Type Ib and Ic supernovae

Spectra

When a supernova is observed, it can be categorized in the Minkowski–Zwicky supernova classification scheme based upon the absorption lines that appear in its spectrum. |access-date = 2006-11-09 |url-status = dead |archive-url = https://web.archive.org/web/20061018024317/http://rsd-www.nrl.navy.mil/7212/montes/snetax.html |archive-date = 18 October 2006

Type Ib/Ic supernovae are distinguished from Type Ia by the lack of an absorption line of singly ionized silicon at a wavelength of 635.5 nanometres. | access-date = 2010-05-05

Formation

Prior to becoming a supernova, an evolved massive star resembles an onion in that it contains many layers of different elements, each undergoing fusion. The outermost layer consists of hydrogen, followed by helium, carbon, oxygen, and so forth. Thus when the outer envelope of hydrogen is shed, this exposes the next layer that consists primarily of helium (mixed with other elements). This can occur when a very hot, massive star reaches a point in its evolution when significant mass loss is occurring from its stellar wind. Highly massive stars (with 25 or more times the mass of the Sun) can lose up to 10−5 solar masses () each year—the equivalent of every 100,000 years. |doi-access=free

Type Ib and Ic supernovae are hypothesized to have been produced by core collapse of massive stars that have lost their outer layer of hydrogen and helium, either via winds or mass transfer to a companion. The progenitors of Types Ib and Ic have lost most of their outer envelopes due to strong stellar winds or else from interaction with a close companion of about . |book-title=Proceedings of the Third Pacific Rim Conference on Recent Development on Binary Star Research |book-title=Proceedings of the NATO Advanced Study Institute |doi-access=free

There is some evidence that a small fraction of the Type Ic supernovae may be the progenitors of gamma ray bursts (GRBs); in particular, type Ic supernovae that have broad spectral lines corresponding to high-velocity outflows are thought to be strongly associated with GRBs. However, it is also hypothesized that any hydrogen-stripped Type Ib or Ic supernova could be a GRB, dependent upon the geometry of the explosion. |display-authors=etal |doi-access=free

As they are formed from rare, very massive stars, the rate of Type Ib and Ic supernova occurrence is much lower than the corresponding rate for Type II supernovae. |access-date=2007-02-08

Light curves

The light curves (a plot of luminosity versus time) of Type Ib supernovae vary in form, but in some cases can be nearly identical to those of Type Ia supernovae. However, Type Ib light curves may peak at lower luminosity and may be redder. In the infrared portion of the spectrum, the light curve of a Type Ib supernova is similar to a Type II-L light curve.

Type Ia supernovae light curves are useful for measuring distances on a cosmological scale. That is, they serve as standard candles. However, due to the similarity of the spectra of Type Ib and Ic supernovae, the latter can form a source of contamination of supernova surveys and must be carefully removed from the observed samples before making distance estimates.

References

References

1. (2010). "A faint type of supernova from a white dwarf with a helium-rich companion". Nature.