Pub Date : 2026-04-01DOI: 10.3847/1538-4357/ae4c4c
Minami Yoshida, Toshifumi Shimizu, Shin Toriumi and Haruhisa Iijima
The evolution of the global solar magnetic field directly impacts the interplanetary magnetic field (IMF). During the solar maximum of Cycle 24, the monthly averaged IMF strength doubled over five Carrington rotations (CRs) in late 2014. To understand the physical origin of this increase, we investigate the temporal evolution of open magnetic flux resulting from the emergence and decay of bipolar magnetic regions (BMRs). Using surface flux transport and potential field source surface models, we simulated how BMR characteristics, spatial distributions, and interaction with background magnetic fields affect open flux evolution. Our simulation confirmed that the relative configuration of BMRs can either inhibit open flux expansion via closed loops or promote it through favorable connections. The increase in open flux is primarily driven by the equatorial dipole component, which is enhanced by differential rotation acting on tilted BMRs. These behaviors suggest that large open field structures develop from equatorial dipole components formed by these stretched BMRs. We attribute the rapid IMF increase in 2014 (CRs 2152–2157) to the combination of the following three factors: (1) a specific sunspot configuration that facilitated the expansion of the southern coronal hole, (2) the emergence of a giant sunspot group (active region 12192) with high magnetic intensity, and (3) the diffusion of these regions, which reinforced the global magnetic field. These results imply that rapid open flux variations during solar maximum are governed not only by the characteristics of emerging BMRs but also by their interaction with preexisting large coronal holes.
{"title":"Temporal Evolution of Sunspot Groups and Increase in the Open Flux during Solar Maximum in Cycle 24","authors":"Minami Yoshida, Toshifumi Shimizu, Shin Toriumi and Haruhisa Iijima","doi":"10.3847/1538-4357/ae4c4c","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4c4c","url":null,"abstract":"The evolution of the global solar magnetic field directly impacts the interplanetary magnetic field (IMF). During the solar maximum of Cycle 24, the monthly averaged IMF strength doubled over five Carrington rotations (CRs) in late 2014. To understand the physical origin of this increase, we investigate the temporal evolution of open magnetic flux resulting from the emergence and decay of bipolar magnetic regions (BMRs). Using surface flux transport and potential field source surface models, we simulated how BMR characteristics, spatial distributions, and interaction with background magnetic fields affect open flux evolution. Our simulation confirmed that the relative configuration of BMRs can either inhibit open flux expansion via closed loops or promote it through favorable connections. The increase in open flux is primarily driven by the equatorial dipole component, which is enhanced by differential rotation acting on tilted BMRs. These behaviors suggest that large open field structures develop from equatorial dipole components formed by these stretched BMRs. We attribute the rapid IMF increase in 2014 (CRs 2152–2157) to the combination of the following three factors: (1) a specific sunspot configuration that facilitated the expansion of the southern coronal hole, (2) the emergence of a giant sunspot group (active region 12192) with high magnetic intensity, and (3) the diffusion of these regions, which reinforced the global magnetic field. These results imply that rapid open flux variations during solar maximum are governed not only by the characteristics of emerging BMRs but also by their interaction with preexisting large coronal holes.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147587810","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 : 2026-04-01DOI: 10.3847/1538-4357/ae4d0d
Noel D. Richardson, Ryan M. T. White, Anthony J. Fabrega, Emma P. Lieb, André-Nicolas Chené, Peter G. Tuthill, John D. Monnier, Grant M. Hill, Peredur M. Williams, Anthony F. J. Moffat and Gerd Weigelt
When two massive stars orbit each other, their winds create a shock cone. In some cases, an evolved, carbon-rich Wolf–Rayet (WR) star’s wind collides with that of an orbiting OB star, condensing into dust downstream. This dust is then seen as large spiral structures that eventually move into the interstellar medium. Among these colliding-wind binaries, the archetypal system WR 104 has become an enigma. Aperture masking interferometry with Keck revealed an evolving, face-on dust spiral, with multiple rungs of dust visible from years of observations. In contrast to direct imaging, recent spectroscopic results imply that the orbit must have an inclination quite different from a face-on geometry. We examined photometry from the All-Sky Automated Survey (ASAS) and the All-Sky Automated Survey for SuperNovae (ASAS-SN) to place further constraints on the geometry of the orbit. By phase-binning the light curve, we find that the recent g-band light curve is brightest when the OB star lies in front of the WR star along our line of sight, with the lowest flux occurring at the opposite conjunction. We fit the light curve with an illustrative model for scattering eclipses, allowing us to infer a system inclination of . This inclination agrees with the recent spectroscopic orbit, and presents challenges to previous interpretations of high-angular-resolution images of the dust plume. We provide a qualitative geometric model for the dust plume that reconciles these results and show how WR 104 can provide a means for studying the properties of WR dust in detail.
