The Astrophysical Journal Letters最新文献_第3页

Gamma-Ray Burst Timing: Decoding the Hidden Slow Jets in GRB 060729 伽玛射线暴计时：解码GRB 060729中隐藏的慢喷流

The Astrophysical Journal Letters Pub Date : 2025-05-07 DOI: 10.3847/2041-8213/add00e

Jin-Jun Geng, Ding-Fang Hu, Hao-Xuan Gao, Yi-Fang Liang, Yan-Long Hua, Guo-Rui Zhang, Tian-Rui Sun, Bing Li, Yuan-Qi Liu, Fan Xu, Chen Deng, Chen-Ran Hu, Ming Xu, Yong-Feng Huang, Miao-Miao Zhang, Min Fang, Jing-Zhi Yan, Tao An and Xue-Feng Wu

{"title":"Gamma-Ray Burst Timing: Decoding the Hidden Slow Jets in GRB 060729","authors":"Jin-Jun Geng, Ding-Fang Hu, Hao-Xuan Gao, Yi-Fang Liang, Yan-Long Hua, Guo-Rui Zhang, Tian-Rui Sun, Bing Li, Yuan-Qi Liu, Fan Xu, Chen Deng, Chen-Ran Hu, Ming Xu, Yong-Feng Huang, Miao-Miao Zhang, Min Fang, Jing-Zhi Yan, Tao An and Xue-Feng Wu","doi":"10.3847/2041-8213/add00e","DOIUrl":"https://doi.org/10.3847/2041-8213/add00e","url":null,"abstract":"Gamma-ray bursts (GRBs) are luminous stellar explosions characterized by the ejection of relativistic jets. This work proposes a novel paradigm to study these GRB jets. By analyzing the timing information of prompt pulses and X-ray flares, in conjunction with the multiwavelength afterglow observations, we identify three distinct jets in the extraordinary GRB 060729, with initial bulk Lorentz factors ranging from approximately 20 to 80, smaller than typical values of >100. These three jets undergo two successive collisions, producing the observed pair of X-ray flares. Following these interactions, the system evolves into a fast, narrow jet and a slower, hollow jet that continues to propagate in the circumburst medium, evidenced by the notable twin bumps observed in the X-ray and optical afterglow of GRB 060729. Our findings demonstrate that the timing of the early emission enables us to measure the velocities of the GRB jets. The proposed paradigm enhances our understanding of jet dynamics and shock interactions and serves as a powerful tool for probing the physics of the central engine with the expanded sample in the current golden era of GRB research.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143920154","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}

引用次数: 0

Characterizing the Impact of Alfvén Wave Forcing in Interplanetary Space on the Distribution of Near-Earth Solar Wind Speeds 表征行星际空间alfvsamn波强迫对近地太阳风速度分布的影响

The Astrophysical Journal Letters Pub Date : 2025-05-07 DOI: 10.3847/2041-8213/add0a6

B. L. Alterman

{"title":"Characterizing the Impact of Alfvén Wave Forcing in Interplanetary Space on the Distribution of Near-Earth Solar Wind Speeds","authors":"B. L. Alterman","doi":"10.3847/2041-8213/add0a6","DOIUrl":"https://doi.org/10.3847/2041-8213/add0a6","url":null,"abstract":"Broadly, solar wind source regions can be classified by their magnetic topology as intermittently and continuously open to the heliosphere. Early models of solar wind acceleration do not account for the fastest, nontransient solar wind speeds observed near-Earth, and energy must be deposited into the solar wind after it leaves the Sun. Alfvén wave energy deposition and thermal pressure gradients are likely candidates, and the relative contribution of each acceleration mechanism likely depends on the source region. Although solar wind speed is a rough proxy for solar wind source region, it cannot unambiguously identify source region topology. Using near-Sun observations of the solar wind’s kinetic energy flux, we predict the expected kinetic energy flux near Earth. This predicted kinetic energy flux corresponds to the range of solar wind speeds observed in the fast solar wind and we infer that the solar wind’s near-Sun kinetic energy flux is sufficient to predict the distribution of the fastest, nontransient speeds observed near Earth. Applying a recently developed model of solar wind evolution in the inner heliosphere, we suggest that the acceleration required to generate this distribution of the fastest, nontransient speeds is likely due to the continuous deposition of energy by Alfvén wave forcing during the solar wind’s propagation through interplanetary space. We infer that the solar wind’s Alfvénicity can statistically map near-Earth observations to their source regions because the Alfvén wave forcing that the solar wind experiences in transit is a consequence of the source region topology.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143920155","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}

