March 28, 2008
Download
1 / 36

ACCRETING X-RAY MILLISECOND PULSARS IN OUTBURST - PowerPoint PPT Presentation


  • 63 Views
  • Uploaded on

March 28, 2008. Cool discs, hot flows, Funäsdalen, Sweden. ACCRETING X-RAY MILLISECOND PULSARS IN OUTBURST. M A U R I Z I O F A L A N G A. Service d‘Astrophysique, CEA –Saclay, France. Collaborators: J. Poutanen, L. Kuipers, J. M. Bonnet-Bidaud. March 28, 2008.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' ACCRETING X-RAY MILLISECOND PULSARS IN OUTBURST ' - nova


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

March 28, 2008

Cool discs, hot flows, Funäsdalen, Sweden

ACCRETING X-RAY MILLISECOND PULSARS IN OUTBURST

M A U R I Z I O F A L A N G A

Service d‘Astrophysique, CEA –Saclay, France

Collaborators:

J. Poutanen, L. Kuipers,

J. M. Bonnet-Bidaud


March 28, 2008

Cool discs, hot flows, Funäsdalen, Sweden

MSPs hosted in LMXBs

Close X-ray binaries: Companion: M << Msun, Accretion disk, Compact object NS: B~108G

  • 8 SXT which show X-ray millisecond coherent modulation.

  • Spin frequencies lie between 180 and 600 Hz.(see review by Wijnands 2004, astro-ph/0403409)

  • Rich time variability, such as twin QPOs at kHz frequencies (400 - 1300 Hz, increasing with Mdot); kHz QPOs are thought to reflect Kepler at the inner accretion disk.(Van der Klis, 2000, astro-ph/00001167)

    (The Power spectra obtained for SAX J1808.4-3658 during 2002 outburst.)

  • Type-I X-ray bursts, with nearly coherent oscillations in the range 300-600 Hz .

  • Burst oscillations reflect the NS spin frequency

    (D. Chakrabarty, Nature, 2003)

    (Burst oscilation from SAX J1808.4-3658 during 2002 outburst.)

  • SXT:

    L ~ 1031-1032 erg/s in quiescent

  • L ~ 1036-1038 erg/s in outburst, recurence time 2-5 yr.


March 28, 2008

Cool discs, hot flows, Funäsdalen, Sweden

The growing family of the X-ray millisecond pulsars

…now we know 8 LMXBs (transients) which show X-ray millisecond coherent modulation:

SAX J1808.4-3658: Ps = 2.5ms, Porb = 2hr (Wijnands & van der Klis 1998)

XTE J1751-306: Ps = 2.3ms, Porb = 42min (Markwardt et al. 2002)

XTE J0929-314: Ps = 5.4ms, Porb = 43.6min (Galloway et al. 2002)

XTE J1807-294: Ps = 5.3ms, Porb = 40min (Markwardt et al. 2003)

XTE J1814-388: Ps = 3.2ms, Porb = 4.3hr (Markwardt et al. 2003)

IGR J00291+5934: Ps = 1.67ms, Porb = 2.46hr (Eckert et al. 2004)

HETE J1900.1-2455: Ps = 2.65ms, Porb = 1.4hr(Markwardt et al. 2005)

Swift J1756.9-2508: Ps = 5.49ms, Porb = 54.7min(Krimm et al. 2007)


March 28, 2008

Cool discs, hot flows, Funäsdalen, Sweden

A Decade of Accreting millisecond X-ray Pulsars

SAX J1808.4-3658

Amsterdam, 14 - 18 April 2008


IGR J00291+5934

SAX J1808..4-3658

XTE J1814-338

Brown dwarfs

Companion radius Rc/Rsun

0.1 Gyr

1 Gyr

XTE J0929-314

XTE J1751-305

XTE J1807-294

5 Gyr

White dwarfs

Companion mass Mc/Msun

March 28, 2008

Cool discs, hot flows, Funäsdalen, Sweden

Companion Star

Assuming that the companion star should fill its Roche lobe to allow sufficient accretion on the compact star (Bildsten & Chakrabarty, 2001)

  • Brown dwarf models at different ages (Chabrier et al. 2000, Deloye&Bildsten, 2003)

  • Cold low-mass white dwarfs with pure-helium composition

  • IGR J00291+5934

  • SAX J1808.4-3658 H-rich donor, brown dwarf

  • XTE J1814-338

  • HETE J1900.1-2455

  • XTE J0292-314

  • XTE J1751-305 H-poor, highly evolved dwarf

  • XTE J1807-294

  • Swift J1756.9-2508


Helium-rich Thermonuclear Bursts and the Distance to the Accretion-powered MSP

Ledd ~ 3.8 x 1038 erg s-1

L R2T4

α= (Fpers/fb)∆t

The time between bursts was long enough for hot CNO burning to significantly deplete the accreted hydrogen, so that ignition occurred in a pure helium layer underlying a stable hydrogen burning shell.


