1 / 60

Isolated Neutron Stars: News and Views

Isolated Neutron Stars: News and Views. Sergei Popov (SAI MSU). Good old classics. For years two main types of NSs have been discussed: radio pulsars and accreting NSs in close binary systems. The pulsar in the Crab nebula. A binary system. The old zoo of neutron stars.

lora
Download Presentation

Isolated Neutron Stars: News and Views

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Isolated Neutron Stars:News and Views Sergei Popov (SAI MSU)

  2. Good old classics For years two main types of NSs have been discussed:radio pulsars and accreting NSs in close binary systems The pulsar in the Crab nebula A binary system

  3. The old zoo of neutron stars In 60s the first X-ray sources have been discovered.Rocket experiments. Sco X-1. They were neutron stars in close binary systems, BUT ... .... theywere «notrecognized».... Now we know hundreds of X-ray binaries with neutron stars in the Milky Way and in other galaxies.

  4. Discovery !!!! 1967: JocelynBell. Radio pulsars. Seredipitous discovery.

  5. The old Zoo: young pulsars & old accretors

  6. 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 (RRATs) • Calvera ….

  7. CCOs in SNRs Age Distance J232327.9+584843 Cas A 0.32 3.3–3.7 J085201.4−461753 G266.1−1.2 1–3 1–2 J082157.5−430017Pup A 1–3 1.6–3.3 J121000.8−522628 G296.5+10.0 3–20 1.3–3.9 J185238.6+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] Problem: small emitting area

  8. Magnetars • dE/dt > dErot/dt • By definition:The energy of the magnetic field is released Magnetic fields 1014–1015G

  9. Magnetic field estimates • Spin down • Long spin periods • Energy to support bursts • Field to confine a fireball (tails) • Duration of spikes (alfven waves) • Direct measurements of magnetic field (cyclotron lines) Ibrahim et al. 2002

  10. Spectral lines claims All claims were done for RXTE observations (there are few other candidates). All detections were done during bursts. 1E 1048.1-5937 Gavriil et al. (2002, 2004) 4U 0142+61 Gavriil et al. (2007)

  11. SGRs 0526-66 1627-41 1806-20 1900+14 0501+4516 – Aug.2008! 1801-23 (?) AXPs CXO 010043.1-72 4U 0142+61 1E 1048.1-5937 CXO J1647-45 1 RXS J170849-40 XTE J1810-197 1E 1841-045 AX J1845-0258 1E 2259+586 1E 1547.0-5408 Known magnetars (СТВ 109) http://www.physics.mcgill.ca/~pulsar/magnetar/main.html

  12. The newest SGR The most recent SGR candidate was discovered in Aug. 2008 (GCN 8112 Holland et al.) It is named SGR 0501+4516. Several reccurent bursts have been detected by several experiments (see, for example, GCN 8132 by Golenetskii et al.). Spin period 5.769 sec. Optical and IR counterparts. SWIFT P=5.7620690(1) s Pdot=7.4(1)E-12 s/s Pdotdot=-4.3(1.1)E-19 s/s^2 Israel et al. ATel #1837 (11 Nov)

  13. Extragalactic SGRs 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. 2006, 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:0712.1502andreferences therein, for example). Burst from M31 [D. Frederiks et al. astro-ph/0609544]

  14. Transient radio emission from AXP ROSAT and XMM imagesan X-ray outburst happened in 2003. AXP has spin period 5.54 s 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. (Camilo et al. astro-ph/0605429)

  15. Another AXP detected in radio 1E 1547.0-5408 P= 2 sec SNR G327.24-0.13 Pdot changed significantly on the scale of just~few months Rotation and magnetic axis seem to be aligned Also these AXP demostrated weakSGR-like bursts (Rea et al. 2008, GCN 8313) Radio [simultaneous] X-rays 0802.0494 (see also arxiv:0711.3780)

  16. Transient radiopulsar However,no radio emissiondetected. Due to beaming? PSR J1846-0258 P=0.326 sec B=5 1013 G 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-site http://hera.ph1.uni-koeln.de/~heintzma/SNR/SNR1_IV.htm 0802.1242, 0802.1704

  17. Bursts from the transient PSR Chandra: Oct 2000 June 2006 Gavriil et al. 0802.1704

  18. Are SGRs and AXPs brothers? • Bursts of AXPs (from 6 now) • Spectral properties • Quiescent periods of SGRs (0525-66 since1983) Gavriil et al. 2002

