Pub Date : 2025-02-05DOI: 10.3847/2041-8213/ada779
M. Arabsalmani, S. Roychowdhury, B. Schneider, V. Springel, E. Le Floc’h, F. Bournaud, A. Burkert, J.-C. Cuillandre, P.-A. Duc, E. Emsellem, D. Galárraga-Espinosa, E. Pian, F. Renaud and M. A. Zwaan
We identify a chain of galaxies along an almost straight line in the nearby Universe with a projected length of ~5 Mpc. The galaxies are distributed within projected distances of only 7–105 kpc from the axis of the identified filament. They have redshifts in a very small range of z = 0.0361−0.0370 so that their radial velocities are consistent with galaxy proper motions. The filament galaxies are mainly star forming and have stellar masses in a range of 109.1−1010.7M⊙. We search for systems with similar geometrical properties in the full-sky mock galaxy catalog of the MillenniumTNG simulations and find that, although such straight filaments are unusual and rare, they are predicted by ΛCDM simulations (4% incidence). We study the cold H i gas in a 1.3 Mpc section of the filament through H i 21 cm emission line observations and detect 11 H i sources, many more than expected from the H i mass function in a similar volume. They have H i masses 108.5−109.5M⊙ and are mostly within ~120 kpc projected distance from the filament axis. None of these H i sources has a confirmed optical counterpart. Their darkness together with their large H i 21 cm line widths indicates that they contain gas that might not yet be virialized. These clouds must be marking the peaks of the dark matter and H i distributions over large scales within the filament. The presence of such gas clouds around the filament spines is predicted by simulations, but this is the first time that the existence of such clouds in a filament is observationally confirmed.
{"title":"Pearls on a String: Dark and Bright Galaxies on a Strikingly Straight and Narrow Filament","authors":"M. Arabsalmani, S. Roychowdhury, B. Schneider, V. Springel, E. Le Floc’h, F. Bournaud, A. Burkert, J.-C. Cuillandre, P.-A. Duc, E. Emsellem, D. Galárraga-Espinosa, E. Pian, F. Renaud and M. A. Zwaan","doi":"10.3847/2041-8213/ada779","DOIUrl":"https://doi.org/10.3847/2041-8213/ada779","url":null,"abstract":"We identify a chain of galaxies along an almost straight line in the nearby Universe with a projected length of ~5 Mpc. The galaxies are distributed within projected distances of only 7–105 kpc from the axis of the identified filament. They have redshifts in a very small range of z = 0.0361−0.0370 so that their radial velocities are consistent with galaxy proper motions. The filament galaxies are mainly star forming and have stellar masses in a range of 109.1−1010.7M⊙. We search for systems with similar geometrical properties in the full-sky mock galaxy catalog of the MillenniumTNG simulations and find that, although such straight filaments are unusual and rare, they are predicted by ΛCDM simulations (4% incidence). We study the cold H i gas in a 1.3 Mpc section of the filament through H i 21 cm emission line observations and detect 11 H i sources, many more than expected from the H i mass function in a similar volume. They have H i masses 108.5−109.5M⊙ and are mostly within ~120 kpc projected distance from the filament axis. None of these H i sources has a confirmed optical counterpart. Their darkness together with their large H i 21 cm line widths indicates that they contain gas that might not yet be virialized. These clouds must be marking the peaks of the dark matter and H i distributions over large scales within the filament. The presence of such gas clouds around the filament spines is predicted by simulations, but this is the first time that the existence of such clouds in a filament is observationally confirmed.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143125153","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 : 2025-02-05DOI: 10.3847/2041-8213/adace0
M. J. Way
TRAPPIST-1 d is generally assumed to be at the boundary between a Venus-like world and an Earth-like world, although recently published works on TRAPPIST-1 b and c raise concerns that TRAPPIST-1 d may be similarly devoid of a substantial atmosphere. TRAPPIST-1 d is also relatively understudied in comparison with TRAPPIST-1 e. The latter has generally appeared to be within the habitable zone of most atmospheric modeling studies. Assuming that TRAPPIST-1 d still retains a substantial atmosphere, we demonstrate via a series of 3D general circulation model experiments using a dynamic ocean that the planet could reside within the habitable zone in a narrow parameter space. At the same time, it could also be an exo-Venus- or exo-Dead-type world or in transition between between one of these. Studies like this can help distinguish between these types of worlds.
