132 research outputs found
A sample of low energy bursts from FRB 121102
We present 41 bursts from the first repeating fast radio burst discovered
(FRB 121102). A deep search has allowed us to probe unprecedentedly low burst
energies during two consecutive observations (separated by one day) using the
Arecibo telescope at 1.4 GHz. The bursts are generally detected in less than a
third of the 580-MHz observing bandwidth, demonstrating that narrow-band FRB
signals may be more common than previously thought. We show that the bursts are
likely faint versions of previously reported multi-component bursts. There is a
striking lack of bursts detected below 1.35 GHz and simultaneous VLA
observations at 3 GHz did not detect any of the 41 bursts, but did detect one
that was not seen with Arecibo, suggesting preferred radio emission frequencies
that vary with epoch. A power law approximation of the cumulative distribution
of burst energies yields an index that is much steeper than the
previously reported value of . The discrepancy may be evidence for a
more complex energy distribution. We place constraints on the possibility that
the associated persistent radio source is generated by the emission of many
faint bursts ( ms). We do not see a connection between burst
fluence and wait time. The distribution of wait times follows a log-normal
distribution centered around s; however, some bursts have wait times
below 1 s and as short as 26 ms, which is consistent with previous reports of a
bimodal distribution. We caution against exclusively integrating over the full
observing band during FRB searches, because this can lower signal-to-noise.Comment: Accepted version. 16 pages, 7 figures, 1 tabl
Simultaneous X-ray, gamma-ray, and Radio Observations of the repeating Fast Radio Burst FRB 121102
We undertook coordinated campaigns with the Green Bank, Effelsberg, and
Arecibo radio telescopes during Chandra X-ray Observatory and XMM-Newton
observations of the repeating fast radio burst FRB 121102 to search for
simultaneous radio and X-ray bursts. We find 12 radio bursts from FRB 121102
during 70 ks total of X-ray observations. We detect no X-ray photons at the
times of radio bursts from FRB 121102 and further detect no X-ray bursts above
the measured background at any time. We place a 5 upper limit of
erg cm on the 0.5--10 keV fluence for X-ray bursts at
the time of radio bursts for durations ms, which corresponds to a burst
energy of erg at the measured distance of FRB 121102. We also
place limits on the 0.5--10 keV fluence of erg cm and
erg cm for bursts emitted at any time during the
XMM-Newton and Chandra observations, respectively, assuming a typical X-ray
burst duration of 5 ms. We analyze data from the Fermi Gamma-ray Space
Telescope Gamma-ray Burst Monitor and place a 5 upper limit on the
10--100 keV fluence of erg cm ( erg at
the distance of FRB 121102) for gamma-ray bursts at the time of radio bursts.
We also present a deep search for a persistent X-ray source using all of the
X-ray observations taken to date and place a 5 upper limit on the
0.5--10 keV flux of erg s cm (
erg~s at the distance of FRB 121102). We discuss these non-detections in
the context of the host environment of FRB 121102 and of possible sources of
fast radio bursts in general.Comment: 13 pages, 5 figures, published in Ap
HI, FRB, what's your z: The first FRB host galaxy redshift from radio observations
Identification and follow up observations of the host galaxies of fast radio
bursts (FRBs) not only help us understand the environments in which the FRB
progenitors reside, but also provide a unique way of probing the cosmological
parameters using the dispersion measures of FRBs and distances to their origin.
A fundamental requirement is an accurate distance measurement to the FRB host
galaxy, but for some sources viewed through the Galactic plane, optical/NIR
spectroscopic redshifts are extremely difficult to obtain due to dust
extinction. Here we report the first radio-based spectroscopic redshift
measurement for an FRB host galaxy, through detection of its neutral hydrogen
(HI) 21-cm emission using MeerKAT observations. We obtain an HI-based redshift
of z = 0.0357 for the host galaxy of FRB 20230718A, an apparently non-repeating
FRB detected in the CRAFT survey and localized at a Galactic latitude of -0.367
deg. Our observations also reveal that the FRB host galaxy is interacting with
a nearby companion, which is evident from the detection of an HI bridge
connecting the two galaxies. A subsequent optical spectroscopic observation
confirmed an FRB host galaxy redshift of 0.0359 +- 0.0004. This result
demonstrates the value of HI to obtain redshifts of FRBs at low Galactic
latitudes and redshifts. Such nearby FRBs whose dispersion measures are
dominated by the Milky Way can be used to characterise these components and
thus better calibrate the remaining cosmological contribution to dispersion for
more distant FRBs that provide a strong lever arm to examine the Macquart
relation between cosmological DM and redshift.Comment: 13 pages, 3 figures. Accepted to ApJ Letter
A Multi-telescope Campaign on FRB 121102: Implications for the FRB Population
We present results of the coordinated observing campaign that made the first
subarcsecond localization of a Fast Radio Burst, FRB 121102. During this
campaign, we made the first simultaneous detection of an FRB burst by multiple
telescopes: the VLA at 3 GHz and the Arecibo Observatory at 1.4 GHz. Of the
nine bursts detected by the Very Large Array at 3 GHz, four had simultaneous
observing coverage at other observatories. We use multi-observatory constraints
and modeling of bursts seen only at 3 GHz to confirm earlier results showing
that burst spectra are not well modeled by a power law. We find that burst
spectra are characterized by a ~500 MHz envelope and apparent radio energy as
high as erg. We measure significant changes in the apparent
dispersion between bursts that can be attributed to frequency-dependent
profiles or some other intrinsic burst structure that adds a systematic error
to the estimate of DM by up to 1%. We use FRB 121102 as a prototype of the FRB
class to estimate a volumetric birth rate of FRB sources Mpc yr, where is the number of bursts per
source over its lifetime. This rate is broadly consistent with models of FRBs
from young pulsars or magnetars born in superluminous supernovae or long
gamma-ray bursts, if the typical FRB repeats on the order of thousands of times
during its lifetime.Comment: 17 pages, 7 figures. Submitted to AAS Journal
MWA rapid follow-up of gravitational wave transients: prospects for detecting prompt radio counterparts
We present and evaluate the prospects for detecting coherent radio
counterparts to gravitational wave (GW) events using Murchison Widefield Array
(MWA) triggered observations. The MWA rapid-response system, combined with its
buffering mode ( minutes negative latency), enables us to catch any
radio signals produced from seconds prior to hours after a binary neutron star
(BNS) merger. The large field of view of the MWA ( at
120\,MHz) and its location under the high sensitivity sky region of the
LIGO-Virgo-KAGRA (LVK) detector network, forecast a high chance of being
on-target for a GW event. We consider three observing configurations for the
MWA to follow up GW BNS merger events, including a single dipole per tile, the
full array, and four sub-arrays. We then perform a population synthesis of BNS
systems to predict the radio detectable fraction of GW events using these
configurations. We find that the configuration with four sub-arrays is the best
compromise between sky coverage and sensitivity as it is capable of placing
meaningful constraints on the radio emission from 12.6\% of GW BNS detections.
Based on the timescales of four BNS merger coherent radio emission models, we
propose an observing strategy that involves triggering the buffering mode to
target coherent signals emitted prior to, during or shortly following the
merger, which is then followed by continued recording for up to three hours to
target later time post-merger emission. We expect MWA to trigger on
BNS merger events during the LVK O4 observing run, which
could potentially result in two detections of predicted coherent emission.Comment: Accepted for publication in PAS
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