The stellar occultation by (319) Leona on 2023 September 13 in preparation for the occultation of Betelgeuse

peer reviewedOn 2023 December 12, the star α Orionis will be occulted by asteroid (319) Leona. This represents an extraordinary and unique opportunity to analyse the brightness distribution of Betelgeuse's photosphere with extreme angular resolution by studying light curves from different points on Earth and at different wavelengths. Here we present observations of another occultation by asteroid Leona, on 2023 September 13, whose goal was to determine Leona's projected shape and size in preparation for the December 12th event and its interpretation. The occultation campaign was highly successful with 25 positive detections from 17 different sites and a near miss. The effective diameter in projected area derived from the positive detections was 66 ± 2 km using an elliptical fit to the instantaneous limb. The body is highly elongated, with dimensions of 79.6 ± 2.2 km × 54.8 ± 1.3 km in its long and short axis, respectively, at occultation time. This result, in combination with dense time series photometry of Leona that we recently obtained, together with archival sparse photometry, allowed us to predict the angular size of the asteroid for the Betelgeuse event and to simulate the expected brightness change. Also, an accurate position coming from the occultation is provided, to improve the orbit of Leona

Mapping the vulnerability for evacuation of the Campi Flegrei territorial system in case of a volcanic unrest

Over the past few decades the Campi Flegrei territorial system was interested by intense urban expansion overlooking the volcanic risk. In this active volcanic area, where a short period evacuation could be necessary, the emergency management cannot be based solely on the hazard related information, but the territorial and social features must be as well taken into account. In this framework, the main purpose of this research is to point out the seriousness of the present setting of Campi Flegrei territorial system in case an evacuation would become necessary. Following the concept of regional evacuation, the zone to be involved in emergency planning was identified as the whole of the area threatened by the volcanic events occurred in the last 10 ka. Inside this area the spatial relation between the residents distribution and the outflows of routes, railway stations and harbours, necessary to leave the dangerous area, was investigated. A spatial relational GIS-based procedure was used to draw the territorial system vulnerability map for evacuation, depicting the zones with different capability to support the evacuation of residents in case of renewal of volcanic activity. Basing on the concept that people could leave the dangerous area by the means of transport supplied by Civil Protection, and using the threshold value of over-crowding of 0,70 people/ m2, we identified the collection points for residents to be immediately evacuated in case of volcanic unrest, and five microzones displaying different capability to cope with an emergency phase