Pub Date : 2026-03-18DOI: 10.3847/1538-4357/ae4a1d
Lei Huang, Yang Guo, Zhen Li, Jinhan Guo and Mingde Ding
Solar jets, collimated plasma ejections driven by magnetic reconnection, play a vital role in energy transport and coronal heating. While rotational motions in jets are often attributed to magnetic field untwisting, alternative explanatory mechanisms remain possible. This study investigates a rotating jet in an active region observed on 2023 August 1 using multiwavelength observations from the Atmospheric Imaging Assembly, Chinese Hα Solar Explorer, and Interface Region Imaging Spectrograph, combined with a self-consistent time-dependent magnetofrictional model and magnetohydrodynamic simulation. Spectral diagnostics reveal coexisting red and blueshifts along the edges and central axis of the jet, indicating helical plasma motion within a twisted magnetic structure. Numerical simulations demonstrate that the jet’s rotation arises from plasma propagating along helical open field lines, formed via reconnection between a pre-existing flux rope and overlying magnetic fields. Contrary to classical untwisting models, both linear and rotational velocities decrease with altitude during the jet propagation. These results highlight that the observed rotation results from plasma spiral motion along twisted fields rather than untwisting dynamics of the magnetic field itself, providing new insights into solar jet energetics and their connection to broader solar phenomena.
{"title":"Rotation of a Solar Jet Driven by Plasma Flow along Helical Magnetic Fields in an Active Region","authors":"Lei Huang, Yang Guo, Zhen Li, Jinhan Guo and Mingde Ding","doi":"10.3847/1538-4357/ae4a1d","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4a1d","url":null,"abstract":"Solar jets, collimated plasma ejections driven by magnetic reconnection, play a vital role in energy transport and coronal heating. While rotational motions in jets are often attributed to magnetic field untwisting, alternative explanatory mechanisms remain possible. This study investigates a rotating jet in an active region observed on 2023 August 1 using multiwavelength observations from the Atmospheric Imaging Assembly, Chinese Hα Solar Explorer, and Interface Region Imaging Spectrograph, combined with a self-consistent time-dependent magnetofrictional model and magnetohydrodynamic simulation. Spectral diagnostics reveal coexisting red and blueshifts along the edges and central axis of the jet, indicating helical plasma motion within a twisted magnetic structure. Numerical simulations demonstrate that the jet’s rotation arises from plasma propagating along helical open field lines, formed via reconnection between a pre-existing flux rope and overlying magnetic fields. Contrary to classical untwisting models, both linear and rotational velocities decrease with altitude during the jet propagation. These results highlight that the observed rotation results from plasma spiral motion along twisted fields rather than untwisting dynamics of the magnetic field itself, providing new insights into solar jet energetics and their connection to broader solar phenomena.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147471270","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}
We investigate the bar fraction in galaxy pairs from the Sloan Digital Sky Survey to assess how galaxy interactions affect bar structures. Compared to isolated galaxies, close pairs exhibit a significantly reduced bar fraction at projected separations within 25 kpc. This reduction is driven almost entirely by systems showing clear merger or disturbance signatures, indicating that tidal interactions suppress bars. The decline is dominated by a decrease in weak bars, while the fraction of strong bars remains largely unchanged. Bar suppression is primarily associated with major mergers and is strongest in massive host galaxies. A weaker but statistically significant suppression is detected in minor mergers only for massive galaxies with small bulges. In contrast, no significant dependence of bar suppression on the relative orientation between pair members is found. These findings provide observational evidence that tidal perturbations in major mergers play a key role in regulating bar evolution.
