Abstract:
We present the first observational evidence of multiple slow acoustic oscillations in the post-flaring loops of
the corona of Proxima Centauri using XMM-Newton observations. We find the signature of periodic oscillations
localized in the decay phase of the flare in its soft (0.3–10.0 keV) X-ray emissions. Using the standard wavelet tool,
we find multiple periodicities of 1261 s and 687 s. These bursty oscillations persist for durations of 90 minutes
and 50 minutes, respectively, for more than three cycles. The intensity oscillations with a period of 1261 s may
be the signature of the fundamental mode of slow magnetoacoustic waves with a phase speed of 119 km s⁻¹ in a
loop of length 7.5 × 10⁹ cm, which is initially heated, producing the flare peak temperature of 33 MK and later
cooled down in the decay phase and maintained at an average temperature of 7.2 MK. The other period of 687 s
may be associated with the first overtone of slow magnetoacoustic oscillations in the flaring loop. The fundamental
mode oscillations show dissipation with a damping time of 47 minutes. The period ratio P₁ /P₂ is found to be 1.83,
indicating that such oscillations are most likely excited in longitudinal density stratified stellar loops. We estimate
the density scale height of the stellar loop system as ∼23 Mm, which is smaller than the hydrostatic scale height of
the hot loop system, and implies the existence of non-equilibrium conditions.
