scholarly journals Observations of Cosmic Masers

1988 ◽  
Vol 129 ◽  
pp. 213-222
Author(s):  
P. J. Diamond
Keyword(s):  
Late Type ◽  
Star Forming ◽  
Maser Spot ◽  
Star Forming Regions ◽  
Vlbi Observations ◽  
Cosmic Masers ◽  
Interstellar Scattering

A review is presented of recent results from interferometric observations of cosmic masers. Several topics will be discussed, including MERLIN/VLA/VLBI observations of megamasers; recent results on masers in star forming regions and around late-type stars and some new results on the effects of interstellar scattering on maser spot sizes.

scholarly journals A 20-year H2O maser monitoring program with the Medicina 32-m telescope

2007 ◽  
Vol 3 (S242) ◽  
pp. 223-227 ◽  
Author(s):  
J. Brand ◽  
M. Felli ◽  
R. Cesaroni ◽  
C. Codella ◽  
G. Comoretto ◽  
...  
Keyword(s):  
Sampling Rate ◽  
Monitoring Program ◽  
Late Type ◽  
Maser Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
Vlbi Observations ◽  
Water Maser ◽  
Representative Samples

AbstractThe Arcetri/Bologna H2O maser group has been monitoring the 1.3-cm water maser emission from a sample of 43 star-forming regions (SFRs) and 22 late-type stars for about 20 years at a sampling rate of 4-5 observations each year, using the 32-m Medicina Radio Telescope (HPBW 1.′9 at 22 GHz). For the late-type stars we observe representative samples of OH/IR-stars, Mira's, semi-regular variables, and supergiants. The SFR-sample spans a large interval in FIR luminosity of the associated Young Stellar Object (YSO), from 20 L⊙ to 1.5 × 106 L⊙, and offers a unique data base for the study of the long-term (years) variability of the maser emission in regions of star formation.This presentation concerns only the masers in SFRs. The information obtained from single-dish monitoring is complementary to what is extracted from higher-resolution (VLA and VLBI) observations, and can better explore the velocity domain and the long-term variability therein.We characterize the variability of the sources in various ways and we study how it depends on the luminosity and other properties of the associated YSO and its environment.

scholarly journals Magnetic Field Structure of Star Forming Regions: VLBI Spectral Line Results

1984 ◽  
Vol 110 ◽  
pp. 333-334
Author(s):  
J.A. Garcia-Barreto ◽  
B. F. Burke ◽  
M. J. Reid ◽  
J. M. Moran ◽  
A. D. Haschick
Keyword(s):  
Magnetic Field ◽  
Three Dimensional ◽  
Aperture Synthesis ◽  
Stokes Parameters ◽  
Hii Region ◽  
Star Forming ◽  
Star Forming Regions ◽  
Vlbi Observations ◽  
The Magnetic Field ◽  
Synthesis Experiment

Magnetic fields play a major role in the general dynamics of astronomical phenomena and particularly in the process of star formation. The magnetic field strength in galactic molecular clouds is of the order of few tens of μG. On a smaller scale, OH masers exhibit fields of the order of mG and these can probably be taken as representative of the magnetic field in the dense regions surrounding protostars. The OH molecule has been shown to emit highly circular and linearly polarized radiation. That it was indeed the action of the magnetic field that would give rise to the highly polarized spectrum of OH has been shown by the VLBI observations of Zeeman pairs of the 1720 and 6035 MHz by Lo et. al. and Moran et. al. VLBI observations of W3 (OH) revealed that the OH emission was coming from numerous discrete locations and that all spots fell within the continuum contours of the compact HII region. The most detailed VLBI aperture synthesis experiment of the 1665 MHz emission from W3 (OH) was carried out by Reid et. al. who found several Zeeman pairs and a characteristic maser clump size of 30 mas. In this work, we report the results of a 5 station VLBI aperture synthesis experiment of the 1665 MHz OH emission from W3 (OH) with full polarization information. We produced VLBI synthesis maps of all Stokes parameters of 16 spectral features that showed elliptical polarization. The magnitude and direction of the magnetic field have been obtained by the detection of 7 Zeeman pairs. The three dimensional orientation of the magnetic field can be obtained, following the theoretical arguments of Goldreich et. al., from the observation of π and σ components.

scholarly journals The beauty of resolution: The SN Ib factory NGC 2770 spatially resolved

2014 ◽  
Vol 10 (S309) ◽  
pp. 169-170
Author(s):  
C. C. Thöne ◽  
L. Christensen ◽  
J. Gorosabel ◽  
A. de Ugarte Postigo
Keyword(s):  
Stellar Population ◽  
Late Type ◽  
Spiral Arms ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions ◽  
The Galaxy ◽  
History Of ◽  
First Time

AbstractThe late-type spiral NGC 2770 hosted 3 Type Ib supernovae (SNe) in or next to star-forming regions in its outer spiral arms. We study the properties of the SN sites and the galaxy at different spatial resolutions to infer propeties of the SN progenitors and the SF history of the galaxy. Several 3D techniques are used and, for the first time, we present images of metallicity, shocks and stellar population ages from OSIRIS/GTC imaging with tunable narrowband filters.

