Observations suggest that γ-ray bursts (GRBs) are produced by the dissipation of the kinetic energy of a relativistic fireball. We show that a large fraction, ≥ 10%, of the fireball energy is expected to be converted by photo-meson production to a burst of ∼ 10 14 eV neutrinos. A km 2 neutrino detector would observe at least several tens of events per year correlated with GRBs, and test for neutrino properties (e.g. flavor oscillations, for which upward moving τ 's would be a unique signature, and coupling to gravity) with an accuracy many orders of magnitude better than is currently possible.PACS numbers: 96.40. Tv, 98.70.Rz, 98.70.Sa, 14.60.Pq Recent observations of γ-ray bursts (GRBs) suggest that they originate from cosmological sources [1] (see, however, [2]). General phenomenological considerations indicate that the bursts are produced by the dissipation of the kinetic energy of a relativistic expanding fireball (see [3] for reviews). The physical conditions in the dissipation region imply [4] that protons may be Fermi accelerated in this region to energies > 10 20 eV. Furthermore, the spectrum and flux of ultra-high energy cosmic rays (above 10 19 eV) are consistent with those expected from Fermi acceleration of protons in cosmological GRBs [5]. We show in this Letter that a natural consequence of the dissipative fireball model of GRBs is the conversion of a significant fraction of the fireball energy to an accompanying burst of ∼ 10 14 eV neutrinos, created by photo-meson production of pions in interactions between the fireball γ-rays and accelerated protons. The neutrino burst is produced by interaction with protons with energies much lower than ∼ 10 20 eV, the maximum acceleration energy. As shown below, 10 15 eV protons interact with the ∼ 1MeV photons carrying the bulk of γ-ray energy to produce ∼ 10 14 eV neutrinos.The rapid variability time, ∼ 1ms, observed in some GRBs implies that the sources are compact, with a linear scale r 0 ∼ 10 7 cm. The high luminosity required for cosmological bursts, ∼ 10 51 erg s −1 , then results in an optically thick (to pair creation) plasma, which expands and accelerates to relativistic velocities [6]. The hardness of the observed photon spectra, which extends to ≥ 100MeV, implies that the γ-ray emitting region must be moving with a Lorentz factor Γ of order 100 [7], and constitutes independent evidence for ultra-relativistic outflow. The high energy density in the source would result in complete thermalization and a black-body spectrum [6], in contrast with observations. To overcome this problem, Rees and Mészáros suggested [8] that γ-ray emission results from the dissipation at large radius of the kinetic energy of the relativistic ejecta. Such dissipation is expected to occur due to a collision with the inter-stellar medium [8], or due to internal collisions within the ejecta [9,10].Paczyński and Xu suggested [9], that γ-rays are emitted by the decay of neutral pions, which are produced in pp collisions once the kinetic energy is dissipated through internal c...

Although the link between long gamma-ray bursts (GRBs) and supernovae has been established, hitherto there have been no observations of the beginning of a supernova explosion and its intimate link to a GRB. In particular, we do not know how the jet that defines a gamma-ray burst emerges from the star's surface, nor how a GRB progenitor explodes. Here we report observations of the relatively nearby GRB 060218 (ref. 5) and its connection to supernova SN 2006aj (ref. 6). In addition to the classical non-thermal emission, GRB 060218 shows a thermal component in its X-ray spectrum, which cools and shifts into the optical/ultraviolet band as time passes. We interpret these features as arising from the break-out of a shock wave driven by a mildly relativistic shell into the dense wind surrounding the progenitor. We have caught a supernova in the act of exploding, directly observing the shock break-out, which indicates that the GRB progenitor was a Wolf-Rayet star.

