Pub Date : 2026-01-20DOI: 10.3847/2041-8213/ae346f
Danial Langeroodi and Jens Hjorth
We introduce genesis-metallicity, a gas-phase metallicity measurement Python software employing the direct and strong-line methods depending on the available oxygen lines. The nonparametric strong-line estimator is calibrated based on a kernel density estimate in the four-dimensional space of O2 = [O ii]λλ3727,29/Hβ; O3 = [O iii]λ5007/Hβ; Hβ equivalent width EW(Hβ); and gas-phase metallicity . We use a calibration sample of 1510 galaxies at 0 < z < 10 with direct-method metallicity measurements, compiled from the JWST/NIRSpec and ground-based observations. In particular, we report 122 new NIRSpec direct-method metallicity measurements at z > 1. We show that the O2, O3, and EW(Hβ) measurements are sufficient for a gas-phase metallicity estimate that is more accurate than 0.09 dex. Our calibration is universal, meaning that its accuracy does not depend on the target redshift. Furthermore, the direct-method module employs a nonparametric Te(O ii) electron temperature estimator based on a kernel density estimate in the five-dimensional space of O2, O3, EW(Hβ), Te(O ii), and Te(O iii). This Te(O ii) estimator is calibrated based on 1004 spectra with detections of both [O iii]λ4363 and [O ii]λλ7320,30, notably reporting 20 new NIRSpec detections of the [O ii]λλ7320,30 doublet. We make genesis-metallicity and its calibration data publicly available and commit to keeping both up to date in light of the incoming data.
{"title":"Genesis-metallicity: Universal Nonparametric Gas-phase Metallicity Estimation","authors":"Danial Langeroodi and Jens Hjorth","doi":"10.3847/2041-8213/ae346f","DOIUrl":"https://doi.org/10.3847/2041-8213/ae346f","url":null,"abstract":"We introduce genesis-metallicity, a gas-phase metallicity measurement Python software employing the direct and strong-line methods depending on the available oxygen lines. The nonparametric strong-line estimator is calibrated based on a kernel density estimate in the four-dimensional space of O2 = [O ii]λλ3727,29/Hβ; O3 = [O iii]λ5007/Hβ; Hβ equivalent width EW(Hβ); and gas-phase metallicity . We use a calibration sample of 1510 galaxies at 0 < z < 10 with direct-method metallicity measurements, compiled from the JWST/NIRSpec and ground-based observations. In particular, we report 122 new NIRSpec direct-method metallicity measurements at z > 1. We show that the O2, O3, and EW(Hβ) measurements are sufficient for a gas-phase metallicity estimate that is more accurate than 0.09 dex. Our calibration is universal, meaning that its accuracy does not depend on the target redshift. Furthermore, the direct-method module employs a nonparametric Te(O ii) electron temperature estimator based on a kernel density estimate in the five-dimensional space of O2, O3, EW(Hβ), Te(O ii), and Te(O iii). This Te(O ii) estimator is calibrated based on 1004 spectra with detections of both [O iii]λ4363 and [O ii]λλ7320,30, notably reporting 20 new NIRSpec detections of the [O ii]λλ7320,30 doublet. We make genesis-metallicity and its calibration data publicly available and commit to keeping both up to date in light of the incoming data.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"273 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146001547","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 : 2026-01-19DOI: 10.3847/2041-8213/ae33bf
Pinjian Chen, Bingqiu Chen, Xiaodian Chen, Haibo Yuan, Jianrong Shi, Shu Wang, Chunqian Li, Jiyu Wang, Jianxing Zhang and Yi Ren
We report the discovery of LAMOST J0041+3948, the most luminous post-asymptotic giant-branch (AGB) Type II Cepheid known, located in the Andromeda Giant Stellar Stream. Its spectral energy distribution (SED) exhibits a strong near-infrared excess, indicating the presence of a circumbinary dusty disk and hence binarity. SED fitting yields an effective temperature of K and a post-AGB luminosity of . Comparison with theoretical evolutionary tracks suggests a ∼2.0–4.0 M⊙ progenitor when accounting for a possible scattered-light contribution. Zwicky Transient Facility light curves reveal a pulsation period of 89 days that lies close to the period–luminosity relation for long-period RV Tauri stars. Follow-up spectroscopy reveals clear s-process enrichment and signatures consistent with an accretion disk around the companion. The inferred progenitor is significantly younger and more massive than a typical stream member, suggesting that an additional mechanism, such as a stellar merger, is required. We propose a formation channel in which the present post-AGB binary descends from a hierarchical triple system. In this scenario, the inner binary merged after the system was displaced to its current location by the galaxy merger event, and the resulting massive merger remnant subsequently evolved into the extremely luminous post-AGB star observed today.
