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Astron. Astrophys. 349, 45-54 (1999)

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2. Observational material

This study is based on the light curves of the multi-wavelength database of 3C 273 presented by Türler et al. (1999a). The twelve light curves we use are the five radio light curves: 5 GHz, 8.0 GHz, 15 GHz, 22 GHz and 37 GHz and the seven millimetre/submillimetre (mm/submm) light curves: 3.3 mm, 2.0 mm, 1.3 mm, 1.1 mm, 0.8 mm, 0.45 mm and 0.35 mm. At low frequency (5 to 15 GHz), we consider only the measurements of the University of Michigan Radio Astronomy Observatory (UMRAO). The observations at 22 GHz and 37 GHz are mainly from the Metsähovi Radio Observatory in Finland. The mm/submm observations are from various sources including the James Clerk Maxwell Telescope (JCMT), the Swedish-ESO Submillimetre Telescope (SEST) and the "Institut de Radio-Astronomie Millimétrique" (IRAM).

We analyse the observations from 1979.0 to 1996.6, except at low frequency where we extend the analysis up to: 1997.2 (15 GHz), 1997.5 (8.0 GHz) and 1998.0 (5 GHz), in order to include the decay of the 1995 flare. In the mm/submm range, we average repeated observations made within 3 days to avoid oversampling of the light curves at some epochs. This leaves us a total of 4352 observational points to constrain our fits. To observations without known uncertainties, we assign the average uncertainty of the other observations at the same frequency. The light curves are treated as if all their observations were made exactly at the same frequency, i.e. small differences of the observing frequency from one measurement to the other are not taken into account. This simplification should not much affect the results, since the spectrum is rather flat ([FORMULA]) in the considered submillimetre-to-radio domain (e.g. Türler et al. 1999a).

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© European Southern Observatory (ESO) 1999

Online publication: August 25, 1999