{"title":"Reduction of the Bar Fraction in Paired Galaxies in the SDSS","authors":"Linlin Li, 林林 李, Shuai Feng, 帅 冯, Shiyin Shen, 世银 沈, Qi’an Deng, 淇安 邓, Ying Zu, 颖 祖, Wenyuan Cui and 文元 崔","doi":"10.3847/1538-4357/ae4bdc","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4bdc","url":null,"abstract":"We investigate the bar fraction in galaxy pairs from the Sloan Digital Sky Survey to assess how galaxy interactions affect bar structures. Compared to isolated galaxies, close pairs exhibit a significantly reduced bar fraction at projected separations within 25 kpc. This reduction is driven almost entirely by systems showing clear merger or disturbance signatures, indicating that tidal interactions suppress bars. The decline is dominated by a decrease in weak bars, while the fraction of strong bars remains largely unchanged. Bar suppression is primarily associated with major mergers and is strongest in massive host galaxies. A weaker but statistically significant suppression is detected in minor mergers only for massive galaxies with small bulges. In contrast, no significant dependence of bar suppression on the relative orientation between pair members is found. These findings provide observational evidence that tidal perturbations in major mergers play a key role in regulating bar evolution.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"64 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147471271","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}
We investigate whether the long photometric cycles observed in double-periodic variables (DPVs) can arise from nodal precession of a tilted accretion disk driven by the tidal torque of the companion. Within a simple analytical framework, we derive testable relations linking the long-to-orbital period ratio to the binary mass ratio, the normalized disk size, and the disk tilt angle β, which itself can be inferred from the long-cycle amplitude, orbital inclination i, and disk luminosity fraction. The model naturally reproduces the two observed long-cycle light-curve morphologies—sinusoidal and double hump—distinguished by the geometric criterion i + β ≤ 90° versus i + β > 90°. Applying these relations to a sample of DPVs, we find that the inferred disk sizes are physically reasonable and consistent with independent light-curve modeling for a nonnegligible subset of systems. Our results show that tidal nodal precession represents a viable and potentially important contributor to the long-period variability of DPVs and provide a quantitative framework for future observational and theoretical studies.
{"title":"Long Photometric Cycles in Double-periodic Variables from Nodal Precession of a Tilted Accretion Disk","authors":"Cheng-Liang Jiao, 承亮 焦, Er-gang Zhao, Liying Zhu and Azizbek Matekov","doi":"10.3847/1538-4357/ae4b30","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4b30","url":null,"abstract":"We investigate whether the long photometric cycles observed in double-periodic variables (DPVs) can arise from nodal precession of a tilted accretion disk driven by the tidal torque of the companion. Within a simple analytical framework, we derive testable relations linking the long-to-orbital period ratio to the binary mass ratio, the normalized disk size, and the disk tilt angle β, which itself can be inferred from the long-cycle amplitude, orbital inclination i, and disk luminosity fraction. The model naturally reproduces the two observed long-cycle light-curve morphologies—sinusoidal and double hump—distinguished by the geometric criterion i + β ≤ 90° versus i + β > 90°. Applying these relations to a sample of DPVs, we find that the inferred disk sizes are physically reasonable and consistent with independent light-curve modeling for a nonnegligible subset of systems. Our results show that tidal nodal precession represents a viable and potentially important contributor to the long-period variability of DPVs and provide a quantitative framework for future observational and theoretical studies.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"128 11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147471273","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 : 2026-03-18DOI: 10.3847/1538-4357/ae40ab
Kate D. Alexander, Raffaella Margutti, Sebastian Gomez, Michael Stroh, Ryan Chornock, Tanmoy Laskar, Y. Cendes, Edo Berger, Tarraneh Eftekhari, Noah Franz, Aprajita Hajela, B. D. Metzger, Giacomo Terreran, Michael Bietenholz, Collin Christy, Fabio De Colle, S. Komossa, Matt Nicholl, Enrico Ramirez-Ruiz, Richard Saxton, Genevieve Schroeder, Peter K. G. Williams and William Wu
Recent observations presented in Y. Cendes et al. show that optically selected tidal disruption events (TDEs) commonly produce delayed radio emission that can peak years after disruption. Here, we explore the multiwavelength properties of a sample of radio-observed optically selected TDEs, to shed light on the physical process(es) responsible for the late-rising radio emission. We combine new late-time X-ray observations with archival optical, UV, X-ray, and radio data to conclude that a diversity of accretion-driven outflows may power the delayed radio emission in TDEs. Our analysis suggests that some late radio outflows may be launched by a delayed phase of super-Eddington accretion onto the central supermassive black hole (SMBH), while others may result from a state transition to a “low–hard” radiatively inefficient accretion flow or the deceleration of an off-axis relativistic jet. We find that TDEs with delayed radio emission are less likely to exhibit helium emission lines at early times (p = 0.002) and may have larger optical/UV photospheric radii (p = 0.026) than other TDEs, possibly also indicating that the onset of SMBH accretion is delayed in these systems. Our results have implications for our understanding of state changes in SMBH accretion flows, the circularization timescale for TDE debris, and the prevalence of off-axis jets in TDEs, and they motivate systematic long-term monitoring of these unique transients. The objects in our sample with the brightest radio emission are also detected in the Very Large Array Sky Survey, demonstrating that all-sky radio surveys can play an important role in discovering unexpected properties of the TDE population.