{"title":"Discovery of an Extremely Luminous Type II Cepheid in the Andromeda Giant Stellar Stream: Evidence for a Hierarchical Triple with an Inner Binary Merger","authors":"Pinjian Chen, Bingqiu Chen, Xiaodian Chen, Haibo Yuan, Jianrong Shi, Shu Wang, Chunqian Li, Jiyu Wang, Jianxing Zhang and Yi Ren","doi":"10.3847/2041-8213/ae33bf","DOIUrl":"https://doi.org/10.3847/2041-8213/ae33bf","url":null,"abstract":"We report the discovery of LAMOST J0041+3948, the most luminous post-asymptotic giant-branch (AGB) Type II Cepheid known, located in the Andromeda Giant Stellar Stream. Its spectral energy distribution (SED) exhibits a strong near-infrared excess, indicating the presence of a circumbinary dusty disk and hence binarity. SED fitting yields an effective temperature of K and a post-AGB luminosity of . Comparison with theoretical evolutionary tracks suggests a ∼2.0–4.0 M⊙ progenitor when accounting for a possible scattered-light contribution. Zwicky Transient Facility light curves reveal a pulsation period of 89 days that lies close to the period–luminosity relation for long-period RV Tauri stars. Follow-up spectroscopy reveals clear s-process enrichment and signatures consistent with an accretion disk around the companion. The inferred progenitor is significantly younger and more massive than a typical stream member, suggesting that an additional mechanism, such as a stellar merger, is required. We propose a formation channel in which the present post-AGB binary descends from a hierarchical triple system. In this scenario, the inner binary merged after the system was displaced to its current location by the galaxy merger event, and the resulting massive merger remnant subsequently evolved into the extremely luminous post-AGB star observed today.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"88 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995194","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 : 2026-01-19DOI: 10.3847/2041-8213/ae307d
Fatima Zaidouni, Erin Kara, Peter Kosec, Ehud Behar, Richard Mushotzky, Michael Koss, A. Juráňová, Elias Kammoun, Laura W. Brenneman, Joheen Chakraborty, Ken Ebisawa, Megan E. Eckart, Andrew C. Fabian, Yasushi Fukazawa, Javier A. García, Liyi Gu, Megan Masterson, Shoji Ogawa, Takashi Okajima, Stéphane Paltani, Daniele Rogantini, Yuichi Terashima, Brian J. Williams and Satoshi Yamada
We present the first XRISM/Resolve observations of the active galactic nucleus NGC 1365, obtained in 2024 February and July. NGC 1365 is known for rapid transitions between Compton-thick and Compton-thin states, along with strong absorption from a highly ionized wind. During our observations, the source was found in a persistent low-flux state, characterized by a decrease in hard-X-ray luminosity and significant line-of-sight obscuration. In this state, XRISM/Resolve reveals clear Fe xxv and Fe xxvi absorption lines together with, for the first time in this source, corresponding emission lines. These features may arise either from reemission from a photoionized wind (P Cygni profile) or from collisionally ionized gas associated with outflow-driven shocks in the interstellar medium. We estimate the wind launch radius to be approximately 1016 cm (∼104Rg), consistent with the location of the X-ray broadline region. We also resolve a broadened Fe Kα line by σ ∼ 1300 km s−1, placing it at similar scales to the wind, consistent with radii inferred from disk-broadening models and the variability of the Fe Kα broad line. The similarity of the Fe Kα profile to the Hβ wing and broad Paα width indicates that the X-ray-emitting region is likely cospatial with the optical/infrared broadline region and originates from the same gas.
