Two binary neutron star mergers, GW170817 and GW190425, have been detected by Advanced LIGO and Virgo. These signals were detected by matched-filter searches that assume the star's orbit has circularized by the time their gravitational-wave emission is observable. This suggests that their eccentricity is low, but full parameter estimation of their eccentricity has not yet been performed. We use gravitational-wave observations to measure the eccentricity of GW170817 and GW190425. We find that the eccentricity at a gravitational-wave frequency of 10 Hz is $e \leq 0.024$ and $e \leq 0.048$ for GW170817 and GW190425, respectively (90% confidence). This is consistent with the binaries being formed in the field, as such systems are expected to have circularized to $e \leq 10^{-4}$ by the time they reach the LIGO-Virgo band. Our constraint is a factor of two smaller that an estimate based on GW170817 being detected by searches that neglect eccentricity. However, we caution that we find significant prior dependence in our limits, suggesting that there is limited information in the signals. We note that other techniques used to constrain binary neutron star eccentricity without full parameter estimation may miss degeneracies in the waveform, and that for future signals it will be important to perform full parameter estimation with accurate waveform templates.
Eccentric or circular? A reanalysis of binary black hole gravitational wave events for orbital eccentricity signatures
Universitat de les Illes Balears（巴利阿里群岛大学）；Universität Zürich（苏黎世大学）；Max Planck Institut für Gravitationsphysik (Albert Einstein Institut)（马克斯·普朗克引力物理研究所（爱因斯坦研究所））；Institut de Ciències de l’Espai (ICE, CSIC)（空间科学研究所（加泰罗尼亚高等研究理事会））；Dutch National Institute for Subatomic Physics (Nikhef)（荷兰亚原子物理国家研究所）
Constraining initial orbital eccentricity of inspiral-dominated gravitational-wave events with an analytic approximant
The Chinese University of Hong Kong（香港中文大学）；Tata Institute of Fundamental Research（塔塔基础研究所）；Nikhef—National Institute for Subatomic Physics（NIKHEF-国家亚原子物理研究所）；KU Leuven（荷语鲁汶大学）；The Inter-University Centre for Astronomy and Astrophysics（大学间天文学与天体物理学中心）
Eccentricity in Disguise? Insights from GW231123 and Numerically Simulated Binary Black Hole Merger Signals
Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理研究所（爱因斯坦研究所））；Institute for Gravitation & the Cosmos, Department of Physics, Penn State University（宾夕法尼亚州立大学引力与宇宙学研究所物理学系）；Indian Institute of Technology, Bombay（印度理工学院孟买分校）；Gran Sasso Science Institute (GSSI)（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）；School of Physics and Astronomy and Institute for Gravitational Wave Astronomy, University of Birmingham（伯明翰大学物理与天文学院及引力波天文学研究所）
Parameter estimation for the GWTC-4.0 catalog with phenomenological waveform models that include orbital eccentricity and an updated description of spin precession
Universitat de les Illes Balears（巴利阿里群岛大学）；Institut de Ciències de l’Espai (ICE, CSIC)（空间科学研究所）
Eccentricity constraints disfavor single-single capture in nuclear star clusters as the origin of all LIGO-Virgo-KAGRA binary black holes
Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理研究所（爱因斯坦研究所））；University of Maryland（马里兰大学）；University of British Columbia（不列颠哥伦比亚大学）；California Institute of Technology（加州理工学院）；LIGO Laboratory（LIGO实验室）；Universitá degli Studi di Milano-Bicocca（米兰比可卡大学）；INFN, Sezione di Milano-Bicocca（意大利国家核物理研究所米兰比可卡分部）
Implications of the LISA stochastic signal from eccentric stellar mass black hole binaries in vacuum
Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台暗物质与空间天文重点实验室）；School of Astronomy and Space Sciences, University of Science and Technology of China（中国科学技术大学天文与空间科学学院）；SISSA（的里雅斯特国际高等研究学院）；INFN Sezione di Trieste（意大利国家核物理研究所的里雅斯特分部）；IFPU - Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）；Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理研究所（爱因斯坦研究所））；Dipartimento di Fisica “G. Occhialini”, Università degli Studi di Milano-Bicocca（米兰比可卡大学 G. Occhialini 物理系）；INFN, Sezione di Milano-Bicocca（意大利国家核物理研究所米兰比可卡分部）；Institute for Gravitational Wave Astronomy & School of Physics and Astronomy, University of Birmingham（伯明翰大学引力波天文学研究所及物理与天文学学院）
研究探讨了恒星级质量黑洞双星早期 inspiral 中的非圆轨道对随机引力波背景的影响，提出改进的 SGWB 模型并分析其对 LISA 检测的启示。
Astrophysical Implications of Eccentricity in Gravitational Waves from Neutron Star-Black Hole Binaries
Gravity Exploration Institute, School of Physics and Astronomy, Cardiff University（卡迪夫大学物理与天文学学院引力探索研究所）；Max Planck Institute for Astrophysics（马克斯·普朗克天体物理学研究所）；Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理学研究所（阿尔伯特·爱因斯坦研究所））；Adler Planetarium（阿德勒天文馆）；Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University（西北大学跨学科天体物理探索与研究中心）；National Astronomical Observatory of Japan, National Institutes of Natural Sciences（日本国立自然科学研究机构国立天文台）
A refined method for measuring cosmological distances using variability and proper motions in AGN with VLBI-detected counter-jets
Sejong University（世宗大学）；Korea Astronomy and Space Science Institute（韩国天体宇宙科学研究所）；University of Science and Technology（科学技术联合大学院大学）；York University（约克大学）；Institute of Astrophysics, Foundation for Research and Technology-Hellas（希腊研究与技术基金会天体物理研究所）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）
