分类： 天文学 >> 恒星和银河系 提交时间： 2023-12-31
Hong-Liang Yan
Jian-Rong Shi
Yu-Tao Zhou
Yong-Shou Chen
Er-Tao Li
Suyalatu Zhang
Shao-Lan Bi
Ya-Qian Wu
Zhi-Hong Li
Bing Guo
Wei-Ping Liu
Qi Gao
Jun-Bo Zhang
Ze-Ming Zhou
Hai-Ning Li
Gang Zhao
摘要： About 1% of giants have anomalously high Li abundances in their atmospheres, conflicting directly with the prediction of the standard stellar evolution models. This finding makes the production and evolution of Li in the Universe intriguing, not only in the sense of Big Bang nucleosynthesis or the interstellar medium, but also for the evolution of stars. Decades of efforts have been put into explaining why such extreme objects exist, yet the origins of Lirich giants are still being debated. Here we report the discovery of the most Li-rich giant known to date, with a very high Li abundance of 4.51. This rare phenomenon was observed coincidentally with another short-term event: the star is experiencing its luminosity bump on the red giant branch. Such a high Li abundance indicates that the star might be at the very beginning of its Li-rich phase, which provides a great opportunity to investigate the origin and evolution of Li in the Galaxy. A detailed nuclear simulation is presented with up-to-date reaction rates to recreate the Li enrichment process in this star. Our results provide tight constraints on both observational and theoretical points of view, suggesting that low-mass giants can internally produce Li to a very high level through 7Be transportation during the red giant phase.
分类： 天文学 >> 天体物理学 提交时间： 2023-12-29
Zhiyuan Ren
Xi Chen
Tie Liu
Emma Mannfors
Leonardo Bronfman
Fengwei Xu
Siyi Feng
Hongli Liu
Fanyi Meng
Amelia M. Stutz,
Shanghuo Li
Chang Won Lee,
Ke Wang
Jianwen Zhou
Di Li
Chen Wang
Chakali Eswaraiah
Anandmayee Tej
Long-Fei Chen
Hui Shi
摘要： We studied the unique kinematic properties in massive filament G352.63-1.07 at 1000-AU spatial scale with the dense molecular tracers observed with the Atacama Large Millimeter/submillimeter Array (ALMA). We find the central massive core M1 (12 Msun) being separated from the surrounding filament with a velocity difference of v-v_sys=-2 km/s and a transverse separation within 3 arcsec. Meanwhile, as shown in multiple dense-gas tracers, M1 has a spatial extension closely aligned with the main filament and is connected to the filament towards its both ends. M1 thus represents a very beginning state for a massive young star-forming core escaping from the parental filament, within a time scale of ~4000 years. Based on its kinetic energy (3.5x10^44 erg), the core escape is unlikely solely due to the original filament motion or magnetic field, but requires more energetic events such as a rapid intense anisotropic collapse. The released energy also seems to noticeably increase the environmental turbulence. This may help the filament to become stabilized again.
分类： 天文学 >> 天文学 提交时间： 2023-12-29
Pei Wang
Jian Li
Long Ji
Xian Hou
Erbil Gugercinoglu
Di Li
Diego F. Torres
Yutong Chen
Jiarui Niu
Weiwei Zhu
Bing Zhang
En-wei Liang
Li Zhang
Mingyu Ge
Zigao Dai
Lin Lin
Jinlin Han
Yi Feng
Chenhui Niu
Yongkun Zhang
摘要： Magnetars are neutron stars with extremely strong magnetic fields, frequently powering high-energy activity in X-rays. Pulsed radio emission following some X-ray outbursts have been detected, albeit its physical origin is unclear. It has long been speculated that the origin of magnetars' radio signals is different from those from canonical pulsars, although convincing evidence is still lacking. Five months after magnetar SGR 1935+2154's X-ray outburst and its associated Fast Radio Burst (FRB) 20200428, a radio pulsar phase was discovered. Here we report the discovery of X-ray spectral hardening associated with the emergence of periodic radio pulsations from SGR 1935+2154 and a detailed analysis of the properties of the radio pulses. The complex radio pulse morphology, which contains both narrow-band emission and frequency drifts, has not been seen before in other magnetars, but is similar to those of repeating FRBs - even though the luminosities are many orders of magnitude different. The observations suggest that radio emission originates from the outer magnetosphere of the magnetar, and the surface heating due to the bombardment of inward-going particles from the radio emission region is responsible for the observed X-ray spectral hardening.
