A1 Refereed original research article in a scientific journal

Propeller effect in action: Unveiling quenched accretion in the transient X-ray pulsar 4U 0115+63




AuthorsXiao, Hua; Tsygankov, Sergey S.; Suleimanov, Valery F.; Mushtukov, Alexander A.; Ji, Long; Poutanen, Juri

PublisherEDP Sciences

Publication year2025

Journal: Astronomy and Astrophysics

Article numberA216

Volume702

ISSN0004-6361

eISSN1432-0746

DOIhttps://doi.org/10.1051/0004-6361/202556527

Publication's open availability at the time of reportingOpen Access

Publication channel's open availability Open Access publication channel

Web address https://doi.org/10.1051/0004-6361/202556527

Self-archived copy’s web addresshttps://research.utu.fi/converis/portal/detail/Publication/505467999


Abstract

The Be/X-ray pulsar 4U 0115+63 underwent a type II outburst in 2023. After the outburst, similar to the outbursts in 2015 and 2017, the source decayed into a quiescent state. Two out of three XMM-Newton observations conducted after the 2023 outburst confirmed the source to be in a low-luminosity state at a level of LX ∼ 1033 erg s−1. X-ray pulsations were detected at ≈0.277 Hz in both observations with a pulsed fraction exceeding 50%. The power density spectra show no significant low-frequency red noise in either observation, suggesting that the radiation is not driven by accretion. The energy spectra in this state can be described by a single blackbody component, with an emitting area smaller than the typical size of the polar caps during the accretion phase. Based on the timing and spectral properties, we suggest that the propeller effect is active during the quiescent state, resulting in a total quenching of accretion. We discuss possible mechanisms for the generation of pulsations in this regime and consider the scenario of neutron star crust cooling.


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Funding information in the publication
HX acknowledges support from the China Scholarship Council (CSC).


Last updated on 2025-25-11 at 10:06