{"title":"TRAPPIST-1 d: Exo-Venus, Exo-Earth, or Exo-Dead?","authors":"M. J. Way","doi":"10.3847/2041-8213/adace0","DOIUrl":"https://doi.org/10.3847/2041-8213/adace0","url":null,"abstract":"TRAPPIST-1 d is generally assumed to be at the boundary between a Venus-like world and an Earth-like world, although recently published works on TRAPPIST-1 b and c raise concerns that TRAPPIST-1 d may be similarly devoid of a substantial atmosphere. TRAPPIST-1 d is also relatively understudied in comparison with TRAPPIST-1 e. The latter has generally appeared to be within the habitable zone of most atmospheric modeling studies. Assuming that TRAPPIST-1 d still retains a substantial atmosphere, we demonstrate via a series of 3D general circulation model experiments using a dynamic ocean that the planet could reside within the habitable zone in a narrow parameter space. At the same time, it could also be an exo-Venus- or exo-Dead-type world or in transition between between one of these. Studies like this can help distinguish between these types of worlds.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"62 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143192589","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 : 2025-02-05DOI: 10.3847/2041-8213/adad5d
Yi-Han Zhao, Ning-Chen Sun, Junjie Wu, Zexi Niu, Xinyi Hong, Yinhan Huang, Justyn R. Maund, Qiang Xi, Danfeng Xiang and Jifeng Liu
To date, SN 2017ein is the only Type Ic supernova with a directly identified progenitor candidate. This candidate points to a very massive (>45 M⊙) Wolf–Rayet (WR) progenitor, but its disappearance after the explosion of SN 2017ein remains unconfirmed. In this work, we revisit SN 2017ein in late-time images acquired by the Hubble Space Telescope at 2.4–3.8 yr after peak brightness. We find this source has not disappeared, and its brightness and color remain almost the same as in the preexplosion images. Thus, we conclude that the preexplosion source is not the genuine progenitor of SN 2017ein. It is not much likelier to be a companion star of the progenitor since it has a much lower extinction than SN 2017ein; its color also seems inconsistent with a star cluster, indicated by the newly added magnitude limit in F336W, apart from F555W and F814W. We suggest, therefore, this source is an unrelated star in chance alignment with SN 2017ein. Based on the low ejecta mass, we propose that SN 2017ein is most likely originated from a moderately massive star with Mini ∼ 8–20 M⊙, stripped by binary interaction, rather than a very massive WR progenitor.
{"title":"Exclusion of a Direct Progenitor Detection for the Type Ic SN 2017ein Based on Late-time Observations","authors":"Yi-Han Zhao, Ning-Chen Sun, Junjie Wu, Zexi Niu, Xinyi Hong, Yinhan Huang, Justyn R. Maund, Qiang Xi, Danfeng Xiang and Jifeng Liu","doi":"10.3847/2041-8213/adad5d","DOIUrl":"https://doi.org/10.3847/2041-8213/adad5d","url":null,"abstract":"To date, SN 2017ein is the only Type Ic supernova with a directly identified progenitor candidate. This candidate points to a very massive (>45 M⊙) Wolf–Rayet (WR) progenitor, but its disappearance after the explosion of SN 2017ein remains unconfirmed. In this work, we revisit SN 2017ein in late-time images acquired by the Hubble Space Telescope at 2.4–3.8 yr after peak brightness. We find this source has not disappeared, and its brightness and color remain almost the same as in the preexplosion images. Thus, we conclude that the preexplosion source is not the genuine progenitor of SN 2017ein. It is not much likelier to be a companion star of the progenitor since it has a much lower extinction than SN 2017ein; its color also seems inconsistent with a star cluster, indicated by the newly added magnitude limit in F336W, apart from F555W and F814W. We suggest, therefore, this source is an unrelated star in chance alignment with SN 2017ein. Based on the low ejecta mass, we propose that SN 2017ein is most likely originated from a moderately massive star with Mini ∼ 8–20 M⊙, stripped by binary interaction, rather than a very massive WR progenitor.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143192586","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 : 2025-02-04DOI: 10.3847/2041-8213/adad74
Mia Mancuso, Ju Jing, Haimin Wang and Wenda Cao
