New Limits on the Low-frequency Radio Transient Sky Using 31 hr of All-sky Data with the OVRO-LWA

Abstract

We present the results of the first transient survey from the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) using 31 hr of data, in which we place the most constraining limits on the instantaneous transient surface density at timescales of 13 s to a few minutes and at frequencies below 100 MHz. The OVRO-LWA is a dipole array that images the entire viewable hemisphere with 58 MHz of bandwidth from 27 to 84 MHz at 13 s cadence. No transients are detected above a 6.5$\sigma$ flux density limit of 10.5 Jy, implying an upper limit to the transient surface density of $2.5\times 10^{-8}$ deg${}^{-2}$ at the shortest timescales probed, which is orders of magnitude deeper than has been achieved at sub-100 MHz frequencies and comparable flux densities to date. The nondetection of transients in the OVRO-LWA survey, particularly at minutes-long timescales, allows us to place further constraints on the rate of the potential population of transients uncovered by Stewart et al. (2016). From their transient rate, we expect a detection of $8.4_{-8.0}^{+31.8}$ events, and the probability of our null detection is $1.9_{-1.9}^{+644}\times 10^{-3}$, ruling out a transient rate $>1.4\times 10^{-4}{\text{days}}^{-1}{\text{deg}}^{-2}$ with 95% confidence at a flux density limit of 18.1 Jy, under the assumption of a flat spectrum and wide bandwidth. We discuss the implications of our nondetection for this population and further constraints that can be made on the source spectral index, intrinsic emission bandwidth, and resulting luminosity distribution.

arXiv comment20 pages, 8 figures, ApJ accepted

References in corpus (43)

• LOFAR: The LOw-Frequency ARray
• The Murchison Widefield Array: the Square Kilometre Array Precursor at low radio frequencies
• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• The GMRT 150 MHz All-sky Radio Survey: First Alternative Data Release TGSS ADR1
• The Birth of a Relativistic Outflow in the Unusual γ-ray Transient Swift J164449.3+573451
• An Accurate Flux Density Scale from 50 MHz to 50 GHz
• The Very Large Array Low-frequency Sky Survey Redux (VLSSr)
• A Radio-Selected Sample of Gamma Ray Burst Afterglows
• Observations of Fast Radio Bursts at Frequencies down to 400 Megahertz
• A powerful bursting radio source towards the Galactic Centre
• Design and characterization of the Large-Aperture Experiment to Detect the Dark Age (LEDA) radiometer systems
• Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence
• The characteristics of millisecond pulsar emission: III.From low to high frequencies
• Detecting Radio Emission from Cosmic Ray Air Showers and Neutrinos with a Digital Radio Telescope
• The Caltech-NRAO Stripe 82 Survey (CNSS) Paper I: The Pilot Radio Transient Survey In 50 deg${}^2$
• Auroral radio emission from late L and T dwarfs: A new constraint on dynamo theory in the substellar regime
• Ultra-Wideband Detection of 22 Coherent Radio Bursts on M Dwarfs
• The 21 cm Power Spectrum from the Cosmic Dawn: First Results from the OVRO-LWA
• The Strongest Magnetic Fields on the Coolest Brown Dwarfs
• The Radio Sky at Meter Wavelengths: m-Mode Analysis Imaging with the Owens Valley Long Wavelength Array
• Limits on Fast Radio Bursts and other transient sources at 182 MHz using the Murchison Widefield Array
• The variability timescales and brightness temperatures of radio flares from stars to supermassive black holes
• Radio and X-ray Observations of the Type Ic SN 2007gr Reveal an Ordinary, Non-relativistic Explosion
• LOFAR MSSS: Detection of a low-frequency radio transient in 400 hrs of monitoring of the North Celestial Pole
• The Dynamic Radio Sky
• A survey for transients and variables with the Murchison Widefield Array 32-tile prototype at 154 MHz
• The observed properties of Fast Radio Bursts
• Exploring the Transient Radio Sky with VLITE: Early Results
• GCRT J1742-3001: A New Radio Transient Towards the Galactic Center
• 154 MHz detection of faint, polarized flares from UV Ceti
• Low-Frequency Radio Transients in the Galactic Center
• Detection of Radio Emission from Fireballs
• A search for long-timescale, low-frequency radio transients
• Surveying the Dynamic Radio Sky with the Long Wavelength Demonstrator Array
• New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR
• Discovery of a Meter-Wavelength Radio Transient in the SWIRE Deep Field: 1046+59
• A simultaneous search for prompt radio emission associated with the short GRB 170112A using the all-sky imaging capability of the OVRO-LWA
• A Faint, Steep Spectum Burst from the Radio Transient GCRT J1745-3009
• Murchison Widefield Array Observations of Anomalous Variability: A Serendipitous Night-time Detection of Interplanetary Scintillation
• Detection of a Low-frequency Cosmic Radio Transient Using Two LWA Stations
• Rates, Flux Densities, and Spectral Indices of Meteor Radio Afterglows
• Dynamic Radio Spectra from two Fireballs
• A Matched Filter Technique For Slow Radio Transient Detection And First Demonstration With The Murchison Widefield Array

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