soft gamma repeaters kevin hurley uc berkeley space sciences laboratory soft gamma repeaters an...

SOFT GAMMA REPEATERS

Kevin Hurley

UC Berkeley

Space Sciences Laboratory

SOFT GAMMA REPEATERS AN OBSERVATIONAL REVIEW

Kevin HurleyUC BerkeleySpace Sciences [email protected]

THE SOFT GAMMA REPEATERS ARE SPORADIC SOURCES OF BURSTS

• SGRs can remain dormant for many years; during these periods, no bursting behavior is observed

• They become active and emit bursts at apparently random times

• Two common types of bursts:

– Short (100 ms, up to 1041 erg s-1)

– Giant flares (several hundred seconds, periodic emission, up to 1046 erg s-1)

BURSTING ACTIVITY OF 3 SGRs OVER 17 YEARS

1992 1996 2000 2004 2008YEAR

0

20

40

60

800

20

40

600

20

40

60

80

SGR1806-20

SGR1900+14

SGR1627-41

BU

RS

TS

PE

R 1

0 D

AY

INT

ER

VA

L

0 10 20 30 40 50 60TIME, SECONDS

0

10

20

30

40

50

60

70

80

90

CO

UN

TS

/32

ms.

ULYSSESSGR1900+1425-150 keV980530A

SINGLE, ~100 ms LONG BURST (MOST COMMON)

TWO SGR GIANT FLARES

5.16 s period

7.56 s period

50.0 100.0 150.0 200.0 250.0 300.0 350.0TIME, s.

103

104

105

CO

UN

TS

/0.5

s

SGR1900+14

AUGUST 27 1998

ULYSSES

25-150 keV

0 100 200 300 400Tim e, s

10

100

1000

10000

Co

un

ts/0

.5 s

SGR1806-20DECEMBER 27, 2004

RHESSI20-100 keV

SGR1900+14AUGUST 27 1998

ULYSSES25-150 keV

Eγ=4x1044 erg

SGR1806-20DECEMBER 27, 2005

RHESSI20-100 keV

Eγ=8x1045 erg

Three phases:

1) Fast rise (<1 ms)

2) Very intense initial spike, ~100 ms long

3) Periodic decay (~300 s)

GIANT SGR FLARES ARE SPECTACULAR!

• Occur perhaps every 30 years on a given SGR

• Second only to supernovae in intensity

• Intense (Eγ≳1046 erg at the source, 1 erg/cm2 at Earth)

• Very hard energy spectra (up to >10 MeV)

• Create transient radio nebulae

• Cause dramatic ionospheric disturbances

• Should be detectable in nearby galaxies

SHORT BURST ENERGY SPECTRA, 2-150 keV: SUM OF TWO BLACKBODIES, kT=3.4 and 9.3 keV

(SGR1900+14, Feroci et al. 2004)

BeppoSAX MECSkT=3.4 keV

BeppoSAX PDSkT=9.3 keV

R= 14 km at 10 kpc R=2 km at 10 kpc

0 100 200 300 400Time, s

10

100

1000

10000

Co

un

ts/0

.5 s

1

10

100

kT

, keV

SGR1806-20 GIANT FLARERHESSI

SPECTRAL TEMPERATURE

GIANT FLARE ENERGY SPECTRUM: 175 keV BLACKBODY, THEN 10 keV BLACKBODY

101 102 103

ENERGY, keV

10 -1

100

101

102

103

104

105

FL

UX

, ph

oto

ns

/cm

2s

ke

V

SMALL BURST

GIANT FLARE

THE SGRs ARE QUIESCENT X AND γ-RAY SOURCES

• Luminosities: 1034 – 1036 erg/s (>spin-down energy)

• This quiescent component varies slowly, and exhibits pulsations (~10-20% pulsed fraction)

