ray emission from pulsars and their nebulae Roberta Zanin - - PowerPoint PPT Presentation
ray emission from pulsars and their nebulae Roberta Zanin (Max-Planck Institut fr Kernphysik) Outline Pulsars-pulsar wind nebulae supernova remnants ray pulsars standard paradigma before Fermi-LAT launch Main results
Roberta Zanin (Max-Planck Institut für Kernphysik)
ü Pulsars-pulsar wind nebulae – supernova remnants ü γ–ray pulsars ü standard paradigma before Fermi-LAT launch ü Main results in the last years ü New paradigma ü pulsar wind nebulae ü current theoretical understanding ü TeV results
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G21.5-0.9 Chandra
COSMIC RAY PHYSICS COSMIC RAY PHYSICS ü factories of positrons & electrons ASTROPHYSICS ü physics of compact objects ü physics relativistic shocks
Van der Swaluw+03
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Oblique rotator in a magnetic dipole field αà intrinsic physics ζ-> observed properties the magnetosphere is plasma filled induced E extract charges from the NS ü only leptons or also ions?
(Amato+2003, 2006)
ideal MHD (E B =0) & free force conditions (ρE+J✕B =0) dissipate rotational energy loss
spin-down luminosity light cylinder RLC ~108 cm 3
Oblique rotator in a magnetic dipole field αà intrinsic physics ζ-> observed properties the magnetosphere is plasma filled induced E extract charges from the NS ü only leptons or also ions?
(Amato+2003, 2006)
ideal MHD (E B =0) & free force conditions (ρE+J✕B =0) dissipate rotational energy loss
spin-down luminosity light cylinder RLC ~108 cm 3
(Polar cap: Ruderman+ 75, Harding+ 78 Outer gap: Cheng+86, Romani+95 Slot gap: , Arons 83, Muslimov+ 03, 04)
ü acceleration geometries à regions of unscreened fields: = GAPS ü inside the light cylinder ü accelerated particles emit curvature radiation ü pair production to account for particles acceleration, we need regions with deviations from the free-force conditions
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young radio-faint young radio-laud MSP black widow redbacks
> 200 γ-ray PSRs
ü phase folding using radio (X-ray) timing solutions ü blind periodicity searches in Fermi data:
ü GW algorithms (Plesch+2012) + Einstein@home ü mostly radio-quiet (Clark+2017) + few MSP (Clark+2016)
ü radio follow-up of Fermi unidentified sources
> 2500 radio PSRs
Grenier & Harding 2015
6 50 GeV 100 MeV 1MeV 50keV
credits to Harding
YOUNG PULSARS
ü radio loudness/quiteness ü not an intrinsic property, but a function
ü larger Ė than radio: just a selection effect ü 1011<BNS<1014 G
7 50 GeV 100 MeV 1MeV 50keV
credits to Harding
YOUNG PULSARS
ü radio loudness/quiteness ü not an intrinsic property, but a function
ü larger Ė than radio: just a selection effect ü 1011<BNS<1014 G
MILLISECOND PULSARS
ü older ü ms P spun up by accretion from a binary companion ü 108<BNS<1011 G ü 50% of the known MSP
7 50 GeV 100 MeV 1MeV 50keV
YOUNG PULSARS
ü radio loudness/quiteness ü not an intrinsic property, but a function
ü larger Ė than radio: just a selection effect ü 1011<BNS<1014 G
MILLISECOND PULSARS
ü older ü ms P spun up by accretion from a binary companion ü 108<BNS<1011 G ü 50% of the known MSP Same variety of
differences in B, Ė
7 50 GeV 100 MeV 1MeV 50keV
Grenier+2015
MSPs are efficient emitters (η>10%) ü large B at LC More efficient after 104-106 yr
8 50 GeV 100 MeV 1MeV 50keV
Large part of the magnetosphere is free-force (pair production)
