Astrophysical: BL Lacertae objects

  • Publication
    A fast, very-high-energy γ-ray flare from BL Lacertae during a period of multi-wavelength activity in June 2015
    The mechanisms producing fast variability of the γ-ray emission in active galactic nuclei (AGNs) are under debate. The MAGIC telescopes detected a fast, very...
  • Publication
    A large optical and infrared outburst in OJ 287.
    Extensive infrared observations were taken of OJ 287 in 1993/94 as part of an on-going monitoring campaign of this object started in 1988. The data show that...
  • Publication
    A new analysis of the 11-year period in OJ287 - Confirmation of its existence
    We have compiled all the available optical B band data on OJ287, between 1890 and 1991. Using this data we have found a period of 11.6 +/- 0.5 yr for the...
  • Publication
    A possible method of determining the mass function of BL Lac
    Discrete events with internally consistent properties are found in the light curve of the active galaxy BL Lac, which are consistent with the expected...
  • Publication
    A Search for Spectral Hysteresis and Energy-dependent Time Lags from X-Ray and TeV Gamma-Ray Observations of Mrk 421
    Blazars are variable emitters across all wavelengths over a wide range of timescales, from months down to minutes. It is therefore essential to observe blazars...
  • Publication
    A significant hardening and rising shape detected in the MeV/GeV νFν spectrum from the recently discovered very-high-energy blazar S4 0954+65 during the bright optical flare in 2015 February
    We report on Fermi Large Area Telescope (LAT) and multi-wavelength results on the recently discovered very-high-energy (VHE, E > 100 GeV) blazar S4 0954+65 (z =...
  • Publication
    A statistical study of the optical spectral variability in gamma-ray blazars
    Blazars optical emission is generally dominated by relativistic jets, although the host galaxy, accretion disc, and broad-line region (BLR) may also contribute...
  • Publication
    A study of emission lines variability of the active galaxy PKS 0521-365.
    Optical spectrophotometry of the active galaxy PKS 0521-365 over a period of 7 years is reported, together with the analysis of IUE archival spectra. The Hα...
  • Publication
    A sudden fade of OJ 287
    Optical and radio observations of the BL Lacertae object OJ 287 made early in 1989 show a sudden fade in both wavelength ranges. From January to early April the...