Be/X-ray binaries (BeXRB) consist of a magnetized neutron star (NS) orbiting a Be star,
which expels a quasi-Keplerian circumstellar disc to its equatorial plane. During periastron
passages the NS may pass through the Be disc and accrete a fraction of the disc gas. The
accreted gas is channeled on to the NS magnetic poles by the magnetic field.
H 1145-619 is such a BeXRB system. Discovered in 1972, the system displayed frequent
outbursts between 1972 and 1997. The system was believed to be in quiescence since 1997.
However, the analysis of archival INTEGRAL/JEM-X and IBIS/ISGRI data revealed three
unnoticed X-ray outbursts in 2003, 2004, and 2005. The analysis of the INTEGRAL/OMC light
curve of the system also showed long-term optical variability over this period and more
significantly from 2010 to 2017. Alfonso-Garzón et al. (2017)
compiled the available observations of the system in various energy ranges, over the
last ~40 years. The optical photometric and spectroscopic observations display variability,
suggesting an enhancement of the circumstellar disc during the last years. This disc
enhancement provided the material necessary to fuel the renewed X-ray activity observed
since 2015 by the Neil Gehrels Swift Observatory and MAXI onboard the ISS.
The optical light curve from 1973 to 2017 is shown at the top of the picture (red points
are from the INTEGRAL/OMC). The X-ray outbursts are indicated with blue dark arrows with
lengths proportional to their fluxes. The dashed gray lines mark the periastron passages.
Below the light curve, the animation shows an artist impression of the May 2003 outburst.
The green and blue images to the right correspond to JEM-X (3-10 keV) and IBIS/ISGRI
(20-35 keV) data respectively. The persistent source at North-West is the close pulsar
1E 1145.1-6141; the transient source at South-East is H 1145-619.
Combining Swift/XRT data from the September 2015 outburst, with INTEGRAL data from the
June 2003 outburst, Alfonso-Garzón et al. (2017) modelled the X-ray spectrum of
the system. The best fit to this spectrum was obtained with an absorbed cut-off power-law
model with folding energy of E_fold = 17 (+3,-2) keV and a photon index of Γ = 0.86 ± 0.05.
Animation credits: David Cabezas (CESAR, ESA/ESAC)
Reference:
"Long-term optical and X-ray variability of the Be/X-ray binary H 1145-619: Discovery of an ongoing retrograde density wave",
J. Alfonso-Garzón et al.
http://adsabs.harvard.edu/abs/2017A%26A...607A..52A
2017 A&A, 607, 52
