{{Short description|Types of supernovae caused by a star collapsing}} [[Image:Supernova 2008D.jpg|thumb|right|280px|The Type Ib supernova SN 2008D<ref> {{cite journal | last=Malesani |first=D. |display-authors=etal | date=2008 | title=Early spectroscopic identification of SN 2008D | bibcode=2009ApJ...692L..84M | journal=Astrophysical Journal | doi=10.1088/0004-637X/692/2/L84 | volume=692 | issue=2 | pages=L84–L87 | arxiv=0805.1188 |s2cid=1435322 }}</ref><ref> {{cite journal | last=Soderberg |first=A. M. |author-link=Alicia M. Soderberg |display-authors=etal | date=2008 | title=An extremely luminous X-ray outburst at the birth of a supernova | journal=[[Nature (journal)|Nature]] | volume=453 | pages=469–474 | doi= 10.1038/nature06997 | arxiv=0802.1712 | pmid=18497815 | issue=7194 |bibcode = 2008Natur.453..469S |s2cid=453215 }}</ref> in galaxy [[NGC 2770]], shown in [[X-ray]] (left) and visible light (right), at the corresponding positions of the images. ([[NASA]] image.)<ref> {{cite web | last=Naeye | first=R. |author2=Gutro, R. | date=21 May 2008 | url=http://www.nasa.gov/centers/goddard/news/topstory/2008/swift_supernova.html | title=NASA's Swift Satellite Catches First Supernova in the Act of Exploding | publisher=[[NASA]]/[[Goddard Space Flight Center|GSFC]] | access-date=2008-05-22 }}</ref>]]
'''Type Ib and Type Ic supernovae''' are categories of [[supernova]]e that are caused by the [[stellar core]] [[Gravitational collapse|collapse]] of [[massive star]]s. These stars have shed or been stripped of their outer envelope of [[hydrogen]], and, when compared to the spectrum of [[Type Ia supernova]]e, 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.
==Spectra==
When a [[supernova]] is observed, it can be categorized in the [[Rudolph Minkowski|Minkowski]]–[[Fritz Zwicky|Zwicky]] supernova classification scheme based upon the [[absorption line]]s that appear in its [[stellar spectrum|spectrum]].<ref> {{cite journal | first=L. A. L. | last=da Silva | date=1993 | title=The Classification of Supernovae | journal=[[Astrophysics and Space Science]] | volume=202 | issue=2 | pages=215–236 | doi=10.1007/BF00626878 | bibcode=1993Ap&SS.202..215D | s2cid=122727067 }}</ref> A supernova is first categorized as either a Type I or [[Type II supernova|Type II]], then subcategorized 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 subdivided into Type Ia, Type Ib and Type Ic.<ref name="taxonomy"> {{cite web |last = Montes |first = M. |date = 12 February 2002 |title = Supernova Taxonomy |url = http://rsd-www.nrl.navy.mil/7212/montes/snetax.html |publisher = [[Naval Research Laboratory]] |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 }}</ref>
Type Ib/Ic supernovae are distinguished from [[Type Ia supernova|Type Ia]] by the lack of an [[absorption line]] of singly ionized [[silicon]] at a [[wavelength]] of 635.5 [[nanometre]]s.<ref name=arxiv> {{cite journal |last=Filippenko |first=A.V. |date=2004 |title=Supernovae and Their Massive Star Progenitors |journal=The Fate of the Most Massive Stars |volume=332 |pages=34 |arxiv=astro-ph/0412029|bibcode=2005ASPC..332...33F }}</ref> As Type Ib and 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]].<ref name="SAO"> {{cite encyclopedia | url = http://cosmos.swin.edu.au/entries/typeibsupernovaspectra/typeibsupernovaspectra.html?e=1 | title = Type Ib Supernova Spectra | publisher = [[Swinburne University of Technology]] | encyclopedia=COSMOS – The SAO Encyclopedia of Astronomy | access-date = 2010-05-05 }}</ref> Type Ic supernovae are distinguished from Type Ib in that the former also lack lines of [[helium]] at 587.6 nm.<ref name="SAO" />
==Formation== [[File:Evolved star fusion shells.svg|right|thumb|240px|The onion-like layers of an evolved, massive star (not to scale).]] 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<sup>−5</sup> [[solar mass]]es ({{Solar mass|link=y}}) each year—the equivalent of {{Solar mass|1}} every 100,000 years.<ref> {{cite journal |last1=Dray |first1=L. M. |last2=Tout |first2=C. A. |last3=Karaks |first3=A. I. |last4=Lattanzio |first4=J. C. |date=2003 |title=Chemical enrichment by Wolf-Rayet and asymptotic giant branch stars |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=338 |pages=973–989 |doi=10.1046/j.1365-8711.2003.06142.x |bibcode=2003MNRAS.338..973D |issue=4 |doi-access=free }}</ref> [[File:Supernovae_as_initial_mass-metallicity.svg|thumb|Supernovae vs initial mass and metallicity]] 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.<ref name="arxiv" /> The progenitors of Types Ib and Ic have lost most of their outer envelopes due to strong [[stellar wind]]s or else from interaction with a close companion.