Suzaku Observation of the TeV Blazar 1ES 1218+304: Clues on Particle Acceleration in an Extreme TeV Blazar
Abstract
We observed the TeV blazar 1ES 1218+304 with the X-ray astronomy satellite Suzaku in 2006 May. At the beginning of the 2 day continuous observation, we detected a large flare in which the 5-10 keV flux changed by a factor of ~2 on a timescale of 5 × 104 s. During the flare, the increase in the hard X-ray flux clearly lagged behind that observed in the soft X-rays, with the maximum lag of 2.3 × 104 s observed between the 0.3-1 keV and 5-10 keV bands. Furthermore, we discovered that the temporal profile of the flare clearly changes with energy, being more symmetric at higher energies. From the spectral fitting of multiwavelength data assuming a one-zone, homogeneous synchrotron self-Compton model, we obtain a magnetic field strength B ~ 0.047 G and an emission region size R = 3.0 × 1016 cm for an appropriate beaming with a Doppler factor of δ = 20. This value of B is in good agreement with an independent estimate through the model fit to the observed time lag ascribing the energy-dependent variability to the differential acceleration timescale of relativistic electrons provided that the gyrofactor ξ is 105.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2008
- DOI:
- 10.1086/589689
- Bibcode:
- 2008ApJ...680L...9S
- Keywords:
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- BL Lacertae objects: individual: 1ES 1218+304;
- radiation mechanisms: non-thermal;
- X-rays: galaxies