Pub Date : 2026-04-07DOI: 10.3847/1538-4357/ae5494
Ernest Chang, Dae-Sik Moon, Patrick Sandoval, Matthew C. H. Leung, Yuan Qi Ni, Santiago González-Gaitán, Youngdae Lee, Hong Soo Park, Sang Chul Kim and Nan Jiang
We present photometric and spectroscopic observations of a luminous, long-lasting (LLL) Type IIn supernova (SN) KSP-SN-2020f found in a dwarf host galaxy at z = 0.1 from the KMTNet SN Program. Our high-cadence, multicolor (BVi) monitoring observations constrain the epoch of first-light to ∼5 hr prior to first detection under the power-law assumption of early light. The source shows fast evolution across the peak of MV ≃ −19.54 mag, with a rise time of 7.9 days followed by a rapid linear decline of 1.9 mag in 50 days. The fast near-peak evolution and large luminosities require excess emission, such as interactions with circumstellar material (CSM), in addition to SN shock cooling emission. Early blue colors and luminous (MV ≃ −16) late-time evolution (≳200 days) are slower than 56Co radioactive decay, indicating continuous CSM interactions throughout the SN’s entire evolution. Its Hα emission consists of multiple components indicative of substantial CSM interactions with an estimated mass loss rate of M⊙ yr−1. The large wind velocity (∼260 km s−1) and mass loss rate are compatible with an luminous blue variable (LBV)-like progenitor for the source. This study provides a first look at the infant-phase evolution of an LLL Type IIn SN, demonstrating that rapid near-peak evolution can coexist with slow late-time evolution, and also suggesting that LBV-like progenitors can produce Type IIn SNe with fast early evolution.
{"title":"Infant Core-collapse Supernova with Circumstellar Interactions from KMTNet. II. Luminous, Long-lasting Case of KSP-SN-2020f","authors":"Ernest Chang, Dae-Sik Moon, Patrick Sandoval, Matthew C. H. Leung, Yuan Qi Ni, Santiago González-Gaitán, Youngdae Lee, Hong Soo Park, Sang Chul Kim and Nan Jiang","doi":"10.3847/1538-4357/ae5494","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5494","url":null,"abstract":"We present photometric and spectroscopic observations of a luminous, long-lasting (LLL) Type IIn supernova (SN) KSP-SN-2020f found in a dwarf host galaxy at z = 0.1 from the KMTNet SN Program. Our high-cadence, multicolor (BVi) monitoring observations constrain the epoch of first-light to ∼5 hr prior to first detection under the power-law assumption of early light. The source shows fast evolution across the peak of MV ≃ −19.54 mag, with a rise time of 7.9 days followed by a rapid linear decline of 1.9 mag in 50 days. The fast near-peak evolution and large luminosities require excess emission, such as interactions with circumstellar material (CSM), in addition to SN shock cooling emission. Early blue colors and luminous (MV ≃ −16) late-time evolution (≳200 days) are slower than 56Co radioactive decay, indicating continuous CSM interactions throughout the SN’s entire evolution. Its Hα emission consists of multiple components indicative of substantial CSM interactions with an estimated mass loss rate of M⊙ yr−1. The large wind velocity (∼260 km s−1) and mass loss rate are compatible with an luminous blue variable (LBV)-like progenitor for the source. This study provides a first look at the infant-phase evolution of an LLL Type IIn SN, demonstrating that rapid near-peak evolution can coexist with slow late-time evolution, and also suggesting that LBV-like progenitors can produce Type IIn SNe with fast early evolution.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"244 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147630841","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 : 2026-04-07DOI: 10.3847/1538-4357/ae48ea
Naoki Seto
We present the first observational test of the hybrid ring strategy, a general coordinated signaling scheme proposed by N. Seto, which provides a practical Schelling point realization for interstellar signaling. We use the exceptionally bright GRB 221009A as the anchoring flash for the scheme, together with the accurately measured distance to the Galactic center. This combination provides a high-precision relation linking sky position to a tightly constrained arrival-time window. TESS observed the region around the gamma-ray burst nearly continuously for ∼50 days in 2024, providing survey light curves that enable a direct test of this scheme with sharply predicted arrival-time windows of ∼3.4 days. Among 58 carefully selected stars, we identify two that show noticeable single-time-bin brightenings inside their predicted windows (where each time bin corresponds to a 200 s integrated TESS exposure). In both cases the brightenings coincide with excursions in at least one nearby star and are therefore most consistent with instrumental origins. This test demonstrates that the hybrid ring strategy is practical with existing survey data and could serve as a promising basis for future technosignature searches.
