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Long-duration gamma-ray bursts (GRBs) are powerful cosmic explosions, signaling the death of massive stars. Among them, GRB 221009A is by far the brightest burst ever observed. Because of its enormous energy ( E iso ≈ 10 55 erg) and proximity ( z ≈ 0.15), GRB 221009A is an exceptionally rare event that pushes the limits of our theories. We present multiwavelength observations covering the first 3 months of its afterglow evolution. The x-ray brightness decays as a power law with slope ≈ t -1.66 , which is not consistent with standard predictions for jetted emission. We attribute this behavior to a shallow energy profile of the relativistic jet. A similar trend is observed in other energetic GRBs, suggesting that the most extreme explosions may be powered by structured jets launched by a common central engine.

Long-duration γ-ray bursts (GRBs) originate from ultra-relativistic jets launched from the collapsing cores of dying massive stars. They are characterized by an initial phase of bright and highly variable radiation in the kiloelectronvolt-to-megaelectronvolt band, which is probably produced within the jet and lasts from milliseconds to minutes, known as the prompt emission 1,2 . Subsequently, the interaction of the jet with the surrounding medium generates shock waves that are responsible for the afterglow emission, which lasts from days to months and occurs over a broad energy range from the radio to the gigaelectronvolt bands 1-6 . The afterglow emission is generally well explained as synchrotron radiation emitted by electrons accelerated by the external shock 7-9 . Recently, intense long-lasting emission between 0.2 and 1 teraelectronvolts was observed from GRB 190114C 10,11 . Here we report multi-frequency observations of GRB 190114C, and study the evolution in time of the GRB emission across 17 orders of magnitude in energy, from 5 × 10 -6 to 10 12 electronvolts. We find that the broadband spectral energy distribution is double-peaked, with the teraelectronvolt emission constituting a distinct spectral component with power comparable to the synchrotron component. This component is associated with the afterglow and is satisfactorily explained by inverse Compton up-scattering of synchrotron photons by high-energy electrons. We find that the conditions required to account for the observed teraelectronvolt component are typical for GRBs, supporting the possibility that inverse Compton emission is commonly produced in GRBs.

The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of these unique astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest γ-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the nonthermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons accelerated at an external shock.

Gamma-ray burst (GRB) 130427A is one of the most energetic GRBs ever observed. The initial pulse up to 2.5 seconds is possibly the brightest well-isolated pulse observed to date. A fine time resolution spectral analysis shows power-law decays of the peak energy from the onset of the pulse, consistent with models of internal synchrotron shock pulses. However, a strongly correlated power-law behavior is observed between the luminosity and the spectral peak energy that is inconsistent with curvature effects arising in the relativistic outflow. It is difficult for any of the existing models to account for all of the observed spectral and temporal behaviors simultaneously.

The class of type Ic supernovae have drawn increasing attention since 1998 owing to their sparse association (only four so far) with long duration gamma-ray bursts (GRBs). Although both phenomena originate from the core collapse of a massive star, supernovae emit mostly at optical wavelengths, whereas GRBs emit mostly in soft gamma-rays or hard X-rays. Though the GRB central engine generates ultra-relativistic jets, which beam the early emission into a narrow cone, no relativistic outflows have hitherto been found in type Ib/c supernovae explosions, despite theoretical expectations and searches. Here we report radio (interferometric) observations that reveal a mildly relativistic expansion in a nearby type Ic supernova, SN 2007gr. Using two observational epochs 60 days apart, we detect expansion of the source and establish a conservative lower limit for the average apparent expansion velocity of 0.6c. Independently, a second mildly relativistic supernova has been reported. Contrary to the radio data, optical observations of SN 2007gr indicate a typical type Ic supernova with ejecta velocities approximately 6,000 km s(-1), much lower than in GRB-associated supernovae. We conclude that in SN 2007gr a small fraction of the ejecta produced a low-energy mildly relativistic bipolar radio jet, while the bulk of the ejecta were slower and, as shown by optical spectropolarimetry, mildly aspherical.

