Evolution of the Outflow in the Water Fountain Source IRAS 18043-2116

We present the spectral and spatial evolution of H2O masers associated with the water fountain source IRAS 18043-2116, found in observations with the Nobeyama 45 m Telescope and the Australia Telescope Compact Array. We have found new highest-velocity components of the H2O masers (at the redshifted side V (LSR) similar or equal to 376 km s(-1) and at the blueshifted side V (LSR) similar or equal to -165 km s(-1)), and the resulting velocity spread of similar or equal to 540 km s(-1) breaks the speed record of fast jets/outflows in this type of sources. The locations of those components have offsets from the axis joining the two major maser clusters, indicating a large opening angle of the outflow (similar to 60 degrees). The evolution of the maser cluster separation of similar to 2.9 mas yr(-1) and the compact (similar to 0.\u27\u27 2) CO emission source mapped with the Atacama Large Millimeter-submillimeter Array suggest a very short (similar to 30 yr) timescale of the outflow. We also confirmed an increase in the flux density of the 22 GHz continuum source. The properties of the jet and the continuum sources and their possible evolution in the transition to the planetary nebula phase are further discussed

Discovery of SiO Masers in the "Water Fountain" Source IRAS 16552−3050

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.In this paper, we report new detections of SiO v = 1 and v = 2 J = 1 → 0 masers in the "water fountain" source IRAS 16552−3050, which was observed with the Nobeyama 45 m telescope during 2021 March–April. Water fountains are evolved stars whose H2O maser spectra trace high-velocity outflows of >100 km s−1. This is the second known case of SiO masers in a water fountain, after their prototypical source, W 43A. These SiO masers should shed light on the evolutionary status of this category of evolved stars, which are likely to be at the end of the asymptotic giant branch phase, when the star exhibits the most copious stellar mass loss, followed by development of the complicated morphologies of planetary nebulae. The origin of a large (up to 25 km s−1) velocity offset of the SiO masers with respect to the systemic velocity derived from the spectrum of CO J = 2 → 1 line is discussed here. © 2022. The American Astronomical Society. All rights reserved.he Nobeyama 45 m radio telescope is operated by Nobeyama Radio Observatory, a branch of the National Astronomical Observatory of Japan (NAOJ), National Institutes of Natural Sciences. We used the data taken in the project 2018.1.00250.S of ALMA, which is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. This publication also makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. H.I. is supported by JSPS KAKENHI grant No. JP 16H02167. J.F.G. acknowledges support from the State Agency for Research (AEI/10.13039/501100011033) of the Spanish MCIU, through grant PID2020-114461GB-I00 and the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709).Peer reviewe

Water and silicon-monoxide masers monitored towards the water fountain sources

We have investigated the evolution of 12 water fountain sources in real time in the accompanying H2O 2o and SiO masers through our FLASHING (Finest Legacy Acquisitions of SiO-/ H2O 2o-maser Ignitions by Nobeyama Generation) project. It has been confirmed that these masers are excellent probes of new jet blob ejections, acceleration of the material supplied from the parental circumstellar envelope and entrained by the stellar jets yielding its deceleration. Possible periodic variations of the maser emission, reflecting properties of the central dying stars or binary systems, will be further investigated