI: 10.1051/0004-6361/202556752
Petr Hellinger, Simone Landi
Aims. We investigated the properties of plasma turbulence at ion scales in the context of the solar wind. We concentrated on the pressure-strain coupling between the kinetic and magnetic energy and the internal energy; we analysed its capability to produce an effectively irreversible transfer towards the internal energy.Methods. We studied results from a three-dimensional hybrid simulation of decaying turbulence when protons exhibit a substantial temperature anisotropy. We analysed the time evolution and behaviour of the combined (magnetic plus kinetic) energy and its spectral properties. Using the Kármán-Howarth-Monin (KHM) formalism, we quantified the role of the dissipation via the resistive channel and that of the pressure-strain term in generating internal energy.Results. The combined energy flows from large to intermediate and small scales, where it is efficiently dissipated via the resistive term and is exchanged with the internal energy through the pressure-strain term. The pressure-strain coupling oscillates strongly, and this oscillation reflects its reversibility properties that are embedded in a secular evolution towards a global increase in the plasma internal energy. All the terms involved in the KHM energy balance equation are strongly anisotropic with respect to the mean magnetic field. They tend to be elongated along the mean magnetic field and oscillate over time at large scales, which is connected with the pressure-strain coupling. The reversible oscillatory part of the pressure-strain coupling is mostly contained in the gyrotropic pressure-strain part. This mainly affects the turbulent processes at large scales, but when it is time averaged, it also contributes to the ion energisation approximately at ion scales. The non-gyrotropic pressure-strain part does not oscillate significantly, acts at ion scales, and can be considered as the main effective dissipation channel.
{"title":"Pressure-strain interaction in plasma turbulence: Contribution of the ion non-gyrotropy","authors":"Petr Hellinger, Simone Landi","doi":"10.1051/0004-6361/202556752","DOIUrl":"https://doi.org/10.1051/0004-6361/202556752","url":null,"abstract":"<i>Aims.<i/> We investigated the properties of plasma turbulence at ion scales in the context of the solar wind. We concentrated on the pressure-strain coupling between the kinetic and magnetic energy and the internal energy; we analysed its capability to produce an effectively irreversible transfer towards the internal energy.<i>Methods.<i/> We studied results from a three-dimensional hybrid simulation of decaying turbulence when protons exhibit a substantial temperature anisotropy. We analysed the time evolution and behaviour of the combined (magnetic plus kinetic) energy and its spectral properties. Using the Kármán-Howarth-Monin (KHM) formalism, we quantified the role of the dissipation via the resistive channel and that of the pressure-strain term in generating internal energy.<i>Results.<i/> The combined energy flows from large to intermediate and small scales, where it is efficiently dissipated via the resistive term and is exchanged with the internal energy through the pressure-strain term. The pressure-strain coupling oscillates strongly, and this oscillation reflects its reversibility properties that are embedded in a secular evolution towards a global increase in the plasma internal energy. All the terms involved in the KHM energy balance equation are strongly anisotropic with respect to the mean magnetic field. They tend to be elongated along the mean magnetic field and oscillate over time at large scales, which is connected with the pressure-strain coupling. The reversible oscillatory part of the pressure-strain coupling is mostly contained in the gyrotropic pressure-strain part. This mainly affects the turbulent processes at large scales, but when it is time averaged, it also contributes to the ion energisation approximately at ion scales. The non-gyrotropic pressure-strain part does not oscillate significantly, acts at ion scales, and can be considered as the main effective dissipation channel.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"4 1","pages":"A131"},"PeriodicalIF":6.5,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697206","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 : 2025-12-03DOI: 10.1051/0004-6361/202557216
P. Redondo, C. Barrientos, M. Sanz-Novo, V. M. Rivilla
Context. The recent interstellar detection of the high-energy O-protonated carbonyl sulfide isomer (HOCS+) toward the molecular cloud G+0.693-0.027 contrasts with the non-detection of its lower-energy S-protonated counterpart, HSCO+, the global minimum in energy. This raises questions regarding the occurrence of selective formation pathways of these [H,C,S,O]+ isomers in space.Aims. In this work, we aim to explore the most likely gas-phase formation routes for both HOCS+ and HSCO+ beyond the direct protonation of OCS (i.e., HCS+ + OH, HCO+ + SH, HOC+ + SH, and HCO + SH+) to help rationalize previous observational results. Methods. We first explored the thermodynamic feasibility of the aforementioned reactions using high-level double-hybrid B2PLYPD3∕aug-cc-pVTZ and CCSD(T)-F12∕cc-pVTZ-F12 computations. For the reaction HCS+ + OH, found to be the most thermodynamically favorable, we characterized the stationary points on its corresponding potential energy surface (PES). In addition, we also used a composite approach to refine relative energies and employed the statistical rate theory and master equation simulations to estimate rate constants and branching ratios.Results. We show that HOCS+ is preferentially formed through the reaction of HCS+ with OH, providing a plausible chemical explanation for its interstellar presence and the non-detection of the low energy isomer. Nevertheless, while the branching ratio computed at a T ~Tkin(G+0.693) = 70-140 K is qualitatively consistent with the observations, its value is two orders of magnitude larger than the derived HOCS+/HSCO+ lower limit observational ratio (of ≥2.3). This suggests that if the upper limit of HSCO+ is close to the real abundance, additional formation pathways may also play a significant role in shaping the isomeric ratio.Conclusions. These results highlight that including all isomers in a given family, along with their isomer-preferential formation pathways, in astrochemical models, which are in many cases isomer-insensitive, is essential to understand their formation routes.
