European Astronomical Society | 2020 Jun 29
An international group of researchers observed a source of variable gamma rays identified in 2010 by the NASA satellite Fermi. They used a technique called VLBI, that combines data from several radio telescopes on Earth, to produce the sharpest images to date. Surprisingly, the source of gamma rays was a symbiotic nova, a peculiar stellar system known to astronomers as V407 Cyg. ...
Stellar systems like V407 Cygni were not known to emit very high energy radiation, therefore with the observations in 2010, Fermi identified the first member of a new class of gamma objects. The astronomers now released the results of their VLBI campaign carried out during the spectacular outburst that produced the gamma rays. The images, compiled using the radio waves detected by telescopes in Europe and in the US, are the most detailed to date. They reveal the aftermath of a powerful cosmic explosion due to the interaction of two stars on close orbit.
Symbiotic novae are rare and exceptional objects, couples of stars composed of two very different companions: a small, dense, white dwarf and a pulsating red giant. The red giant emits a wind of material that is accumulated on the surface of the white dwarf and, when it reaches a critical density, gives rise to a very bright explosion.
While symbiotic novae are rare objects themselves, observing a symbiotic nova like V407 Cygni in gamma rays was an absolute breakthrough. The researchers went then in search of evidence indicating the presence of shocks, passing through the material in the form of shock waves, due to the very energetic physical processes involved in the event. Never before so detailed radio-band images reveal the shock produced by the explosion of the material on the surface of the white dwarf as it expands into the atmosphere of the red giant companion. ...
Very Long Baseline Interferometry Imaging of the Advancing Ejecta
in the First Gamma-Ray Nova V407 Cyg ~ Marcello Giroletti et al
- Astronomy & Astrophysics 638:A130 (June 2020) DOI: 10.1051/0004-6361/202038142
- arXiv.org > astro-ph > arXiv:2005.06473 > 13 May 2020