Observations and physics of Observations and physics of accreting neutron staraccreting neutron star

ISSI, Bern, SwitzerlandDecember 3-7, 2007

ParticipantsParticipants

Juri Poutanen (University of Oulu, Finland; Team Leader) Andrei Beloborodov (Columbia University, USA) Chris Done (University of Durham, UK)Maurizio Falanga (CEA-Saclay, Service d' Astrophysique, France) Marat Gilfanov (Max Planck Institute f\"ur Astrophysik, Garching, Germany)Tatiana Larchenkova (Astro Space Center, Moscow, Russia)Alexander Lutovinov (Space Research Institute, Moscow, Russia)Sergei Molkov (Space Research Institute, Moscow, Russia)Mike Revnivtsev (MPA, Garching, Germany) Valery Suleimanov (University of Tubingen, Germany) Andrzej Zdziarski (N. Copernicus Astronomical Center, Warsaw, Poland)

Young scientists Marja Annala (University of Oulu, Finland) Kris Beckwith (Univ. of Virginia, USA) Askar Ibragimov (University of Oulu, Finland) Sergey Tsygankov (Space Research Institute, Moscow, Russia)

Program for the meetingProgram for the meeting

Juri Poutanen: Introduction Alexander Lutovinov: About a possibility to observe the effect Shapiro for pulsars in globular clusters

Sergey Tsygankov: Observational features of X-ray pulsars emission revealed with INTEGRAL and RXTE observatories

Marja Annala: X-ray pulsarsMaurizio Falanga: X-ray accreting millisecond pulsars in outbursts

Valery Suleimanov: Importance of Compton scattering on radiation spectra of accretion columns in millisecond pulsars and intermediate polars

Askar Ibragimov: SAX J1808 in 2002

Topics to be coveredTopics to be covered

X-ray bursts & nuclear-powered millisecond pulsars (NMSPs)

Accreting millisecond pulsars (AMSPs)

X-ray pulsars

Theory of accretion columns on a weakly magnetized neutron stars

Theory of boundary layers on neutron stars

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© Michael Kramer

Nuclear-powered Nuclear-powered millisecond millisecond

pulsarspulsars

Source Orbital period [h] spin [Hz]

4U 1728-34 ? 363

4U 1636-53 ? 581

KS 1731-260 ? 524

at Gal. center ? 589

Aql X-1 19.0 549

4U 1702-429 ? 330

MXB 1658-298 7.1 567

4U 1916-053 0.83 270

4U 1608-52 ? 619

SAX J1750.8-2980 ? 601

A 1744-361 1.5 530

IGR J1719.1-2821 ? 294

SAX J1808.4-3658 2.0 401

XTE J1814-338 4.275 314

XTE J1739-285 ? 1122 ?

EXO 0748-676 3.82 45

Nuclear-powered millisecond pulsarsNuclear-powered millisecond pulsars

Time (s)

4U 1728-34

Strohmayer et al (1996); Strohmayer, Markwardt (1999)

Time (s)

Millisecond oscillations during X-ray burstsMillisecond oscillations during X-ray bursts

Time (s)

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simulations by A. Spitkovsky

Millisecond oscillations during X-ray burstsMillisecond oscillations during X-ray bursts

€

A(E)∝1

BE (T)

dBE (T)

dT∝xex

ex −1=

const, x <<1

x, x >>1

⎧ ⎨ ⎩

x =E

kT

Piro & Bildsten 2006

Observed A(E) is consistent with the black body

Pulse fraction in X-ray burstsPulse fraction in X-ray bursts

RMS in X-ray bursts from AMSP XTE J1814-338RMS in X-ray bursts from AMSP XTE J1814-338

Theory of the accretion column for X-ray burstersTheory of the accretion column for X-ray bursters

Accretion-powered Accretion-powered millisecond pulsarsmillisecond pulsars

Romanova et al. (2004)

Power density spectrum.From Wijnands & van der Klis (1998). April 1998 outburst.

From Gilfanov et al. (1998).