{"title":"Can the Dust Eclipses in WR 104 Provide Constraints on the System’s Inclination?","authors":"Noel D. Richardson, Ryan M. T. White, Anthony J. Fabrega, Emma P. Lieb, André-Nicolas Chené, Peter G. Tuthill, John D. Monnier, Grant M. Hill, Peredur M. Williams, Anthony F. J. Moffat and Gerd Weigelt","doi":"10.3847/1538-4357/ae4d0d","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4d0d","url":null,"abstract":"When two massive stars orbit each other, their winds create a shock cone. In some cases, an evolved, carbon-rich Wolf–Rayet (WR) star’s wind collides with that of an orbiting OB star, condensing into dust downstream. This dust is then seen as large spiral structures that eventually move into the interstellar medium. Among these colliding-wind binaries, the archetypal system WR 104 has become an enigma. Aperture masking interferometry with Keck revealed an evolving, face-on dust spiral, with multiple rungs of dust visible from years of observations. In contrast to direct imaging, recent spectroscopic results imply that the orbit must have an inclination quite different from a face-on geometry. We examined photometry from the All-Sky Automated Survey (ASAS) and the All-Sky Automated Survey for SuperNovae (ASAS-SN) to place further constraints on the geometry of the orbit. By phase-binning the light curve, we find that the recent g-band light curve is brightest when the OB star lies in front of the WR star along our line of sight, with the lowest flux occurring at the opposite conjunction. We fit the light curve with an illustrative model for scattering eclipses, allowing us to infer a system inclination of . This inclination agrees with the recent spectroscopic orbit, and presents challenges to previous interpretations of high-angular-resolution images of the dust plume. We provide a qualitative geometric model for the dust plume that reconciles these results and show how WR 104 can provide a means for studying the properties of WR dust in detail.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147587902","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 : 2026-04-01DOI: 10.3847/1538-4357/ae4c57
T. A. Porter, I. V. Moskalenko, A. C. Cummings and G. Jóhannesson
We investigate the effects of the nearby interstellar medium (ISM) on the locally measured cosmic-ray (CR) spectra. Using the GalProp code, we explore how variations in the local gas and source distributions affect spectral features at low energies. Comparing with recent Voyager 1 measurements taken in the local ISM, we show that for a realistic interstellar gas distribution the data favor models in which there are no significant CR sources within ∼150–200 pc of the solar system, implying that the nearest dominant contributors to the low-energy CR flux are located at distances beyond this range. We find that the modeling supports the conclusion of A. C. Cummings et al. that there is a significant fraction of primary boron in its observed spectrum at low energies. Our study shows that detailed modeling of the immediate Galactic environment is required to robustly infer Galactic CR propagation parameters from local measurements and that accounting for nearby ISM structure can alleviate tensions between direct CR data and global propagation models.
