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Photometry of Type Ia Supernovae: Search for the Second Parameter

Explore the fascinating world of Type Ia Supernovae, crucial for measuring cosmic distances. Discover the explosion mechanisms, distance indicators, and the research behind these stellar events. Delve into the energetics, causes, and implications for astronomy.

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Photometry of Type Ia Supernovae: Search for the Second Parameter

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  1. Photometry of Type Ia Supernovae: Search for the Second Parameter Date: May 15, 2009 Author: Kevin Perot Advisor: Dr. Baron

  2. Outline Remnant of Tycho’s Nova, a type Ia supernova observed by Tycho Brahe in 1572. • Motivation • Distance indicators • Background • Supernova types • Type Ia supernovae • Why they’re cool • Why they blow up • How they blow up • How we use them • My research • What I’ve been doing • My results

  3. Distance Indicators galaxy clusters nearby galaxies Milky Way nearby stars solar system Hubble’s Law type Ia supernovae radar parallax main-sequence fitting cepheids Tully-Fisher relation • Measuring distances in astronomy requires some creativity • Cosmic distance ladder: • Why do we care? • Cosmological parameters • Composition of early galaxies

  4. Supernova Types H He S Si Fe • Classified based on spectral lines • Type II: Strong H • Type Ia: Strong Si • Essentially no H • Type Ib: Strong He • Essentially no H or Si • Type Ic: Essentially no H, Si, or He Type Ia Type Ic Type Ib Type II

  5. Type Ia Supernovae: Distance Indicators I SN 1994D, discovered in the galaxy NGC 4526. This galaxy is in the Virgo cluster, about 60 million light years away. • What makes type Ia supernovae good distance indicators? • Very common • Average-mass progenitor • Very bright • Absolute magnitude: -19.3 • Outshines host galaxy • Very consistent • Peak magnitude variation: ~0.3 • Much of this can be corrected for

  6. Type Ia Supernovae: What Causes Them? • Accretion model • Two stars are in a binary system • First, the larger one evolves to a white dwarf • Then, the smaller one evolves to a red giant • Matter spills from red giant to white dwarf • When the dwarf reaches the Chandrasekhar limit (about 1.4 solar masses), it explodes • Collision model • Two white dwarfs merge • Less likely • May explain anomalously massive Supernovae White dwarf accreting matter from giant companion Merging white dwarfs emitting gravitational waves

  7. Type Ia Supernovae: Explosion Mechanism • Fusion reignites as mass approaches Chandrasekhar limit • Deflagration • Leaves some material unburned • Detonation • Not enough intermediate-mass material produced • Delayed Detonation • Begins as a subsonic deflagration, allowing the star to pre-expand • Deflagration turns into a detonation, burning the remaining material • Most of the C and O burned to 56Ni, with some S and Si Model of a type Ia supernova. The blue surface shows deflagration; the white surface shows detonation.

  8. Type Ia Supernovae: Energetics • All energy released during burning goes into kinetic energy • Unbinds the star • Depends primarily on C/O ratio • The light we see comes from decay of 56Ni • Primary product of burning • Amount of 56Ni primarily depends on central density • Decay heats up supernova remnant • Remnant initially opaque, but becomes transparent after a few days White Dwarf Kinetic Energy Star Unbound 56Ni Decay γ γ γ Light Emission γ

  9. Type Ia Supernovae: Distance Indicators II • Brightness varies slightly • Different amounts of 56Ni • Brightness related to decline rate • Brighter supernovae decline more slowly • Brighter supernovae are hotter, and thus more opaque • Stretch method • May be more variations we can account for

  10. My Project Light curves in blue and visible bands Brightness Time (days) • Learn to use IDL • Analyze supernova data to look for more parameters • Data from Carnegie Supernova Project (CSP) • Light curves from 17 supernovae • Very similar observing parameters

  11. Theoretical Model High-mass progenitor • Model by Peter Höflich • Variations in progenitor mass cause variations along the light curve • Specifically looking for the pattern of a high-mass progenitor • Most identifiable pattern

  12. Results • Several light curves fit this pattern • Evidence of a range of progenitor masses between 5 and 7 solar masses • Decline rate related to progenitor mass

  13. Questions? Artist’s conception of type Ia supernova before the explosion and 20 days after

  14. Image sources Outline http://upload.wikimedia.org/wikipedia/commons/a/ac/Main_tycho_remnant_full.jpg Supernova Types http://panisse.lbl.gov/~dnkasen/tutorial/graphics/sn_types.jpg Distance Indicators http://www.daviddarling.info/images/distance_ladder.jpg Type Ia Supernovae: Distance Indicators I http://www.cfa.harvard.edu/supernova//HighZ.html Type Ia Supernovae: What Causes Them? http://www.nscl.msu.edu/files/images/1301_800.preview.png http://images.astronet.ru/pubd/2005/06/02/0001206140/wd_cxc_c33.jpg Slideshow http://www.pha.jhu.edu/~bfalck/Iaprogenitor.jpg Type Ia Supernovae: Explosion Mechanism http://images.iop.org/objects/physicsweb/world/21/12/35/PWfea6_12-08.jpg Type Ia Supernovae: Distance Indicators II http://www.lbl.gov/Science-Articles/Archive/sabl/2005/October/stretch_correction.jpg Questions? http://www.sciencedaily.com/images/2007/07/070713234636-large.jpg

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