{"title":"A TESS Test of the Hybrid Ring Strategy for Technosignature Searches Using GRB 221009A","authors":"Naoki Seto","doi":"10.3847/1538-4357/ae48ea","DOIUrl":"https://doi.org/10.3847/1538-4357/ae48ea","url":null,"abstract":"We present the first observational test of the hybrid ring strategy, a general coordinated signaling scheme proposed by N. Seto, which provides a practical Schelling point realization for interstellar signaling. We use the exceptionally bright GRB 221009A as the anchoring flash for the scheme, together with the accurately measured distance to the Galactic center. This combination provides a high-precision relation linking sky position to a tightly constrained arrival-time window. TESS observed the region around the gamma-ray burst nearly continuously for ∼50 days in 2024, providing survey light curves that enable a direct test of this scheme with sharply predicted arrival-time windows of ∼3.4 days. Among 58 carefully selected stars, we identify two that show noticeable single-time-bin brightenings inside their predicted windows (where each time bin corresponds to a 200 s integrated TESS exposure). In both cases the brightenings coincide with excursions in at least one nearby star and are therefore most consistent with instrumental origins. This test demonstrates that the hybrid ring strategy is practical with existing survey data and could serve as a promising basis for future technosignature searches.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147630801","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 : 2026-04-07DOI: 10.3847/1538-4357/ae552d
Huajian Wang, Xiaodian Chen and Shu Wang
Cepheids are fundamental distance indicators, playing a crucial role not only in the cosmic distance ladder but also in mapping the structure, kinematics, and extinction properties of the Milky Way. Using high-precision photometry and parallaxes from Gaia Data Release 3, we identify a significant anticorrelation between the G-band extinction coefficient and reddening for Galactic Cepheids, quantified as RG = 1.918 ± 0.060 − (0.106 ± 0.022) E(GBP − GRP). We propose that this anticorrelation arises from the combination of the nonlinear effects inherent to the broad Gaia bands and the RV variations caused by the diverse interstellar medium. Adopting a fixed RG would not only lead to an overestimation of the metallicity dependence of Cepheid luminosities but also systematically underestimate the distances to highly reddened Cepheids. Moreover, the strong reddening dependence of RG makes the Wesenheit function based on it unsuitable for highly reddened Cepheids, since the definition of Wesenheit magnitudes requires a fixed extinction coefficient. In contrast, infrared-based distances, being less affected by nonlinear effects and insensitive to RV, provide the most reliable Cepheid distances at present. This work emphasizes the importance of accurately determining RV for Galactic Cepheids and accounting for nonlinear effects in distance measurements, particularly in the optical bands.
