Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Accuracy versus precision in boosted top tagging with the ATLAS detector

Abstract The identification of top quark decays where the top quark has a large momentum transverse to the beam axis, known as top tagging, is a crucial component in many measurements of Standard Model processes and searches for beyond the Standard Model physics at the Large Hadron Collider. Machine learning techniques have improved the performance of top tagging algorithms, but the size of the systematic uncertainties for all proposed algorithms has not been systematically studied. This paper presents the performance of several machine learning based top tagging algorithms on a dataset constructed from simulated proton-proton collision events measured with the ATLAS detector at √ s = 13 TeV. The systematic uncertainties associated with these algorithms are estimated through an approximate procedure that is not meant to be used in a physics analysis, but is appropriate for the level of precision required for this study. The most performant algorithms are found to have the largest uncertainties, motivating the development of methods to reduce these uncertainties without compromising performance. To enable such efforts in the wider scientific community, the datasets used in this paper are made publicly available.</jats:p

Trigeminal Neuralgia

Trigeminal Neuralgia (TN) is the most common cranio-facial pain syndrome, with an incidence of up to 5 in 100,000. Long-term medical treatment is commonly required, with up to 10% of cases suffering adverse drug-related events. In 1951, Lars Leksell pioneered the application of stereotactic irradiation for the treatment of TN, which may now achieve up to 90% pain control at 1 year and 60% at 3-5 years. Radiosurgical treatment targets either the nerve\u2019s emergence (the root entry zone) or the retrogasserian portion of the nerve (pars triangularis). Targeting the latter may reduce the risk of complications, but requires a higher maximum dose to obtain optimal results. Generally speaking, radiosurgical treatment achieves optimal results in patients receiving high doses of radiations ranging from 70 to 90 Gy. Hypoesthesia and facial numbness are frequently observed after high-dose trigeminal irradiation. Mild hypoesthesia is acceptable and is considered by many an efficacy endpoint of the procedure. Bothersome facial numbness is relatively rare. Sensitive trigeminal disturbances and paresthesia after treatment have been reported to range respectively 6%\u201354% and 0%\u201317%. The prescribed dose and brainstem-delivered dose are correlated with the subsequent rate of sensitive trigeminal disturbances. CyberKnife frameless non-isocentric radiosurgery is an emerging and non-invasive treatment for TN. Because of the non-isocentric geometry of radiation beams delivery, CyberKnife technique offers the possibility of homogeneous irradiation of an extended segment of the trigeminal nerve, so introducing some new concepts for the radiosurgical treatment of TN. Clinical results of CyberKnife radiosurgery seems to be satisfactory. We here review the basics of radiosurgery for TN and present a detailed analysis of the technique using the CyberKnife frameless system