The dynamic structures of solar filaments prior to solar flares provide important physical clues about the onset of solar eruptions. Observations of those structures under subarcsecond resolution with high cadence are rare. We present high-resolution observations covering preeruptive and eruptive phases of two C-class solar flares, C5.1 (SOL2022-11-14T17:29) and C5.1 (SOL2022-11-14T19:29), obtained by the Goode Solar Telescope at Big Bear Solar Observatory. Both flares are ejective, i.e., accompanied by coronal mass ejections (CMEs). High-resolution Hα observations reveal details of the flares and some striking features, such as a filament peeling process: individual strands of thin flux tubes are separated from the main filament, followed shortly thereafter by a flare. The estimated flux of rising strands is in the order of 1017 Mx, versus the 1019 Mx of the entire filament. Our new finding may explain why photospheric magnetic fields and overall active region and filament structures as a whole do not have obvious changes after a flare, and why some CMEs have been traced back to the solar active regions with only nonerupting filaments, as the magnetic reconnection may only involve a very small amount of flux in the active region, requiring no significant filament eruptions. We suggest internal reconnection between filament threads, instead of reconnection to external loops, as the process responsible for triggering this peeling of threads that results in the two flares and their subsequent CMEs.
{"title":"Solar Flares Triggered by a Filament Peeling Process Revealed by High-resolution GST Hα Observations","authors":"Mia Mancuso, Ju Jing, Haimin Wang and Wenda Cao","doi":"10.3847/2041-8213/adad74","DOIUrl":"https://doi.org/10.3847/2041-8213/adad74","url":null,"abstract":"The dynamic structures of solar filaments prior to solar flares provide important physical clues about the onset of solar eruptions. Observations of those structures under subarcsecond resolution with high cadence are rare. We present high-resolution observations covering preeruptive and eruptive phases of two C-class solar flares, C5.1 (SOL2022-11-14T17:29) and C5.1 (SOL2022-11-14T19:29), obtained by the Goode Solar Telescope at Big Bear Solar Observatory. Both flares are ejective, i.e., accompanied by coronal mass ejections (CMEs). High-resolution Hα observations reveal details of the flares and some striking features, such as a filament peeling process: individual strands of thin flux tubes are separated from the main filament, followed shortly thereafter by a flare. The estimated flux of rising strands is in the order of 1017 Mx, versus the 1019 Mx of the entire filament. Our new finding may explain why photospheric magnetic fields and overall active region and filament structures as a whole do not have obvious changes after a flare, and why some CMEs have been traced back to the solar active regions with only nonerupting filaments, as the magnetic reconnection may only involve a very small amount of flux in the active region, requiring no significant filament eruptions. We suggest internal reconnection between filament threads, instead of reconnection to external loops, as the process responsible for triggering this peeling of threads that results in the two flares and their subsequent CMEs.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083529","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 : 2025-02-04DOI: 10.3847/2041-8213/ad9f5c
Imad Pasha, Pieter G. van Dokkum, Qing Liu, 青 刘, William P. Bowman, Steven R. Janssens, Michael A. Keim, Chloe Neufeld and Roberto Abraham
We report the discovery and multiwavelength follow-up of LEDA 1313424 (“Bullseye”), a collisional ring galaxy (CRG) with nine readily identified rings—the most so far reported for a CRG. These data shed new light on the rapid, multiring phase of CRG evolution. Using Hubble Space Telescope (HST) imaging, we identify and measure nine ring structures, several of which are “piled up” near the center of the galaxy, while others extend to tens of kiloparsecs scales. We also identify faint patches of emission at large radii (~70 kpc) in the HST imaging and confirm the association of this emission with the galaxy via spectroscopy. Deep ground-based imaging using the Dragonfly Telephoto Array finds evidence that this patch of emission is part of an older, fading ring from the collision. We find that the locations of the detected rings are an excellent match to predictions from analytic theory if the galaxy was a 10-ring system whose outermost ring has faded away. We identify the likely impacting galaxy via Keck/KCWI spectroscopy, finding evidence for gas extending between it and the Bullseye. The overall size of this galaxy rivals that of known giant low surface brightness galaxies (GLSBs) such as Malin I, lending credence to the hypothesis that CRGs can evolve into GLSBs as their rings expand and fade. Analysis of the H i content in this galaxy from ALFALFA finds significantly elevated neutral hydrogen with respect to the galaxy's stellar mass, another feature in alignment with GLSB systems.