A cornerstone of Einstein's special relativity is Lorentz invariance-the postulate that all observers measure exactly the same speed of light in vacuum, independent of photon-energy. While special relativity assumes that there is no fundamental length-scale associated with such invariance, there is a fundamental scale (the Planck scale, l(Planck) approximately 1.62 x 10(-33) cm or E(Planck) = M(Planck)c(2) approximately 1.22 x 10(19) GeV), at which quantum effects are expected to strongly affect the nature of space-time. There is great interest in the (not yet validated) idea that Lorentz invariance might break near the Planck scale. A key test of such violation of Lorentz invariance is a possible variation of photon speed with energy. Even a tiny variation in photon speed, when accumulated over cosmological light-travel times, may be revealed by observing sharp features in gamma-ray burst (GRB) light-curves. Here we report the detection of emission up to approximately 31 GeV from the distant and short GRB 090510. We find no evidence for the violation of Lorentz invariance, and place a lower limit of 1.2E(Planck) on the scale of a linear energy dependence (or an inverse wavelength dependence), subject to reasonable assumptions about the emission (equivalently we have an upper limit of l(Planck)/1.2 on the length scale of the effect). Our results disfavour quantum-gravity theories in which the quantum nature of space-time on a very small scale linearly alters the speed of light.

Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gammaray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass.

Long-duration gamma-ray bursts (GRBs) release copious amounts of energy across the entire electromagnetic spectrum, and so provide a window into the process of black hole formation from the collapse of massive stars. Previous early optical observations of even the most exceptional GRBs (990123 and 030329) lacked both the temporal resolution to probe the optical flash in detail and the accuracy needed to trace the transition from the prompt emission within the outflow to external shocks caused by interaction with the progenitor environment. Here we report observations of the extraordinarily bright prompt optical and gamma-ray emission of GRB 080319B that provide diagnostics within seconds of its formation, followed by broadband observations of the afterglow decay that continued for weeks. We show that the prompt emission stems from a single physical region, implying an extremely relativistic outflow that propagates within the narrow inner core of a two-component jet.

Magnetars are a special class of slowly rotating (period approximately 5-12 s) neutron stars with extremely strong magnetic fields (>10(14 )G)--at least an order of magnitude larger than those of the 'normal' radio pulsars. The potential evolutionary links and differences between these two types of object are still unknown; recent studies, however, have provided circumstantial evidence connecting magnetars with very massive progenitor stars. Here we report the discovery of an infrared elliptical ring or shell surrounding the magnetar SGR 1900+14. The appearance and energetics of the ring are difficult to interpret within the framework of the progenitor's stellar mass loss or the subsequent evolution of the supernova remnant. We suggest instead that a dust-free cavity was produced in the magnetar environment by the giant flare emitted by the source in August 1998. Considering the total energy released in the flare, the theoretical dust-destruction radius matches well with the observed dimensions of the ring. We conclude that SGR 1900+14 is unambiguously associated with a cluster of massive stars, thereby solidifying the link between magnetars and massive stars.

Gamma-ray bursts (GRBs) are known to come in two duration classes, separated at approximately 2 s. Long-duration bursts originate from star-forming regions in galaxies, have accompanying supernovae when these are near enough to observe and are probably caused by massive-star collapsars. Recent observations show that short-duration bursts originate in regions within their host galaxies that have lower star-formation rates, consistent with binary neutron star or neutron star-black hole mergers. Moreover, although their hosts are predominantly nearby galaxies, no supernovae have been so far associated with short-duration GRBs. Here we report that the bright, nearby GRB 060614 does not fit into either class. Its approximately 102-s duration groups it with long-duration GRBs, while its temporal lag and peak luminosity fall entirely within the short-duration GRB subclass. Moreover, very deep optical observations exclude an accompanying supernova, similar to short-duration GRBs. This combination of a long-duration event without an accompanying supernova poses a challenge to both the collapsar and the merging-neutron-star interpretations and opens the door to a new GRB classification scheme that straddles both long- and short-duration bursts.

Soft gamma-ray repeaters (SGRs) are 'magnetars', a small class of slowly spinning neutron stars with extreme surface magnetic fields, B approximately 10(15) gauss (refs 1 , 2 -3). On 27 December 2004, a giant flare was detected from the magnetar SGR 1806-20 (ref. 2), only the third such event recorded. This burst of energy was detected by a variety of instruments and even caused an ionospheric disturbance in the Earth's upper atmosphere that was recorded around the globe. Here we report the detection of a fading radio afterglow produced by this outburst, with a luminosity 500 times larger than the only other detection of a similar source. From day 6 to day 19 after the flare from SGR 1806-20, a resolved, linearly polarized, radio nebula was seen, expanding at approximately a quarter of the speed of light. To create this nebula, at least 4 x 10(43) ergs of energy must have been emitted by the giant flare in the form of magnetic fields and relativistic particles.