  19. Unique AXP bursts? Bursts from AXP J1810-197. Note a long exponential tail with pulsations. (Woods et al. 2005)

  20. Mysterious bursts of SWIFT J195509.6+261406 Optical bursts which is some sensesimilar to magnetars weak X-ray bursts. [Stefanescu et al. arXiv:0809.4043] See also arXiv: 0809.4231. Periodicity ~7 sec is suspected. However, in our opinion, this can benot a magnetar, but a magnetic WD.Optic vs. X-ray, longer time scales,lower energies etc. [Kaslival et al. arXiv: 0708.0226]

  21. Magnificent Seven Radioquiet (?) Close-by Thermal emission Absorption features Long periods

  22. RX J0720.4-3125 as a variable source Long term phase averagedspectrum variations Phase dependent variationsduring different observations. [Hohle et al. 2008 arXiv:0810.5319]

  23. ~10 years period: precession??? 10.711 +/-0.058 yrs [Hohle et al. 2008]

  24. 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 byHarding, 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.

  25. Discovery of RRATs • 11 sources detected in the Parkes Multibeam survey (McLaughlin et al 2006) • Burst duration 2-30 ms, interval 4 min-3 hr • Periods in the range 0.4-7 s • Period derivative measured in 3 sources: B ~ 1012-1014 G, age ~ 0.1-3 Myr • RRAT J1819-1458 detected in the X-rays, spectrum soft and thermal, kT ~ 120 eV (Reynolds et al 2006) • P, B, ages and X-ray properties of RRATs very similar to those of XDINSs • Estimated number of RRATs ~ 3-5 times that of PSRs • If τRRAT ≈ τPSR, βRRAT ≈ 3-5 βPSR • βXDINS > 3 βPSR (Popov et al 2006) • Are RRATs far away XDINSs ? New discussion about birth rates in Keane, Kramer arXiv: 0810.1512

  26. Calvera et al. Rutledge et al. reported the discovery of an enigmatic NS 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.

  27. The isolated neutron star candidate 2XMM J104608.7-594306 A new INS candidate. B >26, V >25.5, R >25 (at 2.5σ confidence level) log(FX/FV) >3.1 kT = 118 +/-15 eV unabsorbed X-ray flux: Fx~1.310−12 erg s−1 cm−2 in the 0.1–12 keV band. At 2.3 kpc (Eta Carina)the luminosity is LX~ 8.2 1032 erg s−1 R∞ ~ 5.7 km M7-like? Yes! [Pires & Motch arXiv: 0710.5192 and Pires et al., in press]

  28. Recent LIGO results 1.0805.4758Beating the spin-down limit on gravitational wave emission from the Crab pulsar h095% < 3.5 10-25 ε<1.9 10-4 (single template) 2.0708.3818All-sky search for periodic grav. waves in LIGO S4 data 50-1000 HZ No evidence. Upper limits on isolated NSs GW emission. 3.gr-qc/0702039Upper limits on gravitational wave emission from 78 PSRs ε< 10-6 for PSR J2124−3358 h<2.6×10−25 for PSRJ1603−7202

  29. NS birth rate [Keane, Kramer 2008, arXiv: 0810.1512]

  30. Too many NSs??? It seems, that the total birth rate is larger than the rate of CCSN. e- - capture SN cannot save the situation, as they are <~20%. Note, that the authors do not include CCOs. So, some estimates are wrong, or some surces evolve into another. See also astro-ph/0603258. [Keane, Kramer 2008, arXiv: 0810.1512]

  31. Pulsars, positrons, PAMELA Geminga, PSR B0656+14, and all PSRs [Dan Hooper et al. 2008 arXiv: 0810.1527] [O. Adriani et al.] arXiv:0810.4995

  32. Magnetars Pdot B=const M7 PSRs P Magnetars, field decay, heating A model based on field-dependent decay of the magnetic moment of NSscan provide an evolutionary link between different populations.

  33. Magnetic field decay Magnetic fields of NSs are expected to decay due to decay of currents which support them. Crustal field of core field? It is easy to decay in the crust. In the core the filed is in the formof superconducting vortices. They can decay only when they aremoved into the crust (during spin-down). Still, in most of models strong fields decay.

