Wideband detection of FRB 20240114A with the Allen Telescope Array
FRB 20240114A, a bright repeating fast radio burst, was initially reported by the CHIME/FRB collaboration (ATel #16420) on January 26th 2024. High fluence emissions (> 10 Jy-ms) from this source have been reported by numerous radio telescopes, including peculiar heightened activity as observed by uGMRT (Panda et al. ATel #16494) and FAST (Zhang et al. ATel #16505) at 650 MHz and 1.25 GHz, respectively. Reports by Zhang et al. (ATel #16433) at FAST and Uttarkar et al. (ATel #16430) at Parkes/Murriyang indicate that the bursts exhibit highly band-limited or narrowband emission characteristics, spanning less than ~100 MHz. Similar behavior has been reported by Kumar et al. (ATel #16452) at the uGMRT. Moreover, observations with the widest instantaneous bandwidth across 704 MHz to 4032 MHz with the Parkes/Murriyang (Hobbs et al. 2019) revealed that the bursts are also band-limited (Uttarkar et al. ATel #16430). Recently, Hewitt et al. (ATel #16597) announced first detection above 2 GHz using the Nancay Radio Telescope also reporting the band-limited nature of these bursts.
In this report, we present detection of bursting behavior above 2 GHz from this source, with the first wideband burst covering a large bandwidth of approximately 800 MHz, utilizing the recently upgraded Allen Telescope Array (ATA). We initiated our follow-up campaign less than 24 hours after the FRB 20240114A was announced by CHIME (ATel #16420). Since MJD 60336, we have actively monitored the source, accumulating close to 200 hours of observations. Observations initially targeted the coordinates provided by the initial CHIME localization (RA: 21h27m39.89s, DEC: +04d21m00.36s, ATel #16420), and subsequently, from MJD 60397 onwards, the updated coordinates from EVN (RA: 21h27m39.835s, Dec: +04d19m45.634s; ATel #16542) are being used. For these observations, 20 of the 42, 6.1-m dishes were configured to target two independent 672 MHz spectral bands, one centered at 1.23 GHz (L-band), and another at 1.9 GHz (S-band). We used similar data products and searched for bursts using the SPANDAK pipeline as highlighted by Sheikh et al. (2024) along with an additional machine learning-based sorting algorithm for candidate prioritization (Gajjar et al. 2022).
Our search targeted bursts with a fluence greater than 3.3 and 3.6 Jy-ms at L-band and S-band, respectively. We identified eight bursts, with five detected at L-band. Of the S-band bursts, two were exclusively visible only at S-band showing clear emission above 2 GHz, while one was simultaneously detected at both bands spanning total bandwidth of approximately 800 MHz (see attached plots). Arrival times reported from our search pipeline of these bursts in the barycentric reference frame at the infinite frequency are as follows. These fluences were calculated across the entire respective observing bandwidth (672 MHz) using the radiometer equation for both bands. The detection statistics may indicate relatively more activity at S-band with time.
From these detections along with reports from Hewitt et al. (ATel #16597), we speculate that the source is progressively becoming active at higher radio frequencies. Additional observations and analysis of FRB 20240114A with the ATA are currently underway. We encourage robust followup at higher frequencies.
SPANDAK plots for these detections with the ATA can be found below.
