Progress in Pulsar detection

Transcription

1

2 Progress in Pulsar detection With EINSTEIN & EXOSAT: 7 radio pulsars detected in X-rays With ROSAT, ASCA & BSAX: 33 radio pulsars detected in X-rays After ~8 yrs with XMM & Chandra: 81 radio pulsars detected in X-rays 8 pulsars fall into the category of old and nearby neutron stars Becker, Haberl & Trümper 2007

3 X-ray emission properties vary with spin-down age Crab-like pulsars (< 10 4 yrs) Fraction of pulsed photons ~100%

4 X-ray emission properties vary with spin-down age Crab-like pulsars (< 10 4 yrs) Cooling neutron stars ( ~ yrs) Fraction of pulsed photons ~100% Fraction of pulsed photons ~20-30%

5 X-ray emission properties vary with spin-down age Crab-like pulsars (< 10 4 yrs) Cooling neutron stars ( ~ yrs) Old pulsars (~ yrs) Fraction of pulsed photons ~100% Fraction of pulsed photons ~20-30%

6 X-ray emission properties vary with spin-down age Crab-like pulsars (< 10 4 yrs) Cooling neutron stars ( ~ yrs) Old pulsars (~ yrs) based on ROSAT obs. of PSR only Fraction of pulsed photons ~100% Fraction of pulsed photons ~20-30% sinusoidal

7 X-ray emission properties vary with spin-down age Crab-like pulsars (< 10 4 yrs) Cooling neutron stars ( ~ yrs) Old pulsars (~ yrs) based on ROSAT obs. of PSR only Fraction of pulsed photons ~100% Fraction of pulsed photons ~20-30% sinusoidal

8 XMM-Newton observations of old pulsars Becker, Weisskopf, Tennant et al. (2004) τ yrs ~ yrs yrs d ~ 255 pc ~ 340 pc ~ 1130 pc N H ~ cm -2 ~ cm -2 ~ cm -2 E ~ erg/s ~ erg/s ~ erg/s

9 X-ray emission properties of old pulsars B B α = α = BB spectra are clearly excluded J BB+BB model resulted in an emitting area for possible polar caps of ~cm size Simplest model: single PL spectrum fits best α = Becker, Weisskopf, Tennant et al. (2004)

10 X-ray emission properties of old pulsars: B pulse profile is NOT sinusoidal double peaked pulse profile phase separation between X-ray peaks of ~ 144 0, the same as for radio pulse and interpulse PF = %, phase separation ~ Becker, Weisskopf, Tennant et al. (2004)

11 XMM-Newton observations of old pulsars: B B τ 2.75 x 10 6 yrs E ~ 1.45 x erg/s d ~ 1.45 kpc N H ~ 6 x cm -2 Becker, Jessner, Kramer et al.(2005) PF = % ( kev)

12 XMM-Newton observations of old pulsars: B B BB spectra are clearly excluded single PL spectrum fits best non-thermal emission dominates α = ~ 20% thermal contrib. possible Becker, Jessner, Kramer et al.(2005)

13 The prototype of an old pulsar: PSR B τ 3.1 x 10 6 yrs P ~ 226 ms E ~ 3.9 x erg/s d ~ pc Becker, Kramer, Jessner et al. (2006)

14 The prototype of an old pulsar: PSR B PF = % ( kev) Becker, Kramer, Jessner et al. (2006)

15 The prototype of an old pulsar: PSR B > 1 kev < 1 kev PF = % PF = % Becker, Kramer, Jessner et al. (2006)

16 The prototype of an old pulsar: PSR B B ROSAT + XMM-Newton (MOS1/2 & PN) α = N H /10 = single PL spectrum fits best non-thermal emission dominates

17 The prototype of an old pulsar: PSR B BB+PL fit: in stretching the errors to the limits no more than ~40% of the emission could come from heated polar caps. Becker, Kramer, Jessner et al. (2006)

18 Pulsar Bow-Shocks

19 Pulsar bow-shock nebulae Proper motion with V p ram = ρ If the ram pressure exceeds the ambient amb gas pressure a bow-shock is formed V 2

20 Pulsar bow-shock nebulae: PSR The pulsar is moving at a transverse velocity of 177 km/s The trail emission is nonthermal and is likely produced from the synchrotron process of highly relativistic electrons in the shocked region between the pulsar wind and the surrounding ISM Becker, Kramer, Jessner et al.(2006)

21 X-ray emission properties of old pulsars: B Becker, Kramer, Jessner et al.(2006)

22 X-ray emission properties of old pulsars: B length of the trail not very well constraint requires deeper observations!! Becker, Kramer, Jessner et al.(2006)

23 X-ray emission properties of old pulsars: B B trail α = N H /10 = spectrum non-thermal likely from synchrotron processes in the shocked region between pulsar wind and the ISM

24 Resolving the bow-shock nebula around the old pulsar PSR B Hui & Becker (2007) / astro-ph:

25 Resolving the bow-shock nebula around the old pulsar PSR B Hui & Becker (2007) / astro-ph:

26 X-ray emission prop. scale with spin-down age Crab-like pulsars Cooling neutron stars Old pulsars non-thermal emission dominates in old pulsars / pulse profiles are NOT sinusoidal Diffuse bow-shock emission of these low Edot pulsars has the potential to challenge pulsar-wind models

27 X-ray emission properties of old pulsars younger older No evidence for a spectral softening with increasing spindown age for old pulsars

28 Surface temperature upper limits for R NS =10 km Pulsar Spin down age T S 3σ upper limt B x 10 6 yrs < k J x 10 6 yrs < k B x 10 6 yrs < k B x 10 6 yrs < k B x 10 6 yrs < k B x 10 6 yrs < k

29 X-ray emission properties of old pulsars

30 Neutron star temperature measurements Becker, Haberl & Trümper 2007