Pub Date : 2026-01-20DOI: 10.3847/1538-4357/ae25e6
Xianming Zheng, Mihailo M. Martinović, Kristopher G. Klein, Viviane Pierrard, Mingzhe Liu, Yang Wang, Tao Wu, Winry Ember, Jingchun Li, Naomi Maruyama, Yutian Chi, Yao Yao, Bingkun Yu and Xianghui Xue
Quasi-thermal noise is an important diagnostic tool for measuring electron density and temperature in space plasmas, with its low-frequency range being dominated by electron shot noise. However, previous missions have shown that conventional shot noise models often yield poor fits in the low frequency , limiting the accurate characterization of electron parameters. To address this issue, we introduce an effective sheath resistance into the previous model, thereby establishing a calibrated shot noise model that improves measurements of electron parameters in the inner heliosphere. Methodologically, we applied the steep-descent and Levenberg–Marquardt method algorithm to determine the electron density and temperature above the plasma frequency; we then isolate the pure shot noise by subtracting other noise sources; and finally, we derive the antenna impedance using measurements below the plasma frequency ( ). Based on Parker Solar Probe (PSP) observations during PSP Encounter 4 ∼ 8 (with unbiased antennas operating in the dipole regime), we obtain an effective antenna capacitance of and an effective resistance in the range of 0.5 ∼ 4 MΩ, with their radial of the capacitances and resistances of and , respectively.
准热噪声是测量空间等离子体中电子密度和温度的重要诊断工具，其低频范围以电子散粒噪声为主。然而，之前的任务表明，传统的散粒噪声模型在低频下的拟合效果很差，限制了电子参数的准确表征。为了解决这个问题，我们在之前的模型中引入了有效的鞘层电阻，从而建立了一个校准的散粒噪声模型，该模型改进了对内日球层电子参数的测量。在方法上，我们采用陡坡下降法和Levenberg-Marquardt算法来确定等离子体频率以上的电子密度和温度；然后，我们通过减去其他噪声源分离出纯散粒噪声；最后，我们使用低于等离子体频率（）的测量来推导天线阻抗。基于帕克太阳探测器（Parker Solar Probe， PSP）在PSP遭遇4 ~ 8（无偏置天线在偶极子区工作）期间的观测，我们获得了有效天线电容和有效电阻在0.5 ~ 4 MΩ范围内，其径向分别为和的电容和电阻。
{"title":"First in Situ Estimates of the Sheath Resistance for the PSP/FIELD Antenna: Employing an Electron Shot Noise Model","authors":"Xianming Zheng, Mihailo M. Martinović, Kristopher G. Klein, Viviane Pierrard, Mingzhe Liu, Yang Wang, Tao Wu, Winry Ember, Jingchun Li, Naomi Maruyama, Yutian Chi, Yao Yao, Bingkun Yu and Xianghui Xue","doi":"10.3847/1538-4357/ae25e6","DOIUrl":"https://doi.org/10.3847/1538-4357/ae25e6","url":null,"abstract":"Quasi-thermal noise is an important diagnostic tool for measuring electron density and temperature in space plasmas, with its low-frequency range being dominated by electron shot noise. However, previous missions have shown that conventional shot noise models often yield poor fits in the low frequency , limiting the accurate characterization of electron parameters. To address this issue, we introduce an effective sheath resistance into the previous model, thereby establishing a calibrated shot noise model that improves measurements of electron parameters in the inner heliosphere. Methodologically, we applied the steep-descent and Levenberg–Marquardt method algorithm to determine the electron density and temperature above the plasma frequency; we then isolate the pure shot noise by subtracting other noise sources; and finally, we derive the antenna impedance using measurements below the plasma frequency ( ). Based on Parker Solar Probe (PSP) observations during PSP Encounter 4 ∼ 8 (with unbiased antennas operating in the dipole regime), we obtain an effective antenna capacitance of and an effective resistance in the range of 0.5 ∼ 4 MΩ, with their radial of the capacitances and resistances of and , respectively.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"230 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146000821","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 : 2026-01-20DOI: 10.3847/1538-4357/ae1f0b
Nibedita Mondal, Sandeep Kumar Mondal and Nayantara Gupta
The detection of very-high-energy gamma rays from M87 can provide crucial insights into particle acceleration and radiation mechanisms in jets. The recent observations by the Large High Altitude Air Shower Observatory detector extend the energy range of TeV gamma-ray astronomy, and also the variability study to the TeV energy domain. We have modeled the low state and flare state multiwavelength spectral energy distributions of M87 within a time-dependent framework. In our model, the low state gamma-ray flux results from the emissions from the subparsec and the kiloparsec scale jets of M87, whereas the flare state gamma-ray flux is mainly produced in the subparsec scale jet. We have shown that the spectral and temporal features of the TeV gamma-ray spectrum of M87 are consistent with this two-zone model, where the contribution from the subparsec scale jet significantly increases during the flare state.
