Pub Date : 2026-02-25DOI: 10.3847/1538-4357/ae3d97
Jiachao Liu, Nan Ding, Qiusheng Gu, Keli Peng, Yunyong Tang, Yongyun Chen and Dingrong Xiong
Although Gaussian processes have been widely applied in modeling the high-energy light curves of blazars, a systematic comparison of the performances of different kernel functions within Gaussian processes has remained lacking. Based on a Bayesian inference framework, we systematically compare the performances of three Gaussian process kernel functions in modeling blazars’ long-term gamma-ray light curves. The results indicate that, among the tested kernel functions, the Matérn 1/2 kernel performs best for both types of blazars—BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs)—suggesting that a universal stochastic process likely governs the high-energy variability of the blazar population. Statistically, this kernel is equivalent to the “shot-noise” model, supporting the scenario that the gamma-ray variability in blazars originates from the random superposition of numerous independent flares. A statistical analysis of hyperparameters reveals that the variability amplitude of FSRQs is significantly higher than that of BL Lacs, which may be related to their radiation being more strongly modulated by external photon fields. The intrinsic correlation timescales of both sources are similar and show no dependence on black hole mass or intrinsic luminosity. This indicates that the timescale is primarily determined by local physical conditions within the jet, rather than by the global properties of the central engine.
{"title":"Universal Stochastic Process in Blazar Gamma-Ray Variability Revealed by Bayesian Kernel Comparison","authors":"Jiachao Liu, Nan Ding, Qiusheng Gu, Keli Peng, Yunyong Tang, Yongyun Chen and Dingrong Xiong","doi":"10.3847/1538-4357/ae3d97","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3d97","url":null,"abstract":"Although Gaussian processes have been widely applied in modeling the high-energy light curves of blazars, a systematic comparison of the performances of different kernel functions within Gaussian processes has remained lacking. Based on a Bayesian inference framework, we systematically compare the performances of three Gaussian process kernel functions in modeling blazars’ long-term gamma-ray light curves. The results indicate that, among the tested kernel functions, the Matérn 1/2 kernel performs best for both types of blazars—BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs)—suggesting that a universal stochastic process likely governs the high-energy variability of the blazar population. Statistically, this kernel is equivalent to the “shot-noise” model, supporting the scenario that the gamma-ray variability in blazars originates from the random superposition of numerous independent flares. A statistical analysis of hyperparameters reveals that the variability amplitude of FSRQs is significantly higher than that of BL Lacs, which may be related to their radiation being more strongly modulated by external photon fields. The intrinsic correlation timescales of both sources are similar and show no dependence on black hole mass or intrinsic luminosity. This indicates that the timescale is primarily determined by local physical conditions within the jet, rather than by the global properties of the central engine.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"99 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147280034","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 : 2026-02-25DOI: 10.3847/1538-4357/ae3fa2
J. Christopher Mihos, Patrick R. Durrell, Brian Malkan and Aaron E. Watkins
We use deep Hubble Space Telescope imaging to study stellar populations in the outer halo of the spiral galaxy M96, located in the dynamically active Leo I galaxy group. Our imaging targets two fields at a projected distance of 50 kpc from the galaxy’s center, with a 50% photometric completeness limit of F814W = 28.0—nearly 2 magnitudes below the tip of the red giant branch (RGB). In both fields, we clearly detect red giant stars in M96’s halo, with a space density that corresponds to an equivalent broadband surface brightness of μV ≈ 31.7 mag arcsec−2. We find little evidence for any differences in the spatial density or color of the RGB stars in the two fields. Using isochrone matching, we derive a median metallicity for the red giants of [M/H] = −1.36, with an interquartile spread of ± 0.75 dex. Adopting a power-law radial density profile, we also derive a total halo mass of M⊙, implying a stellar halo mass fraction of %—on the high end for spiral galaxies, but with significant uncertainty. Finally, we find that M96 appears offset from the stellar halo mass–metallicity relationship for spirals, with a halo that is distinctly metal-poor for its halo mass. While a variety of systematic effects could have conspired to drive M96 off this relationship, if confirmed our results may argue for a markedly different accretion history for M96 compared to other spirals in the nearby Universe.
