Pub Date : 2025-01-20DOI: 10.3847/1538-4357/ada250
Nahuel Andrés, Norberto Romanelli, Christian Mazelle, Li-Jen Chen, Jacob R. Gruesbeck and Jared R. Espley
Using Mars Atmosphere and Volatile EvolutioN Magnetometer observations, we report the first statistical study of ultralow frequency (ULF) waves at the Martian foreshock. The analyzed foreshock ULF wave events are observed in the 0.008–0.086 Hz frequency range, with nearly circular and elliptical left-handed polarization in the spacecraft reference frame. These waves are propagated quasi-parallel to the ambient magnetic field, with a moderate wave amplitude. All these properties are consistent with fast magnetosonic waves, most likely generated through the ion–ion right-hand resonant instability. In addition, our results suggest that the associated resonant backstreaming protons’ velocities parallel to the mean magnetic field in the solar wind reference frame are 1.33 ± 0.40 times the solar wind velocity. The similarity between our results and previous reports at other foreshocks may indicate the presence of a common acceleration process acting in planetary bow shocks and that is responsible for this particular backstreaming population.
{"title":"Foreshock Ultralow Frequency Waves at Mars: Consequence on the Particle Acceleration Mechanisms at the Martian Bow Shock","authors":"Nahuel Andrés, Norberto Romanelli, Christian Mazelle, Li-Jen Chen, Jacob R. Gruesbeck and Jared R. Espley","doi":"10.3847/1538-4357/ada250","DOIUrl":"https://doi.org/10.3847/1538-4357/ada250","url":null,"abstract":"Using Mars Atmosphere and Volatile EvolutioN Magnetometer observations, we report the first statistical study of ultralow frequency (ULF) waves at the Martian foreshock. The analyzed foreshock ULF wave events are observed in the 0.008–0.086 Hz frequency range, with nearly circular and elliptical left-handed polarization in the spacecraft reference frame. These waves are propagated quasi-parallel to the ambient magnetic field, with a moderate wave amplitude. All these properties are consistent with fast magnetosonic waves, most likely generated through the ion–ion right-hand resonant instability. In addition, our results suggest that the associated resonant backstreaming protons’ velocities parallel to the mean magnetic field in the solar wind reference frame are 1.33 ± 0.40 times the solar wind velocity. The similarity between our results and previous reports at other foreshocks may indicate the presence of a common acceleration process acting in planetary bow shocks and that is responsible for this particular backstreaming population.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142989747","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 : 2025-01-20DOI: 10.3847/1538-4357/ad9b0d
Wenhe Lyu, Hong-Xin Zhang, Sanjaya Paudel, Tie Li, Yimeng Tang, Guangwen Chen, Xu Kong and Eric W. Peng
Nuclear star clusters (NSCs) are commonly found in the centers of galaxies, but their dominant formation mechanisms remain elusive. We perform a consistent analysis of stellar populations of 97 nearby NSCs, based on spectroscopic data from the Very Large Telescope. The sample covers a galaxy stellar mass range of 107–1011 M⊙ and is more than 3 times larger than any previous study. We identify three galaxy stellar mass regimes with distinct NSC properties. In the low-mass regime of ≲ 8.5 (Mhost is in units of M⊙), nearly all NSCs have metallicities lower than their circum-NSC host but similar to those of typical red globular clusters (GCs), supporting the GC inspiral–merger scenario of NSC formation. In the high-mass regime of ≳ 9.5, nearly all NSCs have higher metallicities than their circum-NSC host and red GCs, suggesting significant contributions from in situ star formation. In the intermediate-mass regime, a comparable fraction of NSCs have higher or lower metallicities than their circum-NSC host and red GCs, with no clear dependence on NSC mass, suggesting intermittent in situ star formation. The majority of NSCs with higher metallicities than their host exhibit a negative age–metallicity correlation, providing clear evidence of long-term chemical enrichment. The average metallicity difference between NSC and host peaks broadly around and declines toward both higher and lower galaxy masses. We find that the efficiency of dynamical-friction-driven inspiral of GCs observed in present-day galaxies can explain the NSC mass at but falls short of observed ones at higher galaxy mass, reinforcing our conclusions based on stellar population analysis.
