Sky & Telescope - September 2021 - 8

NEWS NOTES
The CHIME radio telescope consists of four
massive cylindrical radio antennas roughly the
size and shape of snowboarding half-pipes.
Astronomers know at least some
FRBs originate from the burnt-out
stellar cinders known as magnetars
(S&T: Sept. 2020, p. 10). These neutron
stars generate strong magnetic fields
that release energy when they tangle or
snap. But astronomers don't yet understand
exactly what makes FRBs, or why
some sources repeat and others don't.
The CHIME data show that repeating
FAST RADIO BURSTS
Number of Fleeting
Radio Bursts Triples
THE POWERFUL FLASHES of fast radio
bursts (FRBs) are so fleeting, they're
hard to find. Astronomers had detected
only about 140 of them since 2007. But
the first data release from the Canadian
Hydrogen Intensity Mapping Experiment
(CHIME), presented June 9th at
the virtual meeting of the American
Astronomical Society, more than tripled
that number with 535 FRBs, including
61 bursts from 18 previously reported
repeating sources.
After CHIME scans the whole sky
visible from its location in British
Columbia every night, astronomers use
digital signal-processing to " focus " on
individual signals. Yet the telescope
only sees the tip of the iceberg: Based on
the first year of data, collected between
2018 and 2019, the CHIME/FRB Collaboration
calculates that some 800
bright bursts occur every day.
The radio flashes CHIME does see
are spread out on the sky, which means
that, as astronomers had already suspected,
the sources of these mysterious
flashes aren't concentrated in the Milky
Way. But that spread isn't completely
uniform. The team finds that FRBs correlate
with galaxies between 3½ billion
and 5 billion light-years away.
An artist's depiction shows a hiccup in a
magnetar's strong magnetic field.
EXOPLANETS
Astronomers Challenge Barnard's Star Planet Claim
IN 2018, A TEAM OF ASTRONOMERS
discovered a super-Earth about 6 lightyears
away, hidden in the meager light
of its red sun, Barnard's star. Now, a
new study to appear in the Astronomical
Journal challenges that claim.
In the original study, Ignasi Ribas
(Institute of Space Sciences, Spain)
and colleagues analyzed two decades of
radial velocity measurements, which
showed the star's slight motions toward
and away from us. Within those data,
8
SEPTEMBER 2021 * SKY & TELESCOPE
Ribas and colleagues saw the repeated
signal of a planet's gravitational backand-forth
pull as it circled its star every
233 days (S&T: Mar. 2019, p. 9).
But in a new analysis, which includes
observations from the recently minted
Habitable-zone Planet Finder on the
Hobby-Eberly Telescope in Texas, graduate
student Jack Lubin (University of
California, Irvine) and colleagues concluded
that stellar activity might have
masqueraded as a planetary signal.
bursts last slightly longer and emit more
focused radio frequencies than single
bursts. That could mean they're two
distinct populations. Or, as CHIME/
FRB team member Ziggy Pleunis
(McGill University) suggests, they could
represent two extremes of a spectrum.
For example, if narrow bursts are rarer,
then the narrowest bursts would appear
to be one-off events.
The CHIME team is excited not only
about the sources themselves but what
can be done with them. " We are now
in the era of using FRBs as cosmological
probes, " says team member Alex Josephy
(also at McGill).
" The distortion of each signal carries
a record of the structure it traveled
through, " explains Kiyoshi Masui
(MIT). Ultimately, astronomers will be
able to map out gas across the universe,
showing the evolution of large-scale
cosmic structures.
¢MONICA YOUNG
The researchers analyzed 856 days'
worth of data from the HPF spectrograph,
but they didn't find the planet's
signal. They also re-analyzed the data
Ribas's team had published and showed
that the signal had strengthened and
weakened over time - something a
planet's signal wouldn't do.
In fact, the researchers found that
almost all of the signal was in 211 data
points collected between 2011 to 2013.
During this same time period, Lubin
says, his team also found a chemical
signature associated with stellar activity
that also varied on a 233-day period.
CHIME RADIO TELESCOPE: ANDRE RENARD (UNIVERSITY OF TORONTO);
CHIME COLLABORATION; MAGNETAR FLARE: NASA'S GODDARD SPACE
FLIGHT CENTER / CHRIS SMITH / USRA / GESTAR
Sky & Telescope - September 2021

Table of Contents for the Digital Edition of Sky & Telescope - September 2021
