37 GHz Observations of a Large Sample of BL Lacertae Objects

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...

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Published in:The Astronomical journal 2007-05, Vol.133 (5), p.1947-1953
Main Authors: Nieppola, Elina, Tornikoski, Merja, Lähteenmäki, Anne, Valtaoja, Esko, Hakala, Tero, Hovatta, Talvikki, Kotiranta, Mikko, Nummila, Sakari, Ojala, Tapio, Parviainen, Mikko, Ranta, Mikko, Saloranta, Pia-Maria, Torniainen, Ilona, Tröller, Mirko
Format: Article
Language:English
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Summary: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 S2 = 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.
ISSN:1538-3881
0004-6256
1538-3881
DOI:10.1086/512609