{"title":"Dependence of Metal Enrichment of Nuclear Star Clusters on Galaxy Stellar Mass","authors":"Wenhe Lyu, Hong-Xin Zhang, Sanjaya Paudel, Tie Li, Yimeng Tang, Guangwen Chen, Xu Kong and Eric W. Peng","doi":"10.3847/1538-4357/ad9b0d","DOIUrl":"https://doi.org/10.3847/1538-4357/ad9b0d","url":null,"abstract":"Nuclear star clusters (NSCs) are commonly found in the centers of galaxies, but their dominant formation mechanisms remain elusive. We perform a consistent analysis of stellar populations of 97 nearby NSCs, based on spectroscopic data from the Very Large Telescope. The sample covers a galaxy stellar mass range of 107–1011 M⊙ and is more than 3 times larger than any previous study. We identify three galaxy stellar mass regimes with distinct NSC properties. In the low-mass regime of ≲ 8.5 (Mhost is in units of M⊙), nearly all NSCs have metallicities lower than their circum-NSC host but similar to those of typical red globular clusters (GCs), supporting the GC inspiral–merger scenario of NSC formation. In the high-mass regime of ≳ 9.5, nearly all NSCs have higher metallicities than their circum-NSC host and red GCs, suggesting significant contributions from in situ star formation. In the intermediate-mass regime, a comparable fraction of NSCs have higher or lower metallicities than their circum-NSC host and red GCs, with no clear dependence on NSC mass, suggesting intermittent in situ star formation. The majority of NSCs with higher metallicities than their host exhibit a negative age–metallicity correlation, providing clear evidence of long-term chemical enrichment. The average metallicity difference between NSC and host peaks broadly around and declines toward both higher and lower galaxy masses. We find that the efficiency of dynamical-friction-driven inspiral of GCs observed in present-day galaxies can explain the NSC mass at but falls short of observed ones at higher galaxy mass, reinforcing our conclusions based on stellar population analysis.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990116","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 : 2025-01-20DOI: 10.3847/1538-4357/ad9b96
Priyesh Kumar Tripathi, Indranil Chattopadhyay and Raj Kishor Joshi
We investigate accretion onto an isolated black hole from uniform winds. If the winds are directed toward the black hole, then the accretion process can be well described by the classical Bondi–Hoyle–Lyttleton or BHL accretion. If the wind is not directed toward the black hole and flows past it, then a smaller fraction of the flow can be attracted by the black hole, and this type of accretion cannot be described by the classical BHL, and we coin the second kind as the lateral BHL. We show that the classical BHL cannot form an accretion disk, while lateral BHL can form transient accretion disks. To describe the thermodynamics of the flow, we have used a variable adiabatic index equation of state which depends on the temperature of the flow as well as the composition of the gas. We show that the electron-proton gas forms an accretion disk, which disappears and forms a shock cone, only to form the disk again at a later time, while for flows with fewer protons, the accretion disk, once lost, does not reappear again. Only when the flow is pair-dominated does it form a persistent accretion disk. We also show that a shock cone is less luminous than the accretion disk.
{"title":"On Disk Formation around Isolated Black Holes via Stream Accretion","authors":"Priyesh Kumar Tripathi, Indranil Chattopadhyay and Raj Kishor Joshi","doi":"10.3847/1538-4357/ad9b96","DOIUrl":"https://doi.org/10.3847/1538-4357/ad9b96","url":null,"abstract":"We investigate accretion onto an isolated black hole from uniform winds. If the winds are directed toward the black hole, then the accretion process can be well described by the classical Bondi–Hoyle–Lyttleton or BHL accretion. If the wind is not directed toward the black hole and flows past it, then a smaller fraction of the flow can be attracted by the black hole, and this type of accretion cannot be described by the classical BHL, and we coin the second kind as the lateral BHL. We show that the classical BHL cannot form an accretion disk, while lateral BHL can form transient accretion disks. To describe the thermodynamics of the flow, we have used a variable adiabatic index equation of state which depends on the temperature of the flow as well as the composition of the gas. We show that the electron-proton gas forms an accretion disk, which disappears and forms a shock cone, only to form the disk again at a later time, while for flows with fewer protons, the accretion disk, once lost, does not reappear again. Only when the flow is pair-dominated does it form a persistent accretion disk. We also show that a shock cone is less luminous than the accretion disk.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990207","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 : 2025-01-20DOI: 10.3847/1538-4357/ad9d3b
Ryosuke Kobashi, Shiu-Hang Lee, Takaaki Tanaka and Keiichi Maeda
While the environment around Tycho's supernova remnant has long been believed to be close to homogeneous, the latest analysis of Chandra data has identified a substantial deceleration of the forward shock, which poses a major challenge to this picture. R. Kobashi et al. showed that the existence of dense molecular cloud (MC) surrounding a rarefied wind-like circumstellar matter (CSM) can explain this observational finding in terms of the shock-expansion dynamics, supporting the so-called single-degenerate scenario for the progenitor system. We here extend this work to study the nonthermal emission processes and investigate whether such an environment is consistent with the observed multiwavelength spectrum. While the simulated broadband spectrum based on the wind–MC environment is largely consistent with observations, we find that such an environment predicts a harder gamma-ray spectrum than observed due to the relatively low CSM density in the cavity interior of the MC. This difference can be at least partially attributed to the present 1D setup of the model, which does not account for the clumpy and multidimensional structure of the CSM. Our model provides predictions for the long-term evolution of the broadband spectrum, which can be used to further probe Tycho's surrounding environment in the future, a key to resolving the long-standing issue of Type Ia supernova progenitor channels.
