1. Low Mass X-ray Binaries and Accreting Millisecond Pulsars A. Patruno R. Wijnands R. Wijnands M. van der Klis M. van der Klis P. Casella D. Altamirano D. Altamirano N. Danegaar N. Danegaar ASTRONOMICAL INSTITUTE A. PANNEKOEK UNIVERSITY OF AMSTERDAM

2. Low Mass X-ray Binaries & Accreting Millisecond Pulsars

3. Projects in Amsterdam Accreting Millisecond Pulsars (AMPs) Periodic Timing Intermittent pulsars Cooling of LMXBs (cooling curves, EOS) Magnetars Magnetars QPOs QPOs Radio Pulsars (timing, glitches) Radio Pulsars (timing, glitches) Neutron Star oscillations Neutron Star oscillations Thermonuclear bursts Thermonuclear bursts

4. Periodic Timing 1: the pulse profiles 1.Fold pulse profiles (extreme variability) 2. Track the phase of each folded profile, i.e., determine the Time Of Arrivals of the pulsations (TOAs) 3. Fit a model to the TOAs: for example a binary circular orbit + a spin frequency 4. Look at the residuals ! Fig. from Hartman et al. 2008

5. Periodic Timing 2: the Timing Noise XTE J1807-294 SAX J1808.4-3685 XTE J1814-338 Hartman, Patruno et al. 2008 Patruno Hartman et al. in prep.

6. Periodic Timing 3: the enigmatic FAR relations XTE J1814-338 XTE J1807-294 The fractional amplitude of the pulsations is anticorrelated with the time of arrival of the pulsations (i.e. when the fractional amplitude is larger the pulses arrive earlier than predicted by the model) Patruno et al. in prep.

7. Periodic Timing 4: physical interpretation Long et al. 2008 1. No glitches: is the hot spot moving ? (it has to preserve the 2 nd harmonic’s phase) 2. Why we see timing noise and FAR relations only in some AMPs ? SAX J1808-3658: 50 deg. in 2002 and 2005 outbursts (Hartman et al. 2008) XTE J1807-294: up to ~100 deg. (Patruno et al. in prep) SAX J1748.4-2021: ~140 deg. (Patruno et al. 2008) XTE J1814-338: ~50 deg. Gradually (Papitto et al. 2007)

8. 12 years 3 months 25 minutes 150 seconds pulsations at ν = 550.27 Hz detected in 0.01% of the exposure Casella et al. 2007 Intermittent Pulsar 1: the discovery of pulsations in Aql X-1

9. 7 years few hours few minutes pulsations at ν = 442.36 Hz in a few % of the exposure Altamirano et al. 2007 Gavriil et al. 2007 Patruno et al. 2008 Intermittent pulsar 2: SAX J1748.9-2021

10. HETE J1900.1-2455 only first 2 months SAX J1748.8-2021 intermittent, hundreds of seconds SAX J1748.8-2021 intermittent, hundreds of seconds Aql X-1 only for 150 seconds Aql X-1 only for 150 seconds Intermittent pulsar 3: current situation 7 AMPs with pulsations throughout the outburst Is magnetic screening ruled out ?

11. Cooling of accreting Neutron Stars Quasi persistent sources: very long outbursts (KS 1731-260: 12.5 years, MXB 1659-29: 2.5 years) compared to “normal” X-Ray Binaries

12. Cooling of accreting Neutron Stars KS 1731-260MXB 1659-29 Flux and Temperature well fitted by an exponential decay plus a constant offset (core temperature) y(t)=a exp[-(t-t0)/b] + c y(t)=a exp[-(t-t0)/b] + c a = normalization constant b = e-folding time c = constant offset (core temperature)

13. Cooling of accreting Neutron Stars: physical interpretation Rutledge et al 2002, Wijnands 2005, Cackett et al. 2006 Rutledge et al. 2002 calculated detailed cooling curves for KS 1731-260 using the mass accretion history of the source. High crust thermal conductivity Enhanced cooling

14. Open issues What is the origin of the timing noise in AMPs ? What is the origin of the timing noise in AMPs ? Why pulse shape changes ? (motion of the hot spot, magnetic field instabilities) Why pulse shape changes ? (motion of the hot spot, magnetic field instabilities) Why we see intermittent pulsations ? (magnetic field burial, smearing of pulsation, crustal cracks) Why we see intermittent pulsations ? (magnetic field burial, smearing of pulsation, crustal cracks) Cooling: are the cooling curves suggesting an enhanced neutrino emission and high crustal thermal conductivity ? Cooling: are the cooling curves suggesting an enhanced neutrino emission and high crustal thermal conductivity ?

15. THANK YOU !