QUIESCENT X-RAY SOURCE ASSOCIATED WITH SGR1806-20

ASCA, 2-10 keV INTEGRAL-IBIS, 18-60 keV10-11 erg cm-2 s-1 10-10 erg cm-2 s-1

QUIESCENT X-RAY FLUX LEVEL IS RELATED TO THE BURSTING ACTIVITY

Bursts and quiescent emission are probably both related to magnetic stresses on the surface of the neutron star

GIANT FLARE

SGR1806-20Woods et al. 2006

P and P-dot FROM QUIESCENT SOFT X-RAYS (2-10 keV)

SGR1900 (P=5.16 s, P=10-10 s/s) SGR1806 (P=7.48 s, P~10-10 s/s)

Kouveliotou et al. 1998

Woods et al. 2000Woods et al. 1999

Hurley et al. 1999

8x10-11 s/s10-10 s/s

. .

SPINDOWN IS IRREGULAR, SOMETIMES RELATED TO BURSTING ACTIVITY, SOMETIMES NOT RELATED

(Woods et al. 2002, 2006)

SGR1900+14Woods et al. 2006

GIANT FLARE

This argues against accretion as the cause of the bursts

BROADBAND QUIESCENT X-RAY SPECTRA Blackbody < 10 keV, Power Law > 20 keV

Götz et al. 2006

SGRs

AXPs

MAGNETARS COMPARED TO OTHER NS: P-P DIAGRAM

SGRs,AXPs

High BRadio

Pulsars

RadioPulsars

MillisecondRadio

Pulsars

V. Kaspi 2006

.

ESSENTIAL SGR PROPERTIES

Giant Flare?

P s

. P s/s

1-10 keV luminosity

erg/s

B, Gauss

1/2

62

.3

R8PIP3c

SGR1806-20 Dec 27 2004

7.46 ~10-10 2x1035

8x1014

SGR1900+14 Aug 27

1998 5.16 ~10-10 3x1034

2-8x1014

SGR0525-66

Mar 5 1979

8 ~7x10-11 1036 7x1014

SGR1627-41 No 2.6 1.2x10-11 1035

2x1014

SGR0501+45 No 5.8 5x10-12 1034 1014

1E1547-5408* No 2.1 2.3x10-11 1033 2.2x1014

*initially thought to be an AXP

HOSTS AND PROGENITORS

• One or two SGRs are probably in supernova remnants

• One SGR may have been ejected from its supernova remnant

• Two SGRs are probably in massive star clusters

• The SNR association implies a normal progenitor mass (~5-8 M)

• The massive cluster association implies a massive progenitor (~50M)

THE SGR-SNR CONNECTION

• SGR0525-66 is almost certainly in the N49 SNR in the LMC

• 1E1547-5408 lies within the radio SNR G327.24-0.13

• SGR0501-4516 may have been ejected from its supernova remnant

MASSIVE CLUSTER-SGR ASSOCIATIONS

SGR1900+14

• ~13 stars

• 1-10 Myr old

(Vrba et al. 2000)

SGR1806-20

• ~12 stars

• 3-5 Myr old

• SGR progenitor mass ~48M

(Fuchs et al. 1999; Bibby et al. 2008)

http://www.journals.uchicago.edu/action/showFullPopup?doi=10.1086%2F312602&id=_e2

COUNTERPARTS

• Two SGRs exhibited transient radio nebulae after giant flares

• One SGR has a persistent radio counterpart

• One SGR has a variable NIR counterpart

SGRs ARE TRANSIENT RADIO SOURCES AFTER GIANT FLARES: RADIO NEBULA CREATED BY GIANT FLARE FROM

SGR1806-20 (Taylor et al. 2005)

