scholarly journals Statistics of the 6.7 GHz methanol maser variability from the Toruń survey

2002 ◽  
Vol 206 ◽  
pp. 135-138
Author(s):  
Anna Niezurawska ◽  
Marian Szymczak ◽  
Grzegorz Hrynek ◽  
Andrzej J. Kus
Keyword(s):  
Flux Density ◽  
Time Scales ◽  
Radio Telescope ◽  
Methanol Maser ◽  
Maser Line

A sample of 174 methanol sources has been observed with the 32 m Toruń radio telescope at four or five epochs separated by 3-7 months. Observations of the 6.7 GHz maser line revealed that about 80% of sources are variable. 20% of sources showed strong variations of the integrated flux density usually on time-scales of 5-12 months. These variations were associated with strong changes in the relative intensities of maser features. Methanol emission from five sources disappeared. The time-scales of variability were longer than 12 months for only 23% of variable sources. It is suggested that the variability of methanol emission is related to the dynamics of the maser regions.

Rapid burst of 6.7 GHz methanol maser in the high mass star region G33.641-0.228

2017 ◽  
Vol 13 (S336) ◽  
pp. 61-62
Author(s):  
Kārlis Bērziņš ◽  
Ivar Shmeld ◽  
Artis Aberfelds
Keyword(s):  
Flux Density ◽  
Radio Telescope ◽  
Ground Level ◽  
Decay Phase ◽  
High Mass ◽  
Mass Star ◽  
Methanol Maser ◽  
Maximum Peak ◽  
Spatial Component ◽  
Peak Flux

AbstractWe report another 6.7 GHz methanol maser burst in the high mass star region G33.641-0.228. The flare is in its second component at vLSR = 59.6 km s−1 and was observed in August-September 2016 by VIRAC radio telescope RT-32 in Irbene, Latvia. Several bursts of the second spatial component of G33.641-0.228 have been reported previously by Fujisawa et al. The maximum peak flux density of the source was measured to reach 343 Jy that is 13 times increase from its ground level. Significant oscillations were discovered during the decay phase indicating a more complex burst mechanism that cannot be explained by a simple heating of the region.

1612 MHz OH maser monitoring with the Nançay Radio Telescope

2012 ◽  
Vol 8 (S287) ◽  
pp. 254-255 ◽  
Author(s):  
D. Engels ◽  
E. Gérard ◽  
N. Hallet
Keyword(s):  
Flux Density ◽  
Radio Telescope ◽  
Light Curves ◽  
Phase Lag ◽  
Full Sample ◽  
Ir Stars ◽  
Maser Line ◽  
Circumstellar Shell ◽  
Linear Diameter

Abstract20 OH/IR stars are monitored in the 1612 MHz OH maser line with the Nançay Radio Telescope. The program started in 2008 with monthly observations of the full sample and will last at least until end of 2012. The aim is the determination of the linear diameter of the circumstellar shell using the phase lag between the light curves of the varying OH maser lines. To use them for distance determinations, angular diameters are obtained by interferometric measurements while the stars pass the maximum of their OH maser flux density variations. The periods of the OH/IR stars monitored are between 425 and >2000 days.

scholarly journals Detection of new methanol maser transitions associated with G358.93−0.03

2019 ◽  
Vol 489 (3) ◽  
pp. 3981-3989 ◽  
Author(s):  
G C MacLeod ◽  
K Sugiyama ◽  
T R Hunter ◽  
J Quick ◽  
W Baan ◽  
...  
Keyword(s):  
Energy Source ◽  
Flux Density ◽  
Time Scales ◽  
Massive Star ◽  
Near Infrared ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser ◽  
Methanol Masers ◽  
Short Time

ABSTRACT We report the detection of new 12.178, 12.229, 20.347, and 23.121 GHz methanol masers in the massive star-forming region G358.93−0.03, which are flaring on similarly short time-scales (days) as the 6.668 GHz methanol masers also associated with this source. The brightest 12.178 GHz channel increased by a factor of over 700 in just 50 d. The masers found in the 12.229 and 20.347 GHz methanol transitions are the first ever reported and this is only the fourth object to exhibit associated 23.121 GHz methanol masers. The 12.178 GHz methanol maser emission appears to have a higher flux density than that of the 6.668 GHz emission, which is unusual. No associated near-infrared flare counterpart was found, suggesting that the energy source of the flare is deeply embedded.

