Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4002
Alison M. W. Mitchell, Giovanni Morlino, Silvia Celli, Stefano Menchiari and Andreas Specovius
Young and massive stellar clusters are a potential source of galactic cosmic rays due to at least two acceleration mechanisms. Collective stellar winds from massive stars form a wind-blown bubble with a termination shock at which particle acceleration to PeV energies may be achieved. Furthermore, shock acceleration may occur at supernova remnants (SNRs) expanding inside the bubble. We apply a model of cosmic-ray acceleration at both the collective wind termination shock and SNR shocks to the catalog of known stellar clusters derived from the Gaia DR2. Predictions for the secondary fluxes of γ-ray and neutrino emission are derived based on hadro-nuclear interactions with the surrounding medium. We compare our modeling under baseline and optimistic scenarios to available data, finding consistent results. An anticipated flux range is provided for a shortlist of the most promising stellar clusters. Approximately 10 clusters may be detectable with future facilities, and one to three could be currently operating as PeVatrons. Among these, data from three γ-ray detected clusters can be consistently described by our model. Several further as-yet-undetected stellar clusters offer promising targets for future γ-ray observations, although the flux range allowed by our model can be broad (≳ factor 10). The large angular size of the wind-blown bubble may pose a challenge, leading to low surface brightness emission, thus exacerbating the problem of source confusion. Nevertheless, we discuss how further work will help to constrain stellar clusters as PeVatron candidates.
{"title":"Probing Hadronic γ-Ray and High-energy Neutrino Emission from Gaia DR2 Star Clusters","authors":"Alison M. W. Mitchell, Giovanni Morlino, Silvia Celli, Stefano Menchiari and Andreas Specovius","doi":"10.3847/1538-4357/ae4002","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4002","url":null,"abstract":"Young and massive stellar clusters are a potential source of galactic cosmic rays due to at least two acceleration mechanisms. Collective stellar winds from massive stars form a wind-blown bubble with a termination shock at which particle acceleration to PeV energies may be achieved. Furthermore, shock acceleration may occur at supernova remnants (SNRs) expanding inside the bubble. We apply a model of cosmic-ray acceleration at both the collective wind termination shock and SNR shocks to the catalog of known stellar clusters derived from the Gaia DR2. Predictions for the secondary fluxes of γ-ray and neutrino emission are derived based on hadro-nuclear interactions with the surrounding medium. We compare our modeling under baseline and optimistic scenarios to available data, finding consistent results. An anticipated flux range is provided for a shortlist of the most promising stellar clusters. Approximately 10 clusters may be detectable with future facilities, and one to three could be currently operating as PeVatrons. Among these, data from three γ-ray detected clusters can be consistently described by our model. Several further as-yet-undetected stellar clusters offer promising targets for future γ-ray observations, although the flux range allowed by our model can be broad (≳ factor 10). The large angular size of the wind-blown bubble may pose a challenge, leading to low surface brightness emission, thus exacerbating the problem of source confusion. Nevertheless, we discuss how further work will help to constrain stellar clusters as PeVatron candidates.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"60 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Solar coronal rotation exhibits significant complexity, and its relationship with the 11 yr solar cycle remains poorly understood. Using 597 McIntosh synoptic maps (CR1601–CR2197), we construct the temporal evolution of coronal rotation by performing cross-correlation analysis of coronal hole areas between consecutive Carrington rotations. Results show coronal rotation rate decreases from the equator to mid-latitudes (45°–60°), then increases at high latitudes (>60°). Comparison across solar cycles 21–24 reveals that cycle 23 displays the highest equatorial rotation rate and the strongest differential rotation. Equatorial rotation rates in odd-numbered cycles are generally higher than in preceding even-numbered ones. The latitudinally averaged rotation rate reaches a minimum near solar maximum and recovers during the declining phase, likely due to the latitudinal migration of coronal holes. Hemispheric asymmetry analysis shows no significant north–south difference in rotation rates, contrasting sharply with the strong asymmetry in sunspot distributions. Time series analysis of rotational parameters A, B, and C reveals a significant negative correlation between A and B, and a positive correlation between A and C. Singular spectrum analysis identifies prominent 5.6 and 6.9 yr periods in all three, with only C showing a strong 10 yr period.
