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AXPs AXPs Anomalous X-ray Pulsars Anomalous X-ray Pulsars and SGRs SGRs and Soft Gamma Repeaters Soft Gamma Repeaters FERMI FERMI A Review in the Era A Review in the Era Launched 2008 June 11 Andreas von Kienlin Vulcano

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 1

AXPs AXPs

Anomalous X-ray Pulsars Anomalous X-ray Pulsars

and and SGRs SGRs

Soft Gamma Repeaters Soft Gamma Repeaters − − A Review in the

A Review in the

FERMI

FERMI

Era

Era

Launched 2008 June 11

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 2

The Fermi The Fermi Observatory Observatory

Gamma-ray Burst Monitor (GBM) GBM BGO detectors Large Area Telescope (LAT)

Orbit: 565 km, 25.6° whole unocculted sky at any time ! 20 % of sky

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 3

The Fermi The Fermi Observatory Observatory

NaIs (location & low-E spectrum) BGOs (mid-E spectrum) LAT (high-E spectrum)

Orbit: 565 km, 25.6° whole unocculted sky at any time ! 20 % of sky NaIs NaIs: 8 : 8 keV keV – – 1 MeV 1 MeV BGOs BGOs: 150 : 150 keV keV – – 40 MeV 40 MeV LAT: 20 MeV LAT: 20 MeV –

– >300

>300 GeV GeV

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 4

GBM Triggers

Aug 08 – Sept 09  GRBs >300  TGFs 17  SGRs ~170  Particles  Other

Other: Cyg X-1 rises, solar- flare(1x), accidentals Weekly Triggers Weekly Triggers

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 5 Andreas von Kienlin Vulcano Workshop 2010

Main properties of SGRs & AXPs

Soft Gamma Repeaters (SGRs)

  • Discovered in 1979 as transient sources of hard X-ray bursts

and giant flares (GF)

  • 8 confirmed SGRs (3 emitted a GF )
  • Persistent counterparts in X-rays and coherent pulsation found

 P: 2 - 8 s; P: ~ 10-11 s/s

Anomalous X-ray pulsars (AXPs)

  • Identified in the 90’s as a peculiar class of persistent X-ray pulsar

with no signs of binary companions

  • Rotational period of a few seconds (5 - 12 s)
  • Secular spin-down ~ 10-11 - 5 × 10-13 s/s
  • LX ~ 1034 - 1036 erg/ s >> Rotational Energy Loss
  • Soft X-ray spectrum (kT~0.5 keV) + hard tail up to 200 keV
  • 9 confirmed AXPs (3 in SNRs, 3 transients)

Venera 12 SGR 0526-66 Mazets et al., 1979

 AXPs  SGRs

  • AXPs have properties very similar to those of the “quiescent” counterparts of SGRs
  • Also AXPs emit bursts similar to SGRs (discovered with RXTE 2003)
  •  same class of sources ?

AXP 1E 2259+586 + SNR CTB 109 Einstein Observatory X-ray image

.

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 6 Andreas von Kienlin Vulcano Workshop 2010

SGRs & AXPs  Magnetars?

 Both SGRs and AXPs are well explained by the Magnetar model:

  • (Isolated) neutron stars where the main source of energy is the magnetic field
  • Highly magnetized (B ~ 1015 G), slowly rotating star (P ~ 2 - 12 s)

 Enough to power bursts and persistent X-ray emission

  • Steady dissipation of magnetic field  surface heating  persistent X-ray emission
  • NS crust fractures  short bursts
  • Magnetic field becomes unstable and undergoes a large-scale rearrangement  Giant flares

 But there are alternative models: accretion from a fall-back disk (e.g Trümper et al. 2010)  Most observed neutron stars have B = 109 - 1012 G and are powered by rotational energy, accretion, residual internal heat

  • Radio Pulsars: Powered by rotational energy (P ~ 1.5 ms - 5 s)
  • Accreting X-ray binaries: Powered by gravitational energy

Thomson & Duncan 1995

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 7

Bursts/Flares/GFs

AXP 1547- 5408

January 22, 2009 INTEGRAL SPI-ACS

Intermediate flares: Sometimes pulsating light curve Durations: t ~ 0.5 – 40 s

Fluence: ~ 1042 – 1044 erg

  • 180
  • 120
  • 60

60 120 180 240 300 360 1x10

5

1x10

6

Precursor

2005, Andreas von Kienlin (on behalf of the SPI team)

Count Rate [1/s] Time [s] after 22:30:26.539 MEZ

INTEGRAL SPI/ACS Lightcurve

60 120 180

9x10

4

Pulsating Tail

0.0 0.5 1.0

Initial Peak

2 x106

Short bursts: in the hard X-ray / soft gamma-ray energy range Durations: t ~ 0.01 – 0.5 s

