ray emission from pulsars and their nebulae Roberta Zanin - PowerPoint PPT Presentation

γ ray emission from pulsars and their nebulae Roberta Zanin (Max-Planck Institut für Kernphysik)

Outline 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 1 R. Zanin 35 th ICRC, Busan 2017

PSR-PWN-SNR systems Van der Swaluw+03 G21.5-0.9 Chandra ASTROPHYSICS COSMIC RAY PHYSICS COSMIC RAY PHYSICS ü physics of compact objects ü factories of ü physics relativistic shocks positrons & electrons 2 R. Zanin 35 th ICRC, Busan 2017

Pulsars Oblique rotator in a magnetic dipole field α à intrinsic physics ζ -> observed properties dissipate rotational energy loss spin-down luminosity the magnetosphere is plasma filled induced E extract charges from the NS ü only leptons or also ions? (Amato+2003, 2006) ideal MHD (E Ÿ B =0) & free force conditions ( ρ E+J ✕ B =0) light cylinder R LC ~10 8 cm 3 R. Zanin 35 th ICRC, Busan 2017

Pulsars Oblique rotator in a magnetic dipole field α à intrinsic physics ζ -> observed properties dissipate rotational energy loss spin-down luminosity the magnetosphere is plasma filled induced E extract charges from the NS ü only leptons or also ions? (Amato+2003, 2006) ideal MHD (E Ÿ B =0) & free force conditions ( ρ E+J ✕ B =0) light cylinder R LC ~10 8 cm 3 R. Zanin 35 th ICRC, Busan 2017

The standard view to account for particles acceleration, we need regions with deviations from the free-force conditions ü acceleration geometries à regions of unscreened fields: = GAPS ü inside the light cylinder ü accelerated particles emit curvature radiation ü pair production (Polar cap: Ruderman+ 75, Harding+ 78 Outer gap: Cheng+86, Romani+95 Slot gap: , Arons 83, Muslimov+ 03, 04) 4 R. Zanin 35 th ICRC, Busan 2017

50 GeV The Fermi -LAT legacy > 2500 radio PSRs young radio-laud > 200 γ -ray PSRs young radio-faint MSP 100 MeV black widow redbacks Grenier & Harding 2015 1MeV 50keV 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 6

2 classes of γ -ray pulsars: 50 GeV young and millisecond 100 MeV YOUNG PULSARS ü radio loudness/quiteness ü not an intrinsic 1MeV property, but a function of the viewing angle ü larger Ė than radio: 50keV just a selection effect ü 10 11 <B NS <10 14 G credits to Harding 7 R. Zanin 35 th ICRC, Busan 2017

2 classes of γ -ray pulsars: 50 GeV young and millisecond 100 MeV YOUNG PULSARS ü radio loudness/quiteness ü not an intrinsic 1MeV property, but a function of the viewing angle ü larger Ė than radio: 50keV just a selection effect ü 10 11 <B NS <10 14 G MILLISECOND PULSARS ü older ü ms P spun up by accretion credits to Harding from a binary companion ü 10 8 <B NS <10 11 G ü 50% of the known MSP 7 R. Zanin 35 th ICRC, Busan 2017

2 classes of γ -ray pulsars: 50 GeV young and millisecond 100 MeV YOUNG PULSARS ü radio loudness/quiteness ü not an intrinsic 1MeV property, but a function of the viewing angle ü larger Ė than radio: 50keV just a selection effect ü 10 11 <B NS <10 14 G Same variety of observables despite the MILLISECOND PULSARS differences in B, Ė ü older ü ms P spun up by accretion from a binary companion ü 10 8 <B NS <10 11 G ü 50% of the known MSP 7 R. Zanin 35 th ICRC, Busan 2017

50 GeV Luminosities More efficient after 10 4 -10 6 yr 100 MeV 1MeV 50keV Grenier+2015 Large part of the MSPs are efficient emitters magnetosphere is free-force ( η >10%) (pair production) ü large B at LC 8 R. Zanin 35 th ICRC, Busan 2017