Y. Cendes等人最近发表的观测结果表明，光学选择的潮汐破坏事件（TDEs）通常会产生延迟的无线电发射，在破坏数年后达到峰值。在这里，我们探索了射电观测到的光学选择tde样品的多波长特性，以阐明导致晚升射电发射的物理过程。我们将新的晚期x射线观测与档案光学、紫外、x射线和射电数据结合起来，得出结论：吸积驱动的流出物的多样性可能是tde延迟射电发射的动力。我们的分析表明，一些晚期射电流出可能是由超级爱丁顿吸积的延迟阶段发射到中央超大质量黑洞（SMBH）上，而其他可能是由状态转变到“低硬”辐射低效吸积流或离轴相对论性射流的减速造成的。我们发现具有延迟射电发射的tde在早期不太可能出现氦发射线（p = 0.002），并且可能比其他tde具有更大的光学/紫外光球半径（p = 0.026），这也可能表明SMBH吸积的开始在这些系统中被延迟。我们的研究结果对我们理解SMBH吸积流的状态变化、TDE碎片的循环时间尺度以及TDE中离轴射流的流行具有重要意义，并且它们激发了对这些独特瞬态的系统长期监测。在我们的样本中，射电发射最亮的天体也在甚大阵巡天中被探测到，这表明全天射电巡天可以在发现TDE种群的意外特性方面发挥重要作用。
{"title":"The Multiwavelength Context of Delayed Radio Emission in Tidal Disruption Events: Evidence for Accretion-driven Outflows","authors":"Kate D. Alexander, Raffaella Margutti, Sebastian Gomez, Michael Stroh, Ryan Chornock, Tanmoy Laskar, Y. Cendes, Edo Berger, Tarraneh Eftekhari, Noah Franz, Aprajita Hajela, B. D. Metzger, Giacomo Terreran, Michael Bietenholz, Collin Christy, Fabio De Colle, S. Komossa, Matt Nicholl, Enrico Ramirez-Ruiz, Richard Saxton, Genevieve Schroeder, Peter K. G. Williams and William Wu","doi":"10.3847/1538-4357/ae40ab","DOIUrl":"https://doi.org/10.3847/1538-4357/ae40ab","url":null,"abstract":"Recent observations presented in Y. Cendes et al. show that optically selected tidal disruption events (TDEs) commonly produce delayed radio emission that can peak years after disruption. Here, we explore the multiwavelength properties of a sample of radio-observed optically selected TDEs, to shed light on the physical process(es) responsible for the late-rising radio emission. We combine new late-time X-ray observations with archival optical, UV, X-ray, and radio data to conclude that a diversity of accretion-driven outflows may power the delayed radio emission in TDEs. Our analysis suggests that some late radio outflows may be launched by a delayed phase of super-Eddington accretion onto the central supermassive black hole (SMBH), while others may result from a state transition to a “low–hard” radiatively inefficient accretion flow or the deceleration of an off-axis relativistic jet. We find that TDEs with delayed radio emission are less likely to exhibit helium emission lines at early times (p = 0.002) and may have larger optical/UV photospheric radii (p = 0.026) than other TDEs, possibly also indicating that the onset of SMBH accretion is delayed in these systems. Our results have implications for our understanding of state changes in SMBH accretion flows, the circularization timescale for TDE debris, and the prevalence of off-axis jets in TDEs, and they motivate systematic long-term monitoring of these unique transients. The objects in our sample with the brightest radio emission are also detected in the Very Large Array Sky Survey, demonstrating that all-sky radio surveys can play an important role in discovering unexpected properties of the TDE population.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147470893","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 : 2026-03-17DOI: 10.3847/1538-4357/ae47dd
Koshvendra Singh, Joe P. Ninan, Zhen Guo, Valentin D. Ivanov, David A. H. Buckley, Devendra K. Ojha, Andrew Monson, Tarak Chand, Saurabh Sharma, Ram Kesh Yadav, Devendra K. Sahu, Pramod Kumar, Vardan Elbakyan, Sergei Nayakshin, Vitor Fermiano, Min Fang, Jura Borissova, Wen Ping Chen, Franz-Josef Hambsch, Radostin Kurtev, Calum Morris, Javier Osses, Vania Rodríguez, Tanvi Sharma, Bandari Srikanth, Thanawuth Thanathibodee, Wei-Hao Wang and Yuting Zhou
Accretion-driven outbursts in young stellar objects remain poorly understood, largely limited by a statistically small sample of closely followed-up events. This underscores the importance of a thorough exploration of each outbursting object. We studied a peculiar outbursting system, Gaia24ccy, which exhibited two Δg ∼ 3.8 mag outbursts in 2019 and 2024. The system consists of two unresolved, nearly identical, and rapidly rotating young stars: Gaia24ccy A (1.1419 days) and Gaia24ccy B (1.7898 days). Periodogram analyses just before the onset of the outbursts suggest Gaia24ccy B to be the outbursting component. Unlike any previously known EXor sources, the two outburst