{"title":"Exploring the Circumstellar Environment of Tycho’s Supernova Remnant. II. Impact on the Broadband Nonthermal Emission","authors":"Ryosuke Kobashi, Shiu-Hang Lee, Takaaki Tanaka and Keiichi Maeda","doi":"10.3847/1538-4357/ad9d3b","DOIUrl":"https://doi.org/10.3847/1538-4357/ad9d3b","url":null,"abstract":"While the environment around Tycho's supernova remnant has long been believed to be close to homogeneous, the latest analysis of Chandra data has identified a substantial deceleration of the forward shock, which poses a major challenge to this picture. R. Kobashi et al. showed that the existence of dense molecular cloud (MC) surrounding a rarefied wind-like circumstellar matter (CSM) can explain this observational finding in terms of the shock-expansion dynamics, supporting the so-called single-degenerate scenario for the progenitor system. We here extend this work to study the nonthermal emission processes and investigate whether such an environment is consistent with the observed multiwavelength spectrum. While the simulated broadband spectrum based on the wind–MC environment is largely consistent with observations, we find that such an environment predicts a harder gamma-ray spectrum than observed due to the relatively low CSM density in the cavity interior of the MC. This difference can be at least partially attributed to the present 1D setup of the model, which does not account for the clumpy and multidimensional structure of the CSM. Our model provides predictions for the long-term evolution of the broadband spectrum, which can be used to further probe Tycho's surrounding environment in the future, a key to resolving the long-standing issue of Type Ia supernova progenitor channels.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"122 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990200","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 : 2025-01-20DOI: 10.3847/1538-4357/ad9d10
Yu-Yang Songsheng, Jian-Min Wang, Yuan Cao, XueFei Chen, JianPing Xiong, Zhi-Xiang Zhang and Rong-Gen Cai
The growing “Hubble tension” has prompted the need for precise measurements of cosmological distances. This paper demonstrates a purely geometric approach for determining the distances to extragalactic binaries through a joint analysis of spectroastrometry (SA), radial velocity (RV), and light-curve (LC) observations. A parameterized model for the binary system is outlined, and simulated SA, RV, and LC data are computed to infer the probability distribution of model parameters based on the mock data. The impacts of data quality and binary parameters on the distance uncertainties are comprehensively analyzed, showcasing the method’s potential for high-precision distance measurements. For a typical eclipsing binary in the Large Magellanic Cloud, the distance uncertainty is approximately 6% under reasonable observational conditions. Within a specific range of data quality and input parameters, the distance measurement precision of individual binary star systems is generally better than 10%. As a geometric method based on the simplest dynamics, it is independent of empirical calibration, and the systematics caused by model selections can be tested using nearby binaries with known distances. By measuring multiple binary star systems or monitoring one binary system repeatedly, geometric distance measurements of nearby galaxies can be achieved, providing valuable insights into the Hubble tension and advancing our understanding of the Universe’s structure and evolution.