{"title":"Stellar Populations in the Extreme Outer Halo of the Spiral Galaxy M96","authors":"J. Christopher Mihos, Patrick R. Durrell, Brian Malkan and Aaron E. Watkins","doi":"10.3847/1538-4357/ae3fa2","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3fa2","url":null,"abstract":"We use deep Hubble Space Telescope imaging to study stellar populations in the outer halo of the spiral galaxy M96, located in the dynamically active Leo I galaxy group. Our imaging targets two fields at a projected distance of 50 kpc from the galaxy’s center, with a 50% photometric completeness limit of F814W = 28.0—nearly 2 magnitudes below the tip of the red giant branch (RGB). In both fields, we clearly detect red giant stars in M96’s halo, with a space density that corresponds to an equivalent broadband surface brightness of μV ≈ 31.7 mag arcsec−2. We find little evidence for any differences in the spatial density or color of the RGB stars in the two fields. Using isochrone matching, we derive a median metallicity for the red giants of [M/H] = −1.36, with an interquartile spread of ± 0.75 dex. Adopting a power-law radial density profile, we also derive a total halo mass of M⊙, implying a stellar halo mass fraction of %—on the high end for spiral galaxies, but with significant uncertainty. Finally, we find that M96 appears offset from the stellar halo mass–metallicity relationship for spirals, with a halo that is distinctly metal-poor for its halo mass. While a variety of systematic effects could have conspired to drive M96 off this relationship, if confirmed our results may argue for a markedly different accretion history for M96 compared to other spirals in the nearby Universe.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147278955","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 : 2026-02-25DOI: 10.3847/1538-4357/ae3c76
Barry F. Madore and Wendy L. Freedman
We examine the multiwavelength period–luminosity–color (PLC) relations for Cepheid variables in the Large and Small Magellanic Clouds and the Milky Way. From first-principles stellar physics, the luminosity of a Cepheid is determined by its radius and surface temperature, yielding a fundamental PLC relation whose observational proxies are the pulsation period and intrinsic color. Using Cepheids in the Magellanic Clouds, we show that the PLC relation recovers the known geometries and line-of-sight tilts of their disks, confirming its ability to detect true distance modulus variations that are achromatic and consistent across all filters. Surprisingly, for Milky Way Cepheids with individually determined reddenings and Hubble Space Telescope and Gaia parallaxes, the residuals from multiwavelength PL fits are also found to be achromatic and identical in sign and amplitude across all passbands, in this case indicating that parallax errors are the dominant source of the scatter. Applying bandpass-averaged corrections to individual Cepheids recovers the theoretically expected wavelength-dependent narrowing of the instability strip and results in revised parallaxes with a median improvement in precision of roughly a factor of 2. In addition, they show no statistically significant correlation with metallicity over the range –0.2 < [Fe/H] 0 < +0.5 dex. The final extinction-and-reddening-corrected PLC relation yields an rms scatter of ±0.04 mag, corresponding to ∼2% precision in distance per star. The use of a physically grounded PLC will provide a more robust foundation for the Cepheid-based extragalactic distance scale and the determination of the Hubble constant.
{"title":"Revising the Milky Way Cepheid Calibration: Quantifying and Correcting for Previously Undetected Distance Modulus Errors in the Gaia-based Multiwavelength Period–Luminosity Relations","authors":"Barry F. Madore and Wendy L. Freedman","doi":"10.3847/1538-4357/ae3c76","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3c76","url":null,"abstract":"We examine the multiwavelength period–luminosity–color (PLC) relations for Cepheid variables in the Large and Small Magellanic Clouds and the Milky Way. From first-principles stellar physics, the luminosity of a Cepheid is determined by its radius and surface temperature, yielding a fundamental PLC relation whose observational proxies are the pulsation period and intrinsic color. Using Cepheids in the Magellanic Clouds, we show that the PLC relation recovers the known geometries and line-of-sight tilts of their disks, confirming its ability to detect true distance modulus variations that are achromatic and consistent across all filters. Surprisingly, for Milky Way Cepheids with individually determined reddenings and Hubble Space Telescope and Gaia parallaxes, the residuals from multiwavelength PL fits are also found to be achromatic and identical in sign and amplitude across all passbands, in this case indicating that parallax errors are the dominant source of the scatter. Applying bandpass-averaged corrections to individual Cepheids recovers the theoretically expected wavelength-dependent narrowing of the instability strip and results in revised parallaxes with a median improvement in precision of roughly a factor of 2. In addition, they show no statistically significant correlation with metallicity over the range –0.2 < [Fe/H] 0 < +0.5 dex. The final extinction-and-reddening-corrected PLC relation yields an rms scatter of ±0.04 mag, corresponding to ∼2% precision in distance per star. The use of a physically grounded PLC will provide a more robust foundation for the Cepheid-based extragalactic distance scale and the determination of the Hubble constant.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"340 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147279367","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 : 2026-02-25DOI: 10.3847/1538-4357/ae3c7e
