Water Masers Associated with Circumstellar Shells

Abstract

view Abstract Citations (46) References (53) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Water Masers Associated with Circumstellar Shells Benson, Priscilla J. ; Little-Marenin, Irene R. Abstract We report observational parameters for 62 H2O maser sources, 23 not previously reported, and upper limits of H2O maser emission for 223 nondetected sources. The detected long-period variables (LPVs) are at D < 1.8 kpc for a detection limit of about 1 Jy. The distance adjusted detection rate varies from 18% for Miras variables with P < 200 days to over 50% for stars with P> 300 days and seems to be determined primarily by the amount of material in their associated circumstellar shells, since detected stars have infrared to photospheric flux ratios [flux(12 μm flux(2.2 μm)] > 0.2, whereas nondetected stars have ratios less than 0.3. Stars in the overlap region, 0.2 < r <0.3, may have been observed at the wrong phase. The minimum mass-loss rate needed to sustain detectable H2O maser emission from stars in this program is 0.5 × 10-7 Msun yr-1. The mass-loss rate increases with period. Mira variables with H2O masers have more asymmetric light curves (f = 43) compared to nondetected Miras variables (f = 46). The average H2O maser flux (normalized to 1 kpc) for Mira variables in our observing program with P < 300 days is about 15 Jy km s-1, corresponding to L(H2O)/L(star) ≍ 1 × 10-10 or L(H20)/Lsun 3 x 10-7 and to a photon luminosity 1043-1044 s-1. The low detection rates for Mira variables with P < 200 days is primarily due to the smaller amount of material in their circumstellar shells as compared to the longer period Mira variables and does not appear to be a strong function of their lower metallicities. Publication: The Astrophysical Journal Supplement Series Pub Date: October 1996 DOI: 10.1086/192349 Bibcode: 1996ApJS..106..579B Keywords: STARS: CIRCUMSTELLAR MATTER; MASERS; STARS: MASS LOSS; STARS: VARIABLES: OTHER LONG-PERIOD VARIABLES full text sources ADS | data products SIMBAD (281)