Long-term Monitoring of Molonglo Calibrators

B. M. Gaensler , R. W. Hunstead ,, PASA, 17 (1), 72.
Title/Abstract Page: Long-term Monitoring of Molonglo
Previous Section: Acknowledgements
Contents Page: Volume 17, Number 1

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Figure 1: The relative gain of the MOST as a function of meridian distance. The data shown correspond to the asymmetric gain curve of Burgess (priv comm), with additional empirical corrections of order 2%.
\begin{figure} \centerline{\psfig{file=md_curve.ps,width=12cm,angle=270}}\end{figure}

Figure 2: Light curves for 55 MOST calibrators. Sources are marked S, U or V, corresponding to whether their time behaviour is steady, undetermined or variable respectively. Each abcissa ranges between MJD - 40000 = 5500 (1983 Jun) and 10400 (1996 Nov), while ordinates run between 0.5 and 1.5 times the nominal flux density for each source (see Table 1 of Paper I). Data have been binned into 30 day intervals -- the error bars shown are the 1$\sigma $ standard deviation of the individual data points within each interval, or are set at 5% in cases where only one data point falls in a given 30 day period.
\begin{figure} \centerline{\psfig{file=sources_1.ps,width=16cm,angle=270}}\end{figure}

Figure 3: Light curves (cont.)
\begin{figure} \centerline{\psfig{file=sources_2.ps,width=14cm,angle=270}}\end{figure}

Figure 4: Light curves (cont.)
\begin{figure} \centerline{\psfig{file=sources_3.ps,width=14cm,angle=270}}\end{figure}

Figure 5: Light curves (cont.)
\begin{figure} \centerline{\psfig{file=sources_4.ps,width=14cm,angle=270}}\end{figure}

Figure 6: Structure functions for the 18 variable sources. The dashed horizontal line corresponds to

$\Sigma _\tau = 2$, the value at which a pure sinusoid will saturate. The dashed vertical line corresponds to the approximate lag at which the structure function saturates (the time scale for variability, $\tau _V$, is defined to be twice this value).
\begin{figure} \centerline{\psfig{file=struc_1.ps,width=14cm,angle=270}}\end{figure}

Figure 7: Structure functions (cont.)
\begin{figure} \centerline{\psfig{file=struc_2.ps,width=14cm,angle=270}}\end{figure}

Figure 8: The fraction of variable sources as a function of Galactic latitude. Horizontal error bars represent the width of each latitude bin, while vertical error bars have been derived by computing the fraction of variable sources which results when half the undetermined sources in that bin are reclassified as either variable (upper limits) or steady (lower limits).
\begin{figure} \centerline{\psfig{file=lat_hist.ps,height=8cm,angle=270}}\end{figure}

Figure 9: Plot of modulation index (m) versus spectral index ($\alpha $) for all 55 MOST calibrator sources. Note the tendency for m to increase as the spectrum flattens.
\begin{figure} \centerline{\psfig{file=m_alpha.ps,width=14cm,angle=270}}\end{figure}


Table 1: Properties of variable sources in our sample.
Source b $\tau _V$ ma Identb z $\alpha^c$ LASd
  (deg) (days)         ('')
               
MRC B0208-512 -61.8 2000 0.047 Q 1.003 -0.23 6.0
MRC B0537-441 -31.1 1500 0.139 Q 0.894 +0.25 ...
MRC B0943-761 -17.4 300 0.023 g ... -0.79 2.8
MRC B1151-348 +26.3 400 0.019 Q 0.258 -0.49 <2.9
MRC B1215-457 +16.5 300 0.019 Q 0.529 -0.59 <1.9
MRC B1234-504 +12.0 1200 0.060 Q? $\ldots$ -0.82 <1
MRC B1424-418 +17.3 300 0.074 Q 1.52 -0.47 <2.3
MRC B1458-391 +17.0 400 0.022 g $\ldots$ -0.67 <2.4
MRC B1549-790 -19.5 700 0.050 g 0.15 -0.29 <1.0
MRC B1610-771 -18.9 400 0.052 Q 1.71 -0.13 <1
MRC B1718-649 -15.8 1400 0.060 g 0.013 +0.21 ...
MRC B1740-517 -11.5 2500 0.063 g $\ldots$ -0.08 <1
MRC B1827-360 -11.8 400 0.016 g $\ldots$ -1.12 <1.5
MRC B1829-718 -24.5 400 0.048 g $\ldots$ -0.35 ...
MRC B1854-663 -25.5 400 0.022 g ... -0.86 <1.0
MRC B1921-293 -19.6 3000 0.191 Q 0.352 +0.38 ...
MRC B2052-474 -40.4 300 0.084 Q 1.489 -0.34 3.9
MRC B2326-477 -64.1 400 0.037 Q 1.489 -0.15 ...
               

a Modulation index, defined by

$m=\sigma/\bar{S}$ b Q = quasar ; g = galaxy c Spectral index $\alpha $ (where

$S \propto \nu^{\alpha}$) between 408 and 2700 MHz (or 4850 MHz if 2700 MHz flux density not available) d Largest angular size at 5 GHz, measured with the Australia Telescope Compact Array (Burgess 1998)


Title/Abstract Page: Long-term Monitoring of Molonglo
Previous Section: Acknowledgements
Contents Page: Volume 17, Number 1

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