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E f f e c t s o f g e o me t r y a n d ma s s a c c r e t i o n r a t e o n t h e r ma l s p e c t r a o f U L X s o u r c e s Mi c h a l B u r s a Arbatax, September 22, 2016

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SLIDE 1

Arbatax, September 22, 2016

E f f e c t s

  • f

g e

  • me

t r y a n d ma s s a c c r e t i

  • n

r a t e

  • n

t h e r ma l s p e c t r a

  • f

U L X s

  • u

r c e s

Mi c h a l B u r s a

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SLIDE 2

Motivation

Spectral modeling of ULXs:

  • most often a model with disk+pl or

disk+th_comp is used

  • in place of a disk model we can see

DISKBB, DISKPN, KERRBB, BHSPEC, GRAD, etc

  • all of the listed disk models are based
  • n thin disk model, which is inaccurate

for L > 0.3 LEdd

  • BUT, such a modelling tends to give

incorrect values for BH masses and for accretion rate (luminosity)

  • how much wrong?

(Gladstone et al. 2009)

slide-3
SLIDE 3

Motivation

Spectral modeling of ULXs:

  • most often a model with disk+pl or

disk+th_comp is used

  • in place of a disk model we can see

DISKBB, DISKPN, KERRBB, BHSPEC, GRAD, etc

  • all of the listed disk models are based
  • n thin disk model, which is inaccurate

for L > 0.3 LEdd

  • BUT, such a modelling tends to give

incorrect values for BH masses and for accretion rate (luminosity)

  • how much wrong?

(Gladstone et al. 2009)

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SLIDE 4

Spectral model based on slim disk model

Numerical simulations

Credit: A. Sadowski

Analytical solutions

Sadowski+2009

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SLIDE 5

Spectral softening: advection & geometry

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SLIDE 6

ULX spectra (a=0.00, i=30°)

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SLIDE 7

ULX spectra (a=0.00, i=30°)

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SLIDE 8

ULX spectra (a=0.00, i=30°)

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SLIDE 9

ULX spectra (a=0.00, i=30°)

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SLIDE 10

ULX spectra (a=0.00, i=30°)

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SLIDE 11

ULX spectra (a=0.00, i=60°)

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SLIDE 12

ULX spectra (a=0.00, i=60°)

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SLIDE 13

ULX spectra (a=0.00, i=60°)

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SLIDE 14

ULX spectra (a=0.00, i=60°)

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SLIDE 15

ULX spectra (a=0.00, i=60°)

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SLIDE 16

ULX spectra (a=0.00, i=60°)

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SLIDE 17

Luminosity vs. Temperature

L-T plot in super-eddington case:

  • standard (thin) disks follow L~T4 relation
  • advection and obscuration effects cause

signifjcant deviations from that relation in super-Eddington regime

  • the effect is strongly inclination dependent
  • observed luminosity can stay arround eddington

even if mass accretion rate is >>1

  • that has implications for spectral modeling

inc=0°

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SLIDE 18

Luminosity vs. Temperature

L-T plot in super-eddington case:

  • standard (thin) disks follow L~T4 relation
  • advection and obscuration effects cause

signifjcant deviations from that relation in super-Eddington regime

  • the effect is strongly inclination dependent
  • observed luminosity can stay arround eddington

even if mass accretion rate is >>1

  • that has implications for spectral modeling

inc=0°

slide-19
SLIDE 19

Luminosity vs. Temperature

L-T plot in super-eddington case:

  • standard (thin) disks follow L~T4 relation
  • advection and obscuration effects cause

signifjcant deviations from that relation in super-Eddington regime

  • the effect is strongly inclination dependent
  • observed luminosity can stay arround eddington

even if mass accretion rate is >>1

  • that has implications for spectral modeling

inc=0°

slide-20
SLIDE 20

Luminosity vs. Temperature

L-T plot in super-eddington case:

  • standard (thin) disks follow L~T4 relation
  • advection and obscuration effects cause

signifjcant deviations from that relation in super-Eddington regime

  • the effect is strongly inclination dependent
  • observed luminosity can stay arround eddington

even if mass accretion rate is >>1

  • that has implications for spectral modeling

inc=70° inc=0°

slide-21
SLIDE 21

Luminosity vs. Temperature

L-T plot in super-eddington case:

  • standard (thin) disks follow L~T4 relation
  • advection and obscuration effects cause

signifjcant deviations from that relation in super-Eddington regime

  • the effect is strongly inclination dependent
  • observed luminosity can stay arround eddington

even if mass accretion rate is >>1

  • that has implications for spectral modeling

Poutanen+2007

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SLIDE 22

0.1 0.5 accretion rate [ ˙ M Edd] 10 15 20 25 30 35 40 BH mass [M ⊙] 1 5 10

inc=30° inc=60°

Mass estimates from thermal spectra

SLIMULX spectra fjtted with DISKBB

  • simulated SLIMULX spectra are fjtted

with a thin disk model (DISKBB) and mass is obtained from the fjt

  • at low Mdot, the fjt recovers the original

mass, but at high Mdot, mass is much larger

  • it appears to be quite tricky to estimate

the ULX source parameters using thin disk models if the disk is strongly radiation pressure dominated

  • masses may be largely overestimated
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SLIDE 23

Limitations

Model limitations

  • vertical equilibrium treatment (Q~R-3 instead of Q~[R2+z2]-3/2)

limits H/R to ~1

  • constant mass accretion rate, the solution misses transfer of gas to outfmow
  • refmection of radiation in the inner funnel; beaming
  • feadback from radiation on the disk structure and shape
  • hardening factor treatment

Fixes

  • use insight from numerical simulations to apply scaling to the analytic model,

possibly with accounting for comptonization in the outfmowing wind

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SLIDE 24

Summary

  • slimulx model can be used fjt BHB UXL spectra
  • the model spectra reproduce a turnover in L-T track
  • compared to thin disk models, it gives lower BH masses