{"title":"Solar Coronal Rotation from 1973 to 2017: An Analytical Approach Based on Coronal Hole Areas","authors":"Zhijun Zhao, Yalin Li, Nanbin Xiang, Linhua Deng, Haijing Zhou and Xinhua Zhao","doi":"10.3847/1538-4357/ae4d12","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4d12","url":null,"abstract":"Solar coronal rotation exhibits significant complexity, and its relationship with the 11 yr solar cycle remains poorly understood. Using 597 McIntosh synoptic maps (CR1601–CR2197), we construct the temporal evolution of coronal rotation by performing cross-correlation analysis of coronal hole areas between consecutive Carrington rotations. Results show coronal rotation rate decreases from the equator to mid-latitudes (45°–60°), then increases at high latitudes (>60°). Comparison across solar cycles 21–24 reveals that cycle 23 displays the highest equatorial rotation rate and the strongest differential rotation. Equatorial rotation rates in odd-numbered cycles are generally higher than in preceding even-numbered ones. The latitudinally averaged rotation rate reaches a minimum near solar maximum and recovers during the declining phase, likely due to the latitudinal migration of coronal holes. Hemispheric asymmetry analysis shows no significant north–south difference in rotation rates, contrasting sharply with the strong asymmetry in sunspot distributions. Time series analysis of rotational parameters A, B, and C reveals a significant negative correlation between A and B, and a positive correlation between A and C. Singular spectrum analysis identifies prominent 5.6 and 6.9 yr periods in all three, with only C showing a strong 10 yr period.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"191 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4903
Meiqi Wang, Bin Chen, Mallory Wickline, Sijie Yu, Säm Krucker, Jeongwoo Lee and Haimin Wang
When in situ solar energetic electron (SEE) events are closely associated with nonthermal flares, the escaping electron population is frequently observed to be much smaller than the nonthermal-radiation-emitting population near the solar surface. If a single accelerated population drives both signatures, the physical mechanism causing this severe deficit of upward-propagating electrons remains poorly understood. Focusing on one of the 2022 November 10–12 SEE events associated with recurrent solar jets and interplanetary type III radio bursts, we present a new, combined microwave–X-ray analysis using the Expanded Owens Valley Solar Array and the Spectrometer/Telescope for Imaging X-rays on board Solar Orbiter. For the first time for such an event, this synergy enables spatially resolved diagnostics over a broad energy spectrum of the near-Sun energetic electrons, complemented by in situ measurements made by spacecraft at multiple heliocentric longitudes and distances. Consistent with earlier results based on in situ and X-ray data, our results show that only 0.1%–1% of energetic electrons escape into interplanetary space. Crucially, the new microwave spectral imaging analysis suggests that energetic electrons are strongly concentrated in a compact region just above a miniflare arcade at the base of the jet spire and that their number density decreases by at least 2 orders of magnitude in the direction of the jet spire away from this region. This steep gradient, revealed by the microwave diagnostics, points to efficient local acceleration and trapping in the region analogous to the above-the-loop-top “magnetic bottle” region in major eruptive flares, allowing only a small fraction of electrons to access open magnetic field lines and enter interplanetary space.
