The Zoo Of Neutron Stars

1
The Zoo Of Neutron Stars

• Sergei Popov
• (SAI MSU)

(www.bradcovington.com)
JINR, Dubna, August 30, 2006
2
Main reviews

• NS basics physics/0503245
• SGRs AXPs astro-ph/040613
• Magnetars
• - Observations astro-ph/0505491
• - Theory
  astro-ph/0504077
• Central compact X-ray
• sources in supernova
• remnants astro-ph/0311526
  
• The Magnificent Seven astro-ph/0502457
• RRATs astro-ph/0511587
• Cooling of NSs astro-ph/0508056
• http//xray.sai.msu.ru/polar/sci_rev/ns.html

????? ???? ??? 72 (2003)
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Prediction ...
Neutron stars have been predicted in 30s L.D.
Landau Star-nuclei (1932) anecdote Baade
and Zwicky neutron stars and
supernovae (1934)
(Landau)
(Zwicky)
(Baade)
4
Neutron stars
Radius 10 km Mass 1-2 solar Density about the
nuclear Strong magnetic fields
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Neutron stars - 2
Superdence matter and superstrong magnetic fields
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The old zoo of neutron stars
In 60s the first X-ray sources have been
discovered. They were neutron stars in close
binary systems, BUT ... .... they were not
recognized....
Now we know hundreds of X-ray binaries with
neutron stars in the Milky Way and in other
galaxies.
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Rocket experimentsSco X-1
Giacconi, Gursky, Hendel 1962 In 2002 R.
Giacconi was awarded with the Nobel prize.
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UHURU
The satellite was launched on December 12,
1970. The program was ended in March 1973. The
other name SAS-1 2-20 keV The first full sky
survey. 339 sources.
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Accretion in close binaries
Accretion is the most powerful source of
energy realized in Nature, which can give a
huge energy output. When matter fall down onto
the surface of a neutron star up to 10 of mc2
can be released.
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Accretion disc
The theory of accretion discs was developed in
1972-73 by N.I. Shakura and R.A. Sunyaev.
Accretion is important not only in close
binaries, but also in active galactic nuclei
and many other types of astrophysical sources.
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Close binary systems
About ½ of massive stars Are members of close
binary systems.
Now we know many dozens of close binary systems
with neutron stars.

LM?c2
The accretion rate can be up to 1020
g/s Accretion efficiency up to 10 Luminosity
thousands of hundreds of the solar.
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Discovery !!!!
1967 Jocelyn Bell. Radio pulsars. Seredipitous
discovery.
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The pulsar in the Crab nebula
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Evolution of NSs. I.temperature
(Yakovlev et al. (1999) Physics Uspekhi)
more details will be described in the talk by
Prof. H. Grigorian
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Evolution of neutron stars. II. rotation
magnetic field
Ejector ? Propeller ? Accretor ? Georotator
1 spin down 2 passage through a molecular
cloud 3 magnetic field decay
astro-ph/0101031
See the book by Lipunov (1987, 1992)
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Magnetorotational evolution of radio pulsars
Spin-down. Rotational energy is released. The
exact mechanism is still unknown.
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The new zoo of neutron stars

• During last 10 years
• it became clear that neutron stars
• can be born very different.
• In particular, absolutely
• non-similar to the Crab pulsar.
• Compact central X-ray sources
• in supernova remnants.
• Anomalous X-ray pulsars
• Soft gamma repeaters
• The Magnificent Seven
• Unidentified EGRET sources
• Transient radio sources..............

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Compact central X-ray sources in supernova
remnants
RCW 103
Cas A
New result 6.7 hour period (de Luca et al. 2006)
Problem small emitting area
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Puppis A
One of the most famous central compact X-ray
sources in supernova remnants.
Age about 3700 years. Probably the progenitor
was a very massive star (mass about 30 solar).
New results Vkick1500 km/s Winkler, Petre
2006 (astro-ph/0608205)
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Magnetars

• dE/dt gt dErot/dt
• By definition The energy of the magnetic field
  is released
• P-Pdot
• Direct measurements of the field (Ibrahim et al.)

