Type Ib supernova

Types Ib and Ic supernovae are categories of stellar explosions that are caused by the core collapse of massive stars. These stars have shed (or been stripped of) their outer envelope of hydrogen, and, when compared to the spectrum of Type Ia supernovae, they lack the absorption line of silicon. Compared to Type Ib, Type Ic supernovae are hypothesized to have lost more of their initial envelope, including most of their helium. The two types are usually referred to as stripped core-collapse supernovae.

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. A supernova is first categorized as either a Type I or Type II, then sub-categorized based on more specific traits. Supernovae belonging to the general category Type I lack hydrogen lines in their spectra; in contrast to Type II supernovae which do display lines of hydrogen. The Type I category is sub-divided into Type Ia, Type Ib and Type Ic supernovae.

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. As Type Ib/Ic supernovae age, they also display lines from elements such as oxygen, calcium and magnesium. In contrast, Type Ia spectra become dominated by lines of iron. Type Ic supernovae are distinguished from Type Ib in that the former also lack lines of helium at 587.6 nm.

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