Overall variation of the $H_{2}O$ masers around W Hydrae in 28 years

Abstract

In this paper, we present the distribution of $H_{2}O$ masers associated with the semi-regular variable star W Hydrae (W Hya). We have collected the radio interferometric data of the maser distribution taken with the Very Large Array (VLA), the Kashima-Nobeyama InterFErometer (KNIFE), the Multi-Element Radio Link Network (MERLIN), the VLBI Exploration of Radio Astrometry (VERA), and the combined array of the Korean VLBI Network (KVN) and VERA (KaVA) in order to trace the maser distribution variation in two decades. Even though differences in the sensitivities and angular resolutions of the interferometric observations should be taken into account, we attempt to find possible correlation of the maser distribution with the stellar light curve. Our failure in the measurement of the annual parallax of the masers with VERA is likely caused by the properties of the maser features, which have been spatially resolved by the synthesized beam and survived for only half a year or less. No dependence of the maser spot flux density on its size is found in the KNIFE data, suggesting that maser spot size is determined by the physical boundary, as is expected for a clump affected by outward propagation of a stellar pulsation shock wave, rather than the (spherical) geometry of maser beaming in the maser gas clump.

27 pages, 10 figures, will be published in PASJ

References in corpus (5)

• Imaging the Radio Photospheres of Mira Variables
• Clumpy dust clouds and extended atmosphere of the AGB star W Hya revealed with VLT/SPHERE-ZIMPOL and VLTI/AMBER II. Time variations between pre-maximum and minimum light
• The shock-heated atmosphere of an asymptotic giant branch star resolved by ALMA
• VLBI Astrometry of AGB Variables with VERA -- A Mira Type Variable T Lepus
• Detection of highly excited OH towards AGB stars: A new probe of shocked gas in the extended atmospheres

Cited by in corpus (4)

• East Asian VLBI Network Observations of Active Galactic Nuclei Jets: Imaging with KaVA+Tianma+Nanshan
• Maser emission from the CO envelope of the asymptotic giant branch star W Hydrae
• Long-term Simultaneous Monitoring Observations of SiO and H2O Masers toward the Mira Variable WX Serpentis
• Water vapour masers in long-period variable stars II. The semi-regular variables R Crt and RT Vir