分类： 天文学 >> 天文学 提交时间： 2023-12-29
Dengke Zhou
Pei Wang
Di Li
Jianhua Fang
Chenchen Miao
Paulo C. C. Freire
Lei Zhang
Dandan Zhang
Huaxi Chen
Yi Feng
Yifan Xiao
Jintao Xie
Xu Zhang
Chenwu Jin
Han Wang
Yinan Ke
Xuerong Guo
Rushuang Zhao
Chenhui Niu
Weiwei Zhu
摘要： Globular clusters harbor numerous millisecond pulsars; however, the detection of long-period pulsars within these clusters has been notably scarce. The search for long-period pulsars encounters significant challenges due to pronounced red noise interference, necessitating the crucial step of red noise removal in the data preprocessing. In this study, we use running median filtering to mitigate red noise in multiple globular cluster datasets obtained through observations with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Additionally, we estimated the minimum detectable flux density of pulsars ($S_{ rm min}$) considering this processing step, resulting in a function depicting how $S_{ rm min}$ varies with different duty cycles and periods. Subsequently, a systematic search for long-period pulsars was conducted on the globular cluster datasets after red noise elimination. Ultimately, two isolated long-period pulsars were discovered in the M15 globular cluster, with periods of approximately 1.928451 seconds and 3.960716 seconds, both exhibiting remarkably low pulse duty cycles of around 1 %. Using archived data, we obtained timing solutions for these pulsars. Based on the timing results, their positions are found to be close to the center of the M15 cluster. On the $P- dot{P}$ diagram, they both lie below the spin-up line, suggesting that their recycling process was likely interrupted, leading them to become isolated pulsars. Moreover, in our current search, these very faint long-period pulsars are exclusively identified in M15, and one possible reason for this could be the relatively close proximity and extremely high stellar formation rate of M15. As observational data accumulate and search algorithms undergo iterative enhancements, the prospect of discovering additional long-period pulsars within globular clusters, such as M15, becomes increasingly promising.
分类： 物理学 >> 核物理学 分类： 天文学 >> 天体物理学 提交时间： 2023-12-28
摘要： 相对论 Brueckner-Hartree-Fock (RBHF) 理论是相对论框架下重要的第一性原理方法，仅包含两体力即可以满意描述核物质的饱和性质。在完备的 Dirac 空间中自洽求解核物质 RBHF 方程，唯一确定了单粒子势的标量和矢量分量，避免了已有工作中由于忽略负能态所导致的不确定性，解决了 40 多年来 RBHF 计算中不能唯一确定单粒子势的问题。文章简要回顾 RBHF 理论的发展历史，阐述包含负能态做 RBHF 计算的必要性，介绍利用完备 Dirac 空间的 RBHF 理论，研究核物质性质和中子星物质性质的最新进展，包括有效质量、纯中子物质的每核子结合能、对称和纯中子物质的压强、中子星物质的粒子分数和状态方程、中子星的质量半径关系和潮汐形变等。文章还展望了完备 Dirac 空间的RBHF 理论在确定密度泛函理论参数、描述核子原子核弹性散射和研究中子星内部强子夸克相变等方面的可能应用。
分类： 天文学 >> 天文学 提交时间： 2023-12-25
Yuting Wang
Ruiyang Zhao
Zhongxu Zhai
Kazuya Koyama
Will J. Percival
Hong Guo
Yin Li
Gong-Bo Zhao
Takahiro Nishimichi
Héctor Gil-Marín
Yonghao Feng
Hanyu Zhang
Yi Wu
摘要： The small-scale linear information in galaxy samples typically lost during non-linear growth can be restored to a certain level by the density field reconstruction, which has been demonstrated for improving the precision of the baryon acoustic oscillations (BAO) measurements. As proposed in the literature, a joint analysis of the power spectrum before and after the reconstruction enables an efficient extraction of information carried by high-order statistics. However, the statistics of the post#2;reconstruction density field are difficult to model. In this work, we circumvent this issue by developing an accurate emulator for the pre-reconstructed, post-reconstructed, and cross power spectra (Ppre, Ppost, Pcross) up to k = 0.5 h Mpc1 based on the Dark Quest N-body simulations. The accuracy of the emulator is at percent level, namely, the error of the emulated monopole and quadrupole of the power spectra is less than 1% and 5% of the ground truth, respectively. A fit to an example power spectra using the emulator shows that the constraints on cosmological parameters get largely improved using Ppre+Ppost+Pcross with kmax = 0.25 h Mpc1 , compared to that derived from Ppre alone, namely, the constraints on (Ωm, H0, 8) are tightened by 41% 55%, and the uncertainties of the derived BAO and RSD parameters (, , f8) shrink by 28% 54%, respectively. This highlights the complementarity among Ppre, Ppost and Pcross, which demonstrates the efficiency and practicability of a joint Ppre, Ppost and Pcross analysis for cosmological implications.
