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Spectral Variability of BL Lac Objects

Published online by Cambridge University Press:  05 March 2013

R. D'Amicis ,
R. Nesci ,
E. Massaro ,
M. Maesano ,
F. Montagni  and
F. D'Alessio
R. D'Amicis
Affiliation:
Department of Physics, University La Sapienza, P.le Aldo Moro 2, I-00185 Roma, Italy
R. Nesci
Affiliation:
Department of Physics, University La Sapienza, P.le Aldo Moro 2, I-00185 Roma, Italy; Roberto.Nesci@uniroma1.it
E. Massaro
Affiliation:
Department of Physics, University La Sapienza, P.le Aldo Moro 2, I-00185 Roma, Italy
M. Maesano
Affiliation:
Department of Physics, University La Sapienza, P.le Aldo Moro 2, I-00185 Roma, Italy
F. Montagni
Affiliation:
Department of Physics, University La Sapienza, P.le Aldo Moro 2, I-00185 Roma, Italy
F. D'Alessio
Affiliation:
Osservatorio Astronomico di Roma, via di Frascati 33, I-00040 Monteporzio Catone (Roma), Italy; dalessio@coma.mporzio.astro.it
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Abstract

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We present the relation between optical luminosity and spectral slope for eight BL Lac objects (3C66A, PKS 0422+00, S5 0716+71, OJ 287, ON 231, OQ 530, S5 1803+78 and BL Lacertae), derived from B, V, R, and I observations spanning a time interval of about 5 years. Four objects show a marked correlation between spectral slope and luminosity, being bluer when brighter, while for the other four the correlation is weaker or absent. Possible explanations are briefly discussed in the framework of current models of the BL Lac phenomenon.

Keywords

BL Lacertae objects: individual (3C 66A, PKS 0422+004, S5 0716+71, OJ 287, ON 231, OQ 530, S5 1803+78, BL Lac)
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 19 , Issue 1 , 2002 , pp. 111 - 113
Copyright
Copyright © Astronomical Society of Australia 2002

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