Magnetic fields 10141015 G
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Known magnetars

• AXPs
• CXO 010043.1-72
• 4U 014261
• 1E 1048.1-5937
• 1 RXS J170849-40
• XTE J1810-197
• 1E 1841-045
• AX J1844-0258
• 1E 2259586

• SGRs
• 0526-66
• 1627-41
• 1806-20
• 190014
• candidates

(??? 109)
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Magnetars on the Galaxy

• 4 SGRs, 9 AXPs, plus candidates, plus radio
  pulsars with high magnetic fields
• Young objects (about 104 year).
• Probably about 10 of all NSs.

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Historical notes

• 05 March 1979. The Konus experiment Co.
• Venera-11,12 (Mazets et al., Vedrenne et al.)
• Events in the LMC. SGR 0520-66.
• Fluence about 10-3 erg/cm2

Mazets et al. 1979
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N49 supernova remnant in the Large
Magellanic cloud (e.g. G. Vedrenne et al. 1979)
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Main types of activity of SGRs

• Weak bursts. Llt1041 erg/s
• Intermediate. L10411043 erg/s
• Giant. Llt1045 erg/s
• Hyperflares. Lgt1046 erg/s

Power distribution is similar to the distribution
of earthquakes in magnitude
See the review in Woods, Thompson astro-ph/0406133
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Normal (weak) bursts of SGRs and AXPs

• Typical bursts of SGR 1806-29,
• SGR 190014
• And of AXP 1E 2259586 detected by RXTE (from
  the review by Woods, Thompson, 2004,
  astro-ph/0406133)

(from Woods, Thompson 2004)
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Intermediate SGR bursts

• Examples of intermediate bursts.
• The forth (bottom right) is sometimes defined
  as a giant burst (for example by Mazets et al.).
  

(from Woods, Thompson 2004)
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Giant flare of the SGR 190014 (27 August 1998)

• Ulysses observations (figure from Hurley et
  al. 1999)
• Initial spike 0.35 s
• P5.16 s
• Lgt3 1044 erg/s
• ETOTALgt1044 erg

Hurley et al. 1999
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SGRs periods and giant flares
Giant flares
P, s

• 0526-66
• 1627-41
• 1806-20
• 190014

8.0
5 March 1979
(?)
18 June 1998
6.4
24 Dec 2004
7.5
5.2
27 Aug 1998
See the review in Woods, Thompson astro-ph/0406133
New result oscillations in the
tail. Trembling of the crust (Israel et al.
2005, Watts and Strohmayer 2005).
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Anomalous X-ray pulsars
Identified as a separate group in 1995.
(Mereghetti, Stella 1995 Van Paradijs et al.1995)

• Similar periods (5-10 sec)
• Constant spin down
• Absence of optical companions
• Relatively weak luminosity
• Constant luminosity

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Known AXPs
Sources Periods, s
CXO 010043.1-72 8.0
4U 014261 8.7
1E 1048.1-5937 6.4
1RXS J170749-40 11.0
XTE J1841-197 5.5
1E 1841-045 11.8
AX J1844-0258 7.0
1E 2259586 7.0
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Pulse profiles of SGRs and AXPs
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Are SGRs and AXPs brothers?

• Bursts of AXPs
• Spectral properties
• Quiescent periods of SGRs (0525-66 since 1983)

Gavriil et al. 2002
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Theory of magnetars

• Thompson, Duncan ApJ 408, 194 (1993)
• Convection in a protoNS results in generation of
  strong magnetic field
• Reconfiguration of the magnetic field structure

(Figures from the web-page of Duncan)
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Generation of the magnetic field
The mechanism of the magnetic field generation
is still unknown. Turbulent dynamo
a-O dynamo (Duncan,Thompson) a2 dynamo (Bonanno
et al.) or their combination
In any case, initial rotation of a protoNS is the
critical parameter.
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Strong field via flux conservation
There are reasons to suspect that the magnetic
fields of magnetars are not due to any kind of
dynamo mechanism, but just due to
flux conservation

• Study of SNRs with magnetars (Vink and Kuiper
  2006).
• If there was a rapidly rotating magnetar
  then a huge
• energy release is inevitable. No traces of
  such energy
• injections are found.
• There are few examples of massive stars with
  field
• strong enough to produce a magnetars due to
  flux
• conservation (Ferrario and Wickramasinghe
  2006)

Still, these suggestions can be criticized
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Alternative theory

• Remnant fallback disc
• Mereghetti, Stella 1995
• Van Paradijs et al.1995
• Alpar 2001
• Marsden et al. 2001
• Problems ..
• How to generate strong bursts?
• Discovery of a passive
• disc in one of AXPs
• (Wang et al. 2006).
• New burst of interest
• to this model.