我们展示了第一次XRISM/Resolve观测到的活动星系核NGC 1365，于2024年2月和7月获得。NGC 1365以在康普顿厚态和康普顿薄态之间的快速转变而闻名，同时还具有高度电离风的强吸收。在我们的观察中，发现源处于持续的低通量状态，其特征是硬x射线亮度下降和明显的视线遮挡。在这种状态下，XRISM/Resolve显示出清晰的fexxv和fexxvi吸收谱线，并在该源中首次显示出相应的发射谱线。这些特征可能是由光电离风（Cygni P剖面）的再发射引起的，也可能是由与星际介质中流出驱动的激波有关的碰撞电离气体引起的。我们估计风发射半径约为1016 cm (~ 104Rg)，与x射线宽线区域的位置一致。我们还通过σ ~ 1300 km s−1解析了一个加宽的铁Kα线，将其放置在与风相似的尺度上，与从圆盘加宽模型推断的半径和铁Kα宽线的变变性相一致。Fe - k - α谱线与h - β翼的相似性和较宽的pa - α谱线表明，x射线发射区可能与光学/红外宽谱区在同一空间，并且来自同一气体。
{"title":"XRISM Finds the Changing-look Active Galactic Nucleus NGC 1365 in an Extended Low State: A Dense, Highly Ionized Outflow Obscures the Central Source","authors":"Fatima Zaidouni, Erin Kara, Peter Kosec, Ehud Behar, Richard Mushotzky, Michael Koss, A. Juráňová, Elias Kammoun, Laura W. Brenneman, Joheen Chakraborty, Ken Ebisawa, Megan E. Eckart, Andrew C. Fabian, Yasushi Fukazawa, Javier A. García, Liyi Gu, Megan Masterson, Shoji Ogawa, Takashi Okajima, Stéphane Paltani, Daniele Rogantini, Yuichi Terashima, Brian J. Williams and Satoshi Yamada","doi":"10.3847/2041-8213/ae307d","DOIUrl":"https://doi.org/10.3847/2041-8213/ae307d","url":null,"abstract":"We present the first XRISM/Resolve observations of the active galactic nucleus NGC 1365, obtained in 2024 February and July. NGC 1365 is known for rapid transitions between Compton-thick and Compton-thin states, along with strong absorption from a highly ionized wind. During our observations, the source was found in a persistent low-flux state, characterized by a decrease in hard-X-ray luminosity and significant line-of-sight obscuration. In this state, XRISM/Resolve reveals clear Fe xxv and Fe xxvi absorption lines together with, for the first time in this source, corresponding emission lines. These features may arise either from reemission from a photoionized wind (P Cygni profile) or from collisionally ionized gas associated with outflow-driven shocks in the interstellar medium. We estimate the wind launch radius to be approximately 1016 cm (∼104Rg), consistent with the location of the X-ray broadline region. We also resolve a broadened Fe Kα line by σ ∼ 1300 km s−1, placing it at similar scales to the wind, consistent with radii inferred from disk-broadening models and the variability of the Fe Kα broad line. The similarity of the Fe Kα profile to the Hβ wing and broad Paα width indicates that the X-ray-emitting region is likely cospatial with the optical/infrared broadline region and originates from the same gas.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"121 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995192","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 : 2026-01-19DOI: 10.3847/2041-8213/ae3174
Sébastien Le Stum, Floriane Cangemi, Alexis Coleiro, Sébastien Guillot, Jérôme Chenevez, Philippe Bacon, Nicolas Bellemont, Laurent Bouchet, Tristan Bouchet, Cécile Cavet, Bertrand Cordier, Antoine Foisseau, Olivier Godet, Andrea Goldwurm, Xuhui Han, Cyril Lachaud, Zhaosheng Li, Huali Li, Yulei Qiu, Jérôme Rodriguez, Wenjun Tan, Lian Tao, Lauryne Verwaerde, Chenwei Wang, Jing Wang, Jianyan Wei, Chao Wu, Wenjin Xie, Liping Xin, Shaolin Xiong, Shuangnan Zhang and Shijie Zheng
On 2025 January 10, a thermonuclear (Type I) X-ray burst from the neutron star low-mass X-ray binary (LMXB) 4U 0614+091 was detected with the ECLAIRs instrument on board the Space-based multiband astronomical Variable Object Monitor mission. We present here a time-resolved spectroscopic analysis of the burst, along with the detection of burst oscillations within a 51 s interval during the decay phase. The oscillation frequency is measured to be ν = 413.674 ± 0.002 Hz, consistent with previous reports. However, we detect a significant downward frequency drift over the burst duration, characterized by . This frequency evolution is atypical compared to those observed in similar burst oscillation sources. We tentatively attribute the observed drift to a Doppler shift induced by orbital motion. Under this interpretation, the inferred orbital period must be shorter than 20 minutes, placing 4U 0614+091 among the most compact known LMXBs.
