Pub Date : 2025-12-18DOI: 10.1051/0004-6361/202557558
Aristeidis Polychronakis, Ioannis Liodakis, Anastasia Glykopoulou, Dmitry Blinov, Iván Agudo, Svetlana G. Jorstad, Beatriz Agís-González, Sara Capecchiacci, Alberto Floris, Sebastian Kielhmann, John A. Kypriotakis, Dimitrios A. Langis, Nikos Mandarakas, Karan Pal, Francisco J. Aceituno, Giacomo Bonnoli, Víctor Casanova, Gabriel Emery, Juan Escudero Pedrosa, Jorge Otero-Santos, Daniel Morcuende, Alfredo Sota, Vilppu Piirola
Blazars are known for their extreme variability across the electromagnetic spectrum. Variability at very short timescales can allow us to discriminate between competing models. This is particularly true for polarization variability, which allows us to probe particle acceleration and high-energy emission models in blazars. Here we present results from the first pilot study of intra-night optical polarization monitoring conducted using RoboPol at the Skinakas Observatory; these results are supplemented by observations from the Calar Alto, Perkins, and Sierra Nevada observatories. Our results show that while variability patterns can vary widely between sources, variability on timescales as short as minutes is prevalent in blazar jets. The amplitudes of the variations are typically small, a few percent for the polarization degree and less than 20° for the polarization angle, pointing to a significant contribution to the optical emission from a turbulent magnetic field component. The overall stability of the polarization angle over time points to a preferred magnetic field orientation.
{"title":"Intra-night optical polarization monitoring of blazars","authors":"Aristeidis Polychronakis, Ioannis Liodakis, Anastasia Glykopoulou, Dmitry Blinov, Iván Agudo, Svetlana G. Jorstad, Beatriz Agís-González, Sara Capecchiacci, Alberto Floris, Sebastian Kielhmann, John A. Kypriotakis, Dimitrios A. Langis, Nikos Mandarakas, Karan Pal, Francisco J. Aceituno, Giacomo Bonnoli, Víctor Casanova, Gabriel Emery, Juan Escudero Pedrosa, Jorge Otero-Santos, Daniel Morcuende, Alfredo Sota, Vilppu Piirola","doi":"10.1051/0004-6361/202557558","DOIUrl":"https://doi.org/10.1051/0004-6361/202557558","url":null,"abstract":"Blazars are known for their extreme variability across the electromagnetic spectrum. Variability at very short timescales can allow us to discriminate between competing models. This is particularly true for polarization variability, which allows us to probe particle acceleration and high-energy emission models in blazars. Here we present results from the first pilot study of intra-night optical polarization monitoring conducted using RoboPol at the Skinakas Observatory; these results are supplemented by observations from the Calar Alto, Perkins, and Sierra Nevada observatories. Our results show that while variability patterns can vary widely between sources, variability on timescales as short as minutes is prevalent in blazar jets. The amplitudes of the variations are typically small, a few percent for the polarization degree and less than 20° for the polarization angle, pointing to a significant contribution to the optical emission from a turbulent magnetic field component. The overall stability of the polarization angle over time points to a preferred magnetic field orientation.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"3 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145784706","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 : 2025-12-18DOI: 10.1051/0004-6361/202557774
J. P. Faria, J.-B. Delisle, D. Ségransan
We introduce a new method to infer the posterior distribution for planet occurrence rates from radial velocity (RV) observations. The approach combines posterior samples from the analysis of individual RV datasets of several stars, using importance sampling to re-weight them appropriately. This eliminates the need for injection-recovery tests to compute detection limits and avoids the explicit definition of a detection threshold. We validate the method on simulated RV datasets and show that it yields unbiased estimates of the occurrence rate in different regions with increasing precision as more stars are included in the analysis.
