The Zoo Of The Zoo Of Neutron StarsNeutron Stars

Sergei PopovSergei Popov((SAI MSUSAI MSU))

(www.bradcovington.com)

22

Neutron starsNeutron stars Superdense matter, strong gravity and superstrong magnetic fields

Cooling Accretion Magnetospheric activity

33

The old zoo of neutron starsThe 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 hundredsof X-ray binaries with neutron stars in the Milky Way and in other galaxies.

44

The first detections in binariesThe first detections in binariesGiacconi, Gursky, Hendel (1962)

UHURU was launched on December 12, 1970.

2-20 keV

The first sky survey.339 sources.

About ½ of massive stars are members of close binary systems.

Now we know hundreds of close binary systems with neutron stars.

55

Good old classicsGood old classics

Crab nebulaCrab nebula

A binary systemA binary system

Radio pulsars discovery

1967: Jocelyn Bell.

66

Evolution of neutron stars. I.: Evolution of neutron stars. I.: rotation + magnetic fieldrotation + magnetic fieldEjector → Propeller → Accretor → Georotator

See the book by Lipunov (1987, 1992)astro-ph/0101031

1 – spin down2 – passage through a molecular cloud3 – magnetic field decay

77

Magnetorotational evolution Magnetorotational evolution of radio pulsarsof radio pulsars

Spin-down.Rotational energy is released.The exact mechanism is still unknown.

88

Evolution of NSs. II.:Evolution of NSs. II.:temperaturetemperature

[Yakovlev et al. (1999) Physics Uspekhi]First papers on the thermal

evolution appeared already in early 60s, i.e. before the discovery of radio pulsars.

99

The old Zoo: The old Zoo: young pulsars & old accretorsyoung pulsars & old accretors

For years only two main types of NSs have been discussed:radio pulsars and accreting NSs in close binary systems

1010

During last ~10-15 years it became clear that neutron stars can be born very different.In particular, absolutely non-similar to the Crab pulsar.

o Compact central X-ray sources in supernova remnants. o Anomalous X-ray pulsarso Soft gamma repeaterso The Magnificent Seveno Unidentified EGRET sourceso Transient radio sources (RRATs)o Calvera ….

The new zoo of neutron starsThe new zoo of neutron stars

All together these NSs have total birth rate higher than normal radio pulsars(see discussion in Popov et al. 2006, Keane, Kramer 2008)

1111

Compact central X-ray sources Compact central X-ray sources in supernova remnantsin supernova remnants

Cas A RCW 103

6.7 hour period(de Luca et al. 2006)

No pulsations, small emitting area

Puppis A

Vkick=1500 km/s(Winkler, Petre 2006)

1212

CCOs in SNRsCCOs in SNRs Age DistanceJ232327.9+584843 Cas A 0.32 3.3–3.7 J085201.4−461753 G266.1−1.2 1–3 1–2J082157.5−430017 Pup A 1–3 1.6–3.3J121000.8−522628 G296.5+10.0 3–20 1.3–3.9J185238.6+004020 Kes 79 ~9 ~10 J171328.4−394955 G347.3−0.5 ~10 ~6

[Pavlov, Sanwal, Teter: astro-ph/0311526, de Luca: arxiv:0712.2209]

For two sources there are strong indications for large (>~100 msec) initial spin periods and low magnetic fields:1E 1207.4-5209 in PKS 1209-51/52 andPSR J1852+0040 in Kesteven 79 [see Halpern et al. arxiv:0705.0978]

1313

MagnetarsMagnetars dE/dt > dEdE/dt > dErotrot/dt/dt By definition:By definition: The energy of the magnetic field is releasedThe energy of the magnetic field is released P-PdotP-Pdot ““Direct” measurements of the field (spectral lines)Direct” measurements of the field (spectral lines)

Magnetic fields 1014–1015 G

1414

SGRs: periods and giant flaresSGRs: periods and giant flares

0526-660526-66 1627-411627-41 1806-201806-20 1900+141900+14 0501+450501+45

P, s Giant flares

8.06.47.55.2

5 March 1979

27 Aug 199827 Dec 2004

18 June 1998 (?)

See the review inWoods, Thompsonastro-ph/0406133and MereghettiarXiv: 0804.0250

5.7

1515

Historical notesHistorical notes 05 March 1979. The 05 March 1979. The

”Konus” experiment & Co. ”Konus” experiment & Co. Venera-11,12 Venera-11,12 Events in the LMC. Events in the LMC. SGR 0520-66.SGR 0520-66. Fluence: about 10Fluence: about 10-3-3 erg/cm erg/cm22