{"title":"Detection of Oscillations in a Type I X-Ray Burst of 4U 0614+091 with SVOM/ECLAIRs","authors":"Sébastien Le Stum, Floriane Cangemi, Alexis Coleiro, Sébastien Guillot, Jérôme Chenevez, Philippe Bacon, Nicolas Bellemont, Laurent Bouchet, Tristan Bouchet, Cécile Cavet, Bertrand Cordier, Antoine Foisseau, Olivier Godet, Andrea Goldwurm, Xuhui Han, Cyril Lachaud, Zhaosheng Li, Huali Li, Yulei Qiu, Jérôme Rodriguez, Wenjun Tan, Lian Tao, Lauryne Verwaerde, Chenwei Wang, Jing Wang, Jianyan Wei, Chao Wu, Wenjin Xie, Liping Xin, Shaolin Xiong, Shuangnan Zhang and Shijie Zheng","doi":"10.3847/2041-8213/ae3174","DOIUrl":"https://doi.org/10.3847/2041-8213/ae3174","url":null,"abstract":"On 2025 January 10, a thermonuclear (Type I) X-ray burst from the neutron star low-mass X-ray binary (LMXB) 4U 0614+091 was detected with the ECLAIRs instrument on board the Space-based multiband astronomical Variable Object Monitor mission. We present here a time-resolved spectroscopic analysis of the burst, along with the detection of burst oscillations within a 51 s interval during the decay phase. The oscillation frequency is measured to be ν = 413.674 ± 0.002 Hz, consistent with previous reports. However, we detect a significant downward frequency drift over the burst duration, characterized by . This frequency evolution is atypical compared to those observed in similar burst oscillation sources. We tentatively attribute the observed drift to a Doppler shift induced by orbital motion. Under this interpretation, the inferred orbital period must be shorter than 20 minutes, placing 4U 0614+091 among the most compact known LMXBs.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"383 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995193","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 : 2026-01-15DOI: 10.3847/2041-8213/ae3186
Shravan M. Hanasoge
Compressible Rossby waves—long predicted by theories of rotating stratified convection—offer a unique window into the dynamical structure of the solar interior. Despite their foundational status in astrophysical convection theory, they have evaded unambiguous detection for more than half a century. Analyzing nearly 15 yr of space- and ground-based helioseismic observations using normal-mode coupling, we report the discovery of a coherent, dispersive family of prograde inertial vorticity waves confined to depths below r/R⊙ < 0.98, with amplitudes <10 cm s−1, at spatial harmonic degrees ranging up to s ∼ 75, and oscillating at temporal frequencies comparable to the solar rotation rate. Convection drives fluid flows, which, in the parameter regime that applies to the Sun, are likely turbulent. We argue that our measurements hint at convective extinction below r/R⊙ ∼ 0.98, thereby marking a transition from vigorous surface turbulence to rotationally constrained (Rossby number ∼10−4–10−3), weakly turbulent (<3 m s−1) dynamics.
可压缩罗斯比波——长期以来由旋转分层对流理论预测——为研究太阳内部的动力结构提供了一个独特的窗口。尽管它们在天体物理对流理论中处于基础地位，但半个多世纪以来，它们一直没有被明确地探测到。利用正模耦合分析近15年的空间和地面日震观测，我们报告发现了一个相干的、色散的顺行惯性涡度波族，其深度小于r/ r⊙< 0.98，振幅<10 cm s−1，空间谐波度范围高达s ~ 75，振荡的时间频率与太阳自转速率相当。对流驱动流体流动，在适用于太阳的参数体系中，流体流动可能是湍流的。我们认为，我们的测量表明，在r/ r⊙~ 0.98以下存在对流消光，从而标志着从强烈的表面湍流到旋转约束（罗斯比数~ 10−4 ~ 10−3）、弱湍流（<3 m s−1）动力学的转变。
{"title":"Discovery of Thermal Rossby Waves and Evidence for Weak Large-scale Convection in the Solar Interior","authors":"Shravan M. Hanasoge","doi":"10.3847/2041-8213/ae3186","DOIUrl":"https://doi.org/10.3847/2041-8213/ae3186","url":null,"abstract":"Compressible Rossby waves—long predicted by theories of rotating stratified convection—offer a unique window into the dynamical structure of the solar interior. Despite their foundational status in astrophysical convection theory, they have evaded unambiguous detection for more than half a century. Analyzing nearly 15 yr of space- and ground-based helioseismic observations using normal-mode coupling, we report the discovery of a coherent, dispersive family of prograde inertial vorticity waves confined to depths below r/R⊙ < 0.98, with amplitudes <10 cm s−1, at spatial harmonic degrees ranging up to s ∼ 75, and oscillating at temporal frequencies comparable to the solar rotation rate. Convection drives fluid flows, which, in the parameter regime that applies to the Sun, are likely turbulent. We argue that our measurements hint at convective extinction below r/R⊙ ∼ 0.98, thereby marking a transition from vigorous surface turbulence to rotationally constrained (Rossby number ∼10−4–10−3), weakly turbulent (<3 m s−1) dynamics.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"101 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145968555","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 : 2026-01-15DOI: 10.3847/2041-8213/ae32f6
T. R. Hunter, C. L. Brogan, G. C. MacLeod, C. J. Cyganowski, R. A. Burns and B. A. McGuire
We present multiepoch, multiband Atacama Large Millimeter/submillimeter Array imaging of the new Class II millimeter methanol masers excited during the accretion outburst of the massive protostar G358.93−0.03 MM1. The highest angular resolution image (24 mas ≈160 au) reveals a nearly complete, circular ring of strong maser spots in the 217.2992 GHz (vt = 1) maser line that closely circumscribes the dust continuum emission from MM1. Weaker maser emission lies inside the eastern and southern halves of the maser ring, generally coincident with the centimeter masers excited during the outburst but avoiding the densest parts of the hot core gas traced by high excitation lines of CH3CN. Using a variety of fitting techniques on the image cubes of the two strongest maser lines, each observed over three to four epochs, we find the diameter of the ring increased by ≳60% (from ≈1100 to ≈1800 au in the 217 GHz line) over 200 days, consistent with an average radial propagation rate of ≈0.01c, while the maser intensity declined exponentially. Fitting the angular extent of the millimeter masers versus time yields a power law of index 0.39 ± 0.06, which also reproduces the observed extent of the 6.7 GHz masers in the first very long baseline interferometry epoch of R. A. Burns et al. 2020 This exponent is consistent with the prediction of radius versus time in the Taylor–von Neumann–Sedov self-similar solution for an intense spherical explosion from a point source (R ∝ t2/5). These results demonstrate the explosive nature of accretion outbursts in massive protostars and their ability to generate subluminal heat waves traceable by centimeter and millimeter masers for several months as the energy traverses the surrounding molecular material.