The experimental proofs: ü atlases of lightcurves as a function of α & ζper each model ü the double-peak lightcurves better fitted by high-altitude emission models
ü
ü δ-Δ anti-correlation
(Romani+1995, LAT coll. 2010, Watters+2009, 2010…)
(Watters+2009,2010, Pierbattista+2012,2015)
ü Γ=-1.5±0.2; ü Ec=2.9±2.0 GeV ü b<1 à caustic outer gaps
9 50 GeV 100 MeV 1MeV 50keV
The experimental proofs: ü atlases of lightcurves as a function of α & ζper each model ü the double-peak lightcurves better fitted by high-altitude emission models
ü
ü δ-Δ anti-correlation
(Romani+1995, LAT coll. 2010, Watters+2009, 2010…)
(Watters+2009,2010, Pierbattista+2012,2015)
ü Γ=-1.5±0.2; ü Ec=2.9±2.0 GeV ü b<1 à caustic outer gaps
9 50 GeV 100 MeV 1MeV 50keV
Fermi-LAT coll. 2010, Djannati-Atai 2017
The experimental proofs: ü atlases of lightcurves as a function of α & ζper each model ü the double-peak lightcurves better fitted by high-altitude emission models
ü
ü δ-Δ anti-correlation
(Romani+1995, LAT coll. 2010, Watters+2009, 2010…)
(Watters+2009,2010, Pierbattista+2012,2015)
ü Γ=-1.5±0.2; ü Ec=2.9±2.0 GeV ü b<1 à caustic outer gaps
9 50 GeV 100 MeV 1MeV 50keV
ü γ-ray leading the radio peak lightcurves require polar cap-like regions ü too many observed high-Ė ü phase-resolved spectra show: ü the peak emission Lγ∞ Ė1/2 ü the bridge emission with Lγ∞ Ė no model can account for the complete variety of lightcurves (Grenier+ 2015, Harding2016,) regions of both high- and low- multiplicity (Renault+2016)
10 50 GeV 100 MeV 1MeV 50keV
ü a new population? only 18! (Kuiper+2015) ü young: τ <50 kyr ü Ė > 4 x 1036 erg/s ü mainly 1 broad peak LC ü SED peaking at 10 MeV ü 7/18 are LAT PSRs ü the remaining are the high-Ė missed by LAT
Kuiper+2015
ü synchrotron emission from magnetic pairs
(Lin+2009,Wang+2013)
ü no HE emission just a geometrical specific case (α≅ς & α<30)(Wang+2013,2015)
11 50 GeV 100 MeV 1MeV 50keV
MAGIC coll. 2016
ü the Crab pulsar shows a new spectral component up to hundreds
ü one single component above 10 GeV to TeV , ü cutoff > 700 GeV
(MAGIC coll. 2016) 12 50 GeV 100 MeV 1MeV 50keV
MAGIC coll. 2016
ü the Crab pulsar shows a new spectral component up to hundreds
ü one single component above 10 GeV to TeV , ü harder for P2 ü cutoff > 700 GeV
(MAGIC coll. 2016)
ü inverse Compton radiation close/beyond the LC
(Lyutikov+2012,Hirotani+2015, Petrí2012, Mochol+2015, Bogovalov +2000, Aharonian+2012) 12 50 GeV 100 MeV 1MeV 50keV
Pdot glitch ü 20% flux drop ü increase in spin down rate ü change in the pulsar profile ü decrease energy cutoff
(Allaford+2013, Ng+2016) Ng+2016
First switch mode in a γ-ray pulsar: J2021+4026 ü a re-arrangement of the B structure à α change (Allaford+2013) Pulsars are not steady at lower energies: ü in radio: glitches (starquakes or superfluids), giant pulses ü intermittent radio pulsars and transitional pulsars (Torres+2016)
13 50 GeV 100 MeV 1MeV 50keV
ü Soft γ-ray emission from low-altitudes only for high-Ė ü high-energy emission come from high-altitude regions ü High-energy efficiency is increasing with time (Lγ ∞ Ė1/2) ü none of the local emission models can account for the variety of observables: a combination of them would work? ü Some MSPs have emission from polar caps regions ü the Crab pulsar has a new spectral component reaching TeV à inverse Compton emission beyond the LC? ü PSRs can be variable sources with flux and spectral changes related to changes of a , thus glitches??