{"title":"Explaining the Origin of TeV Gamma Rays from M87 during High and Low States","authors":"Nibedita Mondal, Sandeep Kumar Mondal and Nayantara Gupta","doi":"10.3847/1538-4357/ae1f0b","DOIUrl":"https://doi.org/10.3847/1538-4357/ae1f0b","url":null,"abstract":"The detection of very-high-energy gamma rays from M87 can provide crucial insights into particle acceleration and radiation mechanisms in jets. The recent observations by the Large High Altitude Air Shower Observatory detector extend the energy range of TeV gamma-ray astronomy, and also the variability study to the TeV energy domain. We have modeled the low state and flare state multiwavelength spectral energy distributions of M87 within a time-dependent framework. In our model, the low state gamma-ray flux results from the emissions from the subparsec and the kiloparsec scale jets of M87, whereas the flare state gamma-ray flux is mainly produced in the subparsec scale jet. We have shown that the spectral and temporal features of the TeV gamma-ray spectrum of M87 are consistent with this two-zone model, where the contribution from the subparsec scale jet significantly increases during the flare state.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146000816","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 : 2026-01-20DOI: 10.3847/1538-4357/ae2c83
Yang Sun, Zhiyuan Ji, George H. Rieke, Francesco D’Eugenio, Yongda Zhu, Fengwu Sun, Xiaojing Lin, Andrew J. Bunker, Jianwei Lyu, 建伟 吕, Pierluigi Rinaldi and Christopher N. A. Willmer
We report the discovery of a substantial sodium doublet (Na D λλ5890, 5896)—traced neutral outflow in the quiescent galaxy JADES-GS-206183 at z = 1.317. Its JWST/NIRSpec-Microshutter Array spectrum shows a deep, blueshifted Na D absorption, revealing a neutral outflow with and a mass outflow rate of . This outflow rate exceeds that of any neutral outflows identified beyond z ∼ 1 by the same line and is comparable with those in local galaxies with intensive star formation (SF) or luminous active galactic nuclei (AGN). JADES-GS-206183 is also a peculiar quiescent galaxy with a spiral+bar morphology, high dust attenuation (AV = 2.27 ± 0.23 mag). Paschen α (Paα) emission from the FRESCO NIRCam grism confirms its low star formation rate (SFRPaα = 10.78 ± 0.55 M⊙ yr−1), placing it 0.5 dex below the main sequence ( ). Despite the systematics introduced by different SF history priors, the spectral energy distribution modeling, combining Hubble Space Telescope-to-NIRCam photometry with the Very Large Telescope/MUSE spectrum, suggests that JADES-GS-206183 experienced an older episode of SF 0.5–2 Gyr ago and a possible rejuvenation within the recent ∼10 Myr. Moreover, rest-frame optical lines indicate that the current AGN activity of JADES-GS-206183, if present, is also weak. Even though we tentatively detect a broad component of the Hα line, it likely traces an ionized outflow rather than an AGN. The results demonstrate that the Na D outflow in JADES-GS-206183 is highly unlikely to be driven by current SF or nuclear activity. Instead, it may represent a long-lasting fossil outflow from past AGN activity, potentially cotriggered with the early phase of rejuvenation.
{"title":"Extreme Neutral Outflow in a Non-active Galactic Nucleus Quiescent Galaxy at z ∼ 1.3","authors":"Yang Sun, Zhiyuan Ji, George H. Rieke, Francesco D’Eugenio, Yongda Zhu, Fengwu Sun, Xiaojing Lin, Andrew J. Bunker, Jianwei Lyu, 建伟 吕, Pierluigi Rinaldi and Christopher N. A. Willmer","doi":"10.3847/1538-4357/ae2c83","DOIUrl":"https://doi.org/10.3847/1538-4357/ae2c83","url":null,"abstract":"We report the discovery of a substantial sodium doublet (Na D λλ5890, 5896)—traced neutral outflow in the quiescent galaxy JADES-GS-206183 at z = 1.317. Its JWST/NIRSpec-Microshutter Array spectrum shows a deep, blueshifted Na D absorption, revealing a neutral outflow with and a mass outflow rate of . This outflow rate exceeds that of any neutral outflows identified beyond z ∼ 1 by the same line and is comparable with those in local galaxies with intensive star formation (SF) or luminous active galactic nuclei (AGN). JADES-GS-206183 is also a peculiar quiescent galaxy with a spiral+bar morphology, high dust attenuation (AV = 2.27 ± 0.23 mag). Paschen α (Paα) emission from the FRESCO NIRCam grism confirms its low star formation rate (SFRPaα = 10.78 ± 0.55 M⊙ yr−1), placing it 0.5 dex below the main sequence ( ). Despite the systematics introduced by different SF history priors, the spectral energy distribution modeling, combining Hubble Space Telescope-to-NIRCam photometry with the Very Large Telescope/MUSE spectrum, suggests that JADES-GS-206183 experienced an older episode of SF 0.5–2 Gyr ago and a possible rejuvenation within the recent ∼10 Myr. Moreover, rest-frame optical lines indicate that the current AGN activity of JADES-GS-206183, if present, is also weak. Even though we tentatively detect a broad component of the Hα line, it likely traces an ionized outflow rather than an AGN. The results demonstrate that the Na D outflow in JADES-GS-206183 is highly unlikely to be driven by current SF or nuclear activity. Instead, it may represent a long-lasting fossil outflow from past AGN activity, potentially cotriggered with the early phase of rejuvenation.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"266 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146001531","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 : 2026-01-20DOI: 10.3847/1538-4357/ae1d65
Madalyn F. Chapleski and Yifan Zhou
The L/T transition is a critical evolutionary stage for brown dwarfs and self-luminous giant planets. L/T transition brown dwarfs are more likely to be spectroscopically variable, and their high-amplitude variability probes distributions in their clouds and chemical makeup. This paper presents Hubble Space Telescope Wide Field Camera 3 spectral time-series data for three variable L/T transition brown dwarfs and compares the findings to the highly variable benchmark object 2MASS J2139. All four targets reveal significant brightness variability between 1.1 and 1.65 μm but show a difference in wavelength dependence of the variability amplitude. Three of our targets do not show significant decrease in variability amplitude in the 1.4 μm water absorption band commonly found in previous studies of L/T transition brown dwarfs. Additionally, at least two brown dwarfs have irregular-shaped, nonsinusoidal light curves. We create heterogeneous atmospheric models by linearly combining SONORA Diamondback model spectra, comparing them with the observations, and identifying the optimal effective temperature, cloud opacity, and cloud coverage for each object. Comparisons between the observed and model color–magnitude variations that trace both spectral windows and molecular features reveal that the early-T dwarfs likely possess heterogeneous clouds. The three T dwarfs show different trends in the same color–magnitude space, which suggests secondary mechanisms driving their spectral variability. This work broadens the sample of L/T transition brown dwarfs that have detailed spectral time-series analysis and offers new insights that can guide future atmospheric modeling efforts for both brown dwarfs and exoplanets.
