Open AccessA comparison of OH and H 2 O maser properties of Mira and semiregular variable stars
Author(s) -
Szymczak M.,
Le Squeren A. M.
Publication year - 1999
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1999.02321.x
Subject(s) - maser , physics , astrophysics , stars , luminosity , astronomy , variable star , redshift , galaxy
A sample of 17 Miras and nine semiregular variable stars was simultaneously observed in the OH and H 2 O maser lines with sensitivities of 0.15 and 0.6 Jy, respectively. One new H 2 O source was detected. Among Miras the H 2 O maser luminosity is well correlated with the OH maser luminosity. The ratio of H 2 O to OH maser luminosities decreases by about four orders of magnitude from the semiregulars to the Miras as a result of an increase in the mass‐loss rate. Some semiregulars have maser properties typical of Mira stars. H 2 O emission is most likely to be detected from Miras at velocities close to the stellar velocity, while emission at blueshifted velocities dominates the detections from semiregulars. OH emission from the semiregulars usually occurs at greater redshifts and blueshifts with respect to the stellar velocities than OH emission observed from the Miras. The differences in the average composite maser profiles in both groups of stars can be related to the velocity gradients in the maser regions. It is suggested that some semiregular variables with maser emission may be in a later stage of stellar evolution than the Miras.