scholarly journals Intrinsic Sizes of the W3 (OH) Masers via Short Time Scale Variability

2012 ◽  
Vol 8 (S287) ◽  
pp. 465-469 ◽  
Author(s):  
Tanmoy Laskar ◽  
W. M. Goss ◽  
B. Ashley Zauderer
Keyword(s):  
Time Scale ◽  
High Mass ◽  
Short Time Scale ◽  
Mass Star ◽  
Star Forming ◽  
Long Baseline ◽  
Interstellar Scintillation ◽  
Maser Line ◽  
Short Time ◽  
Very Long Baseline Array

AbstractWe present a study of short time-scale variability of OH masers within a contiguous 15-hour Very Long Baseline Array observation of the high-mass star-forming region, W3 (OH). With an angular resolution of ~7 mas and a velocity resolution of 53 m s−1, we isolate emission from masers in the field into individual Gaussian-shaped components, each a few milliarcseconds in size. We compute dynamic spectra for individual maser features with a time resolution of 1 minute by fitting for the flux density of all sources in the field simultaneously in the uv-domain. We isolate intrinsic maser variability from interstellar scintillation and instrumental effects. We find fluctuations in the maser line shape on time scales of 5 to 20 minutes, corresponding to maser column lengths of 0.5 to 2.0 Astronomical Units.

scholarly journals The distance to G59.7+0.1 and W3OH

2007 ◽  
Vol 3 (S248) ◽  
pp. 214-216
Author(s):  
Y. Xu ◽  
M. J. Reid ◽  
K. M. Menten ◽  
X. W. Zheng ◽  
A. Brunthaler ◽  
...  
Keyword(s):  
High Mass ◽  
Radio Sources ◽  
Mass Star ◽  
Proper Motions ◽  
Extragalactic Radio Sources ◽  
Star Forming ◽  
Long Baseline ◽  
Methanol Masers ◽  
Very Long Baseline Array

AbstractWe have measured the distance to the high-mass star-forming region G59.7+0.1 (IRAS 19410+2336) and W3OH. Their distances, 2.20 ± 0.11 kpc and 1.95 ± 0.04 kpc, respectively, were determined by triangulation using Very Long Baseline Array (VLBA) observations of 12.2 GHz methanol masers phase-referenced to compact extragalactic radio sources. In addition to the distances, we have also obtained their proper motions.

scholarly journals The distance to G59.7+0.1

2007 ◽  
Vol 3 (S242) ◽  
pp. 374-375
Author(s):  
Y. Xu ◽  
M. J. Reid ◽  
K. M. Menten ◽  
A. Brunthaler ◽  
X. W. Zheng ◽  
...  
Keyword(s):  
High Mass ◽  
Radio Sources ◽  
Mass Star ◽  
Extragalactic Radio Sources ◽  
Star Forming ◽  
Long Baseline ◽  
Infra Red ◽  
Methanol Masers ◽  
Very Long Baseline Array

AbstractWe have measured the distance to the high-mass star-forming region G59.7+0.1, which harbors the far-infra-red source IRAS 19410+2336. The distance is 2.20 ± 0.11 kpc and was determined by triangulation using Very Long Baseline Array (VLBA) observations of 12.2 GHz methanol masers phase-referenced to two compact extragalactic radio sources.

scholarly journals Parallax of Star-forming Region G027.22+0.14

2022 ◽  
Vol 163 (2) ◽  
pp. 54
Author(s):  
S. B. Bian ◽  
Y. Xu ◽  
J. J. Li ◽  
Y. W. Wu ◽  
B. Zhang ◽  
...  
Keyword(s):  
Proper Motion ◽  
High Mass ◽  
Mass Star ◽  
Proper Motions ◽  
Star Forming ◽  
Long Baseline ◽  
Trigonometric Parallax ◽  
Peculiar Motion ◽  
Very Long Baseline Array ◽  
Lower Luminosity

Abstract Using the Very Long Baseline Array, we measured the trigonometric parallax and proper motions toward a 6.7 GHz methanol maser in the distant high-mass star-forming region G027.22+0.14. The distance of this source is determined to be 6.3 − 0.5 + 0.6 kpc. Combining its Galactic coordinates, radial velocity, and proper motion, we assign G027.22+0.14 to the far portion of the Norma arm. The low peculiar motion and lower luminosity of G027.22+0.14 support the conjecture by Immer et al. that low-luminosity sources tend to have low peculiar motions.

scholarly journals Methanol and water maser observations separate disc and outflow sources in IRAS 19410+2336

2020 ◽  
Vol 493 (3) ◽  
pp. 4442-4452 ◽  
Author(s):  
M S Darwish ◽  
K A Edris ◽  
A M S Richards ◽  
S Etoka ◽  
M S Saad ◽  
...  
Keyword(s):  
Flux Density ◽  
High Mass ◽  
High Angular Resolution ◽  
Mass Star ◽  
Star Forming ◽  
Peak Flux ◽  
Maser Line ◽  
Methanol Masers ◽  
Water Masers ◽  
Water Maser