VLA

THIS RADIO EMISSION COMES FROM AN EXPANDING CLOUDOF RELATIVISTIC ELECTRONS ACCELERATED IN THE MAGNETOSPHERE

AND EXPELLED. BUT SGRs ARE NOT OBSERVABLE QUIESCENT RADIO SOURCES

SGR1806-20 IS INVISIBLE IN THE OPTICAL (nH~6x1022 cm-2), BUT IT IS JUST BARELY VISIBLE IN THE INFRARED

m K’ =22

Kosugi et al. 2005

This is the only optical or IR counterpart to an SGR so far

Israel et al. 2005

mKs=20

10″ 1.5″

IR FLUX IS NOT AN EXTRAPOLATION OF HIGH ENERGY QUIESCENT FLUX

• But the IR flux varies with the quiescent flux and/or with bursting activity

Israel et al. 2005

IR X-γ

ESSENTIAL SGR PROPERTIES

Radio

Counterpart

NIR

Counterpart

X-ray

Counterpart

Host Progenitor

SGR1806-20 After giant flare

(transient) Yes Yes

Massive star cluster?

48M

SGR1900+14 After giant flare

(transient) No Yes

Massive star cluster?

Massive Star?

SGR0525-66 No No Yes SNR ?

SGR1627-41 No No Yes ? ?

SGR0501+45 No Maybe Yes SNR? ?

1E1547-5408 Yes No Yes SNR ?

HOW MANY SGRs ARE THERE?

• 5 or 6 confirmed SGRs (depending on 1E1547)

• Three unconfirmed SGRs: 1801-23, 1808-20, GRB050925

• Some short GRBs could be extragalactic giant magnetar flares

• Muno et al. (2008) estimated <540 in the galaxy, based on Chandra, XMM data

CONCLUSIONS

• There is good evidence that the known SGRs are magnetars

• There is growing evidence that the members of the magnetar family (AXPs and SGRs) are very similar to one another

SGRs AND AXPs OBSERVATIONAL PROPERTIES COMPARED

SGRs AXPs

Small Bursts Frequent Rare

Giant Flares Yes No

Quiescent X-rays Yes, to >100 keV Yes, to >100 keV

Radio emission Following giant flares only

1-2 cases known, transient

Periods 5 – 8 s 2 – 11 s

Spindown .5 – 20 × 10-11 s/s 0.05 – 20 × 10-11 s/s

Hosts Massive star clusters? SNRs?

• In 1992, Duncan and Thompson, and Paczyński, independently proposed that neutron stars with large magnetic fields could explain SGR bursts and giant flares

• In 1995, Thompson and Duncan expanded their model to explain the AXPs

• Duncan and Thompson called these neutron stars magnetars

• Motivation:

– High B low opacity, so L>>LEddington is allowed

– High B neutron star magnetosphere can contain the energy of the radiating electrons in a giant flare

– High B causes rapid spindown of newly born pulsar – in the case of SGR0525, the age of the SNR is 10,000 y, and the period is 8 s

– High B is a reservoir of energy to power the quiescent emission and the bursts

MAGNETARS

• Definition: a neutron star in which the magnetic field, rather than rotation, provides the main source of free energy; the decaying field powers electromagnetic radiation (R. Duncan & C. Thompson, 1992; C. Thompson & R. Duncan, 1995, 1996)

• Note that the definition does not specify the magnetic field strength

• To explain SGRs and AXPs, however, B must be greater than the quantum critical value 4.4 x 1013 G, where the energy between electron Landau levels equals their rest mass

• Some AXPs and SGRs require B~1015 Gauss, so these magnetars have the strongest cosmic magnetic fields that we know of in the universe

ORIGIN OF THE MAGNETIC FIELD

• Unknown, but there are two hypotheses:

1. Fossil field: massive (25 M) progenitor star’s field (104 G or more) is amplified during core collapse and frozen into highly conducting compact remnant (the neutron star). Initial period of neutron star is 4-10 ms, too slow for a dynamo to operate efficiently.

