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Supernovae Historically: “new stars” in sky Seen in 1006, 1054, 1181, 1572, 1604, 1680 SN 1054 visible in daytime sky for many months (Chinese records) SN 1572 – Tycho, SN 1604 – Kepler SN 1987A is the only SN visible to the naked eye since the development of telescopes. It is in the Large Magellanic Cloud (50 kpc distant)
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Tycho’s report on his observations of the SN of 1572
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Supernovae Historically: “new stars” in sky Seen in 1006, 1054, 1181, 1572, 1604, 1680 SN 1054 visible in daytime sky for many months (Chinese records) SN 1572 – Tycho, SN 1604 – Kepler SN 1987A is the only SN visible to the naked eye since the development of telescopes. It is in the Large Magellanic Cloud (50 kpc distant)
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Most of what we know today about SN comes from studying them in other galaxies.
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Why are SNe important? The source of most heavy (> He) in the universe. Input a lot of mechanical energy into the interstellar medium (10 51 erg). A laboratory for studying physics under extreme conditions. Associated with useful/interesting phenomena: neutron stars and pulsars; SN Ia used in cosmology; SN II associated with gamma ray bursts.
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Supernovae are energetic explosions Rapid rise (10 days) to peak luminosities of about 10 10 solar luminosities. Spectra show broad, blue-shifted absorption lines with velocities of about 10 4 km/s. Luminous stellar progenitor seen in a few cases.
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SNe Types Type Ia: no hydrogen in spectrum, brightest peak luminosity, seen only in both elliptical and spiral galaxies. Type Ib/Ic: no hydrogen in spectrum, fainter peak L, seen only in spiral galaxies. Type II: hydrogen seen in spectrum, fainter than Ia’s, seen only in spiral galaxies. Light curve (brightness vs time) comes in two broad types – linear (II L) and plateau (II P); though there is a wide diversity in this class.
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SN spectra at early times: broad absorption lines, some with PCygni profiles.
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SNe spectra at late times become dominated by emission lines (hot, low-density gas) of Fe/Co (Type Ia) or light and intermediate elements (Type II and Ib/c)
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SNe Types Type Ia: no hydrogen in spectrum, brightest peak luminosity, seen only in both elliptical and spiral galaxies. Type Ib/Ic: no hydrogen in spectrum, fainter peak L, seen only in spiral galaxies. Type II: hydrogen seen in spectrum, fainter than Ia’s, seen only in spiral galaxies. Light curve (brightness vs time) comes in two broad types – linear (II L) and plateau (II P); though there is a wide diversity in this class.
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Sne Light Curves
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Supernovae searches & rates Used to be found by dedicated amateurs, today mostly found by automated surveys (of nearby galaxies) and scheduled discovery campaigns (for distant galaxies). Type Ia: one every 300 years in the Milky Way Galaxy (a typical big galaxy). Type Ib/c, II: one every 30-50 years in the Milky Way.
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Berkeley Automated Telescopes KAIT: 0.76m automated telescope Images about 1000 galaxies a night out to a distance of about 200 Mpc Discovers about 80 SNe a year.
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SN 2008I
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SN Ia Phillips relation Peak brightness is related to the initial rate of decline of the light curve (faster decline goes with a fainter peak). More generally, the peak brightness correlates with the shape and color of the light curve. Reduces the scatter from 0.4 – 0.5 magnitude to 0.12 – 0.15 mag.
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