{"title":"Inferring planet occurrence rates from radial velocities","authors":"J. P. Faria, J.-B. Delisle, D. Ségransan","doi":"10.1051/0004-6361/202557774","DOIUrl":"https://doi.org/10.1051/0004-6361/202557774","url":null,"abstract":"We introduce a new method to infer the posterior distribution for planet occurrence rates from radial velocity (RV) observations. The approach combines posterior samples from the analysis of individual RV datasets of several stars, using importance sampling to re-weight them appropriately. This eliminates the need for injection-recovery tests to compute detection limits and avoids the explicit definition of a detection threshold. We validate the method on simulated RV datasets and show that it yields unbiased estimates of the occurrence rate in different regions with increasing precision as more stars are included in the analysis.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"23 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145784702","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 : 2025-12-18DOI: 10.1051/0004-6361/202557164
I. Delvecchio, E. Daddi, B. Magnelli, D. Elbaz, M. Giavalisco, A. Traina, G. Lanzuisi, H. B. Akins, S. Belli, C. M. Casey, F. Gentile, C. Gruppioni, F. Pozzi, G. Zamorani
Little red dots (LRDs) are a puzzling population of extragalactic sources whose origin is highly debated. In this work, we performed a comprehensive stacking analysis of NIRCam, MIRI, and ALMA images of a large and homogeneously selected sample of LRDs from multiple JWST Legacy fields. We report clear evidence of hot-dust emission in the median stacked spectral energy distribution (SED) that features a rising near-infrared continuum up to rest-frame λrest ∼ 3 μm, which is best explained by a standard dusty active galactic nucleus (AGN) structure. Although LRDs are likely to be a heterogeneous population, our findings suggest that most (≳50%) LRDs show AGN-heated dust emission, regardless of whether the optical and ultraviolet (UV) continua are stellar or AGN-dominated. In either case, the best-fit dusty-AGN SED, combined with the lack of X-ray detection in the deep Chandra stacks, suggests that Compton-thick (NH > 3 × 1024 cm−2) gas obscuration is common, and likely confined within the dust sublimation radius (Rsub ∼ 0.1 pc). Therefore, we argue that AGN-heated dust does not directly obscure either the optical-UV continuum or the broad-line region emission, in order to explain the observed blue UV slopes and prominent Balmer features. While a gas-dust displacement is in line with several models, the formation scenario (in-situ or ex-situ) of this pre-enriched hot dust remains unclear.
{"title":"Active galactic nuclei-heated dust revealed in “little red dots”","authors":"I. Delvecchio, E. Daddi, B. Magnelli, D. Elbaz, M. Giavalisco, A. Traina, G. Lanzuisi, H. B. Akins, S. Belli, C. M. Casey, F. Gentile, C. Gruppioni, F. Pozzi, G. Zamorani","doi":"10.1051/0004-6361/202557164","DOIUrl":"https://doi.org/10.1051/0004-6361/202557164","url":null,"abstract":"Little red dots (LRDs) are a puzzling population of extragalactic sources whose origin is highly debated. In this work, we performed a comprehensive stacking analysis of NIRCam, MIRI, and ALMA images of a large and homogeneously selected sample of LRDs from multiple JWST Legacy fields. We report clear evidence of hot-dust emission in the median stacked spectral energy distribution (SED) that features a rising near-infrared continuum up to rest-frame <i>λ<i/><sub>rest<sub/> ∼ 3 μm, which is best explained by a standard dusty active galactic nucleus (AGN) structure. Although LRDs are likely to be a heterogeneous population, our findings suggest that most (≳50%) LRDs show AGN-heated dust emission, regardless of whether the optical and ultraviolet (UV) continua are stellar or AGN-dominated. In either case, the best-fit dusty-AGN SED, combined with the lack of X-ray detection in the deep Chandra stacks, suggests that Compton-thick (<i>N<i/><sub>H<sub/> > 3 × 10<sup>24<sup/> cm<sup>−2<sup/>) gas obscuration is common, and likely confined within the dust sublimation radius (<i>R<i/><sub>sub<sub/> ∼ 0.1 pc). Therefore, we argue that AGN-heated dust does not directly obscure either the optical-UV continuum or the broad-line region emission, in order to explain the observed blue UV slopes and prominent Balmer features. While a gas-dust displacement is in line with several models, the formation scenario (in-situ or ex-situ) of this pre-enriched hot dust remains unclear.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"19 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145784704","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 : 2025-12-18DOI: 10.1051/0004-6361/202556635
Claudio Dalla Vecchia, Ignacio Trujillo
The physically motivated definition of galaxy size proposed recently, linked to the farther location of the in situ star formation, considerably reduces the scatter of the galaxy mass–size relation and provides a viable method to infer the galaxy stellar mass from its size. We provide a similar relation correlating the size of galaxies with the size of their dark matter haloes by leveraging the small scatter of the aforementioned relation. We analysed the simulated galaxies of the two main cosmological volumes of the EAGLE simulations and computed the size of the galaxies and their mass when mimicking the observational analysis. For central galaxies, we computed the relation between galaxy size and halo size. We show that the simulated galaxies reproduce the observed stellar mass–size relation’s normalisation and slope. The scatter of this relation, 0.06 dex, matches the intrinsic scatter measured in observation. We then computed the correlation between galaxy size and halo size and found that the relation is steeper than when using the half-mass radius as a measure of size, with the scatter (0.1 dex) being a factor of two smaller than the observed relation. As well, the galaxy-to-halo mass relation derived from the simulations provides a factor of two better scatter than the observed scatter. This opens the possibility of measuring the size of dark matter haloes with greater accuracy (less than 50%, i.e. around six times better than using the effective radius) by using only deep imaging data.