2. Dynamo amplification: field is generated by convective dynamo in the proto-neutron star. Initial period is 1-3 ms.

• These hypotheses are not mutually exclusive

MAKING A MAGNETAR WITH A DYNAMO(Duncan & Thompson 1992)

• A neutron star undergoes vigorous convection in the first ~30 s after its formation

• Coupled with rapid rotation (~1 ms period), this makes the neutron star a likely site for dynamo action

• If the rotation period is less than the convective overturn time, magnetic field amplification is possible

• In principle, B ~ 3 x 1017 G can be generated (magnetic field energy should not exceed the binding energy of a neutron star, so B<5 x 1018 G)

• Differential rotation and magnetic braking quickly slow the period down to the 5-10 s range

• Magnetic diffusion and dissipation create hot spots on the neutron star surface, which cause the star to be a quiescent, periodic X-ray source

• The strong magnetic field stresses the iron surface of the star, to which it is anchored

• The surface undergoes localized cracking, shaking the field lines and creating Alfvèn waves, which accelerate electrons to ~100 keV; they radiate their energy in short (100 ms) bursts with energies 1040 – 1041 erg (magnitude 19.5 crustquake)

• There is enough energy to power bursting activity for 104 y

NEUTRON STAR

B≈1015 G

Thompson & Duncan 1995

• Localized cracking can’t relieve all the stress, which continues to build

• Over decades, the built-up stress ruptures the surface of the star profoundly – a magnitude 23.2 starquake

• Magnetic field lines annihilate, filling the magnetosphere with MeV electrons

• Initial spike in the giant flare is radiation from the entire magnetosphere (>1014 G required to contain electrons)

• Periodic component comes from the surface of the neutron star

THE STATISTICS OF SHORT SGR BURSTS ARE CONSISTENT WITH THE MAGNETAR MODEL

• Burst durations

• Distribution of the time between bursts

• Number-Intensity relation for short bursts

STATISTICS:DISTRIBUTION OF SHORT BURST DURATIONS

(Gogus et al. 2001)

LOGNORMAL LOGNORMAL

STATISTICS:DISTRIBUTION OF THE TIME BETWEEN BURSTS

RXTESGR1900

Gogus et al. 1999

LOGNORMAL

SGR1900+14Gogus et al. 1999

STATISTICS:NUMBER-INTENSITY DISTRIBUTION

Götz et al. 2006

POWER LAW

STATISTICSDISTRIBUTIONS OF SGR PROPERTIES

• Lognormal duration and waiting time distributions, and power law number-intensity distribution, are consistent with:

• Self-organized criticality (Gogus et al. 2000)

– system (neutron star crust) evolves to a critical state due to a driving force (magnetic stress)

– slight perturbation can cause a chain reaction of any size, leading to a short burst of arbitrary size (but not a giant flare)

• A set of independent relaxation systems (Palmer 1999)

– Multiple, independent sites on the neutron star accumulate energy

– Sudden releases of accumulated energy

OUTLINE

• History• SGRs

1. Bursts– X-and γ-ray time histories, giant flares, QPO’s – X-ray afterglows– energy spectra, lines2. Quiescent emission in X- and γ-rays

• AXPs• Interpretation of the data• Data at other wavelengths: radio, optical• Non-electromagnetic emissions: gravitational radiation• Magnetar locations: SNRs, massive clusters• Magnetar census• Terrestrial effects of giant flares• Extragalactic magnetars• The latest news (SGR0501, AXP 1E1547)

AXPs

• At least 4 AXPs have optical/IR counterparts

• All have an IR excess with respect to an extrapolation of their X-ray blackbody spectra

• One or two AXPs display transient, pulsed radio emission

OUTLINE

• History• SGRs



• Magnetars may be deformed during bursts and especially during giant flares

• QPOs may be evidence of this deformation

• It follows that they may be sources of gravitational radiation

LIGO LIMITS ON GRAVITATIONAL RADIATION

• Upper limit to GR from GRB070201, an SGR giant flare in M31 (Abbott et al. 2008)

• Search for GR from SGR0501 bursts is in progress

OUTLINE

• History• SGRs

1. Bursts– X-and γ-ray time histories, giant flares, QPO’s– X-ray afterglows– energy spectra, lines2. Quiescent emission in X- and γ-rays


BUT SGR1900+14 IS NOT ASSOCIATED WITH THE SNR G42.8+0.6!

