High-Time Resolution Astronomy across the e-m Spectrum Gottfried - - PowerPoint PPT Presentation

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High-Time Resolution Astronomy across the e-m Spectrum Gottfried - - PowerPoint PPT Presentation

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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 is constant in t I= L /

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"Universe Probed by Radio" Kashi/Urumqi, China

Variability on short timescales in astronomical objects:

  • Absorption, Eclipses or Beaming effects
  • Luminosity changes

I=L/Ωd2 → ΔI ~ ΔL

if Ω is constant in Δt ε ~ ΔL Δt / (c Δt)3 ~ ΔL / Δt2 If ΔI is large enough to be observable, the energy density in

the emitting volume can be extremely large if Δt is small. Such values can often only be realized around compact

  • bjects (WD, NS, BH) or in explosions.

High-Time Resolution Astronomy across the e-m Spectrum

Gottfried Kanbach, MPE, Garching

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"Universe Probed by Radio" Kashi/Urumqi, China M.Harwit: Phys.Today, Nov. 2003

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"Universe Probed by Radio" Kashi/Urumqi, China

Timescales in Astronomy (long duration):

Months–Days: Supernovae Microlensing events Days-Hours: Pulsating variables Asteroid rotation Close binary stars Hours-Mins: Exoplanet transits Stellar seismology Binary-star interactions AGN outbursts (blazars) mostly optical multiwavelength

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"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)

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"Universe Probed by Radio" Kashi/Urumqi, China

Variability at >100 MeV γ-ray energies

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"Universe Probed by Radio" Kashi/Urumqi, China

SED 3C279 at 4 Epochs

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  • e

BLR clouds

EC (disk) EC (BLR) IC (SSC)

Synchrotron & Inverse Compton

τγγ (E) > 1 ~ 500 RS

AGN Standard Model:

Relativistic Jet Γ ~ 10 Doppler Boost!

Shocks Supermassive Black Hole with accretion disk

‚Isotropic‘ Luminosities: 1048 - 1049 erg/s

  • > reduced to ~ 1045 erg/s after Doppler correction
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"Universe Probed by Radio" Kashi/Urumqi, China

Blazar Identification Example: 3EG J2006-2321

Spectral energy distribution is bimodal like other blazars

Conclusion: 3EG J2006-2321 is a flat spectrum radio quasar (FSRQ)

First Clue: Gamma-ray variability Radio sources in the error box One flat-spectrum radio source, 260 mJy at 5 GHz;

  • ne 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. Only an X-ray upper limit found.

Wallace et al.

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"Universe Probed by Radio" Kashi/Urumqi, China

Timescales: (short duration)

min - sec: Gamma-ray bursts cataclysmic variables sec-msec: Pulsars Quasi-periodic oscillations, QPOs msec – μsec: Accretion instabilities Photon-gas effects Neutron-star oscillations μsec – nsec: Photon emission mechanisms Giant radio bursts in pulsars Photon quantum statistics

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"Universe Probed by Radio" Kashi/Urumqi, China

Gamma-Ray Bursts

GRBs show a large variety of lightcurves with rapid variability long (~ 5 min) short (~20 sec) episodic

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"Universe Probed by Radio" Kashi/Urumqi, China

Credit: P.Meszaros, 2004

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Generic GRB model

γ X O R External Shocks (forward/reverse)

Afterglow

Internal Shocks Delayed Injection: prompt burst Collapse of a massive star ⇒ black hole with accretion disk and relativistic jet (Γ>100) Energy transport: relativistic particle jet

  • r Poynting Flux

t eng :

b.h.-torus fall-back times magnetar

t dec : Eo, Γo, n

if teng>tdec : signature of central engine should be visible in afterglow

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"Universe Probed by Radio" Kashi/Urumqi, China

Gamma Ray Bursts: Optical afterglows to = 12:06:14 UT +193 sec +537 sec

HETE II GRB021004

Nature, 422, 286, 20 March 2003

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"Universe Probed by Radio" Kashi/Urumqi, China

LOTIS ROTSE

86.4 sec

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"Universe Probed by Radio" Kashi/Urumqi, China

The Afterglow Phase of (some) GRBs

The central GRB engine deposits energies of typically 1052 erg (isotropic) into a very small volume (Δt c ~ 1011 cm) The result is a relativistically expanding fireball (jet) with typical initial Lorentz factors of a few 100.

log t log I

~ t-1.8...2.4 ~ t-0.5...1.0

t ~ 10 d

Onset of Afterglow (deceleration time scale): tdec~ 2.4s (E52/n)1/3 (Γo/300)-8/3 (1+z)

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"Universe Probed by Radio" Kashi/Urumqi, China

John M. Blondin

(North Carolina State University)

Hydrodynamics on supercomputers: Interacting Binary Stars

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"Universe Probed by Radio" Kashi/Urumqi, China

Kilohertz quasiperiodic

  • scillations in Sco X-1

(Miller, Strohmayer, Zhang & van der Klis, RXTE)

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"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

  • ptical (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)

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Artist‘s Illustration of XTE J1118+48

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´Reprocessing´ or ´Light-Echoes´

X-ray pulse Optical pulse preceding delayed X-opt correlation Shadowing? Heating

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"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´

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"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 @ 107- 108 G

  • ptical @ 106 G, r=20000 km

EUV UV

  • ptical

A ´jet-like´ outflow:

radio emission blobs fast jet ß ~ 0.5-0.9 slow outflow v < 30000 km/s

  • ptical emission

@ d~ 20000 km

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"Universe Probed by Radio" Kashi/Urumqi, China

