FLASHING: Project Overview

TL;DR

The FLASHING project uses the Nobeyama 45m telescope to monitor water and SiO masers in water fountain sources, revealing maser spectral evolution, jet acceleration/deceleration, and circumstellar envelope changes over five seasons.

Contribution

This study provides new observational insights into maser spectral evolution and jet dynamics in water fountain sources through multi-season monitoring.

Findings

Detection of new spectral components indicating jet speed changes

Observation of SiO maser emission appearing and disappearing in sources

Evidence of jet acceleration and deceleration affecting circumstellar environments

Abstract

This paper describes the overview of the FLASHING (Finest Legacy Acquisitions of SiO-/ H$_2$O-maser Ignitions by the Nobeyama Generation) project promoted using the 45 m telescope of Nobeyama Radio Observatory, which aims to intensively monitor H$_2$O (22 GHz) and SiO (43 GHz) masers associated with so-called "water fountain" sources. Here we show scientific results on the basis of the data taken in for the first five seasons of FLASHING, from 2018 December to 2023 April). We have found the evolution of the H$_2$O maser spectra, such as new spectral components breaking the record of the jet's top speed and/or systematic velocity drifts in the spectrum indicating acceleration or deceleration of the maser gas clumps. For the 43 GHz SiO maser emission, we have found its new detection in a source while its permanent disappearance in other source. Our finding may imply that the jets from these water fountains can be accelerated or decelerated, and show how cicumstellar envelopes have been destroyed.