If the SGR originated in the SNR, a proper motion of 110 mas/yr is implied

DeLuca et al. (2008) have set an upper limit to the proper motion using 5 years of Chandra data: < 70 mas/yr

SGR1900

AXPs

• 3 or 4 AXPs are at the geometrical centers of SNRs

• Implied proper motions are small, and these associations are considered to be likely

• 1 AXP is in the cluster Westerlund 1

OUTLINE

• History• SGRs



GIANT FLARES TURN NIGHT INTO DAY!

Inan et al. 1999

Level of the ionosphere as measured by propagation ofVLF signal from Hawaii (21.4 kHz) descends to daytimevalue, due to ionization by 3-10 keV X-rays at 30-90 km

Effect of the giant flare of 1998 August 27 from SGR1900+14

THE GIANT FLARE FROM SGR1806-20

• The most intense solar or cosmic transient ever observed

• X- and gamma-ray energy released at the source: 3x1046 erg

• Measured X- and gamma-ray flux at the top of the atmosphere: 1.4 erg/cm2

• This should be considered a lower limit to the energy released (saturation effects, limited energy ranges)

• It would require ~106 erg/cm2 absorbed by the atmosphere (a giant flare at 15 pc) to cause an effect similar to “nuclear winter” (ozone depletion, destruction of the food chain)

• To cause damage to the biosphere, SGR1806-20 would have to be about 16000 times closer, at the distance of the nearest stars

• Probability: 10-6

OUTLINE

• History• SGRs



ARE SOME SHORT GRBs ACTUALLY MAGNETAR FLARES IN NEARBY GALAXIES?

GIANT FLARE FROM SGR1806-20RHESSI DATA

•Giant flare begins with ~0.2 s long, hard spectrum spike

•The spike is followed by a pulsating tail with ~1/1000th of the energy

•Viewed from a large distance, only the initial spike would be visible

•It would resemble a short GRB

•It could be detected out to 100 Mpc

•Some short GRBs are almost certainly giant magnetar flares, but how many?

0 100 200 300 400Tim e, s

10

100

1000

10000

100000

Co

un

ts/0

.5 s

0 100 200 300 400Tim e, s

10

100

1000

10000

100000

Co

un

ts/0

.5 s 6 7 8 9 10

TIME, s

20

40

60

80

CO

UN

TS

/0.0

64

S

GRB051103 – A POSSIBLE EXTRAGALACTIC GIANT MAGNETAR FLARE FROM M81 (3.6 Mpc)

IPN ErrorEllipse

M81

M82

Swift BAT15-150 keV

(Not imaged)

Eγ=7x1046 ergFrederiks et al. 2007

GRB070201 – A POSSIBLE EXTRAGALACTIC MAGNETAR FLARE FROM M31 (780 kpc)

-400 -200 0 200 400TIME, MILLISECONDS

0

40

80

120

CO

UN

TS

/2 m

s.

KONUS-W INDGRB0702012 ms. DATA

IPN ErrorBox

M31

Eγ=1.5x1045 erg

LIGO measurements indicate that this could not have been a binary merger in M31 (Abbott et al. 2008)

Mazets et al. 2008

5 GIANT FLARE ENERGIES

Assumed distance, kpc Eγ, erg

SGR1900+14

August 27 1998

15 4x1044

SGR0525-66

March 5 1979

55 7x1044

SGR0044+42 (M31)

February 1 2007

780 (M31) 1.5x1045

SGR1806-20

December 27 2004

8.7 8x1045

SGR0952+69 (M81)

November 3 2005

3600 (M81) 7x1046

OUTLINE

• History• SGRs



INTEGRAL-IBIS IMAGE OF THE QUIESCENT EMISSION FROM SGR0501

JOINT FIT TO THE QUIESCENT SPECTRUM WITH XMM AND INTEGRAL DATA (2BB+PL)