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equatorial current sheet separatrix
ü current sheets are important dissipative regions ü particle acceleration in the current sheets via magnetic reconnection (Uzensky+14, Cerutti+15) ü flux dissipation larger for α=0 Theoretical advances… need to account for energy dissipation
ü dissipative free-force à macroscopic conductivity par. (Komissarov07,Spitkovski12, Kalapotharakos+12, Chen+14) ü free-force-inside-Dissipative-Outside (FIDO) (Kalapotharakos+14, Brambilla+15) ü PIC ab-initio (Philippov+2014,2015, Cerutti+15,16) Uzensky+14 15
HIGH-MULTIPLICITY (pair production) à young PSR ü nearly free-force solution inside the LC ü gaps like regions forming close to the separatrix and polar caps ü weakly dissipative: 20% dissipation within 2RLC (for α = 0) LOW-MULTIPLICITY (supplied only from NS) à old PSR ü no separatrix: the equatorial sheet is electrostatically supported ü highly dissipative 40% dissipation beyond the LC ü MeV synchrotron emission from polar caps à soft γ-ray pulsars ü GeV curvature radiation mainly close to the LC à high-altitude GeV ü TeV ? Promising… ü GeV curvature radiation mainly beyond the LC à high-altitude GeV
Contopoulos16, Cerutti+15 16
ü Soft γ-ray emission from low-altitudes only for high-Ė Yes! ü high-energy emission come from high-altitude regions Yes! ü High-energy efficiency is increasing with time (Lγ ∞ Ė1/2) Yes ü none of the local emission models can account for the variety of observables: a combination of them would work? ü Some MSPs have emission from polar caps regions No ü the Crab pulsar has a new spectral component reaching TeV à inverse Compton emission beyond the LC? ? ü PSRs can be variable sources with flux and spectral changes related to changes of a , thus glitches?? No PIC simulations just started, but in the right direction
17
Kargaltsev+13
ü among the young PSRs the most energetic ones Ė > 1035 erg/s ü ~100 known
SYNCHROTRON IC 18
ü mainly seen in X-rays and TeV
credits to Aharonian
ü big variety seen with high-resolution Chandra images
19 credits to Pavlov
ü big variety seen with high-resolution Chandra images
19
PWNe: the most common class of TeV emitters
Donath+2016 Parsons’s talk today
ü big variety seen with high-resolution Chandra images
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PWNe: the most common class of TeV emitters
Donath+2016 Parsons’s talk today
ü X-rays trace recent history ü close to the termination shock ü depends on the pulsar wind characteristics ü γ rays show the integral emission along the pulsar life ü depends also on environment (radiation field)
ü In the standard view: ü at the TS plasma is heated, the toroidal magnetic field of the pulsar wind compressed ü particles are accelerated ü accelerated particles propagate at non-relativistic speeds towards the SNR shell. Well described by magnetic- hydrodynamic (MHD) models.
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Pulsar wind characteristics: ü anisotropic energy flux distribution ü stripped morphology with an equatorial belt of extension 2*ζ F ∞ sin2(α) (Bogovalov 99) F ∞ sin4(α) (Tchekhovsky+13,15) F ∞ sin2(α) (Bogovalov 99) F ∞ sin4(α) (Tchekhovsky+13,15) Particle injection spectrum: ü power-law spectrum ü 2 populations of electrons
credits to Olmi
Most of what we know comes from the Crab nebula
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X-ray
Jet counter jet wisps torus knot
2D MHD models reproduce well the morphology and its brightness variability in the inner region (1/5 nebula, Olmi+2015) but not the B structure on large scales
Volpi+2008 Olmi+2014
Most of what we know comes from the Crab nebula
22
X-ray
Jet counter jet wisps torus knot
2D MHD models reproduce well the morphology and its brightness variability in the inner region (1.5 nebula, Olmi+2015) but not the B structure on large scales
Volpi+2008 Olmi+2014
Most of what we know comes from the Crab nebula
inverse Compton emission overestimated
credits to E. Amato Volpi+2008 22
σ=1.5
Reduced dimensionality of the simulation causes an artificial compression of B around the polar axis: less instabilities accounted σ-problem solved? NOT YET 3D MDH are highly dissipative (Porth+2014) even though magnetic dissipation seems to become less important after 100 ys
(Olmi+2016) 3D 2D Porth+2013
3D MHD models allow high magnetization at the TS (σ>1) (Porth+2013, Porth+2014) High-σ makes Fermi I acceleration mechanism unlike