{"title":"Few Made It Out: A Multimessenger Study of an In Situ Solar Energetic Electron Event Driven by a Solar Jet","authors":"Meiqi Wang, Bin Chen, Mallory Wickline, Sijie Yu, Säm Krucker, Jeongwoo Lee and Haimin Wang","doi":"10.3847/1538-4357/ae4903","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4903","url":null,"abstract":"When in situ solar energetic electron (SEE) events are closely associated with nonthermal flares, the escaping electron population is frequently observed to be much smaller than the nonthermal-radiation-emitting population near the solar surface. If a single accelerated population drives both signatures, the physical mechanism causing this severe deficit of upward-propagating electrons remains poorly understood. Focusing on one of the 2022 November 10–12 SEE events associated with recurrent solar jets and interplanetary type III radio bursts, we present a new, combined microwave–X-ray analysis using the Expanded Owens Valley Solar Array and the Spectrometer/Telescope for Imaging X-rays on board Solar Orbiter. For the first time for such an event, this synergy enables spatially resolved diagnostics over a broad energy spectrum of the near-Sun energetic electrons, complemented by in situ measurements made by spacecraft at multiple heliocentric longitudes and distances. Consistent with earlier results based on in situ and X-ray data, our results show that only 0.1%–1% of energetic electrons escape into interplanetary space. Crucially, the new microwave spectral imaging analysis suggests that energetic electrons are strongly concentrated in a compact region just above a miniflare arcade at the base of the jet spire and that their number density decreases by at least 2 orders of magnitude in the direction of the jet spire away from this region. This steep gradient, revealed by the microwave diagnostics, points to efficient local acceleration and trapping in the region analogous to the above-the-loop-top “magnetic bottle” region in major eruptive flares, allowing only a small fraction of electrons to access open magnetic field lines and enter interplanetary space.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4c4d
Longhua Qin, Jiancheng Wang, Chuyuan Yang, Huaizhen Li, Quangui Gao, Ju Ma, Ao Wang, Weiwei Na, Ming Zhou, Zunli Yuan, Chunxia Gu and Guangbo Long
Very high energy (VHE; E ≳ 100 GeV) gamma rays are expected to experience strong attenuation during cosmological propagation due to electron–positron pair production on the extragalactic background light (EBL). Recent observations of GRB 221009A (z = 0.151), including photons up to ∼18 detected by LHAASO and a ∼300 TeV event reported by Carpet-3, suggest a higher-than-expected transparency of the Universe at extreme energies. These observations cannot be explained by standard EBL absorption alone; moreover, neither Lorentz invariance violation (LIV) nor photon–axion-like particle (ALP) oscillations, when considered in isolation, appear sufficient to account for the survival of such photons over cosmological distances. In this work, we propose a joint propagation scenario that incorporates photon–ALP mixing in astrophysical magnetic fields together with subluminal quadratic LIV corrections to the γγ pair-production threshold. Applying this framework to the broadband gamma-ray spectrum of GRB 221009A, we show that ALPs with coupling (gaγ = 1.685 × 10−10 GeV−1) and mass (ma = 9.545 × 10−8 eV), combined with a quadratic LIV energy scale (ELIV,2 = 1.30 × 10−7EPl) adopted from the literature, can significantly enhance the photon survival probability in the energy range (10–300) TeV. The resulting enhancement exceeds that obtained from either ALP mixing or LIV effects alone. These results indicate that a combined ALP–LIV scenario may provide a viable interpretation of the extreme-energy gamma-ray observations of GRB 221009A and highlight the potential of VHE gamma-ray measurements as probes of physics beyond the Standard Model.
