Pub Date : 2025-12-22DOI: 10.3847/1538-4357/ae1a6a
Xiukun Li, Wei Liu, Guangcheng Xiao, Bo Gao, Zhiping Jin and Qingzhong Liu
RX J0440.9+4431 is a Be/X-ray binary. Since its discovery, the Hα equivalent width (EW) of this source has exhibited three peaks, which correspond to different X-ray activities: three type I X-ray outbursts, no outburst, and a combined type I + type II outburst. In this work, we present photometric and spectroscopic observations spanning 2008–2023 and 2011–2023, respectively, covering the three peaks of Hα EW. Combined with related multiwavelength public data, we investigate the long-term evolution of RX J0440.9+4431. We propose that the longer disk growth time prior to 2010 led to a higher-density disk and triggered three type I outbursts. In contrast, the more rapid disk growth preceding 2018 resulted in lower disk density, and material accreted during the neutron star’s periastron passage was insufficient to trigger outburst. Later, the disk began to dissipate but ended with a substantial size and residual material. This prior density accumulation, combined with renewed growth, yielded a much higher-density disk at maximum extent during the subsequent phase, ultimately triggering the unique type II outburst.
{"title":"Long-term Multiwavelength Observations of RX J0440.9+4431: Unraveling the Mysteries of the Missing X-Ray Outburst and the Unique Giant Outburst","authors":"Xiukun Li, Wei Liu, Guangcheng Xiao, Bo Gao, Zhiping Jin and Qingzhong Liu","doi":"10.3847/1538-4357/ae1a6a","DOIUrl":"https://doi.org/10.3847/1538-4357/ae1a6a","url":null,"abstract":"RX J0440.9+4431 is a Be/X-ray binary. Since its discovery, the Hα equivalent width (EW) of this source has exhibited three peaks, which correspond to different X-ray activities: three type I X-ray outbursts, no outburst, and a combined type I + type II outburst. In this work, we present photometric and spectroscopic observations spanning 2008–2023 and 2011–2023, respectively, covering the three peaks of Hα EW. Combined with related multiwavelength public data, we investigate the long-term evolution of RX J0440.9+4431. We propose that the longer disk growth time prior to 2010 led to a higher-density disk and triggered three type I outbursts. In contrast, the more rapid disk growth preceding 2018 resulted in lower disk density, and material accreted during the neutron star’s periastron passage was insufficient to trigger outburst. Later, the disk began to dissipate but ended with a substantial size and residual material. This prior density accumulation, combined with renewed growth, yielded a much higher-density disk at maximum extent during the subsequent phase, ultimately triggering the unique type II outburst.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145801393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-22DOI: 10.3847/1538-4357/ae232d
Man Ho Chan
It has been suggested that there are ∼105 black hole–neutron star (BH–NS) binaries in our Galaxy. However, despite the effort of intensive radio search for decades, none of these binaries has been found to date. These binaries are regarded as a holy grail of astronomy because they can greatly improve our understanding about relativistic systems of compact objects and fundamental physics. In this article, we propose the existence of exotic BH–NS binaries that can open a new way in searching the missing BH–NS binaries in our Galaxy. By considering the possible dark matter density spikes formed around the primordial black holes in the BH–NS binaries, we show that extremely high temperature (∼106 K) could be maintained on the surface of the neutron stars due to effective dark matter capture. This interesting feature can also help reveal the nature of dark matter and possibly further improve the upper limit of dark matter scattering cross section well below 10−47 cm2.
