theoretical studies of x-ray binaries in clusters

Theoretical Studies of X-Ray Binaries in Clusters

Vicky Kalogera

MODEST-6

ExtraGalactic only…ExtraGalactic only…

In this review: Do IMBH in clusters form observable ULXs ?

Do Super Star Clusters form High-Mass XRBs ?

What is the role of SSCs in determining the X-ray luminosity functions of Starbursts ?

YOUNGYOUNG

OLDOLD

Do LMXBs in Ellipticals form in Globular Clustersexclusively ?

Does the galactic field contribute at all ?

Why are red GCs better LMXB hosts than blue GCs?

Do accreting IMBH in clusters form observable ULXs ?

Hopman, Portegies Zwart, Alexander 2004: YESIMBH binary: through tidal capture (TC) of MS companions

ULX phase duration: > 10Myr

Blecha, Ivanova, Kalogera, et al. 2005: NOT LIKELYIMBH binary: through exchanges with stellar binaries

ULX phase duration: < 0.1Myr


Hopman, Portegies Zwart, Alexander 2004: YES through TC

Most optimistic assumptions for TC survival of MS stars: “hot squeezars” and ETC x Porb ~ LEdd

Analytical estimate of TC rate for 1,000Mo IMBHfor ANY orbital period

Mass Transfer and LX calculation for isolated IMBH binaries with 5-15Mo MS donors

No dynamical interactions and evolution included

ULX phase duration per IMBH binary: >10MyrFraction of Clusters with IMBH-MS ULX: 30-50%


Blecha, Ivanova, Kalogera, et al. 2005: NOT LIKELY

Cluster core simulations with full binary evolution and dynamical interactions: TC, exchanges, disruptions, collisions

(N. Ivanova’s talk from Monday’s morning session) 100-500Mo IMBH, 100Myr old clusters, Trc < 30Myr

Average ULX phase duration per cluster: <0.1Myr

Time fraction with IMBH binary: > 50% Time fraction with Mass-Transfer: ~1-3% MS donors dominate by time;

Post-MS donors dominate by number Fraction of Mass-Transfer time as a ULX: ~2%

IMBH Companions

Mass Mass distributiondistribution

Orbital separation Orbital separation distributiondistribution

Blecha, Ivanova, Kalogera, et al. 2005

Kaaret et al. 2004

• Lx ≥ (0.5-3)x1036 erg/s

Distribution of point X-ray sources

< 1 XRB per cluster!


Kaaret et al. 2004

• Lx ≥ 5x1035 erg/s

• XRBs closely associated with star clusters• Median distance ~30-100 pc

< 1 XRB per cluster!M82N5253

N1569

50%

Is this all due to Is this all due to Supernova Kicks ?Supernova Kicks ?


• cluster mass: ~5x104 Mo

• LX > 5x1035 erg/s• average of 1,000 cluster simulations

• Significant age dependence

• < 1 XRB per cluster

Models: Population Syntheses of XRBs and Kinematic Orbit Evolution in Cluster Potential

Sepinsky, Kalogera, & Belczynski 2005


Distance from Cluster Center [pc]

YES!XRB models without cluster dynamics appear

in agreement with observations

Mean XRB number per SSC < 1 and spatial distribution: M < 105 Mo and 10-50Myr or more massive and ~50Myr

Supernova kicks: eject XRBs @ D > 10pc especially for M < 105 Mo


LMXB origin in Ellipticals: Clusters and/or Field ?

Bildsten & Deloye 2004: NS Ultra-Compact Binaries from Clusters Matches observed XLF slope below BREAK at ~5x1038 erg/s Formation rate: 1/2Myr per 107Mo of GCs and this

matches cumulative #Ucs for continuous UC formation due to dynamical interactions (Ivanova & Rasio 2004)

and observed #MSPc in Galactic GCs

prediction: search for orbital periods of 5-10min! questions: MW has H-rich donors in GCs

what about above the BREAK ?


Bildsten & Deloye 2004: NS Ultra-Compact Binaries from Clusters

Juett 2005: Ellipticals’ Field Must ContributeReason: Fraction of GC-LMXBs depends on SN

Issues with incompatible coverage for definition of

fLMXB,GC and SN ?


Irwin 2005: Ellipticals’ Field Must ContributeReason: non-zero y-intercept of LX/LB vs. SN (ASN+B, B<>0 @8


Juett 2005: Ellipticals’ Field Must ContributeReason: Fraction of GC-LMXBs depends on SN

Not due to: large-scale GC disruptionor variations in red/blue GC ratio


Irwin 2005: Ellipticals’ Field Must Contribute


Juett 2005: Ellipticals’ Field Must Contribute

Ivanova & Kalogera 2005: Brightest are BH LMXBs from FieldSources with 5x1038 < LX < fewx1039 erg/s too bright for NS accretorBH LMXBs not expected in GCs, (Kalogera, King, & Rasio 2004) but are expected in the Field as BH transients

If Loutburst ~ Ledd : XLF slope above BREAK is a footprint of BH mass spectrum

Current Lmax ~ 2x1039 erg/simplies max BH mass of 15-20Mo

consistent with stellar evolution


Irwin 2005: Ellipticals’ Field Must Contribute


Juett 2005: Ellipticals’ Field Must Contribute

Ivanova & Kalogera 2005: Brightest are BH LMXBs from Field

Consistent answer appears to be: Both Clusters & Field

BUT: Irwin considers sources below the BREAK: mixed

Juett considers all sources: mixedB&D can explain all sources below the BREAK

as coming from Clusters

I&K agree (based on pop-syn models) and propose Field contribution only for sources above the BREAK …

Why are Red Clusters more likely (by ~3) to host LMXBs than Blue Clusters?

Maccarone, Kundu, & Zepf 2004: Z-dependence of Irradiation-Induced Winds

In Blue, Metal-Poor GCs donors have stronger IIWs (less line-cooling)---> shorter LMXB lifetimes ---> lower LMXB numbers

Number ratio comes to 2.5-3.5!Also accounts for:

harder LMXB spectra in Blue, Metal-Poor Clusters

Prediction:Should see monotonic # dependence on Z And account for LMC vs. MW observations



Ivanova 2005: Z-dependence of Magnetic Braking A.M. LossIn Blue, Metal-poor GCs MS donors w/ 0.85-1.25Mo have no outer convective zone ---> no MB ---> harder to start MTEven if MT starts, NS-MS LMXBs are transients (hard to detect)

NS-MS LMXBs in Red, Metal-rich GCs are easier to form and have some bright phase

Estimate of formation rate of Bright NS-MS LMXBs in

Metal-Rich GCs agrees with obs.



Ivanova 2005: Z-dependence of Magnetic Braking A.M. Loss

Not clear (to me!) which of the two is more realistic Any thoughts ?

Both deal with NS-LMXBs and MS donors -

How are these connected to B&D results about NS Ultra-compacts with WD companions ?

theoretical studies of x-ray binaries in clusters

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