A $ΔR\sim 9.5$ mag Super Flare of An Ultracool Star Detected by $\text{SVOM/GWAC}$ System (2012.14126v1)

Abstract: In this paper, we report the detection and follow-ups of a super stellar flare GWAC\,181229A with an amplitude of $\Delta R\sim$9.5 mag on a M9 type star by $\text{SVOM/GWAC}$ and the dedicated follow-up telescopes. The estimated bolometric energy $E_{bol}$ is $(5.56-9.25)\times10^{34}$ ergs, which places the event to be one of the most powerful flares on ultracool stars. The magnetic strength is inferred to be (3.6-4.7) kG. Thanks to the sampling with a cadence of 15 seconds, a new component near the peak time with a very steep decay is detected in the $R$-band light curve, followed by the two-component flare template given by Davenport et al. (2014). An effective temperature of $5340\pm40$ K is measured by a blackbody shape fitting to the spectrum at the shallower phase during the flare. The filling factors of the flare are estimated to be $\sim$30\% and 19\% at the peak time and at 54 min after the first detection. The detection of the particular event with large amplitude, huge-emitted energy and a new component demonstrates that a high cadence sky monitoring cooperating with fast follow-up observations is very essential for understanding the violent magnetic activity.

• The paper presents the detection of a 9.5-mag super flare on an M9 ultracool star using high-cadence data from the SVOM/GWAC system.
• It quantifies a bolometric energy of (5.56–9.25)×10^34 ergs and estimates magnetic field strengths up to 4.7 kG.
• A novel multi-component decay model is employed to reveal distinct cooling phases, enhancing our understanding of stellar magnetic reconnection.

A Study of a Super Flare on an Ultracool Star Detected by the SVOM/GWAC System

The paper "A $\Delta R\sim 9.5$ mag Super Flare of An Ultracool Star Detected by $\text{SVOM/GWAC}$ System" presents a detailed analysis of an extraordinary flare event on an M9 type ultracool star. This research utilizes data obtained from the Ground Wide Angle Cameras (GWAC) system, part of the SVOM mission, to achieve a high cadence, wide-field astronomical survey focal on transient events.

Summary of Key Findings

• Observation and Detected Event: The paper reports the detection of a stellar flare designated as GWAC\,181229A, which exhibited a peak brightness of 13.5 magnitudes in the R-band and an impressive total amplitude of $\Delta R\sim 9.5$ magnitudes. This makes it one of the most luminous flares on ultracool stars reported to date.
• Energy and Magnitude of the Flare: The total estimated bolometric energy ranges from $(5.56-9.25) \times 10^{34}$ ergs, indicating a flare of significant energetic output. The analysis derives maximum magnetic field strengths of approximately 3.6 to 4.7 kG, which are consistent with the presence of strong magnetic activities often observed in ultracool stars.
• Multi-Component Decay Phase: The decay phase of the flare required a model that incorporates three distinct components. This refined approach deviates from the conventional two-phase model (impulsive and gradual) predominantly applied in earlier studies. Each decay step indicates different stages of the cooling process and involves varying physical characteristics.
• Spectroscopic Observations: A spectrum obtained during the event's shallower decay phase yielded an effective blackbody temperature of $5340 \pm 40$ K, which is used to further elucidate the thermodynamic processes at play during the flare's life cycle.
• Implications on Stellar Activity Understanding: Ultracool dwarfs, like the star in this paper, are valuable for understanding stellar magnetic activities, especially given their fully convective interiors which are likely to contribute to non-solar-type dynamo processes.

Implications and Future Directions

The discovery and analysis of GWAC\,181229A elucidates several implications:

1. Stellar Magnetism: The significant flare energies and rapid phase transitions observed reinforce the understanding of magnetic reconnections as a primary driver of flare activities. The insights derived could be instrumental in recalibrating models of stellar magnetic fields, particularly for ultracool dwarfs.
2. Astrobiological Impact: Understanding flare properties of ultracool stars holds importance for assessing the habitability of orbiting exoplanets. These energetic events represent a potential hazard to atmospheric integrity and biological systems.
3. Technological Symbiosis: The combination of high-cadence wide-field monitoring with rapid follow-up systems demonstrates the efficacy of the GWAC system in capturing transient phenomena. This technological synergy is crucial for capturing high-amplitude, short-duration flaring events.
4. Expanding Stellar Models: Observations like these expand empirical data needed for developing comprehensive theories surrounding flare genesis and characteristics in low-mass stars. This paper's approach may inspire further investigations into spectral and temporal characteristics of such flares.

Future efforts should focus on increasing observational coverage through additional deployments of synchronized detection units, enhancing detection thresholds for more comprehensive afterglow tracking, and improving spectroscopic temporal resolution to refine models of post-flare decay dynamics. As these systems evolve, an enriched understanding of stellar behaviors across the H-R diagram may be realized, encapsulating both rapid energetic processes and longer-term magnetic evolution.