INVESTIGADORES
CELLONE Sergio Aldo
artículos
Título:
Optical microvariability of southern AGNs
Autor/es:
ROMERO, G. E.; CELLONE, S. A.; COMBI, J. A.
Revista:
ASTRONOMY & ASTROPHYSICS. SUPPLEMENT SERIES (PRINT)
Editorial:
The European Southern Observatory
Referencias:
Año: 1999 vol. 135 p. 477 - 486
ISSN:
0365-0138
Resumen:
We present results of a search for optical microvariability in a
selected sample of 23 southern AGNs, which includes both radio-quiet and
radio-loud objects. Microvariations were clearly detected in 60% of the
radio-loud sources, with amplitudes from 2.2% up to 8% within a single
night. Night-to-night variability with amplitudes of ~ 20% was also
observed in the BL Lac object 0537-441. On the contrary, no rapid
variability was detected at all in 8 radio-quiet quasars. We have used
microvariability data previously reported for northern objects along
with our new results for southern AGNs in order to estimate duty cycles
of each class of objects from the largest possible sample. Most of the
microvariability in radio-loud objects could be originating in
interactions between relativistic shocks and features in the inner jets,
although contributions from superluminal microlensing and accretion disk
instabilities can be present in some sources. It is possible that the
latter phenomenon is responsible for the microvariability observed in
northern radio-quiet quasars. We suggest that the difference in the
microvariability behaviour of radio and X-ray selected BL Lacs could be
due to the effect of stronger magnetic fields in the latter group of
objects, fields that can prevent the formation of features like density
inhomogeneities and bends in the base of the jets by Kelvin-Helmholtz
macroscopic instabilities.