Calcium Rich Gap Transient

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Calcium-Rich Gap Transients are a sub-type of supernovae that develop photometrically and spectroscopically faster than any other sub-type of supernovae. Their maximum brightness lies between the classic novae and the supernovae. The main characteristic of Calcium-Rich Gap Transients, or sometimes Calcium-Rich Transients, is a high frequency of calcium in the first few weeks of their onset.

properties

In surveys such as the Palomar Transient Factory, more and more types of previously unknown eruptive variables such as the luminous red novae have been discovered since 2000 . Stars are assigned to the class of Calcium Rich Gap Transients, though

  • their maximum brightness lies in the luminosity gap between the classical novae and the supernovae
  • the spectral and photometric development is very rapid
  • the maximum expansion speed is typical for supernovae in the range of 10,000 km / s
  • the spectral course is similar to a type Ib supernova, but an at least one hundred times higher frequency of calcium can be detected in the first two weeks of the outbreak
  • the ejected matter is estimated to be no more than 0.3 solar masses and is therefore a factor of 3 below the otherwise smallest ejactam mass in supernovae of type Ia

The location of the stellar explosions of calcium rich gap transients is often far outside the home galaxy with distances of more than 30 kiloparsecs . In general, this subspecies of the supernovae can be assigned to an old stellar population , in contrast to the spectroscopically similar supernovae Ib, which arise from the core collapse of a young massive star. The calcium rich gap transients are rare with a frequency significantly less than ten percent than that of type Ia supernovae.

interpretation

A core collapse or pair instability as the cause of the stellar explosion are ruled out by the observed location of the eruptive stars. Also, no luminous predecessor star can be identified in deep images from the time before the explosion. Calcium-Rich Gap Transients are also found in or near dwarf galaxies that have not formed any new stars for billions of years.

Also because of the low mass ejected from the calcium rich gap transients, their precursors are suspected to be white dwarfs . However, they do not follow the Phillips relationship and the detection of helium in their spectra also excludes type Ia supernovae. Models have therefore been proposed according to which a white dwarf with a mass well below the Chandrasekhar limit explodes:

  • an Accretion Induced Collaps of rapidly rotating white dwarfs. This interpretation is contested because it should lead to a faster rate of expansion and photometric evolution in descent and descent.
  • A deflagration model in a white dwarf, on the other hand, would suggest traces of elements of the iron group in late spectra . However, these have not yet been proven.
  • An explosive burning of helium in a bowl around a white dwarf can reproduce the light curve and the spectral development well. However, the observed ejected mass is a problem with this model.
  • The destruction of a white dwarf by the tidal forces of a nearby neutron star or a black hole also leads to contradictions with observations.

Examples

  • Sn 2005E
  • SN 2005cz
  • SN 2007ke
  • SN 2010et
  • SN 2012hn

literature

  • JD Lyman, AJ Levan, RP Church, MB Davies, NR Tanvir: The progenitors of calcium-rich transients are not formed in situ . In: Astrophysics. Solar and Stellar Astrophysics . 2014, arxiv : 1408.1424v1 .
  • Mansi M. Kasliwal et al .: CALCIUM-RICH GAP TRANSIENTS IN THE REMOTE OUTSKIRTS OF GALAXIES . In: Astrophysics. Solar and Stellar Astrophysics . 2011, arxiv : 1111.6109v1 .
  • Hagai B. Perets, Carles Badenes, Iair Arcavi, Joshua D. Simon and Avishay Gal-yam: AN EMERGING CLASS OF BRIGHT, FAST-EVOLVING SUPERNOVAE WITH LOW-MASS EJECTA . In: Astrophysics. Solar and Stellar Astrophysics . 2010, arxiv : 1008.2754v1 .
  • HB Perets et al .: A faint type of supernova from a white dwarf with a helium-rich companion . In: Astrophysics. Solar and Stellar Astrophysics . 2009, arxiv : 0906.2003v2 .