SAX J1808.4-3658: SAX J1808.4-3658: the first accreting millisecond pulsarthe first accreting millisecond pulsar

SAX J1808.4-3658

XTE J1751-305

XTE J1807-294

Outbursts profilesOutbursts profiles

1. Wijnands & van der Klis 1998, Chakrabarty & Morgan 1998; 2. Markwardt et al. 20023. Remillard et al. 2002; Galloway et al. 2002; 4. Markwardt et al. 20035. Markwardt et al. 2003; 6. Markwardt, Swank, Strohmayer, Dec 3, 20047. Morgan, Kaaret, Vanderspek, June 17, 2005; Kaaret et al. 2005; 8. Markwardt et al. June 14, 2007

Source Porb

min spin Hz fX / MSun Mc,min/

MSun

1. SAX J1808.4-3658 120 401 3.779 x 10-5 0.05

2. XTE J1751-305 42 435 1.278 x 10-6 0.013

3. XTE J0929-314 44 185 2.9 x 10-7 0.01

4. XTE J1807-294 40 190 1.49 x 10-7 0.007

5. XTE J1814-338 257 314 2.016 x 10-3 0.16

6. IGR J00291+5934 148 599 2.813 x 10-5 0.038

7. HETE J1900.1-2455 83 377 2.00 x 10-6 0.016

8. SWIFT J1756.9-2508 55 182 1.66 x 10-7 0.007

Accretion-powered millisecond pulsarsAccretion-powered millisecond pulsars

XTE J1751-305

IGR J00291+5934XTE J1807-294

disc

spot

kTbb

=0.66keVkTe = 60 keVT = 0.9

Spectral energy distributionSpectral energy distribution

kTdisc=0.43 keVkTseed = 0.75 keVAseed = 26 km2

kTe = 37 keVT = 1.7

disc

Solid – persistent emission; histogram - X-ray bursts. Strohmayer et al. (2003). Kirsch et al. (2003)

XTE J1751-305

XTE J1814-338XTE J1807-294

Gierlinski & Poutanen 2003

Pulse profilesPulse profiles

Pulsar geometryPulsar geometry

In ms pulsars, rotational velocities are high (=v/c ~0.1), the Doppler effect plays an important role

Doppler effectDoppler effect

Phase

slow pulsar (dashes)

fast pulsar, =401 Hz

Fsc,E(fast) ~ 3+ Fsc,E(slow)

Fbb(fast) = Fbb(slow) x 5

Poutanen & Gierliński (2003)

Doppler boosting Iobs4 Iem

Aberration cos obs cos e

Light curves of MSPLight curves of MSP

=1/(1 - cos ) – Doppler factor

=1/– Lorentz factor

Mass/ M

Poutanen & Gierlinski (2003)

Radius, km

Constraints on the equation of stateConstraints on the equation of state

Complications:

Shape of the star

Shape of the spot

Influence of the accretion disk

Cou

nt r

ate

Phase

Pulses from SAX J1808Pulses from SAX J1808

Bildsten et al. (1997)

X-ray pulsarsX-ray pulsars

Obtaining neutron star parameters from the X-ray pulse profiles

A0535+262

Boundary layers and quasi-Boundary layers and quasi-periodic oscillationsperiodic oscillations

Sco X-1

4U 1608-52

From Gilfanov, Revnivtsev and Molkov (2003).

Frequency-resolved spectra of QPOs and the boundary layer

Matter has a significant latitude velocity component, spreading above the neutron star surface and deceleratingdue to friction with the neutron star surface(as the wind above the sea).

From Inogamov and Sunyaev (1999)

BL as a spreading layer

SL model

Atoll & Z sources

GX 340+0

Spectra of neutron star BL

Constraints on EOS of NS

From Suleimanov and Poutanen (2006)

How QPOs are produced ?

• Analysis and theoretical modeling of the data on X-ray pulsars (Lutovinov, Tsygankov, Annala, Ibragimov)

• Modeling the accretion column (Suleimanov, Poutanen)

• Theoretical modeling the light curves from millisecond pulsars (Poutanen, Larchenkova, Falanga)

• Impact of the accretion disk on the light curves (Ibragimov, Annala, Poutanen)

• 2D and optically thin boundary layer models (Poutanen, Suleimanov)

Proposed projects Proposed projects