Monalisa Dubey, Kuntal Misra, Géza Csörnyei, Raya Dastidar, D. Andrew Howell, David J. Sand, Stefano Valenti, WeiKang Zheng, Alexei V. Filippenko, Saurabh Jha, Jesper Sollerman, Peter Brown, Kate D. Alexander, Moira Andrews, Jennifer Andrews, Dre Betz, Emma Born, Kate Bostow, K. Azalee Bostroem, Sea’n J. Brennan, Thomas G. Brink, Collin Christy, Elma Chuang, Yize Dong, Naveen Dukiya, Joseph R. Farah, Noah Franz, Estefania Padilla Gonzalez, Joshua Haislip, Emily Hoang, Griffin Hosseinzadeh, Brian Hsu, Connor Jennings, Vladimir Kouprianov, M. J. Lundquist, Colin Macrie, Curtis McCully, Andrew Mchaty, Darshana Mehta, Katie Mora, Megan Newsome, Jeniveve Pearson, Neil Pichay, Conor Ransome, Aravind P. Ravi, Daniel E. Reichart, Nicolás Meza Retamal, Sophia Risin, Manisha Shrestha, Ajay Kumar Singh, Nathan Smith, Bhagya Subrayan, Giacomo Terreran and William Wu
We present a detailed photometric and spectroscopic analysis of the Type IIP supernova (SN) SN 2023zcu, which exploded in the galaxy NGC 2139 (redshift z = 0.006). SN 2023zcu exhibits a well-sampled light curve covering the rise, plateau, and nebular phases. It has an optically thick phase of 100.6 ± 0.6 days with a magnitude drop of ∼1.7 mag in the V band during the transition between the plateau and nebular phases. Weak emission features in the early-time spectra indicate a low-level interaction between circumstellar material and the SN ejecta. The spectral evolution is well sampled and exhibits a prominent P Cygni profile of Hα, a defining characteristic of Type IIP SNe. Signatures of metal-line formation (e.g., Fe ii, Ca ii near-infrared triplet) are also evident in the spectra as the SN evolves. Spectral modeling with the radiative transfer code TARDIS during the early photospheric phase (8.7–35.5 days since explosion) yields photospheric temperatures decreasing from ∼9000 to ∼6000 K and expansion velocities declining from ∼10,000 to ∼5400 km s−1. A tailored expanding photosphere method fit based on the TARDIS models provides a distance estimate of 27.8 ± 2.0 Mpc. Nebular-phase spectra and bolometric light-curve modeling suggest a progenitor mass in the range 12–15 M⊙. This thorough analysis helps to constrain progenitor properties and explosion parameters, thereby strengthening our understanding of Type IIP SNe.
我们对在NGC 2139星系中爆炸的IIP型超新星SN 2023zcu（红移z = 0.006）进行了详细的光度和光谱分析。SN 2023zcu展示了一个采样良好的光曲线，覆盖了上升、平台和星云相。它的光学厚相位为100.6±0.6天，在平台相和星云相之间的过渡期间，V波段的星等下降了约1.7等。早期光谱中的弱发射特征表明星周物质与SN抛射物之间存在低水平的相互作用。光谱演化得到了很好的采样，并显示出一个突出的P Cygni Hα剖面，这是IIP型SNe的一个定义特征。随着SN的演化，金属线形成的特征（如Fe ii， Ca ii近红外三重态）在光谱中也很明显。辐射传输代码TARDIS在早期光球阶段（爆炸后8.7-35.5天）的光谱模拟结果显示，光球温度从~ 9000 K下降到~ 6000 K，膨胀速度从~ 10,000 km s−1下降到~ 5400 km s−1。基于TARDIS模型的定制扩展光球方法拟合提供了27.8±2.0 Mpc的距离估计。星云相位光谱和测热光曲线模型表明其前身质量在12-15 M⊙之间。这种深入的分析有助于约束前驱性质和爆炸参数，从而加强我们对IIP型SNe的理解。
{"title":"SN 2023zcu: A Type IIP SN with Early Flash Features","authors":"Monalisa Dubey, Kuntal Misra, Géza Csörnyei, Raya Dastidar, D. Andrew Howell, David J. Sand, Stefano Valenti, WeiKang Zheng, Alexei V. Filippenko, Saurabh Jha, Jesper Sollerman, Peter Brown, Kate D. Alexander, Moira Andrews, Jennifer Andrews, Dre Betz, Emma Born, Kate Bostow, K. Azalee Bostroem, Sea’n J. Brennan, Thomas G. Brink, Collin Christy, Elma Chuang, Yize Dong, Naveen Dukiya, Joseph R. Farah, Noah Franz, Estefania Padilla Gonzalez, Joshua Haislip, Emily Hoang, Griffin Hosseinzadeh, Brian Hsu, Connor Jennings, Vladimir Kouprianov, M. J. Lundquist, Colin Macrie, Curtis McCully, Andrew Mchaty, Darshana Mehta, Katie Mora, Megan Newsome, Jeniveve Pearson, Neil Pichay, Conor Ransome, Aravind P. Ravi, Daniel E. Reichart, Nicolás Meza Retamal, Sophia Risin, Manisha Shrestha, Ajay Kumar Singh, Nathan Smith, Bhagya Subrayan, Giacomo Terreran and William Wu","doi":"10.3847/1538-4357/ae3c7e","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3c7e","url":null,"abstract":"We present a detailed photometric and spectroscopic analysis of the Type IIP supernova (SN) SN 2023zcu, which exploded in the galaxy NGC 2139 (redshift z = 0.006). SN 2023zcu exhibits a well-sampled light curve covering the rise, plateau, and nebular phases. It has an optically thick phase of 100.6 ± 0.6 days with a magnitude drop of ∼1.7 mag in the V band during the transition between the plateau and nebular phases. Weak emission features in the early-time spectra indicate a low-level interaction between circumstellar material and the SN ejecta. The spectral evolution is well sampled and exhibits a prominent P Cygni profile of Hα, a defining characteristic of Type IIP SNe. Signatures of metal-line formation (e.g., Fe ii, Ca ii near-infrared triplet) are also evident in the spectra as the SN evolves. Spectral modeling with the radiative transfer code TARDIS during the early photospheric phase (8.7–35.5 days since explosion) yields photospheric temperatures decreasing from ∼9000 to ∼6000 K and expansion velocities declining from ∼10,000 to ∼5400 km s−1. A tailored expanding photosphere method fit based on the TARDIS models provides a distance estimate of 27.8 ± 2.0 Mpc. Nebular-phase spectra and bolometric light-curve modeling suggest a progenitor mass in the range 12–15 M⊙. This thorough analysis helps to constrain progenitor properties and explosion parameters, thereby strengthening our understanding of Type IIP SNe.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147279368","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 : 2026-02-25DOI: 10.3847/1538-4357/ae42cf