{"title":"Voyager 1 Data Reveals Signatures of the Local Gas and Cosmic-Ray Source Distributions","authors":"T. A. Porter, I. V. Moskalenko, A. C. Cummings and G. Jóhannesson","doi":"10.3847/1538-4357/ae4c57","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4c57","url":null,"abstract":"We investigate the effects of the nearby interstellar medium (ISM) on the locally measured cosmic-ray (CR) spectra. Using the GalProp code, we explore how variations in the local gas and source distributions affect spectral features at low energies. Comparing with recent Voyager 1 measurements taken in the local ISM, we show that for a realistic interstellar gas distribution the data favor models in which there are no significant CR sources within ∼150–200 pc of the solar system, implying that the nearest dominant contributors to the low-energy CR flux are located at distances beyond this range. We find that the modeling supports the conclusion of A. C. Cummings et al. that there is a significant fraction of primary boron in its observed spectrum at low energies. Our study shows that detailed modeling of the immediate Galactic environment is required to robustly infer Galactic CR propagation parameters from local measurements and that accounting for nearby ISM structure can alleviate tensions between direct CR data and global propagation models.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147587900","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 : 2026-04-01DOI: 10.3847/1538-4357/ae517b
K. Douglass, S. BenZvi, N. Uberoi, C. Howlett, C. Saulder, K. Said, R. Demina, J. Aguilar, S. Ahlen, G. Aldering, D. Bianchi, D. Brooks, T. Claybaugh, A. Cuceu, T. M. Davis, K. S. Dawson, A. de la Macorra, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, G. Gutierrez, C. Hahn, K. Honscheid, M. Ishak, R. Joyce, T. Kisner, A. Kremin, M. Landriau, M. E. Levi, J. Lucey, P. Martini, A. Meisner, R. Miquel, J. Moustakas, N. Palanque-Delabrouille, W. J. Percival, F. Prada, G. Rossi, E. Sanchez, D. Schlegel, M. Schubnell, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver, R. Zhou and H. Zou
We calibrate the Tully–Fisher relation (TFR) with data from the DESI Peculiar Velocity (PV) Survey taken during the Survey Validation (SV) period of the DESI galaxy redshift survey. Placing spectroscopic fibers on the centers and major axes of spatially extended spiral galaxies identified in the 2020 Siena Galaxy Atlas using the DESI Legacy Surveys, we measure the rotational velocities at 0.33R26 for 1155 (1128 + 27 dwarf) spiral galaxies observed during SV. Using 39 spiral galaxies observed in the Coma cluster, we find a slope for the TFR of −8.32 ± 0.15 AB mag in the r band, with a scatter about the TFR of 1.12 ± 0.03 AB mag. We calibrate the zero-point of the TFR using galaxies with independent distances measured using type Ia supernovae (SNe Ia) via the cosmological distance ladder. From the SN Ia distances, we measure a zero-point of AB mag in the r band. We produce a public catalog of the distances to these 1128 spiral galaxies observed during DESI SV as part of the DESI PV Survey with our calibrated TFR. This is, to our knowledge, the first catalog of TFR distances produced with velocities measured at a single point in the disk.
{"title":"DESI EDR: Calibrating the Tully–Fisher Relationship with the DESI Peculiar Velocity Survey","authors":"K. Douglass, S. BenZvi, N. Uberoi, C. Howlett, C. Saulder, K. Said, R. Demina, J. Aguilar, S. Ahlen, G. Aldering, D. Bianchi, D. Brooks, T. Claybaugh, A. Cuceu, T. M. Davis, K. S. Dawson, A. de la Macorra, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, G. Gutierrez, C. Hahn, K. Honscheid, M. Ishak, R. Joyce, T. Kisner, A. Kremin, M. Landriau, M. E. Levi, J. Lucey, P. Martini, A. Meisner, R. Miquel, J. Moustakas, N. Palanque-Delabrouille, W. J. Percival, F. Prada, G. Rossi, E. Sanchez, D. Schlegel, M. Schubnell, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver, R. Zhou and H. Zou","doi":"10.3847/1538-4357/ae517b","DOIUrl":"https://doi.org/10.3847/1538-4357/ae517b","url":null,"abstract":"We calibrate the Tully–Fisher relation (TFR) with data from the DESI Peculiar Velocity (PV) Survey taken during the Survey Validation (SV) period of the DESI galaxy redshift survey. Placing spectroscopic fibers on the centers and major axes of spatially extended spiral galaxies identified in the 2020 Siena Galaxy Atlas using the DESI Legacy Surveys, we measure the rotational velocities at 0.33R26 for 1155 (1128 + 27 dwarf) spiral galaxies observed during SV. Using 39 spiral galaxies observed in the Coma cluster, we find a slope for the TFR of −8.32 ± 0.15 AB mag in the r band, with a scatter about the TFR of 1.12 ± 0.03 AB mag. We calibrate the zero-point of the TFR using galaxies with independent distances measured using type Ia supernovae (SNe Ia) via the cosmological distance ladder. From the SN Ia distances, we measure a zero-point of AB mag in the r band. We produce a public catalog of the distances to these 1128 spiral galaxies observed during DESI SV as part of the DESI PV Survey with our calibrated TFR. This is, to our knowledge, the first catalog of TFR distances produced with velocities measured at a single point in the disk.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147587819","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 : 2026-04-01DOI: 10.3847/1538-4357/ae4dde
