Found 6 talks width keyword supernova remnants
Using ~320h of good-quality Crab data from Feb 2007 to Apr 2014 the MAGIC telescopes measured the most energetic pulsed photons from a pulsar to date. The new results obtained probe the Crab Pulsar as the most compact TeV accelerator known to date. The remarkable detection of pulsed emission up to 1.5 TeV revealed by MAGIC imposes severe constraints on where and how the underlying electron population produces gamma-rays at these energies. Such TeV pulsed photons require a parent population of electrons with a Lorentz factor of at least 5E6. These results strongly suggest IC scattering off low-energy photons as the emission mechanism and a gamma-ray production region in the vicinity of the light cylinder, requiring a revision of the state-of-the-art models proposed to explain how and where gamma-ray pulsed emission from 100 MeV to 1.5 TeV are produced. Investigating the extension of the very high-energy spectral tail of the Crab Pulsar at energies above 400 GeV, the pulse profile was found to show two narrow peaks synchronized with those measured in the GeV energy range. The spectra of the two peaks follow two different power-law functions from 70 GeV up to 1.5 TeV and connect smoothly with the spectra measured above 10 GeV by the Large Area Telescope (LAT) on board the Fermi satellite.
I will describe the roles of jets in several quite different astrophysical systems. These include exploding core collapse supernovae, expelling common envelopes, and heating gas in clusters of galaxies. Hot bubbles inflated by jets seem to be a key ingredient in the interaction of jets with the ambient gas. The understanding that jets can efficiently interact with the ambient gas leads to new notions, such as the jittering jets model to explode massive stars, and the grazing envelope evolution(GEE) that can replace the common envelope evolution in some cases.
I will report on the results of our paper published in Nature this week, outlining the discovery of a super-Chandrasekhar double-degenerate binary system at the heart of the planetary nebula Hen 2-428. Planetary nebulae (PNe) represent the final stage in the evolution of low- and intermediate-mass stars, forming from the mass ejected by the star during its AGB evolution before being ionised by the star's, now exposed, core. As binarity is expected to play a key role in the formation of aspherical PN morphologies, we have been intensively searching for new binary central stars in a push towards a statistical sample. One of our newly-discovered binary systems, lying at the heart of Hen 2-428, had a further surprise to reveal, with observations and modelling showing the system to consist of twin evolved stars with a total mass greater than the Chandrasekhar limit. The short period of the system, only 4.2 hours, means that the two stars will merge together in approximately 700 Myr, resulting in a Supernova Type Ia. While the super-Chandrasekhar merger of two white dwarfs has long been considered a formation pathway for SN Ia, this is the first system found that is confirmed to be both massive enough and in a tight enough orbit to merge in less than a Hubble time.
From the structure of PHL 293B and the physical properties of its ionizing cluster and based on results of hydrodynamic models, we point at the various events required to explain in detail the emission and absorption components seen in its optical spectrum. We ascribe the narrow and well centered emission lines, showing the low metallicity of the galaxy, to an HII region that spans through the main body of the galaxy. The broad emission line components are due to two off-centered supernova remnants evolving within the ionizing cluster volume and the absorption line profiles are due to a stationary cluster wind able to recombine at a close distance from the cluster surface as originally suggested by Silich et al. 2004. Our numerical models and analytical estimates confirm the ionized and neutral column density values and the inferred X-ray emission derived from the observations.
Following the observational and theoretical evidence that points at core collapse supernovae as major producers of dust, we calculate the hydrodynamics of the matter reinserted within young and massive super stellar clusters under the assumption of gas and dust radiative cooling. The large supernova rate expected in massive clusters allows for a continuous replenishment of dust immersed in the high temperature thermalized reinserted matter and warrants a stationary presence of dust within the cluster volume during the type II supernova era (~ 3 Myr - 40 Myr). Such a balance determines the range of dust to gas mass ratio and this the dust cooling law. We then search for the critical line in the cluster mechanical luminosity (or cluster mass) vs cluster size, that separates quasi- adiabatic and strongly radiative cluster wind solutions from the bimodal cases. In the latter, strong radiative cooling reduces considerably the cluster wind mechanical energy output and affects particularly the cluster central regions, leading to frequent thermal instabilities that diminish the pressure and inhibit the exit of the reinserted matter. Instead matter accumulates there and is expected to eventually lead to gravitational instabilities and to further stellar formation with the matter reinserted by former massive stars. The main outcome of the calculations is that the critical line is almost two orders of magnitude or more, depending on the assumed value of V\infty, lower than when only gas radiative cooling is applied. And thus, massive clusters (M_sc > 10^5 Msun) are predicted to enter the bimodal regime.
Long Gamma-Ray Bursts are flashes of high-energy radiation and are linked to the death of massive stars. I will first summarize the main aspects of GRB astronomy, ranging from gamma to infrared frequencies, and secondly I will show how long GRBs pinpoint star-forming galaxies. Afterwards, I will present recent results which indicate as the GRB host population resembles all kind of star-forming galaxies, even the most dusty ones, almost invisible in optical-dedicated surveys.
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- A Tale of Two GalaxiesDr. Knut OlsenTuesday July 24, 2018 - 12:30 (Aula)
- Galaxies in the low-surface-brightness Universe - the new frontier in galaxy evolution studiesDr. Sugata KavirajWednesday July 25, 2018 - 10:30 (Aula)