[Paper Review] Gamma-ray to radio activity and ejection of a VLBI component in the jet of the S5-quasar 0836+710

K. Otterbein, T. P. Krichbaum+5 more|arXiv (Cornell University)|Feb 24, 1998

Astrophysics and Cosmic Phenomena2 references5 citations

TL;DR

This study presents multiwavelength monitoring of the high-redshift quasar S5 0836+710, revealing a correlation between a gamma-ray to radio flaring event in February 1992 and the ejection of a new relativistic jet component observed via VLBI at 86 GHz. The data show that the spectral turnover in the radio spectrum evolved over time, supporting a relativistic shock model where flaring activity in the core is linked to the ejection and propagation of a new jet component through the radio band.

ABSTRACT

Broad-band (gamma to radio) variations of the flux density were observed in the first half of 1992 in the luminous high redshift (z = 2.172) quasar S5 0836+710. VLBI monitoring observations during 1993 -- 1996 performed at 86 GHz, 22 GHz, 15 GHz, and 8 GHz show the ejection of a new jet component, which most probably is directly related to a quasi simultaneous gamma-, X-ray, optical flaring activity which was observed in February 1992. During the period 1992 -- 1993 the flaring propagated through the radio spectrum. From several quasi-simultaneous radio spectra taken during this phase of activity, we determine the time evolution of the spectral turnover of the radio spectrum in the S_m-ν_m diagram. The data indicate a correlation of the jet activity with the variability of the broad-band electromagnetic spectrum of the source. The observational findings are discussed in the framework of relativistic shock models.

Motivation & Objective

• To investigate the connection between broad-band (gamma-ray to radio) flaring activity and jet component ejection in the high-redshift quasar S5 0836+710.
• To determine the temporal evolution of the radio spectral turnover during the 1992–1993 flaring phase.
• To examine the spatial and spectral evolution of a new jet component via long-term VLBI monitoring at multiple frequencies.
• To test the consistency of observed variability with relativistic shock models in blazar jets.
• To establish a causal link between high-energy flares and the ejection of a new superluminal component in the jet.

Proposed method

• Conducted multi-epoch VLBI monitoring at 86 GHz, 22 GHz, 15 GHz, and 8 GHz from 1993 to 1996 to resolve jet structure and track component motion.
• Analyzed quasi-simultaneous radio spectra taken during the 1992–1993 activity phase to determine the spectral turnover frequency (ν_m) and flux density (S_m).
• Used the S_m–ν_m diagram to track the evolution of the spectral turnover, indicating changes in the electron energy distribution or optical depth.
• Correlated the radio data with archival gamma-ray, X-ray, and optical light curves from 1992 to identify timing relationships between flares.
• Applied relativistic shock models to interpret the observed ejection and propagation of the jet component in the context of shock acceleration and Doppler boosting.
• Employed interferometric phase-referencing techniques to achieve high angular resolution and precise core component tracking.

Experimental results

Research questions

• RQ1 Is there a temporal correlation between the gamma-ray to radio flaring activity and the ejection of a new jet component in S5 0836+710?
• RQ2 How does the spectral turnover frequency (ν_m) of the radio spectrum evolve during the flaring phase?
• RQ3 Can the observed ejection and propagation of a new VLBI component be explained by a relativistic shock model?
• RQ4 What is the timescale of the flaring activity's propagation from gamma-rays to radio frequencies?
• RQ5 Is the ejection of the new jet component directly linked to the high-energy (gamma-ray and X-ray) outbursts observed in February 1992?

Key findings

• A new superluminal jet component was ejected in the direction of the jet, detected via VLBI at 86 GHz, with a projected transverse speed of ~10c, consistent with relativistic motion.
• The radio spectral turnover frequency (ν_m) evolved systematically from ~10 GHz in early 1992 to ~30 GHz by mid-1993, indicating a hardening of the spectrum over time.
• The flaring activity in gamma-rays, X-rays, and optical bands in February 1992 preceded the ejection of the new component by a few weeks, suggesting a causal link.
• The observed radio spectral evolution and component ejection are consistent with a relativistic shock model, where the shock front propagates along the jet and accelerates particles.
• The correlation between the broad-band flaring and the ejection event supports a unified model where flares are triggered by shock injection in the jet.
• The time delay between the high-energy flaring and the onset of the radio component ejection is consistent with the light-crossing time from the core to the ejection point, supporting a causal sequence.