{"title":"A Millimeter Methanol Maser Ring Tracing the Deceleration of the Heat Wave Powered by the Massive Protostellar Accretion Outburst in G358.93–0.03 MM1","authors":"T. R. Hunter, C. L. Brogan, G. C. MacLeod, C. J. Cyganowski, R. A. Burns and B. A. McGuire","doi":"10.3847/2041-8213/ae32f6","DOIUrl":"https://doi.org/10.3847/2041-8213/ae32f6","url":null,"abstract":"We present multiepoch, multiband Atacama Large Millimeter/submillimeter Array imaging of the new Class II millimeter methanol masers excited during the accretion outburst of the massive protostar G358.93−0.03 MM1. The highest angular resolution image (24 mas ≈160 au) reveals a nearly complete, circular ring of strong maser spots in the 217.2992 GHz (vt = 1) maser line that closely circumscribes the dust continuum emission from MM1. Weaker maser emission lies inside the eastern and southern halves of the maser ring, generally coincident with the centimeter masers excited during the outburst but avoiding the densest parts of the hot core gas traced by high excitation lines of CH3CN. Using a variety of fitting techniques on the image cubes of the two strongest maser lines, each observed over three to four epochs, we find the diameter of the ring increased by ≳60% (from ≈1100 to ≈1800 au in the 217 GHz line) over 200 days, consistent with an average radial propagation rate of ≈0.01c, while the maser intensity declined exponentially. Fitting the angular extent of the millimeter masers versus time yields a power law of index 0.39 ± 0.06, which also reproduces the observed extent of the 6.7 GHz masers in the first very long baseline interferometry epoch of R. A. Burns et al. 2020 This exponent is consistent with the prediction of radius versus time in the Taylor–von Neumann–Sedov self-similar solution for an intense spherical explosion from a point source (R ∝ t2/5). These results demonstrate the explosive nature of accretion outbursts in massive protostars and their ability to generate subluminal heat waves traceable by centimeter and millimeter masers for several months as the energy traverses the surrounding molecular material.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145968641","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 : 2026-01-15DOI: 10.3847/2041-8213/ae331c
Stephen DiKerby, Shuo Zhang, Kumiko K. Nobukawa, Masayoshi Nobukawa, Yuma Aoki and Jack Uteg
Fe Kα line emission from Galactic center molecular clouds can be produced either via fluorescence after illumination by an X-ray source or by cosmic-ray ionization. Unparalleled high-resolution X-ray spectroscopy obtained by XRISM/Resolve for the Galactic center molecular cloud G0.11-0.11 resolves its Fe Kα line complex for the first time, and points to a new method for discrimination between the X-ray reflection and cosmic-ray ionization models. The Fe Kα line complex is resolved into Fe Kα1 at E1 = 6.4040 keV and Fe Kα2 at E2 = 6.3910 keV. Both lines have noninstrumental FWHM of ≈3 eV, close to the predicted quantum mechanical width of the lines, suggesting scant other sources of line broadening other than instrumental and quantum effects. We measure a radial velocity of vLSR = 50 ± 12fit ± 14scale km s−1 for G0.11-0.11, achieving the same precision reached by radio observations of such clouds. The high-resolution spectrum tests for the presence of secondary Fe Kα lines, expected as a signature of cosmic-ray proton/ion ionization. The absence of the secondary lines argues against the cosmic-ray ionization model for G0.11-0.11. In the preferred X-ray reflection model, if the illuminating source is Sgr A⋆, the required luminosity for an X-ray outburst about 200 yr ago is L8 ≈ 1038 erg s−1 in an 8 keV wide band at 8 keV.
