37 GHz observations of a large sample of BL lacertae objects

: Nieppola E, Tornikoski M, Lahteenmaki A, Valtaoja E, Hakala T, Hovatta T, Kotiranta M, Nummila S, Ojala T, Parviainen M, Ranta M, Saloranta PM, Torniainen I, Troller M

Publisher: UNIV CHICAGO PRESS

: 2007

: Bulletin of the American Astronomical Society

: ASTRONOMICAL JOURNAL

: ASTRON J

: 133

: 5

: 1947

: 1953

: 7

: 0004-6256

DOI: https://doi.org/10.1086/512609

We present 37 GHz data obtained at Metsahovi Radio Observatory from 2001 December to 2005 April for a large sample of BL Lacertae objects. We also report the mean variability indices and radio spectral indices in frequency intervals 5-37 and 37-90 GHz. Approximately 34% of the sample was detected at 37 GHz, 136 BL Lacertae objects in all. A large majority of the detected sources were low-energy BL Lac objects. The variability index values of the sample were diverse, the mean fractional variability of the sample being Delta S-2 = 0.31. The spectral indices also varied widely, but the average radio spectrum of the sample sources is flat. Our observations show that many of the high-energy BL Lac objects, which are usually considered radio-quiet, can at times be detected at 37 GHz.