{"title":"The Exotic Black Hole–Neutron Star Binaries in Our Galaxy","authors":"Man Ho Chan","doi":"10.3847/1538-4357/ae232d","DOIUrl":"https://doi.org/10.3847/1538-4357/ae232d","url":null,"abstract":"It has been suggested that there are ∼105 black hole–neutron star (BH–NS) binaries in our Galaxy. However, despite the effort of intensive radio search for decades, none of these binaries has been found to date. These binaries are regarded as a holy grail of astronomy because they can greatly improve our understanding about relativistic systems of compact objects and fundamental physics. In this article, we propose the existence of exotic BH–NS binaries that can open a new way in searching the missing BH–NS binaries in our Galaxy. By considering the possible dark matter density spikes formed around the primordial black holes in the BH–NS binaries, we show that extremely high temperature (∼106 K) could be maintained on the surface of the neutron stars due to effective dark matter capture. This interesting feature can also help reveal the nature of dark matter and possibly further improve the upper limit of dark matter scattering cross section well below 10−47 cm2.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145801421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-22DOI: 10.3847/1538-4357/ae1ca9
Sojun Ono and Kazuyuki Sugimura
We present a neural-network emulator for the thermal and chemical evolution in Population III star formation. The emulator accurately reproduces the thermochemical evolution over a wide density range spanning 21 orders of magnitude (10−3–1018 cm−3), tracking six primordial species: H, H2, e−, H+, H−, and H . To handle the broad dynamic range, we partition the density range into five subregions and train separate deep operator networks (DeepONets) in each region. When applied to randomly sampled thermochemical states, the emulator achieves relative errors below 10% in over 90% of cases for both temperature and chemical abundances (except for the rare species H ). The emulator is roughly 10 times faster on a CPU and more than 1000 times faster for batched predictions on a GPU, compared with conventional numerical integration. Furthermore, to ensure robust predictions under many iterations, we introduce a novel timescale-based update method, where a short-time-step update of each variable is computed by rescaling the predicted change over a longer time step equal to its characteristic variation timescale. In one-zone collapse calculations, the results from the timescale-based method agree well with traditional numerical integration, even with many iterations at a time step as short as 10−4 of the free-fall time. This proof-of-concept study suggests the potential for neural network-based chemical emulators to accelerate hydrodynamic simulations of star formation.
{"title":"Neural-network Chemical Emulator for First-star Formation: Robust Iterative Predictions Over a Wide Density Range","authors":"Sojun Ono and Kazuyuki Sugimura","doi":"10.3847/1538-4357/ae1ca9","DOIUrl":"https://doi.org/10.3847/1538-4357/ae1ca9","url":null,"abstract":"We present a neural-network emulator for the thermal and chemical evolution in Population III star formation. The emulator accurately reproduces the thermochemical evolution over a wide density range spanning 21 orders of magnitude (10−3–1018 cm−3), tracking six primordial species: H, H2, e−, H+, H−, and H . To handle the broad dynamic range, we partition the density range into five subregions and train separate deep operator networks (DeepONets) in each region. When applied to randomly sampled thermochemical states, the emulator achieves relative errors below 10% in over 90% of cases for both temperature and chemical abundances (except for the rare species H ). The emulator is roughly 10 times faster on a CPU and more than 1000 times faster for batched predictions on a GPU, compared with conventional numerical integration. Furthermore, to ensure robust predictions under many iterations, we introduce a novel timescale-based update method, where a short-time-step update of each variable is computed by rescaling the predicted change over a longer time step equal to its characteristic variation timescale. In one-zone collapse calculations, the results from the timescale-based method agree well with traditional numerical integration, even with many iterations at a time step as short as 10−4 of the free-fall time. This proof-of-concept study suggests the potential for neural network-based chemical emulators to accelerate hydrodynamic simulations of star formation.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145801415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-22DOI: 10.3847/1538-4357/ae2751
Qi Xu, Lianghai Xie, Limin Wang, Fuhao Qiao, Lei Li, Yiteng Zhang, Wenya Li, Yongyong Feng, Jijie Ma, Jing Wang and Linggao Kong
The water escape from Mars to space could be in the form of hydrogen and oxygen ions as driven by solar wind–Mars interactions. Although oxygen ion escape has been extensively investigated, the H+ escape rate was measured only at solar minimum. To determine the impacts of solar activity on the ionospheric H+ escape rate, we report the observational results from the Tianwen-1 spacecraft at solar maximum. The cold dense ionospheric ion outflows through the magnetotail have an equal energy acceleration process, consistent with the characteristics of ambipolar electric field acceleration. The escape rate of planetary cold H+ through the magnetotail is estimated to be ∼2 × 1023 s−1, a value substantially lower than the neutral hydrogen escape rate, and the H/O ratio (∼0.3) of the tailward escaping ions (H+, O+ and O ) is below the stoichiometric ratio of water. These results indicate the ionospheric H+ outflow plays a minimal role for the water loss on Mars across solar cycles. To assess the contribution of H+ escape to total hydrogen loss, future analysis must target the pickup H+ escape rate within the magnetosheath.
