High-Time Resolution Astronomy across the e-m Spectrum Gottfried Kanbach, MPE, Garching Variability on short timescales in astronomical objects: • Absorption, Eclipses or Beaming effects • Luminosity changes if Ω is constant in Δ t I= L / Ω d 2 → Δ I ~ Δ L ε ~ Δ L Δ t / (c Δ t) 3 ~ Δ L / Δ t 2 If Δ I is large enough to be observable, the energy density in the emitting volume can be extremely large if Δ t is small. Such values can often only be realized around compact objects (WD, NS, BH) or in explosions. "Universe Probed by Radio" Kashi/Urumqi, China
M.Harwit: Phys.Today, Nov. 2003 "Universe Probed by Radio" Kashi/Urumqi, China
Timescales in Astronomy (long duration): Months–Days: Supernovae Microlensing events Days-Hours: Pulsating variables Asteroid rotation mostly optical Close binary stars Hours-Mins: Exoplanet transits Stellar seismology Binary-star interactions multiwavelength AGN outbursts (blazars) "Universe Probed by Radio" Kashi/Urumqi, China
Superluminal (ca 4 c) motion in blazar 3C 279 VLBI 22 GHz / 1.3 cm (Ann Wehrle & Steve Unwin, JPL/CalTech) "Universe Probed by Radio" Kashi/Urumqi, China
Variability at >100 MeV γ -ray energies "Universe Probed by Radio" Kashi/Urumqi, China
SED 3C279 at 4 Epochs "Universe Probed by Radio" Kashi/Urumqi, China
AGN Standard Model: Synchrotron & Inverse Compton Relativistic Jet Γ ~ 10 Doppler Boost! BLR clouds o EC (BLR) e IC (SSC) Shocks τ γγ (E) > 1 ~ 500 R S EC (disk) Supermassive Black Hole ‚Isotropic‘ Luminosities: 10 48 - 10 49 erg/s with accretion disk -> reduced to ~ 10 45 erg/s after Doppler correction "Universe Probed by Radio" Kashi/Urumqi, China
Blazar Identification Example: 3EG J2006-2321 First Clue: Gamma-ray variability Radio sources in the error box One flat-spectrum radio source, 260 mJy at 5 GHz; one marginally-flat source, 49 mJy; other sources are much weaker Optical observations: The 49 mJy source is a normal galaxy; The 260 mJy source has an optical counterpart with a redshift z=0.83 Variable optical polarization is seen. Spectral energy distribution is bimodal like other blazars Only an X-ray upper limit found. Conclusion: 3EG J2006-2321 is a flat spectrum radio quasar (FSRQ) "Universe Probed by Radio" Wallace et al. Kashi/Urumqi, China
Timescales: (short duration) min - sec: Gamma-ray bursts cataclysmic variables sec-msec: Pulsars Quasi-periodic oscillations, QPOs msec – μ sec: Accretion instabilities Photon-gas effects Neutron-star oscillations μ sec – nsec: Photon emission mechanisms Giant radio bursts in pulsars Photon quantum statistics "Universe Probed by Radio" Kashi/Urumqi, China
Gamma-Ray Bursts GRBs show a large variety of lightcurves with rapid variability short long (~20 sec) (~ 5 min) episodic "Universe Probed by Radio" Kashi/Urumqi, China
Credit: P.Meszaros, 2004 "Universe Probed by Radio" Kashi/Urumqi, China
Generic GRB model Collapse of a Internal massive star Shocks ⇒ black hole with External Delayed accretion disk and Shocks (forward/reverse) Injection: relativistic jet ( Γ >100) Afterglow prompt burst γ X O R t eng : t dec : Energy transport: b.h.-torus E o , Γ o , n relativistic particle jet fall-back times or Poynting Flux magnetar if t eng >t dec : signature of central engine should be visible in afterglow "Universe Probed by Radio" Kashi/Urumqi, China
Nature, 422 , 286, 20 March 2003 Gamma Ray Bursts: Optical afterglows HETE II GRB021004 t o = +193 sec +537 sec 12:06:14 UT "Universe Probed by Radio" Kashi/Urumqi, China
ROTSE LOTIS 86.4 sec "Universe Probed by Radio" Kashi/Urumqi, China
The Afterglow Phase of (some) GRBs The central GRB engine deposits energies of typically 10 52 erg (isotropic) into a very small volume ( Δ t c ~ 10 11 cm) The result is a relativistically expanding fireball (jet) with typical initial Lorentz factors of a few 100. Onset of Afterglow (deceleration ~ t -0.5...1.0 log I time scale): t dec ~ 2.4s (E 52 /n) 1/3 ( Γ o /300) -8/3 (1+z) ~ t -1.8...2.4 t ~ 10 d log t "Universe Probed by Radio" Kashi/Urumqi, China
John M. Blondin (North Carolina State University) Hydrodynamics on supercomputers: Interacting Binary Stars "Universe Probed by Radio" Kashi/Urumqi, China
Kilohertz quasiperiodic oscillations in Sco X-1 (Miller, Strohmayer, Zhang & van der Klis, RXTE ) "Universe Probed by Radio" Kashi/Urumqi, China
