Recent Suzaku Results on Strongly Magnetized Neutron Stars Kazuo Makishima (University of Tokyo and RIKEN) T. Enoto, T. Mihara, M. Nakajima, K. Nakazawa, & Y. Terada 2008/5/29 X-ray Universe 2008

1. Strongly Magnetized NSs Measurements of surface m.f. using electron cyclotron resonances; 　Ea = 11.6 (B/1012G) keV Measured m.f. strengths clustered in (1~5)x1012 G (Makishima + 99). “Field decay” hypothesis unlikely. Resonance photosphere height depends on Lx (Nakajima Poster D.7). 2 4 6 8 10 Resonance Energy (keV) Number 100 20 5 50 Log B (Gauss) 12 13 BeppoSAX Ginga RXTE Suzaku ASCA Is m.f. due to nuclear ferromagnetism (Makishima + 99)? Magnetars really have 1014-15 G? Any objects in between ordinary pulsars and magnetars? Origin of the resonance width? 2008/5/29 X-ray Universe 2008

2. Suzaku Observations [Accreting Binary Pulsars] A0535+26 Terada+ ApJL (2006); Naik+ ApJ (2008) Her X-1 Enoto+ PASJ (2008); Terada+ AdSpRes (2007) 4U 1626-67 GRO J1008-57 (TOO) [Rotation-Powered Pulsars] The Crab pulsar PSR 1509-58 Terada+ PASJ (2008) [Magnetars] 4U 0142+61 Enoto+. in prep. 1E 1841-045 Morii+ AIPC (2008) AXP CXOU J164710.2-455216 (TOO) Naik+ PASJ (2008) SGR1900+14 (TOO) SGR 1806-20 (TOO; burst+persistent) Esposito+ A&A (2008) PSR 1509 On-Off, 45 ks HXD-PIN HXD-GSO 2008/5/29 X-ray Universe 2008

3. Crab Ratios Continuum and absorption couple strongly. 0.05 0.02 0.01 .002 42 keV 2005 36 keV HXD-GSO 2006 0.1 .01 Lx=4x1035 erg/s A0535+26 (Suzku,Terada+06） HXD-PIN Her X-1 on-off (Suzaku, Enoto + 08) Lx=3x1037 erg/s 20 50 100 200 23 keV 1 .1 .01 20 50 100 200 Energy (keV) Continuum and absorption couple strongly. Using regions near Ea1/2 and >3Ea1, define the continuum as f(E)=AEα exp(-E/Ecut) X0331+53 (RXTE ; Nakjima + 08) Lx=3x1038 erg/s 5 10 20 50 100 2008/5/29 X-ray Universe 2008

4. Extraction of Absorption Profiles Assuming spectrum = f(E)xexp[-S(E)], exp[-S] is plotted logarithmically. The vertical scale thus becomes -S itself. The energy axis is normalized to Ea1, and ordinatge is adjusted by ~20% The three objects exhibt very similar profiles. 0 50 100 150 200 A0535+26 Her X-1 On-Off X0331 RXTE 1 0.5 0.2 0.1 pivot 2008/5/29 X-ray Universe 2008

5. Joint Fitting of the 3 Pulsars F(E)=(aE-α+bEβ) exp(-E/Ecut) exp{-S1(E/Ea1)-S2(E/Ea2)} ・“NPEX” continuum : independent among the three. ・S1: Lorentzian xE2, common to the three as a function of E/Ea. ・S2 : likewise, but X0331 is allowed to have separate Ea2 and W2. Count Spectra X0331 (PCA) X0331 (HEXTE) Deconvolved νFν 10 20 50 100 keV Her X-1 A0535 (PIN) A0535 (GSO) χ2/ν=1.08 D1=1.61 ± 0.06 W1/Ea1=0.36 ±0.02 D2=1.51 ± 0.13 10 20 50 100 keV 2008/5/29 X-ray Universe 2008

6. Implications The 3 objects are in common physical conditions, despite the luminosity differences by ~3 orders of magnitude. cf. Not claiming that this applies to all accreting pulsars. The NPEX continuum is justified; the1st and 2nd resonances heavily affect the continuum even in between Ea1 and Ea2. Gaussian absorption cross section gives significantly worse joint fits than the Lorentzian x E2 cross section (Enoto et al. 2008); chi^2=347.43 vs. 307.01 for the same d.o.f=287. The resonance width may not be explained by the thermal Doppler effects. Unexpectedly short lifetimes of the excited Landau levels (Enoto et al. 2008)? 2008/5/29 X-ray Universe 2008

7. AXP 4U0142+61 (Enoto et al.) Observed with Suaku on 2007 Aug. 13 for 93 ksec. Soft pulsations are stable. Hard pulses vary on ~30 ks. Very hard component with Gamma~1. Improves INTEGRAL results (Kuiper+06). GSO XIS PIN P=8.688784 sec 0 0.5 1 1.5 2 1st 30 ks 2nd 30 ks 3rd 30 ks 0.06 0.04 0.02 e+e- creation --> rush onto mag.poles --> non-thermal Bremss --> Compton back scatt. (Kotoku+07 PASJ) A0535+26 BGD-subtracted 10-70 keV folded pulse profile 2008/5/29 X-ray Universe 2008

8. Summary Spectra of accreting X-ray pulsars are strongly affected by electron cyclotron resonances, but the effects may be rather common among different objects. The continuum must be carefully determined using wide-band data. The spectrum of an AXP, 4U 0142+61. is clearly distinct from those of any accreting/rotating X-ray pulsars. A ultra-strong MF provides the most likely explanation. Existence of intermediate objects between magnetars and normal strong-field NSs is open (cf. Dr. Haberl’s talk). Further Suzaku observations are of great value. 2008/5/29 X-ray Universe 2008