L. Xiang, D. J. Wu, L. Chen, Q. H. Li, G. Q. Zhao and H. Q. Feng
Kinetic Alfvén waves (KAWs) are ubiquitous in space and solar plasmas and are believed to be crucial for energy transfer and particle energization. Existing studies on KAWs primarily focus on the low-frequency approximation, where the wave frequency is much smaller than the proton cyclotron frequency (i.e., ω ≪ ωcp). However, the wave properties of high-frequency KAWs with ω ≳ ωcp remain unclear. In this work, based on the two-fluid theory, we derive a general dispersion relation for KAWs spanning low-frequency to high-frequency regimes, and examine this dispersion relation and the electromagnetic properties of both low-frequency and high-frequency KAWs. Our findings reveal that, compared to low-frequency KAWs, high-frequency KAWs exhibit several distinct features: higher wave frequency (ω ≳ ωcp), propagation angle over a broader oblique angle range, significantly larger ratio of parallel to perpendicular electric field, and the magnetic helicity and magnetic compressibility that are highly sensitive to the plasma beta. The enhanced parallel electric field highlights the pivotal role of high-frequency KAWs in field-aligned particle acceleration. This work extends KAW theory to the high-frequency domain, providing key insights into KAW properties and the particle acceleration process in space and solar plasmas.
{"title":"On High-frequency Kinetic Alfvén Waves in Space and Solar Plasma","authors":"L. Xiang, D. J. Wu, L. Chen, Q. H. Li, G. Q. Zhao and H. Q. Feng","doi":"10.3847/1538-4357/ae42cf","DOIUrl":"https://doi.org/10.3847/1538-4357/ae42cf","url":null,"abstract":"Kinetic Alfvén waves (KAWs) are ubiquitous in space and solar plasmas and are believed to be crucial for energy transfer and particle energization. Existing studies on KAWs primarily focus on the low-frequency approximation, where the wave frequency is much smaller than the proton cyclotron frequency (i.e., ω ≪ ωcp). However, the wave properties of high-frequency KAWs with ω ≳ ωcp remain unclear. In this work, based on the two-fluid theory, we derive a general dispersion relation for KAWs spanning low-frequency to high-frequency regimes, and examine this dispersion relation and the electromagnetic properties of both low-frequency and high-frequency KAWs. Our findings reveal that, compared to low-frequency KAWs, high-frequency KAWs exhibit several distinct features: higher wave frequency (ω ≳ ωcp), propagation angle over a broader oblique angle range, significantly larger ratio of parallel to perpendicular electric field, and the magnetic helicity and magnetic compressibility that are highly sensitive to the plasma beta. The enhanced parallel electric field highlights the pivotal role of high-frequency KAWs in field-aligned particle acceleration. This work extends KAW theory to the high-frequency domain, providing key insights into KAW properties and the particle acceleration process in space and solar plasmas.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147278959","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 : 2026-02-25DOI: 10.3847/1538-4357/ae3b29
Yao Guo, Dong Wu and Jie Zhang
Mushroom instability (MI) is a shear instability considered to be related to generating and amplifying magnetic fields in relativistic jets. While astrophysical jets are usually magnetized, how MI acts in magnetized jets remains poorly understood. In this paper, we investigate the effect of a flow-aligned external magnetic field on MI with both theoretical analyses and particle-in-cell (PIC) simulations. In the limit of a cold and collisionless plasma, we derive a generalized dispersion relation for linear growth rates of the magnetized MIs. Numerical solutions of the dispersion relation reveal that the external magnetic field always suppresses MI, though MIs are more robust against the field than electron-scale Kelvin–Helmholtz instabilities. Replacing protons in the shear flow with positrons enhances the instability growth in weakly magnetized regimes but suppresses it in strongly magnetized cases. Analyses are also extended to instabilities with an arbitrary wavevector in the shear interface plane, where a coupling effect is observed for subrelativistic scenarios. The 2D PIC simulations of single-mode MIs reach a good agreement with our analytical predictions, and we observe formation of a quasi-steady saturation structure of electrons in magnetized runs. In simulations with finite temperatures, we observe the competition and cooperation between MIs and a diffusion-induced direct current magnetic field.
