the magnetar primer

The Magnetar Primer

Shriharsh P. TendulkarCalifornia Institute of Technology

S. R. KulkarniP. B. Cameron

S. Tendulkar, RRI 2013 2

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


Where does everything fit?

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Magnetic Field Powered

Rotation Powered

“Accretion” Powered


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


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


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


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


Performance

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Palomar 5-m telescope

Cameron et al 2009Measurement Noise Tip-tilt Anisoplanatism


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)


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)


AXP 4U 0142+61

• Brightest AXP• d ≈ 3 kpc

• Counterpart (Hulleman et al. 2000)

• OIR pulsations (Kern & Martin 2002)

• No association13/02/13


AXP 1E 2259+586

• Center of CTB 109• d ≈ 3 kpc

• OIR counterpart (Hulleman et al. 2001)

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CTB 109


Results

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SGR 1900+14

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Galactic Rotation

Expected Progenitor Velocity

MeasuredMagnetarVelocity

Galactic Plane


SGR 1900+14

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Age = 6 kyrTC = 0.9 kyr

V = 130 km/s


SGR 1806-20

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Towards Galactic Center

V = 350 km/s


SGR 1806-20

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Tendulkar et al (2012)

Age = 650 ± 300 yrTC = 160 yr


AXP 1E 2259+586

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V = 160 km/s

Opposite to Galactic Center


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


AXP 4U 0142+61

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V = 100 km/s


AXP 4U 0142+61

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Hunt for an association



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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Matches the velocity distribution of normal pulsars (Hobbs 2005)


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

the magnetar primer

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