{"title":"Martian Ionospheric Cold Hydrogen Ion Escape at Solar Maximum: First Observations","authors":"Qi Xu, Lianghai Xie, Limin Wang, Fuhao Qiao, Lei Li, Yiteng Zhang, Wenya Li, Yongyong Feng, Jijie Ma, Jing Wang and Linggao Kong","doi":"10.3847/1538-4357/ae2751","DOIUrl":"https://doi.org/10.3847/1538-4357/ae2751","url":null,"abstract":"The water escape from Mars to space could be in the form of hydrogen and oxygen ions as driven by solar wind–Mars interactions. Although oxygen ion escape has been extensively investigated, the H+ escape rate was measured only at solar minimum. To determine the impacts of solar activity on the ionospheric H+ escape rate, we report the observational results from the Tianwen-1 spacecraft at solar maximum. The cold dense ionospheric ion outflows through the magnetotail have an equal energy acceleration process, consistent with the characteristics of ambipolar electric field acceleration. The escape rate of planetary cold H+ through the magnetotail is estimated to be ∼2 × 1023 s−1, a value substantially lower than the neutral hydrogen escape rate, and the H/O ratio (∼0.3) of the tailward escaping ions (H+, O+ and O ) is below the stoichiometric ratio of water. These results indicate the ionospheric H+ outflow plays a minimal role for the water loss on Mars across solar cycles. To assess the contribution of H+ escape to total hydrogen loss, future analysis must target the pickup H+ escape rate within the magnetosheath.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"173 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145801423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-22DOI: 10.3847/1538-4357/ae1e78
Maria Acevedo, Nora F. Sherman, Dillon Brout, Bastien Carreres, Daniel Scolnic, Brodie Popovic, Patrick Armstrong, Dingyuan Cao, Rebecca C. Chen, Alex Drlica-Wagner, Peter S. Ferguson, Christopher Lidman, Bailey Martin, Erik R. Peterson and Adam G. Riess
Type Ia supernovae (SNe Ia) have been essential for probing the nature of dark energy; however, most SN analyses rely on the same low-redshift sample, which may lead to shared systematics. In a companion paper, we introduce the Dark Energy Bedrock All-Sky Supernova (DEBASS) program, which has already collected more than 500 low-redshift SNe Ia on the Dark Energy Camera, and present an initial release of 77 SNe Ia within the Dark Energy Survey (DES) footprint observed between 2021 and 2024. Here, we examine the systematics, including photometric calibration and selection effects. We find agreement at the 10 mmag level among the tertiary standard stars of DEBASS, DES, and Pan-STARRS1. Our simulations reproduce the observed distributions of DEBASS SN light-curve properties, and we measure a bias-corrected Hubble residual scatter of 0.08 mag, which, while small, is found in 10% of our simulations. We compare the DEBASS SN distances to the Foundation sample and find consistency with a median residual offset of 0.016 ± 0.019 mag. Selection effects have negligible impacts on distances, but a different photometric calibration solution shifts the median residual −0.015 ± 0.019 mag, highlighting calibration sensitivity. Using conservative simulations, we forecast that replacing historical low-redshift samples with the full DEBASS sample will improve the statistical uncertainties on dark energy parameters w0 and wa by 30% and 24%, respectively, enhance the dark energy Figure of Merit by up to 60%, and enable a measurement of fσ8 at the 25% level.