{"title":"Exploring chemical pathways for the interstellar molecule HOCS+: Preferential formation of the O-protonated carbonyl sulfide isomer","authors":"P. Redondo, C. Barrientos, M. Sanz-Novo, V. M. Rivilla","doi":"10.1051/0004-6361/202557216","DOIUrl":"https://doi.org/10.1051/0004-6361/202557216","url":null,"abstract":"<i>Context<i/>. The recent interstellar detection of the high-energy O-protonated carbonyl sulfide isomer (HOCS<sup>+<sup/>) toward the molecular cloud G+0.693-0.027 contrasts with the non-detection of its lower-energy S-protonated counterpart, HSCO<sup>+<sup/>, the global minimum in energy. This raises questions regarding the occurrence of selective formation pathways of these [H,C,S,O]<sup>+<sup/> isomers in space.<i>Aims<i/>. In this work, we aim to explore the most likely gas-phase formation routes for both HOCS<sup>+<sup/> and HSCO<sup>+<sup/> beyond the direct protonation of OCS (i.e., HCS<sup>+<sup/> + OH, HCO<sup>+<sup/> + SH, HOC<sup>+<sup/> + SH, and HCO + SH<sup>+<sup/>) to help rationalize previous observational results. <i>Methods<i/>. We first explored the thermodynamic feasibility of the aforementioned reactions using high-level double-hybrid B2PLYPD3∕aug-cc-pVTZ and CCSD(T)-F12∕cc-pVTZ-F12 computations. For the reaction HCS<sup>+<sup/> + OH, found to be the most thermodynamically favorable, we characterized the stationary points on its corresponding potential energy surface (PES). In addition, we also used a composite approach to refine relative energies and employed the statistical rate theory and master equation simulations to estimate rate constants and branching ratios.<i>Results<i/>. We show that HOCS<sup>+<sup/> is preferentially formed through the reaction of HCS<sup>+<sup/> with OH, providing a plausible chemical explanation for its interstellar presence and the non-detection of the low energy isomer. Nevertheless, while the branching ratio computed at a <i>T<i/> ~<i>T<i/><i><sub>kin<sub/><i/>(G+0.693) = 70-140 K is qualitatively consistent with the observations, its value is two orders of magnitude larger than the derived HOCS<sup>+<sup/>/HSCO<sup>+<sup/> lower limit observational ratio (of ≥2.3). This suggests that if the upper limit of HSCO<sup>+<sup/> is close to the real abundance, additional formation pathways may also play a significant role in shaping the isomeric ratio.<i>Conclusions<i/>. These results highlight that including all isomers in a given family, along with their isomer-preferential formation pathways, in astrochemical models, which are in many cases isomer-insensitive, is essential to understand their formation routes.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"30 1","pages":"A73"},"PeriodicalIF":6.5,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697276","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 : 2025-12-02DOI: 10.1051/0004-6361/202557356
Luca Barbieri, Pascal Démoulin
Context. The solar corona exhibits a striking temperature inversion, with plasma temperatures exceeding 106 K above a much cooler chromosphere. How the coronal plasma reaches such extreme temperatures remains a fundamental open question in solar and plasma physics, known as the coronal heating problem.Aims. We investigate whether localized heating events, spatially distributed across the upper chromosphere and base of the transition region, combined with a collisionless corona, can self-consistently generate realistic temperature and density profiles without requiring direct energy deposition within the corona itself.Models. We develop a 3D kinetic model of a collisionless stellar atmosphere embedded in a uniform magnetic field, where heating occurs intermittently at the chromosphere–transition region interface. A surface coarse-graining procedure is introduced to capture the spatial intermittency of heating, leading to non-thermal boundary conditions for the Vlasov equation. We derive analytical expressions for the stationary distribution functions and compute the corresponding macroscopic profiles.Results. We show that spatially intermittent heating, when coarse-grained over a surface containing many localized events, produces suprathermal particle distributions and a temperature inversion via velocity filtration. The resulting density and temperature profiles feature a transition region followed by a hot corona, provided that heating events are spatially sparse, consistently with solar observations. This result holds independently of the specific statistical distribution of temperature increments. Importantly, no local heating is applied within the corona.Conclusions. The model demonstrates that spatial intermittency alone, i.e. a sparse distribution of heated regions at the chromospheric interface, is sufficient to explain the formation of the transition region and the high-temperature corona.
