The Zoo Of Neutron Stars Sergei Popov SAI

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The Zoo Of Neutron Stars Sergei Popov (SAI MSU) (www. bradcovington. com) JINR, Dubna, August 30, 2006

Main reviews • NS basics: physics/0503245 • SGRs & AXPs: astro-ph/040613 • Magnetars: - Observations - Theory astro-ph/0505491 astro-ph/0504077 • Central compact X-ray sources in supernova remnants: • The Magnificent Seven: astro-ph/0502457 • RRATs: Труды ГАИШ том 72 (2003) astro-ph/0311526 astro-ph/0511587 • Cooling of NSs: astro-ph/0508056 http: //xray. sai. msu. ru/~polar/sci_rev/ns. html 2

Prediction. . . Neutron stars have been predicted in 30 s: L. D. Landau: Star-nuclei (1932) + anecdote Baade and Zwicky: neutron stars and supernovae (1934) (Landau) (Zwicky) (Baade) 3

Neutron stars Radius: 10 km Mass: 1 -2 solar Density: about the nuclear Strong magnetic fields 4

Neutron stars - 2 Superdence matter and superstrong magnetic fields 5

The old zoo of neutron stars In 60 s 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. 6

Rocket experiments Sco X-1 Giacconi, Gursky, Hendel 1962 In 2002 R. Giacconi was awarded with the Nobel prize. 7

UHURU The satellite was launched on December 12, 1970. The program was ended in March 1973. The other name SAS-1 2 -20 ke. V The first full sky survey. 339 sources. 8

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 mc 2 can be released. 9

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. 10

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. • L=Mηc 2 The accretion rate can be up to 1020 g/s; Accretion efficiency – up to 10%; Luminosity –thousands of hundreds of the solar. 11

Discovery !!!! 1967: Jocelyn Bell. Radio pulsars. Seredipitous discovery. 12

The pulsar in the Crab nebula 13

Evolution of NSs. I. : temperature (Yakovlev et al. (1999) Physics Uspekhi) more details will be described in the talk by Prof. H. Grigorian 14

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 See the book by Lipunov (1987, 1992) astro-ph/0101031 15

Magnetorotational evolution of radio pulsars Spin-down. Rotational energy is released. The exact mechanism is still unknown. 16

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. o Compact central X-ray sources in supernova remnants. o Anomalous X-ray pulsars o Soft gamma repeaters o The Magnificent Seven o Unidentified EGRET sources o Transient radio sources. . . 17

Compact central X-ray sources in supernova remnants Cas A Problem: small emitting area RCW 103 New result: 6. 7 hour period (de Luca et al. 2006) 18

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: Vkick=1500 km/s Winkler, Petre 2006 (astro-ph/0608205) 19

Magnetars u u d. E/dt > d. Erot/dt By definition: The energy of the magnetic field is released P-Pdot Direct measurements of the field (Ibrahim et al. ) Magnetic fields 1014– 1015 G 20

Known magnetars AXPs u CXO 010043. 1 -72 u 4 U 0142+61 u 1 E 1048. 1 -5937 u 1 RXS J 170849 -40 u XTE J 1810 -197 u 1 E 1841 -045 u AX J 1844 -0258 u 1 E 2259+586 SGRs u 0526 -66 u 1627 -41 u 1806 -20 u 1900+14 u +candidates (СТВ 109) 21

Magnetars on the Galaxy 4 SGRs, 9 AXPs, plus candidates, plus radio pulsars with high magnetic fields… u Young objects (about 104 year). u Probably about 10% of all NSs. u 22

Historical notes u u u 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/cm 2 Mazets et al. 1979 23

N 49 – supernova remnant in the Large Magellanic cloud (e. g. G. Vedrenne et al. 1979) 24

Main types of activity of SGRs u Weak bursts. L<1041 erg/s u Intermediate. L=1041– 1043 erg/s u Giant. L<1045 erg/s u Hyperflares. L>1046 erg/s Power distribution is similar to the distribution of earthquakes in magnitude See the review in Woods, Thompson astro-ph/0406133 25

Normal (weak) bursts of SGRs and AXPs u Typical bursts of SGR 1806 -29, SGR 1900+14 And of AXP 1 E 2259+586 detected by RXTE (from the review by Woods, Thompson, 2004, astro-ph/0406133) (from Woods, Thompson 2004) 26

