ASTR 1040 Accel Astro:
Astro: Stars & Galaxies
Prof. Juri Toomre TAs: Ben Brown, Adam Jensen
More Truly Bizarre Events
• How mass transfer from binary companion
can spinspin-up pulsar
• White dwarf supernovae from mass transfer
in binary system, but also repeated novae
• Hot accretion disks formed around object
(white dwarf, neutron star, black hole) on
receiving end of mass transfer
• Why more pulsars than supernova remnants
(SNR)
Lecture 18 Thur 16 Mar 06
zeus.colorado.edu/astr1040zeus.colorado.edu/astr1040-toomre
Clicker review – what is left behind?
Schedule of Events
• Second MidMid-Term Exam this Mon in
recitation, review session tonight 7pm+
(Review Set 2)
2) – cribcrib-sheet awards
• Homework Set 7 due today – new HW 8
passed out – discussion topic on gasgas-starsstarsgas posted, due Mon Apr 3 (post(post-SB)
• Overview read Chap 19 `Our Galaxy’
Galaxy’ for
next Tues lecture
• Read Chap S3 `Spacetime and Gravity’
Gravity’ for
further context about black holes
Final fate of
massive stars
Æ Neutron star
Æ Black hole
• After a massivemassive-star supernova explosion,
the remains of the stellar core _______ .
•
•
•
•
A.
B.
C.
D.
will always be a neutron star
B.
may be either neutron star or black hole
will always be a black hole
may be either a white dwarf, neutron star,
or black hole
Back to
famous
friend –
with
pulsar!
SN: Crab
Nebula M1
4 July 1054
1
REMINDER
Gradual slowing
down of
pulsar rotation
“Pulsar”
Pulsar”
= rotating
neutron star
Energy emitted
in pulses comes
from rotational
kinetic energy
Fierce magnetic fields
+ sizzling electrons
+ fast rotation
Æ finest “lighthouse”
lighthouse”
SYNCHROTRON
RADIATION
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:
forms:
extremely hot ( “X-ray
Burster”
Burster” if He fusion)
(Listen to pulsars
from our website)
“Black Widow”
Widow” millisecond pulsar –
evaporating companion star in cocoon has spun it up
Sketch
Chandra XX-ray Image
L
SNR
“numbers game”
game”
Cygnus
Loop
106
“Stellar graveyard”
graveyard”
is very much alive !
Mass transfer in
binaries adds jazz…
jazz…
white dwarfs,
neutron stars
or black holes
-- all can play !
10-4
40,000
Å Temperature
3,000
2
“Compact Companions”
Companions” in Binary Systems
• Mass transfer
from red giant
companion
spirals onto
accretion disk
Stages in
mass exchange
in binary system
Here consider
two massive stars
-- clock runs fast
• Inner parts
become VERY
hot -- glow in
UV, XX-rays
White Dwarfs in Binary Systems
Mass transfer
Æ accretion disk
• Again, mass
transfer from red
giant companion
spirals onto an
accretion disk
disk gets very hot
-- radiates brightly
makes neutron stars
and black holes visible!
• But too much
mass can take
white dwarf over
the edge!
Nova
WD snooze …
Æpyrotechnics
(in three flavors)
1.
1 or 2:
• Accretion of gas onto
white dwarf can lead to H
fusion on surface
• Star becomes much
brighter Æ nova (may
blow off shell)
2.
binary mass transfer
Æ flash fusion on WD
NOVA
Nova Cygni 1992+2
3
Recurring Nova T Pyxidis ~ every 20 yrs
White Dwarf
SUPERNOVA
3: If exceed 1.4 MSUN
Collapse of WD,
WD,
explosive fusion
burning of “carbon
star”
star” – all gone!
gone!
Brightest SN:
SN:
superb beacons
for measuring
distances
SUPERNOVA Light Curves
Bright Candles in Sky to Measure Distance
SUPERNOVAE in
Other Galaxies
• Bright enough to be seen
as sudden, bright point in
other galaxies
(Type II)
(Type I)
• 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!
Since white dwarfs in evolving binary systems
come “alive”
alive” – what about neutron stars ?
Neutron Stars in Binary Systems
If white dwarfs can do it, so can neutron stars!
Binary WD:
WD:
Hot accretion
disks, novae,
supernovae
Neutron star:
star:
Radiation with
more vigor,
no SN
MASS TRANSFER
• Mass transfer builds very hot accretion disk around
neutron star:
Æ intense xx-ray emission (continuosly
(continuosly))
Æ explosive helium burning (in bursts) on disk
4