Poster Presentation

Spectral–Temporal Evolution of Powerful H₂O Maser Flares in the Protostellar System IRAS 16293−2422

Author(s): A.E. Volvach, L.N. Volvach

Presenter: Volvach Alexandr (Radio Astronomy Lab)

We present the results of long-term monitoring of the 22.235 GHz H₂O maser emission in the young protostellar system IRAS 16293−2422 carried out with the Simeiz RT-22 radio telescope during 2019.8–2021.2. A powerful flare complex was detected near the radial velocity of +6 km s^{−1}. The activity persisted for approximately six months and consisted of several short-duration intense flares superimposed on a weaker broad long-lived emission component.

Using spectral–temporal decomposition and dynamic spectral analysis, we separated partially overlapping flare components and investigated their temporal evolution, linewidth variability, and velocity structure. The dynamic spectrum reveals at least two principal velocity groups near 5.88 and 6.05 km s^{−1}, indicating the presence of multiple physically distinct maser condensations within a compact protostellar environment.

A key observational result is the systematic narrowing of spectral linewidths with increasing flux density in the short-duration flares. The observed dependence of (Δv)^{−2} on lnS is consistent with theoretical expectations for unsaturated maser amplification. The derived thermal linewidths correspond to H₂O kinetic temperatures of approximately 200–230 K for the compact flare components, whereas the broader persistent feature implies effective temperatures approaching several thousand Kelvin.

The coexistence of rapidly varying narrow flares and a stable broad emission component suggests a hierarchical amplification structure. We propose that the broad long-lived feature acts as a source of seed radiation subsequently amplified by compact foreground maser condensations aligned along the line of sight. In this geometrical amplification scenario, temporary increases in the effective amplification path length produce rapid exponential growth of the observed maser intensity.

The obtained results demonstrate that powerful water maser flares in IRAS 16293−2422 are generated by multi-component unsaturated amplification within a dynamically structured maser cluster. High-cadence spectral monitoring combined with dynamic spectral analysis therefore provides an effective tool for investigating the internal structure and amplification regimes of maser flares in young stellar objects.