{"title":"The Dependence of the Extinction Coefficient on Reddening for Galactic Cepheids","authors":"Huajian Wang, Xiaodian Chen and Shu Wang","doi":"10.3847/1538-4357/ae552d","DOIUrl":"https://doi.org/10.3847/1538-4357/ae552d","url":null,"abstract":"Cepheids are fundamental distance indicators, playing a crucial role not only in the cosmic distance ladder but also in mapping the structure, kinematics, and extinction properties of the Milky Way. Using high-precision photometry and parallaxes from Gaia Data Release 3, we identify a significant anticorrelation between the G-band extinction coefficient and reddening for Galactic Cepheids, quantified as RG = 1.918 ± 0.060 − (0.106 ± 0.022) E(GBP − GRP). We propose that this anticorrelation arises from the combination of the nonlinear effects inherent to the broad Gaia bands and the RV variations caused by the diverse interstellar medium. Adopting a fixed RG would not only lead to an overestimation of the metallicity dependence of Cepheid luminosities but also systematically underestimate the distances to highly reddened Cepheids. Moreover, the strong reddening dependence of RG makes the Wesenheit function based on it unsuitable for highly reddened Cepheids, since the definition of Wesenheit magnitudes requires a fixed extinction coefficient. In contrast, infrared-based distances, being less affected by nonlinear effects and insensitive to RV, provide the most reliable Cepheid distances at present. This work emphasizes the importance of accurately determining RV for Galactic Cepheids and accounting for nonlinear effects in distance measurements, particularly in the optical bands.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147630831","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 : 2026-04-07DOI: 10.3847/1538-4357/ae5536
Ya-Wen Xiao, Jian-Fu Zhang and Alex Lazarian
Based on multifrequency radio polarization survey datasets, we investigate the spectral characteristics of the Galactic interstellar medium (ISM) using the polarization frequency analysis (PFA) method, referred to as polarization variance. By comparing this novel PFA technique with the traditional power spectrum approach, and by cross-examining data from two distinct surveys, we aim to reinforce the robustness of our findings. Our analysis reveals that the ISM scaling slope in the Galactic disk is steeper than the classic Kolmogorov slope, whereas the ISM scaling slope in the Galactic halo aligns with the Kolmogorov slope. We suggest a distinct turbulence cascade process operating in the Galactic halo compared to the Galactic disk.
{"title":"Revealing the Spectral Properties of the Galactic Interstellar Medium by Survey Observations","authors":"Ya-Wen Xiao, Jian-Fu Zhang and Alex Lazarian","doi":"10.3847/1538-4357/ae5536","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5536","url":null,"abstract":"Based on multifrequency radio polarization survey datasets, we investigate the spectral characteristics of the Galactic interstellar medium (ISM) using the polarization frequency analysis (PFA) method, referred to as polarization variance. By comparing this novel PFA technique with the traditional power spectrum approach, and by cross-examining data from two distinct surveys, we aim to reinforce the robustness of our findings. Our analysis reveals that the ISM scaling slope in the Galactic disk is steeper than the classic Kolmogorov slope, whereas the ISM scaling slope in the Galactic halo aligns with the Kolmogorov slope. We suggest a distinct turbulence cascade process operating in the Galactic halo compared to the Galactic disk.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"108 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147630832","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 : 2026-04-06DOI: 10.3847/1538-4357/ae4d46
Jed McKinney, Miriam Eleazer, Alexandra Pope, Anna Sajina, Stacey Alberts, Meredith Stone, Leonid Sajkov, Virginia Vanicek, Allison Kirkpatrick, Thomas S.-Y. Lai, Caitlin M. Casey, Lee Armus, Tanio Díaz- Santos, Andrew Korkus, Olivia Cooper, Lindsay R. House, Hollis Akins, Erini Lambrides, Arianna S. Long and Lin Yan
We present a large spectroscopic survey with JWST’s Mid-Infrared Instrument Low Resolution Spectrometer (LRS) targeting 37 infrared-bright galaxies between z = 0.65–2.46 with infrared luminosities and . Targets were taken from a Spitzer 24 μm selected sample with archival spectroscopy from the Infrared Spectrograph (IRS) and include a mix of star-forming galaxies and dust-obscured active galactic nuclei. By combining IRS with the increased sensitivity of LRS, we expand the range of spectral features observed between 5 and 30 μm for every galaxy in our sample. In this paper, we outline the sample selection, reduction of the JWST data, extraction of the 1D spectra, and polycyclic aromatic hydrocarbon (PAH) feature measurements from λrest = 3.3–11.3 μm. In the JWST spectra, we detect PAH emission features at 3.3–5.3 μm, as well as Paschen and Brackett lines. The 3.3 μm feature can be as bright as 1% of the 8–1000 μm infrared luminosity and exhibits a tight correlation with the dust-obscured star formation rate. We detect absorption features from CO gas, CO2 ice, H2O ice, and aliphatic dust. From the joint JWST and Spitzer analysis, we find that the 11.3/3.3 μm PAH ratios are on average three times higher than that of local luminous infrared galaxies. This is interpreted as evidence that the PAH grains are larger at z ∼ 1–2. The size distribution may be affected by coagulation of grains due to high gas densities and low temperatures. These conditions are supported by the observation of strong water ice absorption at 3.05 μm and can lower stellar radiative feedback because large PAHs transmit less energy per photon into the interstellar medium.