{"title":"Geometrical Distances of Extragalactic Binaries through Spectroastrometry","authors":"Yu-Yang Songsheng, Jian-Min Wang, Yuan Cao, XueFei Chen, JianPing Xiong, Zhi-Xiang Zhang and Rong-Gen Cai","doi":"10.3847/1538-4357/ad9d10","DOIUrl":"https://doi.org/10.3847/1538-4357/ad9d10","url":null,"abstract":"The growing “Hubble tension” has prompted the need for precise measurements of cosmological distances. This paper demonstrates a purely geometric approach for determining the distances to extragalactic binaries through a joint analysis of spectroastrometry (SA), radial velocity (RV), and light-curve (LC) observations. A parameterized model for the binary system is outlined, and simulated SA, RV, and LC data are computed to infer the probability distribution of model parameters based on the mock data. The impacts of data quality and binary parameters on the distance uncertainties are comprehensively analyzed, showcasing the method’s potential for high-precision distance measurements. For a typical eclipsing binary in the Large Magellanic Cloud, the distance uncertainty is approximately 6% under reasonable observational conditions. Within a specific range of data quality and input parameters, the distance measurement precision of individual binary star systems is generally better than 10%. As a geometric method based on the simplest dynamics, it is independent of empirical calibration, and the systematics caused by model selections can be tested using nearby binaries with known distances. By measuring multiple binary star systems or monitoring one binary system repeatedly, geometric distance measurements of nearby galaxies can be achieved, providing valuable insights into the Hubble tension and advancing our understanding of the Universe’s structure and evolution.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990115","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 : 2025-01-20DOI: 10.3847/1538-4357/ad9d37
Kristen C. Dage, Evangelia Tremou, Bolivia Cuevas Otahola, Eric W. Koch, Kwangmin Oh, Richard M. Plotkin, Vivian L. Tang, Muhammad Ridha Aldhalemi, Zainab Bustani, Mariam Ismail Fawaz, Hans J. Harff, Amna Khalyleh, Timothy McBride, Jesse Mason, Anthony Preston, Cortney Rinehart, Ethan Vinson, Gemma Anderson, Edward M. Cackett, Shih Ching Fu, Sebastian Kamann, Teresa Panurach, Renuka Pechetti, Payaswini Saikia, Susmita Sett, Ryan Urquhart and Christopher Usher
Intermediate-mass black holes (102 < MBH < 105M⊙) are an open question in our understanding of black hole evolution and growth. They have long been linked to dense star cluster environments, thanks to cluster dynamics, but there are a limited number of secure detections. We leverage existing X-ray observations from the Chandra X-ray Observatory and optical catalogs from the Hubble Space Telescope (HST) as well as new radio observations from the Karl G. Jansky Very Large Array to search for any evidence of accreting black holes in young massive star clusters in the nearby galaxy M51. We find that of 44 bright (LX > 1038 erg s−1) X-ray point sources in M51, 24 had probable matches to objects including possible associated star clusters in the HST Legacy Extragalactic UV Survey catalog, seven of which were classified as contaminants (background galaxies or foreground stars). We explore the optical properties of the remaining 17 sources, including cluster age and mass estimates, and search for radio counterparts in the 8–12 GHz band. The lack of radio counterparts to X-ray sources we know to be associated with young massive star clusters in M51 suggests that we do not significantly detect hard-state intermediate-mass black holes (IMBHs) ~104 M⊙ or above. However, more sensitive radio facilities, like the Square Kilometre Array and next-generation Very Large Array, may be able to provide evidence for IMBHs with masses down to ~103 M⊙.
