Issue |
A&A
Volume 667, November 2022
|
|
---|---|---|
Article Number | L7 | |
Number of page(s) | 6 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202244643 | |
Published online | 11 November 2022 |
Letter to the Editor
A puzzling 2-hour X-ray periodicity in the 1.5-hour orbital period black widow PSR J1311−3430
1
INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano, Via A. Corti 12, 20133 Milano, Italy
e-mail: andrea.deluca@inaf.it
2
INFN, Sezione di Pavia, Via A. Bassi 6, 27100 Pavia, Italy
3
Janusz Gil Institute of Astronomy, University of Zielona Góra, ul Szafrana 2, 65-265 Zielona Góra, Poland
Received:
30
July
2022
Accepted:
15
October
2022
Time-domain analysis of an archival XMM-Newton observation unveiled a very unusual variability pattern in the soft X-ray emission of PSR J1311−3430, a black widow millisecond pulsar in a tight binary (PB = 93.8 min) with a very low-mass (M ∼ 0.01 M⊙) He companion star, known to show flaring emission in the optical and in the X-rays. A series of six pulses with a regular recurrence time of ∼124 min is apparent in the 0.2−10 keV light curve of the system, also featuring an initial, bright flare and a quiescent phase lasting several hours. The X-ray spectrum does not change when the pulses are seen and it is consistent with a power law with photon index Γ ∼ 1.5, also describing the quiescent emission. The peak luminosity of the pulses is of several 1032 erg s−1. Simultaneous observations in the U band with the Optical Monitor onboard XMM and in the g′ band from the Las Cumbres Observatory do not show any apparent counterpart of the pulses and only display the well-known orbital modulation of the system. We consider different hypotheses to explain the recurrent pulses: we investigate their possible analogy with other phenomena already observed in this pulsar and in similar systems and we also study possible explanations related to the interaction of the energetic pulsar wind with intra-binary material, but we found none of these pictures to be convincing. We identify simultaneous X-ray observations and optical spectroscopy as a possible way to constrain the nature of the phenomenon.
Key words: X-rays: stars / pulsars: individual: PSR J1311−3430 / binaries: close
© A. De Luca et al. 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe-to-Open model. Subscribe to A&A to support open access publication.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.