引用次数: 0

Constraints on Nonthermal Pressure at Galaxy Cluster Outskirts from a Joint SPT and XMM-Newton Analysis 星系团外围非热压约束的SPT和XMM-Newton联合分析

The Astrophysical Journal Letters Pub Date : 2025-05-06 DOI: 10.3847/2041-8213/adc676

Arnab Sarkar, Michael McDonald, Lindsey Bleem, Mark Bautz, Bradford A. Benson, Priyanka Chakraborty, Catherine E. Grant, Christine Jones, Florian Kéruzoré, Eric D. Miller, Scott Randall, Charles Romero, Taweewat Somboonpanyakul and Yuanyuan Su

{"title":"Constraints on Nonthermal Pressure at Galaxy Cluster Outskirts from a Joint SPT and XMM-Newton Analysis","authors":"Arnab Sarkar, Michael McDonald, Lindsey Bleem, Mark Bautz, Bradford A. Benson, Priyanka Chakraborty, Catherine E. Grant, Christine Jones, Florian Kéruzoré, Eric D. Miller, Scott Randall, Charles Romero, Taweewat Somboonpanyakul and Yuanyuan Su","doi":"10.3847/2041-8213/adc676","DOIUrl":"https://doi.org/10.3847/2041-8213/adc676","url":null,"abstract":"We present joint South Pole Telescope and XMM-Newton observations of eight massive galaxy clusters (0.8–2 × 1015M⊙) spanning a redshift range of 0.16–0.35. Employing a novel Sunyaev–Zel’dovich + X-ray fitting technique, we effectively constrain the thermodynamic properties of these clusters out to the virial radius. The resulting best-fit electron density, deprojected temperature, and deprojected pressure profiles are in good agreement with previous observations of massive clusters. For the majority of the cluster sample (five out of eight clusters), the entropy profiles exhibit a self-similar behavior near the virial radius. We further derive hydrostatic mass, gas mass, and gas fraction profiles for all clusters up to the virial radius. Comparing the enclosed gas fraction profiles with the universal gas fraction profile, we obtain nonthermal pressure fraction profiles for our cluster sample at >0.5R500, demonstrating a steeper increase between R500 and R200 that is consistent with the hydrodynamical simulations. Our analysis yields nonthermal pressure fraction ranges of 8%–28% (median: 15% ± 11%) at R500 and 21%–35% (median: 27% ± 12%) at R200. Notably, weak-lensing mass measurements are available for only four clusters in our sample, and our recovered total cluster masses, after accounting for nonthermal pressure, are consistent with these measurements.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"1 1","pages":"L63"},"PeriodicalIF":0.0,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143920668","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}

引用次数: 0

Detection of Deuterated Hydrocarbon Nanoparticles in the Whirlpool Galaxy, M51 漩涡星系M51中氘化烃纳米颗粒的检测

The Astrophysical Journal Letters Pub Date : 2025-05-06 DOI: 10.3847/2041-8213/adc991

B. T. Draine, Karin Sandstrom, Daniel A. Dale, J.-D. T. Smith, Ryan Chown, Grant P. Donnelly, Sara E. Duval, Cory M. Whitcomb, Angela Adamo, L. Armus, Danielle A. Berg, Torsten Böker, Alberto D. Bolatto, Martha L. Boyer, Daniela Calzetti, B. G. Elmegreen, Brandt A. L. Gaches, Karl D. Gordon, L. K. Hunt, R. C. Kennicutt, Ralf S. Klessen, Thomas S.-Y. Lai, Adam K. Leroy, Sean T. Linden, Alex Pedrini, Noah S. J. Rogers, Julia C. Roman-Duval, Eva Schinnerer, Evan B. Skillman, Fabian Walter, Tony D. Weinbeck and Benjamin F. Williams

