Compact Binaries - 2ASTR2110

Sarazin

Test #2 Monday, November 13, 11 - 11:50 am Ruffner G006 (classroom) Bring pencils, paper, calculator You may not consult the text, your notes,

or any other materials or any person You may bring a 3x5 card with equations ~2/3 Quantitative Problems (like

homework problems) ~1/3 Qualitative Questions

Multiple Choice, Short Answer, Fill In the Blank questions No essay questions

Test #1 (Cont.) Equation/Formula Card: You may bring one 3x5 inch index card with

equations and formulae written on both sides. DO NOT LIST pc, AU, M¤, L¤, R¤

DO NOT INCLUDE ANY QUALITATIVE MATERIAL (text, etc.)

Test #2 (Cont.) Material:

Chapters 5, 7, 13.5-13.7, 14, 15, 17, 18, 23.3 Binary Stars, the Sun, Atomic Physics, Stellar

Spectra and Atmospheres, Stellar Interiors, Nuclear Energy, Stellar Evolution, Stellar Remnants, General Relativity, Black Holes, Stellar Deaths, Neutron Stars and Pulsars

(Quantitative problems only) (Qualitative problems only) Homeworks 6-9

Know pc, AU, M¤, L¤, R¤

Test #2 (Cont.)

No problem set week of November 6 – 13 to allow study for test

Review Session: Discussion session Friday, November 10, 3-4 pm

Compact Binaries - 2ASTR2110

Sarazin

Energy from Accretion •  Nuclear energy

•  Enuc ≈ 0.008 mc2 •  Requires surface for material to accumulate → Enuc = 0 for BHs

•  Gravitational energy •  Egrav ≈ (1/2) GMm/R = (1/4) (RS/R) mc2 (Virial Theorem) •  Egrav > Enuc if R ≲ 30 RS

•  Egrav > Enuc for BHs, NSs (and Enuc = 0 for BHs) •  Enuc > Egrav for WDs

•  BHs, NSs: Egrav ≈ 0.1 - 0.3 mc2 !!

Accretion Disks •  Accreted material has angular momentum

•  Binary orbit •  Other motions

•  Moves in, orbits faster, centrifugal force increases, forms disk

Accretion Disks Lgrav = d Egrav / dt = (G M* / 2 R*) Ṁ

Ṁ ≡ d M* / dt accretion rate

Lgrav ≈ 1041 (M*/M�)(Ṁ/ M�/yr)(R*/R�)-1 erg/s

Typically,

Ṁ ~ 0.1 M� / tKelvin ~ 10-1 M� / 107 yr ~ 10-8 M�/yr

Accretion Disks Disk dense, ~ blackbody

Lgrav ≈ A σ T4

A ≈ 2 π R2

T ≈ (L/ 2 π σ R2)1/4

2 sides of disk

Zoology of Binary Stars

Zoology of Binary Stars

Cataclysmic Variables Accreting WD Gravitational Energy: Dwarf novae

Mainly UV

Episodic outburst

Cataclysmic Variables Accreting WD Gravitational Energy: Dwarf novae

Mainly UV

Episodic outburst

SS Aur

Cataclysmic Variables Nuclear Energy: Novae

Build up shell of H on surface of WD Bottom heats, fusion, explosion (degen. press.)

Shell blown into space

Nova Cygni 1992

C/O

H

Novae

Old Nova Persei

Novae

Z Cam

Dwarf nova with old nova shell

Zoology of Binary Stars

Type Ia Supernovae •  Not associated with massive, young stars

•  Not core collapse supernova •  No hydrogen or helium •  No stellar remnant (corpse: WD, NS, or BH)

Type Ia Supernovae Spectra:

•  No H, He •  Dominated by Fe, Co lines

No compact object (NS or BH) ever found in Type Ia remnant (e.g., no pulsar)

Type Ia Supernovae •  WD accretes to M > MCh Chandrasekhar limit •  Starts to implode, heats up

•  Mainly C/O (not Fe), nuclear fuel, burns, explodes •  Enuc > Egrav for WDs, WD blows up completely

Accretion by WD, old, low mass, dead star C/O WD → no H, He WD blows up completely → no stellar remnant Enucl ≈ 0.001 x M� c2 ≈ 1051 ergs

Type Ia Supernovae •  Burn C → “Fe”

Type Ia Supernovae •  Burn C → “Fe”

•  Common lighter elements beyond H (He, C, O, …) have Z=N=even

•  Fusion will make only Z=N=even directly

•  e.g. 12C + 12C → 20Ne + 4He

•  56Fe has Z = 26, N = 30, A = 56 → cannot make directly •  Nearest even-even isotope to 56Fe is 56Ni