{"title":"Detecting the Black Hole Candidate Population in M51’s Young Massive Star Clusters: Constraints on Accreting Intermediate-mass Black Holes","authors":"Kristen C. Dage, Evangelia Tremou, Bolivia Cuevas Otahola, Eric W. Koch, Kwangmin Oh, Richard M. Plotkin, Vivian L. Tang, Muhammad Ridha Aldhalemi, Zainab Bustani, Mariam Ismail Fawaz, Hans J. Harff, Amna Khalyleh, Timothy McBride, Jesse Mason, Anthony Preston, Cortney Rinehart, Ethan Vinson, Gemma Anderson, Edward M. Cackett, Shih Ching Fu, Sebastian Kamann, Teresa Panurach, Renuka Pechetti, Payaswini Saikia, Susmita Sett, Ryan Urquhart and Christopher Usher","doi":"10.3847/1538-4357/ad9d37","DOIUrl":"https://doi.org/10.3847/1538-4357/ad9d37","url":null,"abstract":"Intermediate-mass black holes (102 < MBH < 105M⊙) are an open question in our understanding of black hole evolution and growth. They have long been linked to dense star cluster environments, thanks to cluster dynamics, but there are a limited number of secure detections. We leverage existing X-ray observations from the Chandra X-ray Observatory and optical catalogs from the Hubble Space Telescope (HST) as well as new radio observations from the Karl G. Jansky Very Large Array to search for any evidence of accreting black holes in young massive star clusters in the nearby galaxy M51. We find that of 44 bright (LX > 1038 erg s−1) X-ray point sources in M51, 24 had probable matches to objects including possible associated star clusters in the HST Legacy Extragalactic UV Survey catalog, seven of which were classified as contaminants (background galaxies or foreground stars). We explore the optical properties of the remaining 17 sources, including cluster age and mass estimates, and search for radio counterparts in the 8–12 GHz band. The lack of radio counterparts to X-ray sources we know to be associated with young massive star clusters in M51 suggests that we do not significantly detect hard-state intermediate-mass black holes (IMBHs) ~104 M⊙ or above. However, more sensitive radio facilities, like the Square Kilometre Array and next-generation Very Large Array, may be able to provide evidence for IMBHs with masses down to ~103 M⊙.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990118","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 : 2025-01-20DOI: 10.3847/1538-4357/ad9b0a
Man-Hei Ng, Xiaoping Zhang and P. F. Chen
The impulsive phase of solar flares is often accompanied by the depletion of the elements with low first ionization potential (FIP), whose abundance decreases from the coronal level to the photospheric level, and then recovers back to the coronal level during the decay phase. Recently, we analyzed the soft X-ray spectroscopic data of the 2024 February 16 flare event observed by the Macao Science Satellite-1B/Soft X-ray Detection Units. Surprisingly, however, it is revealed that the depletion of the low-FIP elements occurred well before the flare impulsive phase. The timing of this change provides important clues about the location of magnetic reconnection, shedding light on the mass and energy transfer between different layers of the solar atmosphere. By examining the multiwavelength data from the Solar Dynamics Observatory and CHASE missions, we found that there was no filament 0.4 hr before the flare eruption. However, an erupting filament was detected in association with the flare event. Based on these features, we propose for the first time that the flare/filament eruption for this event was initiated by magnetic reconnection in the solar chromosphere, rather than in the corona as stated in the standard flare model.
{"title":"A Peculiar Feature of the First Ionization Potential Effect Before a Solar Flare Impulsive Phase Observed by MSS-1B, CHASE, and SDO","authors":"Man-Hei Ng, Xiaoping Zhang and P. F. Chen","doi":"10.3847/1538-4357/ad9b0a","DOIUrl":"https://doi.org/10.3847/1538-4357/ad9b0a","url":null,"abstract":"The impulsive phase of solar flares is often accompanied by the depletion of the elements with low first ionization potential (FIP), whose abundance decreases from the coronal level to the photospheric level, and then recovers back to the coronal level during the decay phase. Recently, we analyzed the soft X-ray spectroscopic data of the 2024 February 16 flare event observed by the Macao Science Satellite-1B/Soft X-ray Detection Units. Surprisingly, however, it is revealed that the depletion of the low-FIP elements occurred well before the flare impulsive phase. The timing of this change provides important clues about the location of magnetic reconnection, shedding light on the mass and energy transfer between different layers of the solar atmosphere. By examining the multiwavelength data from the Solar Dynamics Observatory and CHASE missions, we found that there was no filament 0.4 hr before the flare eruption. However, an erupting filament was detected in association with the flare event. Based on these features, we propose for the first time that the flare/filament eruption for this event was initiated by magnetic reconnection in the solar chromosphere, rather than in the corona as stated in the standard flare model.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990064","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 : 2025-01-17DOI: 10.3847/1538-4357/ad9b7d
Chang Zhou, Yang Guo, Guoyin Chen, Ye Qiu and M.D. Ding
We observed three recurrent blowout jets in an active region with the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory. Using Helioseismic Magnetic Imager data we found that the magnetic flux of an emerging negative pole increases steadily before declining just as the jets erupt. Certain physical quantities, such as the total unsigned vertical current, align with the periodicity of the jets. The differential affine velocity of vector magnetograms reveals strong shear around the negative pole. The Doppler velocity map, calculated from the Hα spectra observed by the Chinese Hα Solar Explorer, shows upflows with large initial velocity before they can be observed by AIA. The magnetic field derived from the nonlinear force-free field (NLFFF) model suggests a topology akin to a fan–spine structure, consistent with AIA images. We calculated the evolution of the volumetric helicity ratio using the NLFFF model and found its phase aligns with the jet flux in AIA 171 Å. These results suggest that recurrent jets may be triggered by the accumulation and release of energy and helicity, driven by emergence, shearing, and cancellation of photospheric magnetic field.
