scholarly journals VLBI Observations of Water Masers in the Circumstellar Envelope of IRC$ +$60169

2002 ◽  
Vol 54 (5) ◽  
pp. 757-764 ◽  
Author(s):  
Hiroshi Sudou ◽  
Toshihiro Omodaka ◽  
Hiroshi Imai ◽  
Tetsuo Sasao ◽  
Hiroshi Takaba ◽  
...  
Keyword(s):  
Circumstellar Envelope ◽  
Vlbi Observations ◽  
Water Masers

scholarly journals First detection of Zeeman splitting of water masers in circumstellar shells

2002 ◽  
Vol 206 ◽  
pp. 375-378
Author(s):  
Wouter Vlemmings ◽  
Phil Diamond ◽  
Huib Jan van Langevelde
Keyword(s):  
Zeeman Splitting ◽  
Central Star ◽  
Rotational Transition ◽  
Circumstellar Envelope ◽  
Circumstellar Envelopes ◽  
First Results ◽  
Circumstellar Shells ◽  
Water Masers ◽  
The Magnetic Field ◽  
Density Regime

The strength and structure of the magnetic fields in circumstellar envelopes have been measured through polarization observations of OH and SiO masers. Here we present the first results obtained by observing the circular polarization of the H2O masers using VLBI. SiO masers are probes of the high temperature and density regime close to the central star. OH masers are found at much lower densities and temperatures, generally much further out in the circumstellar envelope. The detection of the Zeeman splitting of the (616-523) rotational transition of the H2O maser allows us to determine the magnetic field strength in the intermediate temperature and density regime.

scholarly journals Massive star-formation in G24.78+0.08 studied by means of maser VLBI and thermal interferometric observations

2007 ◽  
Vol 3 (S242) ◽  
pp. 135-139
Author(s):  
L. Moscadelli ◽  
C. Goddi ◽  
R. Cesaroni ◽  
M. T. Beltràn
Keyword(s):  
Star Formation ◽  
Physical Properties ◽  
Massive Star ◽  
Massive Star Formation ◽  
Star Forming ◽  
Gas Kinematics ◽  
Vlbi Observations ◽  
Water Masers

AbstractThis work presents the results of VLBI observations of 6.7 GHz methanol and 22.2 GHz water masers towards the mm core A in the massive star-forming region G24.78+0.08. Comparing the maser with previous millimeter interferometric and recent continuum VLA observations, the physical properties and the gas kinematics of the G24 A core on linear scales from ~100 AU to ~0.1 pc are determined.

scholarly journals First detection of vibrationally excited water masers toward embedded young stellar objects

2002 ◽  
Vol 206 ◽  
pp. 55-58
Author(s):  
Tarja Liljeström ◽  
Anders Winnberg ◽  
Roy Booth
Keyword(s):  
Young Stellar Objects ◽  
Circumstellar Envelope ◽  
Vibrationally Excited ◽  
Stellar Objects ◽  
Maser Emission ◽  
Hot Gas ◽  
Water Masers ◽  
Water Maser

We report the first detection of vibrationally excited water maser emission in the circumstellar envelope of two young stellar objects (W51M, Z CMa). The results suggest that the observed 96 GHz water maser emission traces hot gas in an accretional stage of the protostellar evolution.

scholarly journals Water masers in bowshocks: Addressing the radiation pressure problem of massive star formation

2017 ◽  
Vol 13 (S336) ◽  
pp. 263-266
Author(s):  
Ross A. Burns
Keyword(s):  
Star Formation ◽  
Radiation Pressure ◽  
Massive Star ◽  
Massive Stars ◽  
Massive Star Formation ◽  
Vlbi Observations ◽  
History Of ◽  
Water Masers

AbstractEjection activities in S255IR-SMA1 and AFGL 5142 were investigated by multi-epoch VLBI observations of 22 GHz water masers, tracing bowshocks leading collimated jets. The history of ejections, revealed by the 3D maser motions and supplemented by the literature, suggests that these massive stars formed by episodic accretion, inferred via the accretion-ejection connection. This contribution centers on the role of episodic accretion in overcoming the radiation pressure problem of massive star formation - with maser VLBI and single-dish observations providing essential observational tools.

Proper Motions of Water Masers in Circumstellar Shells

1998 ◽  
Vol 164 ◽  
pp. 253-254
Author(s):  
K. B. Marvel ◽  
P. J. Diamond ◽  
A. J. Kemball
Keyword(s):  
Circumstellar Envelope ◽  
Proper Motions ◽  
Complex Region ◽  
Circumstellar Shells ◽  
Water Masers ◽  
Water Maser

AbstractWe present measurements of proper motions for circumstellar water maser observations obtained with the VLBA. Results of the observations and modeling indicate that the water masers exist in a kinematically complex region of the circumstellar envelope. A change in position of the maser spots as a function of velocity is discussed.

scholarly journals 9.11. Global VLBI observations of the central region in NGC 3079

1998 ◽  
Vol 184 ◽  
pp. 403-404
Author(s):  
Satoko Satoh ◽  
M. Inoue ◽  
K.M. Shibata ◽  
S. Kameno ◽  
V. Migenes ◽  
...  
Keyword(s):  
Nuclear Region ◽  
Vlbi Observations ◽  
Systemic Velocity ◽  
Unique Object ◽  
The Galaxy ◽  
Continuum Structure ◽  
Water Masers ◽  
Velocity Drift ◽  
Absorption Features ◽  
Water Maser

NGC 3079 has very luminous water megamaser from the nucleus, the peak of the spectrum being blueshifted by 180 km s−1 from the systemic velocity of the galaxy (Vsys = 1131 km s−1) (Henkel et al. 1984, Haschick & Baan 1985). Core-jet like continuum structure is also found in the nuclear region (Irwin & Seaquist 1988). No velocity drift for main features of water maser (VLSR = 941–975 km s−1) has been shown (Nakai et al. 1995). However, the drift was recently detected for the maser of 1190 km s−1 (Nakai 1997). HI and OH absorptions are detected in the nucleus (Haschick & Baan 1985, Irwin & Seaquist 1991). Thus this galaxy is very unique object to investigate water masers, continuum structure and absorption features all together with VLBI.

scholarly journals VLBI observations of H2O and CH3OH masers in two high-mass YSOs

2007 ◽  
Vol 3 (S242) ◽  
pp. 152-153
Author(s):  
C. Goddi ◽  
L. Moscadelli ◽  
A. Sanna ◽  
R. Cesaroni ◽  
V. Minier
Keyword(s):  
Large Scale ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Disk Wind ◽  
Star Forming Regions ◽  
Vlbi Observations ◽  
Circumstellar Gas ◽  
Methanol Masers ◽  
Water Masers

AbstractWe have conducted phase-reference VLBI observations of H2O and CH3OH masers toward two high-mass star forming regions, Sh 2-255 IR and AFGL 5142. In Sh 2-255 infrared water masers are aligned along a direction close to the orientation of a large scale H2 jet, tracing possibly shocked material in a precessing jet, or, alternatively, the disk-wind emerging from the disk atmosphere. In AFGL 5142 water masers trace expansion at the base of a protostellar jet, whilst methanol masers are more probably tracing infalling than outflowing gas. Our results suggest that water and methanol masers trace different kinematic structures in the circumstellar gas.

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