ABSTRACT We investigate the kinematics of high-mass protostellar objects within the high-mass star-forming region IRAS 19410+2336. We performed high angular resolution observations of 6.7-GHz methanol and 22 GHz water masers using the Multi-Element Radio Linked Interferometer Network (MERLIN) and e-MERLIN interferometers. The 6.7-GHz methanol maser emission line was detected within the ∼16–27 km s−1 velocity range with a peak flux density ∼50 Jy. The maser spots are spread over ∼1.3 arcsec on the sky, corresponding to ∼2800 au at a distance of 2.16 kpc. These are the first astrometric measurements at 6.7 GHz in IRAS 19410+2336. The 22-GHz water maser line was imaged in 2005 and 2019 (the latter with good astrometry). Its velocities range from 13 to ∼29 km s−1. The peak flux density was found to be 18.7 and 13.487 Jy in 2005 and 2019, respectively. The distribution of the water maser components is up to 165 mas, ∼350 au at 2.16 kpc. We find that the Eastern methanol masers most probably trace outflows from the region of millimetre source mm1. The water masers to the West lie in a disc (flared or interacting with outflow/infall) around another more evolved millimetre source (13-s). The maser distribution suggests that the disc lies at an angle of 60° or more to the plane of the sky and the observed line-of-sight velocities then suggest an enclosed mass between 44 M⊙ and as little as 11 M⊙ if the disc is edge-on. The Western methanol masers may be infalling.

scholarly journals Rotational parallaxes of nearby galaxies

2012 ◽  
Vol 8 (S289) ◽  
pp. 226-226
Author(s):  
Andreas Brunthaler
Keyword(s):  
High Mass ◽  
Mass Star ◽  
Proper Motions ◽  
Star Forming ◽  
Star Forming Regions ◽  
Long Baseline ◽  
First Results ◽  
Systematic Effects ◽  
Nearby Galaxies ◽  
Water Masers

AbstractAccurate geometric distances, which are inherently free of systematic effects are of very great importance for an independent recalibration of extragalactic distance estimators. Local Group galaxies are close enough for both primary and secondary distance indicators to be readily isolated in ground- and space-based observations. Astrometric accuracies of a few micro-arcseconds based on Very Long Baseline Interferometry (VLBI) observations of water masers in high-mass star-forming regions in nearby galaxies allow a measurement of the proper motions of these masers. Since these high-mass star-forming regions rotate with the galaxies, one can deduce a rotational parallax by comparing the known rotation curve with the proper motions of the masers. I provide an update of our previous rotation parallax of M33 and show first results of observations of the recently discovered water masers in the Andromeda galaxy (M31).

scholarly journals VLBI maser kinematics in high-mass SFRs: G23.01–0.41

2012 ◽  
Vol 8 (S287) ◽  
pp. 396-400 ◽  
Author(s):  
Alberto Sanna ◽  
Luca Moscadelli ◽  
Riccardo Cesaroni ◽  
Ciriaco Goddi
Keyword(s):  
Velocity Field ◽  
Very Long Baseline Interferometry ◽  
Young Stellar Objects ◽  
High Mass ◽  
Mass Star ◽  
Stellar Objects ◽  
Star Forming ◽  
3 Dimensional ◽  
Long Baseline ◽  
Molecular Core

AbstractVery Long Baseline Interferometry studies of different maser species observed at multiple epochs allow complementary measurements of the 3-dimensional velocity field of gas close (≲ 103 AU) to massive young stellar objects. Here, we review our recent results toward the high-mass star-forming region G23.01–0.41, where all the strongest molecular maser transitions known to date cluster within 2000 AU from the center of an hot molecular core and are associated with a so called extended green object. The overall maser kinematics reveals a common outflowing motion from a central object; the details of the spatial distribution and velocity field of each maser species hint at the presence of different dynamical structures: a collimated jet, a wide-angle wind, and a flattened rotating core. We further compare the simultaneous presence of maser emission from different molecular species with a recent evolutionary sequence for masers associated with massive young stellar objects.

scholarly journals Multiline observations of S255IR with ALMA

2017 ◽  
Vol 13 (S332) ◽  
pp. 270-273 ◽  
Author(s):  
Igor Zinchenko ◽  
Sheng-Yuan Liu ◽  
Yu-Nung Su ◽  
Petr Zemlyanukha
Keyword(s):  
High Resolution ◽  
High Mass ◽  
Mass Star ◽  
Present Sample ◽  
Star Forming ◽  
Methanol Maser ◽  
Preliminary Results ◽  
Main Target ◽  
Maser Line ◽  
Source Structure

AbstractWe present preliminary results of the high resolution (0.10″ × 0.15″) observations of the high mass star forming region S255IR with ALMA in several spectral windows from ∼335 GHz to ∼350 GHz. The main target lines were C34S(7–6), CH3CN(19K − 18K), CO(3–2) and SiO(8–7), however many other lines of various molecules have been detected, too. We present sample spectra and maps, discuss briefly the source structure and kinematics. A new, never predicted methanol maser line has been discovered.

