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Double Line ~5c>?=5e?>=7h7i H q@=B7AA Single Line|5hA@HZqB@C7q TableFootnoteEGxR qCB7 9EGxR EPwEPw  TableFootnoteod5pDRRHH5xE5 HH GFe   HH5zFN5 HHlEE DHH5{G6 HH @>?HDoe   HH5}HJ6HHlGG HUV 5~I6 HUV AAJUU`   HUV 5JLH6HUV lII H$ 5K6 FtnH$ ELUU` tn oH$ 5LJ6H$ lKK HUV 5M5 HUV N UUe !  HUV 5NPF5HUV lMM H$ 5O5 H$ PUUe "  H$ 5PN5H$ lOO HH5QD HHAR  ` $ Types of Variable Stars UV;` %  X` & Stars with Varying Brightness u` '  F` (  Eclipsing Variables ` ) Binary star systems ` * o ` + 5 Pulsating Variables ` , Regular period variables #` - Cepheids (Type I and II) @` . RR Lyrae stars ]` / Long period variables z` 0 ̪ U` 1 UV Eruptive Variables F` 2 Novae ` 3  Supernovae ` 4   ` 5  Other Variables (` 6 T Tauri stars E` 7 Flare stars b` 8 UUMagnetic variables ` # N...  HH5RDHHlXQQ  d5SUU HH5TS arHHStars Uri ` > Supernovae ;` O inMuch more rare than novae. X` I emTwo very distinct types. u` S 5 ` K s Type I Supernovae: Re` Q bl Very complicated spectra hei` R No strong hydrogen lines r` P ! Elliptical and spiral galaxies ` M ت Gradual light curve #` L bl F@` T &  Model based on binary accretion ]` U 4 z` N 5Type II Supernovae: s ` W  Clear emission spectra ` X arStrong hydrogen emission lines c v` Y  Spiral galaxies only H` V 5Especially in spiral arms  ` Z  Sharp light curve (` \  E` [ &  Model based on core collapse of b` ] massive (young) stars ` _  HH5USts HHlXkTT ;d5V.XXve dHH5WV HHup` Q blYYXic ` 9 Novae ;` : en nX` ; P, Recurrent! Perhaps once every 100 years. ` < ad Complicated spectra ` = . Progenitor stars appear to be fast binaries  h ? .  Accretion onto  White Dwarf ? y` @ (After awhile, enough hydrogen picked up ` A 5c  Nova eruption es` B Y ` C s  Expanding gas shell apparent eci` D s 5+  Gas velocity  v R  from Doppler shift  ` E +  Measure angular  m d '` F f C  d = v R  (km/sec)  / 4.74 m  (arcsec/year) HD` H 5 a G s .Excellent determination of Absolute Magnitude ~@ G and Kinetic Energy VHH5XVveHHlRUWW H5YVlYZhW[^8/xu5Z[Y[e[^8/xu^88x 5[Z\YZ]e^88x ^8*Jl,.5\[^Y^] ^8l(wapp r ^88xs: ^8r*J.$|>7G'x;c-,:4n<^8:x^8lSu5]^_Y[_e ou^8lSu\^^89*Jl,.5^\]Y\]es^8=l(w Y ^8?s=Uf^[ ^8dwi/.$|` ;7GP;cJ[M:Cb <^8=^88vl 5_]`Y]`erhi^88vl ` E^8wvu5`_aY_ae^8wvu  ^8wv^8wv^8nvF5a`bY`e ^8nvF^8N^8N NearbyMƨn$5bacY Mƨn$M$M$  Star losingM+ƨr$5cbdY M+ƨr$M<M<  envelope toHMCƨz$5dceY YMCƨz$MTMT  white dwarf5[^8r5edfY8x[^8rZa [X5fegYgh J [X dZ dZ  Hot spots "ƨN/5gfhYfh  "ƨN/ 3+ 3+ build up^8 [X/`A5hgYu^8 [X/`Afgd6 i^8kksHH6 ji cHH]3 ^8]`Y]prk^8` J &Where does all that energy come from? -` `  #Best guess: Gravitational collapse 5J` ^  g f`` b ^88Consider a white dwarf with mass M 1.4  M SUN f`` c ƨ!Accrete some mass from companion lf`` d "  Exceeds Chandrasekhar limit f` h l Type I Supernova  H9f`` e !Assume M same before and after Vf` f`` f , R  Before  =  R  White Dwarf 5w f`` g 8, R  After  =  R  Neutron Star 53 ` h J 3  h i .Then the  total  energy released is 3 ` j h 83  k ؙ4This is  more than enough  to account for the 5U3 @ k uobserved  (visible) energy. dHH6 kikHHlUnjj  d6Hlnn^8HH6Iml aenHH: Gravitnse ` a Type II Supernovae 8Co;` m rf Core Collapse of a Massive Star X` n ƨ cu` p om Main Sequence phase ` q ceN1 H + 1 H + 1 H + 1 H    4 He in core ` r As e` s nd Post Main Sequence phase ,` t = B4 He + 4 He + 4 He    12 C in core ` u taO1 H + 1 H + 1 H + 1 H    4 He in shell ele#` v  @` w  Getting near the end mo]` x t+12 C + 4 He    16 O, ervz` y ne816 O + 4 He    20 Ne, ... in core ` z Lighter fusions in shell n` {  ` | " The Iron phase (i.e. the end) ` } /Fusion to  56 Ni (28 n and 28 p) in core  ` ~ +  No more energy available from fusion (`   Gravity takes over and so E` la4p  +  e -   n  + n +  energy b` in q` %Left with