Abstract
Abstract
We report a multiwavelength study of two flaring episodes of the blazar BL Lacertae during MJD 60500–60800 (2024 July 9–2025 May 5). The source reached a daily averaged
γ
-ray flux of (1.03 ± 0.05) ×10
−5
photons cm
−2
s
−1
(
E
> 100 MeV) on MJD 60588 (2024 October 5). Using orbit-binned data from the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope, we identify a minimum flux halving timescale of
τ
= 1.33 ± 0.29 hr. This constrains the upper limit on the size of the
γ
-ray-emitting region to
R
≤ 2.0 × 10
15
cm, as well as its distance from the central supermassive black hole to
R
H
≤ 5.9 × 10
16
cm, assuming a Doppler factor of
δ
= 14.8 derived from the spectral energy distribution (SED) modeling. We find tentative evidence for subminute
γ
-ray variability with a minimum doubling time of 0.7 ± 0.2 min (
p
-value = 0.03). This may originate from an extremely compact region with a size of
R
≤ 1.8 × 10
13
cm, suggesting that the emission arises from magnetohydrodynamic substructures, such as plasmoids within a magnetic reconnection zone. Spectral analysis reveals a significant “softer-when-brighter” trend (
r
= 0.96,
p
= 4.5 × 10
−4
) during the minute-scale flare peaks, indicating a complex interplay between particle acceleration and radiative cooling. The SED is reproduced using a one-zone leptonic model, in which synchrotron self-Compton (SSC) and external Compton (EC) scattering effectively account for the high-energy emissions. The reduced magnetic field strengths and hard electron injection spectral indices observed during the flaring states suggest enhanced particle acceleration efficiency, possibly associated with relativistic magnetic reconnection.