X−ray Spectral Modeling for Low−Mass X−ray Binaries

Mario Jimenez−Garate (MIT)

Collaborators: John Raymond (CfA) Duane Liedahl (LLNL)

Jimenez−Garate XRB 02

Photoionized Plasma Models

Particle−photon interactions

Heating = CoolingRecombination rate = Photoionization rate

Radiative cascade

Radiativerecombination

time

Photoionization

L

ner2

ξ =Ionizationparameter

Jimenez−Garate XRB 02

Low−Mass X−ray Binaries withBroad X−ray Line Emission

Hypothesis: Kepler−velocity

broadened lines from

the accretion disk

EXO 0748−676: eclipses, bursts, dips Porb= 3.8 hr, M2 ~ 0.4−0.8 Msun

4U1626: X−ray pulsarPorb= 42 min, M2 < 0.1 Msun

Jimenez−Garate XRB 02

HETGSchulz et al.(2001)

HETG

Centrally Illuminated AccretionDisk Atmosphere and Corona

Radiation TransferGravity

Hydrostatic EquilibriumThermal Balance

Ionization Equilibrium

4 π

Boundary conditions

θ

=

0

Adaptivezone grid

Isothermaldisk, τ>>1

z phot

Gravityz cor

m p

ρcor k T compton

µP =

r

Hot corona

Disk midplane

= 0

Atmosphere

Photosphere

2

Lx

m pµk Tphot photρ

P =

T = T phot

F

F

νF

ν

dν

F

z

dν

Jimenez−Garate XRB 02

X−rays

Gascolumn

Fνd

Fνu

Fν

DiskNeutron star

r

z

Corona

θα

R*

Schematic of exact geometryβ

α

LX = 1037, 1038 erg s−1

Centrally Illuminated AccretionDisk Atmosphere and Corona

Jimenez−Garate XRB 02

Vertical Ionization Structure

Atmosphere thickened by Irradiation

Centrally Illuminated Accretion Disk

Jimenez−Garate XRB 02

A Thick Atmosphere and Corona

Centrally Illuminated AccretionDisk Atmosphere and Corona

Synthetic X−ray Spectrum vs. Absorption NH of Neutron Star Flux

N = 10 cm21

22

−2H*

24N = 10 cm−2H*

N cm−2H* = 5 x 10

(a)

(b)

(c)

Jimenez−Garate XRB 02

Centrally Illuminated AccretionDisk Atmosphere and Corona

Synthetic Profilesand Plasma Diagnostics

Jimenez−Garate XRB 02

O VII i

r

HETG Data (EXO 0748−676)

Line profiles probe radial Atmosperic Changes

Centrally Illuminated AccretionDisk Atmosphere and Corona

Comparison with Spectral Data

Model

HETG Data (EXO 0748−676)

Jimenez−Garate XRB 02

Instr

?

?

Dips vs.No Dip

Dips

Centrally Illuminated AccretionDisk Atmosphere and Corona

Comparison with Spectral Data

Model

Data

Cottam et al. (2001)

XMM−Newton RGS, 30ks

EXO 0748−67

Jimenez−Garate XRB 02

EXO 0748−676: eclipses, bursts, dips Porb= 3.8 hr, M2 ~ 0.4−0.8 Msun

Cottam et al. (2001)MEGHEG

MEG / 50 ks simulation

Jimenez−Garate XRB 02

Centrally Illuminated AccretionDisk Atmosphere and Corona

Narrow Line Emission from a Disk Bulge in

4U 1822−37: X−ray pulsar, ADC, Porb= 5.6 hr

Comparison with Spectral Data

Corona

Hot atmosphere

Photosphereand warm atmosphere

Opticallythick disk

Dippers

No lines

i~60°°

i~75°°

i~80°°

Partial eclipses &coronal sources

Broad lines

Weaker, narrow lines

i~60°°

i~75°°

i~80°°Broader lines

Dips & total eclipses

Jimenez−Garate XRB 02

Centrally Illuminated AccretionDisk Atmosphere and Corona

Inclination Dependenceof X−ray Recombination Emission

Lines from X−raypulsar disks?

Conclusions

Jimenez−Garate XRB 02

Strong Theoretical Evidence for Accretion Disk Atmosphereand Corona present in 0.1−1Ledd neutron star LMXB

Strong Observational Evidence for ’Thick’ Diskin neutron star LMXB

Plasma Diagnostics probe Atmosphere Te,ne

Atmosphere thickened by irradiation (feedback)

Strong Inclination Dependence of X−ray Recombination Emission

Line profiles probe radial Atmosperic Structure

Weak Coupling between Atmosphere and Disk!

Future Work

Jimenez−Garate XRB 02

Eclipsing Dippers EXO 0748−676, Hercules X−1 (Emission & Transmission Spectroscopy)

LMXB dipper 4U1254−690 (Disk Emission search)

Line Transfer and Relativistic Compton Scattering(Monte Carlo)

Black Hole Accretion Disks

Observations:

Theory:

Collaborators: Duane Liedahl, Chris Mauche (LLNL),John Raymond (CfA)