VLBI Observations of the Water Masers near LkHα 234 and BD +40 4124

2005 ◽  
Vol 130 (6) ◽  
pp. 2732-2744 ◽  
Author(s):  
Kevin B. Marvel
Keyword(s):  
Vlbi Observations ◽  
Water Masers

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 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 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.

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.

Maser Emission in G 339.884−1.259

2017 ◽  
Vol 13 (S336) ◽  
pp. 334-335
Author(s):  
V. Krishnan ◽  
L. Moscadelli ◽  
S. P. Ellingsen ◽  
H. E. Bignall ◽  
S. L. Breen ◽  
...  
Keyword(s):  
Star Formation ◽  
High Mass ◽  
Mass Star ◽  
Proper Motions ◽  
Star Formation Region ◽  
Formation Region ◽  
Gas Kinematics ◽  
Long Baseline ◽  
Vlbi Observations ◽  
Water Masers

AbstractWe present multi–epoch VLBI observations of the methanol and water masers in the high–mass star formation region G 339.884−1.259, made using the Australian Long Baseline Array (LBA). Our sub–milliarcsecond precision measurements trace the proper motions of individual maser features in the plane of the sky. When combined with the direct line–of–sight radial velocity (vlsr), these measure the 3 D gas kinematics of the associated high–mass star formation region, allowing us to probe the dynamical processes to within 1000 AU of the core.

scholarly journals Parameters of Disks from VLBI Observations

1997 ◽  
Vol 163 ◽  
pp. 591-599
Author(s):  
R. C. Walker
Keyword(s):  
Accretion Disks ◽  
Imaging Technique ◽  
Direct Imaging ◽  
Important Data ◽  
Outer Disk ◽  
Vlbi Observations ◽  
Water Masers ◽  
Ngc 1275

AbstractVLBI provides the only direct imaging technique currently available that is able to resolve even the outer parts of accretion disks. Recent observations of water masers in NGC 4258 and of free-free absorption of counterjet radiation in NGC 1275 are the best examples of where VLBI has provided important data on the parameters of disks. Other observations are now being made of similar sources. In addition, recent VLBI observations of HI absorption promise to add yet more constraints on the outer disk regions.

scholarly journals VLBI Observations of Water Masers in Onsala 1: Massive Binary Star-Forming Site?

2008 ◽  
Vol 60 (2) ◽  
pp. 183-190 ◽  
Author(s):  
Takumi Nagayama ◽  
Akiharu Nakagawa ◽  
Hiroshi Imai ◽  
Toshihiro Omodaka ◽  
Yoshiaki Sofue
Keyword(s):  
Binary Star ◽  
Star Forming ◽  
Vlbi Observations ◽  
Water Masers

A large rotating structure around AB Doradus A at VLBI scale

2019 ◽  
Vol 15 (S354) ◽  
pp. 189-194
Author(s):  
J. B. Climent ◽  
J. C. Guirado ◽  
R. Azulay ◽  
J. M. Marcaide
Keyword(s):  
Magnetic Reconnection ◽  
Main Sequence ◽  
Complex Structure ◽  
Main Sequence Star ◽  
Polar Cap ◽  
Vlbi Observations ◽  
Rotating Structure ◽  
Source Structure ◽  
Expected Position

AbstractWe report the results of three VLBI observations of the pre-main-sequence star AB Doradus A at 8.4 GHz. With almost three years between consecutive observations, we found a complex structure at the expected position of this star for all epochs. Maps at epochs 2007 and 2010 show a double core-halo morphology while the 2013 map reveals three emission peaks with separations between 5 and 18 stellar radii. Furthermore, all maps show a clear variation of the source structure within the observing time. We consider a number of hypothesis in order to explain such observations, mainly: magnetic reconnection in loops on the polar cap, a more general loop scenario and a close companion to AB Dor A.

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