{"title":"Effect of Flow-aligned External Magnetic Fields on Mushroom Instability","authors":"Yao Guo, Dong Wu and Jie Zhang","doi":"10.3847/1538-4357/ae3b29","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3b29","url":null,"abstract":"Mushroom instability (MI) is a shear instability considered to be related to generating and amplifying magnetic fields in relativistic jets. While astrophysical jets are usually magnetized, how MI acts in magnetized jets remains poorly understood. In this paper, we investigate the effect of a flow-aligned external magnetic field on MI with both theoretical analyses and particle-in-cell (PIC) simulations. In the limit of a cold and collisionless plasma, we derive a generalized dispersion relation for linear growth rates of the magnetized MIs. Numerical solutions of the dispersion relation reveal that the external magnetic field always suppresses MI, though MIs are more robust against the field than electron-scale Kelvin–Helmholtz instabilities. Replacing protons in the shear flow with positrons enhances the instability growth in weakly magnetized regimes but suppresses it in strongly magnetized cases. Analyses are also extended to instabilities with an arbitrary wavevector in the shear interface plane, where a coupling effect is observed for subrelativistic scenarios. The 2D PIC simulations of single-mode MIs reach a good agreement with our analytical predictions, and we observe formation of a quasi-steady saturation structure of electrons in magnetized runs. In simulations with finite temperatures, we observe the competition and cooperation between MIs and a diffusion-induced direct current magnetic field.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147279365","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 : 2026-02-25DOI: 10.3847/1538-4357/ae3f1d
Dongtao Cao and Shenghong Gu
Stellar coronal mass ejections (CMEs) have significant impacts on surrounding exoplanets and stellar evolution. For M-type dwarf stars, hosting close-in habitable zones, frequent and intense stellar CMEs may render their potentially habitable planets uninhabitable. In this study, we used the CARMENES DR 1 spectra to investigate potential stellar CMEs in M-type dwarfs by analyzing asymmetric features of the Hα profiles. Through a comprehensive visual inspection, we identified 61 distinct asymmetric features in the Hα line profiles across 33 M-type dwarfs. These asymmetries were associated with increased emissions in several chromospheric activity lines, indicating likely connections to flare events. The velocities of these features remain below the escape velocities of the investigated stars, except for one case where an asymmetric feature’s maximum velocity approaches the star’s escape velocity. While stellar CMEs are one potential explanation, the observed features are also consistent with other flare-related plasma motions. The estimated moving plasma masses range from 1015 to 1019 g, with corresponding kinetic energies of 1029 to 1032 erg. Stars with asymmetric Hα profiles are generally associated with stronger surface-average magnetic field (〈B〉) and higher normalized X-ray luminosity (log ). However, we find no significant correlation between the line asymmetry rate and either 〈B〉 or log .
