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Photohadronic neutrinos from transients in astrophysical sources

“…The target photon spectrum in the comoving frame of the relativistic flow can then be approximated by a power law with a typical index a ≈ 1.7, if we use a power law interpolation between the sub-mm and X-ray wave bands [47], ignoring the observed break at optical frequencies; this is also justified by the observation that in flares the important optical-to-X-ray spectrum of low luminosity blazars seems to be flatter than the typical a oX ≈ 2 seen in the quiescent state [40,50,51]. In the following, we adopt a = 5 3 and introduce the Doppler factor and magnetic field in canonical units, D 1 ≡ D/10, and B 1 = B/10 G. For the break energy we use ε b ∼ 10 −4 eV [47], andε ∼ 1−10 keV from X-ray observations of flares in Mkn 421 and Mkn 501 [40,52], leading to b ph ∼ 10 3 . The luminosity at the spectral break is not taken from observed fluxes at ε b , because the emission at low energy is likely to be superposed by the emission from other jet regions not associated with the flare; rather, we use the observed, isotropized X-ray luminosity at ε X ≈ 1 keV of the flare, L X = [10 45 erg/s]L X,45 , and determine L b from scaling with the assumed power law photon spectrum, L b = L X,45 (ε b /ε X ) 1/3 ; note that b ph L b ∼ 3L X .…”

Radio pulsars: the search for truth

“…On the other hand, as is well known, another important channel in which energy is released and which is capable of resulting in the production of γ-quanta of even higher energies is the inverse Compton scattering of thermal X-ray photons emitted from the surface of a neutron star. This process has recently been regarded as the main process for the generation of photons of energies in the TeV range for the widest class of objects, such as active galactic nuclei [79,80], galactic sources in the TeV range [81], and, naturally, radio pulsars [82]. In those cases where the 'central engine' is indeed a rapidly rotating neutron star, the Lorentz factor of electrons (or positrons) necessary for shifting the observed photons and soft γ-quanta toward the TeV energies corresponds precisely to values γ = 10 4 -10 5 .…”

Multiwavelength variability of blazars

“…In 1994 and 1995 the X-ray observations were perfomed with the ASCA satellite indicating a general correlation betwen the X-ray and TeV variability with similar amplitude. An important result of the 1994 observations was the detection of a "soft lag", that is soft X-rays appeared to lag the medium X-ray light curve by 2.5 ksec (Takahashi et al 1996).…”