Search results for "RAV"
showing 10 items of 5866 documents
First M87 Event Horizon Telescope Results. II. Array and Instrumentation
2019
The Event Horizon Telescope (EHT) is a very long baseline interferometry (VLBI) array that comprises millimeter- and submillimeter-wavelength telescopes separated by distances comparable to the diameter of the Earth. At a nominal operating wavelength of ~1.3 mm, EHT angular resolution (λ/D) is ~25 μas, which is sufficient to resolve nearby supermassive black hole candidates on spatial and temporal scales that correspond to their event horizons. With this capability, the EHT scientific goals are to probe general relativistic effects in the strong-field regime and to study accretion and relativistic jet formation near the black hole boundary. In this Letter we describe the system design of th…
First M87 Event Horizon Telescope Results. I. the Shadow of the Supermassive Black Hole
2019
When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42 ± 3 μas, which is circular and encompasses a central depression in brightness with a flux rati…
First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
2019
We present measurements of the properties of the central radio source in M87 using Event Horizon Telescope data obtained during the 2017 campaign. We develop and fit geometric crescent models (asymmetric rings with interior brightness depressions) using two independent sampling algorithms that consider distinct representations of the visibility data. We show that the crescent family of models is statistically preferred over other comparably complex geometric models that we explore. We calibrate the geometric model parameters using general relativistic magnetohydrodynamic (GRMHD) models of the emission region and estimate physical properties of the source. We further fit images generated fro…
Time domain astronomy with the THESEUS satellite
2021
THESEUS is a medium size space mission of the European Space Agency, currently under evaluation for a possible launch in 2032. Its main objectives are to investigate the early Universe through the observation of gamma-ray bursts and to study the gravitational waves electromagnetic counterparts and neutrino events. On the other hand, its instruments, which include a wide field of view X-ray (0.3-5 keV) telescope based on lobster-eye focussing optics and a gamma-ray spectrometer with imaging capabilities in the 2-150 keV range, are also ideal for carrying out unprecedented studies in time domain astrophysics. In addition, the presence onboard of a 70 cm near infrared telescope will allow simu…
Bodegas, lagares y almazaras en el territorio de Kelin (siglos V-III a. C.): el caso de la Rambla de la Alcantarilla (Requena, Valencia)
2016
Archaeological evidences date the expansion of grape vineyards in the territory of the Iberian Iron Age city of Kelin from the 5th to 3rd centuries BC; although the origins are documented in the 7th BC. One of the singularities of this territory is the existence of outdoors stone structures for the production of wine and oil. All are located in a specific area of the territory (la Alcantarilla and Los Morenos ravines) (Requena, Valencia), and are associated with archaeological materials that allow date them as Iberian. In this paper we approach the rural settlement pattern in la Alcantarilla ravine and we present in detail the archaeological sites of Rambla de la Alcantarilla and Solana de …
El yacimiento calcolítico de Karea en el contexto de las cuevas sepulcrales de Gipuzkoa (País Vasco)
2018
En el yacimiento arqueológico de Karea (Aia, Gipuzkoa), integrado por las cavidades contiguas de Karea-A y Karea-B, se recuperaron numerosos restos cerámicos y faunísticos (Karea-A) y vestigios de una inhumación calcolítica (Karea-B). El presente trabajo se ha vertebrado en dos ejes. En primer lugar, el estudio de ambos depósitos mediante diferentes disciplinas: (1) estudio antropológico; (2) estudio del ajuar, compuesto por restos cerámicos y faunísticos; (3) identificación antracológica de los restos leñosos recuperados en el depósito funerario y por último, (4) estudios isotópicos que nos han permitido obtener datos de la alimentación (δ13C y δ15N) y procedencia (87Sr/86Sr) del sujeto in…
Climbing into the past—first Himalayan mummies discovered in Nepal
2003
In a cave system in Mebrak (Mustang District, Western Nepal), a team of archaeologists investigating extensive abandoned settlements in the high Himalayas made an extraordinary discovery in 1995. One of the caves had been used as a community burial chamber from ca. 400 BC to 50 AD. Inside, approximately 30 naturally mummified bodies rested in bed-like wooden coffins exhibiting ornamental carving and elaborate painting. The dead had been furnished with a rich store of grave goods consisting of both personal ornaments and objects of daily life as well as the remains of domestic animals. Due to the favourable climatic conditions, all of the artefacts, which also include fur and textile garment…
Through diachronic discontinuities and regionalization: The contribution of the analysis of the lithic industries from Grotta della Serratura (Strata…
2019
Abstract Within the evolutionary dynamics of post-Gravettian techno-complexes, one can observe an intense regionalization phenomenon, both on a European scale, with the creation of two main provinces, and within the Italian peninsula. To date, typological studies have led to the recognition of several Italian Epigravettian facies, identifying trends, similarities, and differences in the lithic complexes. An important contribution was made by the technological method which in recent years has allowed us to identify the evolutionary processes of the lithic industries in numerous deposits of northern Italy. It is the intent of this reporting to add information which contributes to the debate o…
Last Interglacial Iberian Neandertals as fisher-hunter-gatherers.
2020
Fruits of the sea The origins of marine resource consumption by humans have been much debated. Zilhão et al. present evidence that, in Atlantic Iberia's coastal settings, Middle Paleolithic Neanderthals exploited marine resources at a scale on par with the modern human–associated Middle Stone Age of southern Africa (see the Perspective by Will). Excavations at the Figueira Brava site on Portugal's Atlantic coast reveal shell middens rich in the remains of mollusks, crabs, and fish, as well as terrestrial food items. Familiarity with the sea and its resources may thus have been widespread for residents there in the Middle Paleolithic. The Figueira Brava Neanderthals also exploited stone pine…
Continental-scale temperature variability during the past two millennia
2013
Past global climate changes had strong regional expression. To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia. The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructi…