PERIODIC STRUCTURE IN THE MEGAPARSEC-SCALE JET OF PKS 0637–752
Author(s)Godfrey, L. E. H.; Lovell, J. E. J.; Burke-Spolaor, S.; Ekers, R.; Bicknell, G. V.; Birkinshaw, M.; Worrall, D. M.; Jauncey, D. L.; Schwartz, D. A.; Gelbord, Jonathan; Perlman, E. S.; Georganopoulos, Markos; Marshall, Herman; ... Show more Show less
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We present 18 GHz Australia Telescope Compact Array imaging of the megaparsec-scale quasar jet PKS 0637–752 with angular resolution ~0[" over .]58. We draw attention to a spectacular train of quasi-periodic knots along the inner 11'' of the jet, with average separation ~1.1 arcsec (7.6 kpc projected). We consider two classes of model to explain the periodic knots: those that involve a static pattern through which the jet plasma travels (e.g., stationary shocks) and those that involve modulation of the jet engine. Interpreting the knots as re-confinement shocks implies the jet kinetic power Q [subscript jet] ~ 10[superscript 46] erg s[superscript –1], but the constant knot separation along the jet is not expected in a realistic external density profile. For models involving modulation of the jet engine, we find that the required modulation period is 2 × 10[superscript 3] yr < τ < 3 × 10[superscript 5] yr. The lower end of this range is applicable if the jet remains highly relativistic on kiloparsec scales, as implied by the IC/CMB model of jet X-ray emission. We suggest that the periodic jet structure in PKS 0637–752 may be analogous to the quasi-periodic jet modulation seen in the microquasar GRS 1915+105, believed to result from limit cycle behavior in an unstable accretion disk. If variations in the accretion rate are driven by a binary black hole, the predicted orbital radius is 0.7 pc [< over ~] a [< over ~] 30 pc, which corresponds to a maximum angular separation of ~0.1-5 mas.
DepartmentMIT Kavli Institute for Astrophysics and Space Research
The Astrophysical Journal. Letters
Godfrey, L. E. H., J. E. J. Lovell, S. Burke-Spolaor, R. Ekers, G. V. Bicknell, M. Birkinshaw, D. M. Worrall, et al. “PERIODIC STRUCTURE IN THE MEGAPARSEC-SCALE JET OF PKS 0637–752.” The Astrophysical Journal 758, no. 2 (September 27, 2012): L27. © 2012 The American Astronomical Society
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