分类： 物理学 >> 核物理学 分类： 物理学 >> 地球物理学、天文学和天体物理学 提交时间： 2023-12-22
摘要： 近十年的研究表明，夸克物质对称能对夸克物质的状态方程有重要影响。在本研究中，我们通过采用等效质量模型并在夸克质量标度中引入同位旋依赖项来研究夸克物质的稳定窗口。研究结果表明，足够大的同位旋强度依赖参数$C_I$可以显著地增大奇异夸克物质的稳定窗口，从而使计算结果可以同时满足天文观测数据PSR J1614-2230具有$1.928 pm 0.017$倍太阳质量和双中子星并合事件GW170817中得到的潮汐形变$70 le Lambda_{1.4} le 580$的约束。与奇异夸克物质的情况相反，~u-d~夸克物质的稳定窗口会随着同位旋强度依赖参数的增大而减小，从而使~u-d~夸克星无法支持相应的天文观测数据。最后，我们发现奇异夸克物质的对称能远大于 ~u-d~夸克物质的对称能，并且夸克间的单胶子交换相互作用会导致奇异夸克物质的对称能变软。
分类： 天文学 >> 天文学 提交时间： 2023-12-18
摘要： The Five-hundred-meter Aperture Spherical radio Telescope (FAST) has discovered more than 650 new pulsars, which account for 20% of our known Galactic pulsar population. In this paper, we estimate the prospect of a pulsar survey with a radio telescope array to be planned -- the FAST Array (FASTA), consists of six FAST-type telescopes. Such a sensitive radio telescope array would be a powerful instrument in probing the pulsar population deep into our Galaxy as well as in nearby galaxies. We simulate the FASTA pulsar discovery prospects with different Galactic pulsar population models and instrumental parameter combinations. We find that FASTA could detect tens of thousands of canonical pulsars and well-over thousands of millisecond pulsars. We also estimate the potential yield if the FASTA is used to search for pulsars from the nearby spiral galaxy M31, and find that it would probably discover around a hundred new radio pulsars.
分类： 天文学 >> 天体物理学 提交时间： 2023-12-17
Yuxiao Wu
Zhichen Pan
Lei Qian
Scott Ransom
BoJun Wang
Zhen Yan
Jintao Luo
Liyun Zhang
Minghui Li
Dejiang Yin
Baoda Li
Yifeng Li
Yinfeng Dai
Yaowei Li
Xinnan Zhang
Tong Liu
Yu Pan
摘要： We present the discovery of three pulsars in Globular Cluster M15 (NGC 7078) by the Five-hundred-meter Aperture Spherical radio Telescope (FAST).In the three pulsars, PSR~J2129+1210J (M15J) is a millisecond pulsar with a spinning period of 11.84 ms and a dispersion measure of 66.68 pc cm$^{-3}$.Both PSR~J2129+1210K and L (M15K and L) are long period pulsars with spinning periods of 1928 ms and 3961 ms, respectively,while M15L is the GC pulsar with the longest spinning period till now.The discoveries of M15K and L support the theory that core-collapsed Globular Clusters may contain partially recycled long period pulsars citep{verbunt-2014-slowpulsar}.With the same dataset, the timing solutions of M15A to H were updated,and the timing parameter P1 of M15F is different from the previous results, which is approximately 0.027$ times 10^{-18} ss^{-1}$ from our work and $0.032 times 10^{-18} ss^{-1}$ from Anderson's citep{anderson-1993}.As predicted by Rodolfi et al. citep{ridolfi-2017},the luminosity of M15C kept decreasing and the latest detection in our dataset is on December 20$^{ rm th}$, 2022.We also detected M15I for one more time.The different barycentric spin periods indicate that this pulsar should locate in a binary system,manifesting itself as the exceptional one in such a core-collapsing GC.
