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Possible Connection between ULXs and SXTs. Chang-Hwan Lee Seoul National University. 2002.11.29 KIAS. Why do we consider Accretion in NS/BH ? Eddington Luminosity & Mass Accretion Rate Ultraluminous X-ray Sources (ULXs) ULXs from Soft X-ray Transients Conclusion.

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Presentation Transcript
slide1

Possible Connection between

ULXs and SXTs

Chang-Hwan Lee

Seoul National University

2002.11.29 KIAS

slide2

Why do we consider Accretion in NS/BH ?

  • Eddington Luminosity & Mass Accretion Rate
  • Ultraluminous X-ray Sources (ULXs)
  • ULXs from Soft X-ray Transients
  • Conclusion
slide3

Why do we consider accretion in NS/BH ?

  • Accretion by Fallback after SN Explosion
    • SN 1987A : NS/BH was covered by material for a few years
    • Numerical Calculation [a few solar mass can accrete]
  • Accretion by Companion Star
    • Missing Ingredient in SN explosion
    • Rotation
    • Binary provide natural rotation by tidal interaction
    • NS/BH accrete matter from companion
slide4

Eddington Luminosity & Mass Accretion Rate

LEdd = 1.3 x 1038 (M/Msun) erg/s

Spherical Accretion

L = f GMdM/R

If f=1 & L=LEdd dM = dMEdd

slide5

Ultra Luminous X-Ray Sources

LEdd = 1.3 x 1038 (M/Msun) ergs/s

slide6

Ultraluminous X-ray Sources

  • Original Claim
    • Discovery of Intermediate Mass BH ( > 100 Msun )
    • cf) dominant BH : stellar => 10 Msun
    • galactic => 106-109 Msun
  • Problem
    • Too Many of them
    • Hard to evolve them
  • Question: Then, what are they ?
slide7

Soft X-ray Transients

15 Msun

10 Msun

Q) How to evolve ?

slide8

C

B

A

slide9

HMBH

NS/LMBH

slide10

HMBH formation in Case C

HMBH

NS LMBH

Current 1915+105 (108 Rsun)

slide11

Pre-Explosion Properties

ApJ 575 (2002) 996

V4641 & 1915

slide12

Conservative Mass Transfer

V4641 Sgr

Data: 33.5 days

2.817 days

GRS 1915+105

Consistent within error range

slide13

Soft X-ray Transients

33day

14 Msun + 2 Msun

3day

15 Msun

9.5 Msun + 6.5 Msun

10 Msun

1915+105

V4641 Sgr

Beauty of Simple Physical Laws !

slide15

SXTs (10 Msun BH) with evolved companions

=> 100 Eddington Mass Accretion Rate

LLimit = N LEdd

N = O(10) : Porous Disk [white dwarf]

=> 10 Msun BH can explain the ULXs !

LLimit = f GMdM/R

f = O(0.1) : Photon Trapping

dM =100 dMEdd

10 Msun BH can have 10 LEdd & 100 dMEdd

slide16

Ultra Luminous X-Ray Sources

LLimit = 10 LEdd= 13 x 1038 (M/Msun) ergs/s

slide17

SXTs with initial heavy companion

ULXs (0 degree)

L > 10 LEdd

GRS 1915+105

(70 degree)

L = LEdd

10 Msun BH + 6 Msun Companion

slide18

Conclusion

  • ULXs may be BH binaries similar to SXTs in our Galaxy.
  • LLimit = 10 LEdd
  • We predict efficiency f=O(0.1) with photon trapping based on the evolution from V4641 Sgr to 1915+105.
  • dM = 100 dMEdd