{"title":"The Dark Energy Bedrock All-sky Supernova Program: Cross Calibration, Simulations, and Cosmology Forecasts","authors":"Maria Acevedo, Nora F. Sherman, Dillon Brout, Bastien Carreres, Daniel Scolnic, Brodie Popovic, Patrick Armstrong, Dingyuan Cao, Rebecca C. Chen, Alex Drlica-Wagner, Peter S. Ferguson, Christopher Lidman, Bailey Martin, Erik R. Peterson and Adam G. Riess","doi":"10.3847/1538-4357/ae1e78","DOIUrl":"https://doi.org/10.3847/1538-4357/ae1e78","url":null,"abstract":"Type Ia supernovae (SNe Ia) have been essential for probing the nature of dark energy; however, most SN analyses rely on the same low-redshift sample, which may lead to shared systematics. In a companion paper, we introduce the Dark Energy Bedrock All-Sky Supernova (DEBASS) program, which has already collected more than 500 low-redshift SNe Ia on the Dark Energy Camera, and present an initial release of 77 SNe Ia within the Dark Energy Survey (DES) footprint observed between 2021 and 2024. Here, we examine the systematics, including photometric calibration and selection effects. We find agreement at the 10 mmag level among the tertiary standard stars of DEBASS, DES, and Pan-STARRS1. Our simulations reproduce the observed distributions of DEBASS SN light-curve properties, and we measure a bias-corrected Hubble residual scatter of 0.08 mag, which, while small, is found in 10% of our simulations. We compare the DEBASS SN distances to the Foundation sample and find consistency with a median residual offset of 0.016 ± 0.019 mag. Selection effects have negligible impacts on distances, but a different photometric calibration solution shifts the median residual −0.015 ± 0.019 mag, highlighting calibration sensitivity. Using conservative simulations, we forecast that replacing historical low-redshift samples with the full DEBASS sample will improve the statistical uncertainties on dark energy parameters w0 and wa by 30% and 24%, respectively, enhance the dark energy Figure of Merit by up to 60%, and enable a measurement of fσ8 at the 25% level.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145801416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-22DOI: 10.3847/1538-4357/ae1a79
Finnegan M. Keller, Fei Dai and Wenrui Xu
Type I disk migration can form a chain of planets engaged in first-order mean-motion resonances (MMRs) parked at the disk inner edge. However, while second- or even third-order resonances were deemed unlikely due to their weaker strength, they have been observed in some planetary systems, e.g., TOI-178 bc (5:3), TOI-1136 ef (7:5), and TRAPPIST-1 bcd (8:5–5:3). We performed >6000 Type I simulations of multiplanet systems that mimic the observed Kepler sample in terms of stellar mass, planet size, multiplicity, and intra-system uniformity over a parameter space encompassing transitional and truncated disks. We found that Type I migration coupled with a disk inner edge can indeed produce second- and third-order resonances (in a state of libration) in ∼10% and 2% of resonant-chain systems, respectively. Moreover, the relative occurrence of first- and second-order MMRs in our simulations is consistent with observations (e.g., 3:2 is more common than 2:1; while second-order 5:3 is more common than 7:5). The formation of higher-order MMRs favors slower disk migration and a smaller outer planet mass. Higher-order resonances do not have to form with the help of a Laplace-like three-body resonance, as was proposed for TRAPPIST-1. Instead, the formation of higher-order resonances is assisted by breaking a preexisting first-order resonance, which generates small but nonzero initial eccentricities (e ≈ 10−3 to 10−2). We predict that (1) librating higher-order resonances have higher equilibrium e (∼0.1), (2) are more likely found as an isolated pair in an otherwise first-order chain, and (3) more likely emerge in the inner pairs of a chain.