Hanxiao Xia, Ziming Wang, Jianghua Wu, Yue Fang and Shiyu Du
BL Lacertae (BL Lac) has entered an active state since 2020, with multiwavelength observations revealing intense flares. In this study, we conducted 12 night multicolor optical monitoring using an 85 cm telescope from 2020 September to 2024 June and collected long-term broadband archived data from radio to γ-rays. Intraday variabilities were detected on four nights, and most of them exhibited a bluer-when-brighter behavior. Both clockwise and counterclockwise spectral hysteresis loops were found within a single night. However, no reliable intraband time lag was detected for the intranight variabilities. On long timescales, the cross-correlation analysis shows that the variations of the optical, X-ray, and γ-ray bands do not reveal an obvious time delay, while the variations in the radio bands lagged them by about 370 days. The measured time lags suggest two distinct emission regions, respectively, responsible for the optical to γ-ray radiation and for the radio radiation, with a spatial separation of approximately 4.50 × 1019 cm. We modeled the broadband spectral energy distributions during four flaring epochs and one quiescent epoch, and found evidence for the possible persistent existence of a very-high-energy emission region. We also confirmed a spectral evolution of the source from an intermediate-synchrotron-peaked BL Lac object to a low-synchrotron-peaked BL Lac object.
{"title":"Multiple Components and Spectral Evolution of BL Lacertae as Revealed by Multiwavelength Variability and SED Modeling","authors":"Hanxiao Xia, Ziming Wang, Jianghua Wu, Yue Fang and Shiyu Du","doi":"10.3847/1538-4357/ae4dde","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4dde","url":null,"abstract":"BL Lacertae (BL Lac) has entered an active state since 2020, with multiwavelength observations revealing intense flares. In this study, we conducted 12 night multicolor optical monitoring using an 85 cm telescope from 2020 September to 2024 June and collected long-term broadband archived data from radio to γ-rays. Intraday variabilities were detected on four nights, and most of them exhibited a bluer-when-brighter behavior. Both clockwise and counterclockwise spectral hysteresis loops were found within a single night. However, no reliable intraband time lag was detected for the intranight variabilities. On long timescales, the cross-correlation analysis shows that the variations of the optical, X-ray, and γ-ray bands do not reveal an obvious time delay, while the variations in the radio bands lagged them by about 370 days. The measured time lags suggest two distinct emission regions, respectively, responsible for the optical to γ-ray radiation and for the radio radiation, with a spatial separation of approximately 4.50 × 1019 cm. We modeled the broadband spectral energy distributions during four flaring epochs and one quiescent epoch, and found evidence for the possible persistent existence of a very-high-energy emission region. We also confirmed a spectral evolution of the source from an intermediate-synchrotron-peaked BL Lac object to a low-synchrotron-peaked BL Lac object.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"420 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147587901","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 : 2026-04-01DOI: 10.3847/1538-4357/ae4d39
Amanda M Lee, Jin Koda, Fumi Egusa, Akihiko Hirota, Shinya Komugi, Fumiya Maeda and Tsuyoshi Sawada
We present early results from a high-resolution analysis (∼100–200 pc) of the CO(2–1)/CO(1–0) line ratio in 12 nearby galaxies. We use new Atacama Large Millimeter/submillimeter Array (ALMA) CO(1–0) observations from the Fundamental CO(1–0) Transition Survey (FACTS), and re-imaged CO(2–1) data from PHANGS. We make empirical classifications based on the optical and molecular gas morphologies, which show clear systematic trends in the variation of R21 as a function of galactic structure. The sample includes barred, unbarred, and flocculent galaxies. The barred spiral galaxies follow a general trend when the gas exists significantly: R21 is high in the center, low along the bar, increases at the bar ends, and then lowers beyond the bar end or flattens in the outer parts of the disk. The structure dependence suggests the importance of galactic dynamics on molecular gas evolution, and consequently on star formation, in galaxies. R21 fluctuates in the spiral arms for both barred and unbarred galaxies. Areas around HII regions in some cases appear to show more high-ratio gas. Together, R21 varies systematically as a function of galactic structure, dynamics, and star formation activity.
