Stellar flare study of nearby young moving group members with TESS Data

We analyze TESS data to explore stellar flares and rotational characteristics in members of Nearby Young Moving Groups (NYMGs). Our study focuses on 417 members of NYMGs aged 10-150 Myr. Using detrended light curves from the TESS Science Office Quick-Look Pipeline, coupled with our own additional detrending scheme for fast rotators, we systematically detect and characterize 6,288 stellar flares from 27,416 flare candidates. We analyzed light curves from Cycles 1-4 of the TESS mission, finding that for each NYMG member analyzed, at least one stellar flare was present. Flare candidates are initially detected using the AltaiPony flare package, followed by a recovery flare amplitudes, durations, and local continuum background levels. We examine the relationship between flare energy, age, and mass, finding a reduced flaring rate for late-type stars with age for high energy flares, as well as 5.5 times more flares detected in the 10-minute cadence TESS data compared to 30-minute cadence data. Additionally, flare events with extreme energies (E >= 10^{34} erg) on M-dwarf and solar-type stars, providing implications for further exploration into exoplanet habitability.

💡 Research Summary

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This paper presents a comprehensive analysis of stellar flares and rotation in 417 members of nearby young moving groups (NYMGs) using TESS data from Cycles 1–4 (2018–2023). The authors combine detrended light curves from the TESS Quick‑Look Pipeline (QLP) with a custom Hampel‑based rolling median filter to further remove rotational modulation, especially for fast rotators with periods shorter than 0.6 days. After careful contamination screening based on Gaia G‑band magnitudes and a flux‑magnitude relation, 378 light curves are discarded, leaving 1 862 usable curves, of which 417 belong to NYMG members.

Flare candidates are identified with the AltaiPony “find flares” routine, employing thresholds of 3σ positive excursions, a combined 2σ requirement, and at least one consecutive point (N₁=3, N₂=2, N₃=1). The parameters are tuned on a 10 % subset and then applied uniformly to both 30‑minute and 10‑minute cadence data. Each candidate is subsequently fitted with AltaiPony’s aflare function, which includes a sharp rise, exponential‑like decay, and a quadratic background term. Only events with fitted amplitudes exceeding 3σ above the quiescent level are retained, yielding a final catalog of 6 288 flares out of 27 416 initial candidates.

Flare energies are converted from TESS counts to physical units using three independent methods: (1) a zero‑point based conversion following Ealy et al. (2024), (2) bolometric luminosities derived from Baraffe et al. (2015) stellar models combined with TESS bolometric corrections (Eker & Bakış 2023), and (3) the TESSreduce package (Ridden‑Harper et al. 2021). All three approaches agree within uncertainties; the authors adopt the TESSreduce results for all subsequent analysis.

To assess detection completeness, synthetic flares (30 per light curve) are injected, spanning amplitudes from 10⁻³ to 10² (normalized flux) and durations from 0.0001 to 0.01 days. In total, 48 960 artificial flares are added (27 099 in 30‑minute data, 21 861 in 10‑minute data). Recovery rates exceed 90 % for flares with log₁₀(E/E₀) ≥ ‑2.8, and remain above 70 % down to log₁₀(E/E₀) ≈ ‑3.3. The 10‑minute cadence shows a modestly lower 90 % recovery threshold, confirming its superior sensitivity to low‑energy events.

Statistical analysis of flare frequency distributions (FFDs) reveals clear dependencies on age, stellar mass, and spectral type. M‑type stars (especially M5–M7) dominate the flare count, but the occurrence of high‑energy flares (E > 10³³ erg) declines sharply with age across all types. The authors find that the 10‑minute cadence data produce 5.5 times more detected flares than the 30‑minute data, highlighting the importance of higher temporal resolution for capturing short‑duration events. Notably, flares with energies ≥10³⁴ erg are observed on both M‑dwarfs and solar‑type (G) stars, implying that even relatively mature Sun‑like stars can produce superflares capable of influencing planetary atmospheres.

The paper situates its results within the broader context of stellar magnetic activity and exoplanet habitability. By focusing on NYMGs—coeval, spatially compact groups with well‑constrained ages (10–150 Myr)—the study provides a clean laboratory for probing the evolution of magnetic dynamo processes. The observed decline of high‑energy flare rates with age supports models where stellar spin‑down reduces magnetic field strength, leading to less frequent energetic reconnection events. For M‑dwarf habitable zones, the prevalence of frequent, energetic flares at ages < 100 Myr suggests that early atmospheric erosion or photochemical alteration could be significant, whereas the reduced flare activity at later ages may allow atmospheres to stabilize.

In summary, this work delivers the most extensive flare catalog for young nearby stars to date, validates a robust detection pipeline across two TESS cadences, quantifies the age‑mass‑energy relationships of flares, and underscores the implications for planetary atmospheric evolution and habitability assessments. The methodology and results will serve as a benchmark for future time‑domain surveys and for refining stellar activity models in the context of exoplanetary science.