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radio radio
Crab is a PeVatron, but how/where? ü FERMI I ü narrow equatorial sector (low σ) ü optical/X-ray particles (p=2)
(Spitkovsky2008, Sironi+2011)
ü MAGNETIC RECONNECTION ü elsewhere (high σ) ü radio electrons (p=1.5)
(Lyubarsky2003, Lyubarsky+2008, Sironi+2011) Fermi I reconnection reconnection Olmi+2015
wisps at different λ have distinct velocities and positions
(Bietenholz+2004, Schweizer+2013) à different mechanism at work (Olmi+2015) 24
ü flux doubling in 8 hr ü exceed the synch ü photon index 1.3 ü 1/yr
τacc=τsyn B~few mG>>200mG PeV ELECTRONS
ü B> 2mG
ü no optical/X-ray counterpart à no location yet
Γ=1.27
Fast magnetic reconnection in compact regions close to the TS
(Cerutti+2013, 2014, Lyutikov+2016
Buhler+2012 Buhler+2014 Weisskopf+2013,Rudy+2015, Bietenholz+2015 Tavani+2011, LAT 2011, Striani+2013, Balbo+2012 50 GeV 100 MeV 1MeV 50keV 25
ü X-ray + TeV to constrain particle spectra and B
50 GeV 100 MeV 1MeV 50keV 26 credits to Khangulyan
ü X-ray + TeV to constrain particle spectra and B
MAGIC coll. 2015 MAGIC coll. 2015 the B-structure is relevant
ü to infer possible hadronic component of the wind emerging above the K-N cutoff (Amato+2003, Bednarek+2003)
ü high-energy electron distribution from spatial
resolved measurements
Zefi’s talk today 50 GeV 100 MeV 1MeV 50keV 26
Holler’s talk today
H.E.S.S. coll. 2015
the first extragalactic PWN: in the large Magellanic Cloud ü much less efficient accelerator than the Crab (B ~ 45 uG) ü much more efficient γ-ray emitter because of the enhanced radiation field (LH 99) the radiation field has a significant impact in the determination of the LIC
50 GeV 100 MeV 1MeV 50keV 27
ü B decreases with time due to adiabatic expansion à more efficient in γ rays ü when the SNR reverse shock reaches the PWN, its expansion is stopped ü pulsar is offset due to asymmetric interaction with the surroundings (H.E.S.S. coll. 2017) ü extended TeV emission (tens of pc) ü energy-dependent morphology as signature of leptonic cooling (H.E.S.S. coll. 2006, 2013,
Grondin+2011) credits to Slane 28 Martin+12
390 hrs 1-10 TeV HESS J1825-137
1° extension = 100 pc (@ 4kpc) diffusion transport not likely
Mitchel’s talk today Vela X Mitchell+2016 50 GeV 100 MeV 1MeV 50keV 29 radio map & GeV contours X-ray map & TeV contours
ü Cocoon: 5pc long south the PSR ü SNR reverse shock crash (104 ys ago, Blodin+2001) ü efficient acceleration/transport ü no spectral changes (not cooling domin., advection) ü Radio/GeV/(TeV) nebula: escaping?
H.E.S.S coll12 Hinton+11 Tibaldo’s talk today
Salesa’s talk today 2° radius = 7 pc τage > τThompson =3*103 yr
D=2e27cm2/s within the Bohm limit Can this source explain the positron excess? HAWC coll 2017 Geminga
@ 200 pc, t=300 kyr
Aharonian+95
31 CTA talk today
ü 3D MHD is moving towards a complete description of both spectral and morphological observables ü Both Fermi and magnetic reconnection at work depending
ü Crab flares as another manifestation of magnetic reconnection ü Typical TeV PWNe are the middle aged one. ü Brightest with high-precision spatial-dependent results provide important tools to constrain particle transport ü More data are needed to have a complete picture: CTA will detect hundreds of PWN with an angular resolution of 1 arcmin.
an entire session about PWNe this afternoon!
Porth+14
the first extragalactic PWN
Saito+2016 Saito+2016 50 GeV 100 MeV 1MeV 50keV
real flare?
Fermi-LAT coll. 2010
co-rotation ceases at the LC: B-lines open up and plasma flows ü monopole approximation
(Michel 1973, Bogovalov1999) confirmed by numerical simulations (Spitkovsky06, Timokhin06)
ü highly magnetized at the LC ü Striped wind as possible solution to the magnetic dissipation
(Coroniti1990, Lubrasky, Kirk2002)
ü magnetic reconnection? ü Most of the energy flows at high-altitude F sin2(α)
credits to I. Mochol Spitkovski06 5
CLASS I: γ-RAY PEAK LAGs RADIO PEAK ü mainly young γ-ray PSRs ü 75% of the young: double narrow widely spaced peaks ü P2/P1 increase with energy ü often bridge emission
CLASS I: γ-RAY PEAK LAGs RADIO PEAK ü mainly young γ-ray PSRs CLASS II: γ-RAY PEAKS ALIGN WITH RADIO ONES ü mainly MSPs ü Crab & J0540 ü Crab pulsar
CLASS I: γ-RAY PEAK LAGs RADIO PEAK ü mainly young γ-ray PSRs CLASS II: γ-RAY PEAKS ALIGN WITH RADIO ONES ü mainly MSPs ü Crab & J0540 ü Crab pulsar CLASS III: γ-RAY PEAK LEAD RADIO PEAK ü exclusively MSPs