March 28, 2008 Accretion-powered MSP

Cool discs, hot flows, Funäsdalen, Sweden

Milliseconds Bursts oscillations

XTE J1739-285

SAX J1808.4-3658

4U 1728-34

(D. Chakrabarty, Nature, 2003)

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

(Kaaret et al. 2007)


Distinct knee Accretion-powered MSP

Outburst are extended as a consequence of

X-ray irradiation of the disk?(King & Ritter 1998)

March 28, 2008

Cool discs, hot flows, Funäsdalen, Sweden

OUTBURST PROFILE

Discovery(Eckert et al. 2004)

XTE J1807-294

XTE J1807-294

From RXTE

(Galloway et al. 2005)

ISGRI 20-100 keV

(Falanga et al. 2005)

(Falanga et al. 2005)

(Wijnands 2005, astro-ph/0403409)


March 28, 2008 Accretion-powered MSP

Cool discs, hot flows, Funäsdalen, Sweden

Outburst are extended as a consequence of X-ray irradiation of the disk(King & Ritter 1998)

Theory:dwarf novae, SXT

XTE J1751-305

4U 1705-44

Hot viscose state

Rh < Rdisc

SAX J1808.4-3658

Central object prevents the disk to cool down due to Irradiation, on a viscous time-scale,

accounting for the exponential decay of the outburst on a timescale τ~20–40 d.

(Powell, Haswell & Falanga, 2007)


March 28, 2008 Accretion-powered MSP

Cool discs, hot flows, Funäsdalen, Sweden

OUTBURST PROFILE

HETE J1900.1-2455

(Falanga et al. 2007)

After 60 days: Period disappeared

(Kaaret, et al. 2007)

NEW: Intermittent Pulsation

(Galloway et al. 2007

(Piro & Bildsten, 2005)


Decembre 3, 2007 Accretion-powered MSP

ISSI Bern

Intermittent MSP

SAX J1748.9-2021 (Globular Cluster NGC 6440), Pspin = 2.26 ms, Porb = 8.3 hr

(Altamirano et al. 2007)

AQL X-1, Pspin = 1.8 ms, Porb = 19 hr

(Casella et al. 2007)


  • The reason for the lack of coherent pulsations in the persistent emission from LMXBs

  • Different explanations:

  • Gravitational deflection (lensing effect)(Wood et al.1988)

  • Electron scattering (Brainerd & Lamb, 1987; Titarchuk et al. 2002) ~1/(1+τc) or (τc > 4)

  • Weak surface magnetic fields due to magnetic screening (e.g., Cumming et al. 2001)

  • Rayleigh-Taylor instability:Depending on the accretion rate, a star may be in the stable or unstable regime of accretion.(Kulkarni & Romanova 2008)


INTEGRAL persistent emission from LMXBs Observation IGR J00291+5934

IGR J00291+5934

March 28, 2008

Cool discs, hot flows, Funäsdalen, Sweden

(80 - 200 keV)

December 2004 Outburst

Exposure 343 ks

IGR J00291+5934

2S0114+650

Cas Gamma

Cas A

V709 Cas

(20 - 40 keV)

(20-40 keV) significance level ~88σ

derived angular distance: 18´

(40-80 keV) significance level ~51σ

(80-200 keV) significance level ~17σ


March 28, 2008 persistent emission from LMXBs

Cool discs, hot flows, Funäsdalen, Sweden

Geometry of the emission region

The plasma is heated by the accretion shock as the material collimated by the hotspot on to the surface. The seed photons for Comptonization are provided by the hotspot.

