Monitoring observations of SMC X-1’s excursions (MOOSE)  – II. A new excursion accompanies spin-up acceleration

Author:

Hu Chin-Ping1ORCID,Dage Kristen C23,Clarkson William I4,Brumback McKinley5,Charles Philip A6,Haggard Daryl23,Hickox Ryan C7,Mihara Tatehiro8,Bahramian Arash9ORCID,Karam Rawan23,Athukoralalage Wasundara10,Altamirano Diego6,Neilsen Joey11,Kennea Jamie12

Affiliation:

1. Department of Physics, National Changhua University of Education , Changhua 50007, Taiwan

2. Department of Physics, McGill University , 3600 University Street, Montréal, QC H3A 2T8, Canada

3. Trottier Space Institute at McGill , 3550 University Street, Montréal, QC H3A 2A7, Canada

4. Department of Natural Sciences, University of Michigan–Dearborn , 4901 Evergreen Road, Dearborn, MI 48128, USA

5. Department of Astronomy, University of Michigan , 1085 South University Avenue, Ann Arbor, MI 48109, USA

6. Physics and Astronomy, University of Southampton , Southampton, Hampshire SO17 1BJ, UK

7. Department of Physics and Astronomy, Dartmouth College , 6127 Wilder Laboratory, Hanover, NH 03755, USA

8. MAXI Team, Institute of Physical and Chemical Research (RIKEN) , 2-1, Hirosawa, Wako, Saitama 351-0198, Japan

9. International Centre for Radio Astronomy Research – Curtin University , GPO Box U1987, Perth, WA 6845, Australia

10. Department of Physics and Astronomy, Michigan State University , East Lansing, MI 48824, USA

11. Department of Physics, Villanova University , Villanova, PA 19085, USA

12. Department of Astronomy and Astrophysics, The Pennsylvania State University , University Park, PA 16802, USA

Abstract

ABSTRACTSMC X-1 is a high-mass X-ray binary showing superorbital modulation with an unstable period. Previous monitoring shows three excursion events in 1996–1998, 2005–2007, and 2014–2016. The superorbital period drifts from ≳60 to ≲40 d and then evolves back during an excursion. Here, we report a new excursion event of SMC X-1 in 2020–2021, indicating that the superorbital modulation has an unpredictable, chaotic nature. We trace the spin-period evolution and find that the spin-up rate accelerated 1 yr before the onset of this new excursion, which suggests a possible inside-out process connecting the spin-up acceleration and the superorbital excursion. This results in a deviation of the spin-period residual, similar to the behaviour of the first excursion in 1996–1998. In further analysis of the pulse profile evolution, we find that the pulsed fraction shows a long-term evolution and may be connected to the superorbital excursion. These discoveries deepen the mystery of SMC X-1 because they cannot be solely interpreted by the warped-disc model. Upcoming pointed observations and theoretical studies may improve our understanding of the detailed accretion mechanisms taking place.

Funder

Natural Sciences and Engineering Research Council of Canada

Canada Research Chairs

Publisher

Oxford University Press (OUP)

Subject

Space and Planetary Science,Astronomy and Astrophysics

Cited by 2 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

1. Spectral Energy Distributions of Southern Binary X-Ray Sources;The Astrophysical Journal Supplement Series;2023-09-01

2. Constraining the Evolution of the Unstable Accretion Disk in SMC X-1 with NICER;The Astrophysical Journal;2023-08-01

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