{"title":"Observational Study of Recurrent Jets: Evolution of Magnetic Flux, Current, and Helicity","authors":"Chang Zhou, Yang Guo, Guoyin Chen, Ye Qiu and M.D. Ding","doi":"10.3847/1538-4357/ad9b7d","DOIUrl":"https://doi.org/10.3847/1538-4357/ad9b7d","url":null,"abstract":"We observed three recurrent blowout jets in an active region with the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory. Using Helioseismic Magnetic Imager data we found that the magnetic flux of an emerging negative pole increases steadily before declining just as the jets erupt. Certain physical quantities, such as the total unsigned vertical current, align with the periodicity of the jets. The differential affine velocity of vector magnetograms reveals strong shear around the negative pole. The Doppler velocity map, calculated from the Hα spectra observed by the Chinese Hα Solar Explorer, shows upflows with large initial velocity before they can be observed by AIA. The magnetic field derived from the nonlinear force-free field (NLFFF) model suggests a topology akin to a fan–spine structure, consistent with AIA images. We calculated the evolution of the volumetric helicity ratio using the NLFFF model and found its phase aligns with the jet flux in AIA 171 Å. These results suggest that recurrent jets may be triggered by the accumulation and release of energy and helicity, driven by emergence, shearing, and cancellation of photospheric magnetic field.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142987332","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 : 2025-01-17DOI: 10.3847/1538-4357/ad9bae
Yirui Zheng and Juntai Shen
Galactic bars can form via the internal bar instability or external tidal perturbations by other galaxies. We systematically compare the properties of the bars formed through the two mechanisms with a series of controlled N-body simulations that form bars through internal or external mechanisms. We create three disk galaxy models with different dynamical “hotness” and evolve them in isolation and under flyby interactions. In the cold- and warm-disk models, where bars can form spontaneously in isolation, tidally induced bars are promoted to a more “advanced” evolutionary stage. However, these bars have similar pattern speeds to those formed spontaneously within the same disk. Bars formed from both mechanisms have similar distributions in pattern-speed–bar-strength (Ωp − A2) space and exhibit comparable ratios of corotation radius to bar length ( ). Dynamical analyses suggest that the inner stellar disk loses the same amount of angular momentum, irrespective of the presence or intensity of the perturbation, which possibly explains the resemblance between tidally and spontaneously formed bars. In the hot-disk model, which avoids the internal bar instability in isolation, a bar forms only under perturbations and rotates more slowly than those in the cold and warm disks. Thus, if “tidally induced bars” refer exclusively to those in galaxies that are otherwise stable against bar instability, they indeed rotate slower than internally induced ones. However, the pattern speed difference is due to the difference in the internal properties of the bar host galaxies, not the different formation mechanisms.