N. Rea et al., 2009

SGR 0501+4516

PL indices of the hard tails:

0.95

3.1±0.5

1.5-1.9

0.73±0.17

1.46± 0.21

0.94±0.16

Götz et al. 2006

Rea et al. 2009

Different spectral shapes below and above 10 keV different emission mechanisms⇒

AXP 1E1547-5408: THE INTEGRAL SPI-ACS BURST ZOO

-8 -4 0 4 8 12TIME, S

4000

6000

8000

10000

12000

14000

CO

UN

TS

/50

ms

1E1547-5408JANUARY 22 2009

13838 S.

-8 -4 0 4 8 12TIME, S

4000

6000

8000

10000

12000

14000

CO

UN

TS

/50

ms

1E1547-5408JANUARY 22 2009

10016 S.

0 20 40TIME, S

0

10000

20000

30000

40000

50000

CO

UN

TS

/50

ms

1E1547-5408JANUARY 22 2009

19068 S.

0 20 40 60TIME, S

0

20000

40000

60000

80000

100000

CO

UN

TS

/50

ms

1E1547-5408JANUARY 22 2009

24456 S.

• 1E1547 was initially classified as an AXP

• But the bursts from 1E1547 are SGR-like

• Two possibilities

– 1E1547 was incorrectly classified; it’s really an SGR

– SGRs and AXPs are really the same type of object

Chandra-INTEGRAL Spectrum of 1E1547(Courtesy G.L. Israel)

OPEN QUESTIONS

• What is the number-intensity relation for giant magnetar flares?

• What is the SGR birth rate and lifetime?

• What is the progenitor magnetic field?

• What kind of supernova produces an SGR? Why can’t we detect its remnant?

• How are AXPs different from SGRs?

• Are some high-B radio pulsars actually like magnetars?

• How is the high energy tail of the quiescent component generated?

BUT…WHAT IF THEY’RE NOT MAGNETARS?

• Fallback accretion disk

• Phase transitions in strange stars

AND LOCATION

• SGR0525-66 lies in the direction of the N49 SNR in the LMC

• This association has been controversial since March 6 1979

• Important to resolve, because– it is the only unobscured SGR,

and– if the SGR is in N49, it is the only

SGR with an accurately known distance and age;

• HST measurements reveal no optical counterpart (Kaplan et al. 2001); accretion disk ruled out

• Chandra measurements indicate that the quiescent X-ray spectrum resembles that of an AXP, suggesting that the neutron star may be intermediate between and SGR and an AXP

SHOULD YOU BUY A MAGNETAR SHELTER?(WORST CASE CALCULATION)

• Say each giant flare releases 3x1046 erg

• ~106 erg/cm2 absorbed by the atmosphere (a giant flare at 15 pc) would cause an effect similar to “nuclear winter” (ozone depletion, destruction of the food chain)

• Assume magnetars are distributed uniformly throughout the disk of the galaxy (900 kpc3), and that ~10 are active at any given time

• Probability ~ 10-6

LOCATIONS OF THE FOUR KNOWN SGRS

SGR 1806-20 SGR 1900+14

SGR0525-66

N49LMC

SGR1627-41

Magnetars are young objects

MAGNETAR LOCATIONS IN THE GALAXYMAGNETAR LOCATIONS IN THE GALAXY

sMM

M

M

M

M

MM

MMMM

M

MM

M

YOU ARE HERE

M M MM MM M M MM M M M MM

MAGNETAR LOCATIONS IN THE GALAXY

⇒MAGNETARS ARE YOUNG OBJECTS

SGR1806-20 DISTANCE ESTIMATES

4 8 12 16 20DISTANCE TO SGR1806-20, kpc

Bibby et al. 2008

Figer et al. 2004

Eikenberry et al. &Corbel & Eikenberry 2004

Cameron et al. 2005

McClure-Griffiths & Gaensler 2005

Corbel et al. 1997 Mol. Clouds

HI abs.