{"title":"Gray Spectral Variability in Three Brown Dwarfs Observed by HST/WFC3 Time-series Observations","authors":"Madalyn F. Chapleski and Yifan Zhou","doi":"10.3847/1538-4357/ae1d65","DOIUrl":"https://doi.org/10.3847/1538-4357/ae1d65","url":null,"abstract":"The L/T transition is a critical evolutionary stage for brown dwarfs and self-luminous giant planets. L/T transition brown dwarfs are more likely to be spectroscopically variable, and their high-amplitude variability probes distributions in their clouds and chemical makeup. This paper presents Hubble Space Telescope Wide Field Camera 3 spectral time-series data for three variable L/T transition brown dwarfs and compares the findings to the highly variable benchmark object 2MASS J2139. All four targets reveal significant brightness variability between 1.1 and 1.65 μm but show a difference in wavelength dependence of the variability amplitude. Three of our targets do not show significant decrease in variability amplitude in the 1.4 μm water absorption band commonly found in previous studies of L/T transition brown dwarfs. Additionally, at least two brown dwarfs have irregular-shaped, nonsinusoidal light curves. We create heterogeneous atmospheric models by linearly combining SONORA Diamondback model spectra, comparing them with the observations, and identifying the optimal effective temperature, cloud opacity, and cloud coverage for each object. Comparisons between the observed and model color–magnitude variations that trace both spectral windows and molecular features reveal that the early-T dwarfs likely possess heterogeneous clouds. The three T dwarfs show different trends in the same color–magnitude space, which suggests secondary mechanisms driving their spectral variability. This work broadens the sample of L/T transition brown dwarfs that have detailed spectral time-series analysis and offers new insights that can guide future atmospheric modeling efforts for both brown dwarfs and exoplanets.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"272 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146000817","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 : 2026-01-20DOI: 10.3847/1538-4357/ae25ea
Ming-Xuan Lu, Yun-Feng Liang, Xiang-Gao Wang and Hao-Qiang Zhang
Type IIn supernovae (SNe IIn) are a subclass of core-collapse SNe in which strong interactions occur between the ejecta and dense circumstellar material, creating ideal conditions for the production of high-energy neutrinos. This makes them promising candidate sources of neutrinos. In this work, we conduct an association study between 163 SNe IIn observed by the Zwicky Transient Facility and 138 neutrino alert events detected by the IceCube Neutrino Observatory. After excluding alerts with poor localization, we find two SNe that are spatiotemporally coincident with neutrino events. IC 231027A and IC 250421A coincide with the positions of SN 2023syz and SN 2025cbj, respectively, within their localization uncertainties, and the neutrino arrival times are delayed by 38 days and 61 days relative to the discovery times of the corresponding SNe. Using Monte Carlo simulations, we estimate that the probability of two such events occurring by chance in our sample is p ∼ 0.67%, suggesting that they may originate from genuine physical associations, though the result is not yet statistically significant. Our model calculations, however, indicate that the likelihood of a neutrino originating from IC 231027A is low, implying that the association between IC 231027A and SN 2023syz is likely coincidental. Nevertheless, under optimistic parameters, the probability of detecting a neutrino from the whole SNe IIn sample could reach ≳6%, indicating that detecting neutrino emission from the SNe population may be possible. Our study provides a systematic analysis, combining statistical analysis and model calculations, to assess whether interacting supernovae can serve as potential sources of neutrino emission.
{"title":"SN 2023syz and SN 2025cbj: Two Type IIn Supernovae Associated with IceCube High-energy Neutrinos","authors":"Ming-Xuan Lu, Yun-Feng Liang, Xiang-Gao Wang and Hao-Qiang Zhang","doi":"10.3847/1538-4357/ae25ea","DOIUrl":"https://doi.org/10.3847/1538-4357/ae25ea","url":null,"abstract":"Type IIn supernovae (SNe IIn) are a subclass of core-collapse SNe in which strong interactions occur between the ejecta and dense circumstellar material, creating ideal conditions for the production of high-energy neutrinos. This makes them promising candidate sources of neutrinos. In this work, we conduct an association study between 163 SNe IIn observed by the Zwicky Transient Facility and 138 neutrino alert events detected by the IceCube Neutrino Observatory. After excluding alerts with poor localization, we find two SNe that are spatiotemporally coincident with neutrino events. IC 231027A and IC 250421A coincide with the positions of SN 2023syz and SN 2025cbj, respectively, within their localization uncertainties, and the neutrino arrival times are delayed by 38 days and 61 days relative to the discovery times of the corresponding SNe. Using Monte Carlo simulations, we estimate that the probability of two such events occurring by chance in our sample is p ∼ 0.67%, suggesting that they may originate from genuine physical associations, though the result is not yet statistically significant. Our model calculations, however, indicate that the likelihood of a neutrino originating from IC 231027A is low, implying that the association between IC 231027A and SN 2023syz is likely coincidental. Nevertheless, under optimistic parameters, the probability of detecting a neutrino from the whole SNe IIn sample could reach ≳6%, indicating that detecting neutrino emission from the SNe population may be possible. Our study provides a systematic analysis, combining statistical analysis and model calculations, to assess whether interacting supernovae can serve as potential sources of neutrino emission.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146000822","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 : 2026-01-20DOI: 10.3847/1538-4357/ae22d6
