SXP 31.0 -- the 2025 near-Eddington double X-ray outburst after 26 years of quiescence
SXP 31.0 -- the 2025 near-Eddington double X-ray outburst after 26 years of quiescence
SXP 31.0 is an X-ray source in the Small Magellanic Cloud that was first identified as a Be X-ray Binary (BeXRB) system
when it went into X-ray outbusrst in 1998. It is now known to consist of an OBe main sequence star and a neutron star with
a spin period of 31 s. In 2025 a new X-ray outburst phase began with the source exhibiting a luminosities approaching the
Eddington limit of 10 38 erg s −1 . Unusually, H α images show it has a surrounding halo whose nature has not been clear. In
this paper, we report new observations of this halo, including the first multifibre Integrated Flux Unit observations, which
identify this emission as probably a coincidental H ii region. The X-ray, UV, and optical data cover a period of ∼200 d and
reveal that the source underwent two bright, back-to-back, Type II outbursts in 2025 –a rare occurrence for any BeXRB
system.
astro-ph.SR
Coe, M.J.
04dfb23b-1456-46a3-9242-5cee983471d5
Gaudin, T.M.
a57269d7-0d78-4cd2-939d-9e98e0e250aa
Monageng, I.M.
c7195666-944f-4be6-93be-c4b9a5426bb4
Kennea, J.A.
8a2485ff-bd59-4dd8-b6e3-d02e86bbc344
Buckley, D.A.H.
35279f22-62d6-4626-b262-df2754ca734b
Udalski, A.
d6d4956e-6852-4146-aaa7-2ef17bd1944c
Evans, P.A.
fd169e4e-2308-4d9b-94b6-59f4c4e45312
Chattopadhyay, S.
e262c64f-14a4-40a7-87fd-275d4d2d19a8
25 February 2026
Coe, M.J.
04dfb23b-1456-46a3-9242-5cee983471d5
Gaudin, T.M.
a57269d7-0d78-4cd2-939d-9e98e0e250aa
Monageng, I.M.
c7195666-944f-4be6-93be-c4b9a5426bb4
Kennea, J.A.
8a2485ff-bd59-4dd8-b6e3-d02e86bbc344
Buckley, D.A.H.
35279f22-62d6-4626-b262-df2754ca734b
Udalski, A.
d6d4956e-6852-4146-aaa7-2ef17bd1944c
Evans, P.A.
fd169e4e-2308-4d9b-94b6-59f4c4e45312
Chattopadhyay, S.
e262c64f-14a4-40a7-87fd-275d4d2d19a8
Coe, M.J., Gaudin, T.M., Monageng, I.M., Kennea, J.A., Buckley, D.A.H., Udalski, A., Evans, P.A. and Chattopadhyay, S.
(2026)
SXP 31.0 -- the 2025 near-Eddington double X-ray outburst after 26 years of quiescence.
Monthly Notices of the Royal Astronomical Society, 546 (4), [stag265].
(doi:10.1093/mnras/stag265).
Abstract
SXP 31.0 is an X-ray source in the Small Magellanic Cloud that was first identified as a Be X-ray Binary (BeXRB) system
when it went into X-ray outbusrst in 1998. It is now known to consist of an OBe main sequence star and a neutron star with
a spin period of 31 s. In 2025 a new X-ray outburst phase began with the source exhibiting a luminosities approaching the
Eddington limit of 10 38 erg s −1 . Unusually, H α images show it has a surrounding halo whose nature has not been clear. In
this paper, we report new observations of this halo, including the first multifibre Integrated Flux Unit observations, which
identify this emission as probably a coincidental H ii region. The X-ray, UV, and optical data cover a period of ∼200 d and
reveal that the source underwent two bright, back-to-back, Type II outbursts in 2025 –a rare occurrence for any BeXRB
system.
Text
2602.07459v1
- Author's Original
Text
stag265
- Version of Record
More information
Accepted/In Press date: 6 February 2026
e-pub ahead of print date: 10 February 2026
Published date: 25 February 2026
Additional Information:
Accepted for publication in MNRAS
Keywords:
astro-ph.SR
Identifiers
Local EPrints ID: 511760
URI: http://eprints.soton.ac.uk/id/eprint/511760
ISSN: 1365-2966
PURE UUID: 3f2c1f58-a8d1-416b-ab3b-337c390b65a2
Catalogue record
Date deposited: 01 Jun 2026 16:51
Last modified: 02 Jun 2026 01:32
Export record
Altmetrics
Contributors
Author:
T.M. Gaudin
Author:
I.M. Monageng
Author:
J.A. Kennea
Author:
D.A.H. Buckley
Author:
A. Udalski
Author:
P.A. Evans
Author:
S. Chattopadhyay
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics
