TY - JOUR
T1 - Probable dormant neutron star in a short-period binary system
AU - Mazeh, Tsevi
AU - Faigler, Simchon
AU - Bashi, Dolev
AU - Shahaf, Sahar
AU - Davidson, Niv
AU - Green, Matthew
AU - Gomel, Roy
AU - Maoz, Dan
AU - Sussholz, Amitay
AU - Dong, Subo
AU - Zhang, Haotong
AU - Liu, Jifeng
AU - Wang, Song
AU - Luo, Ali
AU - Zheng, Zheng
AU - Hallakoun, Na'ama
AU - Perdelwitz, Volker
AU - Latham, David W.
AU - Ribas, Ignasi
AU - Baroch, David
AU - Morales, Juan Carlos
AU - Nagel, Evangelos
AU - Santos, Nuno C.
AU - Ciardi, David R.
AU - Christiansen, Jessie L.
AU - Lund, Michael B.
AU - Winn, Joshua N.
N1 - Publisher Copyright:
© 2022 The Author(s).
PY - 2022/12/1
Y1 - 2022/12/1
N2 - We have identified 2XMM J125556.57+565846.4, at a distance of 600 pc, as a binary system consisting of a normal star and a probable dormant neutron star. Optical spectra exhibit a slightly evolved F-type single star, displaying periodic Doppler shifts with a 2.76-d Keplerian circular orbit, with no indication of light from a secondary component. Optical and UV photometry reveal ellipsoidal modulation with half the orbital period, due to the tidal deformation of the F-star. The mass of the unseen companion is constrained to the range of 1.1-2.1, M⊙ at 3σ confidence, with the median of the mass distribution at 1.4, M⊙, the typical mass of known neutron stars. A main-sequence star cannot masquerade as the dark companion. The distribution of possible companion masses still allows for the possibility of a very massive white dwarf. The companion itself could also be a close pair consisting of a white dwarf and an M star, or two white dwarfs, although the binary evolution that would lead to such a close triple system is unlikely. Similar ambiguities regarding the certain identification of a dormant neutron star are bound to affect most future discoveries of this type of non-interacting system. If the system indeed contains a dormant neutron star, it will become, in the future, a bright X-ray source and afterwards might even host a millisecond pulsar.
AB - We have identified 2XMM J125556.57+565846.4, at a distance of 600 pc, as a binary system consisting of a normal star and a probable dormant neutron star. Optical spectra exhibit a slightly evolved F-type single star, displaying periodic Doppler shifts with a 2.76-d Keplerian circular orbit, with no indication of light from a secondary component. Optical and UV photometry reveal ellipsoidal modulation with half the orbital period, due to the tidal deformation of the F-star. The mass of the unseen companion is constrained to the range of 1.1-2.1, M⊙ at 3σ confidence, with the median of the mass distribution at 1.4, M⊙, the typical mass of known neutron stars. A main-sequence star cannot masquerade as the dark companion. The distribution of possible companion masses still allows for the possibility of a very massive white dwarf. The companion itself could also be a close pair consisting of a white dwarf and an M star, or two white dwarfs, although the binary evolution that would lead to such a close triple system is unlikely. Similar ambiguities regarding the certain identification of a dormant neutron star are bound to affect most future discoveries of this type of non-interacting system. If the system indeed contains a dormant neutron star, it will become, in the future, a bright X-ray source and afterwards might even host a millisecond pulsar.
KW - binaries: close
KW - binaries: spectroscopic
KW - stars: neutron
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U2 - 10.1093/mnras/stac2853
DO - 10.1093/mnras/stac2853
M3 - Article
AN - SCOPUS:85143672711
SN - 0035-8711
VL - 517
SP - 4005
EP - 4021
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -