Magnetic fields of neutron stars G.S.Bisnovatyi-Kogan IKI RAS, Moscow and JINR, Dubna

1. Magnetic fields of neutron stars G.S.Bisnovatyi-Kogan IKI RAS, Moscow and JINR, Dubna HISS: Nuclear theory and astrophysical applications Dubna, August 2007

2. Estimations Radiopulsars, magnetars Binary X-ray sources, X-ray pulsars Recycled pulsars

3. Neutron stars are the result of collapse. Conservation of the magnetic flux B(ns)=B(s) (R /R ) B(s)=10 – 100 Gs, R ~ (3 – 10) R(Sun), R =10 km B(ns) = 4 10 – 5 10 Gs Ginzburg (1964)

4. Radiopulsars E = AB - magnetic dipole radiation (pulsar wind) E = 0.5 I I – moment of inertia of the neutron star B = IPP/4 A Single radiopulsars – timing observations (the most rapid ones are connected with young supernovae remnants) B(ns) = 2 10 – 5 10 Gs

5. Neutron star formation N.V.Ardeljan, G.S.Bisnovatyi-Kogan, S.G.Moiseenko MNRAS, 2005, 359, 333. B(chaotic) ~ 10^14 Gs High residual chaotic magnetic field after MRE core collapse SN explosion. Heat production during Ohmic damping of the chaotic magnetic field may influence NS cooling light curve

6. Inner region: development of magnetorotational instability (MRI)

7. Toy model of the MRI development: expomemtial growth of the magnetic fields at initial stages MRI leads to formation of multiple poloidal differentially rotating vortexes. Angular velocity of vortexes is growing (linearly) with a growth of H.

9. Field decay depends on the position of the electrical currents. Deep inside the currents do not decay because of a very high conductivity. et al., 1997

10. Soft Gamma Repeaters (SGR) Giant bursts in SGR similar to short GRB SGR model: MagnetarB=10^14 – 10^15 Gs Giant bursts in nearby galaxies (short GRB): 2 are observed by KONUS: M31 (Andromeda), 1February 2007 M81 3 November 2005 (statistically should be see about 10 short GRB) Jumps in dP/dt -- not seen in other pulsars Cyclotron lines: proton radiation (?)

11. Mazets et al., 1981

12. St. Peterburg, June 2005 St. Peterburg, June 2005 Mazets et al., 1981

13. Mazets et al., 1981

14. The time history of the giant burst from the soft gammarepeater SGR 1627-41. on June 18, 6153 s UT corrected for deadtime. Photon energy E > 15 keV. The rise time is about 100 ms(Mazets, 1999a).

15. The giant 1998 August 27 outburst of the soft gamma repeater SGR1900 + 14. Intensity of the E > 15 keV radiation (Mazets, 1999c).

16. The epoch folded pulse profile of SGR 1900 + 14 (2-20 keV) for the May 1998 RXTE observations(Kouveliotouet al., 1999).

17. The epoch folded pulse profile of SGR 1900 + 14 (2-20 keV) for the August 28, 1998 RXTEobservation. The plot is exhibiting two phase cycles (Kouveliotouet al., 1999).

18. The Power Density Spectrum of the May 1998 RXTE observations ofSGR 1900 + 14 . The highest peak in the spectrum corresponds tothe fundamental period of 5.159142 s; the three less intense peaksare the harmonics (Kouveliotou et al., 1999)

19. PDS of the August 28, 1998 RXTE observation. The two highest peaksare the fundamental period at 5.160199 s, and its second harmonic(Kouveliotou et al., 1999).

20. The evolution of "Period derivative" versus time since the firstperiod measurement of SGR 1900+14 with ASCA. The time is given inModified Julian Days (MJDs) (Kouveliotou et al., 1999)

21. 2004 December 27 giant outburst. Reconstructed time history of the initial pulse. Theupper part of the graph is derived from Helicon data while the lowerpart represents the Konus-Wind data. The dashed lines indicateintervals where the outburst intensity still saturates theKonus-Wind detector, but is not high enough to be seen by theHelicon. Mazets et al., 2005

22. Time history of the 2004 December 27 giant outburstrecorded by the Konus-Wind detector in three energy windows G1(16.5--65~keV), G2 (65--280~keV), and G3 (280--1060~keV), and thehardness ratio G2/G1. The moderate initial count rate growth to10^2--10^3~counts~s^{-1} transforms rapidly to anavalanche-type rise to levels >5 \times 10^7~counts~s^{-1},which drives the detector to deep saturation for a time \Delta T\simeq 0.5~s. After the initial pulse intensity has dropped to\sim 10^6~counts~s^{-1}, the detector resumes operation torecord the burst tail. P=7.57 +- 0.07 s Mazets et al., 2005

