April 2017
Figure 1.
The arrival of the
Lorimer burst heralded
a new era in radio
astrophysics. The
dynamic spectrum of
the pulse is shown with
frequency along the
y-axis and arrival time
along the x-axis. The
grayscale depicts the
1-bit digitized intensity.
Two thin white lines
are drawn along the
theoretical dispersion
relation to guide the
eye. The inset shows
the total intensity
profile as a function of
time after correcting
for dispersion. Figure
adapted from Lorimer
et al., 2007.
Shriharsh P. Tendulkar, on behalf of the FRB 121102 collaboration
The Host Galaxy of the Repeating
Fast Radio Burst FRB 121102
Fast radio bursts (FRBs) are a recent astronomical mystery consisting
of short, yet extremely bright, pulsar-like bursts of radio waves that
seem to traverse cosmological distances. Although they occur at a
stunning rate of 1,000 per day in the entire sky, we know little about
their origins, generation mechanisms, and, until recently, even their
distances. Using the combined forces of the Karl G. Jansky Very Large
Array in New Mexico and the Gemini North telescope in Hawai‘i, we
have localized and identified — for the first time — the host galaxy of
an FRB. Surprisingly, the host galaxy is a low-metallicity, star-forming,
dwarf galaxy ~1 billion parsecs distant, which hints at possible
similarities of this FRB host to those of superluminous supernovae and
long-duration gamma-ray bursts.
Almost exactly ten years ago, Duncan Lorimer and his team
at West Virginia University were searching archival data from
the 64-meter Parkes telescope in New South Wales, Austra-
lia, for bright single pulses from Galactic radio pulsars. They
discovered a short and brilliant burst (Figure 1; now known
as the “Lorimer” burst) with a flux density or radio brightness
of 30 Jansky (Jy) 1 , bright enough to saturate the detectors
at Parkes (Lorimer et al., 2007). More oddly, unlike Galactic
radio pulsars, the burst had a dispersion measure (DM; see
the box, next page) far greater than the contribution of the
Milky Way along that line of sight — 375 pc/cm 3 compared
to the Galactic contribution of 25 pc/cm 3 .
1
16
GeminiFocus
Jansky = 10 -23 erg/cm 2 /s/Hz.
January 2018 / 2017 Year in Review