Compact objects at stellar scale, generally including white dwarfs, neutron stars and stellar-mass black holes, are the final remnants of stellar evolution. Compact objects provide the most extreme physical conditions in the Universe, e.g., high density, strong gravity, and strong magnetic field. They are associated with some of the most energetic physical processes, such as relativistic jets and gamma-ray bursts. Compact object study is one of the most important approaches to understand the life cycle of stars, the related matter and energy exchange, and the effects on their environment and beyond. Meanwhile, compact objects provide the ideal laboratory for fundamental physics on the properties of matter under extreme physical conditions.

The Astronomy Department at Xiamen University has been carrying out diverse and fruitful studies on compact objects, on both the theoretical and observational regimes. Our faculty members have a long and rich history of theoretical research on accretion onto compact objects, which is one of the most energy-efficient processes in the Universe. Luminous radiation originating from the accreted gas reveals the properties of the compact objects, especially when they are not directly observable. The associated outflow affects the environment far beyond the scale of the compact objects. Gamma-ray bursts are the most violent and luminous explosions in the Universe. Our faculty members have been working actively on the theories of gamma-ray bursts, as well as of other transients such as fast radio bursts and supernovae. Another focus of our theoretical research is the fundamental properties of dense matter, such as the neutron star equation of state, and neutrino oscillation in dense matter.

Studies on compact objects constitute a major part of the sub-discipline high energy astrophysics, for which the X-ray and gamma-ray facilities have been the main observational tools. Besides the expertise on X-rays and gamma-rays, our faculty members are embracing a multiwavelength, multimessenger approach. We are combining wide-field optical/infrared spectroscopic and photometric surveys (such as LAMOST and ASAS-SN), as well as astrometry databases, to search for the largely unexplored population of stellar-mass black holes. Time-resolved optical spectroscopy and photometry are employed to characterize the fundamental properties, especially the mass, of compact objects. We have also started to utilize gravitational waves and neutrinos as the new messengers to comprehend the physical properties and processes of compact objects. Our Department has been actively participating in major observational facilities, such as LAMOST, Insight/HXMT, FAST, CSST, eXTP, EP, HUBs, TMT, SKA, and JUNO.