ALBERT

Description: An unresolved X-ray glow (at energies above a few kiloelectronvolts) was discovered about 25 years ago and found to be coincident with the Galactic disk-the Galactic ridge X-ray emission. This emission has a spectrum characteristic of a approximately 10(8) K optically thin thermal plasma, with a prominent iron emission line at 6.7 keV. The gravitational well of the Galactic disk, however, is far too shallow to confine such a hot interstellar medium; instead, it would flow away at a velocity of a few thousand kilometres per second, exceeding the speed of sound in the gas. To replenish the energy losses requires a source of 10(43) erg s(-1), exceeding by orders of magnitude all plausible energy sources in the Milky Way. An alternative is that the hot plasma is bound to a multitude of faint sources, which is supported by the recently observed similarities in the X-ray and near-infrared surface brightness distributions (the latter traces the Galactic stellar distribution). Here we report that at energies of approximately 6-7 keV, more than 80 per cent of the seemingly diffuse X-ray emission is resolved into discrete sources, probably accreting white dwarfs and coronally active stars.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Revnivtsev, M -- Sazonov, S -- Churazov, E -- Forman, W -- Vikhlinin, A -- Sunyaev, R -- England -- Nature. 2009 Apr 30;458(7242):1142-4. doi: 10.1038/nature07946.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Excellence Cluster Universe, Technische Universitat Munchen, 85748, Garching, Germany. mikej@mpa-garching.mpg.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19407795" target="_blank"〉PubMed〈/a〉

Description: A type Ia supernova is thought to be a thermonuclear explosion of either a single carbon-oxygen white dwarf or a pair of merging white dwarfs. The explosion fuses a large amount of radioactive (56)Ni (refs 1-3). After the explosion, the decay chain from (56)Ni to (56)Co to (56)Fe generates gamma-ray photons, which are reprocessed in the expanding ejecta and give rise to powerful optical emission. Here we report the detection of (56)Co lines at energies of 847 and 1,238 kiloelectronvolts and a gamma-ray continuum in the 200-400 kiloelectronvolt band from the type Ia supernova 2014J in the nearby galaxy M82. The line fluxes suggest that about 0.6 +/- 0.1 solar masses of radioactive (56)Ni were synthesized during the explosion. The line broadening gives a characteristic mass-weighted ejecta expansion velocity of 10,000 +/- 3,000 kilometres per second. The observed gamma-ray properties are in broad agreement with the canonical model of an explosion of a white dwarf just massive enough to be unstable to gravitational collapse, but do not exclude merger scenarios that fuse comparable amounts of (56)Ni.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Churazov, E -- Sunyaev, R -- Isern, J -- Knodlseder, J -- Jean, P -- Lebrun, F -- Chugai, N -- Grebenev, S -- Bravo, E -- Sazonov, S -- Renaud, M -- England -- Nature. 2014 Aug 28;512(7515):406-8. doi: 10.1038/nature13672.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Space Research Institute (IKI), Profsouznaya 84/32, Moscow 117997, Russia [2] Max Planck Institute for Astrophysics, Karl-Schwarzschild-Strasse 1, 85741 Garching, Germany. ; Institute for Space Sciences (ICE-CSIC/IEEC), 08193 Bellaterra, Spain. ; 1] Universite de Toulouse, UPS-OMP, IRAP, Toulouse, France [2] CNRS, IRAP, 9 Avenue colonel Roche, BP 44346, F-31028 Toulouse Cedex 4, France. ; APC, Universite Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cite, 75205 Paris Cedex 13, France. ; Institute of Astronomy of the Russian Academy of Sciences, 48 Pyatnitskaya Street, 119017 Moscow, Russia. ; Space Research Institute (IKI), Profsouznaya 84/32, Moscow 117997, Russia. ; ETSAV, Universitat Politecnica de Catalunya, Carrer Pere Serra 1-15, 08173 Sant Cugat del Valles, Spain. ; 1] Space Research Institute (IKI), Profsouznaya 84/32, Moscow 117997, Russia [2] Moscow Institute of Physics and Technology, Institutsky pereulok 9, 141700 Dolgoprudny, Russia. ; LUPM, Universite Montpellier 2, CNRS/IN2P3, CC 72, Place Eugene Bataillon, F-34095 Montpellier Cedex 5, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25164750" target="_blank"〉PubMed〈/a〉