{"title":"Kinetic collisionless model of the solar transition region and corona with spatially intermittent heating","authors":"Luca Barbieri, Pascal Démoulin","doi":"10.1051/0004-6361/202557356","DOIUrl":"https://doi.org/10.1051/0004-6361/202557356","url":null,"abstract":"<i>Context.<i/> The solar corona exhibits a striking temperature inversion, with plasma temperatures exceeding 10<sup>6<sup/> K above a much cooler chromosphere. How the coronal plasma reaches such extreme temperatures remains a fundamental open question in solar and plasma physics, known as the coronal heating problem.<i>Aims.<i/> We investigate whether localized heating events, spatially distributed across the upper chromosphere and base of the transition region, combined with a collisionless corona, can self-consistently generate realistic temperature and density profiles without requiring direct energy deposition within the corona itself.<i>Models.<i/> We develop a 3D kinetic model of a collisionless stellar atmosphere embedded in a uniform magnetic field, where heating occurs intermittently at the chromosphere–transition region interface. A surface coarse-graining procedure is introduced to capture the spatial intermittency of heating, leading to non-thermal boundary conditions for the Vlasov equation. We derive analytical expressions for the stationary distribution functions and compute the corresponding macroscopic profiles.<i>Results.<i/> We show that spatially intermittent heating, when coarse-grained over a surface containing many localized events, produces suprathermal particle distributions and a temperature inversion via velocity filtration. The resulting density and temperature profiles feature a transition region followed by a hot corona, provided that heating events are spatially sparse, consistently with solar observations. This result holds independently of the specific statistical distribution of temperature increments. Importantly, no local heating is applied within the corona.<i>Conclusions.<i/> The model demonstrates that spatial intermittency alone, i.e. a sparse distribution of heated regions at the chromospheric interface, is sufficient to explain the formation of the transition region and the high-temperature corona.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"11 1","pages":"A84"},"PeriodicalIF":6.5,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697211","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 : 2025-12-02DOI: 10.1051/0004-6361/202556304
Luc Dessart, Rubina Kotak, Wynn Jacobson-Galán, Kaustav Das, Christoffer Fremling, Mansi Kasliwal, Yu-Jing Qin, Sam Rose
We present 0.3–21 μm observations at ∼275 d and ∼400 d of type II supernova (SN) 2024ggi that combined ground-based optical and near-infrared data from the Keck I/II telescopes and space-based infrared data from the James Webb Space Telescope. Although the optical regions dominate the observed flux, SN 2024ggi is bright at infrared wavelengths (65% and 35% fall each side of 1 μm). SN 2024ggi exhibits a plethora of emission lines from H, He, intermediate-mass elements (O, Na, Mg, S, Ar, and Ca), and iron-group elements (IGEs; Fe, Co, and Ni). The width of all lines is essentially the same, which suggests efficient macroscopic chemical mixing of the inner ejecta at ≲2000 km s−1 and little mixing of 56Ni at higher velocities. Molecular emission in the infrared range is dominated by the CO fundamental, which radiates about 5% of the total SN luminosity. A molecule-free radiative-transfer model based on a standard explosion of a red supergiant star (i.e., ∼1051 erg, 0.06 M⊙ of 56Ni from a 15.2 M⊙ progenitor) yields a satisfactory match throughout the optical and infrared at both epochs. The SN 2024ggi CO luminosity is comparable to the fractional decay power absorbed in the model C/O-rich shell. An accounting for CO cooling would likely resolve the model overestimate of the [O I] 0.632 μm flux. The relative weakness of the molecular emission in SN 2024ggi and the good overall match obtained with our molecule-free model suggests negligible microscopic mixing; about 95% of the SN luminosity is radiated by atoms and ions. The lines from IGEs, which form from explosion ashes at these late times, are ideal diagnostics of the magnitude of 56Ni mixing in core-collapse SN ejecta. Stable Ni, which was identified in SN 2024ggi (e.g., [Ni II] 6.634 μm), is probably a common product of explosions of massive stars.