HI abs.

LBV

LBV

Spectroscopy8.7 kpc

DUST RING AROUND SGR1900+14

• If the SGR is at the distance of the massive cluster, the August 27 1998 giant flare could have created a dust-free cavity

• The ring would be illuminated by the stars in the cluster

Wachter et al. 2008 Spitzer observation

SGR1900+14 DISTANCE ESTIMATES

0 4 8 12 16DISTANCE TO SGR1900+14, kpc

Vasisht et al. 1994

Vrba et al. 1999Supergiant stars

G42.8+0.6

13.5 kpc

NUMBER-INTENSITY RELATION FOR 5 GIANT SGR FLARES*

*not to be taken too seriously

1 0 4 4 1 0 4 5 1 0 4 6 1 0 4 7

E , e r g

0

2

4

6

N(>

E)

HOW TO ANSWER THEM

• More detailed theory

• More sensitive instruments, longer observation times

• Another 30 years of data


• December 27 2004 21:30:26 UT

• SGR1806-20 was over longitude 146.2º W, latitude +20.4º (near Hawaii)

• Detected by at least 24 spacecraft (and probably numerous military spacecraft) – most of which had no X- or gamma-ray detectors!





A FEW NUMBERS FOR COMPARISON

• Peak luminosity: 2x1047 erg/s

– Peak luminosity of all the stars in the Galaxy: 8.7x1043

• Total energy released: 3x1046 erg in ~ 1 second

– =300,000 years of the sun’s energy output

– =8x1018 times the yearly world energy consumption

– =8x1019 times the energy in the world’s nuclear arsenal

• But the dose outside the Earth’s atmosphere, 0.14 rem, was roughly equivalent to a medical X-ray


GIANT SGR FLARES ARE SPECTACULAR!

• Occur perhaps every 30 years on a given SGR

• Intense (3x1046 erg at the source, 1 erg/cm2 at Earth), ~5 minute long bursts of X- and gamma-rays with very hard energy spectra (up to several MeV at least)

• Are modulated with the neutron star periodicity

• Create transient radio nebulae, dramatic ionospheric disturbances

• Display fast oscillations which provide a clue to the structure of the neutron star

LESS WELL KNOWN SGR PROPERTIES

Name PossibleSNRAssociation

Distance,kpc

Age,kyr

MassiveStarCluster?

SGR1806-20 G10.0-0.3 6 - 15 ? Yes

SGR1900+14 G42.8+0.6 5 - 15 5 - 20 Yes

SGR0525-66 N49 55 10 No

SGR1627-41 G337.0-0.1 6-11 1-5 No


• December 27 2004 21:30:26 UT

• SGR1806-20 was over longitude 146.2º W, latitude +20.4º (near Hawaii)

• Detected by at least 24 spacecraft (and probably numerous military spacecraft) – most of which had no X- or gamma-ray detectors!





A FEW NUMBERS FOR COMPARISON

• Peak luminosity: 2x1047 erg/s

– Peak luminosity of all the stars in the Galaxy: 8.7x1043

• Total energy released: 3x1046 erg in ~ 1 second

– =300,000 years of the sun’s energy output

– =8x1018 times the yearly world energy consumption

– =8x1019 times the energy in the world’s nuclear arsenal

• But the dose outside the Earth’s atmosphere, 0.14 rem, was roughly equivalent to a medical X-ray


IS SGR1900+14 ASSOCIATED WITH A HISTORICAL SUPERNOVA? (Wang, Li, and Zhao 2002)

• “During the 3rd month of the 3rd year of Jian-Ping in the period of the king of Han Ai (4 BC, April), a po star was seen near He-Gu”

• Similar description is found in Korean records

• “po” star had m~5

• In this direction, m=5 corresponds to M=-21; possibly a hypernova

R. Mallozzi, 1998

• On August 22, 2008, SGR0501+4516 awoke from a long sleep and became burst-active