恒星日冕物质抛射（cme）对周围系外行星和恒星演化具有重要影响。对于m型矮星来说，拥有近距离的宜居带，频繁而强烈的恒星cme可能会使它们可能适合居住的行星变得不适合居住。在这项研究中，我们利用CARMENES DR 1光谱通过分析Hα谱线的不对称特征来研究m型矮星中潜在的恒星cme。通过全面的目视检查，我们在33个m型矮星的Hα线剖面中发现了61个明显的不对称特征。这些不对称与几个色球活动线的辐射增加有关，表明可能与耀斑事件有关。这些特征的速度仍然低于被研究恒星的逃逸速度，除了一个不对称特征的最大速度接近恒星的逃逸速度的情况。虽然恒星日冕物质抛射是一种可能的解释，但观测到的特征也与其他与耀斑相关的等离子体运动一致。估计的运动等离子体质量范围为1015至1019g，对应的动能为1029至1032erg。具有不对称Hα谱线的恒星通常具有较强的表面平均磁场（< B >）和较高的归一化x射线光度（log）。然而，我们发现线不对称率与< B >或log之间没有显著的相关性。
{"title":"Investigating Possible Stellar Coronal Mass Ejections in M-type Dwarfs Using the CARMENES Data Release 1 Spectra","authors":"Dongtao Cao and Shenghong Gu","doi":"10.3847/1538-4357/ae3f1d","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3f1d","url":null,"abstract":"Stellar coronal mass ejections (CMEs) have significant impacts on surrounding exoplanets and stellar evolution. For M-type dwarf stars, hosting close-in habitable zones, frequent and intense stellar CMEs may render their potentially habitable planets uninhabitable. In this study, we used the CARMENES DR 1 spectra to investigate potential stellar CMEs in M-type dwarfs by analyzing asymmetric features of the Hα profiles. Through a comprehensive visual inspection, we identified 61 distinct asymmetric features in the Hα line profiles across 33 M-type dwarfs. These asymmetries were associated with increased emissions in several chromospheric activity lines, indicating likely connections to flare events. The velocities of these features remain below the escape velocities of the investigated stars, except for one case where an asymmetric feature’s maximum velocity approaches the star’s escape velocity. While stellar CMEs are one potential explanation, the observed features are also consistent with other flare-related plasma motions. The estimated moving plasma masses range from 1015 to 1019 g, with corresponding kinetic energies of 1029 to 1032 erg. Stars with asymmetric Hα profiles are generally associated with stronger surface-average magnetic field (〈B〉) and higher normalized X-ray luminosity (log ). However, we find no significant correlation between the line asymmetry rate and either 〈B〉 or log .","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"52 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147278950","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 : 2026-02-25DOI: 10.3847/1538-4357/ae42be
Rebecca C. Chen, Zhiyuan Guo, 致远 郭, Dan Scolnic, Bhavin Joshi, Richard Kessler, Lluís Galbany, Rebekah Hounsell, Diane M. Markoff, Benjamin M. Rose, David Rubin and The Roman Supernova Cosmology Project Infrastructure Team
The High-latitude Time-domain Survey (HLTDS) for the Nancy Grace Roman Space Telescope (Roman) will discover thousands of high-redshift Type Ia supernovae (SNe Ia) to set generation-defining cosmological constraints on dark energy. To construct the Roman SN Hubble diagram, a strategy to obtain redshifts must be determined. While the nominal HLTDS will use only the Roman prism, in this work, we consider the utility of the Roman grism observations from overlap with the High-latitude Wide-area Survey for SN Ia cosmology. We determine a galaxy grism redshift recovery rate by simulating dispersed grism images and measuring redshifts with the Grizli software, obtaining an H-band 50% redshift recovery at magnitude 20.61 and 90% recovery at magnitude 19.27. To estimate the total number of spectroscopic redshifts expected for Roman SN cosmology, we also consider a Roman prism SN redshift efficiency and a ground-based telescope redshift efficiency for host galaxies. We apply these redshift efficiencies to SN Ia catalog-level simulations and predict that ∼6800 SNe will have an SN or host spectroscopic redshift. Second, we evaluate the size of potential systematics related to modeling the grism redshift efficiency by considering the impact of additional dependences on stellar mass and host-galaxy color. We estimate the largest potential size of this systematic to be 0.0066 ± 0.002 and −0.0266 ± 0.0079, roughly 42.9% and 49.6% of the statistical uncertainty, for w0 and wa, respectively. Lastly, we consider the effects of assuming different redshift sources on the optimization of the HLTDS survey strategy by measuring relative changes to the dark energy figure of merit.
