13 research outputs found
Limits on Simultaneous and Delayed Optical Emission from Well-Localized Fast Radio Bursts
We present the largest compilation to date of optical observations during and
following fast radio bursts (FRBs). The data set includes our dedicated
simultaneous and follow-up observations, as well as serendipitous archival
survey observations, for a sample of 15 well-localized FRBs, including 8
repeating and 7 one-off sources. Our simultaneous (and nearly simultaneous with
a -sec delay) optical observations of 7 (1) bursts from the repeating FRB
20220912A provide the deepest such limits to date for any extragalactic FRB,
reaching a luminosity limit of erg s
( erg s); these observations are also the
deepest to date in terms of optical flux to radio fluence ratio of ms ( ms),
and place a limit on the flux ratio of
on a msec timescale or () on a sec
timescale. These simultaneous limits provide useful constraints in the context
of FRB emission models, such as the pulsar magnetosphere and pulsar nebula
models. Interpreting all available optical limits in the context of the FRB
synchrotron maser model, we find that they constrain the flare energies to
erg (depending on the distances of the various
repeating FRBs, with erg for SGR 1935+2154). These limits
are generally at least an order of magnitude larger than the energies inferred
from the FRBs themselves, although in the case of FRB 20220912A our
simultaneous and rapid follow-up observations severely restrict the model
parameter space. We conclude by exploring the potential of future rapid
response and simultaneous observations with large optical telescopes.Comment: 22 pages, 8 figures, submitted to ApJL. Please let us know if we
missed any optical and/or radio observations of the FRB sampl
A Distant Fast Radio Burst Associated with Its Host Galaxy by the Very Large Array
We present the discovery and subarcsecond localization of a new fast radio burst (FRB) by the Karl G. Jansky Very Large Array (VLA) and realfast search system. The FRB was discovered on 2019 June 14 with a dispersion measure of 959 pc cm⁻³. This is the highest DM of any localized FRB and its measured burst fluence of 0.6 Jy ms is less than nearly all other FRBs. The source is not detected to repeat in 15 hr of VLA observing and 153 hr of CHIME/FRB observing. We describe a suite of statistical and data quality tests we used to verify the significance of the event and its localization precision. Follow-up optical/infrared photometry with Keck and Gemini associate the FRB with a pair of galaxies with r ∼ 23 mag. The false-alarm rate for radio transients of this significance that are associated with a host galaxy is roughly 3×10⁻⁴ hr⁻¹. The two putative host galaxies have similar photometric redshifts of z_(phot) ∼ 0.6, but different colors and stellar masses. Comparing the host distance to that implied by the dispersion measure suggests a modest (~ 50 pc/cm⁻³) electron column density associated with the FRB environment or host galaxy/galaxies
A Distant Fast Radio Burst Associated with Its Host Galaxy by the Very Large Array
We present the discovery and subarcsecond localization of a new fast radio burst (FRB) by the Karl G. Jansky Very Large Array (VLA) and realfast search system. The FRB was discovered on 2019 June 14 with a dispersion measure of 959 pc cm⁻³. This is the highest DM of any localized FRB and its measured burst fluence of 0.6 Jy ms is less than nearly all other FRBs. The source is not detected to repeat in 15 hr of VLA observing and 153 hr of CHIME/FRB observing. We describe a suite of statistical and data quality tests we used to verify the significance of the event and its localization precision. Follow-up optical/infrared photometry with Keck and Gemini associate the FRB with a pair of galaxies with r ∼ 23 mag. The false-alarm rate for radio transients of this significance that are associated with a host galaxy is roughly 3×10⁻⁴ hr⁻¹. The two putative host galaxies have similar photometric redshifts of z_(phot) ∼ 0.6, but different colors and stellar masses. Comparing the host distance to that implied by the dispersion measure suggests a modest (~ 50 pc/cm⁻³) electron column density associated with the FRB environment or host galaxy/galaxies
A fast radio burst localized at detection to a galactic disk using very long baseline interferometry
Fast radio bursts (FRBs) are millisecond-duration, luminous radio transients
of extragalactic origin. These events have been used to trace the baryonic
structure of the Universe using their dispersion measure (DM) assuming that the
contribution from host galaxies can be reliably estimated. However,
contributions from the immediate environment of an FRB may dominate the
observed DM, thus making redshift estimates challenging without a robust host
galaxy association. Furthermore, while at least one Galactic burst has been
associated with a magnetar, other localized FRBs argue against magnetars as the
sole progenitor model. Precise localization within the host galaxy can
discriminate between progenitor models, a major goal of the field. Until now,
localizations on this spatial scale have only been carried out in follow-up
observations of repeating sources. Here we demonstrate the localization of FRB
20210603A with very long baseline interferometry (VLBI) on two baselines, using
data collected only at the time of detection. We localize the burst to SDSS
J004105.82+211331.9, an edge-on galaxy at , and detect recent
star formation in the kiloparsec-scale vicinity of the burst. The edge-on
inclination of the host galaxy allows for a unique comparison between the line
of sight towards the FRB and lines of sight towards known Galactic pulsars. The
DM, Faraday rotation measure (RM), and scattering suggest a progenitor
coincident with the host galactic plane, strengthening the link between the
environment of FRB 20210603A and the disk of its host galaxy. Single-pulse VLBI
localizations of FRBs to within their host galaxies, following the one
presented here, will further constrain the origins and host environments of
one-off FRBs.Comment: 40 pages, 13 figures, submitted. Fixed typo in abstrac
CHIME/FRB Discovery of 25 Repeating Fast Radio Burst Sources
We present the discovery of 25 new repeating fast radio burst (FRB) sources
found among CHIME/FRB events detected between 2019 September 30 and 2021 May 1.