{"title":"ALMA FACTS. III. High-resolution CO(2–1)/CO(1–0) Maps of Twelve Nearby Galaxies","authors":"Amanda M Lee, Jin Koda, Fumi Egusa, Akihiko Hirota, Shinya Komugi, Fumiya Maeda and Tsuyoshi Sawada","doi":"10.3847/1538-4357/ae4d39","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4d39","url":null,"abstract":"We present early results from a high-resolution analysis (∼100–200 pc) of the CO(2–1)/CO(1–0) line ratio in 12 nearby galaxies. We use new Atacama Large Millimeter/submillimeter Array (ALMA) CO(1–0) observations from the Fundamental CO(1–0) Transition Survey (FACTS), and re-imaged CO(2–1) data from PHANGS. We make empirical classifications based on the optical and molecular gas morphologies, which show clear systematic trends in the variation of R21 as a function of galactic structure. The sample includes barred, unbarred, and flocculent galaxies. The barred spiral galaxies follow a general trend when the gas exists significantly: R21 is high in the center, low along the bar, increases at the bar ends, and then lowers beyond the bar end or flattens in the outer parts of the disk. The structure dependence suggests the importance of galactic dynamics on molecular gas evolution, and consequently on star formation, in galaxies. R21 fluctuates in the spiral arms for both barred and unbarred galaxies. Areas around HII regions in some cases appear to show more high-ratio gas. Together, R21 varies systematically as a function of galactic structure, dynamics, and star formation activity.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147587811","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 : 2026-04-01DOI: 10.3847/1538-4357/ae4ecf
Michael J. Reiner
Direction-finding techniques from spacecraft have been used to locate and track interplanetary type III radio sources for many decades. These source locations are typically found to be farther from the Sun than expected on the bases of interplanetary density profiles derived from white-light and in situ observations. This puzzling result has led to suggestions that interplanetary scattering and other propagation effects may play an important role in shifting the observed locations of the radio sources away from the intrinsic or true radio emission regions. It is only recently that it has been possible to quantify the effects of anisotropic scattering on the locations of the individual type III radio sources in the solar corona and interplanetary medium. However, it is challenging to confirm these interplanetary scattering predictions with observations since the intrinsic radio emission regions in the interplanetary medium cannot easily be directly identified. We use the electron exciter beam kinematics, deduced from the remote and in situ radio observations, as a diagnostic of the intrinsic type III radio emission regions to compare with the observed type III source locations derived from two-spacecraft triangulations and to the expectations from isotropic and anisotropic scattering models. Our analyses suggest that the locations of the interplanetary type III radio emission regions are not significantly displaced, either radially or longitudinally, from the two-spacecraft triangulated source locations.
{"title":"Interplanetary Type III Radio Emission Locations Deduced from the Underlying Electron Exciter Beam Kinematics","authors":"Michael J. Reiner","doi":"10.3847/1538-4357/ae4ecf","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4ecf","url":null,"abstract":"Direction-finding techniques from spacecraft have been used to locate and track interplanetary type III radio sources for many decades. These source locations are typically found to be farther from the Sun than expected on the bases of interplanetary density profiles derived from white-light and in situ observations. This puzzling result has led to suggestions that interplanetary scattering and other propagation effects may play an important role in shifting the observed locations of the radio sources away from the intrinsic or true radio emission regions. It is only recently that it has been possible to quantify the effects of anisotropic scattering on the locations of the individual type III radio sources in the solar corona and interplanetary medium. However, it is challenging to confirm these interplanetary scattering predictions with observations since the intrinsic radio emission regions in the interplanetary medium cannot easily be directly identified. We use the electron exciter beam kinematics, deduced from the remote and in situ radio observations, as a diagnostic of the intrinsic type III radio emission regions to compare with the observed type III source locations derived from two-spacecraft triangulations and to the expectations from isotropic and anisotropic scattering models. Our analyses suggest that the locations of the interplanetary type III radio emission regions are not significantly displaced, either radially or longitudinally, from the two-spacecraft triangulated source locations.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"111 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147587815","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 : 2026-04-01DOI: 10.3847/1538-4357/ae4c5e
Stephen P. Schmidt, Daniel P. Thorngren and Kevin C. Schlaufman
The unexpectedly large radii of transiting hot Jupiters have led to many proposals for the physical mechanisms responsible for heating their interiors. While it has been shown that hot Jupiters reinflate as their host stars brighten due to heating deep in planetary interiors, young hot Jupiters also exhibit signs of delayed cooling possibly related to heating closer to their surfaces. To investigate this ambiguity, we enhance our previously published hot Jupiter thermal evolution model by adding a parameter that allows for both deep heating and delayed cooling. We fit our thermal evolution models to a homogeneous, physically self-consistent catalog of accurate and precise hot Jupiter system properties in a hierarchical Bayesian framework. We find that hot Jupiters’ interior cooling rates are reduced on average by 95%–98% compared to simpler anomalous heating models. The most plausible explanation for this inference is substantial shallow heating just below their radiative–convective boundaries that enables reinflation with much weaker deep heating. Shallow heating by Ohmic dissipation and/or temperature advection are therefore important components of accurate models of hot Jupiter atmospheres, especially in circulation models. If hot Jupiters are inflated primarily by shallow heating as we propose, then we predict that atmospheric circulation-related observables should increase with temperature in the range Teq ≲ 1500 K, peak in the range 1500 K ≲ Teq ≲ 1800 K, and decrease in the range Teq ≳ 1800 K.
