Iax-type supernova

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Iax-type supernovae are a subgroup of thermonuclear supernovae. The thermonuclear supernovae of type Ia (SN Ia) arise when white dwarfs exceed the Chandrasekhar limit mass and the degenerative pressure cannot prevent their own gravity from collapsing. The collapse of white dwarfs consisting of carbon and oxygen causes an explosive burning of the carbon and the energy released in the process completely destroys the degenerated star. As supernovae type Iax Type Ia supernovae be referred to a lower luminosity reach the maximum, and a slower rate of expansion of the ejecta than the vast majority of the SN Ia. These properties are attributed to a lower mass of the predecessor star in the range of approximately 0.5 solar masses, while the Chandrasekhar limiting mass is approximately 1.44 solar masses . Like the Super-Chandrasekhar supernovae , the Type Iax are a subgroup of the SN Ia with very different properties. The term SN 2002cx-like supernovae is used as an alternative designation.

properties

Type Ia supernovae are the standard candles in astrophysics for cosmological distances. Because the Chandrasekhar limiting mass varies only slightly with the chemical composition of the white dwarf, an energy of 10 44 J (= 10 51 erg ) is released in all Type Ia supernovae , and this enabled the accelerated expansion of the Universe to be closed. When observing many SN Ia, a subgroup was found whose luminosity is below and whose observed rate of expansion is far below the normal SN Ia. Both phenomena are attributed to a lower mass of the predecessor star, since less 56 Ni is produced in the thermonuclear reactions during the detonation , which further decays to 56 Co and 56 Fe and is the main source for the luminosity of the supernova.

The absolute visual brightness at the maximum is in the range from M v −14.2 to −18.9. The spectroscopic properties largely correspond to those of SN Ia, although the maximum expansion speed is lower in a value range from 2000 to 8000 km / s in the presence of a hot photosphere . As with the normal SN Ia, there is a relationship between the shape of the light curve and the luminosity , this being shifted towards lower brightness levels compared to normal SN Ia and showing greater scattering. In contrast to normal SN Ia, the type Iax SN show no secondary maximum in the near infrared . The Type Iax precursor star is likely a white dwarf due to its position in late spiral galaxies , the low mass of the ejecta, strong iron lines in the spectrum, and signs of C / O burning in maximum light. The Type Iax supernovae are the most common subgroup of the SN Ia, with around 30 Type Iax for every 100 normal SN Ia.

Emergence

The observations are interpreted as a failed deflagration in a white dwarf, with only part of the available mass being converted during the thermonuclear burn. This interpretation is supported by late spectra of the SN Iax, which in contrast to normal supernovae of type Ia show forbidden lines of oxygen. A part of the white dwarf may even remain, while in normal SN Ia the precursor star is completely destroyed. Alternatively, Type Iax supernovae are interpreted as the result of a mass transfer of helium from a degenerate companion to a C / O white dwarf, with an explosive helium burning in the lowest layer of the helium atmosphere . This process is known as double detonation, where a shock wave from the explosive burning of helium runs into the core of the white dwarf and compresses it. Due to the compression, the C / O core ignites before the Chandrasekhar limit mass is reached, which explains a lower luminosity of the Iax type.

Examples

  • SN 1991bj
  • SN 2002bp,
  • SN 2002cx
  • SN 2003gq
  • SN 2004cs
  • SN 2004gw
  • SN 2005P
  • SN 2005cc
  • SN 2005hk
  • SN 2006hn
  • SN 2007J
  • SN 2007ie
  • SN 2007qd
  • SN 2008A
  • SN 2008ae
  • SN 2008ge
  • SN 2008ha
  • SN 2009J
  • SN 2009ku
  • SN 2010ae
  • SN 2010el
  • SN 2011ay
  • SN 2011ce
  • SN 2012Z

literature

  • Ryan J. Foley et al .: Type Iax Supernovae: A New Class of Stellar Explosion . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1212.2209v2 .
  • Bo Wang, Stephen Justham, Zhanwen Han: Double-detonation explosions as progenitors of type Iax supernovae . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1301.1047 .
  • Curtis McCully et al .: Hubble Space Telescope and Ground-Based Observations of the Type Iax Supernovae SN 2005hk and SN 2008A . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1309.4457v1 .