A broadband study of FRB20240114A with the Effelsberg 100-m radio telescope

TL;DR

This work presents a detailed broadband study of FRB20240114A using the Effelsberg 100-m telescope with the Ultra BroadBand receiver (1.3–6.0 GHz), yielding over 700 bursts across four epochs. By performing coherent dedispersion, single-pulse searches, and multi-Gaussian burst fitting across six rebinned sub-bands, the authors classify bursts into four spectro-temporal morphologies, document modest frequency-dependent width evolution with constant fractional bandwidth, and identify significant rate variability likely influenced by scintillation. A Weibull-based arrival-time analysis and a cross-band waiting-time study reveal a predominantly independent burst process with occasional short-timescale clustering and a tendency toward downward frequency drifts in clustered events, including frequency shifts spanning several GHz on second timescales. The results imply a combination of intrinsic emission physics and propagation effects shaping FRB20240114A’s complex broadband behavior, and they underscore the value of simultaneous wideband observations for constraining FRB emission mechanisms and environmental conditions.

Abstract

We present Effelsberg 100-m telescope observations of the hyperactive repeating fast radio burst source FRB 20240110A, discovered by CHIME/FRB in January 2024. Using the Ultra BroadBand (UBB) receiver, spanning 1.3-6.0 GHz, we detected over 700 unique bursts across four observing epochs. A comprehensive analysis of their temporal and spectral properties reveals four distinct spectro-temporal morphologies, including simple, complex and frequency-drifting structures. No bursts were detected across the full UBB band, confirming the band-limited emission typical of repeating FRBs. We find modest frequency evolution in burst widths but constant fractional bandwidths, and strong variability in burst rates that may be influenced by scintillation. The waiting-time distributions indicate predominantly independent burst events, with occasional clustering suggesting a characteristic emission timescale of $\sim$10 ms. Additionally, this study presents a multi-frequency analysis of waiting-time distributions, offering new insights into the complex frequency drifts commonly observed in repeating FRBs. These broadband observations provide a detailed view of the frequency-dependent burst behavior of FRB 20240110A and offer insights into the variability and temporal structure of repeating FRB emission.

Figures (7)

• Figure 1: Example dynamic spectra of selected bursts from FRB20240114A , illustrating the distinct morphologies discussed in Section \ref{['sec:spec-temp_properties']}. In each subplot, the left panel shows the burst spectrum across the full UBB frequency coverage where the vertical dashed lines indicate the rebinned frequency bands, while the right panel presents the dynamic spectrum (bottom) in the UBB band where the burst is detected, together with its frequency-averaged temporal profile (top). The temporal profiles are fitted with red solid curves, with dashed vertical lines marking the measured burst widths. The burst spectra were generated using a frequency downsampling factor of 2 and a time resolution of 0.5 ms. Channels affected by RFI were masked and replaced by median values for visualization. See Section \ref{['sec:burst_properties']} for details of the fitting methodology.
• Figure 2: Frequency extent of bursts from FRB20240114A as a function of time for Epochs 2--4. Each vertical line represents an individual burst, color-coded by morphology: simple (blue), complex multi-component (yellow), and drifting (green). The shaded regions indicate flagged frequency ranges due to RFI (light purple) and the instrumental band gap (gray). Side panels show histograms of burst morphologies as a function of time (top) and frequency (right). (We note that an artifical temporal gap is observed in Epoch 2 close to 2000 s due to a technical fault during the observation)
• Figure 3: Frequency evolution of burst widths from GMRT (green circles), Effelsberg (blue circles), and CHIME (red crosses). Distributions at each frequency are shown as violin plots in logarithmic space, with mean values and corresponding uncertainties indicated by black points with error bars. The dashed black line represents the weighted power-law fit across all frequencies (GMRT+Effelsberg), while the solid black line shows the fit using only Effelsberg data. Both fits are performed in log--log space, yielding power-law indices $\alpha$ as indicated in the legend.
• Figure 4: Top: Distribution of raw burst bandwidths in each frequency band shown as violin plots. Gray violins correspond to measured bursts, while blue violins show RFI-extended bursts. The red diamonds mark the scintillation bandwidth predicted by the NE2001 model. Bottom: Fractional bandwidth distributions (burst bandwidth divided by center frequency). Gray violins correspond to measured bursts, while blue violins show RFI-extended bursts. Black points with error bars indicate the mean $\pm$ standard deviation for the measured bursts.
• Figure 5: Top panel: The normalized burst count (per hour) as a function of frequency for the five UBB sub-bands over four observing epochs. For each epoch, two rate distributions are plotted: one calculated with all detected bursts and the other restricted to bursts above a common fluence threshold across all sub-bands (see Section \ref{['sec:burst_rate']} for details). Error bars represent uncertainties estimated from Poisson statistics, with additional error ranges overplotted to reflect expected variations due to scintillation effects (see text for details). Bottom panel: Total on-source time in each observation as a function of MJD for the four UBB epochs. Vertical dashed lines indicate detection epochs reported by CHIME (black) and uGMRT (blue).