FLASHING: Project overview

This paper describes an overview of the FLASHING (Finest Legacy Acquisitions of SiO-/H<SUB>2</SUB>O-maser Ignitions by the Nobeyama Generation) project promoted using the 45 m telescope of Nobeyama Radio Observatory, which aims to intensively monitor H<SUB>2</SUB>O (at 22 GHz) and SiO (at 43 GHz) masers associated with so-called "water fountain" sources. Here we show scientific results based on the data taken in the first five seasons of FLASHING, from 2018 December to 2023 April. We show the evolution of the H<SUB>2</SUB>O maser spectra, discovering new spectral components that break 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 newly detect it in one source and find that it is no longer present in another source. This implies that the jets from these water fountains can be accelerated or decelerated, and show how circumstellar envelopes are destroyed.