{"title":"An accurate measure of the size of dark matter haloes using the size of galaxies","authors":"Claudio Dalla Vecchia, Ignacio Trujillo","doi":"10.1051/0004-6361/202556635","DOIUrl":"https://doi.org/10.1051/0004-6361/202556635","url":null,"abstract":"The physically motivated definition of galaxy size proposed recently, linked to the farther location of the in situ star formation, considerably reduces the scatter of the galaxy mass–size relation and provides a viable method to infer the galaxy stellar mass from its size. We provide a similar relation correlating the size of galaxies with the size of their dark matter haloes by leveraging the small scatter of the aforementioned relation. We analysed the simulated galaxies of the two main cosmological volumes of the EAGLE simulations and computed the size of the galaxies and their mass when mimicking the observational analysis. For central galaxies, we computed the relation between galaxy size and halo size. We show that the simulated galaxies reproduce the observed stellar mass–size relation’s normalisation and slope. The scatter of this relation, 0.06 dex, matches the intrinsic scatter measured in observation. We then computed the correlation between galaxy size and halo size and found that the relation is steeper than when using the half-mass radius as a measure of size, with the scatter (0.1 dex) being a factor of two smaller than the observed relation. As well, the galaxy-to-halo mass relation derived from the simulations provides a factor of two better scatter than the observed scatter. This opens the possibility of measuring the size of dark matter haloes with greater accuracy (less than 50%, i.e. around six times better than using the effective radius) by using only deep imaging data.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145784707","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}
Context. Studying the transport of galactic cosmic rays (GCRs) is crucial for understanding the space radiation environment and large-scale heliospheric structures. Various numerical, observational, and theoretical studies have demonstrated that GCR fluxes are modulated by the interplanetary magnetic field (IMF), which evolves with the solar cycle. However, there are still open questions on how different modulation processes, and their dependence on the IMF, impact the GCR transport in the heliosphere. In particular, we still do not fully understand how GCR time variations lag behind solar activity changes, referred to as GCR delay time in this study.Aims. We aim to parameterize the GCR delay time with respect to several solar activity indices and determine how this delay changes with particle rigidity, thereby contributing to a better understanding of GCR modulation in the heliosphere.Methods. Based on long-term GCR observations with the SOlar and Heliospheric Observatory (SOHO) telescope, the Interplanetary Monitoring Platform-8 (IMP-8), and the Alpha Magnetic Spectrometer (AMS-02), we used the force-field approximation to derive an analytical formula for estimating the GCR modulation delay. We then applied information theory to quantify the GCR modulation delay innovatively and employed Monte Carlo methods to evaluate its uncertainty.Results. Consistent with previous findings, we confirm GCRs have a longer delay time for qA < 0 than qA > 0, where q is the GCR particle charge and A = 1 (or −1) if the solar magnetic field is predominantly outward (or inward) at the solar north pole. For protons with a rigidity of 0.8 GV or higher, the modulation delay time gradually decreases from 7–12 months to 2–3 months as rigidity increases and then remains constant, which can be explained by the finite propagation speed of solar activity information within the heliosphere.Conclusions. We formulate a rigidity-dependent expression for the GCR modulation delay using the force-field approximation and assess its applicability through observational analysis grounded in information theory. These findings offer new insights into the heliospheric transport of GCRs.
{"title":"The rigidity-dependent delay time of the galactic cosmic ray modulation with respect to the open solar magnetic flux","authors":"Yubao Wang, Jingnan Guo, Claudio Corti, Yuming Wang, Weihao Liu, Robert Wimmer-Schweingruber","doi":"10.1051/0004-6361/202557157","DOIUrl":"https://doi.org/10.1051/0004-6361/202557157","url":null,"abstract":"<i>Context.<i/> Studying the transport of galactic cosmic rays (GCRs) is crucial for understanding the space radiation environment and large-scale heliospheric structures. Various numerical, observational, and theoretical studies have demonstrated that GCR fluxes are modulated by the interplanetary magnetic field (IMF), which evolves with the solar cycle. However, there are still open questions on how different modulation processes, and their dependence on the IMF, impact the GCR transport in the heliosphere. In particular, we still do not fully understand how GCR time variations lag behind solar activity changes, referred to as GCR delay time in this study.<i>Aims.<i/> We aim to parameterize the GCR delay time with respect to several solar activity indices and determine how this delay changes with particle rigidity, thereby contributing to a better understanding of GCR modulation in the heliosphere.<i>Methods.<i/> Based on long-term GCR observations with the SOlar and Heliospheric Observatory (SOHO) telescope, the Interplanetary Monitoring Platform-8 (IMP-8), and the Alpha Magnetic Spectrometer (AMS-02), we used the force-field approximation to derive an analytical formula for estimating the GCR modulation delay. We then applied information theory to quantify the GCR modulation delay innovatively and employed Monte Carlo methods to evaluate its uncertainty.<i>Results.<i/> Consistent with previous findings, we confirm GCRs have a longer delay time for <i>qA<i/> < 0 than <i>qA<i/> > 0, where <i>q<i/> is the GCR particle charge and <i>A<i/> = 1 (or −1) if the solar magnetic field is predominantly outward (or inward) at the solar north pole. For protons with a rigidity of 0.8 GV or higher, the modulation delay time gradually decreases from 7–12 months to 2–3 months as rigidity increases and then remains constant, which can be explained by the finite propagation speed of solar activity information within the heliosphere.<i>Conclusions.<i/> We formulate a rigidity-dependent expression for the GCR modulation delay using the force-field approximation and assess its applicability through observational analysis grounded in information theory. These findings offer new insights into the heliospheric transport of GCRs.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"11 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145784744","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}