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) 27

Giant flare of the SGR 1900+14 (27 August 1998) Ulysses observations (figure from Hurley et al. 1999) u Initial spike 0. 35 s u P=5. 16 s u L>3 1044 erg/s u ETOTAL>1044 erg u Hurley et al. 1999 28

SGRs: periods and giant flares P, s Giant flares u 0526 -66 8. 0 5 March 1979 u 1627 -41 6. 4 u 1806 -20 7. 5 24 Dec 2004 u 1900+14 5. 2 27 Aug 1998 New result: oscillations in the “tail”. “Trembling” of the crust (Israel et al. 2005, Watts and Strohmayer 2005). 18 June 1998 (? ) See the review in Woods, Thompson astro-ph/0406133 29

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 30

Known AXPs Sources Periods, s CXO 010043. 1 -72 8. 0 4 U 0142+61 8. 7 1 E 1048. 1 -5937 6. 4 1 RXS J 170749 -40 11. 0 XTE J 1841 -197 5. 5 1 E 1841 -045 11. 8 AX J 1844 -0258 7. 0 1 E 2259+586 7. 0 31

Pulse profiles of SGRs and AXPs 32

Are SGRs and AXPs brothers? Bursts of AXPs u Spectral properties u Quiescent periods of SGRs (0525 -66 since 1983) u Gavriil et al. 2002 33 33

Theory of magnetars Thompson, Duncan Ap. J 408, 194 (1993) u Convection in a proto. NS results in generation of strong magnetic field u Reconfiguration of the magnetic field structure u (Figures from the web-page of Duncan) 34

Generation of the magnetic field The mechanism of the magnetic field generation is still unknown. Turbulent dynamo α-Ω dynamo (Duncan, Thompson) α 2 dynamo (Bonanno et al. ) or their combination In any case, initial rotation of a proto. NS is the critical parameter. 35

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: 1. Study of SNRs with magnetars (Vink and Kuiper 2006). 2. If there was a rapidly rotating magnetar then a huge 3. energy release is inevitable. No traces of such energy 4. injections are found. 2. There are few examples of massive stars with field 3. strong enough to produce a magnetars due to flux 4. conservation (Ferrario and Wickramasinghe 2006) Still, these suggestions can be criticized 36

u u u u 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. 37

Magnetic field estimates Direct measurements of magnetic field (cyclotron lines) u Spin down u Long spin periods u Ibrahim et al. 2002 38

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, … u 100 times brighter than any other! u Palmer et al. astro-ph/0503030 39

C O R O N A S F Integral RHESSI 40

27 Dec 2004 Giant flare SGR 1806 -20 Spike 0. 2 s u Fluence 1 erg/cm 2 u E(spike)=3. 5 1046 erg u L(spike)=1. 8 1047 erg/s u Long «tail» (400 s) u P=7. 65 s u E(tail) 1. 6 1044 erg u Distance 15 kpc u 41

Konus observations. SGR 1806 -20 27 Dec 2004 Mazets et al. 2005 42

The myth about Medusa 43

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. 44

ROSAT ROentgen SATellite German satellite (with participation of US and UK). Launched 01 June 1990. The program was successfully ended on 12 Feb 1999. 45

Close-by radio quiet NSs Discovery: Walter et al. (1996) u Proper motion and parallax: RX J 1856. 5 -3754 Kaplan et al. u No pulsations u Thermal spectrum u Later on: six brothers u 46

Relatives of magnetars? Source Period, s RX 1856 - RX 0720 The Magnificent seven 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? ICo. NS? Pu. TINS? 47

Radio detection of the Magnificent Seven Malofeev et al. (2005) reported detection of 1 RXS J 1308. 6+212708 (RBS 1223) in the low-frequency band (60110 MHz) with the radio telescope in Pushchino. Malofeev et al, Atel #798, 2006 1 RXS J 2143. 7+065419 (RBS 1774) 48

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) 49

Discovery of radio transients Mc. Laughlin 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. 50

P-Pdot diagram for RRATs Mc. Laughlin 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) 51

There are several types of sources: CCOs, M 7, Conclusion SGRs, AXPs, RRATs. . . u Magnetars (? ) u Significant fraction of all newborn NSs u Unsolved problems: 1. Are there links? 2. Reasons for diversity u 52

Dorothea Rockburne 53

That’s all, folks! 54