Fluence: ~ 1038 – 1042 erg

Giant flares: Initial hard spike + pulsating tail (3x) Durations: t ~ 1 – 60 s Fluence: ~ 1044 – 1047 erg

SGR 1806-20 Dec27, 04 SGR 1550-5418 Oct 03, 08

P=7.65 s P=2.07s

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 8 Andreas von Kienlin Vulcano Workshop 2010

Quiescent X-ray emission

 X-ray spectra:

  • Soft X-ray emission is predominantly
  • f thermal origin (XMM)
  • Detection of persistent hard X-ray

tails by INTEGRAL

 Pulsation also seen

XMM & INTEGRAL Götz et al. 2008

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 9 Andreas von Kienlin Vulcano Workshop 2010

Magnetars Magnetars in the in the Fermi Fermi era era

 GBM Magnetar Key Project (PI: Chryssa Kouveliotou)

  • http://gammaray.nsstc.nasa.gov/gbm/science/magnetars

SGR Source Active Period Triggers Comments

J0501+4516 22 Aug – 03 Sep 08 26 Fermi/GBM New source at Perseus arm 1806-20 29 Nov 2008 1 Old source - reactivation J1550-5418 03 - 20 Oct 08 22 Jan - 24 Feb 09 22 Mar – 17 Apr 09 7 117 14 Known AXP – first time exhibiting burst active episodes J0418+5729 05 Jun 2009 2 discovered with GBM ! new source at Perseus arm 1833-0832 19 Mar 2010 discovered with Swift and RXTE – no GBM detection

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 10

SGR 0501+4516 SGR 0501+4516

 Swift triggered on 4 bursts on 22 August 2008  First bursts was also detected by Fermi/GBM  RXTE ToO program triggered ~4 hours after the first Swift trigger for 600 s

  • P = 5.7620 s was reported ~ 9 hours after the first Swift trigger!
  • P = 7.4980x10-12 and B = 2.1 x 1014 G

 CXO HRC location: RA = 05h 01m 06.756s DEC = +45d 16m 33.92s (0.1” error)  IR Counterpart with UKIRT, K~18.6 (Tanvir & Varricatt 2008)  GBM triggered on 26 events from the source – total of 56 events in ~ 3.5 days

.

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 11

SGR 0501+4516 Bursts SGR 0501+4516 Bursts

Suzaku data for 080826_136:

Integrated spectrum best fit by 2 BB: kT1 = 3.3 keV, kT2 = 15.1 keV

Enoto et al. 2009

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 12

GBM data for 080826_136 (common with: Suzaku, Konus): Integrated spectrum can be fitted by … Watts et al. 2010 Lin Lin et al. 2010

SGR 0501+4516 GBM data SGR 0501+4516 GBM data

… two BB or kT1 = 8 keV, kT2 = 18 keV … one BB + PL: kT = 11 keV, γ = -2.4

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 13

SGR 0501+4516: SGR 0501+4516: odd flare

  • dd flare lightcurve

lightcurve

First magnetar candidate PRE burst ?  PRE: Photospehric Radius Expansion  Multi-peaked flare  Very rapid drop in emission PRE in thermonuclear bursts  Luminosity reaches Eddington limit, triggering PRE  Expanding layers cool, leading to a multi-peaked light curve.  Standard candle to measure a neutron star distance

>10 keV 5-10 keV 2-5 keV Counts/s Time

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 14

SGR 0501+4516: SGR 0501+4516: odd flare

  • dd flare lightcurve

lightcurve

First magnetar candidate PRE burst ?  PRE: Photospehric Radius Expansion  Multi-peaked flare  Very rapid drop in emission  Distance and field strength known.  Predicted critical flux matches that recorded by GBM!  2 x 10-4 ergs/cm2/s  Watts et al. 2010  Emission becomes softer during the dip in the lightcurve

Watts et al. 2010

O t h e r c a n d i d a t e P R E b u r s t s b e i n g i n v e s t i g a t e d !

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 15

SGR 1550-5418 SGR 1550-5418

formerly known as AXP 1E1547.0-5408 formerly known as an ASCA CCO in G327.0-0.13

 Three bursting episodes detected with GBM:

  • Oct. 2008
  • Jan. 2009
  • Mar. & Apr. 2009

 P = 2.069s, P = 2.318 x 10-11 s/s and B = 2.2 x 1014 G  Near IR detection, Ks = 18.5±0.3  GBM triggered on 138 events from the source;

  • many more in the data

.