Context. Asteroid surface reconstruction is essential for deep space exploration missions, as it provides critical information about surface morphology that supports spacecraft navigation and sample acquisition. Traditional methods, such as stereo-photogrammetry (SPG) and stereo-photoclinometry (SPC), have been widely applied in asteroid missions, which often rely on large amounts of data or considerable manual intervention to derive reliable models. Meanwhile, intelligent methods based on the neural radiance field (NeRF) suffer from slow processing speeds, often requiring several hours or even days to complete surface reconstruction. Recent 3D Gaussian splatting (3DGS) shows promise in fast surface reconstruction but faces some challenges in asteroid scenarios, limiting its direct application.Aims. This paper presents Asteroid-GS, a fast and intelligent method for reconstructing asteroid surface models based on 3DGS. It is intended to complement current methodologies, enabling asteroid reconstruction with a limited number of images and a small amount of processing time while achieving an accuracy comparable that of to existing algorithms.Methods. Our method incorporates an adaptive Gaussian pruning strategy to remove noise from asteroids in deep space environments. The shallow multilayer perceptrons integrated with asteroid illumination are employed to improve the reconstruction in both well-lit and shadowed regions. Additionally, we employ geometric regularization techniques to enhance surface detail preservation and construct the Gaussian opacity field to enable accurate surface mesh extraction.Results. Experimental results on asteroids Itokawa and Ryugu demonstrate that our method outperforms state-of-the-art 3DGS-based methods in terms of 3D model accuracy and novel view synthesis. It maintains geometric consistency with traditional models, achieving better results than SPG given the same input images, while notably reducing processing time and manual intervention compared to SPC. Asteroid-GS completes reconstruction within one hour, requiring significantly less time than NeRF-based methods. Our work provides a supplementary solution for asteroid surface reconstruction, potentially improving the efficiency of future exploration missions.
{"title":"Asteroid-GS: 3D Gaussian splatting for fast surface reconstruction of asteroids","authors":"Xiaojie Zhang, Linyan Cui, Xiaodong Wei, Yicong Chen","doi":"10.1051/0004-6361/202556730","DOIUrl":"https://doi.org/10.1051/0004-6361/202556730","url":null,"abstract":"<i>Context.<i/> Asteroid surface reconstruction is essential for deep space exploration missions, as it provides critical information about surface morphology that supports spacecraft navigation and sample acquisition. Traditional methods, such as stereo-photogrammetry (SPG) and stereo-photoclinometry (SPC), have been widely applied in asteroid missions, which often rely on large amounts of data or considerable manual intervention to derive reliable models. Meanwhile, intelligent methods based on the neural radiance field (NeRF) suffer from slow processing speeds, often requiring several hours or even days to complete surface reconstruction. Recent 3D Gaussian splatting (3DGS) shows promise in fast surface reconstruction but faces some challenges in asteroid scenarios, limiting its direct application.<i>Aims.<i/> This paper presents Asteroid-GS, a fast and intelligent method for reconstructing asteroid surface models based on 3DGS. It is intended to complement current methodologies, enabling asteroid reconstruction with a limited number of images and a small amount of processing time while achieving an accuracy comparable that of to existing algorithms.<i>Methods.<i/> Our method incorporates an adaptive Gaussian pruning strategy to remove noise from asteroids in deep space environments. The shallow multilayer perceptrons integrated with asteroid illumination are employed to improve the reconstruction in both well-lit and shadowed regions. Additionally, we employ geometric regularization techniques to enhance surface detail preservation and construct the Gaussian opacity field to enable accurate surface mesh extraction.<i>Results.<i/> Experimental results on asteroids Itokawa and Ryugu demonstrate that our method outperforms state-of-the-art 3DGS-based methods in terms of 3D model accuracy and novel view synthesis. It maintains geometric consistency with traditional models, achieving better results than SPG given the same input images, while notably reducing processing time and manual intervention compared to SPC. Asteroid-GS completes reconstruction within one hour, requiring significantly less time than NeRF-based methods. Our work provides a supplementary solution for asteroid surface reconstruction, potentially improving the efficiency of future exploration missions.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145771634","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 : 2025-12-17DOI: 10.1051/0004-6361/202554844
T. W. H. Yiu, H. K. Vedantham, J. R. Callingham, T. W. Shimwell
Brown dwarfs display Jupiter-like auroral phenomena, such as rotationally modulated electron cyclotron maser radio emission. Radio observations of cyclotron maser emission can be used to measure their magnetic field strength and topology, and to deduce the presence of magnetically interacting exoplanets. Observations of the coldest brown dwarfs (spectral types T and Y) are especially intriguing, as their magnetospheric phenomena could, in fact, closely resemble those of gas-giant exoplanets. Here, we report observations made over ten epochs, amounting to 44 hours, of WISEP J101905.63+652954.2 (J1019+65, hereinafter) using the LOFAR telescope between 120 and 168 MHz. J1019+65 is a methane dwarf binary (T5.5 + T7) whose radio emission was originally detected in a single-epoch LOFAR observation to be highly circular polarised and rotationally modulated at ≈3 h. Unexpectedly, our long-term monitoring reveals an additional periodic signature at ≈0.787 h. We considered several explanations for the second period and ultimately proposed that it could be the rotationally modulated emission of the second brown dwarf in the binary, although follow-up infrared (IR) observations are necessary to confirm this hypothesis. In addition, the data also allowed us to statistically estimate the duty cycle and observed radio-loud fraction, respectively, of the 120-168 MHz cyclotron emission from methane dwarfs to be ⟨D⟩ = 0.030−0.030+0.034 and F′radio = 0.088−0.088+0.168.
