Upper limits on low-frequency emission from FRBs 200914 and 200919 from SKA-Low prototype stations
ATel #14044; M. Sokolowski, N. D. R. Bhat, R. B. Wayth, J. Broderick, D. Minchin, A. McPhail, D. Ung, B. Crosse, D. Davidson, T. Booler, S. Tingay, D. Price, B. Juswardy, A. Sutinjo (ICRAR/Curtin University) on behalf of the EDA2 Team. G. Bernardi, P. Bolli, J. Monari, A. Mattana, F. Perini, G. Comoretto, G. Macario, G. Pupillo, M. Schiaffino (INAF) on behalf of the AAVS2 Team. A. Magro (University of Malta), R. Chiello (University of Oxford), P. Benthem (ASTRON) and M. Waterson (SKA Organisation, Manchester)
on 27 Sep 2020; 12:17 UT
Credential Certification: Marcin Sokolowski (marcin.sokolowski@curtin.edu.au)
Subjects: Radio, Fast Radio Burst
The Engineering Development Array 2 (EDA2; Wayth et al., in prep.) and the Aperture Array Verification System 2 (AAVS2; Bolli et al., in prep.) are two prototype stations of the low-frequency component of the Square Kilometre Array (SKA-Low). During the times of FRBs 200914 and 200919 (Gupta et al. ATEL #14040), both EDA2 and AAVS2 were performing test commissioning observations, and thus fortuitously, effectively co-observed the FRBs at low frequencies. The data were collected in a correlated mode using a single coarse (narrow-band) channel (approximately 0.926 MHz bandwidth), at central frequencies 159.4 (EDA2) and 229.7 MHz (AAVS2), which can be used to produce all-sky images in near real-time. The correlated data were analysed using an automatic transient detection algorithm (Sokolowski et al., in prep.), and the data around the vicinity of FRB locations and the times were also visually inspected.
Neither of these have revealed any low-frequency counterparts, resulting in the following (1 sigma) upper limits:
EDA2 at 159.4 MHz :
FRB200919 : ~25 kJy ms, implied spectral index limit > -4.0 (between 159.4 MHz and 1400 MHz)
FRB200914 : ~26 kJy ms, implied spectral index limit > -4.7 (between 159.4 MHz and 1400 MHz)
AAVS2 at 229.7 MHz :
FRB200919 : ~33 kJy ms, implied spectral index limit > -4.9 (between 229.7 MHz and 1400 MHz)
FRB200914 : ~32 kJy ms, implied spectral index limit > -5.8 (between 229.7 MHz and 1400 MHz)
Both the systems are currently in their early stages of development, and we note that both FRBs were observed at fairly low elevations. As a result, the sensitivities achieved are at ~10% level of the near-zenith (maximum). Improved sensitivities (and hence better constraints) will be possible in the future when more instantaneous bandwidth becomes available and for observations at more optimal elevations.