{"title":"An optical-to-infrared study of type II SN 2024ggi at nebular times","authors":"Luc Dessart, Rubina Kotak, Wynn Jacobson-Galán, Kaustav Das, Christoffer Fremling, Mansi Kasliwal, Yu-Jing Qin, Sam Rose","doi":"10.1051/0004-6361/202556304","DOIUrl":"https://doi.org/10.1051/0004-6361/202556304","url":null,"abstract":"We present 0.3–21 μm observations at ∼275 d and ∼400 d of type II supernova (SN) 2024ggi that combined ground-based optical and near-infrared data from the Keck I/II telescopes and space-based infrared data from the James Webb Space Telescope. Although the optical regions dominate the observed flux, SN 2024ggi is bright at infrared wavelengths (65% and 35% fall each side of 1 μm). SN 2024ggi exhibits a plethora of emission lines from H, He, intermediate-mass elements (O, Na, Mg, S, Ar, and Ca), and iron-group elements (IGEs; Fe, Co, and Ni). The width of all lines is essentially the same, which suggests efficient macroscopic chemical mixing of the inner ejecta at ≲2000 km s<sup>−1<sup/> and little mixing of <sup>56<sup/>Ni at higher velocities. Molecular emission in the infrared range is dominated by the CO fundamental, which radiates about 5% of the total SN luminosity. A molecule-free radiative-transfer model based on a standard explosion of a red supergiant star (i.e., ∼10<sup>51<sup/> erg, 0.06 <i>M<i/><sub>⊙<sub/> of <sup>56<sup/>Ni from a 15.2 <i>M<i/><sub>⊙<sub/> progenitor) yields a satisfactory match throughout the optical and infrared at both epochs. The SN 2024ggi CO luminosity is comparable to the fractional decay power absorbed in the model C/O-rich shell. An accounting for CO cooling would likely resolve the model overestimate of the [O I] 0.632 μm flux. The relative weakness of the molecular emission in SN 2024ggi and the good overall match obtained with our molecule-free model suggests negligible microscopic mixing; about 95% of the SN luminosity is radiated by atoms and ions. The lines from IGEs, which form from explosion ashes at these late times, are ideal diagnostics of the magnitude of <sup>56<sup/>Ni mixing in core-collapse SN ejecta. Stable Ni, which was identified in SN 2024ggi (e.g., [Ni II] 6.634 μm), is probably a common product of explosions of massive stars.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"6 1","pages":"L6"},"PeriodicalIF":6.5,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697205","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 : 2025-12-02DOI: 10.1051/0004-6361/202556356
S. de Wet, G. Leloudas, D. A. H. Buckley, N. Erasmus, P. J. Groot, E. A. Zimmerman
<i>Context.<i/> Type IIb supernovae (SNe) are a transitional subclass of stripped-envelope SNe showing hydrogen lines in their spectra that gradually weaken and give way to helium lines reminiscent of SNe Ib. The presence of hydrogen indicates that these SNe retain a non-negligible hydrogen-rich envelope that has been stripped through stellar winds or binary interaction.<i>Aims.<i/> The direct detection of SN progenitors is a valuable way to connect the various SN sub-types with their progenitor stars. SN 2024abfo is the seventh SN IIb with a direct progenitor detection. Our aim is to study the progenitor candidate and the SN itself to determine the evolutionary history of the system.<i>Methods.<i/> In this paper, we astrometrically register our ERIS adaptive optics imaging with archival <i>HST<i/> imaging to determine whether the SN position is consistent with the progenitor candidate position. We perform photometry on archival DECam imaging to derive the spectral energy distribution of the progenitor candidate and investigate its temporal variability. We consider single and binary star models to explain the end point of the progenitor candidate in the Hertzsprung-Russell diagram. For the SN, we compare the light curves and spectra with other SNe IIb with progenitor detections. We derive the bolometric light curve and attempt to fit this with a semi-analytic light curve model.<i>Results.