Pub Date : 2025-12-05DOI: 10.1051/0004-6361/202557288
Deboki Reja, Paul S. Barklem, Stan Bartmentloo, Anders Jerkstrand
The charge-transfer process C + O+ → C+ + O (1D) has been found in previous modelling to be important in neutralising oxygen ions in supernova (SN) ejecta, as well as in determining the strength of the [O I] doublet at 6300 and 6364 Å. This conclusion is, however, based on a highly uncertain simple estimate of the rate coefficient. In this work, calculations of the cross-sections at low energy (0–10 eV) are performed using quantum mechanical methods. The rate coefficients at temperatures up to 10 000 K are determined and found to be significantly lower than the simple estimate. Using spectral modelling of SN ejecta, we show that the new rates change model predictions for [O I] λλ6300, 6364 and [C I] λλ9824, 9850 by ~10% in the early, warm nebular phases, and by yet larger factors in the late, cold phases, with direct impact on inferences of carbon and oxygen masses.
{"title":"Charge transfer in C + O+ collisions and its impact on supernova spectra","authors":"Deboki Reja, Paul S. Barklem, Stan Bartmentloo, Anders Jerkstrand","doi":"10.1051/0004-6361/202557288","DOIUrl":"https://doi.org/10.1051/0004-6361/202557288","url":null,"abstract":"The charge-transfer process C + O<sup>+<sup/> → C<sup>+<sup/> + O (<sup>1<sup/>D) has been found in previous modelling to be important in neutralising oxygen ions in supernova (SN) ejecta, as well as in determining the strength of the [O I] doublet at 6300 and 6364 Å. This conclusion is, however, based on a highly uncertain simple estimate of the rate coefficient. In this work, calculations of the cross-sections at low energy (0–10 eV) are performed using quantum mechanical methods. The rate coefficients at temperatures up to 10 000 K are determined and found to be significantly lower than the simple estimate. Using spectral modelling of SN ejecta, we show that the new rates change model predictions for [O I] <i>λλ<i/>6300, 6364 and [C I] <i>λλ<i/>9824, 9850 by ~10% in the early, warm nebular phases, and by yet larger factors in the late, cold phases, with direct impact on inferences of carbon and oxygen masses.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"11 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697372","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: 10.1051/0004-6361/202557059
C. E. Scardoni, G. P. Rosotti, C. J. Clarke, E. Ragusa, R. A. Booth
Context. Recent studies on the planet-dominated regime of type II migration have demonstrated the presence of a correlation between the direction of massive planet migration and the parameter K that describes the depth of the gap opened by the planet. Indeed, it has been reported that high (low) values for the K parameter correspond to an outward (inward) migration.Aims. In this paper, we aim to understand the mechanism driving inward and outward migration and why these mechanisms are correlated with the gap depth.Methods. We performed a suite of 2D, live-planet, long-term simulations of massive planets migrating in disks with the hydro-code FARGO3D. We focused on a range of planet masses (1–13 mJ) and disk aspect ratios (from 0.03 to 0.1). We analyzed the evolution of orbital elements and gap structure. We also studied the torque contributions from outer Lindblad resonances to investigate their role in the migration outcome.Results. We find that while all planets initially migrate inward, those with high enough K values eventually enter a phase in which the torque reverses sign and migration turns outward, until the point where it stalls. This behavior is associated with eccentricity growth in the outer disk and changes in the gap structure. We identified the surface density ratio at the 1:2 and 1:3 outer Lindblad resonances as a key output diagnostic that are correlated with the migration direction. In general, this ratio regulates the migration for all the cases where the massive planet remains in an almost circular orbit and the outer gap region exhibits moderate eccentricity. This characteristic sequence of inward-reversal-outward-stalling can occur for a variety of K values. Thus, further work is required to identify the simulation input parameters that determine the onset of this sequence.Conclusions. Our results suggest that outward migration in the planet-dominated regime is primarily governed by the relative importance of the 1:2 and 1:3 resonances. Therefore, the gap profiles play a crucial role in determining the direction of migration.