{"title":"Revisiting Very High Energy Gamma-Ray Absorption in Cosmic Propagation under the Combined Effects of Axion-like Particles and Lorentz Invariance Violation","authors":"Longhua Qin, Jiancheng Wang, Chuyuan Yang, Huaizhen Li, Quangui Gao, Ju Ma, Ao Wang, Weiwei Na, Ming Zhou, Zunli Yuan, Chunxia Gu and Guangbo Long","doi":"10.3847/1538-4357/ae4c4d","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4c4d","url":null,"abstract":"Very high energy (VHE; E ≳ 100 GeV) gamma rays are expected to experience strong attenuation during cosmological propagation due to electron–positron pair production on the extragalactic background light (EBL). Recent observations of GRB 221009A (z = 0.151), including photons up to ∼18 detected by LHAASO and a ∼300 TeV event reported by Carpet-3, suggest a higher-than-expected transparency of the Universe at extreme energies. These observations cannot be explained by standard EBL absorption alone; moreover, neither Lorentz invariance violation (LIV) nor photon–axion-like particle (ALP) oscillations, when considered in isolation, appear sufficient to account for the survival of such photons over cosmological distances. In this work, we propose a joint propagation scenario that incorporates photon–ALP mixing in astrophysical magnetic fields together with subluminal quadratic LIV corrections to the γγ pair-production threshold. Applying this framework to the broadband gamma-ray spectrum of GRB 221009A, we show that ALPs with coupling (gaγ = 1.685 × 10−10 GeV−1) and mass (ma = 9.545 × 10−8 eV), combined with a quadratic LIV energy scale (ELIV,2 = 1.30 × 10−7EPl) adopted from the literature, can significantly enhance the photon survival probability in the energy range (10–300) TeV. The resulting enhancement exceeds that obtained from either ALP mixing or LIV effects alone. These results indicate that a combined ALP–LIV scenario may provide a viable interpretation of the extreme-energy gamma-ray observations of GRB 221009A and highlight the potential of VHE gamma-ray measurements as probes of physics beyond the Standard Model.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"67 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4d43
Adam B. Mantz, Anthony M. Flores, Taweewat Somboonpanyakul, Steven W. Allen, R. Glenn Morris, Abigail Y. Pan and Haley R. Stueber
With the goal of extracting as much information as possible from Chandra and XMM-Newton observations of faint, diffuse sources such as galaxy clusters, as well as those of future X-ray telescopes, we present a strategy for forward modeling all of the foreground and background signals present in these data. This work leverages widespread efforts to understand the soft X-ray emission from the Galaxy, as well as the cosmic X-ray background and instrument-specific, particle-induced backgrounds. Statistically, a forward model of the foregrounds and backgrounds is preferable to alternatives because it requires no binning of the data, and allows for straightforward marginalization over systematic uncertainties. We apply these methods to several galaxy clusters at intermediate-to-high redshifts, spanning a range of masses and morphologies, using Chandra and/or XMM-Newton data. Our results suggest a modest improvement even for relatively bright clusters at these redshifts, and more substantial advantages in the high-redshift, low-surface-brightness regime. We also discuss and provide a simple correction for a time-dependent miscalibration of the Chandra advanced CCD imaging spectrometer detectors identified in archival galaxy cluster data.
{"title":"Ruminations Upon the Modeling of X-Ray Foregrounds, Backgrounds, and Faint Sources","authors":"Adam B. Mantz, Anthony M. Flores, Taweewat Somboonpanyakul, Steven W. Allen, R. Glenn Morris, Abigail Y. Pan and Haley R. Stueber","doi":"10.3847/1538-4357/ae4d43","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4d43","url":null,"abstract":"With the goal of extracting as much information as possible from Chandra and XMM-Newton observations of faint, diffuse sources such as galaxy clusters, as well as those of future X-ray telescopes, we present a strategy for forward modeling all of the foreground and background signals present in these data. This work leverages widespread efforts to understand the soft X-ray emission from the Galaxy, as well as the cosmic X-ray background and instrument-specific, particle-induced backgrounds. Statistically, a forward model of the foregrounds and backgrounds is preferable to alternatives because it requires no binning of the data, and allows for straightforward marginalization over systematic uncertainties. We apply these methods to several galaxy clusters at intermediate-to-high redshifts, spanning a range of masses and morphologies, using Chandra and/or XMM-Newton data. Our results suggest a modest improvement even for relatively bright clusters at these redshifts, and more substantial advantages in the high-redshift, low-surface-brightness regime. We also discuss and provide a simple correction for a time-dependent miscalibration of the Chandra advanced CCD imaging spectrometer detectors identified in archival galaxy cluster data.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"55 11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4a23
Hyeonyong Kim, Ji-hoon Kim, Minyong Jung, Santi Roca-Fàbrega, Daniel Ceverino, Pablo Granizo, Kentaro Nagamine, Joel R. Primack, Héctor Velázquez, Kirk S. S. Barrow, Robert Feldmann, Keita Fukushima, Lucio Mayer, Boon Kiat Oh, Johnny W. Powell, Tom Abel, Oscar Agertz, Chaerin Jeong, Alessandro Lupi, Yuri Oku, Thomas R. Quinn, Yves Revaz, Ramón Rodríguez-Cardoso, Ikkoh Shimizu, Romain Teyssier and AGORA COLLABORATION
Recent observations from the James Webb Space Telescope have revealed unexpectedly luminous galaxies, exhibiting stellar masses and luminosities significantly higher than predicted by theoretical models at Cosmic Dawn. In this study, we present a suite of cosmological zoomed-in simulations targeting high-redshift (z ≥ 10) galaxies with dark matter halo masses in the range 1010–1011M⊙ at z = 10, using state-of-the-art galaxy formation simulation codes (Enzo, Ramses, Changa, Gadget-3, Gadget-4, and Gizmo). This study aims to evaluate the convergence of the participating codes and their reproducibility of high-redshift galaxies with the galaxy formation model calibrated at relatively low redshift, without additional physics for high-redshift environments. The subgrid physics follows the AGORA CosmoRun framework, with adjustments to resolution and initial conditions to emulate similar physical environments in the early Universe. The participating codes show consistent results for key galaxy properties (e.g., stellar mass), but also reveal notable differences (e.g., metallicity), indicating that galaxy properties at high redshifts are highly sensitive to the feedback implementation of the simulation. Massive halos (Mhalo≥5 × 1010M⊙ at z = 10) succeed in reproducing observed stellar masses, metallicities, and UV luminosities at 10 ≤ z ≤ 12 without requiring additional subgrid physics, but tend to underpredict those properties at higher redshift. We also find that varying the dust-to-metal ratio modestly affects UV luminosity of simulated galaxies, whereas the absence of dust significantly enhances it. In future work, higher-resolution simulations will be conducted to better understand the formation and evolution of galaxies at Cosmic Dawn.
{"title":"The AGORA High-resolution Galaxy Simulations Comparison Project. X. Formation and Evolution of Galaxies at the High-redshift Frontier","authors":"Hyeonyong Kim, Ji-hoon Kim, Minyong Jung, Santi Roca-Fàbrega, Daniel Ceverino, Pablo Granizo, Kentaro Nagamine, Joel R. Primack, Héctor Velázquez, Kirk S. S. Barrow, Robert Feldmann, Keita Fukushima, Lucio Mayer, Boon Kiat Oh, Johnny W. Powell, Tom Abel, Oscar Agertz, Chaerin Jeong, Alessandro Lupi, Yuri Oku, Thomas R. Quinn, Yves Revaz, Ramón Rodríguez-Cardoso, Ikkoh Shimizu, Romain Teyssier and AGORA COLLABORATION","doi":"10.3847/1538-4357/ae4a23","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4a23","url":null,"abstract":"Recent observations from the James Webb Space Telescope have revealed unexpectedly luminous galaxies, exhibiting stellar masses and luminosities significantly higher than predicted by theoretical models at Cosmic Dawn. In this study, we present a suite of cosmological zoomed-in simulations targeting high-redshift (z ≥ 10) galaxies with dark matter halo masses in the range 1010–1011M⊙ at z = 10, using state-of-the-art galaxy formation simulation codes (Enzo, Ramses, Changa, Gadget-3, Gadget-4, and Gizmo). This study aims to evaluate the convergence of the participating codes and their reproducibility of high-redshift galaxies with the galaxy formation model calibrated at relatively low redshift, without additional physics for high-redshift environments. The subgrid physics follows the AGORA CosmoRun framework, with adjustments to resolution and initial conditions to emulate similar physical environments in the early Universe. The participating codes show consistent results for key galaxy properties (e.g., stellar mass), but also reveal notable differences (e.g., metallicity), indicating that galaxy properties at high redshifts are highly sensitive to the feedback implementation of the simulation. Massive halos (Mhalo≥5 × 1010M⊙ at z = 10) succeed in reproducing observed stellar masses, metallicities, and UV luminosities at 10 ≤ z ≤ 12 without requiring additional subgrid physics, but tend to underpredict those properties at higher redshift. We also find that varying the dust-to-metal ratio modestly affects UV luminosity of simulated galaxies, whereas the absence of dust significantly enhances it. In future work, higher-resolution simulations will be conducted to better understand the formation and evolution of galaxies at Cosmic Dawn.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"414 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4e26
