Probing the Inner Jet of the Quasar PKS 1510-089 with Multi-waveband Monitoring during Strong Gamma-ray Activity (1001.2574v2)

Abstract: We present results from monitoring the multi-waveband flux, linear polarization, and parsec-scale structure of the quasar PKS 1510-089, concentrating on eight major gamma-ray flares that occurred during the interval 2009.0-2009.5. The gamma-ray peaks were essentially simultaneous with maxima at optical wavelengths, although the flux ratio of the two wavebands varied by an order of magnitude. The optical polarization vector rotated by 720 degrees during a 5-day period encompassing six of these flares. This culminated in a very bright, roughly 1 day, optical and gamma-ray flare as a bright knot of emission passed through the highest-intensity, stationary feature (the "core") seen in 43 GHz Very Long Baseline Array images. The knot continued to propagate down the jet at an apparent speed of 22c and emit strongly at gamma-ray energies as a months-long X-ray/radio outburst intensified. We interpret these events as the result of the knot following a spiral path through a mainly toroidal magnetic field pattern in the acceleration and collimation zone of the jet, after which it passes through a standing shock in the 43 GHz core and then continues downstream. In this picture, the rapid gamma-ray flares result from scattering of infrared seed photons from a relatively slow sheath of the jet as well as from optical synchrotron radiation in the faster spine. The 2006-2009.7 radio and X-ray flux variations are correlated at very high significance; we conclude that the X-rays are mainly from inverse Compton scattering of infrared seed photons by 20-40 MeV electrons.

• The paper uses multi-waveband data to link eight major gamma-ray flares with structural changes in the quasar's inner jet.
• It employs high-resolution VLBA imaging and complementary X-ray, optical, and radio measurements to capture dynamic jet behavior.
• Results indicate a spiral motion with a 720-degree polarization rotation and a knot speed of 22c, implicating complex seed photon sources.

Analyzing the Inner Jet Dynamics of Quasar PKS 1510−089 Through Multi-waveband Monitoring

The paper provides an extensive analysis of the multi-frequency observation of the quasar PKS 1510−089, focusing on its behavior during significant gamma-ray activity in 2009. Utilizing data from radio through gamma-ray wavelengths, the paper investigates eight major gamma-ray flares, exploring the spatio-temporal correlation of emissions across different bands and the structural dynamics of the relativistic jet observed in PKS 1510−089 with the Very Long Baseline Array (VLBA) at 43 GHz.

Observation Methodology and Data Analysis

The researchers employed the VLBA for high-resolution radio imaging, the Large Area Telescope (LAT) of the Fermi Gamma-ray Space Telescope for gamma-ray flux measurements, the Rossi X-ray Timing Explorer (RXTE) for X-ray observations, and several other instruments to gather optical and radio data. The data were meticulously processed to generate comprehensive radio imaging and measure various relevant parameters such as flux density, polarization degree, and position angle, across the electromagnetic spectrum.

Results: Dynamics and Mechanisms of Emission

One of the prominent results is the temporal alignment of gamma-ray peaks with optical flux maxima, although their flux ratio showed variability. Remarkably, a 720-degree rotation in the optical polarization vector was detected over a 5-day period encompassing six of the flares. This rotation and the subsequent flares were interpreted as manifestations of a moving emission feature following a spiral trajectory within a toroidal magnetic field structure aligning with the acceleration and collimation zone of the jet. The knot producing these flares was noted to travel downstream at an apparent speed of 22c, continuing to emit gamma-rays as an X-ray and radio outburst increased over months.

Theoretical Implications

The model proposed involved synchrotron and inverse Compton scattering mechanisms, with gamma-ray flares resulting from infrared seed photons scattering and optical synchrotron emission. The paper further established that the behavior and variability observed necessitate local sources of seed photons either within the jet or possibly from a slower sheath surrounding the jet, stressing the necessity of complex internal structure within the jet's relativistic flow to explain the emission phenomena.

Future Prospects

The findings from this research extend the understanding of the physics governing relativistic jets in blazars like PKS 1510−089, particularly through the effects of magnetic field geometry and jet kinematics on observed emissions. Future studies could leverage similar multi-waveband datasets to validate the proposed model across other blazars, potentially assessing the prevalence and nature of spiral jet dynamics and its effect on multi-band emission patterns. This would not only deepen theoretical understanding but also refine models predicting jet behavior during different energetic states.

Overall, while primarily an observational astronomy paper, the work provides rich insights into high-energy astrophysical processes surrounding quasars, offering paths for future empirical and theoretical advancements in understanding relativistic jet flows.