<ref> {{cite conference |last=Pols |first=O. |date=26 October – 1 November 1995 |title=Close Binary Progenitors of Type Ib/Ic and IIb/II-L Supernovae |book-title=Proceedings of the Third Pacific Rim Conference on Recent Development on Binary Star Research |pages=153–158 |location=Chiang Mai, Thailand |bibcode=1997ASPC..130..153P }}</ref><ref name="woosley95"> {{cite conference |last1=Woosley |first1=S. E. |last2=Eastman |first2=R.G. |date=June 20–30, 1995 |title=Type Ib and Ic Supernovae: Models and Spectra |book-title=Proceedings of the NATO Advanced Study Institute |pages=821–838 |publisher=[[Kluwer Academic Publishers]] |location=Begur, Girona, Spain |bibcode=1997ASIC..486..821W |doi = 10.1007/978-94-011-5710-0_51 |isbn=978-94-010-6408-8 }}</ref> Rapid mass loss can occur in the case of a [[Wolf–Rayet star]], and these massive objects show a spectrum that is lacking in hydrogen. Type Ib progenitors have ejected most of the hydrogen in their outer atmospheres, while Type Ic progenitors have lost both the hydrogen and helium shells; in other words, Type Ic have lost more of their envelope (i.e., much of the helium layer) than the progenitors of Type Ib.<ref name="arxiv" /> In other respects, however, the underlying mechanism behind Type Ib and Ic supernovae is similar to that of a Type II supernova, thus placing Types Ib and Ic between Type Ia and Type II.<ref name="arxiv" /> Because of their similarity, Type Ib and Ic supernovae are sometimes collectively called Type Ibc supernovae.<ref> {{cite journal |last=Williams |first=A. J. |title=Initial Statistics from the Perth Automated Supernova Search |journal=[[Publications of the Astronomical Society of Australia]] |volume=14 |issue=2 |pages=208–213 |doi= 10.1071/AS97208 |bibcode=1997PASA...14..208W |year=1997 |doi-access=free }}</ref>
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.<ref> {{cite journal |last=Ryder |first=S. D. |display-authors=etal |date=2004 |title=Modulations in the radio light curve of the Type IIb supernova 2001ig: evidence for a Wolf-Rayet binary progenitor? |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=349 |issue=3 |pages=1093–1100 |doi=10.1111/j.1365-2966.2004.07589.x |doi-access=free |bibcode=2004MNRAS.349.1093R |arxiv = astro-ph/0401135 |s2cid=18132819 }}</ref> In any case, astronomers believe that most Type Ib, and probably Type Ic as well, result from core collapse in stripped, massive stars, rather than from the thermonuclear runaway of [[white dwarf]]s.<ref name=arxiv/>
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.<ref> {{cite web |last1=Sadler |first1=E. M. |last2=Campbell |first2=D. |date=1997 |title=A first estimate of the radio supernova rate |url=http://www.atnf.csiro.au/pasa/14_2/sadler/paper/node4.html |publisher=[[Astronomical Society of Australia]] |access-date=2007-02-08 }}</ref> They normally occur in regions of new star formation, and are extremely rare in [[elliptical galaxy|elliptical galaxies]].<ref name=perets>{{cite journal|doi=10.1038/nature09056|pmid=20485429|title=A faint type of supernova from a white dwarf with a helium-rich companion|journal=Nature|volume=465|issue=7296|pages=322–325|year=2010|last1=Perets|first1=H. B.|last2=Gal-Yam|first2=A.|last3=Mazzali|first3=P. A.|last4=Arnett|first4=D.|last5=Kagan|first5=D.|last6=Filippenko|first6=A. V.|last7=Li|first7=W.|last8=Arcavi|first8=I.|last9=Cenko|first9=S. B.|last10=Fox|first10=D. B.|last11=Leonard|first11=D. C.|last12=Moon|first12=D.-S.|last13=Sand|first13=D. J.|last14=Soderberg|first14=A. M.|last15=Anderson|first15=J. P.|last16=James|first16=P. A.|last17=Foley|first17=R. J.|last18=Ganeshalingam|first18=M.|last19=Ofek|first19=E. O.|last20=Bildsten|first20=L.|last21=Nelemans|first21=G.|last22=Shen|first22=K. J.|last23=Weinberg|first23=N. N.|last24=Metzger|first24=B. D.|last25=Piro|first25=A. L.|last26=Quataert|first26=E.|last27=Kiewe|first27=M.|last28=Poznanski|first28=D.|bibcode=2010Natur.465..322P|arxiv=0906.2003|s2cid=4368207}}</ref> Because they share a similar operating mechanism, Type Ibc and the various Type II supernovae are collectively called core-collapse supernovae. In particular, Type Ibc may be referred to as ''stripped core-collapse supernovae''.<ref name=arxiv/>
==Light curves== The [[light curve]]s (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.<ref> {{cite journal |last=Tsvetkov |first=D. Yu. |date=1987 |title=Light curves of type Ib supernova: SN 1984l in NGC 991 |journal=[[Soviet Astronomy Letters]] |volume=13 |pages=376–378 |bibcode=1987SvAL...13..376T }}</ref> Type Ib supernovae usually have slower decline rates for the spectral curves than Ic.<ref name=arxiv/>
Type Ia supernovae light curves are useful for measuring distances on a cosmological scale. That is, they serve as [[standard candle]]s. 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.<ref> {{cite journal |last=Homeier |first=N. L. |date=2005 |title=The Effect of Type Ibc Contamination in Cosmological Supernova Samples |journal=[[The Astrophysical Journal]] |volume=620 |issue=1 |pages=12–20 |doi=10.1086/427060 |bibcode=2005ApJ...620...12H |arxiv = astro-ph/0410593 |s2cid=18855749 }}</ref>
==See also==
* [[Type Ia supernova]] * [[Type II supernova]]
==References== {{Reflist|30em}}
==External links==
{{Supernovae}}
{{good article}}
[[Category:Supernovae|Type 1b and 1c Supernova]]