Evolution of the spin, spectrum and super-orbital period of the ultraluminous X-ray pulsar M51 ULX7
| Autor: | Murray Brightman, Matteo Bachetti, Hannah Earnshaw, Felix Fürst, Marianne Heida, Gian Luca Israel, Sean Pike, Daniel Stern, Dominic J Walton |
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| Přispěvatelé: | ITA, USA, GBR, DEU, ESP |
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
High Energy Astrophysical Phenomena (astro-ph.HE)
Space and Planetary Science Astrophysics::High Energy Astrophysical Phenomena FOS: Physical sciences Astronomy and Astrophysics Astrophysics::Earth and Planetary Astrophysics Astrophysics - High Energy Astrophysical Phenomena Astrophysics::Galaxy Astrophysics |
| Popis: | M51 ULX7 is among a small group of known ultraluminous X-ray pulsars (ULXP). The neutron star powering the source has a spin period of 2.8s, orbits its companion star with a period of 2 days, and a super-orbital period of 38 days is evident in its X-ray lightcurve. Here we present NuSTAR and XMM-Newton data on the source from 2019 obtained when the source was near its peak brightness. We detect the pulsations, having spun up at a rate of 3$\pm0.5\times10^{-10}$ s s$^{-1}$ since they were previously detected in 2018. The data also provide the first high-quality broadband spectrum of the source. We find it to be very similar to that of other ULXPs, with two disk-like components, and a high energy tail. When combined with XMM-Newton data obtained in 2018, we explore the evolution of the spectral components with super-orbital phase, finding that the luminosity of the hotter component drives the super-orbital flux modulation. The inclination the disk components appear to change with phase, which may support the idea that these super-orbital periods are caused by disk precession. We also reexamine the super-orbital period with 3 years of Swift/XRT monitoring, finding that the period is variable, increasing from 38.2$\pm0.5$ days in 2018--2019 to 44.2$\pm0.9$ days in 2020--2021, which rules out alternative explanations for the super-orbital period. Accepted for publication in ApJ |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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