Yimin Wang, 宜敏 王, Jiajia Liu, 佳佳 刘, Jing Chen, 静 陈, Robertus Erdélyi, Norbert G. Gyenge, Ye Jiang and 也 姜
Accurate sunspot number estimation is essential for understanding the long-term evolution of solar activity and its impact on space weather. Sunspot numbers have been manually determined, leading to inconsistencies and observer-dependent biases. To address this, the World Data Center Sunspot Index and Long-term Solar Observations (WDC-SILSO) aggregates data from a global network of observatories to estimate the daily total sunspot number, enabling cross-validation and calibration across simultaneous observations. This study proposes a novel deep learning framework for automated total sunspot number calculation using solar full-disk continuum images from the Solar Dynamics Observatory. The method integrates U-Net for sunspot segmentation, K-means clustering for distinguishing umbrae from penumbrae, and You Only Look Once model for sunspot group detection. The selection of image-processing thresholds and neural network hyperparameters is optimized with respect to WDC-SILSO reference values during training. The results demonstrate a high correlation of 0.97 between the estimated and the WDC-SILSO daily total sunspot numbers. Furthermore, the framework offers a scalable approach suitable for future high-resolution solar observations.
准确的太阳黑子数估算对于了解太阳活动的长期演变及其对空间天气的影响至关重要。太阳黑子的数量一直是人工确定的，这导致了不一致和观察者依赖的偏差。为了解决这个问题，世界数据中心太阳黑子指数和长期太阳观测（WDC-SILSO）汇集了来自全球观测站网络的数据，以估计每日太阳黑子总数，从而实现跨同时观测的交叉验证和校准。本研究提出了一种新的深度学习框架，利用太阳动力学天文台的太阳全盘连续体图像自动计算太阳总黑子数。该方法将U-Net用于太阳黑子分割，K-means聚类用于区分本影和半影，You Only Look Once模型用于太阳黑子群检测。在训练过程中，针对WDC-SILSO参考值对图像处理阈值和神经网络超参数的选择进行优化。结果表明，估算值与WDC-SILSO日总黑子数的相关系数为0.97。此外，该框架提供了一种适用于未来高分辨率太阳观测的可扩展方法。
{"title":"A Deep Learning Approach for Automated Total Sunspot Number Estimation","authors":"Yimin Wang, 宜敏 王, Jiajia Liu, 佳佳 刘, Jing Chen, 静 陈, Robertus Erdélyi, Norbert G. Gyenge, Ye Jiang and 也 姜","doi":"10.3847/1538-4357/ae22d6","DOIUrl":"https://doi.org/10.3847/1538-4357/ae22d6","url":null,"abstract":"Accurate sunspot number estimation is essential for understanding the long-term evolution of solar activity and its impact on space weather. Sunspot numbers have been manually determined, leading to inconsistencies and observer-dependent biases. To address this, the World Data Center Sunspot Index and Long-term Solar Observations (WDC-SILSO) aggregates data from a global network of observatories to estimate the daily total sunspot number, enabling cross-validation and calibration across simultaneous observations. This study proposes a novel deep learning framework for automated total sunspot number calculation using solar full-disk continuum images from the Solar Dynamics Observatory. The method integrates U-Net for sunspot segmentation, K-means clustering for distinguishing umbrae from penumbrae, and You Only Look Once model for sunspot group detection. The selection of image-processing thresholds and neural network hyperparameters is optimized with respect to WDC-SILSO reference values during training. The results demonstrate a high correlation of 0.97 between the estimated and the WDC-SILSO daily total sunspot numbers. Furthermore, the framework offers a scalable approach suitable for future high-resolution solar observations.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146001633","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 : 2026-01-20DOI: 10.3847/1538-4357/ae225a
B. McGloughlin, J. Martins, B. Steltner, M. A. Papa, H.-B. Eggenstein, B. Machenschalk, R. Prix and M. Bensch
We present results from the most sensitive all-sky search to date for continuous gravitational waves with frequencies 30.0 Hz ≤ f ≤ 250.0 Hz and frequency derivatives Hz s−1. We deploy this search on the Einstein@Home volunteer-computing project and on three supercomputer clusters. At the end of a multistage approach there are four surviving candidates: three from “hardware injections,” i.e., signals “added” by moving the instruments’ mirrors, and one due to line disturbances in the data. The high sensitivity of our search enabled the first-ever detection of hardware injection 11. We set upper limits on the gravitational wave amplitude h0, and translate these to upper limits on the neutron star ellipticity and on the r-mode amplitude. The most stringent upper limits are at 173 Hz with h0 = 6.5 × 10−26, at the 90% confidence level, which improve by about 70% with respect to the LIGO-Virgo-KAGRA Collaboration’s most stringent O3 upper limits, and might well be competitive with results from O4 searches.
