3/10/20

ASTR 1040: & Galaxies Today on Stellar Explosions

• Revisit – spinning neutron stars with fierce magnetic fields; gradually slow down • Beamed pulses from synchrotron radiation • Crab (4 July 1054) in splendid detail with Hubble and Chandra • Spinning up pulsars through mass transfer from (surviving!) companions Ring • supernovae from mass transfer Nebula in binary system, but also repeated novae • Importance of WD supernovae as standard Prof. Juri Toomre TAs: Daniel Sega, Max Weiner candles Lecture 17 Tues 10 March 2020 zeus.colorado.edu/astr1040-toomre

REMINDER Things to do • Review 18.1 on mass transfer in binaries  with white dwarfs: supernovae = rotating • Re-read 18.3 on black holes with care neutron • Second Mid-Term Exam on Thur, review on Fierce magnetic fields Wed evening 6pm-8pm here (pink sheet, + sizzling electrons SYNCHROTRON Review Set #2) + fast rotation RADIATION   • HW #7 returned (with answers) à finest lighthouse cone beam • Observatory Night #6 tonight (signup) • Covid19 comments

REMINDER Synchrotron Synchrotron Radiation radiation • Fast electrons in beaming from strong magnetic REMINDER fields (spiralling) … and many forward beaming other energetic à neutron stars, places (quasars) black holes

• Different shape scream from electrons from thermal spiralling along magnetic radiation: emits at fields – like in particle all wavelengths, accelerators strongest in radio

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Back to famous friend !

SN: Crab Crab SNR Nebula M1 composite Oct 06: Spitzer (IR), 4 July 1054 Chandra (X), Hubble (V)

Crabs pulse patterns MODEL “NEUTRON STAR”

x-ray

visible

radio

REVISIT Listening Briefly revisit the web for to Pulsars pulsar “sound tracks” and • PSR 0329+54 typical, normal pulsar: period varying pulse patterns 0.714 sec (~1.40 rotations/sec) • PSR 0833-45 VELA pulsar: period 89 millisec (0.089 sec) (~11 rot/sec) in SNR ~10,000 yrs ago Jodrell Bank Observatory, UK • PSR 0531+21 CRAB pulsar: ~30 rot/sec youngest neutron star known • PSR J0437-4715 millisec pulsar, ~174 rot/sec • PSR 1937+21 2nd fastest pulsar, ~642 rot/sec surface of star moving at 1/7 c!

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Sam Lippincott Crib Sheet Awards Most Artful M-T Exam 1 13 Feb 2020 (10 Mar ceremony) Darkside Award

Emily Gradual slowing Lookhoff down of pulsar rotation Most Energy emitted Dense in pulses comes from rotational Info kinetic energy Award

Revisit Clicker Question MASS TRANSFER in evolving binary systems: Which of these stars formed EARLIEST important for white dwarfs and neutron stars (in the lifetime of the Universe)? Binary WD: Hot A. Star A: 70% H, 28% He, 2% other disks, novae, B. Star B: 75% H, 25% He, 0% other supernovae C. Star C: 72% H, 27% He, 1% other Neutron star: Radiation with D. Star D: 90% H, 10% He, 0% other more vigor, can spin up E. It depends on their masses MASS TRANSFER the star

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Neutron Stars in Binary Systems 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)

• Mass transfer builds very hot accretion disk around neutron star: à intense x-ray emission (continuosly) à transfer of angular can SPIN UP the NS

Black Widow millisecond pulsar – evaporating companion star in cocoon has spun it up Binary Systems: The Algol Paradox Sketch • Algol is a binary system consisting of a 3.7 solar mass main sequence star and a 0.8 solar mass red giant. Why is this strange? A. • A. A 3.7 star should have become a red giant before a 0.8 solar mass star • B. Binary stars usually have the same mass • C. 0.8 solar mass stars usually never become red giants Chandra X-ray Image

early MS Clicker Puzzle: Algol Binary System What happened? Binary Mass Exchange 1.5 • A. Binary stars can • The 0.8 solar mass star once 3.0 was more massive (3.0), with have different masses a 1.5 mass companion but usually ARE -2.2 formed at the same • As it became a red giant, it time. swelled and poured material onto its companion (lost 2.2) • More massive star should have had a • The red giant (0.8) is now less massive than its now 0.8 3.7 shorter main companion (3.7) sequence lifetime • Future: when the other star becomes red giant, it may pour gas back…?

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Stellar graveyard Stages in is very much alive ! mass exchange in binary system Mass transfer in binaries adds jazz… Here consider two massive stars white dwarfs, -- clock runs fast neutron stars or black holes 10-4 -- all can play !

40,000 ß Temperature 3,000

White Dwarfs in Binary Systems WD snooze … • Mass transfer àpyrotechnics from red giant companion (in three flavors) 1. spirals onto an accretion disk 1 or 2: 2. binary mass transfer • But too much à flash fusion on WD mass can take white dwarf over NOVA the edge!

• Accretion of gas onto Recurring Nova T Pyxidis ~ every 20 yrs white dwarf can lead to H fusion on surface • Star becomes much brighter à nova (may blow off shell) NOVA

Nova Cygni 1992+2

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SUPERNOVA Light Curves White Dwarf Bright Candles in Sky to Measure Distance SUPERNOVA

3: If exceed 1.4 MSUN

Collapse of WD, (Type II – core collapse) explosive fusion burning of  – all gone! (Type Ia -- WD) Brightest SN: superb beacons for measuring distances

Bright enough to be seen halfway across SUPERNOVAE in observable universe Other Galaxies • 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) Useful for mapping the • If monitor a million universe to the largest galaxies, likely to find 30+ new ones each night! distances

Supernovae in very distant galaxies White dwarf SN as distance estimators

• Standard explosion = fusion of 1.4 solar BEFORE masses of material

• Nearly the same amount of energy released

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White dwarf supernovae • Carbon fusion Practical difficulty: White dwarf SN explosion: mass transfer in binary brighter SN • Need to catch them takes white dwarf dim more slowly! within a day or two `over the edge of the explosion • Roughly same • About 1 per galaxy amount of energy per century released (calibrate) • Need to monitor thousands of galaxies to catch a few per year à galaxy clusters are calibrated useful

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