profiles show very similar evolution: both rose at the same rate for the first 15 days, followed by multiple “subbursts” on timescales of 10−20 days. The 2019 outburst lasted 145–255 days, while the 2024 outburst persisted for 367 days. We infer the unstable region to lie at rtrigger ≃ 0.019–0.047 au (∼5–12.3R⋆). The accreted mass per event, Macc ∼ 10−5 M⊙, can be provided by a compact inner-disk reservoir. The photometric rise and decay timescales, together with the mid-infrared (MIR) color evolution, favor a thermal–viscous trigger in a hot inner disk, while the presence of rich emission-line spectra indicates concurrent magnetospheric compression—together forming a hybrid picture. Finally, we explain the reddening of the MIR color observed during the outburst as a consequence of the competing emission from the viscous disk and the photosphere.
{"title":"Gaia24ccy: An Outburst Followed the Footsteps of its Predecessor","authors":"Koshvendra Singh, Joe P. Ninan, Zhen Guo, Valentin D. Ivanov, David A. H. Buckley, Devendra K. Ojha, Andrew Monson, Tarak Chand, Saurabh Sharma, Ram Kesh Yadav, Devendra K. Sahu, Pramod Kumar, Vardan Elbakyan, Sergei Nayakshin, Vitor Fermiano, Min Fang, Jura Borissova, Wen Ping Chen, Franz-Josef Hambsch, Radostin Kurtev, Calum Morris, Javier Osses, Vania Rodríguez, Tanvi Sharma, Bandari Srikanth, Thanawuth Thanathibodee, Wei-Hao Wang and Yuting Zhou","doi":"10.3847/1538-4357/ae47dd","DOIUrl":"https://doi.org/10.3847/1538-4357/ae47dd","url":null,"abstract":"Accretion-driven outbursts in young stellar objects remain poorly understood, largely limited by a statistically small sample of closely followed-up events. This underscores the importance of a thorough exploration of each outbursting object. We studied a peculiar outbursting system, Gaia24ccy, which exhibited two Δg ∼ 3.8 mag outbursts in 2019 and 2024. The system consists of two unresolved, nearly identical, and rapidly rotating young stars: Gaia24ccy A (1.1419 days) and Gaia24ccy B (1.7898 days). Periodogram analyses just before the onset of the outbursts suggest Gaia24ccy B to be the outbursting component. Unlike any previously known EXor sources, the two outburst profiles show very similar evolution: both rose at the same rate for the first 15 days, followed by multiple “subbursts” on timescales of 10−20 days. The 2019 outburst lasted 145–255 days, while the 2024 outburst persisted for 367 days. We infer the unstable region to lie at rtrigger ≃ 0.019–0.047 au (∼5–12.3R⋆). The accreted mass per event, Macc ∼ 10−5 M⊙, can be provided by a compact inner-disk reservoir. The photometric rise and decay timescales, together with the mid-infrared (MIR) color evolution, favor a thermal–viscous trigger in a hot inner disk, while the presence of rich emission-line spectra indicates concurrent magnetospheric compression—together forming a hybrid picture. Finally, we explain the reddening of the MIR color observed during the outburst as a consequence of the competing emission from the viscous disk and the photosphere.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147465704","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 : 2026-03-17DOI: 10.3847/1538-4357/ae48e5
Sihui Zhong, Dmitrii Y. Kolotkov and Valery M. Nakariakov
Solar intensity power spectra are usually characterized by colored noise, with the spectral energy following a segmented power-law function of frequency, S(f) ∝ f−α, over different frequency ranges. Typically, the power-law index exceeds 1 in the low-frequency part (αlf) and is around 0 at high frequencies (αhf). This work investigates the spatial and temporal evolution of the power-law indices of coronal EUV intensity power spectra in flare-hosting active regions. The spatial distribution of the power-law index in the low-frequency domain (αlf) closely mirrors EUV intensity images, indicating that αlf can reveal the dynamics of coronal plasma structures. Temporally, αlf remains stable in quiescent active regions, but it exhibits significant variability before the flare onset. Motivated by this behavior, we analyzed 14 flare events, quantifying the temporal variation of the indices αlf and αhf as potential flare precursors. In all flare events considered, notable deviations of αlf beyond a defined threshold consistently occurred at the flare site within a few minutes before the flare. In some cases, the change in the value of αlf − αhf was detected within 30–90 minutes before the flare. This proof-of-concept study suggests that the temporal variation of the power-law indices in coronal EUV intensity power spectra could potentially serve as short-term precursors of solar flares, which needs to be validated on a larger flare sample.
