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 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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table 99 669 Variability Measurements from the Culgoora
Circular Array
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See also:
VIII/35 : Radio Sources observed with Culgoora Circular Array
Byte-by-byte Description of file: table
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Bytes Format Units Label Explanations
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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)
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Note (1): Variability modulation indices as defined by
Slee and Siegman (1988MNRAS.235.1313S 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.
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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 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 1983PASAu...5..114S
Slee O.B. and Siegman, B.C. 1988, MNRAS, 235, 1313 =1988MNRAS.235.1313S 1988MNRAS.235.1313S
(End) Patricia Bauer [CDS] 21-Aug-1996