50 GeV High-altitude emission The experimental proofs: ü atlases of lightcurves as a function of α & ζ per each model 100 MeV (Watters+2009,2010, Pierbattista+2012,2015) ü the double-peak lightcurves better fitted by high-altitude emission models 1MeV ü 50keV ü Γ =-1.5±0.2; ü E c =2.9±2.0 GeV ü b<1 à caustic outer gaps ü δ - Δ anti-correlation (Romani+1995, LAT coll. 2010, Watters+2009, 2010…) 9 R. Zanin 35 th ICRC, Busan 2017

50 GeV High-altitude emission The experimental proofs: ü atlases of lightcurves as a function of α & ζ per each model 100 MeV (Watters+2009,2010, Pierbattista+2012,2015) ü the double-peak lightcurves better fitted by high-altitude emission models 1MeV ü 50keV ü Γ =-1.5±0.2; ü E c =2.9±2.0 GeV ü b<1 à caustic outer gaps ü δ - Δ anti-correlation (Romani+1995, LAT coll. 2010, Fermi-LAT coll. 2010, Djannati-Atai 2017 Watters+2009, 2010…) 9 R. Zanin 35 th ICRC, Busan 2017

50 GeV High-altitude emission The experimental proofs: ü atlases of lightcurves as a function of α & ζ per each model 100 MeV (Watters+2009,2010, Pierbattista+2012,2015) ü the double-peak lightcurves better fitted by high-altitude emission models 1MeV ü 50keV ü Γ =-1.5±0.2; ü E c =2.9±2.0 GeV ü b<1 à caustic outer gaps ü δ - Δ anti-correlation (Romani+1995, LAT coll. 2010, Watters+2009, 2010…) 9 R. Zanin 35 th ICRC, Busan 2017

High-altitude emission, 50 GeV but … not always ü γ -ray leading the radio peak 100 MeV lightcurves require polar cap-like regions 1MeV ü too many observed high- Ė 50keV no model can account for the complete variety of lightcurves (Grenier+ 2015, Harding2016,) ü phase-resolved spectra show: ü the peak emission L γ ∞ Ė 1/2 ü the bridge emission with L γ ∞ Ė regions of both high- and low- multiplicity (Renault+2016) 10 R. Zanin 35 th ICRC, Busan 2017

50 GeV Soft γ -ray emission ü a new population? only 18! (Kuiper+2015) 100 MeV ü young: τ <50 kyr ü Ė > 4 x 10 36 erg/s ü mainly 1 broad peak LC 1MeV ü SED peaking at 10 MeV ü 7/18 are LAT PSRs 50keV 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 R. Zanin 35 th ICRC, Busan 2017

A new spectral component at 50 GeV very high energies ü the Crab pulsar shows a new spectral component up to hundreds of GeV (VERITAS coll 2011, MAGIC coll. 2011, 2012, 2014, Richards+2015) 100 MeV ü one single component above 10 GeV to TeV , ü cutoff > 700 GeV MAGIC coll. 2016 1MeV (MAGIC coll. 2016) 50keV 12 R. Zanin 35 th ICRC, Busan 2017

A new spectral component at 50 GeV very high energies ü the Crab pulsar shows a new spectral component up to hundreds 100 MeV of GeV (VERITAS coll 2011, MAGIC coll. 2011, 2012, 2014, Richards+2015) ü one single component above 10 GeV to TeV , MAGIC coll. 2016 ü harder for P2 1MeV ü cutoff > 700 GeV (MAGIC coll. 2016) 50keV ü inverse Compton radiation close/beyond the LC (Lyutikov+2012,Hirotani+2015, Petrí2012, Mochol+2015, Bogovalov +2000, Aharonian+2012) 12 R. Zanin 35 th ICRC, Busan 2017

50 GeV Flux variability in pulsars Pulsars are not steady at lower energies: ü in radio: glitches (starquakes or superfluids), giant pulses 100 MeV ü intermittent radio pulsars and transitional pulsars (Torres+2016) First switch mode in a γ -ray pulsar: J2021+4026 20% flux drop ü increase in spin 1MeV ü down rate change in the ü 50keV pulsar profile decrease energy ü cutoff (Allaford+2013, Ng+2016) Ng+2016 Pdot glitch ü a re-arrangement of the B structure à α change (Allaford+2013) 13 R. Zanin 35 th ICRC, Busan 2017

Summarizing… 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 (L γ ∞ Ė 1/2 ) 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?? 14 R. Zanin 35 th ICRC, Busan 2017