{"title":"Unusual periodic modulation in the radio emission of the methane dwarf binary WISEP J101905.63+652954.2","authors":"T. W. H. Yiu, H. K. Vedantham, J. R. Callingham, T. W. Shimwell","doi":"10.1051/0004-6361/202554844","DOIUrl":"https://doi.org/10.1051/0004-6361/202554844","url":null,"abstract":"Brown dwarfs display Jupiter-like auroral phenomena, such as rotationally modulated electron cyclotron maser radio emission. Radio observations of cyclotron maser emission can be used to measure their magnetic field strength and topology, and to deduce the presence of magnetically interacting exoplanets. Observations of the coldest brown dwarfs (spectral types T and Y) are especially intriguing, as their magnetospheric phenomena could, in fact, closely resemble those of gas-giant exoplanets. Here, we report observations made over ten epochs, amounting to 44 hours, of WISEP J101905.63+652954.2 (J1019+65, hereinafter) using the LOFAR telescope between 120 and 168 MHz. J1019+65 is a methane dwarf binary (T5.5 + T7) whose radio emission was originally detected in a single-epoch LOFAR observation to be highly circular polarised and rotationally modulated at ≈3 h. Unexpectedly, our long-term monitoring reveals an additional periodic signature at ≈0.787 h. We considered several explanations for the second period and ultimately proposed that it could be the rotationally modulated emission of the second brown dwarf in the binary, although follow-up infrared (IR) observations are necessary to confirm this hypothesis. In addition, the data also allowed us to statistically estimate the duty cycle and observed radio-loud fraction, respectively, of the 120-168 MHz cyclotron emission from methane dwarfs to be ⟨D⟩ = 0.030<sub>−0.030<sub/><sup>+0.034<sup/> and F<sup>′<sup/><sub>radio<sub/> = 0.088<sub>−0.088<sub/><sup>+0.168<sup/>.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"31 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145771635","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 : 2025-12-17DOI: 10.1051/0004-6361/202556947
M. Racca, T. T. Hansen, I. U. Roederer, V. M. Placco, A. Frebel, T. C. Beers, R. Ezzeddine, E. M. Holmbeck, C. M. Sakari, S. Monty, Ø. Harket, J. D. Simon, C. Sneden, I. B. Thompson
Context. The astrophysical origin of the rapid neutron-capture process (r-process), responsible for producing roughly half of the elements heavier than iron, remains uncertain. Detailed chemical signatures from the oldest, most metal-poor stars, which act as fossil records of the earliest nucleosynthesis events, can be used to identify the dominant r-process sites.Aims. We present a homogeneous chemical abundance analysis of ten r-process element-enhanced stars. These old and metal-poor stars are strongly enriched in r-process elements with minimal contamination from other nucleosynthetic sources. By focusing on this chemically pure sample, we aim to investigate intrinsic variations in the r-process abundance patterns and explore their implications for the nature and potential diversity of r-process sites.Methods. We performed a detailed chemical abundance analysis of high-resolution, high-signal-to-noise spectra. For each star, we inspected over 1400 individual absorption lines using a combination of equivalent width measurements and spectral synthesis. The analysis was conducted under the assumption of 1D local thermodynamic equilibrium and employing the MOOG radiative transfer code.Results. We derived abundances for 54 chemical species, including 29 neutron-capture (n-capture) elements, covering the full mass range of the r-process abundance pattern. A kinematic analysis reveals that stars likely originated from ten kinematically distinct systems. Based on this assumption, we used the sample to probe the maximum variation expected from ten independent r-process nucleosynthesis events and computed the intrinsic dispersion of each element relative to Zr and Eu for the light and heavy r-process elements, respectively. This exercise resulted in a remarkably low cosmic scatter across the ten r-process sites enriching these stars; for the rare earth and third peak elements, for example, we find σ[La/Eu] = 0.08 and σ[Os/Eu] = 0.11 dex, while the scatter between light and heavy elements, σ[Zr/Eu], is slightly higher at 0.18 dex.Conclusions. The elemental abundance patterns across the ten independent r-process sites show remarkably small cosmic dispersions. This minimal dispersion suggests a high degree of uniformity in r-process yields across diverse astrophysical environments.
{"title":"The R-Process Alliance: Exploring the cosmic scatter among ten r-process sites with stellar abundances★","authors":"M. Racca, T. T. Hansen, I. U. Roederer, V. M. Placco, A. Frebel, T. C. Beers, R. Ezzeddine, E. M. Holmbeck, C. M. Sakari, S. Monty, Ø. Harket, J. D. Simon, C. Sneden, I. B. Thompson","doi":"10.1051/0004-6361/202556947","DOIUrl":"https://doi.org/10.1051/0004-6361/202556947","url":null,"abstract":"<i>Context<i/>. The astrophysical origin of the rapid neutron-capture process (<i>r<i/>-process), responsible for producing roughly half of the elements heavier than iron, remains uncertain. Detailed chemical signatures from the oldest, most metal-poor stars, which act as fossil records of the earliest nucleosynthesis events, can be used to identify the dominant <i>r<i/>-process sites.<i>Aims<i/>. We present a homogeneous chemical abundance analysis of ten <i>r<i/>-process element-enhanced stars. These old and metal-poor stars are strongly enriched in <i>r<i/>-process elements with minimal contamination from other nucleosynthetic sources. By focusing on this chemically pure sample, we aim to investigate intrinsic variations in the <i>r<i/>-process abundance patterns and explore their implications for the nature and potential diversity of <i>r<i/>-process sites.<i>Methods<i/>. We performed a detailed chemical abundance analysis of high-resolution, high-signal-to-noise spectra. For each star, we inspected over 1400 individual absorption lines using a combination of equivalent width measurements and spectral synthesis. The analysis was conducted under the assumption of 1D local thermodynamic equilibrium and employing the MOOG radiative transfer code.<i>Results<i/>. We derived abundances for 54 chemical species, including 29 neutron-capture (<i>n<i/>-capture) elements, covering the full mass range of the <i>r<i/>-process abundance pattern. A kinematic analysis reveals that stars likely originated from ten kinematically distinct systems. Based on this assumption, we used the sample to probe the maximum variation expected from ten independent <i>r<i/>-process nucleosynthesis events and computed the intrinsic dispersion of each element relative to Zr and Eu for the light and heavy <i>r<i/>-process elements, respectively. This exercise resulted in a remarkably low cosmic scatter across the ten <i>r<i/>-process sites enriching these stars; for the rare earth and third peak elements, for example, we find <i>σ<i/><sub>[La/Eu]<sub/> = 0.08 and <i>σ<i/><sub>[Os/Eu]<sub/> = 0.11 dex, while the scatter between light and heavy elements, <i>σ<i/><sub>[Zr/Eu]<sub/>, is slightly higher at 0.18 dex.<i>Conclusions<i/>. The elemental abundance patterns across the ten independent <i>r<i/>-process sites show remarkably small cosmic dispersions. This minimal dispersion suggests a high degree of uniformity in <i>r<i/>-process yields across diverse astrophysical environments.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"36 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145771632","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 : 2025-12-17DOI: 10.1051/0004-6361/202557362
Alex Kemp, Jasmine Vrancken, Joey S. G. Mombarg, Luc IJspeert, Mykyta Kliapets, Andrew Tkachenko, Conny Aerts
Context. In the modern era of large-scale photometric time-domain surveys, relatively rare but information-rich eclipsing binary systems can be leveraged at a population level across the Hertzsprung-Russel diagram to improve our knowledge of stellar evolution. This high-precision photometry is also excellent for assessing and exploiting the asteroseismic properties of such stars and results in a powerful synergy that has great potential for shedding light on how stellar interiors and tides affect stellar evolution and mass transfer.Aims. In this work, we seek to characterise a large sample of 14 377 main sequence eclipsing binaries in terms of their stellar, astero-seismic, and orbital properties.Methods. We conducted manual vetting on a sub-set of 4000 targets from our full 14 377 target sample to identify targets with pressure or gravity modes. We inferred stellar properties including mass, the convective core mass, radius, and central H fraction for the primary using the Gaia Data Release 3 effective temperature and luminosity estimates and a grid of asteroseismically calibrated stellar models. We used surface brightness ratio and radius ratio estimates from previous eclipse analyses to study the effect of binarity on our results.Results. Through our manual vetting, we identified 751 candidate g-mode pulsators, 131 p-mode pulsators, and a further 48 hybrid pulsators. The inferred stellar properties of the hybrid and p-mode pulsators are highly correlated, while the orbital properties of the hybrid pulsators align best with the g-mode pulsators. The g-mode pulsators themselves show a distribution that peaks around the classical γ Dor instability region but extends continuously towards higher masses, with no detectable divide between the classical γ Dor and SPB instability regions. There is evidence at the population level for a heightened level of tidal efficiency in stars showing g-mode or hybrid variability. We corrected the primary mass inference for binarity based on eclipse measurements of the surface brightness and radius ratios, resulting in a relatively small shift towards lower masses.Conclusions. This work provides a working initial characterisation of this sample from which more detailed analyses folding in aster-oseismic information can be built. It also provides a foundational understanding of the limitations and capabilities of this kind of rapid, scalable analysis that will be highly relevant in planning the exploitation of future large-scale binary surveys.
