We explore an alternative explanation for the low-mass ultra-compact star in the supernova remnant HESS~J1731-347 using a model-agnostic approach to construct hybrid equations of state. The hadronic part of the hybrid equation of state is constructed using a generalized piecewise polytropic scheme, while the quark phase is described by the generic constant speed of sound model. We assume an abrupt first-order hadron-quark phase transition with a slow conversion speed between phases. Our equations of state align with modern Chiral Effective Field Theory calculations near nuclear saturation density and are consistent with perturbative Quantum Chromodynamics calculations at high densities. Using this theoretical framework, we derive a wide range of hybrid equations of state capable of explaining the light compact object in HESS~J1731-347 in a model-independent manner, without fine-tuning. These equations of state are also consistent with modern astronomical constraints from high-mass pulsar timing, NICER observations, and multimessenger astronomy involving gravitational waves. Our results support the hypothesis that the compact object in HESS~J1731-347 could plausibly be a slow stable hybrid star.
Classification of $g$-modes for neutron stars with a strong transition: Novel universal relation including slow stable hybrid stars
Universidad Nacional de La Plata（拉普拉塔国立大学）；CONICET（阿根廷国家科学研究委员会）；The Brazilian Center for Research in Physics (CBPF)（巴西物理研究中心）；Universidad Tecnológica del Perú（秘鲁理工大学）
CoportSL: A Contribution-constrained Hybrid Slow-light Framework for Time-dependent Polarized GRMHD Imaging
School of Physics and Astronomy, Beijing Normal University（北京师范大学物理与天文学院）；School of Physics, Peking University（北京大学物理学院）；Key Laboratory of Multiscale Spin Physics (Beijing Normal University), Ministry of Education（教育部多尺度自旋物理重点实验室（北京师范大学））；School of Physical Science and Technology, Ningbo University（宁波大学物理科学与技术学院）
Self-bound hybrid stars with strong phase transitions can relieve major compact star observation tensions
Tongji University（同济大学）；The Hong Kong University of Science and Technology（香港科技大学）；Centro Brasileiro de Pesquisas Físicas（巴西物理研究中心）；Peking University（北京大学）
Quasiradial oscillations of rotating hybrid neutron stars
Central China Normal University（华中师范大学）；Hubei University of Education（湖北教育学院）；China University of Geosciences（中国地质大学）；Huazhong University of Science and Technology（华中科技大学）；INFN Sezione di Catania（意大利国家核物理研究所卡塔尼亚分部）；Universitá di Catania（卡塔尼亚大学）
