Building on the detection of the J = 7−6 SiO maser emission in both the v = 1 and v = 2 vibrational states towards the symbiotic Mira, R Aquarii, we have used the James Clerk Maxwell Telescope to study the changes in the SiO maser features from R Aqr over a stellar pulsational period. The observations, complemented by contemporaneous data taken at 86GHz, represent a test of the popular thermal-...

We present a survey in the 6 16 − 5 23 rotational H 2 O transition toward 33 galactic ultracompact HII regions. Maser emission is detected toward 18 of these sources; two are new detections. High quality spectra are provided for all 18 sources. We discuss the detection rate of this survey and the correlation of various maser properties with other physical parameters. In addition, we report wide...

Context. Water maser emission is a powerful tracer of the presence of embedded sources in dense clouds since it requires elevated temperatures (>100 K) and densities (>107 cm−3) that can be found in circumstellar disks and/or jets/outflows associated with Young Stellar Objects. Bright rimmed clouds compressed by ionization fronts from nearby massive stars are considered good examples of externa...

Context. The role of magnetic fields during high-mass star formation is a matter of fierce debate, yet only a few direct probes of magnetic field strengths are available. Aims. The magnetic field is detected in a number of massive star-forming regions through polarization observations of 6.7 GHz methanol masers. Although these masers are the most abundant of the maser species occurring during h...

(Pseudo) radiative pumprate of OH 1612MHz masers is defined for a sample of 44 OH/IR sources (infrared sources with OH 1612MHz maser), irrespective of the real maser pumping mechanisms. The correlation between the (pseudo) maser pumprates and the evolutionary status of the maser sources reveals that the radiative pumprates of stellar OH masers are nearly fixed, which agrees with the theoretical...

Sub-arcsecond observations using the Very Large Array (VLA) are presented of low-luminosity H2O maser emission in M82, M51, and NGC4051. New maser features have been detected within the M82 starburst complex. They are largely associated with star-forming activity such as optically-identified starburst-driven winds, H ii regions, or the early phase of star-formation in the galaxy. H2O maser in M...

We have investigated the influence of several line overlaps between 28 SiO , 29 SiO and 30 SiO on maser emission from the envelopes of late-type stars using the Large Velocity Gradient radiative transfer formalism modified to account for overlaps. Our model includes: (i) 40 rotational levels for each of the v = 0 to 4 vibrational states and each isotopic species; (ii) collisions with molecular ...

We present the first result of VLBI observations of the blueshifted water maser emission from the type 2 Seyfert galaxy NGC5793, which we combine with new and previous VLBI observations of continuum emission at 1.7, 5.0, 8.4, 15, and 22 GHz. Maser emission was detected earlier in single-dish observations and found to have both redand blueshifted features relative to the systemic velocity. We co...