Long term 6.7 GHz methanol maser monitoring program

AbstractThe first long-term maser (mainly methanol) monitoring program is under way with the radio telescopes of Ventspils International Radio Astronomy Center. The first activity of this program was to develop an observations methodology and data registration and reduction software for the Ventspils telescopes. The developed routines are to be used for maser variability monitoring, investigating short bursts of intensity and a search for new, previously unknown, maser sources. Currently the program consists of 41 methanol masers observed at 6.7 GHz, while new ones are periodically added. The maser sources are observed at 3 – 5 day intervals. It was found that most the sources display a significant level of variability with time, ranging from a few days, up to several months and, perhaps, years. In addition to non-varying masers, several types of maser variability behavior were observed, including: monotonic increases or decreases, un-periodical, quasi-periodic and periodic variations.

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Periodic variations in 6.7-GHz methanol masers

Proceedings of the International Astronomical Union ◽

10.1017/s174392130701263x ◽

2007 ◽

Vol 3 (S242) ◽

pp. 97-101 ◽

Cited By ~ 3

Author(s):

Sharmila Goedhart ◽

Michael J. Gaylard ◽

D. Johan van der Walt

Keyword(s):

Time Series ◽

Radio Astronomy ◽

Monitoring Program ◽

Astronomy Observatory ◽

Intensive Monitoring ◽

Radio Astronomy Observatory ◽

Long Term Trends ◽

Methanol Masers ◽

Maser Sources

AbstractAn intensive monitoring program of 54 6.7-GHz methanol maser sources was carried out at the Hartebeesthoek Radio Astronomy Observatory from January 1999 to April 2003. The monitoring program was subsequently continued on 19 sources of interest. Analysis of the resulting time-series stretching over eight years shows that six of the sources are periodic, with periods ranging from 133 days to 504 days. The waveforms in individual sources range from sinusoidal fluctuations to sharp flares and there can be other long term trends in the time-series. The amplitudes of the variations can also change from cycle to cycle. The time-series of the periodic masers will be presented, and possible causes of the variability discussed.

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Millimetre wavelength methanol masers survey towards massive star forming regions

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307013051 ◽

2007 ◽

Vol 3 (S242) ◽

pp. 234-235

Author(s):

T. Umemoto ◽

N. Mochizuki ◽

K. M. Shibata ◽

D.-G. Roh ◽

H.-S. Chung

Keyword(s):

Detection Rate ◽

Massive Star ◽

Molecular Line ◽

Maser Emission ◽

Star Forming ◽

Methanol Maser ◽

Physical Conditions ◽

Star Forming Regions ◽

Methanol Masers ◽

Maser Sources

AbstractWe present the results of a mm wavelength methanol maser survey towards massive star forming regions. We have carried out Class II methanol maser observations at 86.6 GHz, 86.9 GHz and 107.0 GHz, simultaneously, using the Nobeyama 45 m telescope. We selected 108 6.7 GHz methanol maser sources with declinations above −25 degrees and fluxes above 20 Jy. The detection limit of maser observations was ~3 Jy. Of the 93 sources surveyed so far, we detected methanol emission in 25 sources (27%) and “maser” emission in nine sources (10%), of which thre “maser” sources are new detections. The detection rate for maser emission is about half that of a survey of the southern sky (Caswell et al. 2000). There is a correlation between the maser flux of 107 GHz and 6.7 GHz/12 GHz emission, but no correlation with the “thermal” (non maser) emission. From results of other molecular line observations, we found that the sources with methanol emission show higher gas temperatures and twice the detection rate of SiO emission. This may suggest that dust evaporation and destruction by shock are responsible for the high abundance of methanol molecules, one of the required physical conditions for maser emission.

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Sub-mm observations of periodic methanol masers

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317010699 ◽

2017 ◽

Vol 13 (S336) ◽

pp. 301-302

Author(s):

D. J. van der Walt ◽

J.-M. Morgan ◽

J. O. Chibueze ◽

Q. Zhang

Keyword(s):

Methanol Maser ◽

Methanol Masers ◽

Maser Sources

AbstractWe present the results of sub-millimetre observations on three periodic methanol maser sources. Our results indicate that there are geometric differences between some periodic methanol masers which have different variability profiles.

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Imaging of selected sources from the Methanol Multibeam Survey

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307012914 ◽

2007 ◽

Vol 3 (S242) ◽

pp. 184-185

Author(s):

D. Wong-McSweeney ◽

G. A. Fuller ◽

S. Etoka

Keyword(s):

Angular Resolution ◽

Galactic Plane ◽

High Angular Resolution ◽

Maser Emission ◽

Methanol Maser ◽

Preliminary Results ◽

Methanol Masers ◽

Maser Sources

AbstractHigh angular resolution observations are essential for understanding the nature of maser emission and the sources which excite it. Here we present preliminary results from MERLIN observations of three methanol masers from the Toruń survey. These MERLIN observations are being analysed as part of the interferometric component of the Methanol Multibeam (MMB) Survey which is surveying the Galactic plane at |b|≤2° for 6.67 GHz methanol maser sources.