I型盘的迁移可以形成一串行星，这些行星在盘的内缘处进行一阶平均运动共振（MMRs）。然而，虽然二阶甚至三阶共振被认为不太可能，因为它们的强度较弱，但它们已经在一些行星系统中被观察到，例如TOI-178 bc (5:3), TOI-1136 ef（7:5）和TRAPPIST-1 bcd（8:5-5:3）。我们对多行星系统进行了bbb6000型I型模拟，模拟了观测到的开普勒样本在恒星质量、行星大小、多样性和系统内均匀性方面的参数空间，包括过渡盘和截断盘。我们发现，在约10%和2%的共振链系统中，与圆盘内缘耦合的I型迁移确实可以分别产生二阶和三阶共振（处于振动状态）。此外，在我们的模拟中，一阶和二阶mmr的相对发生率与观测结果一致（例如，3:2比2:1更常见；而二阶5:3比7:5更常见）。高阶mmr的形成有利于较慢的圆盘迁移和较小的外行星质量。像TRAPPIST-1所提出的那样，高阶共振不必借助类拉普拉斯三体共振来形成。相反，高阶共振的形成是通过打破先前存在的一阶共振来辅助的，这产生了小但非零的初始偏心率（e≈10−3至10−2）。我们预测：(1)振动高阶共振具有更高的平衡e(~ 0.1),(2)更有可能在其他一阶链中作为孤立对发现，(3)更有可能出现在链的内部对中。
{"title":"Higher-order Mean-motion Resonances Can Form in Type I Disk Migration","authors":"Finnegan M. Keller, Fei Dai and Wenrui Xu","doi":"10.3847/1538-4357/ae1a79","DOIUrl":"https://doi.org/10.3847/1538-4357/ae1a79","url":null,"abstract":"Type I disk migration can form a chain of planets engaged in first-order mean-motion resonances (MMRs) parked at the disk inner edge. However, while second- or even third-order resonances were deemed unlikely due to their weaker strength, they have been observed in some planetary systems, e.g., TOI-178 bc (5:3), TOI-1136 ef (7:5), and TRAPPIST-1 bcd (8:5–5:3). We performed >6000 Type I simulations of multiplanet systems that mimic the observed Kepler sample in terms of stellar mass, planet size, multiplicity, and intra-system uniformity over a parameter space encompassing transitional and truncated disks. We found that Type I migration coupled with a disk inner edge can indeed produce second- and third-order resonances (in a state of libration) in ∼10% and 2% of resonant-chain systems, respectively. Moreover, the relative occurrence of first- and second-order MMRs in our simulations is consistent with observations (e.g., 3:2 is more common than 2:1; while second-order 5:3 is more common than 7:5). The formation of higher-order MMRs favors slower disk migration and a smaller outer planet mass. Higher-order resonances do not have to form with the help of a Laplace-like three-body resonance, as was proposed for TRAPPIST-1. Instead, the formation of higher-order resonances is assisted by breaking a preexisting first-order resonance, which generates small but nonzero initial eccentricities (e ≈ 10−3 to 10−2). We predict that (1) librating higher-order resonances have higher equilibrium e (∼0.1), (2) are more likely found as an isolated pair in an otherwise first-order chain, and (3) more likely emerge in the inner pairs of a chain.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"184 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145801440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-22DOI: 10.3847/1538-4357/ae1f08
Amy Secunda, Rachel S. Somerville, Yan-Fei Jiang, 燕飞 姜, Jenny E. Greene, Lukas J. Furtak and Adi Zitrin
Little red dots (LRDs), high-redshift, compact, red objects with V-shaped spectra, are one of the most exciting and perplexing discoveries made by the James Webb Space Telescope (JWST). While the simplest explanation for LRDs is that they are high-redshift active galactic nuclei (AGN), due to their compactness and frequent association with broad-line emission, the lack of corresponding X-ray emission and observed variability casts doubt on this picture. Here, we simulate LRD light curves using both traditional models for sub-Eddington AGN variability derived empirically from lower-redshift AGN observations and moderately super-Eddington AGN disk models from radiation magnetohydrodynamic simulations to examine the reason for the lack of variability. We find that even though most LRDs have only been observed two to four times in a given wave band, we should still be detecting significantly more variability if traditional sub-Eddington AGN variability models can be applied to LRDs. Instead, our super-Eddington model light curves are consistent with the lack of observed LRD variability. In addition, the ongoing high-cadence nexus campaign will detect changes in magnitude Δm > 1 for traditional sub-Eddington models, but will only observe significant continuum variability for the lowest-mass LRDs for our super-Eddington AGN models. Even if LRDs lack continuum variability, we find that the ongoing spectroscopic JWST campaign twinkle should observe broad emission line variability as long as soft X-ray irradiation manages to reach the broad-line region from the inner disk. Our models show that super-Eddington accretion can easily explain the lack of continuum variability in LRDs.
