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Accreting Black Holes in the Milky Way and Beyond …

Accreting Black Holes in the Milky Way and Beyond …. Vicky Kalogera Physics & Astronomy Dept with Mike Henninger Natasha Ivanova Bart Willems. In this talk :. Ultra Luminous X-ray sources (ULXs): what are they ? where are they found ? their nature: IMBH or anisotropic emission ?

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Accreting Black Holes in the Milky Way and Beyond …

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  1. Accreting Black Holesin the Milky Way and Beyond … Vicky Kalogera Physics & Astronomy Dept with Mike Henninger Natasha Ivanova Bart Willems

  2. In this talk : • Ultra Luminous X-ray sources (ULXs): • what are they ? • where are they found ? • their nature: IMBH or anisotropic emission ? • Transient behavior: an observational diagnostic • Galactic Black-Hole X-ray binaries: • Current measurements constrain their evolutionary history • Black-hole kicks and progenitors • BH X-ray binaries in Globular Clusters: • Why none observed so far ?

  3. pre-Chandra ... 'super-Eddington' sources tentatively identified (e.g., Fabbiano 1995) • some identified as X-ray pulsars (hence beaming) • most often questions of source confusion (lack of variability) post-Chandra ... • existence ofULXsestablished: LX > 1039-40 erg/s • mostly found in young stellar environments (<~ 100 Myr) • their nature still not well understood although many hints have been discussed … (e.g., Miller & Colbert 2003) ULXs: What do we know about them ?

  4. ULXs: What is their nature ? if LX > 1040 erg/s and LX < Ledd = 2x1039 (M/10Msolar) erg/s ===> MBH > 50 Msolar : accretion onto IMBH OR if M > Medd (e.g., because of thermal-timescale mass transfer) ===> super-Eddington mass transfer that possibly leads to beaming and anisotropic emission Lxtrue = LX * (beaming fraction) < LX . .

  5. ULXs: IMBH possibility has important implications for: • stellar dynamics (evolution of massive stars and binary black holes in clusters) and possibly Pop III stars • seeds for super-massive black hole formation • gravitational-wave detection

  6. Q : Can the long-term behavior of X-ray emission be used as an observational diagnostic ? VK, Henninger, Ivanova, King 2003 In the context of the thermal-viscous disk instability, an X-ray binary is transient if M is below a critical value The development of anisotropic emission (beaming) has been connected to thermal-timescale MT and super-Eddington, i.e., high, MT rates ---> stable disk How about accreting IMBH binaries in young stellar environments ? ---> are they stable or are they transient?

  7. Q : What is the minimum BH mass required for the development of transient behavior ? VK, Henninger, Ivanova, King 2003 Critical mass transfer rate for transient behavior: Minimum BH mass required for transient behavior: • MT rate depends primarily on the • donor massand • evolutionary stage (or orbital period) • and is ratherinsensitive to the BH mass • in the MT sequence used to calculate MT rate …

  8. Q : What is the minimum BH mass required for the development of transient behavior ? VK, Henninger, Ivanova, King 2003 • Plan: • Use numerical MT sequences to examine • analytical expectations • Derive MBH,min for a wide range of stellar parameters • Does MBH,min lie consistently in the IM or stellar-mass range ? transience: diagnostic

  9. Minimum BH mass required for transient behavior MBH = 1000 Msolar Mdonor = 20 Msolar BGB orbital period ZAMS MT rate VK, Henninger, Ivanova, King 2003 minimum BH mass

  10. Mdonor = 10 Msolar MBH = 1000 Msolar MBH = 10 Msolar Q : Does MBH,min depend on MBH in the MT sequence ? No ! Mdonor = 20 Msolar MBH = 1000 Msolar MBH = 10 Msolar VK, Henninger, Ivanova, King 2003

  11. Q : Can the long-term behavior of X-ray emission be used as an observational diagnostic ? VK, Henninger, Ivanova, King 2003 A: Yes ! in young (<~108 yr) stellar popsrelevant to ULXs • For stellar donors more massive than ~5Msolar, MBH,min for transient behavior is in excess of 50-100Msolar for 90-100% of the MT duration. • In young stellar pops massive stars dominate the central regions due to mass segregation. • Less massive captured IMBH companions typically do not have enough time to fill their Roche lobes.

  12. IMBH could form through successive collisions and mergers of ordinary massive stars in dense star clusters (timescale ~1-3Myr) (Sanders 1970; Quinlan & Shapiro 1990; Portegies Zwart & McMillan 2001; Ebisuzaki et al. 2001; Gurkan et al. 2003) After formation an IMBH could appear as an X-ray source, if an acquired stellar companion goes through Roche lobe overflow Q : Can an IMBH acquire a stellar companion in a young cluster that will fill its Roche lobe ?

