On Energetics and Structure of Sub-parsec Jets in Quasars

This paper reviews the topic of sub-parsec - scale jets in quasars, and covers the the following issues: observations of parsec and sub-parsec scale jets; energy dissipation and particle acceleration; radiative processes; magnetic fields, pair content, and energetics; and variability and its relation to the central engine activity. In particular, we describe how internal shocks can explain properties of gamma-ray flares and demonstrate that MeV blazars (those with luminosity peak in the 1-30 MeV range) can be unified with GeV blazars (those with luminosity peak at GeV energies) assuming that in GeV blazars the gamma-ray flares are produced via Comptonization of broad emission lines, whereas in the MeV blazars they result from Comptonization of infrared radiation of hot dust. We also make predictions about the radiative effects of bulk Compton process in the soft X-ray band and show how spectral and variability properties in that band can be used to constrain structure of jets near their bases.Comment: To appear in the Proceedings of the 2nd KIAS Astrophysics Workshop "Current High Energy Emission Around Black Holes," Seoul, Korea, Sep. 3 - 8, 2001 (15 pages

Recent and Future Observations in the X-ray and Gamma-ray Bands: Chandra, Suzaku, GLAST, and NuSTAR

This paper presents a brief overview of the accomplishments of the Chandra satellite that are shedding light on the origin of high energy particles in astrophysical sources, with the emphasis on clusters of galaxies. It also discusses the prospects for the new data to be collected with instruments recently launched - such as Suzaku - or those to be deployed in the near future, and this includes GLAST and NuSTAR.Comment: To appear in "Astrophysical Sources of High Energy Particles and Radiation", eds. T. Bulik, B. Rudak, and G. Madejski, AIP Conference Proceedings, vol 801 (2005), proc. conf. in Torun, Poland, 20-24 June 200

MAXI and GLAST Studies of Jets in Active Galaxies

The recent launch of Fermi / GLAST - coinciding with the MAXI workshop - opens a new era for studies of jet-dominated active galaxies, known as blazars. While the emission processes operating in various spectral bands in blazars are reasonably well understood, the knowledge of the details of the structure of the jet, location of the dissipation region with respect to the accreting black hole, and coupling of the jet to the accretion process are known only at a rudimentary level. Blazars are variable, and this provides an opportunity to use the variability in various bands - and in particular, the relationship of respective time series to each other - to explore the relative location of regions responsible for emission in the respective bands. Observationally, this requires well-sampled time series in as many spectral bands as possible. To this end, with its all-sky, sensitive monitoring capability, the recently launched GLAST, and MAXI, to be deployed in 2009, are the most promising instruments bound to provide good sampling in respectively the energetic gamma-ray, and the soft X-ray band. This paper highlights the inferences regarding blazar jets that can be gleaned from such joint observations.Comment: Submitted to the proceedings of 3rd MAXI workshop "Astrophysics with All-Sky X-ray Observations," 10-12 June 2008, RIKEN, Wako, Saitama, Japa

Are Quasar Jets Matter or Poynting Flux Dominated?

If quasar jets are accelerated by magnetic fields but terminate as matter dominated, where and how does the transition occur between the Poynting-dominated and matter-dominated regimes? To address this question, we study constraints which are imposed on the jet structure by observations at different spatial scales. We demonstrate that observational data are consistent with a scenario where the acceleration of a jet occurs within 10^{3-4} R_g. In this picture, the non-thermal flares -- important defining attributes of the blazar phenomenon - are produced by strong shocks formed in the region where the jet inertia becomes dominated by matter. Such shocks may be formed due to collisions between the portions of a jet accelerated to different velocities, and the acceleration differentiation is very likely to be related to global MHD instabilities.Comment: to appear in "Astrophysical Sources of High Energy Particles and Radiation", AIP Proceedings Series, eds. T. Bulik, G. Madejski, and B. Rudak (20-24 June 2005, Torun, Poland