Mazets et al. 1979

N49 – supernovaremnant in theLarge Magellaniccloud(G.Vedrenne et al. 1979)

1616

Soft Gamma Repeaters: Soft Gamma Repeaters: main propertiesmain properties

Energetic “Giant Flares” (GFs, L ≈ 1045-1047 erg/s) detected from 3 (4?) sources

No evidence for a binary companion, association with a SNR at least in one case

Persistent X-ray emitters, L ≈ 1035 - 1036 erg/s

Pulsations discovered both in GFs tails and persistent emission, P ≈ 5 -10 s

Huge spindown rates, Ṗ ≈ 10-10 -10-11ss-1

Saturationof detectors

1717

Main types of activity of SGRsMain types of activity of SGRs Weak bursts. L<10Weak bursts. L<104242 erg/s erg/s Intermediate.Intermediate. L~10L~104242–10–104343 erg/s erg/s Giant. L<10Giant. L<104545 erg/s erg/s Hyperflares. L>10Hyperflares. L>104646 erg/s erg/s

(from Woods, Thompson 2004)

1818

Extragalactic SGRsExtragalactic SGRs

[D. Frederiks et al. astro-ph/0609544]

It was suggested long ago (Mazets et al. 1982)that present-day detectors could alredy detectgiant flares from extragalactic magnetars.

However, all searches in, for example,BATSE databse did not provide clear candidates(Lazzati et al. 2005, Popov & Stern 2006, etc.).

Finally, recently several good candidates have been proposed by different groups(Mazets et al., Frederiks et al., Golenetskii et al.,Ofek et al, Crider ...., see arxiv:0712.1502 andreferences therein, for example).

Burstin M31

1919

Anomalous X-ray pulsarsAnomalous X-ray pulsarsIdentified 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

2020

Known AXPsKnown AXPs

CXO 010043-7211CXO 010043-7211 8.08.04U 0142+614U 0142+61 8.78.71E 1048.1-59371E 1048.1-5937 6.46.41E 1547.0-54081E 1547.0-5408 2.02.0CXOU J164710-4552CXOU J164710-4552 10.610.61RXS J170849-401RXS J170849-40 11.011.0XTE J1810-197XTE J1810-197 5.55.51E 1841-0451E 1841-045 11.811.8AX J1845-0258AX J1845-0258 7.07.01E 2259+5861E 2259+586 7.07.0

Sources Periods, s

2121

SGRs and AXPsSGRs and AXPs

2222

Are SGRs and AXPs brothers?Are SGRs and AXPs brothers? Bursts of AXPsBursts of AXPs

(from 6 now) (from 6 now) Spectral propertiesSpectral properties Quiescent periods Quiescent periods

of SGRs (0525-66 of SGRs (0525-66 sincesince 1983)1983)

Gavriil et al. 2002

2323

Magnetic field estimatesMagnetic field estimates Spin downSpin down Long spin periods Long spin periods Energy to support Energy to support

burstsbursts Field to confine a Field to confine a

fireball (tails)fireball (tails) Duration of spikes Duration of spikes

(alfven waves)(alfven waves) Direct measurements Direct measurements

of magnetic field of magnetic field (cyclotron lines)(cyclotron lines)

Ibrahim et al. 2002

Gavriil et al. (2002, 2004)

2424

Transient radio emission from AXPTransient radio emission from AXP

(Camilo et al. astro-ph/0605429)

Radio emission was detected from XTE J1810-197during its active state.Clear pulsations have been detected.Large radio luminosity.Strong polarization.Precise Pdot measurement.Important for limting models, better distanceand coordinates determination etc.

ROSAT and XMM images.The X-ray outburst happened in 2003.

AXP has spin period 5.54 s

2525

Transient radiopulsarTransient radiopulsarPSR J1846-0258P=0.326 secB=5 1013 G

0802.1242, 0802.1704

Among all rotation poweredPSRs it has the largest Edot.Smallest spindown age (884 yrs).

