Variability and Proper Motion of X-ray Knots in the Jet of Centaurus A

Abstract

We report results from Chandra observations analyzed for evidence of variability and proper motion in the X-ray jet of Centaurus A. Using data spanning 15 years, collective proper motion of $11.3\pm 3.3$ mas yr${}^{-1}$, or $0.68\pm 0.20c$, is detected for the fainter X-ray knots and other substructure present within the jet. The three brightest knots (AX1A, AX1C, and BX2) are found to be stationary to an upper limit of $0.10c$. Brightness variations up to 27% are detected for several X-ray knots in the jet. For the fading knots, BX2 and AX1C, the changes in spectral slope expected to accompany synchrotron cooling are not found, ruling it out and placing upper limits of $\simeq 80\mu \mathrm{G}$ for each of their magnetic field strengths. Adiabatic expansion can account for the observed decreases in brightness. Constraints on models for the origin of the knots are established. Jet plasma overrunning an obstacle is favored as the generator of stationary knots, while moving knots are likely produced either by internal differences in jet speed or the late stages of jet interaction with nebular or cloud material.

Accepted to ApJ, 14 pages, 8 figures, 2 tables

References in corpus (13)

• Kinematics of the jet in M87 on scales of 100 -- 1000 Schwarzschild radii
• High-energy particle acceleration at the radio-lobe shock of Centaurus A
• On the deceleration of FRI jets: mass loading by stellar-winds
• New results on particle acceleration in the Centaurus A jet and counterjet from a deep Chandra observation
• TANAMI monitoring of Centaurus A: The complex dynamics in the inner parsec of an extragalactic jet
• Radio observations of active galactic nuclei with mm-VLBI
• Ruling out IC/CMB X-rays in PKS 0637-752 and the Implications for TeV Emission from Large-Scale Quasar Jets
• Internal entrainment and the origin of jet-related broad-band emission in Centaurus A
• Fermi non-detections of four X-ray jet sources and implications for the IC/CMB mechanism
• The infrared jet in Centaurus A: multiwavelength constraints on emission mechanisms and particle acceleration
• Where Centaurus A gets its X-ray knottiness
• The Complex North Transition Region of Centaurus A: A Galactic Wind
• Numerical simulations of shocks encountering clumpy regions

Cited by in corpus (3)

• Detection of Superluminal Motion in the X-Ray Jet of M87
• Non-thermal emission resulting from a supernova explosion inside an extragalactic jet
• The Advanced X-ray Imaging Satellite