•  Fusion burns C → 56Ni •  56Ni radioactive

56Ni → 56Co → 56Fe 6.4 d 77 d

Type Ia Supernovae

6.4 d 77 d Light curve double

exponential

Type Ia Supernovae •  Fusion makes Ni, Co, Fe → lines in spectrum

Each Type Ia makes ~ 0.6 M� of iron •  Core collapse SN, iron core → NS or BH

Type Ia SN make most of iron in Universe

Zoology of Binary Stars

Zoology of Binary Stars

X-ray Binary Stars •  BH or NS accreting from normal star

•  Egrav > Enuc •  T ~ 108 K •  L ~ 1036 - 1039 ergs/s •  Mainly X-ray emission •  BH brighter and hotter

Zoology of Binary Stars

X-ray Binary Pulsar •  NS accreting from normal star

•  Strong magnetic field, gas channelled onto magnetic poles •  Makes X-ray pulses

X-ray Burster Layer of accreted H eventually burns

•  Burst of X-rays •  Egrav > Enucl , material not blown off

NS

H

X-ray Binary Pulsar Spin-Up •  Accreted material has high angular momentum

•  Spins up neutron star (true of ~all X-ray binary pulsars)

Millisecond Radio Pulsars

Very fast rotation Very weak magnetic field Very Accurate Clocks Many in globular clusters OLD Most are binaries (circles) Not on life track of normal radio pulsars How are they made?

Millisecond Pulsars •  Accretion spins up NSs in binaries •  Accretion and age weaken magnetic field •  After second star dies or accretion stops •  Recently, several objects caught in transition

X-ray binary çè millisecond pulsar Millisecond Pulsars (``Recycled Pulsars’’)

•  Older pulsars (many in globular clusters) •  Most found in binaries •  Very rapid rotation (Prot ~ 1 msec = 0.001 sec •  Weak magnetic field, dP/dt ~ 10-20 sec/sec •  Very good clocks!!

Binary Pulsars - Tests of General Relativity

PSR1913+16 •  1974, Hulse-Taylor discover •  Orbital Period 8 hours, very compact •  Elliptical orbits, determine masses very accurately, ~1.4 M�

PSR 1913+16 Orbit contracting due to gravitational waves Rate exactly matches General Relativity All other theories fail

PSR 1913+16 - Noble Prize 1993

Neutron Star Masses X-ray Binary Pulsars and Binary Millisecond Pulsars = NSs in binaries, derive masses

Neutron Star Masses

1.97+- 0.04 Msun NRAO/UVa

Neutron Star Masses X-ray Binary Pulsars and Binary Millisecond

Pulsars = NSs in binaries, derive masses

Most young NSs have M ~ 1.4 M�

Formed by collapse of iron core in massive star

Maximum mass > 1.97 M�

Rules out quark matter, other exotic possibilities for NS interiors

Zoology of Binary Stars

Gamma-Ray Bursts First lecture

Accidental Discovery 1960’s

Long Bursts:Collapsar Supernova Due to Jets from a

Black Hole?

Short Bursts: NS-NS or NS-BH Mergers to Form a Black Hole?

LIGO Detects Gravitational Waves NS-NS Mergers on August 17!

LIGO Detection GW source = Short GRB in nearby galaxy

è Confirms NS-NS merger theory for Short GRB

After the burst, kilo-nova = ejection of highly radioactive heavy nuclei made in neutron-rich environment

èConfirms theory for production of heaviest elements via NS-NS mergers

Where gold comes from

LIGO Detects Gravitational Waves NS-NS Mergers on August 17!

Zoology of Binary Stars

X-ray Binary Black Holes •  First BH detected Cygnus X-1

•  Like NSs, but brighter and hotter, no pulses, no nuclear energy •  Highly irregular emission

X-ray Binary Black Holes Often, first detected as high mass stellar corpse

X-ray Binary Black Holes •  First BH detected Cygnus X-1

•  Like NSs, but brighter and hotter, no pulses, no nuclear energy •  Highly irregular emission •  Highly Doppler and Gravity (red)shifted X-ray lines

X-ray Line from Black Hole Grav. redshift

Dopp redshift Dopp blueshift

Accretion Disks Highly blueshifted and redshifted (Dopper and

gravity) from accretion disk gas.

X-ray Line from Black Hole Grav. redshift

Dopp redshift Dopp blueshift

X-ray Binary Black Holes •  First BH detected Cygnus X-1

•  Like NSs, but brighter and hotter, no pulses, no nuclear energy •  Highly irregular emission •  Highly Doppler and Gravity (red)shifted X-ray lines •  Make both light and kinetic energy in jets

Jets from Black Holes

Jets from Black Holes

Jets from Black Holes

Jets from Black Holes

Jets from Cygnus X-1 BH

Paradox of Black Holes •  Blackest things in Universe

•  no light escapes from event horizon, but . . .

•  As material falls in, makes more light than any other objects in Universe

•  Brightest lights in Universe

•  Best garbage disposals in Universe

•  nothing escapes from event horizon, but . . .

•  As material falls in, part is shot out in jets at v ~ 0.9999 c •  Most powerful cannons in Universe