15 research outputs found

    Letter to Nature: An ultra-relativistic outflow from a neutron star accreting gas from a companion.

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    Collimated relativistic outflows—also known as jets—are amongst the most energetic phenomena in the Universe. They are associated with supermassive black holes in distant active galactic nuclei1, accreting stellar-mass black holes and neutron stars in binary systems2 and are believed to be responsible for gamma-ray bursts3. The physics of these jets, however, remains something of a mystery in that their bulk velocities, compositions and energetics remain poorly determined. Here we report the discovery of an ultra-relativistic outflow from a neutron star accreting gas within a binary stellar system. The velocity of the outflow is comparable to the fastest-moving flows observed from active galactic nuclei, and its strength is modulated by the rate of accretion of material onto the neutron star. Shocks are energized further downstream in the flow, which are themselves moving at mildly relativistic bulk velocities and are the sites of the observed synchrotron emission from the jet. We conclude that the generation of highly relativistic outflows does not require properties that are unique to black holes, such as an event horizon

    Measurement of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">B</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>8</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math> solar neutrino flux using the full <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>SNO</mml:mi><mml:mo>+</mml:mo></mml:mrow></mml:math> water phase dataset

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    The SNO+ detector operated initially as a water Cherenkov detector. The implementation of a sealed cover gas system midway through water data taking resulted in a significant reduction in the activity of Rn222 daughters in the detector and allowed the lowest background to the solar electron scattering signal above 5 MeV achieved to date. This paper reports an updated SNO+ water phase B8 solar neutrino analysis with a total livetime of 282.4 days and an analysis threshold of 3.5 MeV. The B8 solar neutrino flux is found to be (2.32−0.17+0.18(stat)−0.05+0.07(syst))×106  cm−2 s−1 assuming no neutrino oscillations, or (5.36−0.39+0.41(stat)−0.16+0.17(syst))×106  cm−2 s−1 assuming standard neutrino oscillation parameters, in good agreement with both previous measurements and standard solar model calculations. The electron recoil spectrum is presented above 3.5 MeV. Published by the American Physical Society 2024 </jats:sec

    Initial measurement of reactor antineutrino oscillation at SNO+

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    AbstractThe SNO++ + collaboration reports its first spectral analysis of long-baseline reactor antineutrino oscillation using 114 tonne-years of data. Fitting the neutrino oscillation probability to the observed energy spectrum yields constraints on the neutrino mass-squared difference Δm212\Delta m^2_{21} Δ m 21 2 . In the ranges allowed by previous measurements, the best-fit Δm212\Delta m^2_{21} Δ m 21 2 is (8.851.33+1.108.85^{+1.10}_{-1.33} 8 . 85 - 1.33 + 1.10 ) ×\times × 10510^{-5} 10 - 5 eV2\hbox {eV}^2 eV 2 . This measurement is continuing in the next phases of SNO+ and is expected to surpass the present global precision on Δm212\Delta m^2_{21} Δ m 21 2 with about three years of data.</jats:p

    Event-by-event direction reconstruction of solar neutrinos in a high light-yield liquid scintillator

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    The direction of individual B8 solar neutrinos has been reconstructed using the SNO+ liquid scintillator detector. Prompt, directional Cherenkov light was separated from the slower, isotropic scintillation light using time information, and a maximum likelihood method was used to reconstruct the direction of individual scattered electrons. A clear directional signal was observed, correlated with the solar angle. The observation was aided by a period of low primary fluor concentration that resulted in a slower scintillator decay time. This is the first time that event-by-event direction reconstruction in high light-yield liquid scintillator has been demonstrated in a large-scale detector
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