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

La tirannia del trade-off sconfitta? Turismo, ambiente naturale e rifiuti solidi urbani: la ricerca di una ''environmental Kuznet Curve''

Attraverso l impiego della metodologia comune agli studi sulla environmental Kuznets curve, il lavoro intende testare la relazione tra una proxy della ricchezza e un indicatore di qualit� ambientale (la quantit� di rifiuti solidi urbani pro capite) su una data base costruito a livello comunale per 322 comuni della Sardegna. Il modello adottato consente inoltre di testare la validit� di una assunzione comunemente ispiratrice della pianificazione economica - la complementariet� tra specializzazione turistica e conservazione dell ambiente. I risultati dell analisi econometrica confermano che l esistenza di una curva di Kuznets � sensibile sia ai dati impiegati che alla specificazione adottata. Il modello statisticamente preferito mostra che per il particolare indicatore ambientale la relazione � la Kuznets non esiste, confermando un risultato gi� emerso in precedenti studi. Infine, l ipotesi di complementariet� tra turismo e ambiente � rifiutata.

Effects of distance on non-use values

A Choice Modelling (CM) experiment is designed to analyze the relation between Non-Use Values (NUVs) and distance. This issue is relevant in environmental valuation as it can help to identify the relevant market for a given environmental asset and improve individual benefit estimates. The CM experiment extends the literature by designing the environmental attributes so that NUV changes can be disentangled from Use Value (UV) changes. The experiment also allows for a flexible specification of the distance covariates. Data are obtained from a geographically representative sample. We find that NUVs do not depend on distance. Aggregation of NUVs is based on income and individuals’ environmental attitudes.non-use values, choice modelling, experimental design, distance, substitution, information