Patrick Tremblay, Alain Beauchamp, Pierre Bergeron and Antoine Bédard
The study of Stark broadening of neutral helium lines, despite significant advances over recent decades, has not led to updated large grids of helium line profiles relevant to the spectroscopic study of helium-rich stars. While the semi-analytical approach based on the standard Stark broadening theory is efficient for generating such grids, it presents challenges in incorporating additional physical effects into the model. Motivated by recent studies that highlight potential issues with line profiles in the context of white dwarf stars, this paper leverages advances in computer simulations to create a new grid of line profiles for 13 neutral helium lines in the optical range. These profiles cover densities ranging from 1014 to 6 × 1017 cm−3 and temperatures from 10,000 to 40,000 K, with the exception of the narrower He iλ4713 line, for which the profile grid begins at 1015.5 cm−3. The primary goal of this research is to present the new grid and compare it with both the semi-analytical approach and other simulation results. By doing so, corrections to the previous grid will be explored, providing a foundation for future studies that utilize this updated grid. We also examine the impact of these new profiles on the determination of physical parameters for a range of astrophysical objects, including DB white dwarfs and other helium-rich stars.
{"title":"Improved Stark-broadened Profiles for Neutral Helium Lines Using Computer Simulations","authors":"Patrick Tremblay, Alain Beauchamp, Pierre Bergeron and Antoine Bédard","doi":"10.3847/1538-4357/ae4e26","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4e26","url":null,"abstract":"The study of Stark broadening of neutral helium lines, despite significant advances over recent decades, has not led to updated large grids of helium line profiles relevant to the spectroscopic study of helium-rich stars. While the semi-analytical approach based on the standard Stark broadening theory is efficient for generating such grids, it presents challenges in incorporating additional physical effects into the model. Motivated by recent studies that highlight potential issues with line profiles in the context of white dwarf stars, this paper leverages advances in computer simulations to create a new grid of line profiles for 13 neutral helium lines in the optical range. These profiles cover densities ranging from 1014 to 6 × 1017 cm−3 and temperatures from 10,000 to 40,000 K, with the exception of the narrower He iλ4713 line, for which the profile grid begins at 1015.5 cm−3. The primary goal of this research is to present the new grid and compare it with both the semi-analytical approach and other simulation results. By doing so, corrections to the previous grid will be explored, providing a foundation for future studies that utilize this updated grid. We also examine the impact of these new profiles on the determination of physical parameters for a range of astrophysical objects, including DB white dwarfs and other helium-rich stars.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"19 12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4d36
Yuxi Jiang, Q.Y. Peng, Fan Li, Xin Wang, Xing Lu, Xueqing Fang and Jian Chen
We present a method for obtaining high-precision asteroid astrometry from a ground-based optical telescope. While the observation of a faint asteroid often employs a single clear filter to ensure a high signal-to-noise ratio, this strategy introduces strong differential chromatic refraction (DCR). We demonstrate our method based on a sample of 16 asteroids observed via a single clear filter, performing data reduction with a newly published DCR calibration model. The approach employs multinight observations to derive the asteroid’s color index (CI) and correct its positional residuals after a suitable plate-constant model solution. For the full sample, the standard deviations of residuals relative to the Jet Propulsion Laboratory ephemeris were reduced to approximately 0 02 in each direction. This precision represents an improvement of approximately 1 order of magnitude over the astrometric precision typically achieved by major surveys. Furthermore, the derived CIs show general consistency with previous photometric records. Our method provides a robust calibration strategy for future surveys, enabling high-sensitivity broadband observations to achieve high astrometric precision.