{"title":"Do Little Red Dots Vary?","authors":"Amy Secunda, Rachel S. Somerville, Yan-Fei Jiang, 燕飞 姜, Jenny E. Greene, Lukas J. Furtak and Adi Zitrin","doi":"10.3847/1538-4357/ae1f08","DOIUrl":"https://doi.org/10.3847/1538-4357/ae1f08","url":null,"abstract":"Little red dots (LRDs), high-redshift, compact, red objects with V-shaped spectra, are one of the most exciting and perplexing discoveries made by the James Webb Space Telescope (JWST). While the simplest explanation for LRDs is that they are high-redshift active galactic nuclei (AGN), due to their compactness and frequent association with broad-line emission, the lack of corresponding X-ray emission and observed variability casts doubt on this picture. Here, we simulate LRD light curves using both traditional models for sub-Eddington AGN variability derived empirically from lower-redshift AGN observations and moderately super-Eddington AGN disk models from radiation magnetohydrodynamic simulations to examine the reason for the lack of variability. We find that even though most LRDs have only been observed two to four times in a given wave band, we should still be detecting significantly more variability if traditional sub-Eddington AGN variability models can be applied to LRDs. Instead, our super-Eddington model light curves are consistent with the lack of observed LRD variability. In addition, the ongoing high-cadence nexus campaign will detect changes in magnitude Δm > 1 for traditional sub-Eddington models, but will only observe significant continuum variability for the lowest-mass LRDs for our super-Eddington AGN models. Even if LRDs lack continuum variability, we find that the ongoing spectroscopic JWST campaign twinkle should observe broad emission line variability as long as soft X-ray irradiation manages to reach the broad-line region from the inner disk. Our models show that super-Eddington accretion can easily explain the lack of continuum variability in LRDs.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145801419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-22DOI: 10.3847/1538-4357/ae1a74
Rachel A. Osten, Adam F. Kowalski, Suzanne Hawley, Isaiah I. Tristan, Sarah J. Schmidt, Ben Tofflemire and Eric Hilton
We present the results of a coordinated campaign to observe radio and optical stellar flares from the nearby M dwarf flare star EV Lac. From a total of 27 hr of radio and 29 hr of optical observations, we examine the correspondence of the action of accelerated electrons of different energies in two distinct regions of the stellar atmosphere. We find that out of nine optical flares with suitable radio coverage, only four have plausible evidence for a radio response. Optical photometric properties cannot predict which flares will have a radio response. From flares with time-resolved optical spectroscopy available, optical-only flares have similar implied electron distributions, while those with radio responses better correlate with higher low-energy cutoffs. The optical flares with a radio response all exhibit a delay between the optical and radio peaks of ≈1 and 7 minutes, with the optical flare peaking earlier in all cases. This likely indicates that multiple loops are involved in the event, and/or the different impacts on electrons trapped in a magnetic loop (producing radio emission), versus those directly precipitating from the loop (producing the optical flare). We also remark on the radio spectral index behavior at early times for the largest radio flare observed in this study, which we interpret as evidence for increased opacity from a chromospheric evaporation front.