{"title":"Characterizing the Roman Grism Redshift Efficiency of Type Ia Supernova Host Galaxies for the High-latitude Time-domain Survey","authors":"Rebecca C. Chen, Zhiyuan Guo, 致远 郭, Dan Scolnic, Bhavin Joshi, Richard Kessler, Lluís Galbany, Rebekah Hounsell, Diane M. Markoff, Benjamin M. Rose, David Rubin and The Roman Supernova Cosmology Project Infrastructure Team","doi":"10.3847/1538-4357/ae42be","DOIUrl":"https://doi.org/10.3847/1538-4357/ae42be","url":null,"abstract":"The High-latitude Time-domain Survey (HLTDS) for the Nancy Grace Roman Space Telescope (Roman) will discover thousands of high-redshift Type Ia supernovae (SNe Ia) to set generation-defining cosmological constraints on dark energy. To construct the Roman SN Hubble diagram, a strategy to obtain redshifts must be determined. While the nominal HLTDS will use only the Roman prism, in this work, we consider the utility of the Roman grism observations from overlap with the High-latitude Wide-area Survey for SN Ia cosmology. We determine a galaxy grism redshift recovery rate by simulating dispersed grism images and measuring redshifts with the Grizli software, obtaining an H-band 50% redshift recovery at magnitude 20.61 and 90% recovery at magnitude 19.27. To estimate the total number of spectroscopic redshifts expected for Roman SN cosmology, we also consider a Roman prism SN redshift efficiency and a ground-based telescope redshift efficiency for host galaxies. We apply these redshift efficiencies to SN Ia catalog-level simulations and predict that ∼6800 SNe will have an SN or host spectroscopic redshift. Second, we evaluate the size of potential systematics related to modeling the grism redshift efficiency by considering the impact of additional dependences on stellar mass and host-galaxy color. We estimate the largest potential size of this systematic to be 0.0066 ± 0.002 and −0.0266 ± 0.0079, roughly 42.9% and 49.6% of the statistical uncertainty, for w0 and wa, respectively. Lastly, we consider the effects of assuming different redshift sources on the optimization of the HLTDS survey strategy by measuring relative changes to the dark energy figure of merit.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147278958","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 : 2026-02-25DOI: 10.3847/1538-4357/ae3bdb
Shaheda Begum Shaik, Guillermo Stenborg, Phillip Hess, Angelos Vourlidas, Karl Battams and Robin Colaninno
Comet C/2023 P1 (Nishimura) was observed by the Solar Orbiter Heliospheric Imager (SoloHI), on board the Solar Orbiter spacecraft, from 2023 September 1 to 14. During this period, the ion tail of the comet exhibited continual fluctuations and four tail disconnection events (TDEs), each coinciding with the passage of a coronal mass ejection (CME). In this work, we report on the ion tail dynamics of the best observed TDE, which occurred on September 11. The SoloHI white-light images reveal an abrupt bending, subsequent kinks, and severing of a downstream portion of the preexisting ion tail. The onset of disconnection occurred ∼6.5 hr after the projected passage of the CME leading edge in the images, consistent with a CME flank encounter. After the disconnection, the ion tail reformed in over ∼24 hr, with a regrowth rate of ∼86 ± 7 km s−1, indicating the rate at which newly ionized material forms along the magnetic field draped around the comet’s coma. After the TDE, the detached tail drifted anti-sunward at an estimated speed of ∼295 ± 20 km s−1, comparable to the local CME flank’s speed, suggesting that the severed plasma was most likely carried away from the comet by the CME. This study provides the first direct, quantitative characterization of comet–CME interactions and the subsequent regrowth phase of a cometary TDE. These measurements were achievable by SoloHI’s unique inner-heliospheric coverage, thanks to a combination of high photometric sensitivity, short exposure times, and a wide field of view that preserves the fine-scale tail dynamics.
彗星C/2023 P1（西村）是由太阳轨道飞行器上的太阳轨道日光层成像仪（SoloHI）于2023年9月1日至14日观测到的。在此期间，彗星的离子尾部呈现出持续的波动和四次尾部断开事件（TDEs），每次都与日冕物质抛射（CME）的通过相吻合。在这项工作中，我们报告了发生在9月11日的最佳观测TDE的离子尾动力学。SoloHI的白光图像显示了一个突然的弯曲，随后的扭结，以及先前存在的尾部下游部分的切断。分离发生在CME前缘投影通过图像后约6.5小时，与CME侧面相遇一致。断开后，离子尾巴在约24小时内重新形成，再生速率为~ 86±7 km s−1，这表明新电离物质沿着覆盖在彗星彗发周围的磁场形成的速率。在TDE之后，分离的彗尾反太阳方向漂移，估计速度为~ 295±20 km s−1，与当地CME侧面的速度相当，这表明分离的等离子体很可能是被CME带离彗星的。这项研究提供了彗星- cme相互作用的第一个直接的、定量的特征，以及随后彗星TDE的再生阶段。这些测量是通过SoloHI独特的内部日球覆盖来实现的，这要归功于高光度灵敏度、短曝光时间和宽视场的结合，从而保留了精细的尾部动力学。
