The Doppler factors at X-ray band of the blazars

摘要

We study the Doppler factors for a group blazars at soft X-ray band. In our estimates, we have made the assumptions that (i) blazars can be divided into high-energy-peaked (HEP) objects whose synchrotron peak frequencies v(p) > 10(14.7) Hz, and the low-energy-peaked (LEP) objects whose synchrotron peak frequencies v(p) <= 10(14.7) Hz, and (ii) the intrinsic radiation from a blazar in the energy range from radio to soft X-ray bands is the synchrotron radiation for HEP objects and the soft X-ray emission comes from inverse Compton scattering for LEP objects. Under the above assumptions, we estimate Doppler factors at optical (delta(O)) and X-rays (delta(x)) for 54 blazars by using the known radio Doppler factors and the observed flux densities in radio, optical and X-ray bands, and Doppler factors (delta(x)(syn)) at X-ray band in which X-rays are assumed to be produced only by the synchrotron radiation. We get delta(x)(syn) > delta(x). The Doppler factors are different in various wavebands, and on average, the Doppler factor decreases with frequency from radio to X-ray bands.