Multi-wavelength observations of 3C 279 during the extremely bright gamma-ray flare in 2014 March-April

The well studied blazar 3C 279 underwent a giant $\gamma$-ray outburst in 2014 March-April. The measured $\gamma$-ray flux (1.21 $\pm$ 0.10 $\times$ 10$^{-5}$ ph cm$^{-2}$ s$^{-1}$ in 0.1-300 GeV energy range) is the highest detected from 3C 279 by Fermi Large Area Telescope. Hour scale $\gamma$-ray flux variability are observed, with a flux doubling time as short as 1.19 $\pm$ 0.36 hours detected during one flare. The $\gamma$-ray spectrum is found to be curved at peak of the flare suggesting low probability of detecting very high energy (VHE; E $>$ 100 GeV) emission, which is further confirmed by the Very Energetic Radiation Imaging Telescope Array System observations. The $\gamma$-ray flux increased by more than an order in comparison to low activity state and the flare consists of multiple sub-structures having fast rise and slow decay profile. The flux enhancement is seen in all the wavebands though at a lesser extent compared to $\gamma$-rays. During the flare, a considerable amount of the kinetic jet power gets converted to $\gamma$-rays and the jet becomes radiatively efficient. A one zone leptonic emission model is used to reproduce the flare and we find increase in the bulk Lorentz factor as a major cause of the outburst. From the observed fast variability, lack of VHE detection, and the curved $\gamma$-ray spectrum, we conclude that the location of the emission region cannot be far out from the broad line region (BLR) and contributions from both BLR and torus photons are required to explain the observed $\gamma$-ray spectrum.Comment: 42 pages, 8 figures, 7 tables, to appear in the Astrophysical journa

Mass of the black hole in the Seyfert 1.5 galaxy H 0507+164 from reverberation mapping

We present the results of our optical monitoring campaign of the X-ray source H 0507+164, a low luminosity Seyfert 1.5 galaxy at a redshift z = 0.018. Spectroscopic observations were carried out during 22 nights in 2007, from the 21 of November to the 26 of December. Photometric observations in the R-band for 13 nights were also obtained during the same period. The continuum and broad line fluxes of the galaxy were found to vary during our monitoring period. The R-band differential light curve with respect to a companion star also shows a similar variability. Using cross correlation analysis, we estimated a time delay of 3.01 days (in the rest frame), of the response of the broad H-beta line fluxes to the variations in the optical continuum at 5100 angstroms. Using this time delay and the width of the H-beta line, we estimated the radius for the Broad Line Region (BLR) of 2.53 x 10^{-3} parsec, and a black hole mass of 9.62 x 10^{6} solar mass.Comment: 7 pages, 8 figures, Accepted for publication in MNRA