Comparison between TeV and non-TeV BL Lac Objects

Abstract

BL Lacertae objects (BL Lacs) is the dominant population of TeV emitting blazars. In this work, we investigate whether there is any special observational properties for TeV sources. To do so, we will compare the observational properties of TeV detected BL Lacs (TeV BLs) and non-TeV detected BL Lac objects (non-TeV BLs). From the 3rd $Fermi$/LAT catalog (3FGL), we can get 662 BL Lacs, out of which, 47 are TeV BLs and 615 are non-TeV BLs. Their multi-wavelength flux densities ($F_{\rm R}$, $F_{\rm O}$, $F_{\rm X}$, $F_{\gamma}$), photon spectral indexes ($\alpha_{\rm X}^{\rm ph}$, $\alpha_{\gamma}^{\rm ph}$), and effective spectral indexes ($\alpha_{\rm RO}$ and $\alpha_{\rm OX}$) are compiled from the available literatures. Then the luminosities ($\log\,{\nu}L_{\rm R}$, $\log\,{\nu}L_{\rm O}$, $\log\,{\nu}L_{\rm X}$, $\log\,{\nu}L_{\gamma}$) are calculated. From comparisons, we found that TeV BLs are different from low-synchrotron-peaked BLs (LSP) and intermediate-synchrotron-peaked BLs (ISP), but TeV BLs show similar properties as high-synchrotron-peaked BLs (HSP). Therefore, we concentrated on comparison between TeV HSP BLs and non-TeV HSP BLs. Analysis results suggest that TeV HSP BLs and non-TeV HSP BLs show some differences in their $\alpha_{\rm RO}$ and $\alpha_{\gamma}^{\rm ph}$, while their other properties are quite similar.