{"title":"Eccentric disks as a gateway to giant planet outward migration","authors":"C. E. Scardoni, G. P. Rosotti, C. J. Clarke, E. Ragusa, R. A. Booth","doi":"10.1051/0004-6361/202557059","DOIUrl":"https://doi.org/10.1051/0004-6361/202557059","url":null,"abstract":"<i>Context<i/>. Recent studies on the planet-dominated regime of type II migration have demonstrated the presence of a correlation between the direction of massive planet migration and the parameter <i>K<i/> that describes the depth of the gap opened by the planet. Indeed, it has been reported that high (low) values for the <i>K<i/> parameter correspond to an outward (inward) migration.<i>Aims<i/>. In this paper, we aim to understand the mechanism driving inward and outward migration and why these mechanisms are correlated with the gap depth.<i>Methods<i/>. We performed a suite of 2D, live-planet, long-term simulations of massive planets migrating in disks with the hydro-code FARGO3D. We focused on a range of planet masses (1–13 <i>m<i/><sub>J<sub/>) and disk aspect ratios (from 0.03 to 0.1). We analyzed the evolution of orbital elements and gap structure. We also studied the torque contributions from outer Lindblad resonances to investigate their role in the migration outcome.<i>Results<i/>. We find that while all planets initially migrate inward, those with high enough <i>K<i/> values eventually enter a phase in which the torque reverses sign and migration turns outward, until the point where it stalls. This behavior is associated with eccentricity growth in the outer disk and changes in the gap structure. We identified the surface density ratio at the 1:2 and 1:3 outer Lindblad resonances as a key output diagnostic that are correlated with the migration direction. In general, this ratio regulates the migration for all the cases where the massive planet remains in an almost circular orbit and the outer gap region exhibits moderate eccentricity. This characteristic sequence of inward-reversal-outward-stalling can occur for a variety of <i>K<i/> values. Thus, further work is required to identify the simulation input parameters that determine the onset of this sequence.<i>Conclusions<i/>. Our results suggest that outward migration in the planet-dominated regime is primarily governed by the relative importance of the 1:2 and 1:3 resonances. Therefore, the gap profiles play a crucial role in determining the direction of migration.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"4 1","pages":"A78"},"PeriodicalIF":6.5,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697207","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: 10.1051/0004-6361/202556757
K. Thomson-Paressant, C. Neiner, J. Labadie-Bartz, R.-M. Ouazzani, S. Mathis, L. Manchon
Context. At this time, the list of known magnetic δ Scuti stars is extremely limited, with only a select number of well-studied examples.Aims. We seek to expand this list, by retrieving targets from a variety of sources and demonstrating that they present simultaneously a surface magnetic field signature and δ Scuti pulsations.Methods. We obtained archival and new spectropolarimetric datasets for a variety of known δ Scuti stars and analysed them using the least squares deconvolution method to generate mean Stokes I and V profiles for each target, from which we can determine longitudinal magnetic field measurements. Additionally, we assessed photometric data from the TESS satellite to discern frequency peaks consistent with δ Scuti pulsations in known magnetic stars, and to identify magnetic candidates via rotational modulation.Results. We present a compiled list of all the confirmed magnetic δ Scuti stars discovered to date, containing 13 stars. The majority of this sample lies outside the usual δ Scuti instability strip in the Hertzsprung-Russell diagram, though we do not observe any specific correlations between magnetic field strength and various stellar parameters. This indicates that strong global magnetic fields play a fundamental role in shaping interior structure and processes. Magnetic fields thus must be included in realistic stellar models in order to more accurately predict structure and evolution.Conclusions. This work constitutes the largest database to date of strongly magnetic δ Scuti stars, one that will continue to grow over time with subsequent studies.
{"title":"Discovery of new magnetic δ Scuti stars and the impact of magnetism on pulsation excitation","authors":"K. Thomson-Paressant, C. Neiner, J. Labadie-Bartz, R.-M. Ouazzani, S. Mathis, L. Manchon","doi":"10.1051/0004-6361/202556757","DOIUrl":"https://doi.org/10.1051/0004-6361/202556757","url":null,"abstract":"<i>Context.<i/> At this time, the list of known magnetic <i>δ<i/> Scuti stars is extremely limited, with only a select number of well-studied examples.<i>Aims.<i/> We seek to expand this list, by retrieving targets from a variety of sources and demonstrating that they present simultaneously a surface magnetic field signature and <i>δ<i/> Scuti pulsations.<i>Methods.<i/> We obtained archival and new spectropolarimetric datasets for a variety of known <i>δ<i/> Scuti stars and analysed them using the least squares deconvolution method to generate mean Stokes <i>I<i/> and <i>V<i/> profiles for each target, from which we can determine longitudinal magnetic field measurements. Additionally, we assessed photometric data from the TESS satellite to discern frequency peaks consistent with <i>δ<i/> Scuti pulsations in known magnetic stars, and to identify magnetic candidates via rotational modulation.<i>Results.<i/> We present a compiled list of all the confirmed magnetic <i>δ<i/> Scuti stars discovered to date, containing 13 stars. The majority of this sample lies outside the usual <i>δ<i/> Scuti instability strip in the Hertzsprung-Russell diagram, though we do not observe any specific correlations between magnetic field strength and various stellar parameters. This indicates that strong global magnetic fields play a fundamental role in shaping interior structure and processes. Magnetic fields thus must be included in realistic stellar models in order to more accurately predict structure and evolution.<i>Conclusions.<i/> This work constitutes the largest database to date of strongly magnetic <i>δ<i/> Scuti stars, one that will continue to grow over time with subsequent studies.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"3 1","pages":"A134"},"PeriodicalIF":6.5,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145697212","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: 10.1051/0004-6361/202556644
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}
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