[seminar] Astro Journal Club on 3 February

[Oskari Miettinen]

Dear all,

Our Astro Journal Club will be held on Wednesday at 3:00 pm in the seminar
room F-201 of the Physics Department. This time we will discuss about the
gamma-ray emission characteristics of the radio quasar 3C454.3.

Presenter: Tea Turkalj
Paper title: Localising the gamma-ray emission region during the June 2014
outburst of 3C 454.3
Authors: Coogan, R. T., Brown, A. M., and Chadwick, P. M.

Summary:
In May - July 2014, the flat spectrum radio quasar 3C 454.3 exhibited
strong flaring behaviour. Observations with the Large Area Telescope
detector on-board the Fermi Gamma-ray Space Telescope captured the
gamma-ray flux at energies 0.1 <= E <=300 GeV increasing fivefold during
this period, with two distinct peaks in emission. The gamma-ray emission
is analysed in detail, in order to study the emission characteristics and
put constraints on the location of the emission region. We explore
variability in the spectral shape of 3C 454.3, search for evidence of a
spectral cutoff, quantify the significance of VHE emission and investigate
whether or not an energy-dependence of the emitting electron cooling
exists. Gamma-ray intrinsic doubling timescales as small as tau_int =
0.68+/-0.01 h at a significance of > 5sigma are found, providing evidence
of a compact emission region. Significant E>=35 GeV and E>=50 GeV emission
is also observed. The location of the emission region can be constrained
to r>=1.3xR_BLR^out, a location outside the broad-line region. The
spectral variation of 3C 454.3 also suggests that these flares may be
originating further downstream of the supermassive black hole than the
emission before and after the flares.

Link to the paper: http://adsabs.harvard.edu/abs/2016arXiv160107180C

Hope to see you all on Wednesday!

Cheers,
Oskari