{"title":"The Bullseye: HST, Keck/KCWI, and Dragonfly Characterization of a Giant Nine-ringed Galaxy","authors":"Imad Pasha, Pieter G. van Dokkum, Qing Liu, 青 刘, William P. Bowman, Steven R. Janssens, Michael A. Keim, Chloe Neufeld and Roberto Abraham","doi":"10.3847/2041-8213/ad9f5c","DOIUrl":"https://doi.org/10.3847/2041-8213/ad9f5c","url":null,"abstract":"We report the discovery and multiwavelength follow-up of LEDA 1313424 (“Bullseye”), a collisional ring galaxy (CRG) with nine readily identified rings—the most so far reported for a CRG. These data shed new light on the rapid, multiring phase of CRG evolution. Using Hubble Space Telescope (HST) imaging, we identify and measure nine ring structures, several of which are “piled up” near the center of the galaxy, while others extend to tens of kiloparsecs scales. We also identify faint patches of emission at large radii (~70 kpc) in the HST imaging and confirm the association of this emission with the galaxy via spectroscopy. Deep ground-based imaging using the Dragonfly Telephoto Array finds evidence that this patch of emission is part of an older, fading ring from the collision. We find that the locations of the detected rings are an excellent match to predictions from analytic theory if the galaxy was a 10-ring system whose outermost ring has faded away. We identify the likely impacting galaxy via Keck/KCWI spectroscopy, finding evidence for gas extending between it and the Bullseye. The overall size of this galaxy rivals that of known giant low surface brightness galaxies (GLSBs) such as Malin I, lending credence to the hypothesis that CRGs can evolve into GLSBs as their rings expand and fade. Analysis of the H i content in this galaxy from ALFALFA finds significantly elevated neutral hydrogen with respect to the galaxy's stellar mass, another feature in alignment with GLSB systems.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083528","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 : 2025-02-03DOI: 10.3847/2041-8213/adace9
T. Wevers, M. Guolo, S. Lockwood, A. Mummery, D. R. Pasham and R. Arcodia
X-ray quasiperiodic eruptions (QPEs) are a novel mode of variability in nearby galactic nuclei whose origin remains unknown. Their multiwavelength properties are poorly constrained, as studies have focused almost entirely on the X-ray band. Here, we report on time-resolved, coordinated Hubble Space Telescope far-ultraviolet (FUV) and XMM-Newton X-ray observations of the shortest period X-ray QPE source currently known, eRO-QPE2. We detect a bright UV point source (LFUV ≈ few × 1041 erg s−1) that does not show statistically significant variability between the X-ray eruption and quiescent phases. This emission is unlikely to be powered by a young stellar population in a nuclear stellar cluster. The X-ray-to-UV spectral energy distribution can be described by a compact accretion disk ( ). Such compact disks are incompatible with typical disks in active galactic nuclei, but form naturally following the tidal disruption of a star. Our results rule out models (for eRO-QPE2) invoking (i) a classic active galactic nucleus accretion disk and (ii) no accretion disk at all. For orbiter models, the expected radius derived from the timing properties would naturally lead to disk-orbiter interactions for both quasi-spherical and eccentric trajectories. We infer a black hole mass of log10(MBH) = 5.9 ± 0.3 M⊙ and an Eddington ratio of 0.13 ; in combination with the compact outer radius, this is inconsistent with existing disk instability models. After accounting for the quiescent disk emission, we constrain the ratio of X-ray to FUV luminosity of the eruption component to be LX/LFUV > 16−85 (depending on the intrinsic extinction).
