Editing SN 1987A (section)

==Light curve==
[[File:SN1987ALightCurve.png|thumb|left|A [[Photometric system#Photometric letters|visual band]] light curve for SN&nbsp;1987A. The inset plot shows the time around peak brightness. Plotted from data published by several sources.

<ref name="Allen1987">{{cite journal |last1=Allen |first1=W. H. |title=Three colour observations of SN1987A
 |journal=Royal Astronomical Society of New Zealand Publications of Variable Star Section
 |date=1987 |volume=14 |pages=82–84 |url=https://ui.adsabs.harvard.edu/abs/1988PVSS...14...82A
 |bibcode=1988PVSS...14...82A |access-date=7 November 2022}}</ref>

<ref name="Suntzeff1988">{{cite journal |last1=Suntzeff |first1=Nicholas B. |last2=Hamuy |first2=Mario
 |last3=Martin |first3=Gabriel |last4=Gomez |first4=Arturo |last5=Gonzalez |first5=Ricardo
 |title=SN 1987A in the LMC. II. Optical Photometry at Cerro Tololo |journal=Astronomical Journal
 |date=December 1988 |volume=96 |page=1864 |doi=10.1086/114933 |bibcode=1988AJ.....96.1864S
 |url=https://ui.adsabs.harvard.edu/abs/1988AJ.....96.1864S |access-date=7 November 2022}}</ref>

<ref name="Catchpole2987">{{cite journal |last1=Catchpole |first1=R. M. |last2=Menzies |first2=J. W.
 |last3=Monk |first3=A. S. |last4=Wargau |first4=W. F. |last5=Pollaco |first5=D. |last6=Carter |first6=B. S.
 |last7=Whitelock |first7=P. A. |last8=Marang |first8=F. |last9=Laney |first9=C. D.
 |last10=Balona |first10=L. A. |last11=Feast |first11=M. W. |last12=Lloyd Evans |first12=T. H. H.
 |last13=Sekiguchi |first13=K. |last14=Laing |first14=J. D. |last15=Kilkenny |first15=D. M.
 |last16=Spencer Jones |first16=J. |last17=Roberts |first17=G. |last18=Cousins |first18=A. W. J.
 |last19=van Vuuren |first19=G. |last20=Winkler |first20=H.
 |title=Spectroscopic and photometric observations of SN 1987A- II. Days 51 to134
 |journal=Monthly Notices of the Royal Astronomical Society |date=November 1987 |volume=229 |pages=15P–25P
 |doi=10.1093/mnras/229.1.15P |bibcode=1987MNRAS.229P..15C
 |url=https://academic.oup.com/mnras/article/229/1/15P/959331 |access-date=7 November 2022|doi-access=free }}</ref>

<ref name="Fransson2007">{{cite journal |last1=Fransson |first1=C. |last2=Gilmozzi |first2=R.
 |last3=Groeningsson |first3=P. |last4=Hanuschik |first4=R. |last5=Kjaer |first5=K. |last6=Leibundgut |first6=B.
 |last7=Spyromilio |first7=J. |title=Twenty Years of Supernova 1987A |journal=The Messenger |date=March 2007
 |volume=127 |page=44 |url=http://www.eso.org/sci/publications/messenger/archive/no.127-mar07/messenger-no127-44-48.pdf
 |access-date=8 November 2022 |bibcode=2007Msngr.127...44F}}</ref>
]]