θ

B ~ 108 G

Seed photons from the hotspot

Thermal Comptonization in plasma of Temperature ~ 40 keV

XTE J1807-294

Rm

Thermal disk emission

(Falanga, Bonnet-Bidaud, Poutanen et al. 2005)


Spectral energy distribution
Spectral energy distribution persistent emission from LMXBs

Gierlinski & Poutanen 2003

Poutanen & Gierlinski 2001

spot

kTbb =0.66keV

kTe = 60 keV

tT = 0.9

XTE J1751-305

disc

Falanga et al 2007

Falanga et al 2005

HETE J11900.1-2455

IGR J00291+5934


March 28, 2008 persistent emission from LMXBs

Cool discs, hot flows, Funäsdalen, Sweden

Spectral evolution

IGR J00291+5934

XTE J1751-305

Gierlinski & Poutanen 2003

Falanga et al. 2005


March 28, 2008 persistent emission from LMXBs

Cool discs, hot flows, Funäsdalen, Sweden

PULSE PROFILE

IGR J00291+5934

Rev 261/262/263, ~205

Porbit = 2.457 hr

Ps = 1.67 ms

Pdot = +8.4 x 10-13 Hz/s

(Falanga, Kuiper, Poutanen et al. 2005)


March 28, 2008 persistent emission from LMXBs

Cool discs, hot flows, Funäsdalen, Sweden

Pulsed fraction and Time lag : IGR J00291+5934

(Falanga, Kuiper, Poutanen et al. 2005)

(Falanga et al. 2005)

If the spectrum has a sharp cutoff, the rms amplitude of the pulse at energies above the cutoff increases dramatically.

F(E) ≈E-(Γ0-1) exp(-[E/Ec]β),Componization photon indexΓ(E) = Γ0 + β(E/Ec)β


Hard X-ray persistent emission from LMXBs

Soft X-ray

Hot corona

Accretion disk

March 28, 2008

Cool discs, hot flows, Funäsdalen, Sweden

(Falanga et al. 2005)

Time lag IGR J00291+5934

Time lag are normally hard

Compton scattering model

The energy spectra often observed in LMXBs suggests that the dominant radiative mechanism in the system is Compton scattering of soft photons in a hot plasma.

(For a review of models for spectral variability and time lags seePoutanen 2001)


Accretion persistent emission from LMXBs

column

θhot

Hard photons

1-Cill

Hard photons

θref

Disk soft photons

Cill

Neutron Star

Soft photons

Disk

Compton cloud

March 28, 2008

Cool discs, hot flows, Funäsdalen, Sweden

(Falanga & Titarchuk 2007)

Time/Phase Lag Model

∆t(Cill,ref,hot,neref,nehot) =

upscattering lag + downscattering lag


March 28, 2008 persistent emission from LMXBs

Cool discs, hot flows, Funäsdalen, Sweden

Recycling model for MSPs

  • LMXB phase preceding the MSP stage;

    • mass transfer stops;

    • the radio MSP switches on

Old Neutron stars spin up by accretion from a companion

Spin up by mass accretion

  • Most binary MSPs have short orbital

  • periods and mass function identifying the

  • companions as low mass evolved dwarfs

Radio Pulsar

Millisecond Radio Pulsar

Accreting NS in LMXBs are conventionally thought to be the progenitors of millisecond or „recycled“ radio pulsars(Alpar et al. 1982)

X-ray transients can be the missing link between LMXBs and MSPs!


March 28, 2008 persistent emission from LMXBs

Cool discs, hot flows, Funäsdalen, Sweden

Spin-up IGR J00291+5934

We measured for the first time a spin-up for an accreting X-ray millisecond Pulsar

υ= + 8.4 ×10-13 Hz s-1

(Falanga et al. 2005)

(Burderi et al. 2007)

υ= + 3.7 ×10-13 (L37/η-1I45) (Rm/Rco)1/2 (M/1.4Msun) (υspin/600)-1/3 Hz s-1


March 28, 2008 persistent emission from LMXBs

Cool discs, hot flows, Funäsdalen, Sweden

YES

Is the Spin-up real?

An error in the source coordinates can give rise to timing error which may introduce a spurious spin-up or spin-down

0.2 arcsec

0.092 arcsec

0.2 arcsec

0.092 arcsec

1 Year

Our observation

0.092 arcsec source position error would introduce a non-existant spin-up rate of

Such an apparent spin-up would require a fairly large ~ 0.7 arcsec source position error during our observation

υ= + 5.8 ×10-14 Hz s-1


« Star eats companion » persistent emission from LMXBs

«Une étoile cannibale »


Pulsar spin-up Animation persistent emission from LMXBs

NASA, D. Barry


Modeling the Pulse Profile persistent emission from LMXBs

XTE J1751-305

disc

Gierlinski & Poutanen 2003

XTE J1807-294

XTE J1814-338

kTdisc=0.43 keV

kTseed = 0.75 keV

Aseed = 26 km2

kTe = 37 keV

tT = 1.7

Kirsch et al. (2003)

Strohmayer et al. (2003)


Strong-field persistent emission from LMXBs General Relativity is required to describe the lightcurve observed at infinit.

