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Photometry of Type Ia Supernovae: Search for the Second Parameter

Photometry of Type Ia Supernovae: Search for the Second Parameter. Date: May 15, 2009 Author: Kevin Perot Advisor: Dr. Baron. Outline. Remnant of Tycho’s Nova, a type Ia supernova observed by Tycho Brahe in 1572. Motivation Distance indicators Background Supernova types

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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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