Chinese astronomers from Peking University and the National Astronomical Observatories have discovered a peculiar neutron star candidate in a binary system, located 385 light years away from Earth. The object, which is a dark companion to an old-age star, has a mass of only 0.98 times that of the Sun, making it the nearest and lightest neutron star candidate ever known if confirmed. The discovery was reported based on observations from China’s Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and the Nanshan 1-meter Wide-field Telescope (NOWT) in northwest China’s Xinjiang Uygur Autonomous Region.
The neutron star candidate is presumed to be an X-ray-dim isolated neutron star (XDINS) in binary, a peculiar object with barely-detected radio signals. Only seven such objects have been discovered to date, and they are nicknamed the Magnificent Seven, located 391 to 1,630 light years away from Earth. Neutron stars were previously believed to have taken shape through the core-collapse supernovae, but they tend to be above 1.17 times solar mass.
LAMOST’s spectral data also hinted at the presence of a small accretion disk around the neutron star candidate and/or a level of accretion disk activity. The new findings suggested that the radio-quiet, XDINS-like compact object possibly was born in an alternative channel, such as the collapse of a white dwarf after it accretes, according to the researchers. This discovery could provide insight into the formation of neutron stars and the evolution of binary star systems.