中国科学院机构知识库网格系统: 检索

The Intrinsic Structure of Sagittarius A* at 1.3 cm and 7 mm 期刊论文 OAI收割
Astrophysical Journal, 2022, 卷号: 926, 期号: 2, 页码: 108
作者: Cho, Ilje; Zhao, Guang-Yao; Kawashima, Tomohisa; Kino, Motoki; Akiyama, Kazunori

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收藏 | 浏览/下载：15/0 | 提交时间：2023/06/19

magnetically arrested accretion base-line interferometry scatter-broadened image supermassive black-hole event-horizon galactic-center radio-source vlbi observations nonthermal electrons synchrotron emission Astronomy & Astrophysics

Timing Synchronization System on RF-Driven Neutral Beam Injection System 期刊论文 OAI收割
FUSION SCIENCE AND TECHNOLOGY, 2022
作者: Li, Y.; Hu, C. D.; Zhao, Y. Z.; Cui, Q. L.; Shu, X. L.

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收藏 | 浏览/下载：49/0 | 提交时间：2022/03/21

IEEE 1588-2019 synchronization radio-frequency-driven negative ion source neutral beam injection

Influence of magnetic filter on plasma parameters of the prototype RF ion source at ASIPP 期刊论文 OAI收割
FUSION ENGINEERING AND DESIGN, 2020, 卷号: 160
作者: Wang, Qi; Hu, Chundong; Xie, Yahong; Liang, Lizhen; Wei, Jianglong

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收藏 | 浏览/下载：42/0 | 提交时间：2021/04/26

Neutral beam heating Radio frequency negative ion source Magnetic field filter Electron temperature and density

No pulsed radio emission during a bursting phase of a Galactic magnetar 期刊论文 OAI收割
Nature, 2020, 卷号: 587, 页码: 63-65
作者: HXMT

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收藏 | 浏览/下载：44/0 | 提交时间：2022/02/08

Astrophysics - High Energy Astrophysical Phenomena Abstract: Fast radio bursts (FRBs) are millisecond-duration radio transients of unknown physical origin observed at extragalactic distances^1-3. It has long been speculated that magnetars are the engine powering repeating bursts from FRB sources^4-13, but no convincing evidence has been collected so far¹⁴. Recently, the Galactic magnetar SRG 1935+2154 entered an active phase by emitting intense soft íray bursts¹⁵. One FRB-like event with two peaks (FRB 200428) and a luminosity slightly lower than the faintest extragalactic FRBs was detected from the source, in association with a soft íray/hard-X-ray flare^18-21. Here we report an eight-hour targeted radio observational campaign comprising four sessions and assisted by multi-wavelength (optical and hard-X-ray) data. During the third session, 29 soft-íray repeater (SGR) bursts were detected in íray energies. Throughout the observing period, we detected no single dispersed pulsed emission coincident with the arrivals of SGR bursts, but unfortunately we were not observing when the FRB was detected. The non-detection places a fluence upper limit that is eight orders of magnitude lower than the fluence of FRB 200428. Our results suggest that FRB-SGR burst associations are rare. FRBs may be highly relativistic and geometrically beamed, or FRB-like events associated with SGR bursts may have narrow spectra and characteristic frequencies outside the observed band. It is also possible that the physical conditions required to achieve coherent radiation in SGR bursts are difficult to satisfy, and that only under extreme conditions could an FRB be associated with an SGR burst.