{"title":"A Practical Method for Improving an Asteroid’s Astrometric Measurement","authors":"Yuxi Jiang, Q.Y. Peng, Fan Li, Xin Wang, Xing Lu, Xueqing Fang and Jian Chen","doi":"10.3847/1538-4357/ae4d36","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4d36","url":null,"abstract":"We present a method for obtaining high-precision asteroid astrometry from a ground-based optical telescope. While the observation of a faint asteroid often employs a single clear filter to ensure a high signal-to-noise ratio, this strategy introduces strong differential chromatic refraction (DCR). We demonstrate our method based on a sample of 16 asteroids observed via a single clear filter, performing data reduction with a newly published DCR calibration model. The approach employs multinight observations to derive the asteroid’s color index (CI) and correct its positional residuals after a suitable plate-constant model solution. For the full sample, the standard deviations of residuals relative to the Jet Propulsion Laboratory ephemeris were reduced to approximately 0 02 in each direction. This precision represents an improvement of approximately 1 order of magnitude over the astrometric precision typically achieved by major surveys. Furthermore, the derived CIs show general consistency with previous photometric records. Our method provides a robust calibration strategy for future surveys, enabling high-sensitivity broadband observations to achieve high astrometric precision.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4ec3
Laurel White, Michael McDonald, Steven W. Allen, Marshall W. Bautz, Michael Calzadilla, Gordon P. Garmire, Julie Hlavacek-Larrondo, Ralph Kraft, Adam B. Mantz, Taweewat Somboonpanyakul and Alexey Vikhlinin
With rapid improvements in the assembly of large samples of galaxy clusters, we are approaching the ability to study clusters at z ≳ 2. Evolutionary studies comparing these distant clusters to the clusters in our local Universe depend heavily on the reliability of low-redshift cluster samples, most of which are subject to X-ray selection effects, biasing them to relaxed, cool-core clusters. Here, we introduce the Cluster Evolutionary Reference Ensemble at Low-z (CEREAL) sample, composed of Chandra X-ray observations of 169 galaxy clusters that have been selected from the Planck Sunyaev–Zel’dovich catalog. CEREAL has a simple and well-understood selection function, spans an order of magnitude in mass at z ∼ 0.15, and has uniform, high-resolution X-ray follow-up. We present the full sample and provide results based on X-ray surface brightness properties, finding significantly more non-cool-core systems than in X-ray-selected samples. We use surface brightness concentration (cSB) as a proxy for cool-core strength and centroid shift (w) to measure dynamical state. Over the full sample, we find a cool-core (cSB > 0.075) fraction of , a strong cool-core (cSB > 0.155) fraction of , and a dynamically relaxed (w < 0.01) fraction of . We find no mass dependence in the fraction of clusters that appear relaxed or have cool cores. We quantify the rarity of X-ray-bright central point sources (Lnuc, 2−10 keV > 1043 erg s−1), finding them to be intrinsically rare ( % of massive, low-z clusters) with a notable increase in occurrence rate at the centers of cool cores.