分类： 物理学 >> 核物理学 分类： 天文学 >> 天文仪器与技术 分类： 材料科学 >> 材料科学（综合） 提交时间： 2023-12-15
Pei-Yi Feng
Xi-Lei Sun
Zheng-Hua An
Yong Deng
Cheng-Er Wang
Huang Jiang
Jun-Jie Li
Da-Li Zhang
Xin-Qiao Li
Shao-Lin Xiong
Chao Zheng
Ke Gong
Sheng Yang
Xiao-Jing Liu
Min Gao
Xiang-Yang Wen
Ya-Qing liu
Yan-Bing Xu
Xiao-Yun Zhao
Jia-Cong Liu
摘要： The GECAM series of satellites utilizes LaBr3(Ce), LaBr3(Ce,Sr), and NaI(Tl) crystals as sensitive materials for gamma-ray detectors (GRDs). To investigate the non-linearity in the detection of low-energy gamma rays and address the errors in the calibration of the E-C relationship, comprehensive tests and comparative studies of the three aforementioned crystals were conducted using Compton electrons, radioactive sources, and monoenergetic X-rays. The non-linearity test results of the Compton electrons and X-rays demonstrated substantial differences, with all three crystals presenting a higher non-linearity for X/-rays than for Compton electrons. Despite the LaBr3(Ce) and LaBr3(Ce,Sr) crystals having higher absolute light yields, they exhibited a noticeable non-linear decrease in the light yield, especially at energies below 400 keV. The NaI(Tl) crystal demonstrated an excess light output in the 6200 keV range, reaching a maximum excess of 9.2% at 30 keV in the X-ray testing and up to 15.5% at 14 keV during Compton electron testing, indicating a significant advantage in the detection of low-energy gamma rays. Furthermore, we explored the underlying causes of the observed non-linearity in these crystals. This study not only elucidates the detector responses of GECAM, but also initiates a comprehensive investigation of the non-linearity of domestically produced lanthanum bromide and sodium iodide crystals.
分类： 天文学 提交时间： 2023-12-15 合作期刊: 《天文学报》
摘要： 大学天文学是高校天文学专业最重要的专业基础课程, 主要 讲授天文学的基础知识和发展全貌, 具有覆盖面广、知识点多的特点. 教材的质量对于帮助学生理解天文学的基本原理和方法、提高学术水平和科学素养起到关键作用. 对于非天文学专业的学生和天文爱好者, 天文学教材也是拓展科学知识和认知宇宙的重要途径. 我国的大学天文学教材建设与欧美发达国家相比在数量和质量上还有不小差距. 梳理了国内外较有代表性的大学天文学教材, 评述其特色、优势和有待改进之处, 比较中外教材在内容和写法上的异同. 通过分析国外优秀教材的编著理念、方法和技巧, 为我国未来天文学教材建设提供参考建议.
分类： 天文学 提交时间： 2023-12-15 合作期刊: 《天文学报》
摘要： 卡西尼号探测器携带了光学成像科学子系统(ISS: Imaging Science Subsystem), 在2004--2017年间拍摄了一些土星内卫星的图像. 部分图像中土星内卫星非常靠近土星环, 观测对象受土星环散射光影响导致测量精度差, 甚至无法测量. 由此提出一种适用于这类图像的背景消除算法, 可对受土星光环散射光影响的土星内卫星进行测量. 归算了7颗近环内卫星(土卫十(Janus)、土卫十一(Epimetheus)、土卫十五(Atlas)、土卫十六(Prometheus)、土卫十七(Pandora)、土卫三十二(Methone)和土卫四十九(Anthe))的70张ISS图像, 并与不消除散射光的方法进行了比较. 结果显示, 该方法至少可以提高43 %的精度. 和喷气推进实验室的土星卫星历表 lk SAT415相比, 测量得到的赤经和赤纬方向的残差均值分别为0.72 ;km和2.26 ;km, 标准差分别为10.99 ;km和11.36 ; km.
