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Astron. Astrophys. 358, 451-461 (2000)

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1. Introduction

The quasar 0202+149 has an optical spectrum with narrow emission lines typical of low to moderate ionization narrow line radio galaxies (Stickel et al. 1996). There are a few very different estimates of its redshift: [FORMULA] in NED, [FORMULA] (Comastri et al. 1997) and [FORMULA] (Stickel et al. 1996). Since the latter authors derived the redshift from emission lines that they were able to detect, we consider their determination as the most reliable. At optical wavelengths the source has been imaged by Peacock et al. (1981), who find it to be faint and point-like (mR=21.3, Stickel at al. 1996; mv=20.9, Impey & Tapia 1990). The photometric colors in the visible range point to a power law [FORMULA] with index [FORMULA]=2.3 (Fughmann & Meisenheimer 1988). The infrared measurements show very large variations by a factor of [FORMULA] 8 in 1 month and give a power law with [FORMULA]=2.5, both when the source is faint and when it is bright (Stickel et al. 1996). Therefore, the optical and infrared spectra are consistent with each other, although the measurements are not simultaneous. A fairly high level of optical polarization (pmax=4%) was found by Impey & Tapia (1990). The quasar 0202+149 was detected by EGRET as a [FORMULA]-ray source (von Montigny et al. 1995) and classified as a variable source with a high level of probability in the second EGRET catalog (Mattox et al. 1997). In the radio band 0202+149 is classified as a flat-spectrum radio source, with mean spectral index in the region from 400 MHz to 8 GHz equal to [FORMULA]=0.33 (Herbig & Readhead 1992) and average flux density at 5 GHz of [FORMULA]2.7 Jy.

All the aforementioned features of the quasar 0202+149 make it an interesting object for investigation of its detailed VLBI structure. We present geodetic centimeter-wave VLBI observations and high dynamic range millimeter-wave VLBA observations, which, together with the results of more than 20 years monitoring of the flux density at centimeter wavelengths carried out at the University of Michigan Radio Astronomy Observatory (UMRAO, Aller et al. 1985) and at millimeter wavelengths at Metsähovi Radio Research Station (Teräsranta et al. 1992), should allow us to relate individual events to provide a coherent scenario of the source variability.

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© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000