{"title":"Radio and Optical Flares on the dMe Flare Star EV Lac","authors":"Rachel A. Osten, Adam F. Kowalski, Suzanne Hawley, Isaiah I. Tristan, Sarah J. Schmidt, Ben Tofflemire and Eric Hilton","doi":"10.3847/1538-4357/ae1a74","DOIUrl":"https://doi.org/10.3847/1538-4357/ae1a74","url":null,"abstract":"We present the results of a coordinated campaign to observe radio and optical stellar flares from the nearby M dwarf flare star EV Lac. From a total of 27 hr of radio and 29 hr of optical observations, we examine the correspondence of the action of accelerated electrons of different energies in two distinct regions of the stellar atmosphere. We find that out of nine optical flares with suitable radio coverage, only four have plausible evidence for a radio response. Optical photometric properties cannot predict which flares will have a radio response. From flares with time-resolved optical spectroscopy available, optical-only flares have similar implied electron distributions, while those with radio responses better correlate with higher low-energy cutoffs. The optical flares with a radio response all exhibit a delay between the optical and radio peaks of ≈1 and 7 minutes, with the optical flare peaking earlier in all cases. This likely indicates that multiple loops are involved in the event, and/or the different impacts on electrons trapped in a magnetic loop (producing radio emission), versus those directly precipitating from the loop (producing the optical flare). We also remark on the radio spectral index behavior at early times for the largest radio flare observed in this study, which we interpret as evidence for increased opacity from a chromospheric evaporation front.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145801413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-22DOI: 10.3847/1538-4357/ae1970
E. Cappellazzo, J. R. Dawson, Mark Wardle, Trey V. Wenger, Anita Hafner, Dana S. Balser, L. D. Anderson, Elizabeth K. Mahony, M. R. Rugel and John M. Dickey
Observational studies of H ii region–molecular cloud interactions constrain models of feedback and quantify its impact on the surrounding environment. A recent hypothesis proposes that a characteristic spectral signature in ground state hyperfine lines of hydroxyl (OH)—the OH flip—may trace gas that is dynamically interacting with an expanding H ii region, offering a new means of probing such interactions. We explore this hypothesis using dedicated Jansky Very Large Array observations of three Galactic H ii regions, G049.205−0.343, G034.256+0.145, and G024.471+0.492, in 1–2 GHz continuum emission, all four 18 cm ground-state OH lines, and multiple hydrogen radio recombination lines. A Gaussian decomposition of the molecular gas data reveals complex OH emission and absorption across our targets. We detect the OH flip toward two of our sources, G049.205−0.343 and G034.256+0.145, finding agreement between key predictions of the flip hypothesis and the observed multiwavelength spectra, kinematics, and morphology. Specifically, we demonstrate a strong spatial and kinematic association between the OH flip and the ionized gas of the H ii regions—the first time this has been demonstrated for resolved sources—and evidence from 13CO(1–0) data that the expected OH component originates from the nondisturbed gas of the parent cloud. While we detect no flip in G024.471+0.492, we do find evidence of interacting molecular gas traced by OH, providing further support for OH’s ability to trace H ii region–molecular cloud interactions.
{"title":"Tracing Gas Kinematics and Interactions between H II Regions and Molecular Clouds Using VLA Observations of Recombination Lines and Hydroxyl","authors":"E. Cappellazzo, J. R. Dawson, Mark Wardle, Trey V. Wenger, Anita Hafner, Dana S. Balser, L. D. Anderson, Elizabeth K. Mahony, M. R. Rugel and John M. Dickey","doi":"10.3847/1538-4357/ae1970","DOIUrl":"https://doi.org/10.3847/1538-4357/ae1970","url":null,"abstract":"Observational studies of H ii region–molecular cloud interactions constrain models of feedback and quantify its impact on the surrounding environment. A recent hypothesis proposes that a characteristic spectral signature in ground state hyperfine lines of hydroxyl (OH)—the OH flip—may trace gas that is dynamically interacting with an expanding H ii region, offering a new means of probing such interactions. We explore this hypothesis using dedicated Jansky Very Large Array observations of three Galactic H ii regions, G049.205−0.343, G034.256+0.145, and G024.471+0.492, in 1–2 GHz continuum emission, all four 18 cm ground-state OH lines, and multiple hydrogen