{"title":"A JWST MIRI LRS Survey of 37 Massive Star-forming Galaxies and Active Galactic Nuclei at Cosmic Noon: Overview and First Results","authors":"Jed McKinney, Miriam Eleazer, Alexandra Pope, Anna Sajina, Stacey Alberts, Meredith Stone, Leonid Sajkov, Virginia Vanicek, Allison Kirkpatrick, Thomas S.-Y. Lai, Caitlin M. Casey, Lee Armus, Tanio Díaz- Santos, Andrew Korkus, Olivia Cooper, Lindsay R. House, Hollis Akins, Erini Lambrides, Arianna S. Long and Lin Yan","doi":"10.3847/1538-4357/ae4d46","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4d46","url":null,"abstract":"We present a large spectroscopic survey with JWST’s Mid-Infrared Instrument Low Resolution Spectrometer (LRS) targeting 37 infrared-bright galaxies between z = 0.65–2.46 with infrared luminosities and . Targets were taken from a Spitzer 24 μm selected sample with archival spectroscopy from the Infrared Spectrograph (IRS) and include a mix of star-forming galaxies and dust-obscured active galactic nuclei. By combining IRS with the increased sensitivity of LRS, we expand the range of spectral features observed between 5 and 30 μm for every galaxy in our sample. In this paper, we outline the sample selection, reduction of the JWST data, extraction of the 1D spectra, and polycyclic aromatic hydrocarbon (PAH) feature measurements from λrest = 3.3–11.3 μm. In the JWST spectra, we detect PAH emission features at 3.3–5.3 μm, as well as Paschen and Brackett lines. The 3.3 μm feature can be as bright as 1% of the 8–1000 μm infrared luminosity and exhibits a tight correlation with the dust-obscured star formation rate. We detect absorption features from CO gas, CO2 ice, H2O ice, and aliphatic dust. From the joint JWST and Spitzer analysis, we find that the 11.3/3.3 μm PAH ratios are on average three times higher than that of local luminous infrared galaxies. This is interpreted as evidence that the PAH grains are larger at z ∼ 1–2. The size distribution may be affected by coagulation of grains due to high gas densities and low temperatures. These conditions are supported by the observation of strong water ice absorption at 3.05 μm and can lower stellar radiative feedback because large PAHs transmit less energy per photon into the interstellar medium.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147625619","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 : 2026-04-06DOI: 10.3847/1538-4357/ae4979
Shing-Chi Leung, Seth Walther, Henry Yerdon, Ken’ichi Nomoto and Aurora Simionescu
The legacy Hitomi telescope has delivered the precise measurements of the chemical abundances in the Perseus Cluster, covering the Si-group (Si, S, Ar, Ca) and Fe-group elements (Cr, Mn, Ni). In Paper I, we examined the role of convection parameters and presented new core-collapse supernova (CCSN) explosion models at solar metallicity, which fit the observed abundance pattern. In this article, we extend our calculation for the stellar evolutionary models and CCSN models of the initial mass 15–60M⊙ and the metallicity Z = 0 − Z⊙. The detailed pre- and postexplosion chemical profiles are calculated with a large postprocessing network to capture the production of α-chain elements (e.g., Si, S, Ar), odd-number elements (e.g., P, K, Cl), and iron group elements (e.g., Mn, Ni). We study the role of CCSNe in the production of these elements. We compare the galactic chemical evolution model based on the nucleosynthesis yield of the new massive stars and other yield tables from the literature. For each supernova yield, we perform parameter surveys and search for configurations that produce the best-fit model and best-rate model using the Perseus Cluster as the reference. From the survey, we study how individual chemical elements affect the contributions of massive stars and Type Ia supernovae in the cosmic chemical enrichment history.