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 16

SGR 1550 SGR 1550– –5418 Bursting Activity 5418 Bursting Activity

von Kienlin et al. 2010 van der Horst et al. 2010

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 17

January 22, 2009 activity of AXP 1E 1547.0-5408

 More than 200 bursts detected by INTEGRAL SPI/ACS (IBAS @ ISDC)

  • Period with strongest activity: January 22, 2009
  • Uninterrupted monitoring due to highly elliptical orbit
  • Energy release of brightest bursts ~ 1043 erg (assumed distance: 10 kpc)

Detected by:  Fermi / GBM  Swift  Suzaku  Konus-Wind  RHESSI  INTEGRAL

  • SPI/ACS

Time binning: 50 ms E > 80 keV

Mereghetti et al. 2009

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 18

January 22, 2009 activity of AXP 1E 1547.0-5408

 Two bright events with pulsating tail observed at 6:48:04 UT and 8:17:29 UT

  • Two longest bursts
  • Modulated at the 2.1 s spin period
  • E ~1043erg for 10 kpc

~ 0.9 s long burst (n. 150) profile

not in phase with preceding pulses

 Dead time

  • Resolving loss (deadtime)

in each single FEE

  • Blocking loss in the VCU

by “OR”-ing of 92 FEE veto signals

dead-time limited !

150

Mereghetti et al. 2009

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 19

Jan 22, 2008 GBM observations  41 triggers  450 bursts on one day…

SGR J1550-5418: Jan 08 activity period

van der Horst et al. 2010 van der Horst et al. 2010

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 20

…even when the Earth is in the way!

SGR J1550-5418: Jan 08 activity period

van der Horst et al. 2010

INTEGRAL SPI/ACS

van der Horst et al. 2010

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 21

Fermi / GBM results Adopting a distance to the SGR

  • f 5 kpc, we estimate a total

isotropic-equivalent energy release of 1042 ergs during this activation.

SGR J1550-5418: Jan 08 activity period

van der Horst et al. 2010

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SGR J1550-5418: Jan 08 activity period – GBM first trigger

Kaneko et al. 2010

~ 150 s long enhanced persistent Emission

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 23

SGR J1550-5418: Jan 08 activity period – GBM first trigger

Kaneko et al. 2010

Clear pulsation up to ~ 110 keV seen!

50 – 100 keV

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 24

SGR J1550-5418: first Jan 08 trigger: pulse profile & pulsed fraction

Kaneko et al. 2010

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 25

SGR J1550-5418: Jan 08 activity period – first trigger

 Time Integrated Spectrum [T0 + 72 – 248 s]

  • 8 – 900 keV, time intervalls of bursts cut out

8 – 900 keV Burst Free Power law

Additional Blackbody (kT = 18 keV) : Δ Cstat = 13.5 (for 2 DOF)

Kaneko et al. 2010

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 26

SGR J1550-5418: Jan 08 activity period – first trigger

 Time resolved spectroscopy [T0 + 72 – 117, 122 – 169, 173 – 223 s]

  • 8 – 900 keV, time intervals of bursts cut out
  • Interval Ι: 74 – 117 s Power Law only (Blackbody is not needed)

8 – 900 keV Burst Free Kaneko et al. 2010

Power
Law Blackbody

FBB/FTOTAL = 26%

Ι ΙΙΙ ΙΙ

ΙΙ:
122
–169
s

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 27

ΙΙΙ:
173
–223
s Blackbody Power
Law

SGR J1550-5418: Jan 08 activity period – first trigger

 Time resolved spectroscopy [T0 + 72 – 117, 122 – 169, 173 – 223 s]

  • 8 – 900 keV, time intervals of bursts cut out
  • Interval Ι: 74 – 117 s Power Law only (Blackbody is not needed)

Kaneko et al. 2010

FBB/FTOTAL = 25%

Ι ΙΙΙ ΙΙ

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 28

Evidence for the Blackbody Component

 Temporal Properties

  • Pulsations most significant in

120 – 210 s

  • Pulse fraction peaks in 50 –

74 keV

  • Pulsations not seen above 110

keV

 Spectral Properties

  • Blackbody required in

122 – 223 s

  • Blackbody kT ~ 17 keV

(peaks at around 51 keV)

  • FBB  25%

FPWRL  75% Hot Spot

RHS ≈ 120 m 

 Assuming a hot spot of radius RHS on the neutron star surface

For D = 5 kpc, kT = 17 keV:

  • AHS ≈ 0.044 (D/5 kpc)2 km2

 RHS ≈ 120 m

  • which is the size of the magnetically-confined hot

plasma and is << 1% of the NS surface area

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 29

SGR 0418+5729 GBM detection SGR 0418+5729 GBM detection

 GBM triggered on 5 June 2009

  • 2 events
  • new source confirmed with IPN

 RXTE ToO program

  • triggered ~ 4 days after the GBM triggers

 ν = 0.1102 Hz  P = 9.0783(1) sec  ν ~ 2 x 10-14 Hz/s at 3σ and B < 1014 G  CXO location:

  • RA = 04h 18m 33.867s, Dec = +57d 32'

22.91"

 No IR

  • Ks > 21.3 (Wachter et al 2009)

 or optical counterpart detected

  • R > 24 (Ratti, Steeghs & Jonker 2009)

.