radio recombination lines. A Gaussian decomposition of the molecular gas data reveals complex OH emission and absorption across our targets. We detect the OH flip toward two of our sources, G049.205−0.343 and G034.256+0.145, finding agreement between key predictions of the flip hypothesis and the observed multiwavelength spectra, kinematics, and morphology. Specifically, we demonstrate a strong spatial and kinematic association between the OH flip and the ionized gas of the H ii regions—the first time this has been demonstrated for resolved sources—and evidence from 13CO(1–0) data that the expected OH component originates from the nondisturbed gas of the parent cloud. While we detect no flip in G024.471+0.492, we do find evidence of interacting molecular gas traced by OH, providing further support for OH’s ability to trace H ii region–molecular cloud interactions.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145801494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-22DOI: 10.3847/1538-4357/ae1b97
G. D. Berland, M. E. Hill, A. Kouloumvakos, D. G. Mitchell, R. L. McNutt, E. C. Roelof, C. M. S. Cohen, M. E. Wiedenbeck, D. J. McComas, E. R. Christian, N. A. Schwadron, L. Y. Khoo, M. E. Cuesta, G. D. Muro, Z. G. Xu, S. Pak, H. A. Farooki, M. L. Stevens and S. D. Bale
The Parker Solar Probe Integrated Science Investigation of the Sun (IS⊙IS) instrument suite measured a variety of suprathermal and energetic particle events during orbits 18 and 19. We provide an overview of key features of the observations to provide guidance critical to making progress on complicated, integrated data sets like those provided by IS⊙IS. In this work, we analyze and describe observations of particle acceleration signatures associated with coronal mass ejection (CME)–driven shocks and solar flares from 2023 November to 2024 March as measured by the IS⊙IS/Energetic Particle Instrument-Low Energy and Energetic Particle Instrument-High Energy particle detectors. We present energy spectra for protons through Fe ions from ∼10 keV nuc−1 to >10 MeV nuc−1, abundance ratios, and time series analyses for seven solar energetic particle (SEP) events with respect to the magnetic field and plasma context provided by the FIELDS and Solar Wind Electrons Alphas and Protons instruments, respectively. For SEP events in orbits 18 and 19, we find that acceleration driven by multiple CMEs in succession have larger variability in 4He/H and Fe/O ratios than singular CMEs, that flare-associated SEP events preferentially accelerate higher mass-to-charge ratio particles, and that shock upstream transients may be present in CME-driven interplanetary shocks.
{"title":"Parker Solar Probe Observations of Suprathermal and Energetic Particles during Orbits 18 and 19","authors":"G. D. Berland, M. E. Hill, A. Kouloumvakos, D. G. Mitchell, R. L. McNutt, E. C. Roelof, C. M. S. Cohen, M. E. Wiedenbeck, D. J. McComas, E. R. Christian, N. A. Schwadron, L. Y. Khoo, M. E. Cuesta, G. D. Muro, Z. G. Xu, S. Pak, H. A. Farooki, M. L. Stevens and S. D. Bale","doi":"10.3847/1538-4357/ae1b97","DOIUrl":"https://doi.org/10.3847/1538-4357/ae1b97","url":null,"abstract":"The Parker Solar Probe Integrated Science Investigation of the Sun (IS⊙IS) instrument suite measured a variety of suprathermal and energetic particle events during orbits 18 and 19. We provide an overview of key features of the observations to provide guidance critical to making progress on complicated, integrated data sets like those provided by IS⊙IS. In this work, we analyze and describe observations of particle acceleration signatures associated with coronal mass ejection (CME)–driven shocks and solar flares from 2023 November to 2024 March as measured by the IS⊙IS/Energetic Particle Instrument-Low Energy and Energetic Particle Instrument-High Energy particle detectors. We present energy spectra for protons through Fe ions from ∼10 keV nuc−1 to >10 MeV nuc−1, abundance ratios, and time series analyses for seven solar energetic particle (SEP) events with respect to the magnetic field and plasma context provided by the FIELDS and Solar Wind Electrons Alphas and Protons instruments, respectively. For SEP events in orbits 18 and 19, we find that acceleration driven by multiple CMEs in succession have larger variability in 4He/H and Fe/O ratios than singular CMEs, that flare-associated SEP events preferentially accelerate higher mass-to-charge ratio particles, and that shock upstream transients may be present in CME-driven interplanetary shocks.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145801412","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：