{"title":"Power-law Indices of EUV Intensity Power Spectrum in Flaring Coronal Active Regions","authors":"Sihui Zhong, Dmitrii Y. Kolotkov and Valery M. Nakariakov","doi":"10.3847/1538-4357/ae48e5","DOIUrl":"https://doi.org/10.3847/1538-4357/ae48e5","url":null,"abstract":"Solar intensity power spectra are usually characterized by colored noise, with the spectral energy following a segmented power-law function of frequency, S(f) ∝ f−α, over different frequency ranges. Typically, the power-law index exceeds 1 in the low-frequency part (αlf) and is around 0 at high frequencies (αhf). This work investigates the spatial and temporal evolution of the power-law indices of coronal EUV intensity power spectra in flare-hosting active regions. The spatial distribution of the power-law index in the low-frequency domain (αlf) closely mirrors EUV intensity images, indicating that αlf can reveal the dynamics of coronal plasma structures. Temporally, αlf remains stable in quiescent active regions, but it exhibits significant variability before the flare onset. Motivated by this behavior, we analyzed 14 flare events, quantifying the temporal variation of the indices αlf and αhf as potential flare precursors. In all flare events considered, notable deviations of αlf beyond a defined threshold consistently occurred at the flare site within a few minutes before the flare. In some cases, the change in the value of αlf − αhf was detected within 30–90 minutes before the flare. This proof-of-concept study suggests that the temporal variation of the power-law indices in coronal EUV intensity power spectra could potentially serve as short-term precursors of solar flares, which needs to be validated on a larger flare sample.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147465706","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 : 2026-03-17DOI: 10.3847/1538-4357/ae4905
Xia Li, Long Wang, Chengyuan Li, Yang Chen, Hao Tian and Xin Zhang
Observations show that multiple stellar populations (MPs) are ubiquitous in globular clusters. The Hubble Space Telescope (HST) has been a pivotal tool for previous photometric studies of MPs. The Chinese Space Station Survey Telescope (CSST) is a 2 m telescope scheduled for launch. One of its imaging instruments, the Survey Camera (SC), combines ultraviolet sensitivity comparable to that of HST with a significantly larger field of view, making it well-suited for conducting large-scale photometric surveys of MPs within extensive stellar stream structures. In this work, we perform mock observations of the stellar stream Palomar 5 to assess the feasibility of detecting MPs with the CSST/SC. The results indicate that the CSST/SC cannot resolve MPs in stellar streams at distances comparable to Palomar 5 (≳20 kpc) with one or 10 150 s exposures. This fundamental limitation arises from the absence of the precise proper motions required to disentangle stream members. We estimate that successful resolution would require the target stream to be ≲8 kpc under a 150 s exposure. Furthermore, using theoretical color–magnitude diagrams, we find that the CSST/SC g band provides an optimal balance between contamination rate and completeness rate for member identification in the cluster’s core. However, this approach fails in the stream due to severe field star contamination. Therefore, future CSST observations of Palomar 5 and its tidal tails will employ multiple epochs across several bands to obtain the deep photometry and proper motion data for a definitive MP analysis.