  13. IMBH dynamics (preliminary …) Ivanova, VK, Belczynski 2003 MBH = 500 Msolar Tev = 100 Myr n = 104 pc-3 s = 5 km/s

  14. IMBH dynamics (preliminary …) Ivanova, VK, Belczynski 2003 initial final MBH = 500 Msolar Tev = 100 Myr n = 104 pc-3 s = 5 km/s

  15. IMBH dynamics (preliminary …) Ivanova, VK, Belczynski 2003 hard-soft boundary initial final MBH = 500 Msolar Tev = 100 Myr n = 104 pc-3 s = 5 km/s RLO at Rmax RLO at EMS RLO at ZAMS

  16. IMBH dynamics (preliminary …) Ivanova, VK, Belczynski 2003 hard-soft boundary initial final MBH = 500 Msolar Tev = 100 Myr n = 104 pc-3 s = 5 km/s X-ray RLO at Rmax RLO at EMS RLO at ZAMS

  17. IMBH dynamics (preliminary …) Ivanova, VK, Belczynski 2003 MBH = 500 Msolar Tev = 100 Myr n = 104 pc-3 s = 5 km/s different Monte Carlo realizations

  18. BH formation: some open questions … • What is the mass relation between progenitors and BHs ? • Are asymmetric birth kicks imparted to BHs ? • How do their magnitudes compare to NS kicks ? • Observed sample of BH X-ray binaries: • Growing in number • New exciting measurements of proper motion give us with radial velocity unique information on kinematic history

  19. primordial binary How do BH X-ray binaries form ? Common Envelope: orbital contraction and mass loss BH formation X-ray binary at Roche-lobe overflow courtesy Sky & Telescope Feb 2003 issue

  20. Use ALL observational constraints and measurements: Current: BH and donor mass donor position on the H-R diagram orbital period 3-D velocity Plan: Follow the Galactic motion backwards in time Derive Vcm as a function of time Identify at least one MT sequence that satisfies ALL observables: obtain time of BH formation and post-collapse properties Analyze collapse dynamics: constrain BH XRB progenitor

  21. Example case: GRO J1655-40 Proper motion measured by Mirabel et al. 2002 D = 3.2 kpc orbit does not extend beyond 70-100pc away from the Galactic plane

  22. Example case: GRO J1655-40 Initial values: MBH Mdonor Porb (Mo) (Mo) (d) 4.4 2.45 0.56 4.4 2.45 1.4 4.4 2.45 1.8 5.4 2.0 1.5 Mass transfer sequences must satisfy constraints on current H-R position of the donor and …

  23. Example case: GRO J1655-40 Mass transfer sequences must also satisfy constraints on current BH and donor masses and most importantly orbital period current BH mass MBH Mdonor Porb (Mo) (Mo) (d) 4.4 2.451.4 4.4 2.45 1.8 current donor mass current orbital period time since BH formation: ~900Myr

  24. Example case: GRO J1655-40 Constraint on BH-binary age ---> VCM = 87-89 km/s

  25. Example case: GRO J1655-40 Use VCM, MBH, Mdonor, and Aorb (or Porb) at BH birth to constrain Aorb just before as well as the BH-progenitor mass and the possible BH kick magnitude

  26. Example case: GRO J1655-40 from core simulations and stellar models: the progenitor of a 4.4Msolar BH is a 4.8Msolar He-star (Fryer & VK 1997) BH progenitor mass BH kick magnitude necessary ! most likely: 125 - 150 km/s BH kick magnitude

  27. To follow: > Several other systems to be analyzed > Core-collapse runs and SN explosion constraints (with C. Fryer) > Are BH kick magnitudes correlated with either BH mass or mass loss at BH formation ? > Comparison with NS systems

  28. Black Holes in Globular Clusters • Expect ~ 10-4 - 10-3 N BH from evolution of N stars with Salpeter-like IMF • N ~ 105 - 106 in GC GC should have many BH… • Where are they?? • BH XRBs, ULXs ? • Ejected, as binaries, GW sources ?

  29. Standard Scenario: • BHs quickly concentrate in GC core (mass segregation) • BHs decouple dynamically from GC on ~ 108 yr timescale (Spitzer instability) • BHs get ejected through interactions on ~ 109 yr timescale (evaporation) • ~ 1 BH left in GC core today • Sometimes: growth to IMBH • through successive mergers

  30. Observability of BH XRBs • Remaining ~ 1 BH is very likely to acquire a companion through either: • Exchange interaction • Tidal capture (?) • Duty cycle of resulting XRB is: • Very low (<< 10-3) for post-exchange binaries (wide) • Very high ( ~ 1) for tidal capture binaries (conflicts with observations for Galactic GC !) (Kalogera, King, & Rasio 2003, ApJL, in press, astro-ph/0308485)

  31. (O’Leary, Fregeau, Ivanova, & Rasio 2003)

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