INTEGRAL finds link between magnetar and an FRB-like radio source
The high-energy source SGR 1935+2154 is a highly variable magnetar
located in our Galaxy, at a distance of about 14,000 light years.
Magnetars, isolated neutron stars endowed by magnetic fields about a
thousand times more intense than those of ordinary pulsars, are known
for their sporadic emission of short, but very intense, bursts of
X/gamma radiation powered by magnetic energy.
One burst emitted by SGR 1935+2154 on 28 April 2020 was of exceptional
interest (more than thirty scientific papers have already been written
about this discovery!), because, for the first time, radio emission was
seen to accompany a magnetar burst.
Various space-borne high-energy instruments detected the 28 April burst
at X-ray and gamma-ray energies, while simultaneous bright pulses of
radio emission were independently discovered by the CHIME and STARE2
radio telescopes, located in Canada and in the US, respectively.
INTEGRAL was the first satellite to disseminate the notice of this
remarkable burst (only 5 seconds after its occurrence), thanks to the
automatic analysis carried out in real time by the INTEGRAL Burst Alert
System. The image shown, obtained with the INTEGRAL/IBIS telescope
during the burst, clearly shows that it originated from SGR 1935+2154,
and not from the nearby black hole binary GRS 1915+105. The latter was
the target of the observation but it is too faint to be detected in such
a short integration time (about 0.5 seconds).
The IBIS light curve (20-200 keV; see inset, in blue) shows that the
burst had three narrow peaks, two of which lagged by about 6 millisecond
the two pulses seen at radio wavelengths (that occurred at the times
indicated by the red curve).
The radio properties of the April 28 burst were very similar to those of
the Fast Radio Bursts (FRBs), a class of extra-galactic radio sources of
unknown origin and never observed to date at other wavelengths. Various
different models have been proposed to explain their origin, including
many that are based on magnetars. It is only through this discovery that
the first direct observational link between a magnetar and an FRB-like
radio source has been found.
Credits:
"INTEGRAL discovery of a burst with associated radio emission from the
magnetar SGR 1935+2154",
S. Mereghetti, V. Savchenko, C. Ferrigno, D. Götz, M. Rigoselli, A.
Tiengo, A. Bazzano, E. Bozzo, A. Coleiro, T. J.-L. Courvoisier, M.
Doyle, A. Goldwurm, L. Hanlon, E. Jourdain, A. von Kienlin, A.
Lutovinov, A. Martin-Carrillo, S. Molkov, L. Natalucci, F. Onori, F.
Panessa, J. Rodi, J. Rodriguez, C. Sánchez-Fernández, R. Sunyaev, P.
Ubertini
To be published in The Astrophysical Journal Letters
Preprint available at
https://arxiv.org/abs/2005.06335