{"title":"Detection of Deuterated Hydrocarbon Nanoparticles in the Whirlpool Galaxy, M51","authors":"B. T. Draine, Karin Sandstrom, Daniel A. Dale, J.-D. T. Smith, Ryan Chown, Grant P. Donnelly, Sara E. Duval, Cory M. Whitcomb, Angela Adamo, L. Armus, Danielle A. Berg, Torsten Böker, Alberto D. Bolatto, Martha L. Boyer, Daniela Calzetti, B. G. Elmegreen, Brandt A. L. Gaches, Karl D. Gordon, L. K. Hunt, R. C. Kennicutt, Ralf S. Klessen, Thomas S.-Y. Lai, Adam K. Leroy, Sean T. Linden, Alex Pedrini, Noah S. J. Rogers, Julia C. Roman-Duval, Eva Schinnerer, Evan B. Skillman, Fabian Walter, Tony D. Weinbeck and Benjamin F. Williams","doi":"10.3847/2041-8213/adc991","DOIUrl":"https://doi.org/10.3847/2041-8213/adc991","url":null,"abstract":"Deuteration of hydrocarbon material, including polycyclic aromatic hydrocarbons (PAHs), has been proposed to account for the low gas-phase abundances of D in the interstellar medium (ISM). JWST spectra of four star-forming regions in M51 show an emission feature, with central wavelength ∼4.647 μm and FWHM 0.0265 μm, corresponding to the C–D stretching mode in aliphatic hydrocarbons. The emitting aliphatic material is estimated to have (D/H)aliph. ≈0.17 ± 0.02—a factor of ∼104 enrichment relative to the overall ISM. On ∼50 pc scales, deuteration levels toward four H ii regions in M51 are 2–3 times higher than in the Orion Bar photodissociation region (PDR), with implications for the processes responsible for the formation and evolution of hydrocarbon nanoparticles, including PAHs. The deuteration of the aliphatic material is found to anticorrelate with helium ionization in the associated H ii, suggesting that harsh far-UV radiation may act to lower the deuteration of aliphatics in PDRs near massive stars. No evidence is found for deuteration of aromatic material, with (D/H)arom. ≲ 0.016: deuteration of the aliphatic material exceeds that of the aromatic material by at least a factor of 10. The observed levels of deuteration may account for the depletion of D observed in the Galactic ISM. If so, the 4.65 μm feature may be detectable in absorption.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143927307","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}

引用次数: 0

On the Impact of Neutrinos on the Launching of Relativistic Jets from “Magnetars” Produced in Neutron Star Mergers 中微子对中子星合并产生的“磁星”发射相对论喷流的影响

The Astrophysical Journal Letters Pub Date : 2025-05-06 DOI: 10.3847/2041-8213/adcd6d

Carlo Musolino, Luciano Rezzolla and Elias R. Most

{"title":"On the Impact of Neutrinos on the Launching of Relativistic Jets from “Magnetars” Produced in Neutron Star Mergers","authors":"Carlo Musolino, Luciano Rezzolla and Elias R. Most","doi":"10.3847/2041-8213/adcd6d","DOIUrl":"https://doi.org/10.3847/2041-8213/adcd6d","url":null,"abstract":"A significant interest has emerged recently in assessing whether collimated and ultrarelativistic outflows can be produced by a long-lived remnant from a binary neutron star (BNS) merger, with different approaches leading to different outcomes. To clarify some of the aspect of this process, we report the results of long-term (i.e., ∼110 ms) state-of-the-art general relativistic magnetohydrodynamics simulations of the inspiral and merger of a BNS system of magnetized stars. We find that after ∼50 ms from the merger an α–Ω dynamo driven by the magnetorotational instability sets in in the densest regions of the disk and leads to the breakout of the magnetic field lines from the accretion disk around the remnant. The breakout is responsible for generating a collimated, magnetically driven outflow with only mildly relativistic velocities and for a violent eruption of electromagnetic energy. We provide evidence that this outflow is partly collimated via a Blandford–Payne mechanism. Finally, by including or not the radiative transport via neutrinos, we determine the role they play in the launching of the collimated wind. In this way, we conclude that the mechanism of magnetic field breakout we observe is robust and takes place even without neutrinos. Contrary to previous expectations, the inclusion of neutrino absorption and emission leads to a smaller baryon pollution in polar regions and hence accelerates the occurrence of the breakout, yielding a larger electromagnetic luminosity. Given the mildly relativistic nature of these disk-driven breakout outflows, it is difficult to consider them responsible for the jet phenomenology observed in short gamma-ray bursts.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143915594","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}

