Optical variability of PKS 0736+017

Free access article

Issue		A&A Volume 421, Number 1, July I 2004


Page(s)		83 - 89
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20034449

A&A 421, 83-89 (2004)
DOI: 10.1051/0004-6361:20034449

Optical variability of PKS 0736+017

A. Ramírez¹, J. A. de Diego¹, D. Dultzin-Hacyan¹ and J. N. González-Pérez^{2, 3}

¹ Instituto de Astronomía, UNAM, Apdo. 70-264, Ciudad Universitaria, 04510 México, D.F., México
e-mail: [aramirez;jdo;deborah]@astroscu.unam.mx
² Universität Hamburg, Hamburger Sternwarte, Gojenbergsweg 112, 21029, Hamburg, Germany
³ Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
e-mail: st1h317@hs.uni-hamburg.de

(Received 6 October 2003 / Accepted 29 November 2003)

Abstract
We present BVR photometric observations of the blazar PKS 0736+017 . These observations were carried out with three telescopes in Mexico and two in Spain between December 1998 and April 2003. PKS 0736+017 shows remarkable variation at different timescales and amplitudes. Maximum brightness was detected on December 19, 2001 ( $B=14.90\pm 0.01$ , $V=14.34\pm0.01$ , and $R=13.79\pm 0.01$ ). A peculiar tendency to redden with increased brightness was detected throughout our observations. Moreover, in one season a good correlation between flux level and spectral slope is shown. This anomalous behaviour cannot be described by common flare models of blazars. The flux vs. spectral slope correlation observed in this and other blazars is worth further study.

Key words: Blazar -- PKS 0736+017 -- radiation mechanisms -- variability

Offprint request: A. Ramírez, aramirez@astroscu.unam.mx

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