Bibcode
Kidger, M. R.; Takalo, L. O.; de Diego, J. A.
Bibliographical reference
Astronomy and Astrophysics (ISSN 0004-6361), vol. 282, no. 2, p. 369-385
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2
1994
Citations
15
Refereed citations
14
Description
We present results from five nights of pseudo-simulations JHK infrared
monitoring of the blazar OJ 287 taken with the Carlos Sanchez Telescope
during March 1991 with a time resolution of approximately 20 min. The
monitoring shows small amplitude variations in time scales of a few tens
of minutes, which are largest in J. Considerable variations are seen in
the spectra and the spectral index in time scales comparable with our
time resolution. This is the first time that spectral variations have
been observed at any wavelength on such short time scales on OJ 287.
There is a strong correlation between the spectral index and the
intensity in the J-band which also shows significant night to night
variations. We can rule out the cause of the variations being
instrumental, or due to sky transparency variations, with a high degree
of confidence. The spectrum is seen to tilt about a point at
approximately 1.9 micrometers, although the exact value of the
wavelength of the pivotal point varies from night to night. These
observations could be explained by a large, variable magnetic field, in
which the energy spectrum of injected relativistic electrons varies due
to radiative decay on time scales of a few minutes. An alternative, but
less viable explanation, is a two-component model in which a
non-variable component dominates the flux in K and H bands, but the flux
is dominated by a variable emission in the J-band.