The pulsar increased its luminosity in X-rays. Increase of pulsed X-ray flux.Magnetar-like X-ray bursts (RXTE).Timing noise.

See additional info about this pulsar at the web-sitehttp://hera.ph1.unikoeln.de/~heintzma/SNR/SNR1_IV.htm

However,no radio emissiondetected. Due to beaming?

2626

Twisted Magnetospheres – ITwisted Magnetospheres – I The magnetic field inside a The magnetic field inside a

magnetar is “wound up”magnetar is “wound up” The presence of a toroidal The presence of a toroidal

component induces a rotation of component induces a rotation of the surface layersthe surface layers

The crust tensile strength resists The crust tensile strength resists A gradual (quasi-plastic ?) A gradual (quasi-plastic ?)

deformation of the crustdeformation of the crust The external field twists up The external field twists up (Thompson, Lyutikov & Kulkarni (Thompson, Lyutikov & Kulkarni

2002)2002)

(Thompson & Duncan 2001)(Mereghetti arXiv: 0804.0250)

(by R. Turolla)

2727

Generation of the magnetic Generation of the magnetic field or fossil field?field or fossil field?

The mechanism of the magnetic field generation is still unknown. α-Ω dynamo (Duncan,Thompson) α2 dynamo (Bonanno et al.) or their combinationIn any case, initial rotation of aprotoNS is the critical parameter.

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:1. Study of SNRs with magnetars

(Vink and Kuiper 2006).2. There are few examples of massive

stars with field strong enough to produce magnetars (Ferrario and Wickramasinghe 2006)

2828

What is special about What is special about magnetarsmagnetars??

Link withLink with massive starsmassive starsThere are reasons to suspect that magnetars are connected to massive stars (astro-ph/0611589).

Link to binary starsThere is a hypothesis that magnetars are formed in close binary systems (astro-ph/0505406).The question is still on the list.

AXP in Westerlund 1 most probably hasa very massive progenitor >40 Msolar.

2929

ROSATROSATROentgen SATellite

Launched 01 June 1990. The program was successfully endedon 12 Feb 1999.

German satellite(with participation of US and UK).

3030

Close-by radioquiet NSsClose-by radioquiet NSs Discovery: Walter et al. Discovery: Walter et al.

(1996)(1996) Proper motion and Proper motion and

distance: Kaplan et al.distance: Kaplan et al. No pulsationsNo pulsations Thermal spectrumThermal spectrum Later on: six brothersLater on: six brothers

RX J1856.5-3754

3131

Magnificent SevenMagnificent SevenNameName Period, sPeriod, sRX 1856RX 1856 7.057.05RX 0720RX 0720 8.398.39RBS 1223RBS 1223 10.31 10.31

RBS 1556RBS 1556 6.88?6.88?RX 0806RX 0806 11.3711.37RX 0420RX 0420 3.453.45RBS 1774RBS 1774 9.449.44

Radioquiet (?)Close-byThermal emissionAbsorption featuresLong periods

3232

Pulsating ICoNSPulsating ICoNS

Quite large pulsed fractionsQuite large pulsed fractions Skewed lightcurvesSkewed lightcurves Harder spectrum at pulse Harder spectrum at pulse

minimumminimum Phase-dependent Phase-dependent

absorption featuresabsorption featuresRX J0420.0-5022 (Haberl et al 2004)

3333

The Optical ExcessThe Optical Excess In the four sources with a In the four sources with a

confirmed optical confirmed optical counterpart counterpart FFopt opt 5-10 x B 5-10 x B(T(TBB,XBB,X))

FFopt opt 2 2 ?? Deviations from a Rayleigh-Deviations from a Rayleigh-

Jeans continuum in RX J0720 Jeans continuum in RX J0720 (Kaplan et al 2003)(Kaplan et al 2003) and RX J1605 and RX J1605 (Motch et al 2005)(Motch et al 2005). A non-thermal . A non-thermal power law ? power law ? RX J1605 multiwavelength SED

(Motch et al 2005)