Two classes of rotating neutron stars-soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars-are magnetars, whose X-ray emission is powered by a very strong magnetic field (B approximately 10(15) G). SGRs occasionally become 'active', producing many short X-ray bursts. Extremely rarely, an SGR emits a giant flare with a total energy about a thousand times higher than in a typical burst. Here we report that SGR 1806-20 emitted a giant flare on 27 December 2004. The total (isotropic) flare energy is 2 x 10(46) erg, which is about a hundred times higher than the other two previously observed giant flares. The energy release probably occurred during a catastrophic reconfiguration of the neutron star's magnetic field. If the event had occurred at a larger distance, but within 40 megaparsecs, it would have resembled a short, hard gamma-ray burst, suggesting that flares from extragalactic SGRs may form a subclass of such bursts.

The supranova model for gamma-ray bursts (GRBs) is becoming increasingly more popular. In this scenario the GRB occurs weeks to years after a supernova explosion, and is located inside a pulsar wind bubble (PWB). Protons accelerated in the internal shocks that emit the GRB may interact with the external PWB photons producing pions which decay into approximately 10(16) eV neutrinos. A km(2) neutrino detector would observe several events per year correlated with the GRBs.

The supranova model for gamma-ray bursts (GRBs) has recently gained popularity. In this scenario the GRB occurs weeks to years after a supernova explosion, and is located inside a pulsar wind bubble (PWB). High energy protons from the PWB can interact with photons from the rich radiation field inside the PWB or collide with cold protons from the supernova remnant, producing pions which decay into approximately 10-10(3) TeV neutrinos. The predicted neutrino flux from the PWBs that host the GRBs should be easily detectable by planned 1 km(2) detectors.

We discuss the spectrum arising from synchrotron emission by fast cooling (FC) electrons, when fresh electrons are continually accelerated by a strong blast wave, into a power-law distribution of energies. The FC spectrum has so far been described by four power-law segments divided by three break frequencies nusa

This paper reports on 1H and 31P NMR as well as EPR measurements of the labeling reagent of ATPase sites, "Co(III)-(phen)-ATP." This complex is found to be paramagnetic, as deduced both from its EPR spectrum and from the significant broadening, though almost unshifted, proton and phosphorus resonances. This paramagnetism is a result of the incorporation of the superoxide free-radical anion in the coordination sphere of the trivalent cobalt ion. Evidence for the presence of superoxide in the complex is based on competition experiments with cyanide, which is able to displace the superoxide anion. The latter was identified by its inducing effect on the photoreactivity of luminol. The displacement of superoxide by cyanide was accompanied by the abolition of the paramagnetism of the complex. The relative distances between the protons and phosphorus atoms of ATP and the superoxide anion in the complex were calculated using the NMR line-broadening data. Structural models compatible with the experimental results are proposed. Under conditions of excess of adenine nucleotides or phenanthroline, the coordinated ATP molecule becomes exchangeable. This phenomenon is attributed to the labilization of the cobaltic ion ligands induced by the superoxide anion.

6-Hydroxydopamine (I) is a well-known neurocytotoxic agent which has become an important tool in many neurochemical studies in recent years. Biochemical investigations of the mechanism of action of 6-hydroxydopamine indicated that this amine binds covalently and irreversibly to proteins. In the present work, molecular properties of 6-hydroxydopamine in aqueous solution such as self-association, ionization, intramolecular conformations, and possible cyclization were investigated using 1H nuclear magnetic resonance spectroscopy. A model study for the interaction of 6-hydroxydopamine with proteins was undertaken by using SH-containing molecules: cysteine, glutathione, and bovine serum albumin. The binding of these compounds to 6-hydroxydopamine was found to cause labilization of the hydrogen attached to C2 of the amine aromatic ring. This effect was interpreted in terms of nucleophilic attack of RS- on C1 of 6-hydroxydopamine. A proposed model for neurocytotoxicity is discussed.

