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
Authors: Xiao, Hua; Tsygankov, Sergey S.; Suleimanov, Valery F.; Mushtukov, Alexander A.; Ji, Long; Poutanen, Juri
Publisher: EDP Sciences
Publication year: 2025
Journal: Astronomy and Astrophysics
Article number: A216
Volume: 702
ISSN: 0004-6361
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202556527
Publication's open availability at the time of reporting: Open 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 address: https://research.utu.fi/converis/portal/detail/Publication/505467999
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).