Localizing a Second
Repeating FRB
The Canadian Hydrogen Intensity Mapping
Experiment telescope and Fast Radio Burst
detector (CHIME/FRB) at the Dominion Ra-
dio Astrophysical Observatory in British Co-
lumbia has proven to be the most prolific
FRB-detecting machine. Since 2018, the tele-
scope's large collecting area, wide band re-
ceiver, and enormous field of view has led to
the discovery of many new repeating FRBs
(CHIME/FRB Collaboration et al., 2019a,b), in-
cluding eight in August 2019.
One of the discovered repeating sources is
FRB 180916.J0158 + 65. The CHIME/FRB Col-
laboration refined the source’s position to a
Figure 1.
The interferometric
localization of FRB
180916.J0158+65
using the EVN. Panels
a to d show the images
of the four detected
bursts. Panel e shows
the continuum radio
image of the field,
where no significant
persistent radio
counterparts are
reported. Panel f shows
the derived positions
for each of the bursts
(orange circles) and
the averaged final
position (black square),
to which all plots are
referred: α (J2000) =
01h 58m 00.75017s
(± 2.3 mas), δ (J2000)
= 65˚ 43‘ 00.3152“
(± 2.3 mas). Error
bars represent 1-σ
uncertainty.
few arcminutes in the sky. This source exhib-
its a low DM, placing it somewhere between
the Galactic halo and a redshift up to ~ 0.1.
We observed the field of FRB 180916.
J0158+65 on June 19, 2019, with the EVN,
combining data from a total of eight radio
telescopes in real time to reach unparalleled
resolution and sensitivity at 1.7 gigahertz
(GHz). In parallel, we also recorded from the
100-meter Effelsberg telescope in Bad Mün-
stereifel, Germany, high time and frequency
resolution data to directly search for single,
bright radio bursts coming from the source.
During this EVN run, we detected four bursts
from FRB 180916.J0158 + 65, with each burst
lasting for, at most, a few milliseconds. As
shown in Figure 1, the resolution reached
in this observation allowed
astronomers to pinpoint the
origin of the bursts in the sky
with an accuracy of about 3
milliarcseconds (Marcote et
al., 2020). Our team found no
persistent radio counterparts
consistent with this position,
unlike with FRB 121102 (the
first repeater). In archival im-
ages from the Sloan Digital
Sky Survey and PanSTARRs,
this position placed it at the
edge of a diffuse, seemingly
elliptical galaxy. Was this re-
peating FRB, which is in the
same kind of environment
as the non-repeating FRBs,
drastically different from
that of the first repeater?
With the GMOS imager/
spectrograph on the 8-meter
Gemini North telescope, we
observed this field between
July and September 2019
with the g and r photometric
filters, but also with long-slit
optical spectroscopy. FRB
6
GeminiFocus
January 2020