The Magnetar Primer
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Transcript of The Magnetar Primer
The Magnetar Primer
Shriharsh P. TendulkarCalifornia Institute of Technology
S. R. KulkarniP. B. Cameron
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The Neutron Star Household
• Pulsars (1967)• Soft Gamma Repeaters (1979)• Recycled Pulsars (MSPs etc) (1982)• Isolated Neutron Stars (1992-1996) • Anomalous X-ray Pulsars (1995)• Compact Central Objects (around 2003)• RRaTs (2006)
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Where does everything fit?
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SGRsAXPs
INSsRRaTsStandard
Issue Pulsars
MSPs
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Where does everything fit?
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Magnetic Field Powered
Rotation Powered
“Accretion” Powered
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AXPs
• Anomalous X-ray Pulsars
• LX ~ 1035-36 erg/s
• Lrot ~1032 erg/s
• No companions
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AXP 1E 2259+586 inside CTB 109
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SGRs
• Soft Gamma Repeaters
• Short bursts:– 1042 ergs/s
• Giant flares– 2-500 x 1044 ergs– -29 mag!
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What is a magnetar?
• Highly magnetized NS– B ≈ 1015 G– Young– Slowly rotating (P ≈ 5-10 s)
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What is a magnetar?
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1 2
3 4
Scientific American 2003R. Duncan
AXPSGR
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Reasons for high B
• Spin down (1979 burst)– 8 sec in 104 years
• Energetics– Variability– No baryons
• Magnetic Containment
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Magnetar vs Pulsar
• Low B field ‘magnetar’– SGR 0418+5729– B~7 x 1012 G
• Radio quiet, X-ray bright
• Unsteady pulses, ratty Pdot
• High B field pulsars– Few x 1013 G
• Radio bright, X-ray quiet
• Steady pulses, decline
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Open Questions
• Formation– B-field Dynamo vs Fossil– Progenitors:
• Mass, Spin, High B-field?– Age– Kinematics (~1000 km/s?)– SN energies
• Evolution– Lifetime
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Wider Relevance
• Neutron Star census– Millions might be floating around?– Star formation history etc.
• Fraction of short-hard GRBs (Ofek et al)– Rate of NS-NS mergers
• Energetic supernovae (Kasen & Bildsten 2010)
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Astrometry
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Why Astrometry?
• Kinematics– Comparison to other NS groups
• Ages– Model free
• Progenitors/Birth-places
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• Challenges:– Can’t work in X-rays– Very few radio/IR counterparts
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OIR Astrometry
• Hubble Space Telescope– Large FoV– Stable Distortion– Diffraction Limited
• Very precise astrometry!– ≈ 0.020 mas/yr over 7 years
(Kallivayalil et al. 2013)
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Challenges in AO astrometry
• Small FoV (10-40”)
• Anisoplanatism– Changing PSF
• Variable Performance– Atmosphere
dependent
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Optimal Astrometry
• Tip-tilt Anisoplanatism
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Sasiela 1994
Cameron et al. 2009
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Performance
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Palomar 5-m telescope
Cameron et al 2009Measurement Noise Tip-tilt Anisoplanatism
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SGR 1900+14
• Giant flare: 27th Aug 1998• d ≈ 12 kpc• OIR counterpart (Testa et al. 2008)
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40 arcsec
Cluster of Massive Stars(Vrba et al. 2000)
Turnoff mass≈ 17 M(Davies et al. 2009)
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SGR 1806-20
• Giant flare: 27th Dec 2004• d ≈ 15 kpc• OIR counterpart (Israel et al. 2005)
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Cluster of Massive Stars(Fuchs et al. 1999)
Turnoff mass≈ 50 M(Bibby et al. 2008)
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AXP 4U 0142+61
• Brightest AXP• d ≈ 3 kpc
• Counterpart (Hulleman et al. 2000)
• OIR pulsations (Kern & Martin 2002)
• No association13/02/13
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AXP 1E 2259+586
• Center of CTB 109• d ≈ 3 kpc
• OIR counterpart (Hulleman et al. 2001)
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CTB 109
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Results
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SGR 1900+14
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Galactic Rotation
Expected Progenitor Velocity
MeasuredMagnetarVelocity
Galactic Plane
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SGR 1900+14
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Age = 6 kyrTC = 0.9 kyr
V = 130 km/s
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SGR 1806-20
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Towards Galactic Center
V = 350 km/s
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SGR 1806-20
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Tendulkar et al (2012)
Age = 650 ± 300 yrTC = 160 yr
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AXP 1E 2259+586
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V = 160 km/s
Opposite to Galactic Center
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AXP 1E 2259+586
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Current Center of CTB 109
Age = 14 kyr(Sasaki et al. 2013)
Center of explosion DE
NSE
MO
LECU
LAR
CLO
UD
Tendulkar et al. in prep
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AXP 4U 0142+61
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V = 100 km/s
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AXP 4U 0142+61
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Hunt for an association
Tendulkar et al. in prep
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Magnetar Kinematics
Magnetar Vtan (km/s) Association Method Reference
AXP 1E 1810−197 212±35 – VLBI Helfand et al (2007)
AXP 1E 1547.0-5408 280±120 SNR G327.4-0.13
VLBI Deller et al (2012)
SGR 1900+14 130±30 Cluster LGSAO Tendulkar et al (2012)
SGR 1806-20 350±100 Cluster LGSAO Tendulkar et al (2012)
AXP 1E 2259+586 157±17 SNR CTB 109 LGSAO Tendulkar et al (subm)
AXP 4U 0142+61 102±26 – LGSAO Tendulkar et al (subm)
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Magnetar Kinematics
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Tendulkar et al. in prep
Matches the velocity distribution of normal pulsars (Hobbs 2005)
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The NuSTAR Magnetar
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Timeline
• 24th April ‘13 SWIFT XRT brightening– 0.11 cts/s (1.3 x 1035 ergs/s)
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Timeline
• 24th April ‘13 SWIFT XRT brightening– 0.11 cts/s (1.3 x 1035 ergs/s)
• 26th April ‘13 SWIFT BAT flare– 32 ms, 2500 cts/s
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Timeline
• 26th April ‘13 SWIFT BAT flare– 32 ms, 2500 cts/s
• 26th April ‘13 NuSTAR ToO6 hr obs
– 3.76 sec period
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Timeline
• 26th April ‘13 NuSTAR ToO6 hr obs
– 3.76 sec period
• 29th April ‘13 Chandra position– 3” away from GC (0.1 pc)
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Timeline
• 29th April ‘13 Chandra position– 3” away from GC (0.1 pc)
• 4th May ‘13 NuSTAR– 7 hrs– Pdot = 6 x 10-12 s/s– B ~ 1.5 x 1014 G
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Timeline
• 4th May ‘13 NuSTAR– 7 hrs– Pdot = 6 x 10-12 s/s– B ~ 1.5 x 1014 G
• 6th May ’13 Paper to ApJL– Kaya Mori et al.
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Implications
• Very similar to other magnetars
• Probably born in O/WR stars– 6 Myr old 40 M
• More evidence for “transient” magnetars– Link to high-B pulsars
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Astrometry
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Galactic Rotation
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• No quasars– Absolute astrometry is
challenging
• Model galactic rotation– Along line of sight– SDSS stellar density– Estimate bulk motion
• Progenitor Velocity