分类： 天文学 提交时间： 2023-12-15 合作期刊: 《天文学报》
摘要： 相对于核物质和奇异夸克物质, 仅由两味夸克构成的轻夸克物质(即ud夸克物质)有可能更稳定. 而对于由这三类物质构成的典型物质集团, 研究发现如果ud夸克物质具有较大的对称能, 那么其物质团会在特定大小(重子数$A approx1000$)时最稳定. 在这种情况下, 就可能存在由ud夸克物质团和电子构成的致密矮星, 即ud夸克矮星. 通过进一步研究这类ud夸克矮星的结构可知: 相较于传统的由原子核和电子构成的白矮星, ud夸克矮星通常具有较小的半径, 而被正常物质覆盖的ud夸克矮星的半径则在它们之间, 这与最近观测到的质量和半径都异常小的白矮星相符.
分类： 天文学 提交时间： 2023-12-15 合作期刊: 《天文学报》
摘要： 平方公里阵列(Square Kilometre Array, SKA)项目是建设全球最大射电望远镜的国际合作项目, 其灵敏度和测量速度将比当前所有的射电望远镜都要高出一个数量级. 连续谱巡天是SKA的主要观测模式之一, 基于连续谱成像建立巡天区域的标准星图, 将能为后续天文科学研究奠定重要基础. 银河系与河外星系全天默奇森宽场阵列拓展巡天(GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended, GLEAM-X)是2018---2020年利用SKA先导望远镜默奇森宽场阵列(Murchison Wide-field Array, MWA)二期拓展阵列开展的新的射电连续谱巡天项目, 观测期间积累了大量的低频巡天观测数据. 海量观测数据的自动化、大批量处理是SKA望远镜项目所面临的的最大挑战和难题之一, 基于分布式执行框架的成像管线优化经验将有助于解决海量数据处理问题. 详细介绍了GLEAM-X成像管线并对其进行整合和改进, 在中国SKA区域中心原型机(China SKA Regional Centre Prototype, CSRC-P)上实现了多条管线并行处理, 使用GLEAM-X观测数据验证成像管线系统的部署和测试其正确性. 随后为了优化管线提高处理效率, 使用数据激活流图形引擎(Data Activated Liu Graph Engine, DALiuGE), 将成像管线集成入DALiuGE执行框架中实现了管线的自动化分布式并行处理. 通过性能测试与结果分析表明, 基于DALiuGE执行框架进行优化的成像管线相较于传统的并行方式具有更好的性能优势、更灵活的适配性和可扩展性, 可支持未来SKA第一阶段试运行期间的大规模连续谱成像实验.
分类： 天文学 提交时间： 2023-12-15 合作期刊: 《天文学报》
摘要： 氢原子钟具有较高的短期稳定度, 将其作为主钟可在短期内产生高精度的本地时间信号. 但氢钟存在频率漂移现象, 导致其长期稳定度较差, 从而影响本地时间的准确性. 毫秒脉冲星自转高度稳定, 借助于其长期稳定度高的特性, 可定期实现对氢原子钟的频率驾驭, 并对实时信号加以控制. 首先分析了国际脉冲星计时阵(International Pulsar Timing Array, IPTA)第二批发布数据中四颗毫秒脉冲星的稳定度随时间的变化, 同时采用哈达玛方差分析了中国科学院国家授时中心(National Time Service Center, NTSC)一台氢钟的频率稳定性能, 最终给出了利用脉冲星驾驭氢原子钟频率的方法.
分类： 天文学 提交时间： 2023-12-15 合作期刊: 《天文学报》
摘要： 日冕是太阳大气活动的关键区域, 是日地空间天气的源头. 受观测限制, 对日冕低层大气等离子体结构和磁场状态的研究非常欠缺, 国际上对于可见光波段日冕低层大气的亮度分层研究很少. 利用丽江日冕仪YOGIS (Yunnan Green-line Imaging System)的日冕绿线($ rm Fe_{ Rmnum{14}}$5303 AA)观测资料, 对内日冕区域(1.03$R_{ odot}$--1.25$R_{ odot}$, $R_{ odot}$ 表示太阳半径)亮结构及其中冕环进行了有效的强度衰减分析. 对亮结构的强度在太阳径向高度上进行了指数衰减拟合, 比较这些拟合结果发现所得到的静态内冕环的衰减指数在一固定值附近. 然后将比较明显的冕环提取出来, 通过对不同高度的绿线强度进行指数拟合, 得出的衰减指数与亮结构中也比较相近, 这对进一步研究日冕中的各项物理参数演化提供了参考.
