We present a spectral analysis of NuSTAR and NICER observations of the luminous, persistently accreting neutron star (NS) low-mass X-ray binary Cygnus X-2. The data were divided into different branches that the source traces out on the Z-track of the X-ray color-color diagram; namely the horizontal branch, normal branch, and the vertex between the two. The X-ray continuum spectrum was modeled in two different ways that produced a comparable quality fit. The spectra showed clear evidence of a reflection component in the form of a broadened Fe K line, as well as a lower energy emission feature near 1 keV likely due to an ionized plasma located far from the innermost accretion disk. We account for the reflection spectrum with two independent models (relxillns and rdblur*rfxconv). The inferred inclination is in agreement with earlier estimates from optical observations of ellipsoidal light curve modeling (relxillns: $i=67^{\circ}\pm4^{\circ}$, rdblur*rfxconv: $i=60^{\circ}\pm10^{\circ}$). The inner disk radius remains close to the NS ($R_{\rm in}\leq1.15\ R_{\mathrm{ISCO}}$) regardless of the source position along the Z-track or how the 1 keV feature is modeled. Given the optically determined NS mass of $1.71\pm0.21\ M_{\odot}$, this corresponds to a conservative upper limit of $R_{\rm in}\leq19.5$ km for $M=1.92\ M_{\odot}$ or $R_{\rm in}\leq15.3$ km for $M=1.5\ M_{\odot}$. We compare these radius constraints to those obtained from NS gravitational wave merger events and recent NICER pulsar light curve modeling measurements.
The first comprehensive spectral and timing study of the ultra-compact X-ray binary 4U 1812-12 with NICER and NuSTAR
Department of physics, Visva-Bharati（维斯瓦-巴拉蒂大学物理系）；Indian Institute Of Astrophysics (IIA)（印度天体物理研究所）；Inter-University Centre for Astronomy & Astrophysics (IUCAA)（天文与天体物理跨大学中心）
Timing and Spectral Analysis of the 2024 Outburst of 2S 1553$-$542 with NuSTAR and NICER
University of Groningen（格罗宁根大学）；Wuhan University（武汉大学）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；Guizhou Minzu University（贵州民族大学）
Simultaneous NICER and NuSTAR Observations of the Neutron Star Low-mass X-ray Binary Serpens X-1
Wayne State University（韦恩州立大学）；University of Michigan（密歇根大学）；University of Cambridge（剑桥大学）；Space Sciences Lab, University of California, Berkeley（加州大学伯克利分校空间科学实验室）；Howard University（霍华德大学）；CRESST and NASA Goddard Space Flight Center（CRESST 和 NASA 戈达德太空飞行中心）；California Institute of Technology（加州理工学院）；Utah Valley University（犹他山谷大学）
Revisiting the 2021 Outburst of the BHC MAXI J1803-298 Using NICER, NuSTAR, and Insight-HXMT Data
South-Western Institute for Astronomy Research, Yunnan University（西南天体物理研究所，云南大学）；Indian Center for Space Physics（印度空间物理中心）；Institute of Astronomy, National Tsing Hua University（国立清华大学天文研究所）
Timing and Spectral Studies of PSR J2022+3842 with NICER and NuSTAR
Yunnan University（云南大学）；Nanjing Normal University（南京师范大学）；China West Normal University（西华师范大学）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）
Probing the emission geometry of the X-ray pulsar 2S 1417$-$624 during a weak outburst with NICER, IXPE, and NuSTAR
Institut für Astronomie und Astrophysik, Universität Tübingen（蒂宾根大学天文与天体物理研究所）；Research Center of Astronomy, QingHai University（青海大学天文研究中心）；Department of Physics and Astronomy, QingHai University（青海大学物理与天文系）；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）；University of Chinese Academy of Sciences, Chinese Academy of Sciences（中国科学院大学）
State-Dependent X-ray Variability in Cygnus X-1: A 12-Year NuSTAR Timing Study of Accretion Flow Geometry
Boston University（波士顿大学）；Raman Research Institute（拉曼研究所）；Indian Institute of Science Education and Research Bhopal（印度科学教育与研究学院博帕尔分校）；Florida International University（佛罗里达国际大学）；Miami Dade College（迈阿密戴德学院）；Osmania University（奥斯曼尼亚大学）；Physical Research Laboratory（物理研究实验室）；UN Center for Space Science and Technology Education in Asia and Pacific (CSSTEAP)（联合国亚洲及太平洋空间技术和外空活动教育训练中心）；Sardar Vallabhbhai National Institute of Technology, Surat（萨达尔·瓦拉巴伊国立技术学院苏拉特分校）；Pondicherry University（本地治里大学）；School of Sciences, JAIN (Deemed-to-be University), Bengaluru（JAIN（视为大学）班加罗尔理学院）；Janusz Gil Institute of Astronomy, University of Zielona Góra（绿山大学扬努什·吉尔天文学研究所）
Spectral Analysis of the 2019 and 2022 Outbursts of SAX J1808.4-3658
Montana State University（蒙大拿州立大学）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo（东京大学宇宙学前沿研究机构（WPI））；RTX（RTX公司）
A NuSTAR Reflection-Spectroscopy Survey of Cygnus X-1
Boston University（波士顿大学）；Raman Research Institute（拉曼研究所）；Indian Institute of Science Education and Research Bhopal（印度科学教育与研究学院博帕尔分校）；Janusz Gil Institute of Astronomy, University of Zielona Góra（绿山大学扬努什·吉尔天文学研究所）；Miami Dade College（迈阿密戴德学院）；Florida International University（佛罗里达国际大学）
Decoding Cygnus X-2: The Critical Role of Reflection in IXPE Data
Fudan University（复旦大学）；Eberhard-Karls Universität Tübingen（蒂宾根大学）；University of Warwick（华威大学）；Newcastle University（纽卡斯尔大学）；New Uzbekistan University（新乌兹别克斯坦大学）；University of Cambridge（剑桥大学）；INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所博洛尼亚天文与空间科学观测站）；Wayne State University（韦恩州立大学）；University of Amsterdam（阿姆斯特丹大学）；Anton Pannekoek Institute for Astronomy, University of Amsterdam（阿姆斯特丹大学安东·范·佩内贝克克天文学研究所）；Astronomical Institute of the Czech Academy of Sciences（捷克科学院天文研究所）
