A Magnetar-Powered X-Ray Transient as the Aftermath of a Binary Neutron-Star Merger
Document Type
Letter to the Editor
Publication Date
4-10-2019
Publication Title
Nature
Volume
568
First page number:
198
Last page number:
201
Abstract
Mergers of neutron stars are known to be associated with short γ-ray bursts. If the neutron-star equation of state is sufficiently stiff (that is, the pressure increases sharply as the density increases), at least some such mergers will leave behind a supramassive or even a stable neutron star that spins rapidly with a strong magnetic field (that is, a magnetar). Such a magnetar signature may have been observed in the form of the X-ray plateau that follows up to half of observed short γ-ray bursts. However, it has been expected that some X-ray transients powered by binary neutron-star mergers may not be associated with a short γ-ray burst. A fast X-ray transient (CDF-S XT1) was recently found to be associated with a faint host galaxy, the redshift of which is unknown. Its X-ray and host-galaxy properties allow several possible explanations including a short γ-ray burst seen off-axis, a low-luminosity γ-ray burst at high redshift, or a tidal disruption event involving an intermediate-mass black hole and a white dwarf. Here we report a second X-ray transient, CDF-S XT2, that is associated with a galaxy at redshift z = 0.738 (ref.). The measured light curve is fully consistent with the X-ray transient being powered by a millisecond magnetar. More intriguingly, CDF-S XT2 lies in the outskirts of its star-forming host galaxy with a moderate offset from the galaxy centre, as short γ-ray bursts often do. The estimated event-rate density of similar X-ray transients, when corrected to the local value, is consistent with the event-rate density of binary neutron-star mergers that is robustly inferred from the detection of the gravitational-wave event GW170817.
Keywords
Compact astrophysical objects; High-energy astrophysics; Transient astrophysical phenomena
Disciplines
Stars, Interstellar Medium and the Galaxy
Language
English
Repository Citation
Xue, Y.,
Zheng, X.,
Li, Y.,
Brandt, W. N.,
Zhang, B.,
Luo, B.,
Zhang, B.,
Bauer, F. E.,
Sun, H.,
Lehmer, B. D.,
Wu, X. F.,
Yang, G.,
Kong, X.,
Li, J. Y.,
Sun, M. Y.,
Wang, J. X.,
Vito, F.
(2019).
A Magnetar-Powered X-Ray Transient as the Aftermath of a Binary Neutron-Star Merger.
Nature, 568
198-201.
http://dx.doi.org/10.1038/s41586-019-1079-5