{"title":"Populations of tidal and pulsating variables in eclipsing binaries","authors":"Alex Kemp, Jasmine Vrancken, Joey S. G. Mombarg, Luc IJspeert, Mykyta Kliapets, Andrew Tkachenko, Conny Aerts","doi":"10.1051/0004-6361/202557362","DOIUrl":"https://doi.org/10.1051/0004-6361/202557362","url":null,"abstract":"<i>Context.<i/> In the modern era of large-scale photometric time-domain surveys, relatively rare but information-rich eclipsing binary systems can be leveraged at a population level across the Hertzsprung-Russel diagram to improve our knowledge of stellar evolution. This high-precision photometry is also excellent for assessing and exploiting the asteroseismic properties of such stars and results in a powerful synergy that has great potential for shedding light on how stellar interiors and tides affect stellar evolution and mass transfer.<i>Aims.<i/> In this work, we seek to characterise a large sample of 14 377 main sequence eclipsing binaries in terms of their stellar, astero-seismic, and orbital properties.<i>Methods.<i/> We conducted manual vetting on a sub-set of 4000 targets from our full 14 377 target sample to identify targets with pressure or gravity modes. We inferred stellar properties including mass, the convective core mass, radius, and central H fraction for the primary using the <i>Gaia<i/> Data Release 3 effective temperature and luminosity estimates and a grid of asteroseismically calibrated stellar models. We used surface brightness ratio and radius ratio estimates from previous eclipse analyses to study the effect of binarity on our results.<i>Results.<i/> Through our manual vetting, we identified 751 candidate g-mode pulsators, 131 p-mode pulsators, and a further 48 hybrid pulsators. The inferred stellar properties of the hybrid and p-mode pulsators are highly correlated, while the orbital properties of the hybrid pulsators align best with the g-mode pulsators. The g-mode pulsators themselves show a distribution that peaks around the classical <i>γ<i/> Dor instability region but extends continuously towards higher masses, with no detectable divide between the classical <i>γ<i/> Dor and SPB instability regions. There is evidence at the population level for a heightened level of tidal efficiency in stars showing g-mode or hybrid variability. We corrected the primary mass inference for binarity based on eclipse measurements of the surface brightness and radius ratios, resulting in a relatively small shift towards lower masses.<i>Conclusions.<i/> This work provides a working initial characterisation of this sample from which more detailed analyses folding in aster-oseismic information can be built. It also provides a foundational understanding of the limitations and capabilities of this kind of rapid, scalable analysis that will be highly relevant in planning the exploitation of future large-scale binary surveys.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"29 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145771692","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 : 2025-12-17DOI: 10.1051/0004-6361/202556787
S. Bellotti, P. I. Cristofari, J. R. Callingham, J. Morin, P. Petit, A. A. Vidotto, M. Jardine, L. Arnold, R. D. Kavanagh, J. LLama, H. Vedantham
Context. Radio observations at low frequencies are sensitive to the magnetic activity of stars and the plasma environment surrounding them, so one can scrutinize the conditions under which stellar space weather develops and impacts exoplanets. The accurate interpretation of the processes underlying the radio signatures requires a detailed characterisation of stellar magnetism.Aims. We study two M dwarfs, namely StKM 1-1262 (M0 type, Prot = 1.24 d) and V374 Peg (M4 type, Prot = 0.4455 d), which were detected recently with the LOw Frequency ARray (LOFAR). StKM 1-1262 exhibited the typical signature of a type-II radio burst, potentially resulting from a coronal mass ejection event. V374 Peg manifested low-frequency radio emission with high brightness temperature and low degree of polarisation, suggesting an electron-cyclotron maser instability emission mechanism. In this work, we provide recent observational constraints on the magnetic field of both stars.Methods. We analysed spectropolarimetric observations of these M dwarfs, collected with the SpectroPolarimètre InfraRouge (SPIRou). Firstly, we refined the stellar parameters, such as effective temperature, surface gravity, and metallicity, and measured the average surface magnetic flux via modelling of Zeeman broadening in unpolarised spectra. We then applied Zeeman-Doppler imaging to least-squares deconvolution line profiles in circular polarisation to reconstruct their large-scale magnetic fields. We also reconstructed