Accreting Binary sources Cataclysmic Variables:

e.g. AM Her type: A highly-magnetic white dwarf (~107-8 G) in locked rotation around a low mass star (~0.3 Mo) Emission from accretion stream and hot spots (thermal and synchro-cyclotron)

Neutron Star or Black Hole Binary (μBlazar)

Emission from accretion disk and jet

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"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 Secondary Star (M4V, ~0.3 Mo) Magnetic White Dwarf, B~4x107G, mv ~ 15, ~0.9 Mo Accretion stream

HU Aqr (RE 2107-05): d ~ 200 pc, i>85° Orbitalvelocity ~ 200 km/s

6x1010 cm

Zyklotronstrahlung H

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"Universe Probed by Radio" Kashi/Urumqi, China

HU Aqr

time (s)

  • 2000

2000 4000 6000 8000 10000

counts / sec

2000 4000 6000 8000 10000 12000 14000 16000

21 Sep 2001 05 Jul 2000

HU Aqr: a cataclysmic variable with an orbital period of 125 min and eclipses

Pre-eclipse Dip Absorption by Accretion Stream Synchrotron Maxima ⊥ to B-field

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"Universe Probed by Radio" Kashi/Urumqi, China

Accretion Spot Stream Sec.Star White Dwarf ?

dt ~ 6 sec = 1200 km dt~ 7 sec = 1400 km Eclipse Detail

Size of the polar ‚hot‘ spot

  • rbital

velocity ~200 km/s

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"Universe Probed by Radio" Kashi/Urumqi, China

New optical outbursts on HU Aqr:

1 sec Possible explanation: clumps (inhomogeneities) in the accretion stream

sky bkgnd

3 sec

sec

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"Universe Probed by Radio" Kashi/Urumqi, China

Pulsars

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PSR Multiwavelength Lightcurves

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"Universe Probed by Radio" Kashi/Urumqi, China

Polar Cap Emission: multi-λ Lightcurves in Phase Prototype: Crab

Pulsar Science

Outer Gap Emission: multi-λ Lightcurves Not in Phase Prototype: Vela

Thermal Emission from NS surface

Synchrotron and inverse Compton Emission from Magnetosphere

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"Universe Probed by Radio" Kashi/Urumqi, China

Nebula / Pulsar Polarization (OPTIMA)

close to pulsar: degree: 8-13% angle ~ 140° (Schmidt&Angel, 79)

8% ; 139° 6% ; 145° 8% ; 145° 6% ; 144° 7% ; 138°

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"Universe Probed by Radio" Kashi/Urumqi, China

Crab Polarisation (OPTIMA)

Measure lightcurves for different positions

  • f the rotating polarisation filter

at [φ0, φ0+90°] and [φ0+45°, φ0+135°]. Calculate Stokes-Parameters: Q=I(0°)-I(90°), U=I(45°)-I(135°) I U Q V

2 2 +

= Q U arctan 2 1 ⋅ = Θ

P1 P2

angle of polarisation: degree of polarisation:

Kellner, 2002

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The polarisation angle: Magnetic field geometry in the emission regions

A n g l e

Line of Sight Plane of Polaris. Curvature Radn. Magnetic Field

Romani et al., 1995: outer gap model

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"Universe Probed by Radio" Kashi/Urumqi, China

New Emission Model: 2-pole caustic slot gap

Dyks and Rudak, 2002, 2003 Harding, Dyks, and Rudak, 2004

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"Universe Probed by Radio" Kashi/Urumqi, China

credit: A. Harding, GSFC

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Slot-gap Model (Muslimov & Harding, 2003,2004)

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"Universe Probed by Radio" Kashi/Urumqi, China

Slot Gap Emission Pattern on the celestial sphere: Magnetic inclination 45°, P= 33ms, Bo=8x1012 G

Muslimov & Harding, ApJ, 606, 1143, 2004

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"Universe Probed by Radio" Kashi/Urumqi, China

Model: Dyks et al., 2004

~ Correspondence of Polarization Characteristics

Measurement Two Pole Caustic Model (Dyks etal, 2004)

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"Universe Probed by Radio" Kashi/Urumqi, China

looking ahead....

New multi-beam surveys (Parkes, Swinburne...) Now about 1700 radio pulsars known

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"Universe Probed by Radio" Kashi/Urumqi, China

The Parkes Multibeam Pulsar Survey The The Parkes Parkes Multibeam Multibeam Pulsar Survey Pulsar Survey

The most successful survey ever: The most successful survey ever:

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P-P Diagram of Pulsar Population

.

Classical γ-ray pulsars X-ray ‚magnetars‘ ms PSRs

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"Universe Probed by Radio" Kashi/Urumqi, China

Galactic PSR Population with the new detections (~ 1500 pulsars) Galactic PSR Population with the new Galactic PSR Population with the new detections (~ 1500 pulsars) detections (~ 1500 pulsars)

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The Galactic Distribution of known Pulsars

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Population Synthesis of observed γ-ray pulsars (Gonthier et al., 2004)

(Sim) (Sim) (Sim) loud: 7 quiet:1 loud: 15-19 quiet:7-10 loud: 37 quiet:13 loud: 344 quiet:276

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Some Conclusions

  • Multiwavelength observations of variable

astronomical sources are essential to determine the physics of these objects

  • Radio/optical/X-ray mapping and source

characterization will be needed to identify new high-energy sources

  • for pulsars continuous monitoring of rotational

ephemerides is needed for high-energy data analysis (mostly from radio)