The sources were found using a new clustering algorithm that looks for multiple
events co-located on the sky having similar dispersion measures (DMs). The new
repeaters have DMs ranging from 220 pc cm to 1700 pc
cm, and include sources having exhibited as few as two bursts to as many
as twelve. We report a statistically significant difference in both the DM and
extragalactic DM (eDM) distributions between repeating and apparently
nonrepeating sources, with repeaters having lower mean DM and eDM, and we
discuss the implications. We find no clear bimodality between the repetition
rates of repeaters and upper limits on repetition from apparently nonrepeating
sources after correcting for sensitivity and exposure effects, although some
active repeating sources stand out as anomalous. We measure the repeater
fraction and find that it tends to an equilibrium of % over
our exposure thus far. We also report on 14 more sources which are promising
repeating FRB candidates and which merit follow-up observations for
confirmation.Comment: Submitted to ApJ. Comments are welcome and follow-up observations are
encouraged
Sub-second periodicity in a fast radio burst
Fast radio bursts (FRBs) are millisecond-duration flashes of radio waves that
are visible at distances of billions of light-years. The nature of their
progenitors and their emission mechanism remain open astrophysical questions.
Here we report the detection of the multi-component FRB 20191221A and the
identification of a periodic separation of 216.8(1) ms between its components
with a significance of 6.5 sigmas. The long (~3 s) duration and nine or more
components forming the pulse profile make this source an outlier in the FRB
population. Such short periodicity provides strong evidence for a neutron-star
origin of the event. Moreover, our detection favours emission arising from the
neutron-star magnetosphere, as opposed to emission regions located further away
from the star, as predicted by some models.Comment: Updated to conform to the accepted versio
Spectropolarimetry of Fast Radio Bursts, Radio Galaxies, and the Milky Way
Fast radio bursts (FRBs) are microsecond to millisecond extragalactic radio transients. Despite a published sample of over 600 FRB observations, the nature of their progenitor/s, the mechanism for their emission and their domain of applicability as probes remain open problems. Here, information on their polarized signals may offer illuminating clues, however, only a small fraction of the current FRB sample report polarization information. This modest sample exhibits a rich phenomenology in its polarized properties and has provided some important discoveries that have refined our under- standing of the FRB population. The FRB survey operating between 400-800 MHz on the Canadian Hydrogen Intensity Mapping Experiment (CHIME/FRB) should detect several thousand FRBs over the next few years. A significant fraction of these events will be recorded in a mode that enables po- larization analysis. Such a large sample requires an automated pipeline in order to reduce recorded data into useful summary statistics for different FRB properties.
This thesis reviews the polarization analysis pipeline developed for CHIME/FRB, along with the various science enabled with polarized data. The analysis tools developed specifically for CHIME/FRB observations are illustrated using a combination of simulated and real FRBs. These tools include a parametric method that robustly characterizes dominant sources of instrumental polarization affecting the CHIME telescope. A novel method for circumventing bandwidth depolar- ization is outlined and validated with a real CHIME-detected FRB whose Faraday rotation measure (RM) is the second largest from any FRB observed to date. Time dependence in the polarization properties of two prolific repeating CHIME/FRB sources is studied where significant changes in RM are observed, strongly suggesting a dynamic local environment. Joint analysis of dispersion and rotation measures are used to constrain the field strength in the local environment and are compared to equivalent measurements from other repeating FRBs and pulsars. Finally, this thesis explores new methods for refining the Faraday rotating Galactic foreground, a major contaminant in the interpretation of FRB RMs, through joint analysis of RMs obtained from extragalactic sources and foreground emission from the interstellar medium.Ph.D
Polarization properties of the 128 non-repeating fast radio bursts from the first CHIME/FRB baseband catalog
International audienceWe present a 400-800 MHz polarimetric analysis of 128 non-repeating fast radio bursts (FRBs) from the first CHIME/FRB baseband catalog, increasing the total number of FRB sources with polarization properties by a factor of ~3. Of the 128 sources, 89 FRBs have >6 linearly polarized detections, 29 FRBs fall below this significance threshold and are deemed linearly unpolarized, and for 10 FRBs the polarization data are contaminated by instrumental polarization. For the 89 polarized FRBs, we find Faraday rotation measure (RM) amplitudes, after subtracting approximate Milky Way contributions, in the range 0.5-1160 rad m with a median of 53.8 rad m. Most non-repeating FRBs in our sample have RMs consistent with Milky Way-like host galaxies and their linear polarization fractions range from 10% to 100% with a median of 63%. The non-repeater RMs and linear polarization fraction distributions are consistent with those of repeating FRBs. We see marginal evidence that non-repeating FRBs have more constraining lower limits than repeating FRBs for the host electron-density-weighted line-of-sight magnetic field strength. We classify the non-repeating FRB polarization position angle (PA) profiles into four archetypes: (i) single component with constant PA (57% of the sample), (ii) single component with variable PA (10%), (iii) multiple components with a single constant PA (22%), and (iv) multiple components with different or variable PAs (11%). We see no evidence for population-wide frequency-dependent depolarization and, therefore, the spread in the distribution of fractional linear polarization is likely intrinsic to the FRB emission mechanism