23. A spectrum of the burst tail averaged over the pulsationperiod. The low-energy component is similar to spectra of SGR'srecurrent bursts with E_0 ~30keV. At high energies itexhibits a hard power-law component with \alpha = -1.8 \pm 0.2.This two-component model is shown by the solid line. Mazets et al., 2005

24. The hystory of the outburst from SRG 1806-20 (RXTE/PCA 2-60 keV). The top panel (a) shows aq bright burst preceded by a long, complex precursor. The bottom panel (b) shows the precursor intervals used in the spectral analysis (Ibrahim et al., 2002).

25. SGR 1806-20: spectrum and best-fit continuum model for the second precursor interval with 4 absorption lines (RXTE/PCA 2-30 keV), Ibrahim et al. (2002)

28. astro-ph/0309402 First evidence of a cyclotron feature in an anomalous X-ray pulsar astro-ph/0309261 ATMOSPHERES AND SPECTRA OF STRONGLY MAGNETIZED NEUTRON STARS Wynn C. G. Ho, Dong Lai, Alexander Y. PotekhinandGilles Chabrier We find that, for the higher magnetic field models(B > BQ), vacuum polarization suppresses both the proton cyclotron line and spectral lines due to the boundspecies. As a result, the thermal spectra are almost featureless and blackbody-like. A proton RCF feature at 8.1 keV

31. et al.

32. A radio pulsar with an 8.5-second period that challenges emission models Young, M. D.; Manchester, R. N.; Johnston, S. Nature, Volume 400, Issue 6747, pp. 848-849 (1999). Radio pulsars are rotating neutron stars that emit beams of radiowaves from regions above their magnetic poles. Popular theories of the emission mechanism require continuous electron-positron pair production, with the potential responsible for accelerating the particles being inversely related to the spin period. Pair production will stop when the potential drops below a threshold, so the models predict that radio emission will cease when the period exceeds a value that depends on the magnetic field strength and configuration. Here we show that the pulsar J2144-3933, previously thought to have a period of 2.84s, actually has a period of8.51s, which is by far the longest of any known radio pulsar. Moreover, under the usual model assumptions, based on the neutron-star equations of state, this slowly rotating pulsar should not be emitting a radio beam. Therefore either the model assumptions are wrong, or current theories of radio emission must be revised.

33. Pulsar Astronomy - 2000 and Beyond, ASP Conference Series, Vol. 202; Proc. of the 177th Colloquium of the IAU held in Bonn, Germany, 30 August - 3 September 1999 Young, M. D.; Manchester, R. N.; Johnston, S. Ha, ha, ha, ha, staying alive, staying alive: A radio pulsar with an 8.5-s period challenges emission models.

34. Radiopulsars with "magnetar" properties PSR J1119-6127 has period P=0.407 s, and thelargest period derivative known among radio pulsars characteristic spin-down age of only a surface dipole magnetic field strength G The second pulsar, PSR J1814-1744, has P=3.975 s and PSR J1847-0130 a 6.7 s spin period This inferred dipolarmagnetic field strength is the highest by far among all known radio pulsars andover twice the quantum critical field above which some models predict radioemission should not occur. The inferred dipolar magnetic field strength andperiod of this pulsar are in the same range as those of the anomalous X-raypulsars, which have been identified as being magnetars whose luminous X-rayemission is powered by their large magnetic fields.

35. An upper limit on the X-ray luminosity ofJ1847-0130 is lower than the luminosities of all but one anomalous X-raypulsar. The properties of this pulsar prove that inferred dipolar magnetic fieldstrength and period cannot alone be responsible for the unusual high-energyproperties of the magnetars and create new challenges for understanding thepossible relationship between these two manifestations of young neutron stars

36. X – ray pulsars Her X-1: X ray pulsar Period of pulsations P(p)=1.24 sec,orbital P(orb)=1.7 days, P(precession)=35 days Neutron star mass 1.4 Solar masses Optical star mass about 2 Solar masses Cyclotron line corresponds to B ~ 5 10^12 Gauss (Truemper et al., 1978)

37. Inner disk radius is at R~ 20 R(star) Configuration of the inner edge of the disk and the neutron star;neutron star and the disk in the "high-on" state (left top box),and in the "low-on" state (right bottom box). Sheffer et al., 1992