{"title":"Mock Observations of Multiple Stellar Populations in Tidal Streams of Palomar 5 for the Chinese Space Station Survey Telescope","authors":"Xia Li, Long Wang, Chengyuan Li, Yang Chen, Hao Tian and Xin Zhang","doi":"10.3847/1538-4357/ae4905","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4905","url":null,"abstract":"Observations show that multiple stellar populations (MPs) are ubiquitous in globular clusters. The Hubble Space Telescope (HST) has been a pivotal tool for previous photometric studies of MPs. The Chinese Space Station Survey Telescope (CSST) is a 2 m telescope scheduled for launch. One of its imaging instruments, the Survey Camera (SC), combines ultraviolet sensitivity comparable to that of HST with a significantly larger field of view, making it well-suited for conducting large-scale photometric surveys of MPs within extensive stellar stream structures. In this work, we perform mock observations of the stellar stream Palomar 5 to assess the feasibility of detecting MPs with the CSST/SC. The results indicate that the CSST/SC cannot resolve MPs in stellar streams at distances comparable to Palomar 5 (≳20 kpc) with one or 10 150 s exposures. This fundamental limitation arises from the absence of the precise proper motions required to disentangle stream members. We estimate that successful resolution would require the target stream to be ≲8 kpc under a 150 s exposure. Furthermore, using theoretical color–magnitude diagrams, we find that the CSST/SC g band provides an optimal balance between contamination rate and completeness rate for member identification in the cluster’s core. However, this approach fails in the stream due to severe field star contamination. Therefore, future CSST observations of Palomar 5 and its tidal tails will employ multiple epochs across several bands to obtain the deep photometry and proper motion data for a definitive MP analysis.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147465707","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 : 2026-03-17DOI: 10.3847/1538-4357/ae4b31
Rita K. Y. Lau
This study proposes that energy from nuclear reactions can be a source for short gamma-ray bursts (SGRBs). I demonstrate that within the dynamical ejecta of binary mergers, nuclear reactions generate immense energy on the order of 1050 erg s−1 or even higher from beta decay and up to 1058 erg s−1 from neutron capture. The latter process produces highly variable energetic spikes, which provide a natural explanation for the rapid luminosity variability observed in the SGRB light curves. This finding challenges the traditional paradigm that SGRBs are solely magnetically powered and points to nuclear energy as an alternative contributor to SGRBs.
这项研究提出，核反应产生的能量可能是短伽马射线暴（sgrb）的来源。我证明了在双星合并的动态抛射中，核反应产生巨大的能量，从β衰变产生1050 erg s - 1或更高的能量，从中子捕获产生1058 erg s - 1。后一个过程产生高度可变的能量尖峰，这为在SGRB光曲线中观测到的快速光度变化提供了自然的解释。这一发现挑战了传统的范例，即sgrb完全是磁力驱动的，并指出核能是sgrb的另一种替代来源。
{"title":"Nuclear Reactions in the Early Stage of Binary Mergers and Their Connections to Short Gamma-Ray Bursts","authors":"Rita K. Y. Lau","doi":"10.3847/1538-4357/ae4b31","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4b31","url":null,"abstract":"This study proposes that energy from nuclear reactions can be a source for short gamma-ray bursts (SGRBs). I demonstrate that within the dynamical ejecta of binary mergers, nuclear reactions generate immense energy on the order of 1050 erg s−1 or even higher from beta decay and up to 1058 erg s−1 from neutron capture. The latter process produces highly variable energetic spikes, which provide a natural explanation for the rapid luminosity variability observed in the SGRB light curves. This finding challenges the traditional paradigm that SGRBs are solely magnetically powered and points to nuclear energy as an alternative contributor to SGRBs.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"59 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147465708","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 : 2026-03-17DOI: 10.3847/1538-4357/ae4351
Ashna Gulati, Tara Murphy, David L. Kaplan, Dougal Dobie, Charlotte Ward, Gemma Anderson, Manisha Caleb, Poonam Chandra, Jeff Cooke, Barnali Das, Adam Deller, Adelle Goodwin, Kelly Gourdji, Giancarlo Ghirlanda, Emil Lenc, Anais Möller, James K. Leung, Stella Koch Ocker, Joshua Pritchard, Claudio Ricci, Elaine M. Sadler, Om Sharan Salafia, Kavya Shaji, Roberto Soria, Mark Suhr, Artem Tuntsov and Ziteng Wang
