Long-term Simultaneous 2.25/8.60 GHz Monitoring of the Newly Discovered Repeating FRB 20240114A

Abstract We report on the simultaneous monitoring of the repeating fast radio burst (FRB) 20240114A at 2.25 and 8.60 GHz, conducted 66 times between 2024 January 29 and 2025 February 15 with the Shanghai Tianma Radio Telescope. In about 180 hr of observation, we detected 155 bursts at 2.25 GHz above a fluence threshold of 0.72 Jy ms but none at 8.60 GHz above a fluence threshold of 0.27 Jy ms. FRB 20240114A exhibited frequency-dependent activity, as evidenced by the nondetections in 14.3 hr of observations at 2.25 GHz prior to 2024 February 24, despite its reported activity below 2 GHz. In contrast to its low-activity state reported below 1.4 GHz between 2024 June and December, FRB 20240114A exhibited high activity at 2.25 GHz in 2024 July with a mean burst rate of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>1.7</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.16</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.18</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="1em"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">hr</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> , followed by a low-activity state. We also detected a short-term reactivation at 2.25 GHz around 2025 January 20, about 2 weeks after renewed activity was reported below 1.4 GHz by other telescopes. The median burst width at 2.25 GHz is 3 ms, which is narrower than that at lower frequencies. The waiting time distribution peaks at 1019 s, and bursts arrive on hourly timescales consistent with a Poisson process. The isotropic-equivalent energy of the bursts spans 10 37 –10 39 erg. The distribution of burst energy above the completeness threshold (7.5 × 10 37 erg) follows a power-law relation with an index of γ = −1.20 ± 0.03 ± 0.02. Finally, we find that FRB 20240114A is at least 2 orders of magnitude less active at 8.60 GHz than at 2.25 GHz, and we constrain the broadband spectra of the detected bursts.