引用次数: 0

MINDS: The Very Low-mass Star and Brown Dwarf Sample Hidden Water in Carbon-dominated Protoplanetary Disks 思想：非常低质量的恒星和褐矮星样本在碳主导的原行星盘中隐藏了水

The Astrophysical Journal Letters Pub Date : 2025-05-06 DOI: 10.3847/2041-8213/adc692

Aditya M. Arabhavi, Inga Kamp, Ewine F. van Dishoeck, Thomas Henning, Hyerin Jang, Valentin Christiaens, Danny Gasman, Ilaria Pascucci, Giulia Perotti, Sierra L. Grant, David Barrado, Manuel Güdel, Pierre-Olivier Lagage, Alessio Caratti o Garatti, Fred Lahuis, L. B. F. M. Waters, Till Kaeufer, Jayatee Kanwar, Maria Morales-Calderón, Kamber Schwarz, Andrew D. Sellek, Benoît Tabone, Milou Temmink and Marissa Vlasblom

{"title":"MINDS: The Very Low-mass Star and Brown Dwarf Sample Hidden Water in Carbon-dominated Protoplanetary Disks","authors":"Aditya M. Arabhavi, Inga Kamp, Ewine F. van Dishoeck, Thomas Henning, Hyerin Jang, Valentin Christiaens, Danny Gasman, Ilaria Pascucci, Giulia Perotti, Sierra L. Grant, David Barrado, Manuel Güdel, Pierre-Olivier Lagage, Alessio Caratti o Garatti, Fred Lahuis, L. B. F. M. Waters, Till Kaeufer, Jayatee Kanwar, Maria Morales-Calderón, Kamber Schwarz, Andrew D. Sellek, Benoît Tabone, Milou Temmink and Marissa Vlasblom","doi":"10.3847/2041-8213/adc692","DOIUrl":"https://doi.org/10.3847/2041-8213/adc692","url":null,"abstract":"Infrared observations of the inner disks around very low-mass stars (VLMS; <0.3 M⊙) have revealed a carbon-rich gas composition in the terrestrial planet-forming regions. Contrary to the typically water-rich T Tauri disk spectra, only two disks around VLMS have been observed to be water-rich among more than 10 VLMS disks observed so far with JWST/MIRI. In this Letter, we systematically search for the presence of water and other oxygen-bearing molecules in the JWST/MIRI spectra of 10 VLMS disks from the MIRI mid-INfrared Disk Survey (MINDS). In addition to the two previously reported detections of water emission in this VLMS sample, we detect water emission in the spectra of three other sources and tentatively in one source, and we provide strong evidence for water emission in the remaining disks in the MINDS sample, most of which have bright emission from carbon-bearing molecules. We show that the C2H2 emission is much stronger than that of water for sources with low luminosities, and the hydrocarbons outshine the water emission in such conditions. We propose that the appearance of water-rich versus hydrocarbon-rich spectra is related to the location of the water reservoir in the disk relative to the main hydrocarbon reservoir. Our findings indicate that the terrestrial planet-forming regions in VLMS disks have high carbon-to-oxygen ratios (C/O > 1) but can still harbor ample water, similar to those in the T Tauri disks.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"141 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143915586","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}

引用次数: 0

Structure and Fragmentation Scale of a Massive Star-forming Filament in NGC 6334: High-resolution Mid-infrared Absorption Imaging with JWST NGC 6334大质量恒星形成丝的结构和破碎尺度：JWST高分辨率中红外吸收成像

The Astrophysical Journal Letters Pub Date : 2025-05-06 DOI: 10.3847/2041-8213/adc73d

Philippe André, Michael Mattern, Doris Arzoumanian, Yoshito Shimajiri, Annie Zavagno, Daisei Abe and Delphine Russeil

{"title":"Structure and Fragmentation Scale of a Massive Star-forming Filament in NGC 6334: High-resolution Mid-infrared Absorption Imaging with JWST","authors":"Philippe André, Michael Mattern, Doris Arzoumanian, Yoshito Shimajiri, Annie Zavagno, Daisei Abe and Delphine Russeil","doi":"10.3847/2041-8213/adc73d","DOIUrl":"https://doi.org/10.3847/2041-8213/adc73d","url":null,"abstract":"Dense filaments are believed to be representative of the initial conditions of star formation in molecular clouds. We have used the MIRI instrument on JWST to image the massive filament NGC 6334M at d ∼ 1.3 kpc with unprecedented resolution and dynamic range at 7.7 and 25.5 μm. Our observations reveal the fine structure of the filament in absorption against mid-infrared background emission. From the absorption data, we derive high-resolution column density maps and perform a detailed analysis of the structure of NGC 6334M. We find a median filament width of 0.12 ± 0.02 pc at both wavelengths, resolved by almost two orders of magnitude with MIRI, and consistent with the typical half-power width of Herschel filaments in nearby (d < 500 pc) clouds. The JWST data also reveal the presence of a quasi-periodic series of side filaments with a similar projected spacing of 0.125 ± 0.015 pc. Combining our JWST results with Spitzer and APEX/Herschel data, we perform a study of cloud structure over four orders of magnitude in linear scale. A convergence test shows that our width estimates for NGC 6334M are robust and reflect the presence of a true characteristic scale. While there is evidence of a Kolmogorov-like spectrum of small-scale fluctuations down to the 1.6 × 10−3 pc resolution of the JWST observations, we identify a break in the power spectrum of column density fluctuations at a scale ∼0.1–0.4 pc comparable to the width of NGC 6334M and its side filaments. This characteristic scale ∼0.1 pc has important implications for the origin of the star formation efficiency in dense gas and the initial mass function.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"72 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143927341","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}

引用次数: 0

ALMASOP: Detection of Turbulence-induced Mass Assembly Shocks in Starless Cores 无星核中湍流引起的质量组合冲击的检测

The Astrophysical Journal Letters Pub Date : 2025-05-06 DOI: 10.3847/2041-8213/adcd6a

Shih-Ying Hsu, Sheng-Yuan Liu, Xunchuan Liu, Pak Shing Li, Tie Liu, Dipen Sahu, Ken'ichi Tatematsu, Shanghuo Li, Naomi Hirano, Chin-Fei Lee and Sheng-Jun Lin

{"title":"ALMASOP: Detection of Turbulence-induced Mass Assembly Shocks in Starless Cores","authors":"Shih-Ying Hsu, Sheng-Yuan Liu, Xunchuan Liu, Pak Shing Li, Tie Liu, Dipen Sahu, Ken'ichi Tatematsu, Shanghuo Li, Naomi Hirano, Chin-Fei Lee and Sheng-Jun Lin","doi":"10.3847/2041-8213/adcd6a","DOIUrl":"https://doi.org/10.3847/2041-8213/adcd6a","url":null,"abstract":"Star formation is a series of mass assembly processes and starless cores; those cold and dense condensations in molecular clouds play a pivotal role as initial seeds of stars. With only a limited sample of known starless cores, however, the origin and growth of such stellar precursors had not been well characterized previously. Meanwhile, the recent discovery of CH3OH emission, which is generally associated with the desorbed icy mantle in warm regions, particularly at the periphery of starless cores, also remains puzzling. We present sensitive Atacama Large Millimeter/submillimeter Array (Band 3) observations (at 3 mm) toward a sample of newly identified starless cores in the Orion molecular cloud. The spatially resolved images distinctly indicate that the observed CH3OH and N2H+ emission associated with these cores are morphologically anticorrelated and kinematically offset from each other. We postulate that the CH3OH emission highlights the desorption of icy mantle by shocks resulting from gas piling onto dense cores in the filaments traced by N2H+. Our magnetohydrodynamic simulations of star formation in turbulent clouds combined with radiative transfer calculations and imaging simulations successfully reproduced the observed signatures and reaffirmed the above scenario at work. Our result serves as an intriguing and exemplary illustration, a snapshot in time, of the dynamic star-forming processes in turbulent clouds. The results offer compelling insights into the mechanisms governing the growth of starless cores and the presence of gas-phase complex organic molecules associated with these cores.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143915587","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}

引用次数: 0

Spatial Age Distribution of Classical Cepheids in Spiral Galaxies: The Cases of M31 and M33 螺旋星系中经典造父变星的空间年龄分布：以M31和M33为例