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Magnetic field estimates

• Direct measurements of magnetic field (cyclotron
  lines)
• Spin down
• Long spin periods

Ibrahim et al. 2002
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Hyperflare of SGR 1806-20

• 27 December 2004 A giant flare from SGR 1806-20
  was detected by many satellites Swift, RHESSI,
  Konus-Wind, Coronas-F, Integral, HEND,
• 100 times brighter than any other!

Palmer et al. astro-ph/0503030
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C O R O N A S - F
Integral
RHESSI
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27 Dec 2004Giant flare SGR 1806-20

• Spike 0.2 s
• Fluence 1 erg/cm2
• E(spike)3.5 1046 erg
• L(spike)1.8 1047 erg/s
• Long tail (400 s)
• P7.65 s
• E(tail) 1.6 1044 erg
• Distance 15 kpc

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Konus observations.SGR 1806-20 27 Dec 2004
Mazets et al. 2005
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The myth about Medusa
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What is special about magnetars?
Link with massive stars There are reasons to
suspect that magnetars are connected to massive
stars. Link to binary stars There is a
hypothesis that magnetars are formed in close
binary systems (astro-ph/0505406).
Westerlund 1
The question is still on the list.
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ROSAT
ROentgen SATellite
German satellite (with participation of US and
UK).
Launched 01 June 1990. The program was
successfully ended on 12 Feb 1999.
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Close-by radio quiet NSs

• Discovery Walter et al. (1996)
• Proper motion and parallax
• Kaplan et al.
• No pulsations
• Thermal spectrum
• Later on
• six brothers

RX J1856.5-3754
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Relatives of magnetars?
The Magnificent seven
Source Period, s
RX 1856 -
RX 0720 8.39
RBS 1223 10.31
RBS 1556 -
RX 0806 11.37
RX 0420 3.45
RBS 1774 9.44
Radio quiet Close Young Thermal emission Long
periods
XDINS? RINS? ICoNS? PuTINS?
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Radio detection of the Magnificent Seven
Malofeev et al, Atel 798, 2006 1RXS
J2143.7065419 (RBS 1774)
Malofeev et al. (2005) reported detection of
1RXS J1308.6212708 (RBS 1223) in the
low-frequency band (60-110 MHz) with the radio
telescope in Pushchino.
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Unidentified EGRET sources
Grenier (2000), Gehrels et al. (2000)
Unidentified sources are divided into several
groups. One of them has sky distribution similar
to the Gould Belt objects. It is suggested that
GLAST (and, probably, AGILE) Can help to solve
this problem. Actively studied subject (see for
example papers by Harding, Gonthier)
New results no radio pulsars in 56 EGRET
error boxes (Crawford et al. 2006)
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Discovery of radio transients
McLaughlin et al. (2006) discovered a new type of
sources RRATs (Rotating Radio Transients). For
most of the sources periods about few seconds
were discovered. The result was obtained during
the Parkes survey of the Galactic plane.
These sources can be related to The Magnificent
seven.
Thermal X-rays were observed from one of the
RRATs (Reynolds et al. 2006). This one seems to
me the youngest.
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P-Pdot diagram for RRATs
McLaughlin et al. 2006 Nature
Estimates show that there should be about 400
000 Sources of this type in the Galaxy. Young
or old??? Relatives of the Magnificent
seven? (astro-ph/0603258)
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Conclusion

• There are several types of sources CCOs, M7,
• SGRs, AXPs, RRATs ...
• Magnetars (?)
• Significant fraction of all newborn NSs
• Unsolved problems
• 1. Are there links?
• 2. Reasons for diversity

53
Dorothea Rockburne
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Thats all, folks!
55
Main reviews

• NS basics physics/0503245
• SGRs AXPs astro-ph/040613
• Magnetars
• - Observations astro-ph/0505491
• - Theory
  astro-ph/0504077
• Central compact X-ray
• sources in supernova
• remnants astro-ph/0311526
  
• The Magnificent Seven astro-ph/0502457
• RRATs astro-ph/0511587
• Cooling of NSs astro-ph/0508056
• http//xray.sai.msu.ru/polar/sci_rev/ns.html

????? ???? ??? 72 (2003)