A black hole transient in 2000 : XTE J1118+48 (=KV Uma) • transient X-ray source during Jan – Jul 2000 • Hard spectral state with high variability • high optical / X-ray luminosity ratio • nearby object (~ 2 kpc) at high galactic latitude • estimated mass of compact star > 6 M � Correlated timing observations between X-rays (RXTE-PCA) and optical (OPTIMA) were carried out during July 4-8, 2000 A total of 2.5 hours of coincident measurements were performed! (Kanbach, Straubmeier, Spruit, and Belloni, 2001, Nature,414, 180) "Universe Probed by Radio" Kashi/Urumqi, China
Artist‘s Illustration of XTE J1118+48 "Universe Probed by Radio" Kashi/Urumqi, China
´Reprocessing´ or ´Light-Echoes´ X-opt correlation Heating Shadowing? Optical pulse preceding delayed X-ray pulse "Universe Probed by Radio" Kashi/Urumqi, China
X-ray optical correlations Positive correlation with short rise (~ 100ms) Maximum at ~ 500 ms; length ~ 5 sec Anti-correlation at –2 sec:´precognition dip´ "Universe Probed by Radio" Kashi/Urumqi, China
Emission Models: The brightness temperature and the SED indicate that self-absorbed cyclo-synchrotron emission causes the optical signal The size of the emitting region is < 30,000 km A ´quasi spherical´ slow outflow crossing photospheric surfaces: EUV @ 10 7 - 10 8 G optical @ 10 6 G, r=20000 km EUV UV optical radio emission blobs fast jet ß ~ 0.5-0.9 slow outflow v < 30000 km/s optical emission @ d~ 20000 km A ´jet-like´ outflow: "Universe Probed by Radio" Kashi/Urumqi, China
Accreting Binary sources Neutron Star or Black Hole Binary ( μ Blazar) Emission from accretion disk and jet Cataclysmic Variables: e.g. AM Her type: A highly-magnetic white dwarf (~10 7-8 G) in locked rotation around a low mass star ( ~ 0.3 M o ) Emission from accretion stream and hot spots (thermal and synchro-cyclotron) "Universe Probed by Radio" Kashi/Urumqi, China
Cataclismic Variable: Type Polar / AM Her Observations of HU Aqr (Orbital Period 125 min) from ESO/La Silla 2.2 m and Skinakas Observatory/Crete 1.3m HU Aqr (RE 2107-05): d ~ 200 pc, i>85° Orbitalvelocity ~ 200 km/s Zyklotronstrahlung H Secondary Star Accretion Magnetic White Dwarf, (M4V, ~0.3 M o ) stream B~4x10 7 G, m v ~ 15, ~0.9 M o 6x10 10 cm "Universe Probed by Radio" Kashi/Urumqi, China
HU Aqr: a cataclysmic variable with an orbital period of 125 HU Aqr min and eclipses 16000 21 Sep 2001 05 Jul 2000 14000 12000 counts / sec 10000 8000 6000 4000 2000 0 -2000 0 2000 4000 6000 8000 10000 time (s) Pre-eclipse Dip Absorption by Synchrotron Maxima Accretion ⊥ to B-field Stream "Universe Probed by Radio" Kashi/Urumqi, China
Eclipse Detail Accretion Spot Stream Sec.Star White Dwarf ? dt~ 7 sec = 1400 km dt ~ 6 sec = 1200 orbital velocity km Size of the polar ‚hot‘ spot ~200 km/s "Universe Probed by Radio" Kashi/Urumqi, China
New optical outbursts on HU Aqr: Possible explanation: clumps (inhomogeneities) in the accretion stream 1 sec 3 sec sky bkgnd sec "Universe Probed by Radio" Kashi/Urumqi, China
Pulsars "Universe Probed by Radio" Kashi/Urumqi, China
PSR Multiwavelength Lightcurves "Universe Probed by Radio" Kashi/Urumqi, China
Pulsar Science Outer Gap Emission: multi- λ Polar Cap Emission: multi- λ Lightcurves Lightcurves in Phase Not in Phase Prototype: Crab Prototype: Vela Synchrotron and Thermal Emission from NS inverse Compton surface Emission from Magnetosphere "Universe Probed by Radio" Kashi/Urumqi, China
Nebula / Pulsar Polarization (OPTIMA) 8% ; 139° 6% ; 145° 7% ; 138° close to pulsar: degree: 8-13% angle ~ 140° 6% ; 144° (Schmidt&Angel, 79) 8% ; 145° "Universe Probed by Radio" Kashi/Urumqi, China
Kellner, 2002 Crab Polarisation (OPTIMA) 1 ⋅ U Θ = arctan angle of polarisation: 2 Q Measure lightcurves for different positions of the rotating polarisation filter at [ φ 0 , φ 0 +90°] and [ φ 0 +45°, φ 0 +135°]. Calculate Stokes-Parameters: Q=I(0°)-I(90°), U=I(45°)-I(135°) 2 + 2 Q U = degree of polarisation: V I P2 P1 "Universe Probed by Radio" Kashi/Urumqi, China
The polarisation angle: Magnetic field geometry in the emission regions Magnetic Field Line of Sight Plane of Polaris. Curvature Radn. e l g n A Romani et al., 1995: outer gap model "Universe Probed by Radio" Kashi/Urumqi, China
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