The Astrophysical Journal Letters Pub Date : 2025-05-06 DOI: 10.3847/2041-8213/adcf92

Giulia De Somma, Marcella Marconi, Vincenzo Ripepi, Santi Cassisi, Roberto Molinaro, Ilaria Musella, Teresa Sicignano and Erasmo Trentin

{"title":"Spatial Age Distribution of Classical Cepheids in Spiral Galaxies: The Cases of M31 and M33","authors":"Giulia De Somma, Marcella Marconi, Vincenzo Ripepi, Santi Cassisi, Roberto Molinaro, Ilaria Musella, Teresa Sicignano and Erasmo Trentin","doi":"10.3847/2041-8213/adcf92","DOIUrl":"https://doi.org/10.3847/2041-8213/adcf92","url":null,"abstract":"Classical Cepheids can be used as age indicators due to well-established period–age and period–age–color relations. G. De Somma et al. refined these relations by including a metallicity term and different mass–luminosity assumptions. In this study, we apply the period–age–metallicity relation for the first time to samples of classical Cepheids in M31 and M33. For both galaxies, we consider Cepheid coordinates and spatial distributions, along with the metallicity gradient by D. Zaritsky et al. and L. Magrini et al. to provide a metallicity estimate for each pulsator. Therefore, by applying the period–age–metallicity relation, we derive the individual ages of each Cepheid. By combining the individual ages and spatial distributions of classical Cepheids in M31 and M33, we built detailed age maps for both galaxies. Our analysis confirms a radial age gradient, with younger Cepheids preferentially found toward the galactic center. In M31, we confirm an outer ring at ∼11 kpc, consistent with previous studies, and identify for the first time an inner ring at ∼7 kpc, possibly associated with star formation episodes. Comparing age gradients at different angles, we find a consistent general trend of ages increasing monotonically with radius. At the same time, we observe smaller-scale differences, particularly in the 90°–180° quadrant, suggesting asymmetric star formation and possible dynamical influences. In contrast, M33 displays a steeper global age gradient, indicating a higher concentration of young stars toward its center. This study highlights the utility of Cepheids as stellar population tracers, providing insights into the star formation and dynamical evolution of spiral galaxies. Future works will extend this methodology to additional galaxies.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"104 1","pages":"L60"},"PeriodicalIF":0.0,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143920669","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}

引用次数: 0

An Actinide-boost Star Discovered in the Gaia-Sausage-Enceladus 在盖亚-香肠-土卫二发现了一颗锕系元素增强恒星

The Astrophysical Journal Letters Pub Date : 2025-05-05 DOI: 10.3847/2041-8213/adc8a3

Yangming Lin, Haining Li, Ruizheng Jiang, Wako Aoki, Satoshi Honda, Zhenyu He, Ruizhi Zhang, Zhuohan Li and Gang Zhao

{"title":"An Actinide-boost Star Discovered in the Gaia-Sausage-Enceladus","authors":"Yangming Lin, Haining Li, Ruizheng Jiang, Wako Aoki, Satoshi Honda, Zhenyu He, Ruizhi Zhang, Zhuohan Li and Gang Zhao","doi":"10.3847/2041-8213/adc8a3","DOIUrl":"https://doi.org/10.3847/2041-8213/adc8a3","url":null,"abstract":"We report the discovery of an actinide-boost, very metal-poor ( ), r-process-enhanced ( ) star, LAMOST J0804+5740, within the Gaia-Sausage-Enceladus (GSE). Based on the high-resolution (R ∼ 36,000 and 60,000) and high signal-to-noise ratio spectra obtained with the High Dispersion Spectrograph on the Subaru Telescope, the abundances of 48 species are determined. Its establishes it as the first confirmed actinide-boost star within the GSE. Comparative analysis of its abundance pattern with theoretical r-process models reveals that the magnetorotationally driven jet supernova r-process model with = 0.2 provides the best fit and successfully reproduces the actinide-boost signature. Kinematic analysis of actinide-boost stars reveals that approximately two-thirds of them are classified as ex situ stars, suggesting that actinide-boost stars are more likely to originate from accreted dwarf galaxies. As the first actinide-boost star identified within the GSE, J0804+5740 will provide valuable insights into r-process nucleosynthesis in accreted dwarf galaxies like the GSE, especially on the production of the heaviest elements.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143909952","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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