Revisiting Stellar equatorial rotational velocities with Gaia DR3 line broadening -- the dependence on temperature, mass and age
Authors:
Amitay Sussholz,
Tsevi Mazeh,
Simchon Faigler
Abstract:
We used more than $10^5$ Gaia DR3 line broadening vbroad measurements to examine stellar rotation as a function of stellar temperature, mass and age. The large sample clearly displays the Kraft break at $\sim 6{,}500$\,K, or mass of $\sim1.3\,M_{\odot}$-while vbroad are small, on the order of $10$-$20$ km/s, for stars cooler than the Kraft break, they sharply rise above the break, reaching up…
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We used more than $10^5$ Gaia DR3 line broadening vbroad measurements to examine stellar rotation as a function of stellar temperature, mass and age. The large sample clearly displays the Kraft break at $\sim 6{,}500$\,K, or mass of $\sim1.3\,M_{\odot}$-while vbroad are small, on the order of $10$-$20$ km/s, for stars cooler than the Kraft break, they sharply rise above the break, reaching up $\sim100$ km/s with temperature of $7{,}000$ K. To follow the stellar rotation as a function of age, we consider vbroad as a function of scaled age-stellar age divided by the relevant Terminal Age Main Sequence (MS), for four narrow mass bins. We find that stellar rotation deceleration is slow during the MS phase and fast afterwards for stars hotter than the break, whereas deceleration rate is relatively high and does not vary much for the cool stars. Our findings are consistent with the theory that stellar rotation slowing is due to magnetic breaking, emanating from magnetic fields that are anchored to the stellar convective envelopes. Therefore, deceleration is high in cool stars, but in hot stars only after they leave the MS and develop convective outer layers
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Submitted 27 January, 2026;
originally announced January 2026.
Probable Dormant Neutron Star in a Short-Period Binary System
Authors:
Tsevi Mazeh,
Simchon Faigler,
Dolev Bashi,
Sahar Shahaf,
Niv Davidson,
Matthew Green,
Roy Gomel,
Dan Maoz,
Amitay Sussholz,
Subo Dong,
Haotong Zhang,
Jifeng Liu,
Song Wang,
Ali Luo,
Zheng Zheng,
Na'ama Hallakoun,
Volker Perdelwitz,
David W. Latham,
Ignasi Ribas,
David Baroch,
Juan Carlos Morales,
Evangelos Nagel,
Nuno C. Santos,
David R. Ciardi,
Jessie L. Christiansen
, et al. (2 additional authors not shown)
Abstract:
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-day Keplerian circular orbit, with no indication of light from a secondary component. Optical and UV photometry reveal ellipsoidal varia…
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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-day Keplerian circular orbit, with no indication of light from a secondary component. Optical and UV photometry reveal ellipsoidal variations 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 $1.1$--$2.1\,M_{\odot}$ at $3σ$ confidence, with the median of the mass distribution at $1.4\,M_{\odot}$, 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.
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Submitted 3 October, 2022; v1 submitted 22 June, 2022;
originally announced June 2022.