{"title":"The First Quantitative Study of Cometary Tail Regrowth following a Coronal Mass Ejection-driven Disconnection Event","authors":"Shaheda Begum Shaik, Guillermo Stenborg, Phillip Hess, Angelos Vourlidas, Karl Battams and Robin Colaninno","doi":"10.3847/1538-4357/ae3bdb","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3bdb","url":null,"abstract":"Comet C/2023 P1 (Nishimura) was observed by the Solar Orbiter Heliospheric Imager (SoloHI), on board the Solar Orbiter spacecraft, from 2023 September 1 to 14. During this period, the ion tail of the comet exhibited continual fluctuations and four tail disconnection events (TDEs), each coinciding with the passage of a coronal mass ejection (CME). In this work, we report on the ion tail dynamics of the best observed TDE, which occurred on September 11. The SoloHI white-light images reveal an abrupt bending, subsequent kinks, and severing of a downstream portion of the preexisting ion tail. The onset of disconnection occurred ∼6.5 hr after the projected passage of the CME leading edge in the images, consistent with a CME flank encounter. After the disconnection, the ion tail reformed in over ∼24 hr, with a regrowth rate of ∼86 ± 7 km s−1, indicating the rate at which newly ionized material forms along the magnetic field draped around the comet’s coma. After the TDE, the detached tail drifted anti-sunward at an estimated speed of ∼295 ± 20 km s−1, comparable to the local CME flank’s speed, suggesting that the severed plasma was most likely carried away from the comet by the CME. This study provides the first direct, quantitative characterization of comet–CME interactions and the subsequent regrowth phase of a cometary TDE. These measurements were achievable by SoloHI’s unique inner-heliospheric coverage, thanks to a combination of high photometric sensitivity, short exposure times, and a wide field of view that preserves the fine-scale tail dynamics.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147279366","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 : 2026-02-25DOI: 10.3847/1538-4357/ae3da0
Nguyen Thi Phuong and Nguyen Tat Thang
We present Atacama Large Millimeter/submillimeter Array observations of multiwavelength dust emissions at 3.1 and 1.3 mm, along with molecular line emissions of CO(2–1), CO(3–2), 13CO(3–2), and C18O(3–2) at spatial resolutions of 7–45 au toward the protoplanetary system AS 205. The dust emissions exhibit two distinct components of AS 205 N and AS 205 S, separated by 1 3. While gas kinematics within the dust disk regions are dominated by Keplerian rotation, the more extended gas emission displays complex morphology and kinematics strongly affected by the binary gravitational interaction in the outer regions. The stellar masses of AS 205 N and AS 205 S are estimated at 0.78 ± 0.19 and 1.93 ± 0.86 M⊙, respectively. Azimuthal variation is observed in the spectral index distribution of both disks. In AS 205 N, the spectral index minimum in the southwest is coincident with the peaks of CO(2–1), CO(3–2), and 13CO(3–2) integrated intensity and the relative position of its southern counterpart. On the other hand, the spectral index distribution in AS 205 S exhibits two prominent maxima, with the one in the northeast aligning with the peak of 13CO(3–2), and the peak in the south coinciding with local maxima in CO(2–1) and CO(3–2) azimuthal profiles. These results suggest a correlation between dust grain size and/or optical depth with the gas distributions. Dust trapping along the spiral arms possibly contributes to the spectral index minima in AS 205 N; however, the observed asymmetry across both disks suggests the involvement of additional mechanisms.
{"title":"A Multiwavelength ALMA View of Gas and Dust in Binary Protoplanetary System AS 205: Evidence of Dust Asymmetric Distribution","authors":"Nguyen Thi Phuong and Nguyen Tat Thang","doi":"10.3847/1538-4357/ae3da0","DOIUrl":"https://doi.org/10.3847/1538-4357/ae3da0","url":null,"abstract":"We present Atacama Large Millimeter/submillimeter Array observations of multiwavelength dust emissions at 3.1 and 1.3 mm, along with molecular line emissions of CO(2–1), CO(3–2), 13CO(3–2), and C18O(3–2) at spatial resolutions of 7–45 au toward the protoplanetary system AS 205. The dust emissions exhibit two distinct components of AS 205 N and AS 205 S, separated by 1 3. While gas kinematics within the dust disk regions are dominated by Keplerian rotation, the more extended gas emission displays complex morphology and kinematics strongly affected by the binary gravitational interaction in the outer regions. The stellar masses of AS 205 N and AS 205 S are estimated at 0.78 ± 0.19 and 1.93 ± 0.86 M⊙, respectively. Azimuthal variation is observed in the spectral index distribution of both disks. In AS 205 N, the spectral index minimum in the southwest is coincident with the peaks of CO(2–1), CO(3–2), and 13CO(3–2) integrated intensity and the relative position of its southern counterpart. On the other hand, the spectral index distribution in AS 205 S exhibits two prominent maxima, with the one in the northeast aligning with the peak of 13CO(3–2), and the peak in the south coinciding with local maxima in CO(2–1) and CO(3–2) azimuthal profiles. These results suggest a correlation between dust grain size and/or optical depth with the gas distributions. Dust trapping along the spiral arms possibly contributes to the spectral index minima in AS 205 N; however, the observed asymmetry across both disks suggests the involvement of additional mechanisms.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"104 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147279369","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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