Low Mass X-ray BinariesLow Mass X-ray Binariesand Accreting and Accreting Millisecond PulsarsMillisecond Pulsars

A. Patruno A. Patruno R. Wijnands R. Wijnands

M. van der Klis M. van der Klis P. CasellaP. Casella

D. Altamirano D. Altamirano N. DanegaarN. Danegaar

ASTRONOMICAL INSTITUTE A. PANNEKOEK ASTRONOMICAL INSTITUTE A. PANNEKOEK UNIVERSITY OF AMSTERDAMUNIVERSITY OF AMSTERDAM

Low Mass X-ray Binaries & Accreting Low Mass X-ray Binaries & Accreting Millisecond PulsarsMillisecond Pulsars

Projects in AmsterdamProjects in Amsterdam

Accreting Millisecond Pulsars (AMPs)

Periodic Timing

Intermittent pulsars Cooling of LMXBs (cooling curves, EOS) MagnetarsMagnetars QPOs QPOs Radio Pulsars (timing, glitches)Radio Pulsars (timing, glitches) Neutron Star oscillations Neutron Star oscillations Thermonuclear bursts Thermonuclear bursts

Periodic Timing 1: the pulse Periodic Timing 1: the pulse profilesprofiles1. 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. 2008Fig. from Hartman et al. 2008

Periodic Timing 2: the Periodic Timing 2: the Timing NoiseTiming Noise

XTE J1807-294

SAX J1808.4-3685

XTE J1814-338

Hartman, Patruno et al. 2008Hartman, Patruno et al. 2008

Patruno Hartman et al. in prep.Patruno Hartman et al. in prep.

Periodic Timing 3: the enigmatic Periodic Timing 3: the enigmatic FAR relationsFAR 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.

Periodic Timing 4: physical Periodic Timing 4: physical interpretationinterpretation

Long et al. 2008

1. No glitches: is the hot spot moving ? (it has to preserve the 2nd 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)

12 years

3 months

25 minutes

150 seconds

pulsations at ν = 550.27 Hz

detected in 0.01% of the exposure

Casella et al. 2007Casella et al. 2007

Intermittent Pulsar 1: the discovery Intermittent Pulsar 1: the discovery of pulsations in Aql X-1of pulsations in Aql X-1

7 years

few hours

few minutes

pulsations at ν = 442.36 Hz

in a few % of the exposure

Altamirano et al. 2007Altamirano et al. 2007Gavriil et al. 2007Gavriil et al. 2007Patruno et al. 2008Patruno et al. 2008

Intermittent pulsar 2: SAX Intermittent pulsar 2: SAX J1748.9-2021J1748.9-2021

HETE J1900.1-2455 only first 2 monthsHETE J1900.1-2455 only first 2 months

SAX J1748.8-2021 intermittent, hundreds of SAX J1748.8-2021 intermittent, hundreds of secondsseconds

Aql X-1 only for 150 secondsAql X-1 only for 150 seconds

Intermittent pulsar 3: current Intermittent pulsar 3: current situationsituation

7 AMPs with pulsations throughout the 7 AMPs with pulsations throughout the outburstoutburst

Is magnetic screening ruled out ?

Cooling of accreting Cooling of accreting Neutron StarsNeutron 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

Cooling of accreting Cooling of accreting Neutron StarsNeutron Stars

KS 1731-260 MXB 1659-29

Flux and Temperature well fitted by an exponential decay plus a constant offset (core temperature)

y(t)=y(t)=aa exp[-(t-t0)/ exp[-(t-t0)/bb] + ] + cc

a = normalization constant

b = e-folding time

c = constant offset (core temperature)

Cooling of accreting Neutron Cooling of accreting Neutron Stars: physical interpretationStars: 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

Open issuesOpen 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, Why pulse shape changes ? (motion of the hot spot,

magnetic field instabilities)magnetic field instabilities) Why we see intermittent pulsations ? (magnetic field Why we see intermittent pulsations ? (magnetic field

burial, smearing of pulsation, crustal cracks)burial, smearing of pulsation, crustal cracks) Cooling: are the cooling curves suggesting an Cooling: are the cooling curves suggesting an

enhanced neutrino emission and high crustal enhanced neutrino emission and high crustal thermal conductivity ? thermal conductivity ?

THANK YOU !