SN 2011fe
SN 2011fe is a supernova of type Ia, which was discovered in August 2011 in M101. It is located at a distance of about 21 million light-years to Earth. It is so far discovered in the earliest stages of development Type Ia supernova.
Discovery
The stellar explosion was in the spacious, fully automated Palomar Transient Factory survey ( PTF) discovered on filming nights 24 August 2011 on 22 and 23 August and was initially the designation PTF 11kly. In their discovery the supernova had an apparent magnitude of 17.2 mag. On September 4, the apparent brightness was 10.3 may, probably close to the maximum. Upon discovering it was expected that the brightness to 6 mag could rise.
Importance
Type Ia supernovae arise when in a close binary system, a CO white dwarf matter from a companion star accretes until finally no longer sufficient to the degeneracy pressure of the electrons to stabilize the white dwarf, and this begins to collapse ( it exceeds the Chandrasekhar limit). As a result, there will be a runaway fusion process in the core and thus the supernova explosion. Since these processes always run at the Chandrasekhar mass is exceeded and thus the energy released ( and brightness) of supernovae should be the same type Ia, these are called " standard candles " used to determine the distance ( and also serve to calibrate other, more far-reaching methods of distance determination ). For use as standard candles, the discovery of the accelerated expansion of the universe is coming. The early discovery of the supernova event allows a closer examination of its course and the improvement of the models to describe them.
The progenitor star
The galaxy M101 at a distance of 21 million light years, has been well studied and, therefore, was sought on deep images after the precursor system. It is believed that there are two channels for the formation of supernovae of type Ia, in the single- degenerate channel accreted white dwarf matter from a red giant in a symbiotic star, a main sequence star in a cataclysmic binary star or a helium star. In the doubly - degenerate channel two white dwarfs come under emission of gravitational waves so close that one is torn apart by the tidal forces and its matter is accreted onto the more massive white dwarf.
On deep images of the Hubble Space Telescope no progenitor star was discovered at the site of a supernova. Since the location of the supernova is located outside of the spiral arms, the absorbance should be low. This symbiotic stars and helium stars can be excluded as a mass -giving precursor systems. Does the ejected at high velocity matter of the supernova circumstellar matter, this should lead to the development of radio and X-rays. Both could not be detected and thus can all precursor systems are excluded from the single- degenerate channel. Also in the UV could not be detected an interaction of the supernova with a companion star. The companion of the white dwarf is therefore either a main sequence star with less than one solar mass or also a white dwarf. A main sequence star would take in a close binary system in a supernova explosion about 1047 erg of energy and lose some of its atmosphere. To compensate for the loss of which would expand and show for a period of several thousand years, a luminosity of a few hundred to a thousand times the sun the star. This can also be a main sequence star as a companion of the exploding white dwarf at SN 2011fe be excluded. Depth of X-rays from the period before the outbreak can also be the place where the supernova detect any source and also close the doubly - degenerate channel, as a supersoft X -ray source within the detection limits should be. All the recognized precursor scenarios can be excluded for SN2011fe with high probability. It would be conceivable a rapidly rotating single white dwarf whose mass has already exceeded the Chandrasekharsche mass limit by accretion. A collapse is due to the rapid rotation prevented by centrifugal forces. Only when the white dwarf after a long period of time loses its stability by magnetic torque losses or emission of gravitational waves, there is a supernova of type Ia. Thus, before the explosion, neither X-rays would still detectable interaction would take place with circumstellar material.