Access to Astronomical Catalogues

J/MNRAS/235/1313    Metrewave Extragalactic Variability   (Slee+ 1988)
A survey for metrewave variability extragalactic radio sources.
      Slee O.B., Siegman B.C.
     <Mon. Not. R. Astron. Soc. 235, 1313 (1988)>
     =1988MNRAS.235.1313S       (SIMBAD/NED BibCode)
ADC_Keywords: Radio sources


Abstract:
    We report a detailed statistical study of the intensity variations in
    412 extragalactic radio sources randomly selected from the ∼2000
    sources which have been observed with the Culgoora circular array at
    80 and 160 MHz during the interval 1970-84. Our results are:
    (i) About 47 per cent of the sample displays significant variability
    on time scales of months or years.
    (ii) A similar degree of variability is shown by QSOs, radio galaxies
    and sources in blank optical fields.
    (iii) Sources with flatter radio spectra are more variable.
    (iv) There is a weak increase in variability for the
    lower-galactic-latitude sources.
    (v) There is a correlation between month-to-month variability and
    year-to year variability in the same sources.
    (vi) The degree of variability at 80MHz is related to that at
    160MHz.
    (vii) Most of the sources in both the variable and non-variable
    categories have a component with angular diameter <1arcsec. Our
    results are partly consistent with an origin in refractive
    scintillation by large-scale electron density turbulence in the
    intervening medium. There are, however, serious difficulties in
    explaining, from the existing theory of slow galactic scintillation,
    the short time-scale of the scintillation. Our results are probably
    more in accord with the focusing and occulting effects of compact
    interstellar ionized structures recently identified at microwave
    frequencies.

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table             99      669   Variability Measurements from the Culgoora
                                  Circular Array


See also:
    VIII/35 : Radio Sources observed with Culgoora Circular Array


Byte-by-byte Description of file: table

   Bytes Format Units   Label     Explanations

   1-  8  A8    ---     Name      Source name
  10- 11  I2    h       RAh       Right ascension (B1950)
  12- 13  I2    min     RAm       Right ascension (B1950)
  14- 17  F4.1  s       RAs       Right ascension (B1950)
      18  A1    ---     DE-       Declination sign
  19- 20  I2    deg     DEd       Declination (B1950)
  21- 22  I2    arcmin  DEm       Declination (B1950)
  23- 24  I2    arcsec  DEs       Declination (B1950)
  26- 29  A4    ---     OptID     Optical Identification
  33- 37  F5.3  ---     z         ? Redshift of optical identification
  39- 43  F5.2  ---     alpha     ? Radio spectral index
  45- 49  F5.1  deg     GLON      Galactic longitude
  51- 55  F5.1  deg     GLAT      Galactic latitude
  58- 62  F5.1  Jy      F80MHz    ? Average flux density at 80 MHz
  64- 65  I2    ---     o_F80MHz  ? Number of observations at F80MHz
  67- 71  F5.2  ---     M1a       ? 1-monthly 80 MHz  modulation index (1)
  73- 77  F5.2  ---     M12a      ? 12-month 80 MHz modulation index (1)
  80- 84  F5.1  Jy      F160MHz   ? Average flux density at 160 MHz
  86- 87  I2    ---    o_F160MHz  ? Number of observations at F160MHz
  89- 93  F5.2  ---     M1b       ? 1-month 160 MHz modulation index (1)
  95- 99  F5.2  ---     M12b      ? 12-month 160 MHz modulation index (1)

Note (1): Variability modulation indices as defined by
          Slee and Siegman (1988MNRAS.235.1313S).
     A value of '-1.00' means that no variability (95% confidence level)
          was detected.
     A blank indicates that the data were not available to test for
          variability.


Acknowledgements: We thank Heinz Andernach  for
    providing an access to his set of radio catalogues (R190), and to 
    Bruce Slee  for his assistance.

References:
   Slee O.B. 1995, Aust. J. Phys., 48, 143            =1995AuJPh..48..143S
   Slee O.B. 1994, Einstein On-line Service, 'radcul80160'
   Slee O.B. et al. 1982, Proc. Astron. Soc. Aust. 4, 278
   Slee O.B. et al. 1983, Proc. Astron. Soc. Aust., 5, 114 =1983PASAu...5..114S
   Slee O.B. and Siegman, B.C. 1988, MNRAS, 235, 1313 =1988MNRAS.235.1313S
(End)                                         Patricia Bauer  [CDS]  21-Aug-1996