3434

Period EvolutionPeriod Evolution RX J0720.4-3125: bounds on derived by Zane RX J0720.4-3125: bounds on derived by Zane

et al. (2002) and Kaplan et al (2002)et al. (2002) and Kaplan et al (2002) Timing solution by Cropper et al (2004), further Timing solution by Cropper et al (2004), further

improved by Kaplan & Van Kerkwijk (2005): improved by Kaplan & Van Kerkwijk (2005): = 7x10= 7x10-14-14 s/s, B = 2x10 s/s, B = 2x101313 G G RX J1308.6+2127: timing solution by Kaplan & RX J1308.6+2127: timing solution by Kaplan &

Van Kerkwijk (2005a), Van Kerkwijk (2005a), = 10= 10-13-13 s/s, B = 3x10 s/s, B = 3x101313 G G Spin-down values of B in agreement with Spin-down values of B in agreement with

absorption features being proton cyclotron linesabsorption features being proton cyclotron lines

.P

.P

.P

B ~ 1013 -1014 G

3535

Featureless ? No Thanks !Featureless ? No Thanks ! RX J1856.5-3754 is convincingly featurelessRX J1856.5-3754 is convincingly featureless

(Chandra 500 ks DDT; Drake et al 2002; Burwitz et al 2003)(Chandra 500 ks DDT; Drake et al 2002; Burwitz et al 2003) A broad absorption feature detected in all A broad absorption feature detected in all

other ICoNSother ICoNS (Haberl et al 2003, 2004, 2004a; Van (Haberl et al 2003, 2004, 2004a; Van Kerkwijk et al 2004; Zane et al 2005)Kerkwijk et al 2004; Zane et al 2005)

EElineline ~ 300-700 eV; evidence for two lines ~ 300-700 eV; evidence for two lines with Ewith E1 1 ~ 2E~ 2E2 2 in RBS 1223 in RBS 1223 (Schwope et al 2006)(Schwope et al 2006)

Proton cyclotron lines ? H/He transitions at Proton cyclotron lines ? H/He transitions at high B ?high B ?

RX J0720.4-3125 (Haberl et al 2004)

3636

SourceSource Energy Energy (eV)(eV)

EWEW(eV)(eV)

BBline line (B(Bsdsd))(10(101313 G) G)

NotesNotes

RX J1856.5-3754RX J1856.5-3754 nono nono ?? --RX J0720.4-3125RX J0720.4-3125 270270 4040 5 (2)5 (2) Variable lineVariable line

RX J0806.4-4123RX J0806.4-4123 460460 3333 99 --RX J0420.0-5022RX J0420.0-5022 330330 4343 77 --RX J1308.6+2127RX J1308.6+2127 300300 150150 6 (3)6 (3) --RX J1605.3+3249RX J1605.3+3249 450450 3636 99 --

1RXS J214303.7+0654191RXS J214303.7+065419 700700 5050 1414 --

3737

Long Term Variations in Long Term Variations in RX J0720.4-3125RX J0720.4-3125

A gradual, long term A gradual, long term change in the shape of change in the shape of the X-ray spectrum the X-ray spectrum AND the pulse profile AND the pulse profile (De Vries et al 2004; Vink et al (De Vries et al 2004; Vink et al 2004) 2004)

Steady increase of TSteady increase of TBB BB and of the absorption and of the absorption feature EW (faster feature EW (faster during 2003)during 2003)

Evidence for a reversal Evidence for a reversal of the evolution in of the evolution in 2005 2005 (Vink et al 2005)(Vink et al 2005)

De Vries et al. 2004

3838

3939

Unidentified EGRET sourcesUnidentified EGRET sourcesGrenier (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)

no radio pulsars in 56 EGRET error boxes (Crawford et al. 2006) However, Keith et al. (0807.2088) found a PSR at high frequency.

4040

Discovery of RRATsDiscovery of RRATs 11 sources detected in the 11 sources detected in the Parkes Multibeam survey Parkes Multibeam survey (McLaughlin et al 2006)(McLaughlin et al 2006) Burst duration 2-30 ms, Burst duration 2-30 ms,

interval 4 min-3 hrinterval 4 min-3 hr Periods in the range 0.4-7 sPeriods in the range 0.4-7 s Period derivative measured Period derivative measured

in 3 sources: in 3 sources: B ~ 10B ~ 101212-10-101414 G, age ~ 0.1-3 Myr G, age ~ 0.1-3 Myr RRAT J1819-1458 detected in X-rays, RRAT J1819-1458 detected in X-rays,

spectrum soft and thermal, spectrum soft and thermal, kT ~ 120 eV (Reynolds et al 2006)kT ~ 120 eV (Reynolds et al 2006)

