Quenchings and outbursts of extragalactic radio sources - Nine years of 3.3-mm measurements and comparisons with centimeter-wave variations
The extragalactic variable radio sources 3C 84, 3C 120, OJ 287, 3C 273, and BL Lac have been observed frequently at 3.3 mm for up to nine years; the results are compared with 19-, 28-, 387, and 45-mm observations. (1) The 3-mm variations are often rapid; significant information is lost if observations are not made every 1-3 days. (2) The correlation between the 3-mm and centimeter-wave variations of these five sources ranges from high to almost nonexistent; in general, the flatter the spectrum, the better the correlation. (3) The relationship between time lag and wavelength for possibly connected outbursts appears to be characteristically different for different objects. (4) No pronounced 3-mm outbursts on a time scale of one to a few days were observed, but three sharp drops or "quenchings" were. A list of other quenchings found in the literature is included. (5) The amplitudes of outbursts vary as λk, where (k ≍ -0.4, from 3.3 to 111 mm, a factor of 34. Results (4) and (5) may place significant new constraints on models.