Elina Nieppola et al. 2007 The Astronomical Journal 133 1947 doi:10.1086/512609
Elina Nieppola1,2, Merja Tornikoski1, Anne Lähteenmäki1, Esko Valtaoja2,3, Tero Hakala1, Talvikki Hovatta1, Mikko Kotiranta1, Sakari Nummila2, Tapio Ojala2, Mikko Parviainen1, Mikko Ranta2, Pia-Maria Saloranta1,2, Ilona Torniainen1 and Mirko Tröller1
Show affiliationsWe present 37 GHz data obtained at Metsähovi 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 ΔS2 = 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.
BL Lacertae objects: general; galaxies: active; radio continuum: galaxies
Issue 5 (2007 May)
Received 2006 June 21, accepted for publication 2007 January 5
Published 2007 March 21
Elina Nieppola et al. 2007 The Astronomical Journal 133 1947
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