Constraining the X-Ray-Infrared Spectral Index of Second-timescale Flares from SGR 1935+2154 with Palomar Gattini-IR 期刊论文 OAI收割
The Astrophysical Journal, 2020, 卷号: 901, 页码: L7
作者: HXMT

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收藏 | 浏览/下载：24/0 | 提交时间：2022/02/08

Radio transient sources Magnetars Soft gamma-ray repeaters 2008 992 1471 Astrophysics - High Energy Astrophysical Phenomena Astrophysics - Instrumentation and Methods for Astrophysics Abstract: The Galactic magnetar SGR 1935+2154 has been reported to produce the first example of a bright millisecond-duration radio burst (FRB 200428) similar to the cosmological population of fast radio bursts (FRBs). The detection of a coincident bright X-ray burst represents the first observed multiwavelength counterpart of an FRB. However, the search for similar emission at optical wavelengths has been hampered by the high inferred extinction on the line of sight. Here, we present results from the first search for second-timescale emission from the source at near-infrared (NIR) wavelengths using the Palomar Gattini-IR observing system in the J band, enabled by a novel detector readout mode that allows short exposure times of ?0.84 s with 99.9% observing efficiency. With a total observing time of ?12 hr (?47,728 images) during its 2020 outburst, we place median 3Ҡlimits on the second-timescale NIR fluence of ?18 Jy ms (13.1 AB mag). The corresponding extinction-corrected limit is ?125 Jy ms for an estimated extinction of A_J = 2.0 mag. Our observations were sensitive enough to easily detect an NIR counterpart of FRB 200428 if the NIR emission falls on the same power law as observed across its radio to X-ray spectrum. We report nondetection limits from epochs of four simultaneous X-ray bursts detected by the Insight-HXMT and NuSTAR telescopes during our observations. These limits provide the most stringent constraints to date on fluence of flares at 10¹⁴ Hz, and constrain the fluence ratio of the NIR emission to coincident X-ray bursts to R_NIR ? 0.025 (fluence index ?0.35).

A novel approach of power allocation for secondary users in cognitive radio networks 期刊论文 OAI收割
COMPUTERS & ELECTRICAL ENGINEERING, 2019, 卷号: 75, 页码: 301-308
作者: Mukherjee, Amrit; Choudhury, Sagarika; Goswami, Pratik; Bayessa, Gezahegn Abdissa; Tyagi, Sumarga K. Sah

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收藏 | 浏览/下载：77/0 | 提交时间：2019/08/16

Cognitive radio Cooperative communication Wireless communication Blind source separation Autocorrelation Vector quantization

VLBI Studies of DAGN and SMBHB Hosting Galaxies 期刊论文 OAI收割
RADIO SCIENCE, 2018, 卷号: 53, 期号: 10, 页码: 1211-1217
作者: An, T.; Mohan, P.; Frey, S.

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收藏 | 浏览/下载：54/0 | 提交时间：2019/05/23

Dual Agn Supermassive Black Hole Binary Vlbi Observations Flat Spectrum Radio Cores High-resolution Imaging Source Compilation

Design of a water-cooled tube for high-power and long-pulse radio frequency ion source 期刊论文 OAI收割
FUSION ENGINEERING AND DESIGN, 2018, 卷号: 129, 期号: 无, 页码: 164-170
作者: Gu, Yuming; Wei, Jianglong; Xie, Yahong; Tao, Ling; Li, Jun

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收藏 | 浏览/下载：84/0 | 提交时间：2019/08/26

Neutral beam injection Radio frequency ion source Water-cooled ceramic Fluid-thermal-structural analysis

Diagnostics from three rising submillimeter bursts 期刊论文 OAI收割
RESEARCH IN ASTRONOMY AND ASTROPHYSICS, 2016, 卷号: 16, 期号: 2
作者: Zhou, Ai-Hua; Li, Jian-Ping; Wang, Xin-Dong

收藏 | 浏览/下载：25/0 | 提交时间：2016/09/27

Sun: submillimeter emission Sun: energetic electrons Sun: radio source environment

Study of temporal evolution of emission spectrum in a steeply rising submillimeter burst 期刊论文 OAI收割
RESEARCH IN ASTRONOMY AND ASTROPHYSICS, 2016, 卷号: 16, 期号: 1
作者: Li, Jian-Ping; Zhou, Ai-Hua; Wang, Xin-Dong

收藏 | 浏览/下载：18/0 | 提交时间：2016/09/27

Sun: submillimeter burst Sun: energetic electrons Sun: radio source size