{"title":"Hot Jupiters Are Inflated Primarily by Shallow Heating","authors":"Stephen P. Schmidt, Daniel P. Thorngren and Kevin C. Schlaufman","doi":"10.3847/1538-4357/ae4c5e","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4c5e","url":null,"abstract":"The unexpectedly large radii of transiting hot Jupiters have led to many proposals for the physical mechanisms responsible for heating their interiors. While it has been shown that hot Jupiters reinflate as their host stars brighten due to heating deep in planetary interiors, young hot Jupiters also exhibit signs of delayed cooling possibly related to heating closer to their surfaces. To investigate this ambiguity, we enhance our previously published hot Jupiter thermal evolution model by adding a parameter that allows for both deep heating and delayed cooling. We fit our thermal evolution models to a homogeneous, physically self-consistent catalog of accurate and precise hot Jupiter system properties in a hierarchical Bayesian framework. We find that hot Jupiters’ interior cooling rates are reduced on average by 95%–98% compared to simpler anomalous heating models. The most plausible explanation for this inference is substantial shallow heating just below their radiative–convective boundaries that enables reinflation with much weaker deep heating. Shallow heating by Ohmic dissipation and/or temperature advection are therefore important components of accurate models of hot Jupiter atmospheres, especially in circulation models. If hot Jupiters are inflated primarily by shallow heating as we propose, then we predict that atmospheric circulation-related observables should increase with temperature in the range Teq ≲ 1500 K, peak in the range 1500 K ≲ Teq ≲ 1800 K, and decrease in the range Teq ≳ 1800 K.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147587800","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 : 2026-04-01DOI: 10.3847/1538-4357/ae4c47
Marie-Luise Steinmeyer, Caroline Dorn, Aaron Werlen and Simon L. Grimm
The observed masses and radii of sub-Neptunes are typically explained by the gas dwarf or water world scenarios. While their evolutionary history on a population level has been proposed as a method to distinguish between these compositions, previous evolutionary models neglected the crucial role of atmosphere–interior chemical interaction. We present a novel evolution framework for sub-Neptunes that combines the thermal evolution with the chemical coupling of the atmosphere and interior. Using this model, we examine how planets formed inside and outside the water-ice line can be observationally distinguished, with an emphasis on their atmospheric properties. We find that young sub-Neptunes store the majority of their volatile budget in the interior, regardless of formation location. Nevertheless, the atmospheric metallicity is a factor of 4 higher for the planet formed outside the water-ice line. During cooling, hydrogen and oxygen exsolve from the interior, increasing the atmospheric mass fraction and counteracting the thermal contraction for both planets. Consequently, radius evolution alone cannot distinguish between the two formation scenarios. Instead, the primary discriminators are the abundance of carbon-bearing species and the resulting atmospheric C/O ratio. For sub-Neptunes formed beyond the water-ice line, nearly all carbon resides in the gas phase. We find that high molar fractions of CH4 (10−2) and H2O (>5 × 10−2) and a high C/O ratio (>5 × 10−1) are indicative of formation outside the water-ice line. In contrast, sub-Neptunes formed inside the water-ice line exhibit strongly suppressed CH4 abundances, yielding C/O ratios ranging from 10−7 to 10−1.
