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Multifrequency observations of BL Lacertae

Bregman, Joel N. and Matthews, K. (1990) Multifrequency observations of BL Lacertae. Astrophysical Journal, 352 . pp. 574-586. ISSN 0004-637X. doi:10.1086/168559.

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We present 20 years of optical, infrared, and radio monitoring data for BL Lac as well as four simultaneous multifrequency spectra covering the 10^9-10^(18) Hz range. Although there is no time delay between the optical and infrared variability, the high-frequency radio variations precede lower frequency variations, but only by weeks. The optical variability precedes the radio variability by a few years. The structure function for the radio variations is nearly that of shot noise for time scales less than 600 days, in contrast to the optical variation, which is similar to flicker noise. These results indicate that, although there are fundamental differences between the optical and radio emitting regions, they are related, possibly by the propagation of shocks between regions. The multifrequency spectra show that the power per logarithmic bandwidth has a well-defined peak in the near-infrared and a sharp cutoff in the optical-ultraviolet region. This cutoff is like those seen in a few other blazars and is attributed to synchrotron losses that prevent particle acceleration from exceeding a critical energy. The X-ray continuum is not smoothly connected to the optical-ultraviolet emission and has a flatter slope, similar to that of the infrared-millimeter region. In addition, the X-ray emission varied in the same sense as the infrared-millimeter emission but opposite that of the optical-ultraviolet emission. These X-ray properties are those expected from the synchrotron-self-Compton process. The best model suggests that the plasma radiating at ~ 10^(11.5) Hz has a size of ~ 10^(-2·5) pc, a Doppler parameter δ>= 2-3, and a magnetic field of B = 2-40 G.

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Additional Information:© 1990 American Astronomical Society. Received 1989 May 30; accepted 1989 September 28. We would like to thank Rick Howard for using test time to make millimeter measurements of BL Lac and Anne Kinney for-her assistance with IUE data reduction. IUE observing at NYU was supported by NASA grant NAG 5-73; J. N. B. would like to acknowledge support from grant NAG-5-1059; radio astronomy at the University of Michigan is supported by the NSF through grant AST-8501093 and AST-8815678; J. S. M. and S. S. wish to acknowledge Lick Observatory and the NSF for their support; W. A. D., and W. K. have been aided by the NSF and the University of Massachusetts; infrared astronomy at Caltech gratefully acknowledges continued support by the NSF; funding for IRAS observations and data reduction were provided by ESA, SERC, and NASA; W. Z. W. would like to thank Steward observatory for their support. The long-term University of Florida observations have been supported by a series of grants from the NSF; the current grant is AST-8516269.
Funding AgencyGrant Number
European Space Agency (ESA)UNSPECIFIED
Science and Engineering Research Council (SERC)UNSPECIFIED
Steward ObservatoryUNSPECIFIED
Subject Keywords:BL Lacertae objects infrared: sources radiation mechanisms radio sources: galaxies
Record Number:CaltechAUTHORS:20170301-135109574
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Official Citation:Multifrequency observations of BL Lacertae Bregman, J. N., Glassgold, A. E., Huggins, P. J., Neugebauer, G., Soifer, B. T., Matthews, K. Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 352, April 1, 1990, p. 574-586.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74652
Deposited By: Ruth Sustaita
Deposited On:02 Mar 2017 03:48
Last Modified:11 Nov 2021 05:28

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