Much of the [[light curve]], or graph of luminosity as a function of time, after the explosion of a [[type II supernova]] such as SN 1987A is produced by the energy from [[radioactive decay]]. Although the luminous emission consists of optical photons, it is the radioactive power absorbed that keeps the remnant hot enough to radiate light. Without the radioactive heat, it would dim quickly. The radioactive decay of [[isotopes of nickel|<sup>56</sup>Ni]] through its daughters [[isotopes of cobalt|<sup>56</sup>Co]] to [[isotopes of iron|<sup>56</sup>Fe]] produces gamma-ray [[photon]]s that are absorbed and dominate the heating and thus the luminosity of the ejecta at intermediate times (several weeks) to late times (several months).<ref name="explosion_model">
{{cite journal
 |last1=Kasen |first1=D.
 |last2=Woosley |first2=S.
 |year=2009
 |title=Type II Supernovae: Model Light Curves and Standard Candle Relationships
 |journal=[[The Astrophysical Journal]]
 |volume=703 |issue=2 |pages=2205–2216
 |arxiv=0910.1590
 |bibcode=2009ApJ...703.2205K
 |doi=10.1088/0004-637X/703/2/2205
 |s2cid=42058638
}}</ref> Energy for the peak of the light curve of SN1987A was provided by the decay of <sup>56</sup>Ni to <sup>56</sup>Co (half life of 6 days) while energy for the later light curve in particular fit very closely with the 77.3-day half-life of <sup>56</sup>Co decaying to <sup>56</sup>Fe. Later measurements by space gamma-ray telescopes of the small fraction of the <sup>56</sup>Co  and <sup>57</sup>Co gamma rays that escaped the SN1987A remnant without absorption<ref>
{{cite journal
 |last1=Matz |first1=S. M.
 |display-authors=etal
 |year=1988
 |title=Gamma-ray line emission from SN1987A
 |journal=[[Nature (journal)|Nature]]
 |volume=331 |issue=6155 |pages=416–418
 |bibcode=1988Natur.331..416M
 |doi=10.1038/331416a0
 |s2cid=4313713
}}</ref><ref>
{{cite journal
 |last1=Kurfess |first1=J. D.
 |display-authors=etal
 |year=1992
 |title=Oriented Scintillation Spectrometer Experiment observations of Co-57 in SN 1987A
 |journal=[[The Astrophysical Journal Letters]]
 |volume=399 |issue=2 |pages=L137–L140
 |bibcode=1992ApJ...399L.137K
 |doi=10.1086/186626
}}</ref> confirmed earlier predictions that those two radioactive nuclei were the power source.<ref>
{{cite journal
 |last1=Clayton |first1=D. D.
 |last2=Colgate |first2=S. A.
 |last3=Fishman |first3=G. J.
 |year=1969
 |title=Gamma-Ray Lines from Young Supernova Remnants
 |url=https://tigerprints.clemson.edu/cgi/viewcontent.cgi?article=1313&context=physastro_pubs
 |journal=[[The Astrophysical Journal]]
 |volume=155 |page=75
 |bibcode=1969ApJ...155...75C
 |doi=10.1086/149849
}}</ref>

Because the <sup>56</sup>Co in SN1987A has now completely decayed, it no longer supports the luminosity of the SN 1987A ejecta. That is currently powered by the radioactive decay of [[Isotopes of titanium|<sup>44</sup>Ti]], with a half life of about 60 years but which increases with its ionization state as the decay is purely through electron capture. With this change, X-rays produced by the ring interactions of the ejecta began to contribute significantly to the total light curve. This was noticed by the Hubble Space Telescope as a steady increase in luminosity 10,000 days after the event in the blue and red spectral bands.<ref name=McCray2016>
{{Cite journal
 |last1=McCray |first1=R.
 |last2=Fansson |first2=C.
 |title=The Remnant of Supernova 1987A
 |journal=[[Annual Review of Astronomy and Astrophysics]]
 |volume=54 |pages=19–52 |year=2016
 |bibcode=2016ARA&A..54...19M
 |doi=10.1146/annurev-astro-082615-105405
}}</ref> X-ray lines <sup>44</sup>Ti observed by the [[INTEGRAL]] space X-ray telescope showed that the total mass of radioactive <sup>44</sup>Ti synthesized during the explosion was {{nowrap|3.1 ± 0.8{{e|−4}} [[solar mass|{{solar mass}}]]}}.<ref name=Grebenev2012>
{{Cite journal
 |last1=Grebenev |first1=S. A.
 |last2=Lutovinov |first2=A. A.
 |last3=Tsygankov |first3=S. S.
 |last4=Winkler |first4=C.
 |year=2012
 |title=Hard-X-ray emission lines from the decay of 44Ti in the remnant of supernova 1987A
 |journal=[[Nature (journal)|Nature]]
 |volume=490 |issue=7420 |pages=373–375
 |arxiv=1211.2656
 |bibcode=2012Natur.490..373G
 |doi=10.1038/nature11473
 |pmid=23075986
 |s2cid=205230641
}}</ref>

Observations of the radioactive power from their decays in the 1987A light curve have measured accurate total masses of the <sup>56</sup>Ni, <sup>57</sup>Ni, and <sup>44</sup>Ti created in the explosion, which agree with the masses measured by gamma-ray line space telescopes and provides nucleosynthesis constraints on the computed supernova model.<ref name="20yrsof1987A">
{{cite journal
 |last1=Fransson |first1=C.
 |display-authors=etal
 |year=2007
 |title=Twenty Years of Supernova 1987A
 |journal=[[The Messenger (astronomy magazine)|The Messenger]]
 |volume=127 |page=44
 |bibcode=2007Msngr.127...44F
}}</ref>