Evidence of two spectral breaks in the prompt emission of gamma ray bursts

The long-lasting tension between the observed spectra of gamma ray bursts (GRBs) and the predicted synchrotron emission spectrum might be solved if electrons do not completely cool. Evidence for incomplete cooling was recently found in Swift GRBs with prompt observations down to 0.1 keV and in one bright Fermi burst, GRB 160625B. Here we systematically search for evidence of incomplete cooling in the spectra of the ten brightest short and long GRBs observed by Fermi. We find that in 8/10 long GRBs there is compelling evidence of a low energy break (below the peak energy) and good agreement with the photon indices of the synchrotron spectrum (respectively -2/3 and -3/2 below the break and between the break and the peak energy). Interestingly, none of the ten short GRBs analysed shows a break but the low energy spectral slope is consistent with -2/3. In a standard scenario, these results imply a very low magnetic field in the emission region (B' ~ 10 G in the comoving frame), at odd with expectations.Comment: 14 pages, 15 figures, in press, accepted for publication in A&

Cost-effectiveness analysis of alectinib versus crizotinib in first-line treatment of anaplastic lymphoma kinase-positive advanced non-small cell lung cancer:

In the randomized, active-controlled, multicenter Phase III open-label ALEX trial, alectinib showed superior efficacy and lower toxicity compared with crizotinib in the primary treatment of anaplastic lymphoma kinase-positive non-small cell lung cancer (ALK-positive NSCLC). The aim of this economic evaluation was to assess the cost-utility of alectinib versus crizotinib from the perspective of the Italian National Health Service (INHS). A partitioned survival model with three health states (progression-free, post-progression, and death) was used. The clinical data (progression-free survival, overall survival and time to progression) was based on the ALEX trial. Utility values were derived from EQ-5D scores evaluated in the ALEX trial and literature. Costs included drug treatments, progression-free, post-progression and supportive care. Direct medical costs and benefits (quality-adjusted life-years, QALYs) were discounted at a 3.0% annual rate. Uncertainty was assessed using deterministic and probabilistic sensitivity analyses. Treatment with alectinib versus crizotinib led to a gain of 2.82 life-years, 1.86 QALYs, and incremental costs of €58,276, resulting in an incremental cost-utility ratio of €31,353 per QALY. The deterministic analysis showed that the most critical parameters in the model were the cost of post-progression and utility scores. From the probabilistic sensitivity analysis, alectinib had a 64.5% probability of being cost-effective at a willingness-to-pay threshold of €40,000 per QALY. Compared with crizotinib, alectinib increased the length of the progression-free state and the QALYs. The incremental overall cost increase was reflective of longer treatment durations in the progression-free state. Compared with crizotinib, alectinib can be considered a valid cost-utility option in the treatment of naive patients with ALK-positive NSCLC

The long-term optical spectral variability of BL Lacertae

We present the results from a study of the long-term optical spectral variations of BL Lacertae, using the long and well-sampled B and R-band light curves of the Whole Earth Blazar Telescope (WEBT) collaboration, binned on time intervals of 1 day. The relation between spectral slope and flux (the spectrum gets bluer as the source flux increases) is well described by a power-law model, although there is significant scatter around the best-fitting model line. To some extent, this is due to the spectral evolution of the source (along well-defined loop-like structures) during low-amplitude events, which are superimposed on the major optical flares, and evolve on time scales of a few days. The "bluer-when-brighter" mild chromatism of the long-term variations of the source can be explained if the flux increases/decreases faster in the B than in the R band. The B and R-band variations are well correlated, with no significant, measurable delays larger than a few days. On the other hand, we find that the spectral variations lead those in the flux light curves by ~ 4 days. Our results can be explained in terms of Doppler factor variations due to changes in the viewing angle of a curved and inhomogeneous emitting jet.Comment: 7 pages, 5 figures, accepted for publication in A&

Budget Impact Model of Omalizumab In The Treatment of Chronic Spontaneous Urticaria In Italy

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The short gamma-ray burst population in a quasi-universal jet scenario