{"title":"Revisiting the Perseus Cluster. II. Metallicity-dependence of Massive Stars and Chemical Enrichment History","authors":"Shing-Chi Leung, Seth Walther, Henry Yerdon, Ken’ichi Nomoto and Aurora Simionescu","doi":"10.3847/1538-4357/ae4979","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4979","url":null,"abstract":"The legacy Hitomi telescope has delivered the precise measurements of the chemical abundances in the Perseus Cluster, covering the Si-group (Si, S, Ar, Ca) and Fe-group elements (Cr, Mn, Ni). In Paper I, we examined the role of convection parameters and presented new core-collapse supernova (CCSN) explosion models at solar metallicity, which fit the observed abundance pattern. In this article, we extend our calculation for the stellar evolutionary models and CCSN models of the initial mass 15–60M⊙ and the metallicity Z = 0 − Z⊙. The detailed pre- and postexplosion chemical profiles are calculated with a large postprocessing network to capture the production of α-chain elements (e.g., Si, S, Ar), odd-number elements (e.g., P, K, Cl), and iron group elements (e.g., Mn, Ni). We study the role of CCSNe in the production of these elements. We compare the galactic chemical evolution model based on the nucleosynthesis yield of the new massive stars and other yield tables from the literature. For each supernova yield, we perform parameter surveys and search for configurations that produce the best-fit model and best-rate model using the Perseus Cluster as the reference. From the survey, we study how individual chemical elements affect the contributions of massive stars and Type Ia supernovae in the cosmic chemical enrichment history.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"191 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147625624","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 : 2026-04-06DOI: 10.3847/1538-4357/ae5181
Sonika Piridi, Ranjan Kumar, Divya Pandey and Ananta C. Pradhan
We used observations obtained with the Ultraviolet Imaging Telescope on board the AstroSat satellite to measure the integrated far-ultraviolet (FUV) and optical (V) magnitudes of 30 Galactic globular clusters (GCs). We classified the UV-bright evolved stellar populations of the GCs using FUV−V versus FUV color–magnitude diagrams (CMDs) and BaSTI-IAC isochrones and subsequently quantified their contributions to the total integrated FUV emissions. We found that the horizontal branch (HB) and post-HB stars contribute ∼40%–45% to the total FUV emission of GCs, while the contribution of blue straggler stars is only ∼3%. The HB stars especially dominate the UV budget of the metal-poor clusters. The observed spread in FUV–optical color in the color–color diagram supports the phenomenon that the UV upturn of early-type galaxies is due to the evolved stars. We studied for the first time the variation of integrated FUV magnitudes and colors with several cluster parameters in the core, intermediate, outer, and tidal regions, such as the fraction of second-generation stars, helium mass fraction, HB morphology, and mass of the GCs. We found that the GCs with a higher second-generation star fraction, helium mass fraction, and cluster mass are brighter in all the regions. The GCs with bluer HB morphologies also have brighter and bluer FUV magnitudes in the core and intermediate regions. Metal-poor GCs show significantly bluer FUV−optical colors, consistent with a stronger contribution from hot evolved stars.
