3/18/14. Today on Stellar Explosions. Second Mid-Term Exam. Things to do SECOND MID-TERM EXAM. Making a millisecond pulsars spin it up!

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1 3/18/14 ASTR 1040: Stars & Galaxies Binary mass transfer: accretion disk Today on Stellar Explosions Spinning up pulsars through mass transfer from (surviving!) companions White dwarf supernovae from mass transfer in binary system, but also repeated novae Mass transfer can also involve neutron stars (and black holes!) Famous supernova: SN1987A Importance of white-dwarf supernovae as standard candles Prof. Juri Toomre TA: Ryan Orvedahl Lecture 19 Tues 18 Mar 2014 zeus.colorado.edu/astr1040-toomre Things to do Second Mid-Term Exam Review 18.1 on mass transfer in binaries with white dwarfs: supernovae Read 18.3 on black holes with care Overview read Chap 19: `Our Galaxy New HW # 9 (involves supernovae energies), HW #8 due today SECOND MID-TERM EXAM Grade boundaries, based on 122 points (graded on a curve ): If 107/122 (88%) or over, A s [35%] 96/122 (79%) or over, B s [40%] 78/122 (64%) or over, C s [20%] Also +, plain, and within these ranges Making a millisecond pulsars spin it up! Mass transfer onto neutron star in binary system can spin up the pulsar even to 1000 times per second (ms) Accretion disk forms: extremely hot ( X-ray Burster if He fusion) Go through answer sheet and talk to us if do not understand our choices. Keep exam + answers for future review (comp final) 1

2 3/18/14 Black Widow millisecond pulsar evaporating companion star in cocoon has spun it up Sketch Chandra X-ray Image Reading ahead clicker: What happens in a white dwarf supernova? A. Carbon fuses throughout the white dwarf B. Hydrogen fuses on the surface of the white dwarf C. The white dwarf collapse into a neutron star D. Helium fuses throughout the white dwarf L 10 6 Stellar graveyard is very much alive! Mass transfer in binaries adds jazz white dwarfs, neutron stars or black holes -- all can play! 10-4 Stages in mass exchange in binary system Here consider two massive stars -- clock runs fast 40,000 ß Temperature 3,000 White Dwarfs in Binary Systems Mass transfer from red giant companion spirals onto an accretion disk But too much mass can take white dwarf over the edge! WD snooze à pyrotechnics (in three flavors) 1 or 2: binary mass transfer à flash fusion on WD NOVA

3 Recurring Nova T Pyxidis ~ every 20 yrs & Accretion of gas onto white dwarf can lead to H fusion on surface & Star becomes much brighter à nova (may blow off shell) NOVA Nova Cygni White Dwarf SUPERNOVA SUPERNOVA Light Curves Bright Candles in Sky to Measure Distance 3: If exceed 1.4 MSUN Collapse of WD, explosive fusion burning of carbon star all gone! Brightest SN: superb beacons for measuring distances SUPERNOVAE in Other Galaxies (Type II core collapse) (Type Ia -- WD) Bright enough to be seen halfway across observable universe & Bright enough to be seen as sudden, bright point in other galaxies & Many astronomers monitor nearby galaxies nightly to catch them & 1 per 100 years per galaxy means that if you monitor 100 galaxies, see ~ 1 SN per year) & If monitor a million galaxies, likely to find 30+ new ones each night! Useful for mapping the universe to the largest distances 3

4 Supernovae in very distant galaxies White dwarf SN as distance estimators & Standard explosion = fusion of 1.4 solar masses of material BEFORE & Nearly the same amount of energy released White dwarf supernovae & Carbon fusion explosion: mass transfer in binary takes white dwarf `over the edge & Roughly same amount of energy released (calibrate) Practical difficulty: White dwarf SN brighter SN dim more slowly! & Need to catch them within a day or two of the explosion & About 1 per galaxy per century calibrated & Need to monitor thousands of galaxies to catch a few per year à galaxy clusters are useful 24 Feb 1987: SN in LMC (160,000 ly away) Nearest: Story of SN 1987A in LMC Large Magellanic Cloud (LMC) (10,000 tiles with Spitzer composite IR) BEFORE blue supergiant AFTER (SN 1987A) 4

5 Mysterious triple rings in SN 1987A SN 1987A: Brightening knots 1994 > year birthday picture (Chandra + HST) Supernova SN 1987A SNR numbers game Cygnus Loop Cassiopeia A: SN in ~1680 (Flamsteed) Cass A: Viewed with Spitzer IR Youngest SNR in MW (Chandra X-ray image) synchrotron emission Neutron star at center 5

6 Kepler s SNR (1604) Kepler SNR (1604) Chandra X-ray Chandra X-ray image red: oxygen yellow: iron blue: shock prompt Type Ia SN Kepler s SNR (1604) SN in MW In Milky Way: Tycho Brahe SNR (1572) Chandra X-ray 20 ly across x-ray visible infrared Since white dwarfs in evolving binary systems come alive what about neutron stars? Neutron Stars in Binary Systems If white dwarfs can do it, so can neutron stars! Binary WD: Hot accretion disks, novae, supernovae MASS TRANSFER Neutron star: Radiation with more vigor, no SN & Mass transfer builds very hot accretion disk around neutron star: à intense x-ray emission (continuosly) à explosive helium burning (in bursts) on disk 6