4141

RRATsRRATs P, B, ages and X-ray properties of P, B, ages and X-ray properties of

RRATs very similar to those of RRATs very similar to those of XDINSsXDINSs

Estimated number of RRATs: Estimated number of RRATs: ~ 3-5 times that of PSRs~ 3-5 times that of PSRs If If ττRRATRRAT ≈ ≈ ττPSRPSR, , ββRRATRRAT ≈ 3-5 ≈ 3-5 ββPSRPSR ββXDINS XDINS > 3 > 3 ββPSR PSR

(Popov et al 2006)(Popov et al 2006) Are RRATs far away XDINSs ?Are RRATs far away XDINSs ?

4242

RRAT in X-raysRRAT in X-rays

(arXiv: 0710.2056)

X-ray pulses overlaped onradio data of RRAT J1819-1458.

Thermally emitting NS kT ~ 120 eV(Reynolds et al 2006)

4343

Calvera et al.Calvera et al.

Recently, Rutledge et al. reported the discovery of an enigmaticNS candidated dubbed Calvera.

It can be an evolved (aged) version of Cas A source,but also it can be a M7-like object, who’s progenitor was a runaway (or, less probably, hypervelocity) star.

No radio emission was found.

4444

CCO vs. M7. New population?CCO vs. M7. New population?Gotthelf & Halpern (arXiv:0704.2255) recently suggested that 1E 1207.4-5209 and PSR J1852+0040 (in Kes 79) can beprototypes of a different subpopulation of NSs born withlow magnetic field (< few 1011 G) and relatively long spin periods (few tenths of a second).

These NSs are relatively hot, and probably not very rare.Surprisingly, we do not see objects of this type in our vicinity.In the solar neighbourhood we meet a different class of object.

This can be related to accreted envelopes (see, for example, Kaminker et al. 2006).Sources in CCOs have them, so they look hotter,but when these envelopes disappear, they are colderthan NSs which have no envelopes from the very beginning.So, we do not see such sources among close-by NSs.

4545

M7 and CCOsM7 and CCOsBoth CCOs and M7 seem to bethe hottest at their ages (103 and 106 yrs).However, the former cannot evolve to become the latter ones!

Age

Tem

pera

ture

CCOs

M7• Accreted envelopes (presented in CCOs, absent in the M7)• Heating by decaying magnetic field in the case of the M7

4646

Accreted envelopes, B or Accreted envelopes, B or heating?heating?

(Yak

ovle

v &

Peth

ick 2

004)

It is necessary to make population synthesis studies to test all these possibilities.

Related to e-capture SN? • low-mass objects• low kicks• ~10% of all NSs

However, small emitting area remains unexplained.Accretion???

4747

M7 and RRATsM7 and RRATsSimilar periods and PdotsIn one case similar thermal propertiesSimilar birth rate?

(arXiv: 0710.2056)

4848

M7 and RRATs: pro et contraM7 and RRATs: pro et contra

(Kondratiev et al, in press, see also arXiv: 0710.1648)

Based on similarities between M7 and RRATs it was proposed that they can bedifferent manifestations of the same type of INSs (astro-ph/0603258).To verify it a very deep search for radio emission (including RRAT-like bursts)was peformed on GBT (Kondratiev et al.).In addition, objects have been observed with GMRT (B.C.Joshi, M. Burgay et al.).

In both studies only upper limits were derived.Still, the zero result can be just due to unfavorable orientations(at long periods NSs have very narrow beams).It is necessary to increase statistics.

4949

M7 and high-B PSRsM7 and high-B PSRsStrong limits on radio emission from the M7are established (Kondratiev et al. 2008).However, observationally it is still possible thatthe M7 are just misaligned high-B PSRs.

Are there any other considerations to verify a link between these

two popualtions of NSs?

In most of population synthesis studies of PSRsthe magnetic field distribution is described as agaussian, so that high-B PSRs appear to be notvery numerous.On the other hand, population synthesis of thelocal population of young NSs demonstrate thatthe M7 are as numerous as normal-B PSRs.

So, for standard assumptionsit is much more probable, that

high-B PSRs and the M7 are not related.

