The decaying magneticfield of magnetars

Transcription

1 November 25th 2013 SFB/TR7 Video Seminar The decaying magneticfield of magnetars SIMONE DALL'OSSO Theoretical Astrophysics - University of Tübingen

2 Motivations - X-ray emission of magnetars powered by decay of superstrong magnetic field a) eventually test this hypothesis b) best objects to study B-decay - Magnetar-like emission from unsuspected magnetars (SGR Rea et al. 2010) Additional degree of freedom besides dipole field? - Link between different classes of high-b NSs (SGRs, AXPs, transient AXPs/SGRs, XDINs,...) Dall'Osso, Granot & Piran (2012), MNRAS 422, 2878

3

4 Recent population studies Galactic scale height Olausen & Kaspi 2013

5 Recent population studies Galactic scale height Olausen & Kaspi 2013

6 Pulsars: back to basics Magnetic dipole spindown 2 d ω = K B ω 3 Characteristic (spindown) age ω τ c= 2 ω 19 1/2 B d ( P P ) G

7 Pulsars: back to basics Magnetic dipole spindown 2 d ω = K B ω 3 Log P B=const Log P

8 Pulsars: back to basics Magnetic dipole spindown 2 d ω = K B ω 3 Log P B=const Log P

9 Pulsars: back to basics Magnetic dipole spindown 2 d ω = K B ω 3 Log P B=const τ=const Log P

10 Pulsars: back to basics Magnetic dipole spindown 2 d ω = K B ω 3 Log P B=const τ=const Log P

11 Pulsars: back to basics Magnetic dipole spindown 2 d ω = K B ω 3 SGR 0418 io d Ra th a e d r sl a pu lin e

12 Pulsars: back to basics Magnetic dipole spindown 2 d ω = K B ω 3 SGR 0418 io d Ra th a e d r sl a pu lin e

13 Source classes AXPs/SGRs: Kuiper et al. (2006), INTEGRAL Figure credits: Mereghetti 2008 persistent X-ray emission >> d/dt(erot) Thermal kt=( ) kev hard-x spectral tails (up to 150 kev) Bursts&Flares (ms min) - No radio

14 Source classes AXPs/SGRs: persistent X-ray emission >> d/dt(erot) Thermal kt=( ) kev hard-x spectral tails (up to 150 kev) Bursts&Flares (ms min) - No radio Figures: Woods (2003) Israel et al. (2008)

15 Source classes AXPs/SGRs: persistent X-ray emission >> d/dt(erot) Thermal kt=( ) kev hard-x spectral tails (up to 150 kev) Bursts&Flares (ms min) - No radio Transients: Quiescence : X-ray Lum. d/dt(erot) Thermal kt =( ) kev + A << ANS Outburst : X-ray Lum. >> d/dt(erot) decays on ~ yrs timescale

16 Source classes AXPs/SGRs: persistent X-ray emission >> d/dt(erot) Thermal kt=( ) kev hard-x spectral tails (up to 150 kev) Bursts&Flares (ms min) - No radio Transients: Quiescence : X-ray Lum. d/dt(erot) Thermal kt =( ) kev + A << ANS Outburst: X-ray Lum. >> d/dt(erot) decays on ~ yrs timescale Figure: Bernardini et al. (2009)

17 Source classes AXPs/SGRs: persistent X-ray emission >> d/dt(erot) Thermal kt=( ) kev hard-x spectral tails (up to 150 kev) Bursts&Flares (ms min) - No radio Transients: Quiescence : X-ray Lum. d/dt(erot) Thermal kt =( ) kev + A << ANS Outburst: X-ray Lum. >> d/dt(erot) decays on ~ yrs timescale Figure: Rea et al. 2012

18 Source classes AXPs/SGRs: persistent X-ray emission >> d/dt(erot) Thermal kt=( ) kev hard-x spectral tails (up to 150 kev) Bursts&Flares (ms min) - No radio Transients: Quiescence : X-ray Lum. d/dt(erot) Thermal kt =( ) kev + A << ANS Outburst: X-ray Lum. >> d/dt(erot) decays on ~ yrs timescale X-ray Dim Isolated NSs: prototypical isolated NSs. Nearly perfect thermal spectra Stable X-rays kt = ( ) kev

19 Pulsars: back to basics Magnetic dipole spindown 2 d ω = K B ω 3 SGR 0418 io d Ra th a e d r sl a pu lin e

20 Pulsars: back to basics Magnetic dipole spindown 2 d ω = K B ω 3 Bd ~ Bd/τd τd ~ B - α SGR 0418 io d Ra th a e d r sl a pu lin e

21 Pulsars: back to basics Magnetic dipole spindown 2 d ω = K B ω 3 α<2 Produces asymtptotic spin (cf. Colpi et al. 2000) SGR 0418 io d Ra th a e d r sl a pu lin e