{"title":"Coupled Thermal–Chemical Evolution Models of Sub-Neptunes Reveal Atmospheric Signatures of Their Formation Location","authors":"Marie-Luise Steinmeyer, Caroline Dorn, Aaron Werlen and Simon L. Grimm","doi":"10.3847/1538-4357/ae4c47","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4c47","url":null,"abstract":"The observed masses and radii of sub-Neptunes are typically explained by the gas dwarf or water world scenarios. While their evolutionary history on a population level has been proposed as a method to distinguish between these compositions, previous evolutionary models neglected the crucial role of atmosphere–interior chemical interaction. We present a novel evolution framework for sub-Neptunes that combines the thermal evolution with the chemical coupling of the atmosphere and interior. Using this model, we examine how planets formed inside and outside the water-ice line can be observationally distinguished, with an emphasis on their atmospheric properties. We find that young sub-Neptunes store the majority of their volatile budget in the interior, regardless of formation location. Nevertheless, the atmospheric metallicity is a factor of 4 higher for the planet formed outside the water-ice line. During cooling, hydrogen and oxygen exsolve from the interior, increasing the atmospheric mass fraction and counteracting the thermal contraction for both planets. Consequently, radius evolution alone cannot distinguish between the two formation scenarios. Instead, the primary discriminators are the abundance of carbon-bearing species and the resulting atmospheric C/O ratio. For sub-Neptunes formed beyond the water-ice line, nearly all carbon resides in the gas phase. We find that high molar fractions of CH4 (10−2) and H2O (>5 × 10−2) and a high C/O ratio (>5 × 10−1) are indicative of formation outside the water-ice line. In contrast, sub-Neptunes formed inside the water-ice line exhibit strongly suppressed CH4 abundances, yielding C/O ratios ranging from 10−7 to 10−1.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"300 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147587898","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 : 2026-04-01DOI: 10.3847/1538-4357/ae523d
Xinzhong Er, Weishan Zhu, Shude Mao and Dongzi Li
Small-scale clumps of ionized gas have been suggested by observations in the interstellar medium and the circumgalactic medium. The propagation of radio signals can be deflected by these plasma clumps, i.e., plasma lensing. One observable consequence is the magnification and demagnification of background sources. These effects distort the observed luminosity function and potentially introduce bias into population studies. In this work, we investigate these effects on fast radio bursts using Gaussian plasma clumps distributed across multiple lens planes within a small field of view. The central electron density for each clump is sampled from uniform, lognormal, and Gaussian distributions. Two analytical models are employed to mimic the intrinsic luminosity function. Our results show that plasma lensing can modify the observed luminosity functions. On one hand, our model shows that radio sources may be demagnified below the detection threshold, and the strength varies between ∼1% and 15% depending on the ionized gas model and the source redshift. On the other hand, magnification can produce anomalously bright sources at the high luminosity end. Both effects introduce potential biases in inferred source properties. The lensing strength correlates with the power spectrum of free electron density. However, scattering effects in the host galaxy or in the Milky Way can suppress the plasma lensing effects.
{"title":"The Influence of Plasma Lensing Magnification on the Luminosity Function of Fast Radio Bursts","authors":"Xinzhong Er, Weishan Zhu, Shude Mao and Dongzi Li","doi":"10.3847/1538-4357/ae523d","DOIUrl":"https://doi.org/10.3847/1538-4357/ae523d","url":null,"abstract":"Small-scale clumps of ionized gas have been suggested by observations in the interstellar medium and the circumgalactic medium. The propagation of radio signals can be deflected by these plasma clumps, i.e., plasma lensing. One observable consequence is the magnification and demagnification of background sources. These effects distort the observed luminosity function and potentially introduce bias into population studies. In this work, we investigate these effects on fast radio bursts using Gaussian plasma clumps distributed across multiple lens planes within a small field of view. The central electron density for each clump is sampled from uniform, lognormal, and Gaussian distributions. Two analytical models are employed to mimic the intrinsic luminosity function. Our results show that plasma lensing can modify the observed luminosity functions. On one hand, our model shows that radio sources may be demagnified below the detection threshold, and the strength varies between ∼1% and 15% depending on the ionized gas model and the source redshift. On the other hand, magnification can produce anomalously bright sources at the high luminosity end. Both effects introduce potential biases in inferred source properties. The lensing strength correlates with the power spectrum of free electron density. However, scattering effects in the host galaxy or in the Milky Way can suppress the plasma lensing effects.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"64 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147587700","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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