38. Scott et al., 2000 Similar results have been obtained from RXTE data Sample Gingapulse profiles in five energy bands. The bands increase in energy from top to bottom: 1.0--4.6, 4.6--9.3, 9.3--14, 14--23, 23--37 keV. The bottommostpanels display a hardness ratio (9.3--23 keV band divided by 1.0--4.6 keVband). (a)---Leftmost panel set. Main High state observation on MJD 47643.Total exposure time is 8713 seconds.Main pulse occupies phase interval 0.75--1.25, and the interpulseoccupies phase interval 0.3--0.7.(b)---Center panel set. Same profiles as in (a), but with close-upof interpulse.(c)---Rightmost panel set. Short High state observation on MJD 47662,less than a day after Short High state turn-on. Total exposure time is 10118seconds. At same scale as center panel set.

39. Magnetodipole radiation of highly anisotropic relativistic electrons Comparison of the observational and computational X-ray spectra of Her X-1. The solid curve is the observational results taken fromMcCray et al. (1982), the dot curve is the approximation withT_s=0.9~ keV, T_c=8~ keV, \tau_c=14, Double peaked electron distribution at \gamma = 40, B=4 \times 10^{10} Gs. Baushev, B.-K., 1999

40. Schematic structure of the accretion column near the magnetic pole of the neutron star (top), and its radiation spectrum (bottom). Baushev, B.-K., 1999

41. Santandgelo et al., 1999 Observational spectrum of the main pulse ofthe X-ray pulsar X0115+63 in hardpart of the spectrum with harmonics, according to observation by BeppoSAX Nonequidistant lines

42. Baushev, 2002 Cyclotron harminics in magnetodipole radiation

43. X ray pulsars in LMXB: Very high frequency: P ~ 2 msec Very low magnetic fields: B ~ 10^8 Gs Give birth to millisecond recycled pulsars: NS + low mass WD

44. Recycled pulsars Her X-1: this system should give birth to the binary radiopulsar (recycled) Bisnovatyi-Kogan G.S. and Komberg B.V., 1974, Astron. Zh. 51,373 Reasons: 1. After 100 million years the optical star will become a white dwarf, mass transfer will be finished, and the system will be transparant to radio emission. 2. X ray pulsar is accelerating its rotation due to accretion, so after the birth of the white dwarf companion the neurton star will rotate rapidly, P(p) about 100 msec. Question: Why are the binary radiopulsars not found (1973) ? Answer (B-K, K, 1974): Because the magnetic field of the neutron star is decreasing about 100 times during the accretion, so binary radiopulsars are very faint objects, Pulsar luminosity L ~ B/P At small B luminosity L is low even at the rapid rotation Magnetic field is screened by the infalling plasma

45. Physics Today 1975, 28, No.11, pp. 46-54 Informal discussion at Landau Theor. Inst. Left to right: G.S.Bisnovatyi-Kogan, I.D.Novikov, Academicians V.L.Ginzburg and Ya.B.Zeldovich, and David Pines. (Photo G.Baym)

47. The properties of the first binary pulsar coinside with our predictions: Rapid rotation and Small magnetic field

48. The average magnetic fields of single radiopulsars is about 10 Gauss. 2005: New class of neutron stars: recycled pulsars, more than 100 objects discovered. All passed the stage of accreting pulsars, accelerating the rotation and decreasing the magnetic field. Ordinary pulsars Recycled pulsars P=0.033 – 8 sec P=1.5 – 50 msec B= 10 - 10 Gauss B=10 - 10 Gauss Modeling calculations of screening: Lovelace et al. (2005), and references therein. infalling of highly conducting matter versus instability, petentration of plasma into the magnetosphere.

49. NS + NS RP are the best laboratories for checking of General Relativity 1913+16 timing had shown (indirectly) the existence of gravitational waves A Double-Pulsar System — A Rare Laboratory forRelativistic Gravity and Plasma Physics (Lyne et al., 2004) The clock-like properties of pulsars moving in the gravitational fields of theirunseen neutron-star companions have allowed unique tests of general relativityand provided evidence for gravitational radiation. We report here thedetection of the 2.8-sec pulsar J0737-3039B as the companion to the 23-ms pulsar J0737-3039A in a highly-relativistic double-neutron-star system, allowingunprecedented tests of fundamental gravitational physics. We observea short eclipse of J0737-3039A by J0737-3039B and orbital modulation ofthe flux density and pulse shape of J0737-3039B, probably due to the influenceof J0737-3039A’s energy flux upon its magnetosphere. These effects willallow us to probe magneto-ionic properties of a pulsar magnetosphere.