Super Chandrasekhar supernova of type Ia

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The super Chandrasekhar supernovae of type Ia are a subgroup of the supernovae of type Ia with a share of about nine percent of all Ia supernovae . In comparison, their absolute brightnesses are brighter by a maximum of one magnitude. They have a slower rate of ejecta expansion than the vast majority of SN Ia. These properties are attributed to a higher mass of the predecessor star in the range of 2.1 to 2.8 solar masses , while the Chandrasekhar limiting mass of a white dwarf is around 1.44 solar masses. As an alternative term for super-Chandrasekhar supernovae, the term superluminous supernovae of type Ia is used.

properties

Type Ia supernovae are the standard glowing 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 51 ergs is released in all Type Ia supernovae, and this made it possible to deduce the accelerated expansion of the universe with the help of these eruptions . During the observation of many supernovae of type Ia, a subgroup was found whose luminosity is above and whose observed expansion speed is far below the normal Ia SN. Both phenomena are attributed to a higher mass of the predecessor star, since more 56 Ni is formed in the thermonuclear reaction during the detonation , which further decays to 56 Co and 56 Fe and is the main source for the luminosity of the supernova. Furthermore, the higher mass of the precursor star is likely to slow down the expansion of the ejecta more strongly due to stronger gravitational forces.

The absolute visual brightness is in the range of M v −19.5 to −20.5. In the spectrum of the Super-Chandrasekhar Supernova, the line of simply ionized carbon often shows up , which is not observed in normal Type Ia SN. The expansion speed of the singly ionized silicon remains constant for weeks before and after the maximum at a speed of 9000 km / s, which corresponds to only about 50 percent of the value of other SN Ia. This speed curve is interpreted as the result of a shock wave that runs through circumstellar material, such as can arise when two white dwarfs merge. There are no signs in the spectrum of a strong interaction with a dense circumstellar medium around the supernova, which provides the additional luminosity by converting kinetic energy into electromagnetic radiation. The mass of the ejecta derived from the spectra is more than two solar masses.

The position of the super Chandrasekhar supernovae is in the halo of their home galaxies or in less developed dwarf galaxies . In their vicinity there are very metal-poor stars with a metallicity of about a tenth that of the sun. The low metal content is probably also responsible for the higher luminosity of these eruptive variables .

Emergence

  • In the doubly degenerate scenario for supernova of type Ia, two white dwarfs can merge and collide due to the radiation of gravitational radiation . During the collision enough heat is released to ignite the thermonuclear runaway and because two white dwarfs are involved, a mass of up to twice the Chandrasekhar limit mass can be achieved
  • Through the accretion of a second white dwarf, a rapidly rotating white dwarf can arise, which rotates differentially and can clearly exceed the Chandrasekhar limit via centrifugal forces . Upper limit masses of up to 2.4 solar masses are possible before the accreting white dwarf explodes in a thermonuclear supernova
  • In an alternative scenario, a white dwarf and a run through red giant a common envelope . The white dwarf dives into the vast atmosphere of the giant star and throws it off. The hot core accretes material from the white dwarf and is accelerated to high speeds, which delays the detonation because the centrifugal forces compensate for the gravitational forces. The rotation of the magnetic white dwarf leads to the emission of electromagnetic radiation and after a few billion years the superheavy degenerate star explodes
  • An asymmetrical detonation of the white dwarf can simulate an above or below average luminosity depending on the viewing angle due to an aspherical radiation. However, this hypothesis is not polarimetric observations support

Examples

  • SN 2006gz
  • SN 2007if
  • SN 2009dc
  • SN 2003fg

Individual evidence

  1. ↑ Upasana Das, Banibrata Mukhopadhyay: New mass limit for white dwarfs: super-Chandrasekhar type Ia supernova as a new standard candle . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1301.5965 .
  2. ↑ Stephan Hachinger et al .: Spectral modeling of the “Super-Chandra” Type Ia SN 2009dc - testing a 2 sun mass white dwarf explosion model and alternatives . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1209.1339 .
  3. ↑ R. SCALZO et al .: A SEARCH FOR NEW CANDIDATE SUPER-CHANDRASEKHAR-MASS TYPE Ia supernovae IN THE NEARBY SUPERNOVA FACTORY DATASET . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1207.2695 .
  4. ^ S. Taubenberger et al .: High luminosity, slow ejecta and persistent carbon lines: SN 2009dc challenges thermonuclear explosion scenarios. In: Astrophysics. Solar and Stellar Astrophysics . 2010, arxiv : 1011.5665 .
  5. ^ Rubab Khan, KZ Stanek, R. Stoll, JL Prieto: Super-Chandrasekhar SNe Ia Strongly Prefer Metal-Poor Environments . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1106.3071 .
  6. ↑ Yasuomi Kamiya et al .: SUPER-CHANDRASEKHAR-MASS LIGHT CURVE MODELS FOR THE HIGHLY LUMINOUS TYPE Ia SUPERNOVA 2009dc . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1207.4648 .
  7. ↑ IZUMI HACHISU et al .: A SINGLE DEGENERATE PROGENITOR MODEL FOR TYPE Ia SUPERNOVAE HIGHLY EXCEEDING THE CHANDRASEKHAR MASS LIMIT . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1106.3510 .
  8. ↑ Marjan Ilkov and Noam Soker: TYPE IA SUPERNOVAE FROM VERY LONG DELAYED EXPLOSION OF CORE-WD MERGER . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1106.2027 .
  9. ↑ Masaomi Tanaka et al .: SPECTROPOLARIMETRY OF EXTREMELY LUMINOUS TYPE Ia SUPERNOVA 2009dc: NEARLY SPHERICAL EXPLOSION OF SUPER-CHANDRASEKHAR MASS WHITE DWARF . In: Astrophysics. Solar and Stellar Astrophysics . 2009, arxiv : 0908.2057 .