neutron star or black hole +HH6Knl cHHlkumm  Se݀ 6YopH Yh =M0>݀ /f` 'equal[(*q"Red"q*)minus[(*q"Red"q*)times[(*q"Red"q*)char[(*q"Red"q*)G],indexes[(*q"Red"q*)0,1,id[(*q"Red"q*)over[(*q"Red"q*)power[(*q"Red"q*)char[(*q"Red"q*)M],num[(*q"Red"q*)2.00000000,"2"]],char[(*q"Red"q*)R]]],string[(*q"Red"q*)"Before"]]]],plus[(*q"Red"q*)minus[(*q"Red"q*)times[(*q"Red"q*)char[(*q"Red"q*)G],indexes[(*q"Red"q*)0,1,id[(*q"Red"q*)over[(*q"Red"q*)power[(*q"Red"q*)char[(*q"Red"q*)M],num[(*q"Red"q*)2.00000000,"2"]],char[(*q"Red"q*)R]]],string[(*q"Red"q*)"After"]]]],string[(*q"Red"q*)"Energy"]]]2If`Z6Zpri moojfuon6lqreovajXk@$ '8approx[(*q"Magenta"q*)times[(*q"Magenta"q*)char[(*q"Magenta"q*)G],power[(*q"Magenta"q*)char[(*q"Magenta"q*)M],num[(*q"Magenta"q*)2.00000000,"2"]],id[(*q"Magenta"q*)plus[(*q"Magenta"q*)over[(*q"Magenta"q*)num[(*q"Magenta"q*)1.00000000,"1"],indexes[(*q"Magenta"q*)0,1,char[(*q"Magenta"q*)R],times[(*q"Magenta"q*)char[(*q"Magenta"q*)N],char[(*q"Magenta"q*)S]]]],minus[(*q"Magenta"q*)over[(*q"Magenta"q*)num[(*q"Magenta"q*)1.00000000,"1"],indexes[(*q"Magenta"q*)0,1,char[(*q"Magenta"q*)R],times[(*q"Magenta"q*)char[(*q"Magenta"q*)W],char[(*q"Magenta"q*)D]]]]]]]],over[(*q"Magenta"q*)times[(*q"Magenta"q*)char[(*q"Magenta"q*)G],power[(*q"Magenta"q*)char[(*q"Magenta"q*)M],num[(*q"Magenta"q*)2.00000000,"2"]]],indexes[(*q"Magenta"q*)0,1,char[(*q"Magenta"q*)R],times[(*q"Magenta"q*)char[(*q"Magenta"q*)N],char[(*q"Magenta"q*)S]]]]]*qN3 H6mrpiZqqjod6wsluujXkHH6xts x*qHHxMaa"q*)G],unt ` o ],Nucleosynthesis )2C ` [(in Type II Supernovae f` "M'Important factories for heavy elements 1"]` ta )` ta1Q:  Why are there elements heavier than iron? c` )S+(Note: Most elements are iron or lighter!) )nu` .0&A:  Neutron capture and Beta Decay ` *) t` *)Example (see Zeilik): 1` )D456 Fe  +  n   57 Fe followed by [(N` 457 Fe  +  n   58 Fe followed by tak` ]]458 Fe  +  n   59 Fe followed by me` ha459 Fe  +  n   60 Fe followed by 3 ` 460 Fe  +  n   61 Fe followed by ` 6w661 Fe   61 Co  +  e -  + n `  x x*Supernovae best for producing elements by @ 'rapid neutron capture (r-process). Nu6`  S` yp,(Asymptotic red giants contribute to slow t p` y .neutron capture reactions, i.e. s-process.) HH6zusvr HHlnxtt on d6veuxxy HH6wv xplHH> +  x7 ` Supernova SN 1987A e ;` Triumphs and Troubles X` ]] 8u`  February 24, 1987: ow` ,Supernova in the  Large Magellanic Cloud F`  ` - Spectrum and light curve    Type II ` 6w/ Distance known  (d LMC =52  kpc)  +#`  Not too near ... @` es+  Out of galactic plane ]` r-+  Enough time for radiations to disperse `  ... and not too far ` on)+  Follow light curve for a long time e€` ti,+  Images of leftovers  and precursor 6z߀` v ` %Major Bonus: Neutrino burst observed `   Neutron star formed! eu6` (However, no pulsar observed.) 6HH6xvHHlu{ww d7*y{{ubs HH7+zy FeHH0ova in t{ag ` Powering the Light Curve ;` nd*Hint: Is it  56 Fe or  56 Ni? X` ce ou -Fusion reactions in the core cease when they @ 1produce  56 Ni (equal numbers of p and n). `  u` io?However,  56 Fe is more stable than  56 Ni. So... `  l` aK56 Ni   56 Co  +  e +  + n +  gamma rays  6z#` v(t 1/2  = 6.1  days) @` rs b]` K56 Co   56 Fe  +  e +  + n +  gamma rays  lsaz` (t 1/2  = 77.1  days) `  ` -The  gamma rays  power the light curve ` 6  Observe the  half life  in the decay time `    ,(Also: Expected gamma ray spectrum observed (@ from the supernova.) oHH7-{ydHiHHlx~zz  od7<|hco~~HH7=}| rofHH` io~ 5 ` n SN 1987A: Problems ... ;` l X` 56, Around 100   fainter than expected +u` s- A blue supergiant exploded, not a red one! .`  ` These might be connected: ` + +Progenitor was star with low metal content z` (t!  Models need to be modified `  #` Th H ` ow... 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