(Gierlinski & Poutanen, 2005)

(Morsink et al. 2007)


The geometry of the model persistent emission from LMXBs

  • Motion of Matter

  • (Time-like geodesics)

  • Curved photon trajectories

  • (Null-like geodesics)

  • Doppler shift : (1 + z)

  • The solid angle : d(R,d,i,db)

  • (Gravitational lensing effect)

  • Travel time delay

  • The observed flux : F =  Idd

(Schwarzschild metric)


Modeling the pulse profile oblateness of rapidly rotating ns

March 28, 2008 persistent emission from LMXBs

Cool discs, hot flows, Funäsdalen, Sweden

Modeling the Pulse Profile: oblateness of rapidly rotating NS

i = 70°,  = 49°

i = 20°,  = 41°

Morsink et al. 2007


Light curves of msp
Light curves of MSP persistent emission from LMXBs

Fbb(fast) = Fbb(slow) xd5

Doppler boostingIobs=d4Iem

Aberration cos aobs=dcos ae

slow pulsar (dashes)

fast pulsar, =401 Hz

Fsc,E(fast) ~d3+GFsc,E(slow)

d=1/g(1 - b cos q)

– Doppler factor

g=1/1-b2

– Lorentz factor

Poutanen & Gierliński (2003)


Constraints on the neutron star mass-radius relation obtained by fitting the pulse profile of SAX J1808.4-3658

  • Complications:

  • Shape of the star

  • Shape of the spot

  • Influence of the accretion disk

(Poutantn & Gierlinski 2003)


March 28, 2008 obtained by fitting the pulse profile of SAX J1808.4-3658

Cool discs, hot flows, Funäsdalen, Sweden

Important Questions

  • Missing link between LXMB and ms radio pulsar ?

  • Analysis suggests that the spin frequency is limited to 760 Hz (95% confidence; Chakrabarty et al. 2003)

  • Several have suggested that gravitational radiation from a non-spherical neutron star might limit the maximum fraquency (Bildsten et al. 1998)

  • Detection by LISA?

  • Detecting more of these source with more instrument than before


March 28, 2008 obtained by fitting the pulse profile of SAX J1808.4-3658

Cool discs, hot flows, Funäsdalen, Sweden

Thank You…


March 28, 2008 obtained by fitting the pulse profile of SAX J1808.4-3658

Cool discs, hot flows, Funäsdalen, Sweden

Pulsar spin-up

M

R(corotation)

Accretion regime

Rm< Rcor

The accreting matter transfers its specific angular momentum (the Keplerian AM at the magnetospheric radius) to the neutron star: L=(GMRm)1/2

R(magnetosphere)

Propeller regime

Rm> Rcor

The process goes on until the pulsar reaches

the keplerian velocity at Rm (equilibrium period); Pmin when Rm = Rns

(Illarionov & Sunyaev 1975)

The conservation of AM tells us how much mass is

necesssary to reach Pmin starting from a non-rotating NS


March 28, 2008 obtained by fitting the pulse profile of SAX J1808.4-3658

Cool discs, hot flows, Funäsdalen, Sweden

Pulse profile IGR J00291+5934

HEXTE

11.4 σ 20.3-35.2 keV

ISGRI 9.1σ 20-35 keV

HEXTE

8.3 σ 35.2-60.1 keV

ISGRI 7.3 σ 35-60 keV

HEXTE

3.3 σ 60.1-100.9 keV

ISGRI 5.0 σ 60-100 keV

JEM-X 4.0 σ 5-10 keV

Rev 261/262/263, ~205

Porbit = 2.457 hr

Ps = 1.67 ms

Pdot = +8.4 x 10-13 Hz/s

HEXTE

1.1 σ 100.9-151.1 keV

ISGRI 2.0 σ 100-150 keV

(Falanga et al. 2005)


INTEGRAL obtained by fitting the pulse profile of SAX J1808.4-3658 CODED MASK (IBIS, SPI & JEM -X)

Observation

CorrectedImage

DeconvolvedImage

End Image

Coded Mask

Shadow


ad