{"title":"Time-resolved Hubble Space Telescope UV Observations of an X-Ray Quasiperiodic Eruption Source","authors":"T. Wevers, M. Guolo, S. Lockwood, A. Mummery, D. R. Pasham and R. Arcodia","doi":"10.3847/2041-8213/adace9","DOIUrl":"https://doi.org/10.3847/2041-8213/adace9","url":null,"abstract":"X-ray quasiperiodic eruptions (QPEs) are a novel mode of variability in nearby galactic nuclei whose origin remains unknown. Their multiwavelength properties are poorly constrained, as studies have focused almost entirely on the X-ray band. Here, we report on time-resolved, coordinated Hubble Space Telescope far-ultraviolet (FUV) and XMM-Newton X-ray observations of the shortest period X-ray QPE source currently known, eRO-QPE2. We detect a bright UV point source (LFUV ≈ few × 1041 erg s−1) that does not show statistically significant variability between the X-ray eruption and quiescent phases. This emission is unlikely to be powered by a young stellar population in a nuclear stellar cluster. The X-ray-to-UV spectral energy distribution can be described by a compact accretion disk ( ). Such compact disks are incompatible with typical disks in active galactic nuclei, but form naturally following the tidal disruption of a star. Our results rule out models (for eRO-QPE2) invoking (i) a classic active galactic nucleus accretion disk and (ii) no accretion disk at all. For orbiter models, the expected radius derived from the timing properties would naturally lead to disk-orbiter interactions for both quasi-spherical and eccentric trajectories. We infer a black hole mass of log10(MBH) = 5.9 ± 0.3 M⊙ and an Eddington ratio of 0.13 ; in combination with the compact outer radius, this is inconsistent with existing disk instability models. After accounting for the quiescent disk emission, we constrain the ratio of X-ray to FUV luminosity of the eruption component to be LX/LFUV > 16−85 (depending on the intrinsic extinction).","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083530","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 : 2025-01-31DOI: 10.3847/2041-8213/ada7f8
Alessandro Di Marco, Fabio La Monaca, Anna Bobrikova, Luigi Stella, Alessandro Papitto, Juri Poutanen, Maria Cristina Baglio, Matteo Bachetti, Vladislav Loktev, Maura Pilia and Daniele Rogantini
We present the result from the 2024 April observation of the low-mass X-ray binary GX 13+1 with the Imaging X-ray Polarimetry Explorer (IXPE), together with Neutron Star Interior Composition Explorer and Swift- X-Ray Telescope coordinated observations. Two light-curve dips were observed; during them, the harder Comptonized spectral component was dominant and the polarization degree (PD) higher than in the softer, off-dip intervals. Through a joint analysis of the three IXPE observations, which also included the dip from the first observation, we demonstrate that the polarization properties varied in response to the intensity and spectral hardness changes associated with the dips. The PD attained values up to ∼4%. The polarization angle (PA) showed a swing of ∼70∘ across the dip and off-dip states, comparable to the continuous rotation seen during the first IXPE observation. We discuss these results in the context of models for polarized emission from the accretion disk and the boundary/spreading layer on the neutron star surface. We also draw attention to the role that an extended accretion disk corona or disk wind can play in generating high PDs and, possibly, swings of the PA.