a brightness map for the two stars using Doppler imaging.Results. StKM 1-1262 has a total, unsigned magnetic field of 3.53 ± 0.06 kG on average, and the large-scale magnetic field topology is predominantly poloidal, dipolar and moderately axisymmetric, with an average strength of 300 G. V374 Peg has an unsigned magnetic field of 5.46 ± 0.09 kG, and the large-scale field is poloidal, dipolar and axisymmetric, with an average strength of 800 G. For StKM 1-1262, we found a strong (Pearson ρ = −0.96) anti-correlation between the total magnetic field and the effective temperature, which is reminiscent of the tight link between small-scale magnetic fields and surface inhomogeneities. For V374 Peg, we found a moderate (ρ = −0.43) anti-correlation, possibly due to a more even distribution of surface features.Conclusions. The large-scale magnetic field topology of StKM 1-1262 is similar to other stars with similar fundamental parameters like mass and rotation period, and the brightness map features one dark spot, which is responsible for the rotational modulation of the total magnetic field and the retrieved effective temperature. For V374 Peg, the magnetic topology and the brightness map are similar to previous reconstructions, indicating a temporal stability of approximately 14-yr.
{"title":"A magnetic field study of two fast-rotating, radio-bright M dwarfs","authors":"S. Bellotti, P. I. Cristofari, J. R. Callingham, J. Morin, P. Petit, A. A. Vidotto, M. Jardine, L. Arnold, R. D. Kavanagh, J. LLama, H. Vedantham","doi":"10.1051/0004-6361/202556787","DOIUrl":"https://doi.org/10.1051/0004-6361/202556787","url":null,"abstract":"<i>Context.<i/> Radio observations at low frequencies are sensitive to the magnetic activity of stars and the plasma environment surrounding them, so one can scrutinize the conditions under which stellar space weather develops and impacts exoplanets. The accurate interpretation of the processes underlying the radio signatures requires a detailed characterisation of stellar magnetism.<i>Aims.<i/> We study two M dwarfs, namely StKM 1-1262 (M0 type, <i>P<i/><sub>rot<sub/> = 1.24 d) and V374 Peg (M4 type, <i>P<i/><sub>rot<sub/> = 0.4455 d), which were detected recently with the LOw Frequency ARray (LOFAR). StKM 1-1262 exhibited the typical signature of a type-II radio burst, potentially resulting from a coronal mass ejection event. V374 Peg manifested low-frequency radio emission with high brightness temperature and low degree of polarisation, suggesting an electron-cyclotron maser instability emission mechanism. In this work, we provide recent observational constraints on the magnetic field of both stars.<i>Methods.<i/> We analysed spectropolarimetric observations of these M dwarfs, collected with the SpectroPolarimètre InfraRouge (SPIRou). Firstly, we refined the stellar parameters, such as effective temperature, surface gravity, and metallicity, and measured the average surface magnetic flux via modelling of Zeeman broadening in unpolarised spectra. We then applied Zeeman-Doppler imaging to least-squares deconvolution line profiles in circular polarisation to reconstruct their large-scale magnetic fields. We also reconstructed a brightness map for the two stars using Doppler imaging.<i>Results.<i/> StKM 1-1262 has a total, unsigned magnetic field of 3.53 ± 0.06 kG on average, and the large-scale magnetic field topology is predominantly poloidal, dipolar and moderately axisymmetric, with an average strength of 300 G. V374 Peg has an unsigned magnetic field of 5.46 ± 0.09 kG, and the large-scale field is poloidal, dipolar and axisymmetric, with an average strength of 800 G. For StKM 1-1262, we found a strong (Pearson <i>ρ<i/> = −0.96) anti-correlation between the total magnetic field and the effective temperature, which is reminiscent of the tight link between small-scale magnetic fields and surface inhomogeneities. For V374 Peg, we found a moderate (<i>ρ<i/> = −0.43) anti-correlation, possibly due to a more even distribution of surface features.<i>Conclusions.<i/> The large-scale magnetic field topology of StKM 1-1262 is similar to other stars with similar fundamental parameters like mass and rotation period, and the brightness map features one dark spot, which is responsible for the rotational modulation of the total magnetic field and the retrieved effective temperature. For V374 Peg, the magnetic topology and the brightness map are similar to previous reconstructions, indicating a temporal stability of approximately 14-yr.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"12 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145771686","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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