{"title":"The Cluster Evolutionary Reference Ensemble at Low-z (CEREAL) Sample of Galaxy Clusters. I. X-Ray Morphological Properties and Demographics","authors":"Laurel White, Michael McDonald, Steven W. Allen, Marshall W. Bautz, Michael Calzadilla, Gordon P. Garmire, Julie Hlavacek-Larrondo, Ralph Kraft, Adam B. Mantz, Taweewat Somboonpanyakul and Alexey Vikhlinin","doi":"10.3847/1538-4357/ae4ec3","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4ec3","url":null,"abstract":"With rapid improvements in the assembly of large samples of galaxy clusters, we are approaching the ability to study clusters at z ≳ 2. Evolutionary studies comparing these distant clusters to the clusters in our local Universe depend heavily on the reliability of low-redshift cluster samples, most of which are subject to X-ray selection effects, biasing them to relaxed, cool-core clusters. Here, we introduce the Cluster Evolutionary Reference Ensemble at Low-z (CEREAL) sample, composed of Chandra X-ray observations of 169 galaxy clusters that have been selected from the Planck Sunyaev–Zel’dovich catalog. CEREAL has a simple and well-understood selection function, spans an order of magnitude in mass at z ∼ 0.15, and has uniform, high-resolution X-ray follow-up. We present the full sample and provide results based on X-ray surface brightness properties, finding significantly more non-cool-core systems than in X-ray-selected samples. We use surface brightness concentration (cSB) as a proxy for cool-core strength and centroid shift (w) to measure dynamical state. Over the full sample, we find a cool-core (cSB > 0.075) fraction of , a strong cool-core (cSB > 0.155) fraction of , and a dynamically relaxed (w < 0.01) fraction of . We find no mass dependence in the fraction of clusters that appear relaxed or have cool cores. We quantify the rarity of X-ray-bright central point sources (Lnuc, 2−10 keV > 1043 erg s−1), finding them to be intrinsically rare ( % of massive, low-z clusters) with a notable increase in occurrence rate at the centers of cool cores.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"109 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-27DOI: 10.3847/1538-4357/ae4b32
Xin Sheng, Bennett Link, Matthew E. Caplan and Yuri Levin
We study the superfluid vortex motion in the neutron star inner crust through direct 3D simulations of the coupled dynamics of the vortex and the nuclear lattice. We demonstrate the pinning of an initially moving vortex to the lattice through the excitation of lattice vibrations and show that the efficiency of this process is higher for attractive than for repulsive nucleus–vortex interactions. We explore the unpinning of a vortex under the action of the applied Magnus force and find that it is influenced by multiple parameters, including the sign of the pinning force, the lattice orientation, composition, temperature, and the energy of the pinning to individual nuclei. In lattices with multiple grains, the unpinning transition is triggered inside the grains with weaker pinning, propagates along the vortex (mediated by the excited Kelvin waves), and crosses into grains with stronger pinning. This is likely to effectively decrease the critical force at which vortices unpin and to produce extended regions of unpinned vorticity. The shearing of the crust lattice (e.g., by a starquake) initiates the unpinning of the vortices that are crossing the slip plane. A close encounter of an unpinned vortex with a pinned vortex would cause the latter to unpin, perhaps initiating an unpinning avalanche of many vortices.
{"title":"Vortex Dynamics in the Neutron Star Inner Crust","authors":"Xin Sheng, Bennett Link, Matthew E. Caplan and Yuri Levin","doi":"10.3847/1538-4357/ae4b32","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4b32","url":null,"abstract":"We study the superfluid vortex motion in the neutron star inner crust through direct 3D simulations of the coupled dynamics of the vortex and the nuclear lattice. We demonstrate the pinning of an initially moving vortex to the lattice through the excitation of lattice vibrations and show that the efficiency of this process is higher for attractive than for repulsive nucleus–vortex interactions. We explore the unpinning of a vortex under the action of the applied Magnus force and find that it is influenced by multiple parameters, including the sign of the pinning force, the lattice orientation, composition, temperature, and the energy of the pinning to individual nuclei. In lattices with multiple grains, the unpinning transition is triggered inside the grains with weaker pinning, propagates along the vortex (mediated by the excited Kelvin waves), and crosses into grains with stronger pinning. This is likely to effectively decrease the critical force at which vortices unpin and to produce extended regions of unpinned vorticity. The shearing of the crust lattice (e.g., by a starquake) initiates the unpinning of the vortices that are crossing the slip plane. A close encounter of an unpinned vortex with a pinned vortex would cause the latter to unpin, perhaps initiating an unpinning avalanche of many vortices.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147519234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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