We report the discovery of a slowly evolving, extragalactic radio transient, ASKAP J005512.2–255834 (hereafter ASKAP J0055–2558), identified using the Australian SKA Pathfinder in a search for orphan afterglows associated with archival gravitational-wave events. Although discovered in this context, there is no evidence that the transient is associated with any known gravitational-wave event. Nonetheless, this source exhibits a 20-fold increase in flux density over <250 days, and it remains in a declining yet detectable state more than 1000 days after the initial detection. Follow-up observations from 0.3 to 9 GHz reveal an evolving spectrum consistent with synchrotron emission. ASKAP J0055–2558 is spatially coincident with a low-mass, star-forming galaxy at redshift z = 0.116 (dL = 543 Mpc), placing its peak radio luminosity at νLν ∼ 1039 erg s−1. Analysis of its radio light curve, inferred blast-wave velocity, energetics, host-galaxy properties, and the absence of counterparts at other wavelengths suggests that ASKAP J0055–2558 is most consistent with either the late-time phase of an orphan long gamma-ray burst afterglow or a tidal disruption event involving an intermediate-mass black hole spatially offset from the galaxy nucleus. The radio discovery of either of these phenomena is extremely rare, with only a few or no confirmed examples to date.
{"title":"ASKAP J005512.2−255834: A Luminous, Long-lived Radio Transient at z = 0.1—an Orphan Afterglow or an Off-nuclear TDE from an IMBH?","authors":"Ashna Gulati, Tara Murphy, David L. Kaplan, Dougal Dobie, Charlotte Ward, Gemma Anderson, Manisha Caleb, Poonam Chandra, Jeff Cooke, Barnali Das, Adam Deller, Adelle Goodwin, Kelly Gourdji, Giancarlo Ghirlanda, Emil Lenc, Anais Möller, James K. Leung, Stella Koch Ocker, Joshua Pritchard, Claudio Ricci, Elaine M. Sadler, Om Sharan Salafia, Kavya Shaji, Roberto Soria, Mark Suhr, Artem Tuntsov and Ziteng Wang","doi":"10.3847/1538-4357/ae4351","DOIUrl":"https://doi.org/10.3847/1538-4357/ae4351","url":null,"abstract":"We report the discovery of a slowly evolving, extragalactic radio transient, ASKAP J005512.2–255834 (hereafter ASKAP J0055–2558), identified using the Australian SKA Pathfinder in a search for orphan afterglows associated with archival gravitational-wave events. Although discovered in this context, there is no evidence that the transient is associated with any known gravitational-wave event. Nonetheless, this source exhibits a 20-fold increase in flux density over <250 days, and it remains in a declining yet detectable state more than 1000 days after the initial detection. Follow-up observations from 0.3 to 9 GHz reveal an evolving spectrum consistent with synchrotron emission. ASKAP J0055–2558 is spatially coincident with a low-mass, star-forming galaxy at redshift z = 0.116 (dL = 543 Mpc), placing its peak radio luminosity at νLν ∼ 1039 erg s−1. Analysis of its radio light curve, inferred blast-wave velocity, energetics, host-galaxy properties, and the absence of counterparts at other wavelengths suggests that ASKAP J0055–2558 is most consistent with either the late-time phase of an orphan long gamma-ray burst afterglow or a tidal disruption event involving an intermediate-mass black hole spatially offset from the galaxy nucleus. The radio discovery of either of these phenomena is extremely rare, with only a few or no confirmed examples to date.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147471272","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 : 2026-03-17DOI: 10.3847/1538-4357/ae43df
R. Abbasi, M. Ackermann, J. Adams, S. K. Agarwalla, J. A. Aguilar, M. Ahlers, J.M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Argüelles, Y. Ashida, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, J. Baines-Holmes, A. Balagopal V., S. W. Barwick, S. Bash, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, B. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, I. Bodo, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, R. T. Burley, D. Butterfield, M. A. Campana, K. Carloni, J. Carpio, S. Chattopadhyay, N. Chau, Z. Chen, D. Chirkin, S. Choi, B. A. Clark, A. Coleman, P. Coleman, G. H. Collin, D. A. Coloma Borja, A. Connolly, J. M. Conrad, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. Díaz-Vélez, S. DiKerby, T. Ding, M. Dittmer, A. Do..
