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# Orbital Decay in M82 X-2

Abstract : M82 X-2 is the first pulsating ultraluminous X-ray source discovered. The luminosity of these extreme pulsars, if isotropic, implies an extreme mass transfer rate. An alternative is to assume a much lower mass transfer rate, but with an apparent luminosity boosted by geometrical beaming. Only an independent measurement of the mass transfer rate can help discriminate between these two scenarios. In this paper, we follow the orbit of the neutron star for 7 yr, measure the decay of the orbit ( ${\dot{P}}_{\mathrm{orb}}/{P}_{\mathrm{orb}}\approx -8\cdot {10}^{-6}\,{\mathrm{yr}}^{-1}$ ), and argue that this orbital decay is driven by extreme mass transfer of more than 150 times the mass transfer limit set by the Eddington luminosity. If this is true, the mass available to the accretor is more than enough to justify its luminosity, with no need for beaming. This also strongly favors models where the accretor is a highly magnetized neutron star.
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https://hal-insu.archives-ouvertes.fr/insu-03867383
Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Wednesday, November 23, 2022 - 1:29:14 PM
Last modification on : Thursday, November 24, 2022 - 4:04:55 AM

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Bachetti_2022_ApJ_937_125.pdf
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### Licence

Distributed under a Creative Commons Attribution 4.0 International License

### Citation

Matteo Bachetti, Marianne Heida, Thomas Maccarone, Daniela Huppenkothen, Gian Luca Israel, et al.. Orbital Decay in M82 X-2. The Astrophysical Journal, 2022, 937, ⟨10.3847/1538-4357/ac8d67⟩. ⟨insu-03867383⟩

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