{"title":"Study of Integrated Far-ultraviolet Emissions from Galactic Globular Clusters Using AstroSat/UVIT Observations","authors":"Sonika Piridi, Ranjan Kumar, Divya Pandey and Ananta C. Pradhan","doi":"10.3847/1538-4357/ae5181","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5181","url":null,"abstract":"We used observations obtained with the Ultraviolet Imaging Telescope on board the AstroSat satellite to measure the integrated far-ultraviolet (FUV) and optical (V) magnitudes of 30 Galactic globular clusters (GCs). We classified the UV-bright evolved stellar populations of the GCs using FUV−V versus FUV color–magnitude diagrams (CMDs) and BaSTI-IAC isochrones and subsequently quantified their contributions to the total integrated FUV emissions. We found that the horizontal branch (HB) and post-HB stars contribute ∼40%–45% to the total FUV emission of GCs, while the contribution of blue straggler stars is only ∼3%. The HB stars especially dominate the UV budget of the metal-poor clusters. The observed spread in FUV–optical color in the color–color diagram supports the phenomenon that the UV upturn of early-type galaxies is due to the evolved stars. We studied for the first time the variation of integrated FUV magnitudes and colors with several cluster parameters in the core, intermediate, outer, and tidal regions, such as the fraction of second-generation stars, helium mass fraction, HB morphology, and mass of the GCs. We found that the GCs with a higher second-generation star fraction, helium mass fraction, and cluster mass are brighter in all the regions. The GCs with bluer HB morphologies also have brighter and bluer FUV magnitudes in the core and intermediate regions. Metal-poor GCs show significantly bluer FUV−optical colors, consistent with a stronger contribution from hot evolved stars.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147625679","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 : 2026-04-06DOI: 10.3847/1538-4357/ae5490
Nitya Agarwala, Weijie Sun, Gangkai Poh, Shan Wang, Andy Smith, James A. Slavin, Guan Le and James L. Burch
Flux ropes in space plasma can play an important role in particle acceleration. However, the mechanisms of electron energization and the resulting electron energy distribution associated with flux ropes are still not fully understood. This study examines a flux rope chain with four ion-scale flux ropes observed by the Magnetospheric Multiscale (MMS) mission in a turbulent plasma region in Earth’s magnetotail. We investigate the active electron acceleration mechanisms, including parallel electric fields, betatron acceleration, and magnetic curvature-driven Fermi-type acceleration, based on MMS’s four spacecraft in situ measurements. Our results demonstrate that Fermi acceleration is the dominant mechanism with betatron acceleration providing an important contribution. The electron energy spectra are further fitted by Kappa and Flattop distributions aiming to characterize the energy densities of thermal and suprathermal populations. It shows that although suprathermal electrons comprise only 10% of the number number density, they could contribute up to 30% of the total energy density. While the energy densities of both thermal and suprathermal electrons increase within the flux ropes, the relative portions of suprathermal electrons decrease. This suggests that flux rope could confine both thermal and suprathermal electrons; however, they are likely more efficient to energize thermal electrons.
{"title":"Electron Energization within an Ion-scale Flux Rope Chain in Earth’s Turbulent Magnetotail Plasma Sheet","authors":"Nitya Agarwala, Weijie Sun, Gangkai Poh, Shan Wang, Andy Smith, James A. Slavin, Guan Le and James L. Burch","doi":"10.3847/1538-4357/ae5490","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5490","url":null,"abstract":"Flux ropes in space plasma can play an important role in particle acceleration. However, the mechanisms of electron energization and the resulting electron energy distribution associated with flux ropes are still not fully understood. This study examines a flux rope chain with four ion-scale flux ropes observed by the Magnetospheric Multiscale (MMS) mission in a turbulent plasma region in Earth’s magnetotail. We investigate the active electron acceleration mechanisms, including parallel electric fields, betatron acceleration, and magnetic curvature-driven Fermi-type acceleration, based on MMS’s four spacecraft in situ measurements. Our results demonstrate that Fermi acceleration is the dominant mechanism with betatron acceleration providing an important contribution. The electron energy spectra are further fitted by Kappa and Flattop distributions aiming to characterize the energy densities of thermal and suprathermal populations. It shows that although suprathermal electrons comprise only 10% of the number number density, they could contribute up to 30% of the total energy density. While the energy densities of both thermal and suprathermal electrons increase within the flux ropes, the relative portions of suprathermal electrons decrease. This suggests that flux rope could confine both thermal and suprathermal electrons; however, they are likely more efficient to energize thermal electrons.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147625731","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 : 2026-04-06DOI: 10.3847/1538-4357/ae5235
Victoria A. Blackmon, Maura A. McLaughlin, De Zhao, Jianping Yuan, Qingdong Wu, Chen-Chen Miao, Meng-Yao Xue, Di Li and Wei-Wei Zhu
We present the results of Green Bank Telescope observations of two pulsars discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) during the 19-beam Commensal Radio Astronomy FasT Survey (CRAFTS). We highlight the first timing solutions, pulse profiles, flux densities, and polarization measurements at 820 MHz for PSR J0535–0231, with a spin period of 415 ms, and PSR J1816–0518, with a spin period of 1.93 s, from a year-long follow-up campaign. PSR J0535–0231 appears to be partially recycled, but isolated, and likely belongs to the class of disrupted recycled pulsars. We find that the two widely used electron density models, NE2001 and YMW16, both fall short of accurately modeling the line of sight to PSR J0535–0231, as the maximum dispersion measure (DM) predicted by both models is lower than the pulsar’s DM of 118.1 pc cm−3. Finally, we place both pulsar discoveries in the context of other FAST pulsars discovered in the CRAFTS survey and of the currently known pulsar population, in general, and discuss ways in which future FAST discoveries of faint, distant pulsars might facilitate the development of improved versions of the aforementioned electron density models in certain regions of our Galaxy.