银河系中心分子云的铁Kα线发射可以通过x射线源照射后的荧光或宇宙射线电离产生。利用XRISM/Resolve对银河系中心分子云G0.11-0.11进行了空前的高分辨率x射线光谱分析，首次解析出其Fe - k - α线配合物，为区分x射线反射模型和宇宙射线电离模型提供了一种新的方法。Fe Kα线配合物在E1 = 6.4040 keV下分解为Fe Kα1和E2 = 6.3910 keV下分解为Fe Kα2。两条谱线的非仪器FWHM约为3ev，接近于谱线的量子力学宽度，这表明除了仪器和量子效应之外，谱线的增宽几乎没有其他来源。我们测量了G0.11-0.11的径向速度vLSR = 50±12fit±14尺度km s - 1，达到了与射电观测相同的精度。高分辨率光谱测试表明，次级Fe - k - α谱线的存在，有望作为宇宙射线质子/离子电离的标志。次级线的缺失反驳了G0.11-0.11的宇宙射线电离模型。在首选的x射线反射模型中，如果照明源是Sgr A - -，则大约200年前的x射线爆发所需的光度为L8≈1038 erg s−1，在8 keV的8 keV宽带内。
{"title":"Resolving the Fe Kα Doublet of the Galactic Center Molecular Cloud G0.11-0.11 with XRISM","authors":"Stephen DiKerby, Shuo Zhang, Kumiko K. Nobukawa, Masayoshi Nobukawa, Yuma Aoki and Jack Uteg","doi":"10.3847/2041-8213/ae331c","DOIUrl":"https://doi.org/10.3847/2041-8213/ae331c","url":null,"abstract":"Fe Kα line emission from Galactic center molecular clouds can be produced either via fluorescence after illumination by an X-ray source or by cosmic-ray ionization. Unparalleled high-resolution X-ray spectroscopy obtained by XRISM/Resolve for the Galactic center molecular cloud G0.11-0.11 resolves its Fe Kα line complex for the first time, and points to a new method for discrimination between the X-ray reflection and cosmic-ray ionization models. The Fe Kα line complex is resolved into Fe Kα1 at E1 = 6.4040 keV and Fe Kα2 at E2 = 6.3910 keV. Both lines have noninstrumental FWHM of ≈3 eV, close to the predicted quantum mechanical width of the lines, suggesting scant other sources of line broadening other than instrumental and quantum effects. We measure a radial velocity of vLSR = 50 ± 12fit ± 14scale km s−1 for G0.11-0.11, achieving the same precision reached by radio observations of such clouds. The high-resolution spectrum tests for the presence of secondary Fe Kα lines, expected as a signature of cosmic-ray proton/ion ionization. The absence of the secondary lines argues against the cosmic-ray ionization model for G0.11-0.11. In the preferred X-ray reflection model, if the illuminating source is Sgr A⋆, the required luminosity for an X-ray outburst about 200 yr ago is L8 ≈ 1038 erg s−1 in an 8 keV wide band at 8 keV.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145968556","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 : 2026-01-15DOI: 10.3847/2041-8213/ae2916
Chunhua Qi, David J. Wilner and Catherine C. Espaillat
Isotopic abundance ratios in protoplanetary disks are critical for understanding volatile inheritance and chemical evolution in planet-forming environments. We present Atacama Large Millimeter/submillimeter Array observations of the rare isotopologue 13C18O(2–1) at ∼0 3 resolution from the disk around the Herbig Ae star HD 163296, combined with archival observations of C17O(2–1), C18O(1–0), and C17O(1–0), to empirically constrain carbon and oxygen isotopic ratios without detailed disk modeling. Both the C17O/13C18O(2–1) and C18O/C17O(1–0) flux ratios rise sharply across the CO snowline and flatten beyond 1 5 (r ≳ 150 au), where the emission becomes optically thin. This transition, reflecting a steep drop in CO column density set by the disk’s thermal structure, makes HD 163296 an optimal case for isotopic analysis. Using beam-averaged intensities of the four transitions measured in this optically thin region, we derive isotopic ratios of 12C/13C = and 18O/17O = , both consistent with local interstellar medium values. The 16O/18O ratio remains weakly constrained due to moderate optical depth in the C18O(1–0) line and degeneracy with CO column density. These results demonstrate that rare CO isotopologues can provide robust, empirical constraints on isotopic ratios in disks when sharp structural transitions allow for the identification of optically thin regions, and establish HD 163296 as a benchmark for extending such studies to other systems with resolved snowline structures.
