Manejo agroecológico de la broca del café Hypothenemus hampei

First, we assume a structured (low-luminosity) jet where the Lorentz factor is fixed to Γ = 30. Fig. 6.2 shows the predicted muon neutrino fluence for pure proton injection modelling SGRB 170817A. As shown also in chapter 4, the peak neutrino fluence is not affected by injecting nuclei heavier than protons in GRBs, however the cutoff shifts to lower energies. In this example, an initial baryonic loading of ξA= 100 was used for the computation, as indicated by the scale on the left hand side of the plot. The blue band includes the 1σ uncertainties on the measured duration T90, variability time scale tv, redshift z, gamma-ray fluence Fγ, spectral index α and peak energy Epeak of the target photon spectrum. The gray scale indicates the fraction of the

neutrino fluence directly scales. Demanding super-photospheric emission translates into the red horizontal line, as the photosphere also scales with baryonic loading. According to Eq. (6.11), the maximum baryonic loading is ξ_A,max ∼ 103_{, meaning that the neutrino fluence can be up-}

scaled by a factor 10 at most in this scenario to obtain the maximum possible neutrino fluence for this SGRB in the structured jet internal shock model.

The left panel of Fig. 6.3 shows the impact of the Lorentz factor on the muon neutrino fluence. The red curve corresponds to the case of Γ = 30 as in Fig. 6.2 with the solid curves showing the fluxes for the initial baryonic loading ξA= 100. The figure illustrates how the fluxes scale with Γ according to Eq. (6.9) without imposing any constraints. For large shifts, there is an additional damping of the tail of the spectrum due to fast secondary cooling, which was not considered in the simple analytic estimate. Low values of Γ correspond to efficient neutrino production as the collision radius decreases. On the other hand, the photospheric radius increases, such that low Lorentz factors Γ _{≲ 20 lead to sub-photospheric collisions. This is indicated by the} thin solid curves, whereas the dashed curves represent the maximum neutrino fluence under the photospheric constraint for each case. The fluence for cases with Γ < 20 are scaled down to be in agreement with the photosphere, while in the case of Γ > 20 the fluence is up-scaled as much as it is allowed by the photosphere. Even in the most optimistic case, the neutrino fluence is still three orders of magnitude below the sensitivity of neutrino telescopes, meaning that a neutrino detection of SGRB 170817A was very unlikely in the structured jet scenario.

In the off-axis scenario, the observation angle θ_obs enters as an additional parameter which has an impact on neutrino production and photospheric radius. In the right panel of Fig. 6.3, the dependence of the neutrino fluence on the observation angle is shown with Γ = 30 fixed. Also in this case, the solid curves show the unscaled fluences with the initial baryonic loading of 100, while the dashed curves represent the maximum possible neutrino fluence corresponding to the maximum baryonic loading determined by the photospheric constraint. For this particular choice of Γ, the collisions become sub-photospheric already for θ_{obs ≳ 2}◦. For large observation angles, the fluence will be highly suppressed, making a neutrino detection even less likely than in the structured jet case. The neutrino fluence peaks at a few ×10−5 GeV cm−2 and a baryonic loading ξ_A,max≈ 103_.

In the left panel of Fig. 6.4, we demonstrate how the observation angle θ_obs and the Lorentz factor Γ are constrained by requiring super-photospheric emission. The parameter scan shows the maximum possible baryonic loading such that the collision is just super-photospheric in the internal shock model, as indicated by the contours. We take into account the change of the scaling of the parameters from Eq. (6.5) for large observation angles with the assumption θjet = 1/Γ,

depicted by the white dashed curve. In addition, we show the constraint on these parameters obtained by the time delay t_delay = 1.7 s as calculated in [284], adapted to our parameters.

Figure 6.3: Neutrino fluence (νµ+ ̄νmu) for SGRB 170817A for different values of Γ for a struc- tured jet (left) and for different values of θ_obs for an off-axis jet (right, Γ = 30 fixed). We assume pure proton injection and the same parameters as in Fig. 6.2. For the solid curves, the baryonic loading is fixed to ξA= 100, with thick (thin) curves cor- responding to super-photospheric (sub-photospheric) collisions. The dashed curves show maximized baryonic loading such that R_coll> Rph. Taken from [277].

Compared to the original calculation, we assume a slightly different efficiency ε which leads to a slightly larger allowed region in our plot that is highlighted in white. Compared to this constraint, if we assume the typical baryonic loading of 10 frequently used in the literature, the photospheric limit provides already stronger constraints with θobs≲ 3◦ and Γ≳ 12.

In the right panel of Fig. 6.4, we show all possible neutrino fluences allowed by the photospheric limit in the parameter range of the scan. For each point in the parameter space, the fluence has been computed and re-scaled according to the maximum possible baryonic loading in order to obtain the maximum possible fluence of neutrinos. Any combination of parameters will generate a fluence which lies within the blue shaded uncertainty band. It will not exceed ∼ 5 × 10−5 GeV cm−2 and is therefore about a factor of 10−4 below the sensitivity of neutrino telescopes. It is now clear that since the event was observable in gamma-rays, it is highly unlikely to see any neutrinos from the prompt phase of this SGRB. We also show three explicit example fluences, which occupy different regions of the allowed band. The larger the observation angle, the more the peak is suppressed and the peak energy shifts to lower energies. For the on-axis case, the fluence is the highest, while for intermediate values of Γ and θ_obs the fluence is in-between those extremes. We further show the examples for proton (solid) and iron injection (dashed), which almost give the same result apart from a different cut-off. Note that re-scaling with the

Figure 6.4: Maximum baryonic loading ξ_A,max such that the emission is still super-photospheric as a function of θ_obs and Γ (left) and resulting muon neutrino fluence expected in this region of the parameter space (right). In the left panel, it is assumed that

θjet≃ 1/Γ, i.e., the off-axis scaling changes along the white dashed curve. The black

dashed curve indicates the excluded region of the arrival time constraint [284]. In the right panel, solid curves refer to protons and dashed curves to iron injection. Three particular examples for low, intermediate and high fluence are shown according to the legend, all other parameter combinations are contained in the blue shaded band. The individual curves have been re-scaled with the maximum baryonic loading for each parameter set. Taken from [277].

maximum baryonic loading implies super-photospheric collisions. If this constraint is omitted,

e.g., in a sub-photospheric extrapolation, the neutrino fluence would increase drastically, since

smaller radii lead to much higher radiation densities. However, as indicated by the thin lines in Fig. 6.3, this would still not be enough to reach the sensitivity of any detector.

In conclusion, if GW170817 is a typical neutron star merger, it is highly unlikely that neutrinos will be detected during the prompt emission phase. Nevertheless, certain source properties can be constrained by multi-messenger observations, e.g., the baryonic loading. The jet scenario is still disputed: In the beginning, the situation was very unclear, and low-luminosity jets, off-axis jets, choked jets, or cocoon emission were among the considered scenarios. Some models claim that the radio light curve shows no signature of an off-axis jet afterglow and rather assign the observed gamma-ray emission to cocoon emission [281]. However, recent observations seem to favor the off-axis jet scenario again [290, 291, 292], but overall the situation is still uncertain and will only be clarified by further observations. See also [293, 294] for recent discussions.