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ABSTRACT We present Very Large Array (VLA) high-resolution observations of the NH(1,1) and NH(2,2) molecular transitions towards the high-mass star-forming region AFGL 437. Our aim was to investigate if the poorly collimated CO molecular outflow previously detected in the region is the result of a projection effect, with no intrinsic bipolarity, as suggested by Gómez et al. We complemented our observations with radio continuum archived data from the VLA at 2 and 3.6 cm, and with unpublished public data at 450 m taken with Submillimetre Common-User Bolometer Array at the James Clerk Maxwell Telescope. Ammonia emission was found mainly in three clumps located at the south and east of the position of the compact infrared cluster of AFGL 437, where the CO outflow seemed to have its origin. One of the NH(1,1) clumps coincides with the maximum of NH(2,2) and with a local peak of emission at 450 m. A near-infrared source (s11) is also found at that position. Our continuum map at 2 cm shows extended elongated emission associated with the infrared source AFGL 437W. This elongated morphology and its spectral index between 3.6 and 2 cm (0.4) suggest the presence of a jet in AFGL 437W. We suggest that several molecular bipolar outflows may exist in the region. The observed CO outflow would be the superposition of those individual outflows, which would explain its low degree of collimation observed at larger scales. [ABSTRACT FROM AUTHOR]

We present five epochs of VLBI water maser observations around the massive protostar Cepheus A HW2 with 0.4 mas (0.3 au) resolution. The main goal of these observations was to follow the evolution of the remarkable water maser linear/arcuate structures found in earlier VLBI observations. Comparing the data of our new epochs of observation with those observed 5 yr before, we find that at 'large' scales of arcsec (700 au) the main regions of maser emission persist, implying that both the surrounding medium and the exciting sources of the masers have been relatively stable during that time-span. However, at smaller scales of arcsec (70 au) we see large changes in the maser structures, particularly in the expanding arcuate structures R4 and R5. R4 traces a nearly elliptical patchy ring of ∼70 mas size (50 au) with expanding motions of ∼5 mas yr (15 km s), consistent with previous results of Gallimore and collaborators. This structure is probably driven by the wind of a still unidentified YSO located at the centre of the ring (∼0.18 arcsec south of HW2). On the other hand, the R5 expanding bubble structure (driven by the wind of a previously identified YSO located ∼0.6 arcsec south of HW2) is currently dissipating in the circumstellar medium and losing its previous degree of symmetry, indicating a very short lived event. In addition, our results reveal, at scales of ∼1 arcsec (700 au), the simultaneous presence of a relatively slow (∼10-70 km s) wide-angle outflow (opening angle of ), traced by the masers, and the fast (∼500 km s) highly collimated radio jet associated with HW2 (opening angle of ), previously observed with the VLA. This simultaneous presence of a wide-angle outflow and a highly collimated jet associated with a massive protostar is similar to what is found in some low-mass YSOs. There are indications that the primary wind(s) from HW2 could be rotating. The implications of these results in the study of the formation of high-mass stars are discussed. [ABSTRACT FROM AUTHOR]

We have studied the kinematics traced by the water masers located at the centre of the planetary nebula (PN) K3–35, using data from previous Very Large Array (VLA) observations. An analysis of the spatial distribution and line-of-sight velocities of the maser spots allows us to identify typical patterns of a rotating and expanding ring in the position–velocity diagrams, according to our kinematical model. We find that the distribution of the masers is compatible with tracing a circular ring with a ≃0.021-arcsec (≃100-au) radius, observed with an inclination angle of 55° with respect to the line of sight. We derive expansion and rotation velocities of 1.4 and 3.1 km s−1, respectively. The orientation of the ring, projected on the plane of the sky, at , is almost orthogonal to the direction of the innermost region of the jet observed in K3–35, suggesting the presence of a disc or torus that may be related to the collimation of the outflow. [ABSTRACT FROM AUTHOR]

We present radio-continuum observations of the planetary nebula (PN) IRAS 17347 − 3139 (one of the only two known to harbour water maser emission), made to derive its spectral index and the turnover frequency of the emission. The spectrum of the source rises in the whole frequency range sampled, from 2.4 to 24.9 GHz, although the spectral index seems to decrease at the highest frequencies ( between 4.3 and 8.9 GHz, and between 16.1 and 24.9 GHz). This suggests a turnover frequency of around 20 GHz (which is unusual among PNe, whose radio emission usually becomes optically thin at frequencies <10 GHz), and a relatively high emission measure . The radio-continuum emission has increased by a factor of ≃1.26 at 8.4 GHz in 13 yr, which can be explained as expansion of the ionized region by a factor of ≃1.12 in radius with a dynamical age of ≃120 yr and at an expansion velocity of . These radio-continuum characteristics, together with the presence of water maser emission and a strong optical extinction, suggest that IRAS 17347 − 3139 is one of the youngest PNe known, with a relatively massive progenitor star. [ABSTRACT FROM AUTHOR]