Volume 407, Number 2, August IV 2003
|Page(s)||453 - 460|
|Published online||17 November 2003|
X-ray and optical observations of BL Lac objects: 3C 66A (B0219+428) and ON 325 (B1215+303)
Dipartimento di Fisica, Università “La Sapienza”, Piazzale A. Moro 2, 00185 Roma, Italy
2 ASI Science Data Center, c/o ESA-ESRIN, via G. Galilei, 00044 Frascati, Italy
3 Istituto di Astrofisica Spaziale e Fisica Cosmica, CNR, via del Fosso del Cavaliere 100, 00133 Roma, Italy
4 Osservatorio Astronomico di Brera, via Bianchi 46, 22055 Merate, Italy
5 Department of Physics and Astronomy, Georgia State University, Atlanta GA, USA
Corresponding author: M. Perri, firstname.lastname@example.org
Accepted: 10 June 2003
We report the results of new observations of the two BL Lac objects 3C 66A and ON 325 performed with BeppoSAX and of nearly simultaneous photometric measurements in the bandpasses from I to B. 3C 66A was observed in January 1999 and in July 2001: its X-ray flux was erg cm-2 s-1 in January 1999 and erg cm-2 s-1 in July 2001. In both observations the X-ray spectrum can be fitted by a single power law with an energy index , steeper than that measured in the optical, equal to . The BeppoSAX observation of ON 325 was performed in December 1998 when its X-ray flux was erg cm-2 s-1. The X-ray spectrum cannot be fitted by a single power law, but it is found to be well represented by a broken power law with a break energy at around 4 keV and energy indices equal to and . Both sources are characterised by a synchrotron-dominated emission at energies lower than a few keV, with a sharp flattening toward higher energies due to the inverse Compton component. We obtained satisfactory modelling of the overall spectral energy distributions, from the optical to low energy X-rays, with log-parabolic laws.
Key words: radiation mechanisms: non-thermal / galaxies: active / BL Lacertae objects: individual: 3C 66A, ON 325 / X-rays: galaxies
© ESO, 2003
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.