A magnetar-powered X-ray transient as the aftermath of a binary neutron-star merger

Y. Q. Xue, X. C. Zheng, Y. Li, William Nielsen Brandt, B. Zhang, B. Luo, B. B. Zhang, F. E. Bauer, H. Sun, B. D. Lehmer, X. F. Wu, G. Yang, X. Kong, J. Y. Li, M. Y. Sun, J. X. Wang, F. Vito

Research output: Contribution to journalLetter

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Abstract

Mergers of neutron stars are known to be associated with short γ-ray bursts 1–4 . 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 5–8 (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 9,10 . 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 11,12 . 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 13 . 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 13 . Here we report a second X-ray transient, CDF-S XT2, that is associated with a galaxy at redshift z = 0.738 (ref. 14 ). 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 15,16 . 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.

Original languageEnglish (US)
Pages (from-to)198-201
Number of pages4
JournalNature
Volume568
Issue number7751
DOIs
StatePublished - Apr 11 2019

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Galaxies
Neutrons
X-Rays
Magnetic Fields
Light
Pressure

All Science Journal Classification (ASJC) codes

  • General

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Xue, Y. Q., Zheng, X. C., Li, Y., Brandt, W. N., Zhang, B., Luo, B., ... Vito, F. (2019). A magnetar-powered X-ray transient as the aftermath of a binary neutron-star merger. Nature, 568(7751), 198-201. https://doi.org/10.1038/s41586-019-1079-5
Xue, Y. Q. ; Zheng, X. C. ; Li, Y. ; Brandt, William Nielsen ; Zhang, B. ; Luo, B. ; Zhang, B. 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. / A magnetar-powered X-ray transient as the aftermath of a binary neutron-star merger. In: Nature. 2019 ; Vol. 568, No. 7751. pp. 198-201.
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abstract = "Mergers of neutron stars are known to be associated with short γ-ray bursts 1–4 . 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 5–8 (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 9,10 . 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 11,12 . 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 13 . 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 13 . Here we report a second X-ray transient, CDF-S XT2, that is associated with a galaxy at redshift z = 0.738 (ref. 14 ). 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 15,16 . 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.",
author = "Xue, {Y. Q.} and Zheng, {X. C.} and Y. Li and Brandt, {William Nielsen} and B. Zhang and B. Luo and Zhang, {B. B.} and Bauer, {F. E.} and H. Sun and Lehmer, {B. D.} and Wu, {X. F.} and G. Yang and X. Kong and Li, {J. Y.} and Sun, {M. Y.} and Wang, {J. X.} and F. Vito",
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Xue, YQ, Zheng, XC, Li, Y, Brandt, WN, Zhang, B, Luo, B, Zhang, BB, Bauer, FE, Sun, H, Lehmer, BD, Wu, XF, Yang, G, Kong, X, Li, JY, Sun, MY, Wang, JX & Vito, F 2019, 'A magnetar-powered X-ray transient as the aftermath of a binary neutron-star merger', Nature, vol. 568, no. 7751, pp. 198-201. https://doi.org/10.1038/s41586-019-1079-5

A magnetar-powered X-ray transient as the aftermath of a binary neutron-star merger. / Xue, Y. Q.; Zheng, X. C.; Li, Y.; Brandt, William Nielsen; Zhang, B.; Luo, B.; Zhang, B. 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.

In: Nature, Vol. 568, No. 7751, 11.04.2019, p. 198-201.

Research output: Contribution to journalLetter

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AU - Xue, Y. Q.

AU - Zheng, X. C.

AU - Li, Y.

AU - Brandt, William Nielsen

AU - Zhang, B.

AU - Luo, B.

AU - Zhang, B. B.

AU - Bauer, F. E.

AU - Sun, H.

AU - Lehmer, B. D.

AU - Wu, X. F.

AU - Yang, G.

AU - Kong, X.

AU - Li, J. Y.

AU - Sun, M. Y.

AU - Wang, J. X.

AU - Vito, F.

PY - 2019/4/11

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N2 - Mergers of neutron stars are known to be associated with short γ-ray bursts 1–4 . 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 5–8 (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 9,10 . 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 11,12 . 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 13 . 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 13 . Here we report a second X-ray transient, CDF-S XT2, that is associated with a galaxy at redshift z = 0.738 (ref. 14 ). 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 15,16 . 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.

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