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

2 Main reviews NS basics: physics/ physics/ SGRs & AXPs: astro-ph/ Magnetars: - Observations astro-ph/ astro-ph/ Theory astro-ph/ astro-ph/ Central compact X-ray sources in supernova remnants: astro-ph/ The Magnificent Seven: astro-ph/ RRATs: astro-ph/ astro-ph/ Cooling of NSs: astro-ph/ astro-ph/ Труды ГАИШ том 72 (2003)

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

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

5 Neutron stars - 2 Superdence matter and superstrong magnetic fields

6 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.

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

8 UHURU The satellite was launched on December 12, The program was ended in March The other name SAS keV The first full sky survey. 339 sources.

9 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.

10 Accretion disc The theory of accretion discs was developed in 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.

11 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 g/s; Accretion efficiency – up to 10%; Luminosity –thousands of hundreds of the solar.

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

13 The pulsar in the Crab nebula

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

15 Evolution of neutron stars. II.: rotation + magnetic field Ejector → Propeller → Accretor → Georotator See the book by Lipunov (1987, 1992) astro-ph/ – spin down 2 – passage through a molecular cloud 3 – magnetic field decay

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

17 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

18 Compact central X-ray sources in supernova remnants Cas A RCW 103 New result: 6.7 hour period (de Luca et al. 2006) Problem: small emitting area

19 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: V kick =1500 km/s WinklerWinkler, Petre 2006 Petre (astro-ph/ )

20 Magnetars  dE/dt > dE rot /dt  By definition: The energy of the magnetic field is released  P-Pdot  Direct measurements of the field (Ibrahim et al.) Magnetic fields –10 15 G

21 Known magnetars SGRs      +candidates AXPs  CXO  4U  1E  1 RXS J  XTE J  1E  AX J  1E (СТВ 109)

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

23 Historical notes  05 March The ”Konus” experiment & Co. Venera-11,12 (Mazets et al., Vedrenne et al.) Venera-11,12 (Mazets et al., Vedrenne et al.)  Events in the LMC. SGR  Fluence: about erg/cm 2 Mazets et al. 1979

24 N49 – supernova remnant in the Large Magellanic cloud (e.g. G. Vedrenne et al. 1979)

25 Main types of activity of SGRs  Weak bursts. L<10 41 erg/s  Intermediate. L=10 41 –10 43 erg/s  Giant. L<10 45 erg/s  Hyperflares. L>10 46 erg/s See the review in Woods, Thompson astro-ph/ Power distribution is similar to the distribution of earthquakes in magnitude

26 Normal (weak) bursts of SGRs and AXPs  Typical bursts of SGR , SGR SGR And of AXP 1E detected by RXTE (from the review by Woods, Thompson, 2004, astro-ph/ ) And of AXP 1E detected by RXTE (from the review by Woods, Thompson, 2004, astro-ph/ ) (from Woods, Thompson 2004)

27 Intermediate SGR bursts Examples of intermediate bursts. Examples of intermediate bursts. The forth (bottom right) is sometimes defined as a giant burst (for example by Mazets et al.). The forth (bottom right) is sometimes defined as a giant burst (for example by Mazets et al.). (from Woods, Thompson 2004)

28 Giant flare of the SGR (27 August 1998)  Ulysses observations (figure from Hurley et al. 1999)  Initial spike 0.35 s  P=5.16 s  L> erg/s  E TOTAL >10 44 erg Hurley et al. 1999

29 SGRs: periods and giant flares     P, s Giant flares March Aug Dec June 1998 (?) See the review in Woods, Thompson astro-ph/ New result: oscillations in the “tail”. “Trembling” of the crust (Israel et al. 2005, Watts and Strohmayer 2005).

30 Anomalous X-ray pulsars Identified as a separate group in (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

31 Known AXPs CXO U E RXS J XTE J E AX J E Sources Periods, s

32 Pulse profiles of SGRs and AXPs

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

34 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)

35 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 protoNS is the critical parameter.

36 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). If there was a rapidly rotating magnetar then a huge energy release is inevitable. No traces of such energy injections are found. 2.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

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

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

39 Hyperflare of SGR  27 December 2004 A giant flare from SGR was detected by many satellites: Swift, RHESSI, Konus- Wind, Coronas-F, Integral, HEND, …  100 times brighter than any other! Palmer et al. astro-ph/

40 Integral RHESSI CORONAS-FCORONAS-F

41 27 Dec 2004 Giant flare SGR  Spike 0.2 s  Fluence 1 erg/cm 2  E(spike)= erg  L(spike)= erg/s  Long «tail» (400 s)  P=7.65 s  E(tail) erg  Distance 15 kpc

42 Konus observations. SGR Dec 2004 Mazets et al. 2005

43 The myth about Medusa

44 What is special about magnetars? Westerlund 1 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/ ). The question is still on the list.

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

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

47 Relatives of magnetars? Source Period, s Period, s RX RX RBS RBS RX RX RBS Radio quiet Close Young Thermal emission Long periods The Magnificent seven XDINS? RINS? ICoNS? PuTINS?

48 Radio detection of the Magnificent Seven Malofeev et al. (2005) reported detection of 1RXS J (RBS 1223) in the low-frequency band ( MHz) with the radio telescope in Pushchino. Malofeev et al, Atel #798, RXS J (RBS 1774)

49 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)

50 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.

51 P-Pdot diagram for RRATs McLaughlin et al Nature Estimates show that there should be about Sources of this type in the Galaxy. Young or old??? Relatives of the Magnificent seven? (astro-ph/ )

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

53 Dorothea Rockburne

54 That’s all, folks!

55 Main reviews NS basics: physics/ physics/ SGRs & AXPs: astro-ph/ Magnetars: - Observations astro-ph/ astro-ph/ Theory astro-ph/ astro-ph/ Central compact X-ray sources in supernova remnants: astro-ph/ The Magnificent Seven: astro-ph/ RRATs: astro-ph/ astro-ph/ Cooling of NSs: astro-ph/ astro-ph/ Труды ГАИШ том 72 (2003)