  34. Period evolution with field decay 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. astro-ph/9707318

  35. Magnetic field decay vs. thermal evolution Magnetic field decay can be an important source of NS heating. Heat is carried by electrons. It is easier to transport heat along field lines. So, poles are hotter. (for light elements envelope thesituation can be different). Ohm and Hall decay arxiv:0710.0854 (Aguilera et al.)

  36. Joule heating for everybody? 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! arXiv: 0710.4914 (Aguilera et al.)

  37. Magnetic field vs. temperature The line marks balancebetween heating due to the 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 (astro-ph/0607583)

  38. Log N – Log S with heating • Log N – Log S for 4 different magnetic fields. • No heating (<1013 G) 3. 1014 G • 5 1013 G 4. 2 1014 G Different magnetic field distributions. [Popov, Pons, work in progress; the code used in Posselt et al. A&A (2008) with modifications]

  39. Log N – Log L 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”. [Popov, Pons, work in progress]

  40. 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 are many 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?). Lx> 3 1033 erg s-1 [Muno et al. 2007]

  41. What is special about magnetars? Link withmassive stars There are reasons to suspect that magnetars are connected to massive stars (astro-ph/0611589). Recently, two massive magnetized stars have been found [Petit et al. arxiv:0803.2691] Link to binary stars There is a hypothesis that magnetars are formed in close binary systems (astro-ph/0505406). AXP in Westerlund 1 most probably hasa very massive progenitor >40 Msolar. The question is still on the list.

  42. • 5-10 % of NSs are expected to be binary (for moderate and small kicks) • All known magnetars (or candidates) are single objects. • At the moment from the statistical point of view it is not a miracle, however, it’s time to ask this question. A question: Why do all magnetars are isolated? Two possible explanations • Large kick velocities • Particular evolutionary path

  43. Magnetars origin • Probably, magnetars are isolated due to their origin • Fast rotation is necessary (Thompson, Duncan) • Two possibilities to spin-up during evolution in a binary 1) Spin-up of a progenitor star in a binary via accretion or synchronization 2) Coalescence Rem:Now there are claims (Vink et al., Ferrario et al.) that magnetars can be born slowly rotating, so the field is fossil. We do not discuss this ideas here.

  44. The code We use the “Scenario Machine” code. Developed in SAI (Moscow) since 1983 by Lipunov, Postnov, Prokhorov et al. (http://xray.sai.msu.ru/~mystery/articles/review/) We run the population synthesis of binaries to estimate the fraction of NS progenitors with enhanced rotation.

  45. The model Among all possible evolutionary paths that result in formation of NSs we select those that lead to angular momentum increase of progenitors. • Coalescence prior to a NS formation. • Roche lobe overflow by a primary without a common envelope. • Roche lobe overflow by a primary with a common envelope. • Roche lobe overflow by a secondary without a common envelope. • Roche lobe overflow by a secondary with a common envelope.

  46. Results of calculations-2 Most of “magnetars” appear after coalescences or from secondary companions after RLO by primaries. They are mostly isolated.

  47. • We made population synthesis of binary systems to derive the relative number of NSs originated from progenitors with enhanced rotation -``magnetars''. • With an inclusion of single stars (with the totalnumber equal to the total number of binaries) the fraction of ``magnetars'‘ is ~8-14%. • Most of these NSs are isolated due to coalescences of components prior to NS formation, or due to a system disruption after a SN explosion. • The fraction of ``magnetars'' in survived binaries is about 1% or lower. • The most numerous companions of ``magnetars'' are BHs. MNRAS vol. 367, p. 732 (2006)

  48. New calculations Here we study a lessoptimistic scenario,when we require thata stellar core has largeangular momentum justprior to collapse, becauseif a star is spun-up earlier,than it very probable thatit looses momentumbefore it forms a NS. Maxwellian kick [Bogomazov, Popov in press]

  49. Random kick or aligned kick Velocity distribution is adelta-function. 1 and 2 – random kick 3 and 4 – kick alogn spin1 and 3 – weak stellar wind2 and 4 – strong wind

  50. Spin-dependent kick V=V0∙ 0.001/Pmsec 1 – weak stellar wind 2 – strong wind In a more conservative scenario it is not that easyto obtain small binaryfraction.

More Related