scholarly journals A documentary of high-mass star formation: Probing the dynamical evolution of Orion Source I on 10–100 AU scales using SiO masers

2007 ◽  
Vol 3 (S242) ◽  
pp. 130-134 ◽  
Author(s):  
L. D. Matthews ◽  
C. Goddi ◽  
L. J. Greenhill ◽  
C. J. Chandler ◽  
M. J. Reid ◽  
...  
Keyword(s):  
Star Formation ◽  
Dynamical Evolution ◽  
Young Stellar Objects ◽  
High Mass ◽  
Mass Star ◽  
Stellar Objects ◽  
Very Large Array ◽  
Long Baseline ◽  
Comprehensive Picture ◽  
Very Long Baseline Array

AbstractA comprehensive picture of high-mass star formation has remained elusive, in part because examples of high-mass young stellar objects (YSOs) tend to be relatively distant, deeply embedded, and confused with other emission sources. These factors have impeded dynamical investigations within tens of AU of high-mass YSOs—scales that are critical for probing the interfaces where outflows from accretion disks are launched and collimated. Using observations of SiO masers obtained with the Very Large Array (VLA) and the Very Long Baseline Array (VLBA), the KaLYPSO project is overcoming these limitations by mapping the structure and dynamical/temporal evolution of the material 10-1000 AU from the nearest high-mass YSO: Radio Source I in the Orion BN/KL region. Our data include ~40 epochs of VLBA observations over a several-year period, allowing us to track the proper motions of individual SiO maser spots and to monitor changes in the physical conditions of the emitting material with time. Ultimately these data will provide 3-D maps of the outflow structure over approximately 30% of the outflow crossing time. Here we summarize recent results from the KaLYPSO project, including evidence that high-mass star formation occurs via disk-mediated accretion.

scholarly journals VERA status and results

2012 ◽  
Vol 8 (S289) ◽  
pp. 194-194
Author(s):  
H. Kobayashi ◽  
Keyword(s):  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Long Baseline ◽  
Beam System ◽  
The Galaxy ◽  
The Status ◽  
Trigonometric Parallaxes ◽  
Turbulence Effects

AbstractVERA is a Very Long Baseline Interferometry (VLBI) array for astrometry, composed of four 20 m radio telescopes. They are located over a range of around 2300 km in Japan. VERA consists of a two-beam system equipped with 2, 6.7, 8, 22, and 43 GHz receivers. The two-beam system is used for phase referencing of the VLBI observations, to compensate for atmospheric-turbulence effects between two nearby objects. It has achieved measurements of annual parallaxes within 5 kpc with 10% accuracy. Observed sources are water, SiO, and methanol masers, which are found in molecular gas around star-forming regions and evolved stars. We have carried out a large program of astrometry to reveal the Galaxy's structure and velocity field. VERA has already measured trigonometric parallaxes of more than 30 sources and observed around a hundred sources using the two-beam astrometry technique. Maser sources are associated with high-mass star-forming regions, which are thought to trace the arm structure of the Galaxy. Using annual parallax and proper-motion measurements, their structure will be shown without kinematic distance assumptions. Some sources exhibit large differences between trigonometric-parallax measurements and kinematic distances. We present the status of the VERA project as well as recent results.

scholarly journals A search for the OH 6035 MHz line in high-mass star-forming regions

2020 ◽  
Vol 642 ◽  
pp. A145
Author(s):  
M. Szymczak ◽  
P. Wolak ◽  
A. Bartkiewicz ◽  
M. Aramowicz ◽  
M. Durjasz
Keyword(s):  
Young Stellar Objects ◽  
High Mass ◽  
Mass Star ◽  
General Increase ◽  
Stellar Objects ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Maser Line ◽  
Variability Index

Context. The excited states of OH masers detected in the environment of high-mass young stellar objects (HMYSOs) are important for improving our understanding of the physical conditions of these objects and also provide information about their magnetic fields. Aims. We aim to search for excited-state OH 6035 MHz maser emission in HMYSOs which might have escaped detection in previous surveys or were never searched for. Methods. A sample of HMYSOs derived from untargeted surveys of the 6668 MHz methanol maser line was observed at 6035 MHz OH transition with the Torun 32 m radio telescope. The 6035 MHz detections were observed in the OH 6031 MHz line. Two-thirds of the detections were observed at least three times over a two-year period. Results. Out of 445 targets, 37 were detected at 6035 MHz, including seven new discoveries. The 6031 MHz line was detected towards ten 6035 MHz sources, one of which was not previously reported. All the newly detected sources are faint with the peak flux density lower than 4 Jy and show significant or high variability on timescales of 4 to 20 months. Zeeman pair candidates identified in three new sources imply a magnetic field intensity of 2–11 mG. Comparison of our spectra with those obtained ~10 yr ago indicates different degrees of variability but there is a general increase in the variability index on an ~25 yr timescale, usually accompanied by significant changes in the profile shape.

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