114 research outputs found
A search for rotating radio transients and fast radio bursts in the Parkes high-latitude pulsar survey
Discoveries of rotating radio transients and fast radio bursts (FRBs) in
pulsar surveys suggest that more of such transient sources await discovery in
archival data sets. Here we report on a single-pulse search for dispersed radio
bursts over a wide range of Galactic latitudes (|b| < ) in data
previously searched for periodic sources by Burgay et al. We re-detected 20 of
the 42 pulsars reported by Burgay et al. and one rotating radio transient
reported by Burke-Spolaor. No FRBs were discovered in this survey. Taking into
account this result, and other recent surveys at Parkes, we corrected for
detection sensitivities based on the search software used in the analyses and
the different backends used in these surveys and find that the all-sky FRB
event rate for sources with a fluence above 4.0 Jy ms at 1.4 GHz to be FRBs day sky, where the
uncertainties represent a confidence interval. While this rate is lower
than inferred from previous studies, as we demonstrate, this combined event
rate is consistent with the results of all systematic FRB searches at Parkes to
date and does not require the need to postulate a dearth of FRBs at
intermediate latitudes.Comment: Accepted, 10 pages, 6 figure
GBTrans: A commensal search for radio pulses with the Green Bank twenty metre telescope
We describe GBTrans, a real-time search system designed to find fast radio
bursts (FRBs) using the 20-m radio telescope at the Green Bank Observatory. The
telescope has been part of the Skynet educational program since 2015. We give
details of the observing system and report on the non-detection of FRBs from a
total observing time of 503 days. Single pulses from four known pulsars were
detected as part of the commensal observing. The system is sensitive enough to
detect approximately half of all currently known FRBs and we estimate that our
survey probed redshifts out to about 0.3 corresponding to an effective survey
volume of around 124,000~Mpc. Modeling the FRB rate as a function of
fluence, , as a power law with , we constrain the index at the 90% confidence level. We discuss the implications of this result
in the context of constraints from other FRB surveys.Comment: 7 pages, 6 figure
Simultaneous Radio And X-Ray Observations Of Psr B0611+22
We report results from simultaneous radio and X-ray observations of PSR B0611+22 which is known to exhibit bursting in its single-pulse emission. The pulse phase of the bursts vary with radio frequency. The bursts are correlated in 327/150 MHz data sets while they are anti-correlated, with bursts at one frequency associated with normal emission at the other, in 820/150 MHz data sets. Also, the flux density of this pulsar is lower than expected at 327 MHz assuming a power law. We attribute this unusual behaviour to the pulsar itself rather than absorption by external astrophysical sources. Using this data set over an extensive frequency range, we show that the bursting phenomenon in this pulsar exhibits temporal variance over a span of few hours. We also show that the bursting is quasi-periodic over the observed band. The anti-correlation in the phase offset of the burst mode at different frequencies suggests that the mechanisms responsible for phase offset and flux enhancement have different dependencies on the frequency. We did not detect the pulsar with XMM-Newton and place a 99 per cent confidence upper limit on the X-ray efficiency of 10-5
Setiburst: A Robotic, Commensal, Realtime Multi-Science Backend For The Arecibo Telescope
Radio astronomy has traditionally depended on observatories allocating time to observers for exclusive use of their telescopes. The disadvantage of this scheme is that the data thus collected is rarely used for other astronomy applications, and in many cases, is unsuitable. For example, properly calibrated pulsar search data can, with some reduction, be used for spectral line surveys. A backend that supports plugging in multiple applications to a telescope to perform commensal data analysis will vastly increase the science throughput of the facility. In this paper, we presen
Uncertainty Relations in Deformation Quantization
Robertson and Hadamard-Robertson theorems on non-negative definite hermitian
forms are generalized to an arbitrary ordered field. These results are then
applied to the case of formal power series fields, and the
Heisenberg-Robertson, Robertson-Schr\"odinger and trace uncertainty relations
in deformation quantization are found. Some conditions under which the
uncertainty relations are minimized are also given.Comment: 28+1 pages, harvmac file, no figures, typos correcte
Singular Value Homogenization: a simple preconditioning technique for linearly constrained optimization and its potential applications in medical therapy
A Search for Fast Radio Bursts with the GBNCC Pulsar Survey
We report on a search for Fast Radio Bursts (FRBs) with the Green Bank
Northern Celestial Cap (GBNCC) Pulsar Survey at 350 MHz. Pointings amounting to
a total on-sky time of 61 days were searched to a DM of 3000 pc cm while
the rest (23 days; 29% of the total time) were searched to a DM of 500 pc
cm. No FRBs were detected in the pointings observed through May 2016. We
estimate a 95% confidence upper limit on the FRB rate of FRBs
sky day above a peak flux density of 0.63 Jy at 350 MHz for an
intrinsic pulse width of 5 ms. We place constraints on the spectral index
by running simulations for different astrophysical scenarios and
cumulative flux density distributions. The non-detection with GBNCC is
consistent with the 1.4-GHz rate reported for the Parkes surveys for in the absence of scattering and free-free absorption and in the presence of scattering, for a Euclidean flux distribution. The
constraints imply that FRBs exhibit either a flat spectrum or a spectral
turnover at frequencies above 400 MHz. These constraints also allow estimation
of the number of bursts that can be detected with current and upcoming surveys.
We predict that CHIME may detect anywhere from several to 50 FRBs a day
(depending on model assumptions), making it well suited for interesting
constraints on spectral index, the log -log slope and pulse profile
evolution across its bandwidth (400-800 MHz).Comment: 18 pages, 10 figures, Accepted for publication in Ap
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