We show that cosmic-ray observations set a model-independent upper bound of E 2 ν Φ ν < 2 × 10 −8 GeV/cm 2 s sr to the intensity of high-energy neutrinos produced by photo-meson (or p-p) interactions in sources of size not much larger than the proton photo-meson (or p-p) mean-freepath. This bound applies, in particular, to neutrino production by either AGN jets or GRBs. The upper limit is two orders of magnitude below the intensity predicted in some popular AGN jet models and therefore contradicts the theory that the cosmic gamma-ray background is due to photo-pion interactions in AGN jets. The upper bound is consistent with our predictions from GRB models. The predicted intensity from GRBs is E 2 dN/dE ∼ 0.3 × 10 −8 GeV/cm 2 s sr for 10 14 eV < E < 10 16 eV; we also derive the expected intensity at higher energy.

We discuss a scenario in which the highest energy cosmic rays (CR's) and cosmological -ray bursts (GRB's) have a common origin.

Spectral analysis of Swift/XRT dataWe use the xspec v11.3.2 X-ray spectral fitting package to fit both a power law and a blackbody model to the XRT outburst data. In both models we allow for excess neutral hydrogen absorption (N H ) above the Galactic value along the line of sight to NGC 2770, N H,Gal = 1.7 × 10 20 cm −2 . The best-fit power law model (χ 2 = 7.5 for 17 degrees of freedom; probability, P = 0.98) has a photon index, Γ = 2.3 ± 0.3 (or, F ν ∝ ν −1.3±0.3 ) and N H = 6.9 +1.8 −1.5 × 10 21 cm −2 . The best-fit blackbody model is described by kT = 0.71 ± 0.08 keV and N H = 1.3 +1.0 −0.9 × 10 21 cm −2 . However, this model provides a much poorer fit to the data (χ 2 = 26.0 for 17 degrees of freedom; probability, P = 0.074). We therefore adopt the power law model as the best description of the data. The resulting count rate to flux conversion is 1 counts s −1 = 5 × 10 −11 erg cm −2 s −1 . The outburst undergoes a significant hard-to-soft spectral evolution as indicated by the ratio of counts in the 0.3 − 2 keV band and 2 − 10 keV band. The hardness ratio decreases from 1.35 ± 0.15 during the peak of the flare to 0.25 ± 0.10 about 400 s later. In the context of the power law model this spectral softening corresponds to a change from Γ = 1.70 ± 0.25 to 3.20 ± 0.35 during the same time interval. High resolution optical spectroscopyWe obtained the spectrum with the High Resolution Echelle Spectrometer (HIRES) mounted on the Keck I 10-m telescope beginning at Jan 17.46 UT. A total of four 1800-s exposures were obtained with a spectral resolution, R = 48, 000, and a slit width of 0.86 arcsec. The data reach a signal-to-noise ratio of 18 per pixel. We reduced the data with the MAKEE reduction package. We are interested in the Na I D and K I absorption features since they are sensitive to the gas column density, and hence extinction, along the line of the sight to the SN. Rejecting a Relativistic Origin for XRO 080109We investigate the possibility that XRO 080109 is the result of a relativistic outflow similar to that in GRBs. In this context the emission is non-thermal synchrotron radiation. The outburst flux density is 7.5 × 10 2 µJy at 0.3 keV. Simultaneously, we find 3σ limits on the flux density in the UBV bands (∼ 3 eV) of F ν < 9.0 × 10 2 µJy, indicating that the peak of the synchrotron spectrum must be located between the UV and X-ray bands. In the standard synchrotron model this requires the frequencies corresponding to electrons with the minimum and cooling Lorentz factors to obey ν m ≈ ν c ≈ 3 × 10 16 Hz, while the peak of the spectrum is F ν,p ≈ 3 mJy.The inferred values of ν m and ν c allow us to constrain 47 the outflow parameters and thus to check for consistency with the hypothesis of relativistic expansion. The relevant parameters are the bulk Lorentz factor (γ), the magnetic field (B), and the shock radius (R sh ). From the value of ν c we find γB 3 ≈ 8.3 × 10 3 , and since γ > 1 we conclude that B < 20 G. In addition, using ν m we find ǫ 2 e γ 3 B ≈ 3 × 10 4 ; here ǫ e is the fraction of posts...