{"title":"Einstein@Home All-sky “Bucket” Search for Continuous Gravitational Waves in LIGO O3a Public Data","authors":"B. McGloughlin, J. Martins, B. Steltner, M. A. Papa, H.-B. Eggenstein, B. Machenschalk, R. Prix and M. Bensch","doi":"10.3847/1538-4357/ae225a","DOIUrl":"https://doi.org/10.3847/1538-4357/ae225a","url":null,"abstract":"We present results from the most sensitive all-sky search to date for continuous gravitational waves with frequencies 30.0 Hz ≤ f ≤ 250.0 Hz and frequency derivatives Hz s−1. We deploy this search on the Einstein@Home volunteer-computing project and on three supercomputer clusters. At the end of a multistage approach there are four surviving candidates: three from “hardware injections,” i.e., signals “added” by moving the instruments’ mirrors, and one due to line disturbances in the data. The high sensitivity of our search enabled the first-ever detection of hardware injection 11. We set upper limits on the gravitational wave amplitude h0, and translate these to upper limits on the neutron star ellipticity and on the r-mode amplitude. The most stringent upper limits are at 173 Hz with h0 = 6.5 × 10−26, at the 90% confidence level, which improve by about 70% with respect to the LIGO-Virgo-KAGRA Collaboration’s most stringent O3 upper limits, and might well be competitive with results from O4 searches.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146000819","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 : 2026-01-20DOI: 10.3847/1538-4357/ae2481
Darryl Z. Seligman, Dušan Marčeta and Eloy Peña-Asensio
In this paper we calculate the expected orbital elements, radiants, and velocities of Earth-impacting interstellar objects. We generate a synthetic population of ∼1010 interstellar objects with M-star kinematics in order to obtain ∼104 Earth impactors. The relative flux of impactors arriving from the direction of the solar apex and the Galactic plane is enhanced by a factor of ∼2 relative to the mean. The fastest impactors also arrive from these directions, although Earth impactors are generally slower than objects in the overall population. This is because the Earth-impacting subset contains a higher fraction of low-eccentricity hyperbolic objects, which are more strongly affected by gravitational focusing. Earth-impacting interstellar objects are more likely to have retrograde orbits close to the ecliptic plane. A selection effect makes the inclination distribution of Earth-impacting interstellar objects uniform (sinusoidal) at low (high) perihelion distances. In turn, low-perihelion impactors have a higher impact probability towards the ecliptic plane. The overall impactor population therefore exhibits an intermediate inclination distribution between uniform and sinusoidal. In turn, low-perihelion impactors have a higher impact probability towards the ecliptic plane. The highest-velocity impacts are most likely to occur in the spring when the Earth is moving towards the solar apex. However, impacts in general are more likely to occur during the winter when the Earth is located in the direction of the antapex. Interstellar objects are more likely to impact the Earth at low latitudes close to the equator, with a slight preference for the Northern Hemisphere due to the location of the apex. These distributions are independent of the assumed interstellar object number density, albedos, and size–frequency distribution and are publicly available.