<i/> The position of the SN in our adaptive optics imaging agrees with the progenitor position to within 20 mas. The progenitor spectral energy distribution is consistent with an A3V star with a radius of ∼120 <i>R<i/><sub>⊙<sub/>, a temperature of ∼8800 K, and a luminosity of log(<i>L<i/>/<i>L<i/><sub>⊙<sub/>)∼4.9. Single star models predict an initial mass in the range of 12–16 <i>M<i/><sub>⊙<sub/>, while the most probable binary model is a 12 + 1.2 <i>M<i/><sub>⊙<sub/> system with an initial period of 1.73 years. We also find significant evidence of variability of the progenitor candidate in the years prior to core collapse. SN 2024abfo is the least luminous SN IIb with a direct progenitor detection. At late times, the <i>r<i/>-band light curve decays more slowly than the comparison SNe, which may be due to increased <i>γ<i/>-ray trapping, although this requires further investigation. Similar to SN 2008ax, SN 2024abfo does not show a prominent double-peaked light curve. Our semi-analytic light curve modelling shows that this may be due to a very low mass of hydrogen (≲0.006 <i>M<i/><sub>⊙<sub/>) in the outer envelope. Spectrally, SN 2024abfo is most similar to SN 2008ax at early times, while at later times (∼80 days) it appears to show persistent H<i>α<i/> absorption compared to the comparison sample.<i>Conclusions.<i/> We prefer a binary system to explain SN 2024abfo and its progenitor, but we are unable to rule out single star models. We recommend late-time observations to search for a binary companion and signatures of circumstellar medium interaction. The
{"title":"A low mass, binary-stripped envelope for the Type IIb SN 2024abfo","authors":"S. de Wet, G. Leloudas, D. A. H. Buckley, N. Erasmus, P. J. Groot, E. A. Zimmerman","doi":"10.1051/0004-6361/202556356","DOIUrl":"https://doi.org/10.1051/0004-6361/202556356","url":null,"abstract":"<i>Context.<i/> Type IIb supernovae (SNe) are a transitional subclass of stripped-envelope SNe showing hydrogen lines in their spectra that gradually weaken and give way to helium lines reminiscent of SNe Ib. The presence of hydrogen indicates that these SNe retain a non-negligible hydrogen-rich envelope that has been stripped through stellar winds or binary interaction.<i>Aims.<i/> The direct detection of SN progenitors is a valuable way to connect the various SN sub-types with their progenitor stars. SN 2024abfo is the seventh SN IIb with a direct progenitor detection. Our aim is to study the progenitor candidate and the SN itself to determine the evolutionary history of the system.<i>Methods.<i/> In this paper, we astrometrically register our ERIS adaptive optics imaging with archival <i>HST<i/> imaging to determine whether the SN position is consistent with the progenitor candidate position. We perform photometry on archival DECam imaging to derive the spectral energy distribution of the progenitor candidate and investigate its temporal variability. We consider single and binary star models to explain the end point of the progenitor candidate in the Hertzsprung-Russell diagram. For the SN, we compare the light curves and spectra with other SNe IIb with progenitor detections. We derive the bolometric light curve and attempt to fit this with a semi-analytic light curve model.<i>Results.<i/> The position of the SN in our adaptive optics imaging agrees with the progenitor position to within 20 mas. The progenitor spectral energy distribution is consistent with an A3V star with a radius of ∼120 <i>R<i/><sub>⊙<sub/>, a temperature of ∼8800 K, and a luminosity of log(<i>L<i/>/<i>L<i/><sub>⊙<sub/>)∼4.9. Single star models predict an initial mass in the range of 12–16 <i>M<i/><sub>⊙<sub/>, while the most probable binary model is a 12 + 1.2 <i>M<i/><sub>⊙<sub/> system with an initial period of 1.73 years. We also find significant evidence of variability of the progenitor candidate in the years prior to core collapse. SN 2024abfo is the least luminous SN IIb with a direct progenitor detection. At late times, the <i>r<i/>-band light curve decays more slowly than the comparison SNe, which may be due to increased <i>γ<i/>-ray trapping, although this requires further investigation. Similar to SN 2008ax, SN 2024abfo does not show a prominent double-peaked light curve. Our semi-analytic light curve modelling shows that this may be due to a very low mass of hydrogen (≲0.006 <i>M<i/><sub>⊙<sub/>) in the outer envelope. Spectrally, SN 2024abfo is most similar to SN 2008ax at early times, while at later times (∼80 days) it appears to show persistent H<i>α<i/> absorption compared to the comparison sample.<i>Conclusions.<i/> We prefer a binary system to explain SN 2024abfo and its progenitor, but we are unable to rule out single star models. We recommend late-time observations to search for a binary companion and signatures of circumstellar medium interaction. The ","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"4 4 1","pages":"A89"},"PeriodicalIF":6.5,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697210","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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