Late-type X-ray Emitting Binaries in the Solar Neighborhood and in Star Forming Regions

2006 ◽  
Vol 304 (1-4) ◽  
pp. 17-20
Author(s):  
Antonio Frasca ◽  
Ettore Marilli ◽  
Patrick Guillout ◽  
Rubens Freire Ferrero ◽  
Elvira Covino ◽  
...  
Keyword(s):  
Solar Neighborhood ◽  
Late Type ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions

scholarly journals Methanol masers: Evolutionary and kinematic tracers of massive star formation

2002 ◽  
Vol 206 ◽  
pp. 147-150
Author(s):  
Vincent Minier ◽  
Roy Booth ◽  
John Conway ◽  
Michele Pestalozzi
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Vlbi Observations ◽  
Methanol Masers ◽  
Maser Sources

We summarise our recent VLBI observations of a large sample of methanol maser sources associated with high-mass star-forming regions.

Stellar Kinematics in Star-Forming Regions

1984 ◽  
Vol 88 ◽  
pp. 263-264
Author(s):  
Robert D. Mathieu ◽  
David W. Latham ◽  
Lee Hartmann
Keyword(s):  
Radial Velocity ◽  
Measurement Errors ◽  
Main Sequence ◽  
Stellar Kinematics ◽  
Late Type ◽  
Stellar Rotation ◽  
Main Sequence Stars ◽  
Central Wavelength ◽  
Star Forming ◽  
Star Forming Regions

High-precision radial-velocity studies of three young, star-forming regions - λ Orionis, NGC 2264 and Taurus-Auriga - are under way; study of the Orion cluster (with L. Marschall, in conjunction with the Yale proper-motion study) is beginning this winter. Single-order (~50 A, central wavelength 5200A) echelle spectra have been obtained for late-type pre-main sequence stars. Due to the spectral peculiarities and stellar rotation associated with pre-main sequence stars, our radial-velocity precisions are often somewhat poorer than those obtained for late-type dwarfs or giants. Measurement errors of 0.7-1.5 km/sec are typical, although some stars do not permit any radial velocity measurement at all. We summarize preliminary findings for each region:

scholarly journals Report on a Survey of H2O Masers Towards the Galactic Center

1996 ◽  
Vol 169 ◽  
pp. 343-344
Author(s):  
Deborah A. Levine ◽  
Mark Morris
Keyword(s):  
Galactic Center ◽  
Point Sources ◽  
Late Type ◽  
Star Forming ◽  
Star Forming Regions ◽  
Circumstellar Shells

Galactic H2O masers are associated either with the circumstellar shells of late-type stars or with star-forming regions (SFRs). Previous surveys for H2O masers had revealed relatively few near the Galactic Center (GC). We report on the continuation of a survey using the VLA to make 22.2 GHz observations of IRAS point sources which lie within 2° of the GC and which have either 12 μm or 25 μm flux > 8 Jy. Taylor, Morris and Schulman (TMS, 1992, AJ, 106, 1978) previously observed 97 of 342 candidate sources. We have observed 160 more and plan to complete the survey in early 1995.

scholarly journals Maser astrometry with VERA and Galactic structure

2012 ◽  
Vol 8 (S287) ◽  
pp. 386-390 ◽  
Author(s):  
Mareki Honma ◽  
Takumi Nagayama ◽  
Tomoya Hirota ◽  
Naoko Matsumoto ◽  
Nobuyuki Sakai ◽  
...  
Keyword(s):  
Rotation Curve ◽  
Galactic Structure ◽  
Proper Motions ◽  
Late Type ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Galaxy ◽  
Maser Sources

AbstractSince 2007 VERA (VLBI Exploration of Radio Astrometry) has been producing astrometric results (distances and/or proper motions) for Galactic maser sources. Nearly 30 parallaxes have been obtained for star-forming regions and late-type stars. By using VERA's astrometric results for star-forming regions, combined with those obtained with VLBA and EVN, fundamental Galactic parameters and Galactic structure may be derived. Our results show that R0 = 8.4 ± 0.4 kpc and Ω⊙ ≡ Ω0 + V⊙/R0=30.7±0.8 km s−1 kpc−1, and also show that the rotation curve of the Galaxy is nearly flat. The determinations of Galactic parameters and structures demonstrate that the maser astrometry can not only contribute significantly to research of individual maser sources, but also to studies of the structure of the Galaxy.

Late-type X-ray Emitting Binaries in the Solar Neighborhood and in Star Forming Regions

2007 ◽  
pp. 15-18
Author(s):  
Antonio Frasca ◽  
Ettore Marilli ◽  
Patrick Guillout ◽  
Rubens Freire Ferrero ◽  
Elvira Covino ◽  
...  
Keyword(s):  
Solar Neighborhood ◽  
Late Type ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions
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