{"title":"The Distribution of Earth-impacting Interstellar Objects","authors":"Darryl Z. Seligman, Dušan Marčeta and Eloy Peña-Asensio","doi":"10.3847/1538-4357/ae2481","DOIUrl":"https://doi.org/10.3847/1538-4357/ae2481","url":null,"abstract":"In this paper we calculate the expected orbital elements, radiants, and velocities of Earth-impacting interstellar objects. We generate a synthetic population of ∼1010 interstellar objects with M-star kinematics in order to obtain ∼104 Earth impactors. The relative flux of impactors arriving from the direction of the solar apex and the Galactic plane is enhanced by a factor of ∼2 relative to the mean. The fastest impactors also arrive from these directions, although Earth impactors are generally slower than objects in the overall population. This is because the Earth-impacting subset contains a higher fraction of low-eccentricity hyperbolic objects, which are more strongly affected by gravitational focusing. Earth-impacting interstellar objects are more likely to have retrograde orbits close to the ecliptic plane. A selection effect makes the inclination distribution of Earth-impacting interstellar objects uniform (sinusoidal) at low (high) perihelion distances. In turn, low-perihelion impactors have a higher impact probability towards the ecliptic plane. The overall impactor population therefore exhibits an intermediate inclination distribution between uniform and sinusoidal. In turn, low-perihelion impactors have a higher impact probability towards the ecliptic plane. The highest-velocity impacts are most likely to occur in the spring when the Earth is moving towards the solar apex. However, impacts in general are more likely to occur during the winter when the Earth is located in the direction of the antapex. Interstellar objects are more likely to impact the Earth at low latitudes close to the equator, with a slight preference for the Northern Hemisphere due to the location of the apex. These distributions are independent of the assumed interstellar object number density, albedos, and size–frequency distribution and are publicly available.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146000820","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 : 2026-01-20DOI: 10.3847/1538-4357/ae25fc
N. Parmiggiani, A. Bulgarelli, G. Panebianco, E. Burns, E. Neights, V. Fioretti, I. Martinez-Castellanos, L. Castaldini, A. Ciabattoni, A. Di Piano, R. Falco, S. Gallego, G. Mustafa, P. Patel, A. Rizzo, E. A. Wulf, D. H. Hartmann, C. A. Kierans, J. A. Tomsick and A. Zoglauer
The Compton Spectrometer and Imager (COSI) is a NASA satellite mission under development designed to survey the entire sky at 0.2–5 MeV with a wide-field gamma-ray telescope. Its main instrument is a germanium detector array surrounded on the sides and bottom by bismuth germanium oxide scintillator active shields (the “Anticoincidence Subsystem” (ACS)) to reduce and monitor background and for detecting transients. COSI will have an onboard trigger algorithm to detect gamma-ray bursts (GRBs) in the ACS and send data to the ground for further analysis. In this paper, we present three localization methods that we evaluated for the localization of short GRBs (sGRBs) using the ACS light curves. The first method is the χ2 fit already used by the Fermi Gamma-ray Burst Monitor, which calculates the best fit between look-up tables and the GRB data. The second method is a maximum likelihood estimation fit implemented in bc-tools for the BurstCube mission that performs a fit between the instrument response function and the GRB data. The last method is based on deep learning techniques and consists of a neural network developed for the COSI mission and trained to perform a regression of the sGRB position, taking as input the count rates of each ACS panel. The localization errors obtained by analyzing simulated sGRBs with the three methods are consistent. Despite the theoretical similarity between the approaches, their consistency in results is noteworthy, as they differ substantially in their implementations and optimization processes. The bc-tools obtain the best localization accuracy.