• The first detection was by the Swift BAT

• This was the first new SGR to be confirmed in 10 years

• Many ToO observations were called (AGILE, Chandra, INTEGRAL, RXTE, Suzaku, Swift, XMM)

• We activated our INTEGRAL AO-6 ToO program on August 27, and observed the source for about 200 ksec

• We detected the quiescent emission, and four weak bursts

22-A

ug

-08

23-A

ug

-08

24-A

ug

-08

25-A

ug

-08

26-A

ug

-08

27-A

ug

-08

28-A

ug

-08

29-A

ug

-08

30-A

ug

-08

31-A

ug

-08

1-S

ep-0

82-

Sep

-08

3-S

ep-0

8

0

10

20

30

OB

SE

RV

ED

BU

RS

TS

PE

R D

AY

*

SUZAKUXMM

XRTXRT

INTEGRAL

CHANDRAXTE

*OBSERVATIONS BY KONUS-W IND, RHESSI, INTEGRAL-IBIS, SW IFT, SUZAKU XIS, AGILE,

AND FERMI GBM

SGR0501+4516

ToO OBSERVATIONS

TIMELINES OF BURSTING ACTIVITY AND TOO OBSERVATIONS

August 27 2008 16:25

20-40 keV

40-100 keV

100-300 keV

BURST #1

CO

UN

TS

/50

ms

20-40 keV

40-100 keV

100-300 keV

August 27 2008 22:26

BURST #2

CO

UN

TS

/50

ms

20-40 keV

40-100 keV

100-300 keV

August 28 2008 03:32

BURST #3

CO

UN

TS

/50

ms

20-40 keV

40-100 keV

100-300 keV

August 28 2008 20:59

BURST #4

CO

UN

TS

/50

ms

BURST PARAMETERS

Duration,

ms

Fluence,

erg cm-2

Peak flux,

erg cm-2 s-1 (50 ms)

kT, keV

(OTTB)

August 27 16:25 150 6.6x10-9 4.8x10-8 ---

August 27 22:25 200 4.8x10-8 8.4x10-8 ---

August 28 03:32 200 3x10-8 1.4x10-7 28

August 28 20:59 50 2x10-8 3x10-7 33

These bursts are very weak; spectraare typical for SGR bursts

Spectrum of August 28 20:59 burst

OTTB fitkT=33 keV

SUMMARY

• INTEGRAL-IBIS ToO observation of SGR0501+4516 was successful

• 4 weak bursts were detected. The spectra of two of them were typical of SGR bursts; the other two were too weak for analysis

• Quiescent emission was detected up to 100 keV; flux was 4x10-11 erg cm-2 s-1, 18-100 keV, a typical number for SGRs

• XMM/INTEGRAL spectrum indicates a rising νFν spectrum above 10 keV with a hard power law, which is fairly typical of magnetars

“STRANGE” BURSTS, 1000 TIMES LONGER (RARE)

5 6 7 8 9 10 11 12 13 14 15TIME, SECONDS

0

10

20

30

40

50

60

70

80

90

100

110

CO

UN

TS

/32

ms

ULYSSESSGR1627-41JULY 2, 200125-150 keV

INTERMEDIATE DURATION BURSTS (RARE)

INTERMEDIATE BURST ENERGY SPECTRUM:SUM OF TWO BLACKBODIES, kT=4.3 and 9.8 keV

(SGR1900+14, Olive et al. 2004)

HETE WXM HETE FREGATE

NO GLITCH AT THE TIME OF THE SGR1806-20 GIANT FLARE

HOW MANY ARE THERE?

• When they burst normally in gamma-rays, they are bright enough to detect anywhere in the galaxy

• When they don’t, you can detect them as quiescent X-ray sources, but you have to know exactly where to look

• Long periods (decades) with no bursts possible hidden galactic SGRs

• Muno et al. (2008) estimated <540 based on Chandra, XMM data

soft gamma repeaters kevin hurley uc berkeley space sciences laboratory soft gamma repeaters an...

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