{"title":"X-Ray Dips and Polarization Angle Swings in GX 13+1","authors":"Alessandro Di Marco, Fabio La Monaca, Anna Bobrikova, Luigi Stella, Alessandro Papitto, Juri Poutanen, Maria Cristina Baglio, Matteo Bachetti, Vladislav Loktev, Maura Pilia and Daniele Rogantini","doi":"10.3847/2041-8213/ada7f8","DOIUrl":"https://doi.org/10.3847/2041-8213/ada7f8","url":null,"abstract":"We present the result from the 2024 April observation of the low-mass X-ray binary GX 13+1 with the Imaging X-ray Polarimetry Explorer (IXPE), together with Neutron Star Interior Composition Explorer and Swift- X-Ray Telescope coordinated observations. Two light-curve dips were observed; during them, the harder Comptonized spectral component was dominant and the polarization degree (PD) higher than in the softer, off-dip intervals. Through a joint analysis of the three IXPE observations, which also included the dip from the first observation, we demonstrate that the polarization properties varied in response to the intensity and spectral hardness changes associated with the dips. The PD attained values up to ∼4%. The polarization angle (PA) showed a swing of ∼70∘ across the dip and off-dip states, comparable to the continuous rotation seen during the first IXPE observation. We discuss these results in the context of models for polarized emission from the accretion disk and the boundary/spreading layer on the neutron star surface. We also draw attention to the role that an extended accretion disk corona or disk wind can play in generating high PDs and, possibly, swings of the PA.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143077592","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 : 2025-01-31DOI: 10.3847/2041-8213/adaaf5
Z. H. Zhao, W. Q. Yuan, L. X. Li, X. W. Zhu, X. X. Jin, S. P. Zhu, X. T. He and B. Qiao
The origin of coherent, near-equipartitioned magnetic fields in the universe remains poorly understood, especially in collisionless scenarios. By means of theoretical modeling that includes indispensable kinetic effects and fully kinetic particle-in-cell simulation that contains sufficient scale separation, we self-consistently show that the collisionless large-scale dynamo is quite efficient and the system-scale coherent fields can be generated from kinetic-scale seeds under a turbulent helical drive. We find that, by triggering kinetic mirror and firehose instabilities, the pressure anisotropy—a kinetic effect that is unresolved in conventional magnetohydrodynamics—is the key physics that produces net magnetic helicity that can be inversely transferred to large scales. The magnetic helicity generation rate can be formulated as , where urms is the turbulent velocity and Lin is the driving scale. Our results profoundly refine the picture of cosmic dynamos and potentially resolve the critical issue of dynamo quench.
{"title":"Pressure-anisotropy-mediated Helical Dynamo in Turbulent Collisionless Plasmas","authors":"Z. H. Zhao, W. Q. Yuan, L. X. Li, X. W. Zhu, X. X. Jin, S. P. Zhu, X. T. He and B. Qiao","doi":"10.3847/2041-8213/adaaf5","DOIUrl":"https://doi.org/10.3847/2041-8213/adaaf5","url":null,"abstract":"The origin of coherent, near-equipartitioned magnetic fields in the universe remains poorly understood, especially in collisionless scenarios. By means of theoretical modeling that includes indispensable kinetic effects and fully kinetic particle-in-cell simulation that contains sufficient scale separation, we self-consistently show that the collisionless large-scale dynamo is quite efficient and the system-scale coherent fields can be generated from kinetic-scale seeds under a turbulent helical drive. We find that, by triggering kinetic mirror and firehose instabilities, the pressure anisotropy—a kinetic effect that is unresolved in conventional magnetohydrodynamics—is the key physics that produces net magnetic helicity that can be inversely transferred to large scales. The magnetic helicity generation rate can be formulated as , where urms is the turbulent velocity and Lin is the driving scale. Our results profoundly refine the picture of cosmic dynamos and potentially resolve the critical issue of dynamo quench.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143077593","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 : 2025-01-31DOI: 10.3847/2041-8213/adac4f
Johannes Tschernitz and Philippe-A. Bourdin
Surface convection is important for the presence of magnetic activity at stars. So far, this convection is thought to be a result of heating from below, where convection cells rise and break up. New models reveal that surface convection is instead strongly driven by cooling from above. We compare two simulations of surface convection, one with a significant heating from below and one without. We obtain surface convection in both cases, and they show similar granulation patterns. The deep convection driven by heating from below is still evolving and asymptotically approaches a steady-state solution. We find that convection from below is not needed at all to form typical photospheric granulation. This indicates the possibility of a surface dynamo acting on stars without a convecting envelope. Even stars without a convecting envelope could therefore exhibit stronger magnetic and coronal activity than expected so far.
