Search results for "Jet"
showing 10 items of 4711 documents
The nearest X-ray emitting protostellar jet (HH 154) observed with Hubble
2008
Context. The jet coming from the YSO binary L1551 IRS5 is the closest astrophysical jet known. It is therefore a unique laboratory for studies of outflow mechanisms and of the shocks occurring when expanding material hits the ambient medium as well as of how the related processes influence the star- (and planet-) forming process. Aims. The optical data are related to other data covering the spectrum from the optical band to X-rays with goal of understanding the energetics of low-mass star jets, in general, and of this jet in particular. We study the time evolution of the jet, by measuring the proper motions of knots as they progress outwards from the originating source. Methods. The nebulos…
Examination of the shock wave regular reflexion phenomenon in a rarefied supersonic plasma flow
2005
The flow properties of a low-pressure weakly ionized supersonic argon plasma jet are examined using Fabry–Perot interferometry and laser induced fluorescence spectroscopy. The flow velocity and equilibrium temperature measured at the torch nozzle exit are in close agreement with computational fluid dynamics calculations. The model also predicts the plasma flow to be in a rarefied regime. Departure from thermal equilibrium is indeed observed behind the nozzle where the parallel temperature differs significantly from the perpendicular temperature. The development of the axial velocity component along the jet center stream line reveals the occurrence of the shock wave regular reflexion phenome…
Large-scale jets from active galactic nuclei as a source of intracluster medium heating: cavities and shocks
2014
The evolution of powerful extragalactic jets is not only interesting by itself, but also for its impact on the evolution of the host galaxy and its surroundings. We have performed long-term axisymmetric numerical simulations of relativistic jets with different powers to study their evolution through an environment with a pressure and density gradient. Our results show key differences in the evolution of jets with different powers in terms of the spatial and temporal scales of energy deposition. According to our results, the observed morphology in X-ray cavities requires that an important fraction of the jet’s energetic budget is in the form of internal energy. Thus, light, lepton-dominated …
The nearest X-ray emitting protostellar jet observed with HST
2009
The HH 154 jet coming from the YSO binary L1551 IRS5 is one of the closest (about 150 pc) astrophysical jet known. It is therefore a unique laboratory for studies of outflow mechanisms and of the shocks forming at the interaction front between the expanding material and the ambient medium. The substructures (knots) observed within the HH 154 jet were imaged in several spectral bands using the Hubble Space Telescope. This allows us to derive a simple characterization of the physical conditions in different structures as well as to measure the proper motion of the knots in the jet, their flux variability and shock emission over a time base of about ten years. These knots in the jet undergo si…
Metastable oxygen atom velocity and temperature in supersonic CO2plasma expansions
2008
Radial and axial velocity distribution functions of metastable oxygen atoms were obtained by way of resonant laser induced fluorescence spectroscopy at 777.19 nm in rarefied supersonic plasma jets produced from pure CO2 and CO2–N2 gas mixtures. The N2 seeded fraction is 3% in volume in order to mimic the Martian atmosphere composition. The measured lineshapes allow computation of the mean radial velocity and the perpendicular temperature, with respect to the jet axis, as well as the mean axial velocity and the parallel temperature. With an arcjet plasma source input power of 6.5 kW, the metastable O(5S) atom axial velocity is around 4500 m s−1 and the atom perpendicular temperature reaches …
Recollimation shocks in relativistic jets
2018
Recollimation shocks (RS) appear associated with relativistic flows propagating through pressure mismatched atmospheres. Astrophysical scenarios invoking the presence of such shocks include jets from AGNs and X-ray binaries and GRBs. We shall start reviewing the theoretical background behind the structure of RS in overpressured jets. Next, basing on numerical simulations, we will focus on the properties of RS in relativistic steady jets threaded by helical magnetic fields depending on the dominant type of energy. Synthetic radio maps from the simulation of the synchrotron emission for a selection of models in the context of parsec-scale extragalactic jets will also be discussed.© 2018 World…
Le mobilier numismatique
2013
Determinant factors in the expression of the pronominal subject in spoken Spanish of Valencia
2021
En el presente artículo se estudian los factores determinantes de la presencia del sujeto pronominal en el área metropolitana de Valencia (España). Analizamos fragmentos de habla de un corpus de 72 entrevistas pertenecientes al corpus PRESEVAL, adscrito al grupo PRESEEA. Los resultados muestran la baja tendencia a utilizar la forma expresa (21,8 %). La aparición del sujeto pronominal se ve favorecida por la persona gramatical, muy especialmente la primera del singular, y la clase semántica de los verbos, sobre todo aquellos que indican estados mentales y actividades. Las variables sociales no son especialmente relevantes, si bien el nivel sociocultural y la lengua utilizada (es una comunida…
What drives customer satisfaction and well-being in ridesharing? : A developing country perspective
2019
This study examines ridesharing services from the customer perspective in a developing country context and investigates two significant post-adoption and marketing consequences: satisfaction and well-being. Using a purposeful sampling technique, six semi-structured in-depth interviews were conducted in Sindh province, Pakistan. Among the major findings are that customers’ awareness of the services and how to use the mobile application, convenience of use, high perceived value, the quality of information available in the ridesharing mobile app, real-time location services, and an effective complaint resolution mechanism promote customer satisfaction and well-being. This study includes implic…