Pulsars,Magnetars and Fast Radio Bursts:
Roger Blandford KIPAC Stanford
30 xi 2017 CPT 1 Charles Messier
30 xi 2017 CPT 2 Sam Okoye discovers compact radio source
30 xi 2017 CPT 3 Franco Pacini predicts Crab Nebula Powered by Neutron Star
30 xi 2017 CPT 4 Jocelyn Bell Discovers Pulsars
30 xi 2017 CPT 5 Neutron Stars
•~10 km radius •Giant nucleus; 1057 neutrons •Magnetic field ~ 1012 Gauss •Superfluidity •Superconductivity •Thick crust •Shallow ocean
30 xi 2017 CPT 6 Crab Pulsar
30 xi 2017 CPT to 400 GeV7 ! Millisecond Pulsars • Rapidly spinning pulsars • 1 day -> 1-10 milliseconds! • Fastest 716 Hz F5# • Weak magnetic field • One has planets • Many in globular clusters • Recycled and spun up
30 xi 2017 CPT 8 Binary Pulsars
•Hulse-Taylor binary pulsar •Tests of general relativity •Gravitational radiation •Double pulsar •Two pulsars; now just one •Triple pulsar •Principle of Equivalence
30 xi 2017 CPT 9 GW 170817, GBM 170817A – BNS!
Binary neutron star 30 xi 2017 CPT 10 combined mass - 2.73-2.78 Msun Validated Conjectures-Discovery Space
Cosmography Background Nucleosynthesis Jet formation Nuclear physics Stellar evolution Relativistic shocks GR works Tests of GR SGRB=BNS … Heavy elements Distances g-rays beamed Wave30 xi 2017speed =c CPT 11 Pulsar Timing Array
•LIGO gravitational waves •Directly •Wavelengths ~ 1000 km •Timing pulsars •Wavelengths ~ light years
30 xi 2017 CPT 12 Crab Nebula Spectrum
TeV Synchrotron Radiation
Compton Scattering
30 xi 2017 Radio CPT Gamma Rays 13 Flaring behavior
Buehler et al
April 2011 Power~1029W
Singular events or power spectrum? No variation seen in other bands
30 xi 2017 CPT 14 Faraday’s Disk
Magnet
Conducting Disk Crank
Voltage: 50 PetaVolts Current: 300 TeraAmps Power: 100,000 Suns
30 xi 2017 CPT 15 Magnetars •Young neutron stars •~ 25 known •~ 0.01 pulsars •Magnetic not rotational energy • Up to 1000 x Crab field •Magnetic energy > 1040J •Elastic energy ~1039J •P~3-10 s •Born with ms periods? •Show violent explosions •Create X-rays and g-rays •Can rattle our atmosphere
•Q30 uakesxi 2017 or flares? CPT 16 Fast Radio Bursts • 2007 Lorimer (2001) burst • ~GHz (only?) ~1ms? radio bursts – Dispersed and broadened; DM => d ~1 Gpc? 33 – E ~ 10 fbeam J? 35-40 Thornton – TB ~10 K? – Can be highly linear and circular polarized? – ~ 40 FRB; all sky frequency ~10 mHz? • FRB 121102 – Repeat bursts z~ 0.2 dwarf galaxy; ongoing source, AGN? – Heterogeneous class; cf GRBs, SGRs… Many models: ET, DM, SGR/SN, AGN, PSR… Should learn much, soon, CHIME, DSA, ASKAP… 30 xi 2017 CPT MeerKat?17 Force-Free Electrodynamics
•Sufficient plasma for currents; insufficient for inertia
•Characteristics - Fast mode: w=k
- Intermediate: w=k||; Vg=1 along B; favored? Smooth ParticlE ElectroDYnamics VDt •Nonlinearity and wave steepening: dB/B ~ B-1/2 on open field lines - Cracking the whip Perhaps a current front propagates into magnetosphere
30 xi 2017 CPT 18 Observing a Current Front? • Pairs freely made
– tcool<
• tobs=s(r)-n.r – Depends on orientation with respect to open field lines • Doppler beaming – Maximum intensity from point of tangency 30 xi 2017 CPT 19 Propagation Effects • High brightness radio emission subject to: – Induced Compton Scattering – Stimulated Raman Scattering – Same as pulsars • Interstellar and Intergalactic Scintillation – Powerful probe of plasma turbulence spectra • Many correlations predicted • Gravitational Lensing – Await macrolensing delay in months for ~10-3 FRBs – Microlensing by stars
30 xi 2017 CPT 20 FRBs even more interesting as probes than as sources? Summary
• Pulsars/neutron stars still surprising us FRB interesting for astronomy, plasma astrophysics, cosmology? NS?, QED? • Magnetars - circumstantial evidence – Insufficient for conviction – Reasonable on energetic, environmental grounds? • Much will be learned over the next few years including by MeerKat/SKA!
30 xi 2017 CPT 21