5050

Magnetars, field decay, heatingMagnetars, field decay, heatingA model based on field-dependent decay of the magnetic moment of NSscan provide an evolutionary link between different populations.

P

Pdo

t

PSRs

M7

B=const

Magnetars

Magnetic fields of NSs are expected to decay due to decay ofcurrents which support them.

5151

Period evolution with field decayPeriod evolution with field decay

astro-ph/9707318

An evolutionary track of a NS isvery different in the case of decaying magnetic field.

The most important feature isslow-down of spin-down.Finally, a NS can nearly freezeat some value of spin period.

Several episodes of relativelyrapid field decay can happen.

Number of isolated accretors can be both decreased or increasedin different models of field decay.But in any case their average periods become shorter and temperatures lower.

5252

Magnetic field decay vs. Magnetic field decay vs. thermal evolutionthermal evolution

arxiv:0710.0854 (Aguilera et al.)

Magnetic field decay can be an important source of NS heating.

Ohm and Hall decay

Heat is carried by electrons.It is easier to transport heat along field lines. So, poles are hotter.(for light elements envelope the

situation can be different).

5353

Joule heating for everybody?Joule heating for everybody?

arXiv: 0710.4914 (Aguilera et al.)

It is important to understandthe role of heating by thefield decay for different typesof INS.

In the model by Pons et al.the effect is more importantfor NSs with larger initial B.

Note, that the characteristicage estimates (P/2 Pdot)are different in the case ofdecaying field!

5454

Magnetic field vs. temperatureMagnetic field vs. temperature

(astro-ph/0607583)

The line marks balancebetween heating due tothe field decay and cooling.It is expected by the authors(Pons et al.) that a NSevolves downwards till itreaches the line, then theevolution proceeds along the line.

Selection effects are notwell studied here.A kind of populationsynthesis modeling iswelcomed.

Teff ~ Bd1/2

5555

Log N – Log S with heatingLog N – Log S with heating

[Popov, Pons, work in progress; the code used in Posselt et al. A&A (2008) with modifications]

Log N – Log S for 4 different magnetic fields.1. No heating (<1013 G) 3. 1014 G2. 5 1013 G 4. 2 1014 G

Different magnetic field distributions.

5656

Log N – Log LLog N – Log L

[Popov, Pons, work in progress]

Two magnetic field distributions:with and without magnetars(i.e. different magnetic fielddistributions are used).6 values of inital magnetic field,8 masses of NSs.SNR 1/30 yrs-1.

“Without magnetars” means“no NSs with B0>1013 G”.

5757

Populations, new candidates ....Populations, new candidates ....Birthrate of magnetars is uncertain due to discovery of transient sources.Just from “standard” SGR statistics it is only 10%, then, for example,the M7 cannot be aged magnetars with decayed fields, but if there aremany transient AXPs and SGRs – then the situation is different.

Limits, like the one by Muno et al., on the number of AXPs from asearch for periodicity (<540) are very important and have to be improved(a task for eROSITA?).

[Muno et al. 2007]Lx> 3 1033 erg s-1

5858

ConclusionsConclusions There are several types of There are several types of

sourcessources: : CCOs, M7CCOs, M7, , SGRs, AXPs, RRATsSGRs, AXPs, RRATs ... ... Significant fraction of all Significant fraction of all

newborn NSsnewborn NSs Unsolved problemsUnsolved problems:: 1. 1. Are there linksAre there links?? 2. 2. Reasons for diversity Reasons for diversity

5959

Dorothea Rockburne

6060

Some reviews on isolated Some reviews on isolated neutron starsneutron stars

• NS basics: physics/0503245 astro-ph/0405262• SGRs & AXPs: astro-ph/0406133 arXiv:0804.0250 • CCOs: astro-ph/0311526 arxiv:0712.2209 • Quark stars: arxiv:0809.4228 • The Magnificent Seven: astro-ph/0609066 arxiv:0801.1143 • RRATs: arXiv:0710.2056 • Cooling of NSs: astro-ph/0508056 astro-ph/0402143• NS structure arXiv:0705.2708 • EoS astro-ph/0612440• NS atmospheres astro-ph/0206025 • NS magnetic fields arxiv:0711.3650 arxiv:0802.2227