{"title":"Comparison of Bar Formation Mechanisms. I. Does a Tidally Induced Bar Rotate Slower than an Internally Induced Bar?","authors":"Yirui Zheng and Juntai Shen","doi":"10.3847/1538-4357/ad9bae","DOIUrl":"https://doi.org/10.3847/1538-4357/ad9bae","url":null,"abstract":"Galactic bars can form via the internal bar instability or external tidal perturbations by other galaxies. We systematically compare the properties of the bars formed through the two mechanisms with a series of controlled N-body simulations that form bars through internal or external mechanisms. We create three disk galaxy models with different dynamical “hotness” and evolve them in isolation and under flyby interactions. In the cold- and warm-disk models, where bars can form spontaneously in isolation, tidally induced bars are promoted to a more “advanced” evolutionary stage. However, these bars have similar pattern speeds to those formed spontaneously within the same disk. Bars formed from both mechanisms have similar distributions in pattern-speed–bar-strength (Ωp − A2) space and exhibit comparable ratios of corotation radius to bar length ( ). Dynamical analyses suggest that the inner stellar disk loses the same amount of angular momentum, irrespective of the presence or intensity of the perturbation, which possibly explains the resemblance between tidally and spontaneously formed bars. In the hot-disk model, which avoids the internal bar instability in isolation, a bar forms only under perturbations and rotates more slowly than those in the cold and warm disks. Thus, if “tidally induced bars” refer exclusively to those in galaxies that are otherwise stable against bar instability, they indeed rotate slower than internally induced ones. However, the pattern speed difference is due to the difference in the internal properties of the bar host galaxies, not the different formation mechanisms.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142987333","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}
Type I gamma-ray bursts (GRBs) are believed to originate from compact binary mergers usually with a duration of main emission less than 2 s. However, recent observations of GRB 211211A and GRB 230307A indicate that some merger-origin GRBs could last much longer. Since they show strikingly similar properties (indicating a common mechanism), which are different from the classic “long”-short burst (e.g., GRB 060614), we find they form an interesting subclass of type I GRBs, and we suggest to name them as type IL GRB. We find that the prompt emission of type IL GRB is composed of three episodes: (1) a precursor followed by a short quiescent (or weak emission) period, (2) a long-duration main emission, and (3) an extended emission. With this burst pattern, a good candidate, GRB 170228A, was found in the Fermi/Gamma-ray Burst Monitor archive data. Temporal and spectral analyses indeed show that GRB 170228A falls in the same group with GRB 211211A and GRB 230307A in many diagnostic figures. Thus, this burst pattern could be a good reference for rapidly identifying type IL GRBs and very helpful for conducting low-latency follow-up observation. We estimated the occurrence rate and discussed the physical origins and implications for the three emission episodes of type IL GRBs. Our analysis suggests the premerger precursor model, especially the magnetar super flare model, is more favored for type IL GRBs. More observations in multiwavelength and multimessenger are required to deepen our understanding of this subclass of GRB.
{"title":"A Subclass of Gamma-Ray Burst Originating from Compact Binary Merger","authors":"Chen-Wei Wang, Wen-Jun Tan, Shao-Lin Xiong, Shu-Xu Yi, Rahim Moradi, Bing Li, Zhen Zhang, Yu Wang, Yan-Zhi Meng, Bo-Bing Wu, Jia-Cong Liu, Yue Wang, Sheng-Lun Xie, Wang-Chen Xue, Zheng-Hang Yu, Peng Zhang, Wen-Long Zhang, Yan-Qiu Zhang and Chao Zheng","doi":"10.3847/1538-4357/ad98ec","DOIUrl":"https://doi.org/10.3847/1538-4357/ad98ec","url":null,"abstract":"Type I gamma-ray bursts (GRBs) are believed to originate from compact binary mergers usually with a duration of main emission less than 2 s. However, recent observations of GRB 211211A and GRB 230307A indicate that some merger-origin GRBs could last much longer. Since they show strikingly similar properties (indicating a common mechanism), which are different from the classic “long”-short burst (e.g., GRB 060614), we find they form an interesting subclass of type I GRBs, and we suggest to name them as type IL GRB. We find that the prompt emission of type IL GRB is composed of three episodes: (1) a precursor followed by a short quiescent (or weak emission) period, (2) a long-duration main emission, and (3) an extended emission. With this burst pattern, a good candidate, GRB 170228A, was found in the Fermi/Gamma-ray Burst Monitor archive data. Temporal and spectral analyses indeed show that GRB 170228A falls in the same group with GRB 211211A and GRB 230307A in many diagnostic figures. Thus, this burst pattern could be a good reference for rapidly identifying type IL GRBs and very helpful for conducting low-latency follow-up observation. We estimated the occurrence rate and discussed the physical origins and implications for the three emission episodes of type IL GRBs. Our analysis suggests the premerger precursor model, especially the magnetar super flare model, is more favored for type IL GRBs. More observations in multiwavelength and multimessenger are required to deepen our understanding of this subclass of GRB.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990119","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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