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A Sensitive Search for Predicted Methanol Maser Transitions with the Australia Telescope Compact Array

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2016.48 ◽

2016 ◽

Vol 33 ◽

Cited By ~ 3

Author(s):

A. Chipman ◽

S. P. Ellingsen ◽

A. M. Sobolev ◽

D. M. Cragg

Keyword(s):

Star Formation ◽

Class Ii ◽

High Mass ◽

Mass Star ◽

Radio Telescopes ◽

Methanol Maser ◽

Upper Limit ◽

Methanol Masers ◽

Star Formation Regions ◽

Compact Array

AbstractWe have used the Australia Telescope Compact Array to search for a number of centimetre wavelength methanol transitions which are predicted to show weak maser emission towards star formation regions. Sensitive, high spatial, and spectral resolution observations towards four high-mass star formation regions which show emission in a large number of class II methanol maser transitions did not result in any detections. From these observations, we are able to place an upper limit of ≲ 1300 K on the brightness temperature of any emission from the 31A+–31A−, 17−2–18−3 E (vt = 1), 124–133 A−, 124–133 A+, and 41A+–41A− transitions of methanol in these sources on angular scales of 2 arcsec. This upper limit is consistent with current models for class II methanol masers in high-mass star formation regions and better constraints than those provided here will likely require observations with next-generation radio telescopes.

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3D motions of 6.7 GHz methanol masers and effects of the Galactic bar

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312021837 ◽

2012 ◽

Vol 8 (S289) ◽

pp. 410-413

Author(s):

Naoko Matsumoto ◽

Mareki Honma ◽

Keyword(s):

Inclination Angle ◽

Dynamical Model ◽

Proper Motions ◽

Methanol Maser ◽

Circular Rotation ◽

Methanol Masers ◽

Maser Sources ◽

Better Than ◽

Simple Models ◽

Rotation Model

AbstractTo search for kinematic evidence of the existence of the Galactic bar, we observed 10 methanol maser sources at the near end of the bar with VERA (VLBI Exploration of Radio Astrometry). From these observations, we obtained absolute proper motions of eight sources based on the phase-referencing technique. We compared the motions with the predictions of three simple models in a 3D plane. This comparison showed that a non-flat circular rotation model and a dynamical model including a bar potential reproduce the observed data better than a flat rotation model. In addition, the bar model suggests that the inclination angle of the Galactic bar is around 35°, which is consistent with previous studies.

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Methanol masers: Evolutionary and kinematic tracers of massive star formation

Symposium - International Astronomical Union ◽

10.1017/s0074180900222274 ◽

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.

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Exploring the Nature of MMB sources: A Search for Class I Methanol Masers and their Outflows

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318000698 ◽

2017 ◽

Vol 13 (S336) ◽

pp. 317-318

Author(s):

Nichol Cunningham ◽

Gary Fuller ◽

Adam Avison ◽

Shari Breen

Keyword(s):

Massive Star ◽

Class Ii ◽

Class I ◽

Star Forming ◽

Methanol Maser ◽

Star Forming Regions ◽

Methanol Masers ◽

Initial Results ◽

Maser Sources

AbstractWe present the initial results from a class I 44-GHz methanol maser follow-up survey, observed with the MOPRA telescope, towards 272 sources from the Methanol Multi-beam survey (MMB). Over half (∼60%) of the 6.7 GHz class II MMB maser sources are associated with a class I 44-GHz methanol maser at a greater than 5σ detection level. We find that class II MMB masers sources with an associated class I methanol maser have stronger peak fluxes compared to regions without an associated class I maser. Furthermore, as part of the MOPRA follow-up observations we simultaneously observed SiO emission which is a known tracer of shocks and outflows in massive star forming regions. The presence of SiO emission, and potentially outflows, is found to be strongly associated with the detection of class I maser emission in these regions.

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On the Methanol masers in G9.62+0.20E: Preliminary colliding-wind binary (CWB) calculations

Proceedings of the International Astronomical Union ◽

10.1017/s174392131200676x ◽

2012 ◽

Vol 8 (S287) ◽

pp. 112-113

Author(s):

S. P. van den Heever ◽

D. J. van der Walt ◽

J. M. Pittard ◽

M. G. Hoare

Keyword(s):

Light Curves ◽

Continuum Emission ◽

Hii Region ◽

Star Forming ◽

Methanol Maser ◽

Methanol Masers ◽

Maser Sources ◽

The Continuum

AbstractA comparison between the observed periodic flaring of methanol maser sources in the star forming region G9.62+0.20E and the continuum emission from parts of a background HII region is made. Using a colliding wind binary (CWB) model preliminary calculations show that the CWB model results fit the maser light curves very well.

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