{"title":"COSI Short Gamma-Ray Burst Localization Using BGO Shield Data","authors":"N. Parmiggiani, A. Bulgarelli, G. Panebianco, E. Burns, E. Neights, V. Fioretti, I. Martinez-Castellanos, L. Castaldini, A. Ciabattoni, A. Di Piano, R. Falco, S. Gallego, G. Mustafa, P. Patel, A. Rizzo, E. A. Wulf, D. H. Hartmann, C. A. Kierans, J. A. Tomsick and A. Zoglauer","doi":"10.3847/1538-4357/ae25fc","DOIUrl":"https://doi.org/10.3847/1538-4357/ae25fc","url":null,"abstract":"The Compton Spectrometer and Imager (COSI) is a NASA satellite mission under development designed to survey the entire sky at 0.2–5 MeV with a wide-field gamma-ray telescope. Its main instrument is a germanium detector array surrounded on the sides and bottom by bismuth germanium oxide scintillator active shields (the “Anticoincidence Subsystem” (ACS)) to reduce and monitor background and for detecting transients. COSI will have an onboard trigger algorithm to detect gamma-ray bursts (GRBs) in the ACS and send data to the ground for further analysis. In this paper, we present three localization methods that we evaluated for the localization of short GRBs (sGRBs) using the ACS light curves. The first method is the χ2 fit already used by the Fermi Gamma-ray Burst Monitor, which calculates the best fit between look-up tables and the GRB data. The second method is a maximum likelihood estimation fit implemented in bc-tools for the BurstCube mission that performs a fit between the instrument response function and the GRB data. The last method is based on deep learning techniques and consists of a neural network developed for the COSI mission and trained to perform a regression of the sGRB position, taking as input the count rates of each ACS panel. The localization errors obtained by analyzing simulated sGRBs with the three methods are consistent. Despite the theoretical similarity between the approaches, their consistency in results is noteworthy, as they differ substantially in their implementations and optimization processes. The bc-tools obtain the best localization accuracy.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146000823","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 : 2026-01-20DOI: 10.3847/1538-4357/ae2798
Maria B. Stone, Roberto De Propris, Clare Wethers, Jari Kotilainen, Nischal Acharya, Benne Holwerda, Andrew M. Hopkins and Kevin Pimbblet
We investigated the star formation history and stellar populations of a sample of 205 Type I quasar host galaxies (0.1 < z < 0.35) and compared them with normal (nonactive) galaxies of the same mass and redshift within the volume of the Galaxy and Mass Assembly redshift survey. We find that quasar host galaxies tend to be star-forming galaxies (∼80%) lying on the star-forming main sequence; the fraction of quasar host galaxies that are quiescent (∼20%) is lower than the fraction of quiescent galaxies in the comparison sample of normal galaxies (54%). We find that the mean star formation rate (SFR) of quasar host galaxies has increased over the past 100 Myr by a factor of 2–3, but these galaxies were star-forming at all times previously. Our data are more consistent with quasar activity originating together with an increase in the SFR of otherwise normal galaxies, similar to episodic star formation in normal spirals. We argue that this indicates that secular processes and minor mergers may be the favored triggers of nuclear activity in the local Universe.
我们研究了205个I型类星体宿主星系（0.1 < z < 0.35）的恒星形成历史和恒星群，并将它们与星系和质量集合红移调查范围内相同质量和红移的正常（非活动）星系进行了比较。我们发现类星体宿主星系往往是恒星形成星系（约80%），位于恒星形成主序上；类星体宿主星系中静止星系的比例（~ 20%）低于正常星系对比样本中静止星系的比例（54%）。我们发现类星体宿主星系的平均恒星形成率（SFR）在过去100 Myr中增加了2-3倍，但这些星系之前一直在形成恒星。我们的数据更符合类星体活动与正常星系的SFR增加一起产生，类似于正常螺旋中的偶发性恒星形成。我们认为，这表明长期过程和较小的合并可能是局部宇宙中核活动的有利触发因素。
{"title":"Galaxy and Mass Assembly (GAMA). The Properties of Quasar Host Galaxies: Star Formation Histories and Stellar Populations","authors":"Maria B. Stone, Roberto De Propris, Clare Wethers, Jari Kotilainen, Nischal Acharya, Benne Holwerda, Andrew M. Hopkins and Kevin Pimbblet","doi":"10.3847/1538-4357/ae2798","DOIUrl":"https://doi.org/10.3847/1538-4357/ae2798","url":null,"abstract":"We investigated the star formation history and stellar populations of a sample of 205 Type I quasar host galaxies (0.1 < z < 0.35) and compared them with normal (nonactive) galaxies of the same mass and redshift within the volume of the Galaxy and Mass Assembly redshift survey. We find that quasar host galaxies tend to be star-forming galaxies (∼80%) lying on the star-forming main sequence; the fraction of quasar host galaxies that are quiescent (∼20%) is lower than the fraction of quiescent galaxies in the comparison sample of normal galaxies (54%). We find that the mean star formation rate (SFR) of quasar host galaxies has increased over the past 100 Myr by a factor of 2–3, but these galaxies were star-forming at all times previously. Our data are more consistent with quasar activity originating together with an increase in the SFR of otherwise normal galaxies, similar to episodic star formation in normal spirals. We argue that this indicates that secular processes and minor mergers may be the favored triggers of nuclear activity in the local Universe.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"183 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146000824","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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