scholarly journals Radio variability properties for sources at multi-frequencies

2007 ◽  
Vol 3 (S245) ◽  
pp. 251-252
Author(s):  
Y. Liu ◽  
J. H. Fan ◽  
H. G. Wang

AbstractUsing three radio databases of the university of Michigan Radio Astronomy Observatory (UMRAO), the National Radio Astronomy Observatory (NRAO), and the Metsähovi Observatory, we analyzed the radio light curves by the power spectral analysis and CLEANest method in search for possible periodicity. Multiple periods are found in some sources at multi-frequencies. We adopted the wavelets for period analysis of unevenly sampled time series to search for the evolution of the parameters (period, amplitude) of possible periodicities. Some possible variation of these parameters are found.

2007 ◽  
Vol 3 (S245) ◽  
pp. 245-246
Author(s):  
J. H. Fan ◽  
Y. Huang ◽  
Y. Liu ◽  
Y. Gao ◽  
T. X. Hua ◽  
...  

AbstractIn this work, using the database of the university of Michigan Radio Astronomy Observatory (UMRAO), we determined the brightness temperatures, TB for a sample of 167 radio sources. The value of TB is in a range of log TB(K) = 10.46 to 20.08, which suggested that the boosting factors are in a range of δ = 0.41 to 41.26.


2012 ◽  
Vol 8 (S287) ◽  
pp. 110-111 ◽  
Author(s):  
Sunelle Otto ◽  
Michael J. Gaylard

AbstractThe work here represents the summary of observations made with the Hartebeesthoek Radio Astronomy Observatory (HartRAO) 26 m telescope of the water vapour (H2O) Masers in the Orion KL source region for a period of 8 months during the flare of 2011. The observation setup, calibration method together with the resulting maser time series are discussed.


1991 ◽  
Vol 131 ◽  
pp. 160-164 ◽  
Author(s):  
George W. Swenson

In the spring of 1964, having qualified for a sabbattical leave from the University of Illinois and having recently completed two years as Chairman of the Visiting Committee of the National Radio Astronomy Observatory, I inquired of the NRAO staff as to whether a desk and possibly some augmentation of my University half-salary might be available at Green Bank for the following academic year. Instead I was invited to join the staff as a fulltime employee and to take a coordinating role in the development of the “very large array” as Chairman of the Design Committee. The University granted me a year’s leave of absence which eventually stretched to four years.


2007 ◽  
Vol 3 (S242) ◽  
pp. 97-101 ◽  
Author(s):  
Sharmila Goedhart ◽  
Michael J. Gaylard ◽  
D. Johan van der Walt

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.


1967 ◽  
Vol 20 (6) ◽  
pp. 725
Author(s):  
HM Tovmassian ◽  
IG Moiseev

The positions of 33 radio sources previously identified with distant clusters of galaxies were remeasured more accurately to check the identifications. Observations were made at 1410 and 2650 MHz with the 210 ft radio telescope of the Australian National Radio Astronomy Observatory at Parkes, and at 408 MHz with the east-west arm of the Mills Cross at the Molonglo Radio Astronomical Observatory of the University of Sydney. It was found that 21 sources are situated within 5 min of arc of the centres of the corresponding clusters.


2013 Africon ◽  
2013 ◽  
Author(s):  
Domingos Barbosa ◽  
Miguel Bergano ◽  
Valerio A. R. M. Ribeiro ◽  
Anita Loots ◽  
Venkatasubramani L. Thondikulam ◽  
...  

2012 ◽  
Vol 8 (S291) ◽  
pp. 208-208
Author(s):  
Augustine Chukwude

AbstractWe investigate the spin-down behaviour of a sample of 25 radio pulsars on decadal timescales (~ 18 years) using a continuous timing data obtained over a period of at Hartebeesthoek Radio Astronomy Observatory (HartRAO). Particular attention is placed on achieving a better time resolution of both the short-term and long-term changes in pulsar spin-down using local phase-coherent measurements of the spin-down rates (). We demonstrate that the spin-down of radio pulsars is generally complicated by a superposition of processes that may or may not be related. Specifically, our results show that (i) for 7 pulsars, the observed spin-down variation is largely stochastic, characterized by random and sustained jumps in of varying amplitudes, (ii) for 9 objects, the spin-down evolution shows dominant monotonic variations in superimposed on short-term stochastic jumps in the parameter, and (iii) for the remaining 9 pulsars, the long-term spin-down evolution is non-monotonic, dominated by some systematic excursion in the measured spin-down rates.


2009 ◽  
Vol 57 (7) ◽  
pp. 1783-1789 ◽  
Author(s):  
Tao Yu ◽  
Chunguang Li ◽  
Fei Li ◽  
Qiang Zhang ◽  
Liang Sun ◽  
...  

2000 ◽  
Vol 1 (1) ◽  
pp. 79 ◽  
Author(s):  
I. ZACHARIAS

A computational analysis of the periods and structure of surface seiches of Lake Trichonis in Greece and its experimental verification from three simultaneous water gauge recordings, mounted along the shores in Myrtia, Panetolio and Trichonio is given. The first five theoretical modes are calculated with a finite difference code of tidal equations, which yield the eigenperiodes, co-range and co-tidal lines that are graphically displayed and discussed in detail.Experimental verifications are from recordings taken during spring. Visual observations of the record permit identification of the five lowest order modes, including inter station phase shift. Power spectral analysis of two time series and interstation phase difference and coherence spectra allow the identification of the same five modes. Agreement between the theoretically predicted and the experimentally determined periods was excellent for most of the calculated modes.


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