Intrinsic Curvature in the X-ray Spectra of BL Lac Objects
Abstract
We report results from XMM-Newton observations of thirteen X-ray bright BL Lacertae objects, selected from the Einstein Slew Survey sample. The survey was designed to look for evidence of departures of their X-ray spectra from a simple power law shape (X-ray spectral curvature and/or spectral line features), and to find objects worthy of deeper study. Our data are generally well fit by power-law models, with four objects having hard (α <1; Fν ∝ ν -α ) spectra that indicate synchrotron peaks at E ≳ 5 keV. None of our spectra show line features, suggesting that such features (which had previously been found in ASCA and BBXRT observations) must be rare amongst BL Lacs, or, more likely, are artifacts caused by instrumental effects. Instead, we find significant, intrinsic curvature in 14 of 17 of the X-ray spectra in our sample, which is seen across the entire XMM-Newton bandpass, from 0.5-6 keV. We derive broadband SEDs and examine models of jet synchrotron emission. We model the spectral curvature we see as the result of intermittent particle acceleration.
- Publication:
-
AAS/High Energy Astrophysics Division #8
- Pub Date:
- August 2004
- Bibcode:
- 2004HEAD....8.0429P