22 Pulsars: back to basics Magnetic dipole spindown 2 d ω = K B ω 3 α<2 Produces asymtptotic spin (cf. Colpi et al. 2000) SGR 0418 io d Ra th a e d r sl a pu lin e

23 B Radio Pulsars D ea th Li ne τ

24 B 1013G Radio Pulsars D ea th Li ne τ

25 B BMAX P 1013G ma x Radio Pulsars D ea th P~ Li ne 5s τ

26 A physical perspective r lsa Pu s e lin 11 h at de P= (Dall'Osso, Granot & Piran 2012)

27 A physical perspective r lsa Pu No high-b with old spindown age s e lin 11 h at de P= No source here (Dall'Osso, Granot & Piran 2012) A limit period exists P ~ 11 s

28 A physical perspective r lsa Pu No high-b with old spindown age s e lin 11 h at de P= No source here A limit period exists P ~ 11 s Bd ~ Bd/τd τd ~ B -α (Dall'Osso, Granot & Piran 2012)

29 Dipole Field Decay: parametric model τd ~ B-1 τc tage

30 Dipole Field Decay: parametric model

31 Main modes of dipole field decay Goldreich & Reisenegger 1992

32 Main modes of dipole field decay Goldreich & Reisenegger 1992

33 Main modes of dipole field decay Goldreich & Reisenegger 1992

34 Main modes of dipole field decay OHMIC DECAY AMBIPOLAR DIFFUSION HALL DRIFT Goldreich & Reisenegger 1992

35 Main modes of dipole field decay Hall decay of crustal field is the > G τd,h ~ 104 yrs (ρ14/b15 ) (Cumming et al. 2004, Goldreich & Reisenegger 1992)

36 Main modes of dipole field decay Hall decay of crustal field is the > G τd,h ~ 104 yrs (ρ14/b15 ) (Cumming et al. 2004, Goldreich & Reisenegger 1992)

37 Main modes of dipole field decay Hall decay of crustal field is the > G τd,h ~ 104 yrs (ρ14/b15 ) (Cumming et al. 2004, Goldreich & Reisenegger 1992) B-independent ohmic decay in the crust exponential +ohmic diffusion to deep layers power-law in time: τd,i ~ 104 yrs ρi,12 α ( ) (Urpin, Changmugam & Sang 1994 [ ] Urpin & Yakovlev 2008) Ambipolar diffusion in the core can be relevant if B >> 1015 G τd,amb ~ 104 yrs ρ15/b (Goldreich & Reisenegger 1992, Thompson & Duncan 1996, Dall'Osso et al. 2009, But: Glampedakis et al for effects of superfluidity)

38 Dipole decay modes vs. observations

39 Dipole decay modes vs. observations

40 Dipole decay modes vs. observations

41 Dipole decay modes vs. observations

42 Dipole decay modes vs. observations

43 Age costraints on α Upper limit to quiescent luminosity of SGR LX ~ erg/s (Rea et al. 2010) implies lower limit to age based on passive cooling τage~ 105 yrs τd ~ 103 yrs/b15α 1 α < 2

44 Age costraints on α Kaplan & van Kerkwijk 2011

45 Age costraints on α Kaplan & van Kerkwijk 2011

46 Age costraints on α 3 10 τ d α yrs B15 Kaplan & van Kerkwijk 2011 with 1.5 α 1.8

47 Luminosity evolution vs. dipole decay

48 Luminosity evolution vs. dipole decay Decay of the Dipole Field does not match LX evolution 5 It cannot power PERSISTENT ~ 105 yrs c Additional energy source required Internal magnetic field?

49 Decay of the internal B-field Ambipolar diffusion in the fluid core Heating balanced by ν-cooling(urca) equilibrium T

50 Decay of the internal B-field Ambipolar diffusion in the fluid core Heating balanced by ν-cooling(urca) equilibrium T Hall decay in the deep crust Maximum surface emission limited by ν's

51 Decay of the internal B-field Ambipolar diffusion in the fluid core Heating balanced by ν-cooling(urca) equilibrium T Hall decay in the deep crust Maximum surface emission limited by ν's Persistent : Bint 1016 G (same conclusion in Turolla et al. (2011)) Transients: underluminous in quiescence (??) internal source for outbursts (Pons et al. 2009, Pons & Perna 2012) XDINs : no hint for internal field, but for 1 outlier (possible link)

52 Recent population studies More on LX vs. B Olausen & Kaspi 2013

53 Recent population studies More on LX vs. B Olausen & Kaspi 2013

54 Future directions Transients: statistics have just started to improve thanks to new gamma-ray detectors more observational work required Persistent vs. transient sources: what is the cause of the dichotomy?