We describe a model of the short gamma-ray burst (SGRB) population under a `quasi-universal jet' scenario in which jets can differ in their on-axis peak prompt emission luminosity $L_c$, but share a universal angular luminosity profile $\ell(\theta_v)=L(\theta_v)/L_c$ as a function of the viewing angle $\theta_v$. The model is fitted, through a Bayesian hierarchical approach inspired by gravitational wave (GW) population analyses, to 3 observed SGRB samples simultaneously: the Fermi/GBM sample of SGRBs with spectral information in the catalogue (367 events); a flux-complete sample of 16 Swift/BAT SGRBs also detected by GBM, with a measured redshift; and a sample of SGRBs with a binary neutron star (BNS) merger counterpart, which only includes GRB~170817A at present. The results favour a narrow jet core with half-opening angle $\theta_c=2.1_{-1.4}^{+2.4}$ deg (90\% credible intervals from our fiducial `full sample' analysis) whose on-axis peak luminosity is distributed as $p(L_c) \propto L_c^{-A}$ with $A=3.2_{-0.4}^{+0.7}$ above a minimum luminosity $L_c^\star = 5_{-2}^{+11}\times 10^{51}$ erg s$^{-1}$. For $\theta_v>\theta_c$, the luminosity scales as a power law $\ell\propto \theta_v^{-\alpha_L}$ with $\alpha_L=4.7_{-1.4}^{+1.2}$, with no evidence for a break. While the model implies an intrinsic `Yonetoku' correlation between $L$ and the peak photon energy $E_p$, its slope is somewhat shallower $E_p\propto L^{0.4\pm 0.2}$ than the apparent one, and the normalization is offset towards larger $E_p$, due to selection effects. The implied local rate density of SGRBs is between about 100 up to several thousands of events per Gpc$^{3}$ yr, in line with the BNS merger rate density inferred from GW observations. Based on the model, we predict 0.2 to 1.3 joint GW+SGRB detections per year by the Advanced GW detector network and Fermi/GBM during the O4 observing run.Comment: 30 pages, 23 figures, submitted to A&A. Comments are welcome

Four-lepton production in gluon fusion at NLO matched to parton showers

We present a calculation of the next-to-leading order (NLO) QCD corrections to gluon-induced electroweak gauge boson pair production, $gg \to ZZ$ and $gg \to W^+W^-$, matched to the PYTHIA8 parton shower in the POWHEG approach. The calculation consistently incorporates the continuum background, the Higgs-mediated $gg\to H^* \to VV$ process, and their interference. We consider leptonic decay modes of the massive vector bosons and retain offshell and non-resonant contributions. The processes considered are loop-induced at leading order and thus contain two-loop virtual contributions as well as loop-squared real contributions. Parton-shower effects are found to be marginal in inclusive observables and quite sizeable in observables that are exclusive in additional jet radiation. The Monte Carlo generator presented here allows for realistic experimental effects to be incorporated in state-of-the-art precision analyses of diboson production and of the Higgs boson in the offshell regime.Comment: 15 pages, 13 figures, 1 tabl

Internal shocks in relativistic outflows: collisions of magnetized shells

(Abridged): We study the collision of magnetized irregularities (shells) in relativistic outflows in order to explain the origin of the generic phenomenology observed in the non-thermal emission of both blazars and gamma-ray bursts. We focus on the influence of the magnetic field on the collision dynamics, and we further investigate how the properties of the observed radiation depend on the strength of the initial magnetic field and on the initial internal energy density of the flow. The collisions of magnetized shells and the radiation resulting from these collisions are calculated using the 1D relativistic magnetohydrodynamics code MRGENESIS. The interaction of the shells with the external medium prior to their collision is also determined using an exact solver for the corresponding 1D relativistic magnetohydrodynamic Riemann problem. Our simulations show that two magnetization parameters - the ratio of magnetic energy density and thermal energy density, \alpha_B, and the ratio of magnetic energy density and mass-energy density, \sigma - play an important role in the pre-collision phase, while the dynamics of the collision and the properties of the light curves depend mostly on the magnetization parameter \sigma. The interaction of the shells with the external medium changes the flow properties at their edges prior to the collision. For sufficiently dense shells moving at large Lorentz factors (\simgt 25) these properties depend only on the magnetization parameter \sigma. Internal shocks in GRBs may reach maximum efficiencies of conversion of kinetic into thermal energy between 6% and 10%, while in case of blazars, the maximum efficiencies are \sim 2%.Comment: 17 pages, 18 figures. 2 new references have been added. Accepted for publication in Astronomy and Astrophysic