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

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

pre-Chandra... 'super-Eddington'tentatively '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) ULXs: What do we know about them ?  existence of ULXs established: L X > 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) post-Chandra...

if L X > erg/s and L X < L edd = 2x10 39 (M/10M solar ) erg/s ===> M BH > 50 M solar : accretion onto IMBH OR if M > M edd (e.g., because of thermal-timescale mass transfer) ===> super-Eddington mass transfer that possibly leads to beaming and anisotropic emission L x true = L X * (beaming fraction) < L X ULXs: What is their nature ?..

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

Q : Can the long-term behavior of X-ray emission observational diagnostic ? 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 ?

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 mass and  evolutionary stage (or orbital period) and is rather insensitive to the BH mass in the MT sequence used to calculate MT rate …

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

Minimum BH mass required for transient behavior VK, Henninger, Ivanova, King 2003 orbital period MT rate minimum BH mass M BH = 1000 M solar M donor = 20 M solar BGB ZAMS

? Q : Does M BH,min depend on M BH in the MT sequence ? VK, Henninger, Ivanova, King 2003 M donor = 20 M solar M BH = 1000 M solar No ! M BH = 10 M solar M donor = 10 M solar M BH = 1000 M solar M BH = 10 M solar

Q : Can the long-term behavior of X-ray emission observational diagnostic ? be used as an observational diagnostic ? VK, Henninger, Ivanova, King 2003 For stellar donors more massive than ~5M solar, M BH,min for transient behavior is in excess of M solar for % 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. A: Yes ! in young (<~10 8 yr) stellar pops relevant to ULXs

Q : Can an IMBH acquire a stellar companion in a ? young cluster that will fill its Roche lobe ? 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

IMBH dynamics (preliminary …) M BH = 500 M solar T ev = 100 Myr n = 10 4 pc -3  = 5 km/s Ivanova, VK, Belczynski 2003

IMBH dynamics (preliminary …) M BH = 500 M solar T ev = 100 Myr n = 10 4 pc -3  = 5 km/s Ivanova, VK, Belczynski 2003 initial final

IMBH dynamics (preliminary …) M BH = 500 M solar T ev = 100 Myr n = 10 4 pc -3  = 5 km/s Ivanova, VK, Belczynski 2003 initial final RLO at ZAMS RLO at EMS RLO at R max hard-soft boundary

IMBH dynamics (preliminary …) M BH = 500 M solar T ev = 100 Myr n = 10 4 pc -3  = 5 km/s Ivanova, VK, Belczynski 2003 initial final RLO at ZAMS RLO at EMS RLO at R max hard-soft boundary X-ray

IMBH dynamics (preliminary …) M BH = 500 M solar T ev = 100 Myr n = 10 4 pc -3  = 5 km/s Ivanova, VK, Belczynski 2003 different Monte Carlo realizations

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 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 ?

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

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

Example case: GRO J Proper motion measured by Mirabel et al D = 3.2 kpc orbit does not extend beyond pc away from the Galactic plane

Example case: GRO J Mass transfer sequences must satisfy constraints on current H-R position of the donor and … Initial values: M BH M donor P orb (M o ) (M o ) (d)

current BH mass current donor mass current orbital period M BH M donor P orb (M o ) (M o ) (d) Mass transfer sequences must also satisfy constraints on current BH and donor masses and most importantly orbital period Example case: GRO J time since BH formation: ~900Myr

Example case: GRO J Constraint on BH-binary age ---> V CM = km/s

Example case: GRO J Use V CM, M BH, M donor, and A orb (or P orb ) at BH birth to constrain A orb just before as well as the BH-progenitor mass and the possible BH kick magnitude

BH kick magnitude BH progenitor mass from core simulations and stellar models: the progenitor of a 4.4M solar BH is a 4.8M solar He-star (Fryer & VK 1997) BH kick magnitude necessary ! most likely: km/s Example case: GRO J

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

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

Standard Scenario: BHs quickly concentrate in GC core BHs quickly concentrate in GC core (mass segregation) (mass segregation) BHs decouple dynamically from GC BHs decouple dynamically from GC on ~ 10 8 yr timescale (Spitzer instability) on ~ 10 8 yr timescale (Spitzer instability) BHs get ejected through interactions BHs get ejected through interactions on ~ 10 9 yr timescale (evaporation) on ~ 10 9 yr timescale (evaporation) ~ 1 BH left in GC core today ~ 1 BH left in GC core today  Sometimes: growth to IMBH through successive mergers through successive mergers

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

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