The IceCube Neutrino Observatory has observed extragalactic astrophysical neutrinos with an apparently isotropic distribution. Only a small fraction of the observed astrophysical neutrinos can be explained by known sources. Neutrino production is thought to occur in energetic environments that are ultimately powered by the gravitational collapse of dense regions of the large-scale mass distribution in the universe. Whatever their identity, neutrino sources likely trace this large-scale mass distribution. The clustering of neutrinos with a tracer of the large-scale structure may provide insight into the distribution of neutrino sources with respect to redshift and the identity of neutrino sources. We implement a two-point angular cross correlation of the Northern sky track events with an infrared galaxy catalog derived from the Wide-field Infrared Survey Explorer (WISE) and Two Micron All Sky Survey (2MASS) source catalogs, which trace the nearby large-scale structure. No statistically significant correlation is found between the neutrinos and this infrared galaxy catalog. We find that ≤54% of the diffuse muon neutrino flux can be attributed to sources correlated with the galaxy catalog with 90% confidence. Additionally, when assuming that the neutrino source comoving density evolves following a power law in redshift, dNs/dV ∝ (1 + z)k, we find that sources with negative evolution, in particular k < −1.75, are disfavored at the 90% confidence level.
{"title":"Constraints on the Correlation of IceCube Neutrinos with a Tracer of Nearby Large-scale Structure","authors":"R. Abbasi, M. Ackermann, J. Adams, S. K. Agarwalla, J. A. Aguilar, M. Ahlers, J.M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Argüelles, Y. Ashida, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, J. Baines-Holmes, A. Balagopal V., S. W. Barwick, S. Bash, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, B. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, I. Bodo, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, R. T. Burley, D. Butterfield, M. A. Campana, K. Carloni, J. Carpio, S. Chattopadhyay, N. Chau, Z. Chen, D. Chirkin, S. Choi, B. A. Clark, A. Coleman, P. Coleman, G. H. Collin, D. A. Coloma Borja, A. Connolly, J. M. Conrad, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. Díaz-Vélez, S. DiKerby, T. Ding, M. Dittmer, A. Do..","doi":"10.3847/1538-4357/ae43df","DOIUrl":"https://doi.org/10.3847/1538-4357/ae43df","url":null,"abstract":"The IceCube Neutrino Observatory has observed extragalactic astrophysical neutrinos with an apparently isotropic distribution. Only a small fraction of the observed astrophysical neutrinos can be explained by known sources. Neutrino production is thought to occur in energetic environments that are ultimately powered by the gravitational collapse of dense regions of the large-scale mass distribution in the universe. Whatever their identity, neutrino sources likely trace this large-scale mass distribution. The clustering of neutrinos with a tracer of the large-scale structure may provide insight into the distribution of neutrino sources with respect to redshift and the identity of neutrino sources. We implement a two-point angular cross correlation of the Northern sky track events with an infrared galaxy catalog derived from the Wide-field Infrared Survey Explorer (WISE) and Two Micron All Sky Survey (2MASS) source catalogs, which trace the nearby large-scale structure. No statistically significant correlation is found between the neutrinos and this infrared galaxy catalog. We find that ≤54% of the diffuse muon neutrino flux can be attributed to sources correlated with the galaxy catalog with 90% confidence. Additionally, when assuming that the neutrino source comoving density evolves following a power law in redshift, dNs/dV ∝ (1 + z)k, we find that sources with negative evolution, in particular k < −1.75, are disfavored at the 90% confidence level.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147465699","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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