分类： 天文学 提交时间： 2023-12-15 合作期刊: 《天文学报》
摘要： 随着天线口径增大、频率升高, 日照热对其性能的影响愈发严重. 针对待建的新疆110 m大口径全可动射电望远镜, 建立其热分析有限元模型, 研究天线在夏至日不同太阳时刻的温度场分布特性. 结果如下: 一天中, 主反射面的最高温度可达42.86$^{ circ}$C, 出现在14时, 同时刻撑腿的温度也达到峰值, 为41.74$^{ circ}$C. 背架水平分区温差在5时、18时、19.5时均超过1$^{ circ}$C, 会对天线指向性能产生较大影响. 夜间天线结构温度分布亦不均匀, 俯仰结构的温差明显高于其他构件, 最大温差为6.42$^{ circ}$C, 通过数值模拟与试验相结合的方法, 证明了构件的壁厚差异是导致结构夜间温差较大的主要原因.
分类： 天文学 提交时间： 2023-12-15 合作期刊: 《天文学报》
摘要： 斜轴式望远镜是一种新颖的望远镜结构, 其独特的结构设计更适合南极等极端气候环境, 但目前国内外缺乏针对斜轴式望远镜详细的动力学建模与控制研究. 提出一套斜轴式望远镜动力学建模与鲁棒控制方法, 首先, 对斜轴式望远镜进行了动力学分析, 采用拉格朗日法建立望远镜2自由度刚体模型; 接着, 结合望远镜驱动系统的柔性和所受干扰, 完成了斜轴式望远镜的干扰情况下刚柔耦合系统数学模型的推导; 然后, 针对抗干扰问题, 根据所建数学模型, 设计了基于干扰观测器的滑模控制器, 对于所受干扰进行抑制, 实现了斜轴式望远镜的鲁棒控制; 最后, 仿真结果显示, 在考虑模型的非线性外部干扰的情况下, 相比于传统的比例-积分-微分控制器, 基于干扰观测器的滑模控制器使得系统具有更好的动态性能和抗干扰特性.
分类： 天文学 提交时间： 2023-12-15 合作期刊: 《天文学报》
摘要： 阿尔文波在太阳风中普遍存在, 对其中等离子体的加热与加速有重要意义. 从太阳风中的结构、太阳风湍流、太阳风全球模型、等离子体不稳定性(参量衰变不稳定性和火蛇管不稳定性)、太阳风的加热与加速等方面, 总结了近年来太阳风中阿尔文波相关的研究进展. 结合目前的研究趋势, 从亚阿尔文速太阳风、太阳风全球模型和太阳源区3个方向展望了未来阿尔文波的相关研究.
分类： 天文学 提交时间： 2023-12-15 合作期刊: 《天文学报》
摘要： 红矮星是质量最小, 光度最低的一类主序恒星. 随着探测技术的提升, 在其周围探测到了丰富的行星种群, 与其他类型恒星周围的行星具有不同的分布特征. 在红矮星周围, 类地行星具有较高的出现率, 由其构成的行星系统构型十分紧凑. 宜居带的范围更靠近主星, 更有利于搜寻宜居行星. 超级地球和亚海王星之间过渡半径的分布特征也与类太阳恒星存在差异. 巨行星在小质量恒星周围的发现更是对理论模型提出了巨大挑战.原行星盘中固体物质的质量随主星质量迅速衰减, 是否能够解释巨行星的起源仍然是未解之谜. 得益于TESS (Transiting Exoplanet Survey Satellite), James Webb和ALMA (Atacama Large Millimeter/submillimeter Array)等望远镜的观测, 为行星形成研究提供了新的认知和契机. 将回顾红矮星周围不同行星种群的观测, 并总结对于红矮星周围行星形成理论的最新认知.
点击量
通过
点击量
下载量
评论
待评议
