Open AccessBeppoSAX observations of 1‐Jy BL Lacertae objects – I
Author(s) -
Padovani Paolo,
Costamante Luigi,
Giommi Paolo,
Ghisellini Gabriele,
Comastri Andrea,
Wolter Anna,
Maraschi Laura,
Tagliaferri Gianpiero,
Megan Urry C.
Publication year - 2001
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2001.04918.x
Subject(s) - physics , astrophysics , rosat , bl lac object , synchrotron , spectral line , blazar , inverse , astronomy , galaxy , optics , gamma ray , geometry , mathematics
We present new BeppoSAX observations of seven BL Lacertae objects selected from the 1‐Jy sample plus one additional source. The collected data cover the energy range (observer's frame), reaching ∼50 keV for one source (BL Lac). All sources characterized by a peak in their multifrequency spectra at infrared/optical energies (i.e., of the low‐energy peaked BL Lac type, LBL) display a relatively flat X‐ray spectrum, which we interpret as inverse Compton emission. Four objects (two‐thirds of the LBLs) show some evidence for a low‐energy steepening, which is probably due to the synchrotron tail merging into the inverse Compton component around ∼. If this were generally the case with LBLs, it would explain why the ROSAT spectra of our sources are systematically steeper than the BeppoSAX ones . The broad‐band spectral energy distributions fully confirm this picture, and a synchrotron inverse Compton model allows us to derive the physical parameters (intrinsic power, magnetic field, etc.) of our sources. Combining our results with those obtained by BeppoSAX on BL Lacs covering a wide range of synchrotron peak frequency, ν peak , we confirm and clarify the dependence of the X‐ray spectral index on ν peak originally found in ROSAT data.