{"title":"Granulation and Convectional Driving on Stellar Surfaces","authors":"Johannes Tschernitz and Philippe-A. Bourdin","doi":"10.3847/2041-8213/adac4f","DOIUrl":"https://doi.org/10.3847/2041-8213/adac4f","url":null,"abstract":"Surface convection is important for the presence of magnetic activity at stars. So far, this convection is thought to be a result of heating from below, where convection cells rise and break up. New models reveal that surface convection is instead strongly driven by cooling from above. We compare two simulations of surface convection, one with a significant heating from below and one without. We obtain surface convection in both cases, and they show similar granulation patterns. The deep convection driven by heating from below is still evolving and asymptotically approaches a steady-state solution. We find that convection from below is not needed at all to form typical photospheric granulation. This indicates the possibility of a surface dynamo acting on stars without a convecting envelope. Even stars without a convecting envelope could therefore exhibit stronger magnetic and coronal activity than expected so far.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083531","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 : 2025-01-30DOI: 10.3847/2041-8213/adab75
Thomas Corbett, Alex Doner, Mihály Horányi, Pontus Brandt, Will Grundy, Carey M. Lisse, Joel Parker, Lowell Peltier, Andrew R. Poppe, Kelsi N. Singer, S. Alan Stern and Anne J. Verbiscer
The Venetia Burney Student Dust Counter (SDC) on board the New Horizons spacecraft measures the spatial and size distributions of dust along its trajectory. Models based on early SDC measurements predicted a peak dust number density at a heliocentric distance of ∼40 au, followed by a rapid decline. Instead, SDC observed dust fluxes 2–3 times higher than predicted between 40 and 60 au. One potential explanation for this discrepancy is that SDC may be encountering icy grains with different dynamical behavior than previously modeled silicate grains. Due to ultraviolet photosputtering, water–ice grains rapidly erode and migrate outward, significantly contributing to the measured dust number densities only at distances ≳40 au. We present a model of silicate and ice grain dynamics in the outer solar system, considering gravitational and radiation forces and grain erosion. Using SDC data, we estimate that the mass production rate of ice grains between 0.1 and 10 μm in the Kuiper Belt (KB) would need to be 20–70 times higher than that of silicate grains. However, KB grains are expected to be refractory/volatile mixtures rather than pure silicate or ice. Thus, we briefly explore simple models of more realistic mixed-grain cases to further gauge the effects of grain composition on the equilibrium dust distribution. Future SDC measurements at greater distances will test the model predictions and further constrain silicate and ice grain production rates in the KB.
{"title":"Production, Transport, and Destruction of Dust in the Kuiper Belt: The Effects of Refractory and Volatile Grain Compositions","authors":"Thomas Corbett, Alex Doner, Mihály Horányi, Pontus Brandt, Will Grundy, Carey M. Lisse, Joel Parker, Lowell Peltier, Andrew R. Poppe, Kelsi N. Singer, S. Alan Stern and Anne J. Verbiscer","doi":"10.3847/2041-8213/adab75","DOIUrl":"https://doi.org/10.3847/2041-8213/adab75","url":null,"abstract":"The Venetia Burney Student Dust Counter (SDC) on board the New Horizons spacecraft measures the spatial and size distributions of dust along its trajectory. Models based on early SDC measurements predicted a peak dust number density at a heliocentric distance of ∼40 au, followed by a rapid decline. Instead, SDC observed dust fluxes 2–3 times higher than predicted between 40 and 60 au. One potential explanation for this discrepancy is that SDC may be encountering icy grains with different dynamical behavior than previously modeled silicate grains. Due to ultraviolet photosputtering, water–ice grains rapidly erode and migrate outward, significantly contributing to the measured dust number densities only at distances ≳40 au. We present a model of silicate and ice grain dynamics in the outer solar system, considering gravitational and radiation forces and grain erosion. Using SDC data, we estimate that the mass production rate of ice grains between 0.1 and 10 μm in the Kuiper Belt (KB) would need to be 20–70 times higher than that of silicate grains. However, KB grains are expected to be refractory/volatile mixtures rather than pure silicate or ice. Thus, we briefly explore simple models of more realistic mixed-grain cases to further gauge the effects of grain composition on the equilibrium dust distribution. Future SDC measurements at greater distances will test the model predictions and further constrain silicate and ice grain production rates in the KB.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143077596","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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