Rates, flux densities, and spectral indices of meteor radio afterglows

Obenberger, K. S.; Dowell, Jayce; Hancock, P. J.; Holmes, J. M.; Pedersen, T. R.; Schinzel, F. K.; Taylor, G. B.

doi:10.1002/2016ja022606

Cited by 15 publications

(30 citation statements)

References 14 publications

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“…All meteor events observed by the OVRO-LWA in this data set were clearly reflection events from ionized trails. However, this is not inconsistent with the rate of fireball radio emission predicted by Obenberger et al 2016; for a flux density lower limit of 540 Jy at 38 MHz, they predict a detection rate of approximately 40 meteor afterglows year −1 .…”

Section: Meteor Reflection Eventsmentioning

confidence: 58%

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

Anderson

Hallinan

Eastwood

et al. 2019

ApJ

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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 6.5σ flux density limit of 10.5 Jy, implying an upper limit to the transient surface density of 2.5 × 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 +31.8 −8.0 events, and the probability of our null detection is 1.9 +644 −1.9 × 10 −3 , ruling out a transient rate > 1.4 × 10 −4 days −1 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.

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Section: Meteor Reflection Eventsmentioning

confidence: 58%

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

Anderson

Hallinan

Eastwood

et al. 2019

ApJ

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“…Here we used one of the four meteors given in Obenberger et al (2016b) for extrapolation. This meteor belongs to a group of faint/common meteors occurring 130 times year −1 π sr −1 .…”

Section: Baseline and Channel Limits In Imaging Processmentioning

confidence: 99%

“…In Figure 9 we indicate three LWA1 events with event densities 15, 40 and 130 times year −1 π sr −1 , as described in Obenberger et al (2016b). A spectral index of -4 is used to extrapolate flux densities of these events to the MWA frequency range.…”

Section: Probability Of Detectionmentioning

confidence: 99%

“…Broadband measurements were also made with the beamformer mode of the LWA1 in order to obtain the dynamic spectra of the transient events (Obenberger et al 2016b). Three beams were formed and pointed around zenith at azimuths of 60 • , 180 • , and 240 • , all with elevations of 87 • .…”

Section: Introductionmentioning

confidence: 99%

“…The frequency-dependent flux densities of these events were fit to a power law, and the spectral indices were found to be time variable, with the spectrum steepening over time. Obenberger et al (2016b) also discussed the potential for other observatories to measure meteor spectra, including the Murchision Widefield Array (MWA; Tingay et al 2013a) in Australia, the Amsterdam-ASTRON Radio Transients Facility and Analysis Center (AARTFAAC; Prasad et al 2014) based on the Low-Frequency Array (LOFAR; Van Haarlem et al 2013) in the Netherlands, and two additional LWA stations. It was concluded that the MWA, with its exceptionally high sensitivity, had the best opportunity to test the high-frequency predictions of meteor radio afterglows.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Limits on radio emission from meteors using the MWA

Zhang

Hancock

Devillepoix

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Recently, low frequency, broadband radio emission has been observed accompanying bright meteors by the Long Wavelength Array (LWA). The broadband spectra between 20 and 60 MHz were captured for several events, while the spectral index (dependence of flux density on frequency, with S ν ∝ ν α ) was estimated to be −4 ± 1 during the peak of meteor afterglows. Here we present a survey of meteor emission and other transient events using the Murchison Widefield Array (MWA) at 72-103 MHz. In our 322-hour survey, down to a 5σ detection threshold of 3.5 Jy/beam, no transient candidates were identified as intrinsic emission from meteors. We derived an upper limit of -3.7 (95% confidence limit) on the spectral index in our frequency range. We also report detections of other transient events, like reflected FM broadcast signals from small satellites, conclusively demonstrating the ability of the MWA to detect and track space debris on scales as small as 0.1 m in low Earth orbits.

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Altitudinal dependence of meteor radio afterglows measured via optical counterparts

Obenberger

Holmes

Dowell

et al. 2016

Geophysical Research Letters

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Utilizing the all‐sky imaging capabilities of the first station of the Long Wavelength Array along with a host of all‐sky optical cameras, we have now observed 44 optical meteor counterparts to radio afterglows. Combining these observations, we have determined the geographic positions of all 44 afterglows. Comparing the number of radio detections as a function of altitude above sea level to the number of expected bright meteors, we find a strong altitudinal dependence characterized by a cutoff below ∼90 km, below which no radio emission occurs, despite the fact that many of the observed optical meteors penetrated well below this altitude. This cutoff suggests that wave damping from electron collisions is an important factor for the evolution of radio afterglows. This finding agrees with the hypothesis that the emission is the result of electron plasma wave emission.

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Rates, flux densities, and spectral indices of meteor radio afterglows

Cited by 15 publications

References 14 publications

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

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

Limits on radio emission from meteors using the MWA

Altitudinal dependence of meteor radio afterglows measured via optical counterparts

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