14 years of 6.7 GHz periodic methanol maser observations towards G188.95+0.89

2019 ◽  
Vol 15 (S356) ◽  
pp. 393-394
Author(s):  
Martin M. Mutie ◽  
Paul Baki ◽  
James O. Chibueze ◽  
Khadija El Bouchefry
Keyword(s):  
Radio Telescope ◽  
Exponential Decay ◽  
Hii Regions ◽  
Monitoring Period ◽  
Methanol Maser ◽  
Spectral Components ◽  
Methanol Masers ◽  
Compact Hii Regions

AbstractWe report the results of 14 years of monitoring of G188.95+0.89 periodic 6.7 GHz methanol masers using the Hartebeesthoek 26-m radio telescope. G188.95+0.89 (S252, AFGL5180) is a radio-quiet methanol maser site that is often interpreted as precursors of ultra-compact HII regions or massive protostar sites. At least five bright spectral components were identified. The maser feature at 11.36 km s-1 was found to experience an exponential decay during the monitoring period. The millimetre continuum reveals two cores associated with the source.

scholarly journals Water maser and radio continuum emission towards IRAS 23139+5939

2007 ◽  
Vol 3 (S242) ◽  
pp. 180-181
Author(s):  
M. A. Trinidad ◽  
S. Curiel ◽  
J. M. Torrelles ◽  
L. F. Rodríguez ◽  
V. Migenes ◽  
...  
Keyword(s):  
Flux Density ◽  
Line Emission ◽  
The Other ◽  
Radio Continuum ◽  
High Mass ◽  
Continuum Emission ◽  
Maser Line ◽  
Water Masers ◽  
Water Maser ◽  
The Continuum

AbstractWe present simultaneous observations of continuum (3.5 and 1.3cm) and water maser line emission (1.3cm) carried out with the VLA-A toward the high-mass object IRAS 23139+5939. We detected two radio continuum sources at 3.5cm separated by 0”5 (~2400 AU), I23139 and I23139S. Based on the observed continuum flux density and the spectral index, we suggest that I23139 is a thermal radio jet associated with a high-mass YSO. On the other hand, based on the spatio-kinematical distribution of the water masers, together with the continuum emission information, we speculate that I23139S is also a jet source powering some of the masers detected in the region.

scholarly journals A blind survey of the 6.7 GHz methanol maser line

2002 ◽  
Vol 206 ◽  
pp. 143-146
Author(s):  
Marian Szymczak ◽  
Andrzej J. Kus ◽  
Grzegorz Hrynek
Keyword(s):  
Grid Point ◽  
Hii Regions ◽  
Triangular Grid ◽  
Average Sensitivity ◽  
Grid Pattern ◽  
Methanol Maser ◽  
Peak Flux ◽  
Maser Line ◽  
Methanol Masers ◽  
Ultracompact Hii

A blind survey for 6.7GHz methanol maser emission has been made with the 32 m Toruń radio telescope. The survey consists of 4,800 spectra on an equilateral triangular grid pattern with each grid point separated by 4.4 covering a field of ∼21 deg2 at galactic longitudes 20° to 40° and galactic latitudes ±0°52. The average sensitivity was 1.6 Jy and the spectral resolution was 0.04kms−1. A total of 99 sources were detected, 28 of which were not found during previous searches of IRAS-selected ultracompact HII regions. The peak flux density of new detections is usually lower than 30 Jy. About half of the methanol masers have no IRAS counterparts within a radius of 2. The nature of these sources is unclear.

scholarly journals Radio light-curve for WR 146 (HM19-3, WC6+O8.5), a colliding wind binary

1999 ◽  
Vol 193 ◽  
pp. 390-391
Author(s):  
Diah Y.A. Setia Gunawan ◽  
A. Ger de Bruyn ◽  
Karel A. van der Hucht ◽  
Peredur M. Williams
Keyword(s):  
Light Curve ◽  
Flux Density ◽  
Radio Telescope ◽  
Time Scale ◽  
Preliminary Results ◽  
Average Flux

We report preliminary results of monitoring the flux from the Wolf-Rayet object WR 146 with the Westerbork Synthesis Radio Telescope at 21 cm since 1989. We find the average flux density slowly rising in the period 1989–1997, with evidence of shorter time-scale variability.

Zeeman Effect Observations in Class I Methanol Masers

2018 ◽  
Vol 14 (A30) ◽  
pp. 140-140
Author(s):  
Emmanuel Momjian ◽  
Anuj P. Sarma
Keyword(s):  
Zeeman Effect ◽  
Linear Structure ◽  
Class I ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Splitting Factor ◽  
Maser Line ◽  
Methanol Masers ◽  
Expected Values

AbstractWe report the detection of the Zeeman effect in the 44 GHz Class I methanol maser line toward the star forming region DR21W. The 44 GHz methanol masers in this source occur in a ∼3” linear structure that runs from northwest to southeast, with the two dominant components at each end, and several weaker maser components in between. Toward a 93 Jy maser in the dominant northwestern component, we find a significant Zeeman detection of −23.4 ± 3.2 Hz. If we use the recently published result of Lankhaar et al. (2018) that the F=5-4 hyperfine transition is responsible for the 44 GHz methanol maser line, then their value of z = −0.92 Hz mG−1 yields a line-of-sight magnetic field of Blos =25.4 ± 3.5 mG. If Class I methanol masers are pumped in high density regions with n∼107–8 cm−3, then magnetic fields in these maser regions should be a few to several tens of mG. Therefore, our result in DR21W is certainly consistent with the expected values.Using the above noted splitting factor in past Zeeman effect detections in Class I methanol masers reported by Sarma & Momjian (2011) and Momjian & Sarma (2017) in the star forming regions OMC-2 and DR21(OH) result in Blos values of 20.0 ± 1.2 mG and 58.2 ± 2.9 mG, respectively. These are also consistent with the expected values.

scholarly journals Influence of dust parameters on class II methanol maser pumping

2002 ◽  
Vol 206 ◽  
pp. 183-186
Author(s):  
Andrei B. Ostrovskii ◽  
Andrej M. Sobolev
Keyword(s):  
Chemical Composition ◽  
Dust Emission ◽  
Class Ii ◽  
Dilution Factor ◽  
Model Calculations ◽  
Dust Layer ◽  
Methanol Maser ◽  
Wide Range ◽  
Maser Line ◽  
Methanol Masers

Results of model calculations for class II methanol masers (MMII) are presented. The model of the pumping assumes that an external dust layer provides the source of energy for maser excitation. The dependence of the emergent maser spectrum on the properties of the dust layer is studied. These properties include the chemical composition and sizes of dust grains, the temperature and optical depth of the dust layer. as well as the dilution factor of external dust emission. It is shown that, in order to reproduce the observed patterns of class II methanol maser line ratios, the pumping dust layer should be mostly composed of silicate grains with sizes smaller than 0.01 μ. It is shown that the layer of warm (> 125 K) dust effectively pumps the strongest MMII transitions over a wide range of 30 μ dust opacities (0.01–2) and dilution factors (0.02–0.5).

scholarly journals Measurements Of The Flux Density Of Discrete Radio Sources At 6 Cm Wavelength

1966 ◽  
Vol 19 (4) ◽  
pp. 577 ◽  
Keyword(s):  
Flux Density ◽  
Radio Telescope ◽  
Power Law ◽  
Radio Sources ◽  
Frequency Range ◽  
Thermal Radio ◽  
Discrete Radio Sources ◽  
Selection Of ◽  
Lower Frequencies

The flux densities of 67 non-thermal radio sources have been measured at a frequency of 5000 Mc/s with the CSIRO 210 ft radio telescope at Parkes. The sources were chosen from the stronger objects in the 3C catalogue (Edge et al. 1959), the CTA and CTD catalogues (Harris and Roberts 1960; Kellermann and Read 1965), and the Parkes catalogue (Bolton, Gardner, and Mackey 1964; Price and Milne 1965; Day et al. 1966). In the selection of sources observed in this program, special emphasis was placed on objects whose spectra at lower frequencies showed significant departures from the usual power law with an index near -0�8. Most of the sources reported here have not been previously measured at wavelengths shorter than 10 cm and thus the present observations extend the frequency range of their spectra by nearly a factor of two.

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