Monitoring the Sky with the Prototype All-Sky Imager on the LWA1

Obenberger, K. S.; Taylor, G. B.; Hartman, J. M.; Dowell, Jayce; DuBois, Andrew; DuBois, D. F.; Henning, P. A.; Lazio, Joseph; Michalak, Sarah; Schinzel, F. K.

doi:10.1142/s225117171550004x

Cited by 34 publications

(51 citation statements)

References 28 publications

(25 reference statements)

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“…Obenberger et al [] describe a method to flux calibrate PASI images. Following this procedure we get flux densities of 730±50 (38.0 MHz), 620±50 (38.0 MHz), 1800±140 (25.6 MHz), and 480±50 Jy (34.0 MHz) for the brightest regions of M1, M2, M3, and M4 where 1 Jy = 10 −26 W m −2 Hz −1 .…”

Section: Discussionmentioning

confidence: 99%

“…Following this procedure we get flux densities of 730±50 (38.0 MHz), 620±50 (38.0 MHz), 1800±140 (25.6 MHz), and 480±50 Jy (34.0 MHz) for the brightest regions of M1, M2, M3, and M4 where 1 Jy = 10 −26 W m −2 Hz −1 . Uncertainties are derived from the image noise and a 15% error in the calibrator source Cygnus A [ Obenberger et al , ].…”

Section: Discussionmentioning

confidence: 99%

“…As described in Obenberger et al [], PASI produces near real‐time images of the sky with all four Stokes parameters. PASI can be tuned to any frequency between 10 and 88 MHz, and the images cover 75 kHz of bandwidth.…”

Section: Observationsmentioning

confidence: 99%

“…While the radio emission has been observed between 25.6 and 55.0 MHz, continuous broadband measurements have only been made between 37 and 55 MHz. Most events are recorded using the narrowband (∼100 kHz) Prototype All‐Sky Imager (PASI), a backend correlator/imager of the first station of the Long Wavelength Array (LWA1) [ Taylor et al , ; Ellingson et al , ; Obenberger et al , ]. PASI images have an extremely large field of view of 1 π sr (∼10 4 deg 2 ) but have limited sensitivity due to the narrow bandwidth, which also prevents any spectral characterization of the events.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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Using the narrowband all‐sky imager mode of the Long Wavelength Array (LWA1), we have now detected 30 transients at 25.6 MHz, 1 at 34 MHz, and 93 at 38.0 MHz. While we have only optically confirmed that 37 of these events are radio afterglows from meteors, evidence suggests that most, if not all, are. Using the beam‐forming mode of the LWA1, we have also captured the broadband spectra between 22.0 and 55.0 MHz of four events. We compare the smooth, spectral components of these four events and fit the frequency‐dependent flux density to a power law, and find that the spectral index is time variable, with the spectrum steepening over time for each meteor afterglow. Using these spectral indices along with the narrowband flux density measurements of the 123 events at 25.6 and 38 MHz, we predict the expected flux densities and rates for meteor afterglows potentially observable by other low‐frequency radio telescopes.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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“…prompt emission from 32 GRBs using the LWA1 Prototype All Sky Imager (PASI; Ellingson et al 2013;Obenberger et al 2015), and Kaplan et al (2015) Table 2 for a summary of previous radio surveys specifically targeting prompt emission associated with GRBs. Despite these difficult observational requirements, and the speculative nature of the models, low-frequency radio searches for counterparts to short GRBs remain valuable.…”

Section: Introductionmentioning

confidence: 99%

A Simultaneous Search for Prompt Radio Emission Associated with the Short GRB 170112A Using the All-sky Imaging Capability of the OVRO-LWA

Anderson

Hallinan

Eastwood

et al. 2018

ApJ

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We have conducted the most sensitive low-frequency (below 100 MHz) search to date for prompt, low-frequency radio emission associated with short-duration gamma-ray bursts (GRBs), using the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA). The OVRO-LWA's nearly full-hemisphere field of view (∼20,000 square degrees) allows us to search for low-frequency (sub-100 MHz) counterparts for a large sample of the subset of GRB events for which prompt radio emission has been predicted. Following the detection of short GRB 170112A by Swift, we used all-sky OVRO-LWA images spanning one hour prior to and two hours following the GRB event to search for a transient source coincident with the position of GRB 170112A. We detect no transient source to within a 3σ flux density limit of 4.5Jy at 13 s timescales for frequencies spanning 27-84MHz. We place constraints on a number of models predicting prompt, low-frequency radio emission accompanying short GRBs and their potential binary neutron star merger progenitors, and place an upper limit of L radio / L γ 3.5×10−6 on the fraction of energy released in the prompt radio emission, under the assumptions of negligible scattering of the radio pulse and beaming of emission along the line of sight. These observations serve as a pilot effort for a program targeting a wider sample of both short and long GRBs with the OVRO-LWA, including bursts with confirmed redshift measurements that are critical to placing constraining limits on prompt radio emission models, as well as a program for the follow-up of gravitational wave compact binary coalescence events detected by advanced LIGO and Virgo.

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Dynamic radio spectra from two fireballs

et al. 2015

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We present dynamic spectra from the Long Wavelength Array telescope of two large meteors (fireballs) observed to emit between 37 and 54 MHz. These spectra show the first ever recorded broadband measurements of this newly discovered VHF emission. The spectra show that the emission is smooth and steep, getting very bright at lower frequencies. We suggest that this signal is possibly emission of Langmuir waves and that these waves could be excited by a bump‐on‐tail instability within the trail. The spectra of one fireball display broadband temporal frequency sweeps. We suggest that these sweeps are evidence of individual expanding clumps of emitting plasma. While some of these proposed clumps may have formed at the very beginning of the fireball event, others must have formed seconds after the initial event.

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Monitoring the Sky with the Prototype All-Sky Imager on the LWA1

Cited by 34 publications

References 28 publications

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

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

A Simultaneous Search for Prompt Radio Emission Associated with the Short GRB 170112A Using the All-sky Imaging Capability of the OVRO-LWA

Dynamic radio spectra from two fireballs

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