SRG/ART-XC TOO observation of the binary X-ray pulsar 1A 1118-61
ATel #17616; S. Molkov, A. Lutovinov, A. Tkachenko, I. Mereminskiy, I. Lapshov (IKI RAS, Moscow)
on 20 Jan 2026; 15:39 UT
Credential Certification: Sergei Molkov (molkov@hea.iki.rssi.ru)
Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar
Title: SRG/ART-XC TOO observation of the binary X-ray pulsar 1A 1118-61
Author: S. Molkov, A. Lutovinov, A. Tkachenko, I. Mereminskiy, I. Lapshov (IKI RAS, Moscow)
The High-mass Be/X-ray binary system 1A1118-61 is a transient source
which very rare demonstrate the Type-II outbursts, approximately once
per 17 years. New outburst had been detected by the Swift/BAT telescope
on 2026 January 17 (GCN #43435; GCN #43442; ATel #17608)
and later confirmed by MAXI/GSC (ATel #17613).
The Mikhail Pavlinsky ART-XC telescope on board the SRG observatory
started a pointed observation of 1A1118-61 on 2026-01-19T13:01:00 (UTC+0).
Using the first 70 ks of the observation we clearly detected the source with
the mean fluxes around 2.5e-9, 2.2e-9 and 2.1e-9 erg/s/cm2
(~160, 330 and 420 mCrab) in the 4-12, 12-20 and 20-30 keV energy
bands, respectively. Nevertheless the flux is highly variable on the time
scale of few hundreds seconds.
We also detected pulsations with the pulse period of 408.9(1) s and pulsed
fraction of 25 percent.
A careful spectral analysis is complicated by the increased and variable
background of charged particles caused by the powerful activity of
the Sun and will be done later.
During the next 2 days ART-XC will continue observe 1A1118-61.
We encourage further multiwavelength observations of the source.
ART-XC is X-ray telescopes on board the SRG observatory which
was launched from the Baikonur cosmodrome on 13 July 2019 by the Proton
rocket. ART-XC has been renamed 'Mikhail Pavlinsky ART-XC telescope'
in honor of its first PI, Dr. Mikhail Pavlinsky.