In vivo sodium magnetic resonance (MR) images of various structures--such as the heart, chest wall, kidneys, spine, liver, gallbladder, breasts, knees, hands, and feet--were obtained at 1.9 T. Improved sensitivity relative to standard spin-echo imaging was achieved with use of a modified three-dimensional acquisition sequence with short repetition and gradient-echo times (45 and 6.4 msec, respectively) and with use of special cylindrical and planar radio-frequency coils. Imaging times of 2-30 minutes were sufficient to render good-quality images with high contrast sensitivity. Relatively strong sodium signals were found to emanate from such sources as cerebrospinal fluid, blood serum, interstitial fluid, joint fluid, and cartilage. It is concluded that sodium imaging of body organs and extremities is feasible and is potentially of clinical diagnostic value, as is the more extensively studied sodium imaging of the head.

Measurements on the thymine imino proton relaxation rates have been used to study various structural and dynamic properties of 53 +/- 15 base pair long poly(dA-dT). Below 10 degrees C, the relaxation is dominated by dipolar magnetic interactions. At 1 degrees C the relaxation of the transverse magnetization is exponential (R2 = 124 s-1), but the relaxation of longitudinal magnetization is highly nonexponential due to spin-diffusion effects (initial decay rate constant of 28 s-1 and a slower rate of approximately 2.5 s-1 after equilibration of spin polarization). Neither a rigid-rod model nor simple wormlike motions can account for the observed low-temperature relaxation behavior. However, when localized internal motions of the base pairs (three-state jump model) are allowed for, a good fit of the experimental data is obtained by using a correlation time for internal motion of 7 X 10(-10) s and an angular displacement of the bases of +/- 32 degrees relative to the helix axis. The observed R2/R1 ratio for the thymine imino proton yields a value of 1.14 +/- 0.08 A for the imino proton nitrogen distance. Nuclear Overhauser effect (NOE) measurements establish that the base pairing in poly(dA-dT) is Watson-Crick in solution and not Hoogsteen. Exchange of the T-imino protons with H2O dominates the longitudinal relaxation above 28 degrees C (activation energy of 17 +/- 2 kcal and an exchange rate of 5 +/- 2 s-1 at 300 K). Similar values have been reported for the A X T base pairs in DNA restriction fragments and for A X U base pairs in poly(A) X poly(U). These observations can be explained by a model in which exchange of T-imino protons occurs as a result of a single base pair opening, with a rate that is approximately independent of nearest-neighbor sequences and DNA length. Our observations appear to be inconsistent with a soliton model of proton exchange.

Co3+ and Cr3+ complexes of beta, gamma-methylene-ATP (AMPPCP), which are substitution-inert substrate analogues inactive in phosphoryl transfer reactions, have been used in binding and structural studies of cAMP-dependent protein kinase. Dissociation constants of enzyme complexes with Co(NH3)4AMPPCP and CrAMPPCP and with Mn2+, which binds at an inhibitory site, were determined by electron paramagnetic resonance and by proton relaxation rate enhancement techniques. Nuclear relaxation rate measurements at 100 and 360 MHz were used to determine the distance between Mn2+ and the beta, gamma-methylene protons of Co-(NH3)4AMPPCP, yielding 7.4 +/- 0.6 A in the absence of enzyme and 5.0 +/- 0.9 A when both Mn2+ and Co-(NH3)4AMPPCP were bound to the enzyme. The effect of the paramagnetic CrAMPPCP on the electron spin relaxation time of the enzyme-bound Mn2+ was used used to calculate the distance between the two metal ions of 4.8 +/- 0.4 A. This distance and the Mn2+-methylene distance are consistent with the previous finding that the inhibitory metal bridges the enzyme to the triphosphate chain of the enzyme-bound nucleotide [Granot, J., Kondo, H., Armstrong, R. M., Mildvan, A. S., & Kaiser, E. T. (1979) Biochemistry 18, 2339]. From the paramagnetic effects on the relaxation rates of the protons of the peptide substrate Leu-Arg-Arg-Ala-Ser-Leu-Gly, distances from Mn2+ and Cr3+ to the serine methylene protons of 9.1 +/- 0.9 and 8.1 +/- 0.8 A, respectively, were calculated. These and previous measurements were used to estimate a distance of 5.3 +/- 0.7 A along the reaction coordinate between the gamma-phosphorus of ATP and the serine hydroxyl oxygen. This distance is 2 A greater than that required for molecular contact. The mechanistic implications of these findings are discussed.