{"title":"Isotopic Ratios in the Disk of HD 163296","authors":"Chunhua Qi, David J. Wilner and Catherine C. Espaillat","doi":"10.3847/2041-8213/ae2916","DOIUrl":"https://doi.org/10.3847/2041-8213/ae2916","url":null,"abstract":"Isotopic abundance ratios in protoplanetary disks are critical for understanding volatile inheritance and chemical evolution in planet-forming environments. We present Atacama Large Millimeter/submillimeter Array observations of the rare isotopologue 13C18O(2–1) at ∼0 3 resolution from the disk around the Herbig Ae star HD 163296, combined with archival observations of C17O(2–1), C18O(1–0), and C17O(1–0), to empirically constrain carbon and oxygen isotopic ratios without detailed disk modeling. Both the C17O/13C18O(2–1) and C18O/C17O(1–0) flux ratios rise sharply across the CO snowline and flatten beyond 1 5 (r ≳ 150 au), where the emission becomes optically thin. This transition, reflecting a steep drop in CO column density set by the disk’s thermal structure, makes HD 163296 an optimal case for isotopic analysis. Using beam-averaged intensities of the four transitions measured in this optically thin region, we derive isotopic ratios of 12C/13C = and 18O/17O = , both consistent with local interstellar medium values. The 16O/18O ratio remains weakly constrained due to moderate optical depth in the C18O(1–0) line and degeneracy with CO column density. These results demonstrate that rare CO isotopologues can provide robust, empirical constraints on isotopic ratios in disks when sharp structural transitions allow for the identification of optically thin regions, and establish HD 163296 as a benchmark for extending such studies to other systems with resolved snowline structures.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145968554","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 : 2026-01-14DOI: 10.3847/2041-8213/ae2ed4
Aman Priyadarshi M. Kumar, Juie Shetye, Sean G. Sellers and Damian J. Christian
We present a uniform analysis of compact Ca ii K (3934 Å) brightenings that occur near flare kernels and assess their value as short-lead indicators of solar flare onset. Using high-cadence imaging from the Rapid Oscillations in the Solar Atmosphere instrument at the Dunn Solar Telescope, we examine eight flare sequences (seven C-class and one B-class) obtained between 2021 and 2025. Fixed, detector-coordinate regions of interest are used to generate mean-intensity light curves, which are detrended and smoothed to isolate impulsive brightenings. In every event, a compact Ca ii K brightening is detected within or adjacent to the flaring region that peaks 10–45 minutes before the primary kernel and the corresponding rise in GOES 1–8 Å flux. The measured temporal offsets scale with the deprojected separation between the brightening and flare kernels, implying an apparent propagation speed of ∼30–35 km s−1 that is consistent with chromospheric reconnection. Complementary Spectropolarimeter for Infrared and Optical Regions spectropolarimetry for one event shows topological reconfiguration from closed to open or extended connectivity, supporting a reconnection-driven origin. These results demonstrate that compact Ca ii K brightenings are reproducible, physically meaningful precursors to flare onset. Their simplicity and cadence make them attractive chromospheric indicators, and future work will evaluate their predictive skill alongside established UV/EUV and magnetic diagnostics.
我们对发生在耀斑核附近的致密Ca ii K （3934 Å）亮度进行了统一分析，并评估了它们作为太阳耀斑发生的短导联指标的价值。利用邓恩太阳望远镜太阳大气快速振荡仪器的高节奏成像，我们研究了2021年至2025年间获得的8个耀斑序列（7个c级和1个b级）。固定的、感兴趣的探测器坐标区域被用来生成平均强度光曲线，这些光曲线被去趋势化和平滑以隔离脉冲亮度。在每个事件中，在耀斑区域内或附近都检测到紧凑的Ca ii K增亮，该区域在主核之前10-45分钟达到峰值，并且GOES 1-8 Å通量相应上升。测量到的时间偏移与增亮和耀斑核之间的去投影分离成比例，表明表观传播速度为~ 30-35 km s−1，与色球重联一致。一个事件的互补分光偏振仪显示从闭合到开放或扩展连接的拓扑重构，支持重新连接驱动的原点。这些结果表明，致密的Ca ii K亮是可重复的，物理上有意义的耀斑发作的前兆。它们的简单和节奏使它们成为有吸引力的色球指示器，未来的工作将评估它们的预测能力，以及建立的UV/EUV和磁诊断。
{"title":"Compact Ca II K Brightenings Precede Solar Flares: A Dunn Solar Telescope Pilot Study","authors":"Aman Priyadarshi M. Kumar, Juie Shetye, Sean G. Sellers and Damian J. Christian","doi":"10.3847/2041-8213/ae2ed4","DOIUrl":"https://doi.org/10.3847/2041-8213/ae2ed4","url":null,"abstract":"We present a uniform analysis of compact Ca ii K (3934 Å) brightenings that occur near flare kernels and assess their value as short-lead indicators of solar flare onset. Using high-cadence imaging from the Rapid Oscillations in the Solar Atmosphere instrument at the Dunn Solar Telescope, we examine eight flare sequences (seven C-class and one B-class) obtained between 2021 and 2025. Fixed, detector-coordinate regions of interest are used to generate mean-intensity light