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 30

Summary

 AXPs and SGRs

  • single class of objects  Magnetars
  • highest magnetic fields observed in the Universe

(~1015 G)

  • powers bursts and persistent X-ray emission

 What did FERMI GBM add?

  • It detected one new SGR (SGR J0418+5729)
  • It helped to uncover SGR characteristics of AXP

1547.0-5408  SGR 1550-5418

  • First magnetar candidate PRE burst found
  • It was possible for the first time to see pulsation in

the persistent emission – and not only after an GF

  • Smallest hot spot ever measured for magnetar

 INTEGRAL observations

  • SGR 1550-5418 (AXP 1547.0-5408)
  • Jan 22, 2009 bursting activity
  • Two intermediate flares with pulsation detected
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  • 25. May 2010

Andreas von Kienlin Vulcano Workshop 2010 31

Magnetar Candidates

Thank you

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  • 25. May 2010

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Backup Slides

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INTEGRAL SPI

Anti Coincidence Shield (ACS)

(512 kg, 91 BGO blocks)

The ACS is also used as an

  • mni-directional GRB detector

( E > 80 keV) Provides:

  • 50 ms light curve
  • No direction information
  • No energy information

S.Mereghetti - La Thuile - Feb.2009

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 34

  • 25. May 2010

Andreas von Kienlin Vulcano Workshop 2010 34

January 22, 2009 activity of AXP 1E 1547.0-5408

 INTEGRAL SPI/ACS light curves of a few bursts

  • peak flux higher than 105 ACS counts s-1
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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 35

  • 25. May 2010

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The magnetar model

  • Fig. from R. Duncan web-page:

http://solomon.as.utexas.edu/~duncan/magnetar.html Blue: B filed lines Red: Current Orange: X-ray photons Trapped fireball

Thomson C., Duncan R., 1995, MNRAS, 275, 255

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 36

  • 25. May 2010

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Magnetar Model (Duncan & Thomson 1992 : ApJ 392 L9)

Neutrons stars with a very high field  Dominant source of free energy is the magnetic field

  • Enough to power bursts and persistent X-ray emission

 Highly magnetized (B ~ 1015 G), slowly rotating star (P ~ 5 -8 s)

e+e- plasma

 Magnetic dissipation causes neutron star crust to fracture  Fractures generate sudden shifts in the magnetospheric footpoints  This triggers the generation of Alfvén pulses  Accelerates electrons above the pair production threshold  Resulting quickly in an optically thick pair-photon plasma  Cooling of plasma generates the typical short bursts of soft γ-ray radiation

 Longer bursts are powered by magnetic reconnection and involve the entire neutron star magnetosphere

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  • 25. May 2010

Andreas von Kienlin Vulcano Workshop 2010 37

SGR & AXPs: period vs. period derivative:

 Spin periods: 5 -12 s !  Spin down age: 103 – 105 yrs

  • Spin down torque consistent with magnetic dipole braking of an

isolated neutron star with a dipole field of ∼ 1014 −1015 G

 B: 1014 – 1015 G

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  • 25. May 2010

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Short GRBs  SGR Giant Flares

 GRB 070201: A Giant Flare from a SGR in M31? (Mazets et al. 2008)

  • IPN localization from Konus-Wind, INTEGRAL (SPI-ACS) and MESSENGER

Assuming: burst occurred in M31 at 0.78 Mpc

Total fluence: (2.0 +/- 0.2) × 10-5 erg /cm2 at 0.78 Mpc  total energy: 1.5 × 1045 erg Peak flux: (1.6 +/- 0.2) × 10-2 erg /(cm2s) at 0.78 Mpc  luminosity: 1.2 × 1047 erg /s  Good agreement with observed GFs energetics

Konus-Wind light curve IPN error box

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May 25, 2010 Andreas von Kienlin Vulcano Workshop 2010 39

  • 25. May 2010

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Short GRBs  SGR Giant Flares

 GRB 070201: A Giant Flare from a SGR in M31? (Mazets et al. 2008)

  • IPN localization from Konus-Wind, INTEGRAL (SPI-ACS) and MESSENGER

Assuming: burst occurred in M31 at 0.78 Mpc

Total fluence: (2.0 +/- 0.2) × 10-5 erg /cm2 at 0.78 Mpc  total energy: 1.5 × 1045 erg Peak flux: (1.6 +/- 0.2) × 10-2 erg /(cm2s) at 0.78 Mpc  luminosity: 1.2 × 10-47 erg /s  Good agreement with observed GFs energetics

GRB 051103 & M81:  Another candidate ?