{"title":"Discovery and Timing Follow-up of Two FAST-discovered Pulsars from the FAST CRAFTS Survey","authors":"Victoria A. Blackmon, Maura A. McLaughlin, De Zhao, Jianping Yuan, Qingdong Wu, Chen-Chen Miao, Meng-Yao Xue, Di Li and Wei-Wei Zhu","doi":"10.3847/1538-4357/ae5235","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5235","url":null,"abstract":"We present the results of Green Bank Telescope observations of two pulsars discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) during the 19-beam Commensal Radio Astronomy FasT Survey (CRAFTS). We highlight the first timing solutions, pulse profiles, flux densities, and polarization measurements at 820 MHz for PSR J0535–0231, with a spin period of 415 ms, and PSR J1816–0518, with a spin period of 1.93 s, from a year-long follow-up campaign. PSR J0535–0231 appears to be partially recycled, but isolated, and likely belongs to the class of disrupted recycled pulsars. We find that the two widely used electron density models, NE2001 and YMW16, both fall short of accurately modeling the line of sight to PSR J0535–0231, as the maximum dispersion measure (DM) predicted by both models is lower than the pulsar’s DM of 118.1 pc cm−3. Finally, we place both pulsar discoveries in the context of other FAST pulsars discovered in the CRAFTS survey and of the currently known pulsar population, in general, and discuss ways in which future FAST discoveries of faint, distant pulsars might facilitate the development of improved versions of the aforementioned electron density models in certain regions of our Galaxy.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147625675","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 : 2026-04-06DOI: 10.3847/1538-4357/ae5108
Guoyin Chen, Yang Guo, Qi Hao and Mingde Ding
The magnetic field in the solar corona cannot be observed routinely at present. Nonlinear force-free field (NLFFF) extrapolation serves as a crucial method for modeling the coronal magnetic configuration. We present a novel physics- reinforced generative adversarial network (PRO-GAN), an integrated deep learning framework designed to efficiently transform solar potential fields into corresponding NLFFFs while enforcing physical constraints to improve the result. This dual-phase framework synthesizes multifaceted integration, including the data-driven mapping relation acquisition, the constraint of physics equations, and supervision by a numerical solver. On the other hand, by incorporating a gradient penalty reinforced by a numerical method during the physics reinforcement training process, this approach resolves the inherent gradient conflicts in physics-informed neural networks from a novel perspective. The validity and efficiency of PRO-GAN have also been verified on the dataset and two analytic models.
{"title":"A Novel Way for Extrapolating the Solar Magnetic Field with PRO-GAN","authors":"Guoyin Chen, Yang Guo, Qi Hao and Mingde Ding","doi":"10.3847/1538-4357/ae5108","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5108","url":null,"abstract":"The magnetic field in the solar corona cannot be observed routinely at present. Nonlinear force-free field (NLFFF) extrapolation serves as a crucial method for modeling the coronal magnetic configuration. We present a novel physics- reinforced generative adversarial network (PRO-GAN), an integrated deep learning framework designed to efficiently transform solar potential fields into corresponding NLFFFs while enforcing physical constraints to improve the result. This dual-phase framework synthesizes multifaceted integration, including the data-driven mapping relation acquisition, the constraint of physics equations, and supervision by a numerical solver. On the other hand, by incorporating a gradient penalty reinforced by a numerical method during the physics reinforcement training process, this approach resolves the inherent gradient conflicts in physics-informed neural networks from a novel perspective. The validity and efficiency of PRO-GAN have also been verified on the dataset and two analytic models.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147625672","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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