curves, which are detrended and smoothed to isolate impulsive brightenings. In every event, a compact Ca ii K brightening is detected within or adjacent to the flaring region that peaks 10–45 minutes before the primary kernel and the corresponding rise in GOES 1–8 Å flux. The measured temporal offsets scale with the deprojected separation between the brightening and flare kernels, implying an apparent propagation speed of ∼30–35 km s−1 that is consistent with chromospheric reconnection. Complementary Spectropolarimeter for Infrared and Optical Regions spectropolarimetry for one event shows topological reconfiguration from closed to open or extended connectivity, supporting a reconnection-driven origin. These results demonstrate that compact Ca ii K brightenings are reproducible, physically meaningful precursors to flare onset. Their simplicity and cadence make them attractive chromospheric indicators, and future work will evaluate their predictive skill alongside established UV/EUV and magnetic diagnostics.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145962055","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 : 2026-01-14DOI: 10.3847/2041-8213/ae3239
E. J. Zirnstein, F. Fraternale, N. V. Pogorelov and R. K. Bera
The Interstellar Mapping and Acceleration Probe (IMAP) mission launched from Earth on 2025 September 24, beginning its commissioning phase as the spacecraft makes its way to Lagrange Point 1. IMAP-Hi, one of three energetic neutral atom (ENA) imagers, has improved capabilities compared to its predecessor, the Interstellar Boundary Explorer-Hi instrument, such as a wider energy coverage (∼0.4–15.6 keV compared to ∼0.5–6 keV). In this study, we aim to simulate ENA emissions from the heliosphere, at IMAP-Hi energies, with the goal of showing what ENA maps may look like when their source is affected by the presence of the Kelvin–Helmholtz instability (KHI). The KHI arises when the fast and slow solar wind meet in the heliosheath near the heliopause and create a shear flow, usually strongest at high latitudes. According to our simulation, if the KHIs are present in the heliosphere, then IMAP-Hi should be able to observe their effects on ENA emissions via long bands of enhanced ENA fluxes at high northern and southern latitudes, reaching all the way back to the tail. These bands are separated on the order of ∼15° in latitude, depending on the direction in the sky. The ENA bands are most visible at ∼2–6 keV. The presence or absence of ENA bands in IMAP-Hi observations and their orientation may not only provide important information about the structure of the heliosphere, but also guide improvements to our models, since these features differ or are not present among various simulations.
{"title":"Kelvin–Helmholtz Instability and Energetic Neutral Atoms in the Heliosphere","authors":"E. J. Zirnstein, F. Fraternale, N. V. Pogorelov and R. K. Bera","doi":"10.3847/2041-8213/ae3239","DOIUrl":"https://doi.org/10.3847/2041-8213/ae3239","url":null,"abstract":"The Interstellar Mapping and Acceleration Probe (IMAP) mission launched from Earth on 2025 September 24, beginning its commissioning phase as the spacecraft makes its way to Lagrange Point 1. IMAP-Hi, one of three energetic neutral atom (ENA) imagers, has improved capabilities compared to its predecessor, the Interstellar Boundary Explorer-Hi instrument, such as a wider energy coverage (∼0.4–15.6 keV compared to ∼0.5–6 keV). In this study, we aim to simulate ENA emissions from the heliosphere, at IMAP-Hi energies, with the goal of showing what ENA maps may look like when their source is affected by the presence of the Kelvin–Helmholtz instability (KHI). The KHI arises when the fast and slow solar wind meet in the heliosheath near the heliopause and create a shear flow, usually strongest at high latitudes. According to our simulation, if the KHIs are present in the heliosphere, then IMAP-Hi should be able to observe their effects on ENA emissions via long bands of enhanced ENA fluxes at high northern and southern latitudes, reaching all the way back to the tail. These bands are separated on the order of ∼15° in latitude, depending on the direction in the sky. The ENA bands are most visible at ∼2–6 keV. The presence or absence of ENA bands in IMAP-Hi observations and their orientation may not only provide important information about the structure of the heliosphere, but also guide improvements to our models, since these features differ or are not present among various simulations.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145962140","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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