We present an analysis of three archival Chandra observations of the black hole V4641 Sgr, performed during a decline into quiescence. The last two observations in the sequence can be modeled with a simple power-law. The first spectrum, however, is remarkably similar to spectra observed in Seyfert-2 active galactic nuclei, which arise through a combination of obscuration and reflection from distant material. This spectrum of V4641 Sgr can be fit extremely well with a model including partial-covering absorption and distant reflection. This model recovers a Gamma = 2 power-law incident spectrum, typical of black holes at low Eddington fractions. The implied geometry is plausible in a high-mass X-ray binary like V4641 Sgr, and may be as compelling as explanations invoking Doppler-split line pairs in a jet, and/or unusual Comptonization. We discuss potential implications and means of testing these models.
Candidate X-ray Counterparts of Ultra-High-Energy Emission of the Galactic Microquasar V4641 Sgr Revealed by Einstein Probe
Nanjing University（南京大学）；Key Laboratory of Modern Astronomy and Astrophysics, Nanjing University, Ministry of Education（南京大学现代天文与天体物理教育部重点实验室）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；State Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所粒子天体物理国家重点实验室）；Tianfu Cosmic Ray Research Center（天府宇宙线研究中心）
XMM-Newton Resolves Parsec-scale X-ray Jets in the PeVatron Microquasar V4641 Sgr
Institute for Cosmic Ray Research, The University of Tokyo（宇宙线研究所，东京大学）；Interdisciplinary Theoretical & Mathematical Science Center (iTHEMS), RIKEN（理化学研究所交叉理论与数学科学中心(iTHEMS)）；INAF-Osservatorio Astronomico di Brera（意大利国家天体物理研究所布雷拉天文台）；Como Lake Center for Astrophysics (CLAP), DiSAT, Università degli Studi dell’Insubria（因苏布里亚大学地球科学与技术系科莫湖天体物理中心）；Columbia Astrophysics Laboratory, Columbia University（哥伦比亚大学哥伦比亚天体物理学实验室）；The University of Miyazaki（宫崎大学）；Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所粒子天体物理重点实验室）；Tianfu Cosmic Ray Research Center（天府宇宙线研究中心）；Department of Physics and Astronomy, University of Manitoba（曼尼托巴大学物理与天文学系）；Anton Pannekoek Institute for Astronomy, University of Amsterdam（阿姆斯特丹大学安东·潘内库克天体物理研究所）
Large-scale radio bubbles around the black hole transient V4641 Sgr
Université Paris Cité（巴黎西岱大学）；Université Paris-Saclay（巴黎萨克雷大学）；CEA（法国原子能和替代能源委员会）；CNRS（法国国家科学研究中心）；AIM（天体物理、分子与星际介质实验室）；University of Oxford（牛津大学）；University of Cape Town（开普敦大学）；Rhodes University（罗德岛大学）；South African Radio Astronomy Observatory（南非射电天文观测站）；INAF-Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；Istituto Nazionale di Astrofisica（意大利国家天体物理研究所）；Osservatorio Astronomico di Brera（布雷拉天文台）
A search for very high-energy flares from the microquasars GRS 1915+105, Circinus X-1, and V4641 Sgr using contemporaneous H.E.S.S. and RXTE observations
微类星体是潜在的$γ$射线发射体。最近在至少两个系统中报告了$γ$射线发射的短暂发作迹象：Cyg X-1和Cyg X-3。为了更好地理解$γ$射线是如何在这些系统中产生的，需要识别额外的$γ$射线发射微类星体。理论模型已经预测了微类星体在短暂爆发期间会发射甚高能量（VHE）$γ$射线。本文报告的观测目的是观测$γ$射线和X射线波段的宽带耀斑事件。利用高能光谱系统（H.E.S.S.）对三颗微类星体GRS 1915+105、Circinus X-1和V4641 Sgr进行了同期观测。这是由Rossi X射线定时探测器（RXTE）卫星和望远镜阵列组成的。对每个微类星体进行了X射线分析，并从同时期的H.E.S.S. S获得了VHE $γ$射线上限。观察得出。在三个系统中均未检测到显著的$γ$射线信号。对于GRS 1915+105、Circinus X-1和V4641 Sgr，观测历元的积分$γ$射线光子通量分别被限制为$I(> 560 {\rm\ GeV}) < 7.3\times10^{-13}$ cm $^{-2}$ s $^{-1}$、$I(> 560 {\rm\ GeV}) < 1.2\times10^{-12}$ cm $^{-2}$ s $^{-1}$和$I(> 240 {\rm\ GeV}) < 4.5\times10^{-12}$ cm $^{-2}$ s $^{-1}$。…
Hadronic Emissions from the Microquasar V4641 Sgr, SS433, and its implications in the Diffuse Galactic Emission
Presidency University（总统大学）；Gran Sasso Science Institute（格兰萨索科学研究所）；INFN/Laboratori Nazionali del Gran Sasso（意大利国家核物理研究所/格兰萨索国家实验室）；Aryabhatta Research Institute of Observational Sciences (ARIES)（阿亚巴哈观测科学研究所）；University of Johannesburg（约翰内斯堡大学）；Central University of Kashmir（克什米尔中央大学）
A Multi-messenger Search for a Nearby Microquasar Contributor to the Cosmic Ray Knee
School of Physical Science and Technology, Southwest Jiaotong University（西南交通大学物理科学与技术学院）；State Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所粒子天体物理国家重点实验室）；University of Chinese Academy of Sciences（中国科学院大学）；TIANFU Cosmic Ray Research Center（天府宇宙线研究中心）
Particle acceleration at recollimation shocks in sub-relativistic jets. A model for jets in Seyfert Galaxies, Microquasars and Protostellar Systems
INAF, Istituto Nazionale di Astrofisica（意大利国家天体物理研究所）；Universite Paris Cité（巴黎西岱大学）；Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange（法国蔚蓝海岸大学，蔚蓝海岸天文台，法国国家科学研究中心，拉格朗日实验室）；University of Pisa（比萨大学）；Institute of Nuclear Physics Polish Academy of Sciences（波兰科学院核物理研究所）
Leptonic and hadronic models of high-energy nebula around V4641 Sgr
Institut Polytechnique de Paris（巴黎理工学院）；Université de Paris Cite, CNRS, Astroparticule et Cosmologie（巴黎西岱大学、法国国家科学研究中心、亚原子粒子与宇宙学）；Laboratory of Astrophysics, Ecole Polytechnique Federale de Lausanne（洛桑联邦理工学院天体物理学实验室）；Institutt for fysikk, NTNU（挪威科技大学物理系）
Particle acceleration and non-thermal broadband spectrum of extended shocked outflows in black hole binary V4641 Sgr - a galactic pevatron
Ioffe Institute（伊俄费研究所）；Max Planck Institute for Astrophysics（马克斯·普朗克天体物理学研究所）；Space Research Institute (IKI)（太空研究所（IKI））；Rudolf Peierls Centre for Theoretical Physics, Department of Physics, University of Oxford（牛津大学物理系鲁道夫·派尔斯理论物理中心）
