Transcript X-ray Binaries in Nearby Galaxies

Accreting Compact Objects
in Nearby Galaxies
Vicky Kalogera
@ Michigan State University, Nov 8, 2006
Chandra:
a NASA ‘Great’ Observatory
Launch: 1999
Energy range:
0.5-10keV
Angular Resolution:
~ 0.5 arcsecond
Chandra:
the joys of high angular resolution
• 51 point sources in 30 arcmin with ROSAT
• 110 point sources in 8 arcmin with Chandra ACIS
M101 ROSAT HRI
detected sources
(Wang et al. 1999)
M101 Chandra
detected Sources
(Pence et al. 2001)
X-Ray Binaries
Point, variable on short time scale X-ray sources
Neutron Stars or Black Holes
Accreting from binary companions
X-Ray Binaries
LMXB
LMXB:
Science@NASA Image
CXC Image Archive
low-mass donor, ~1 Mo
Roche-lobe overflow
old, 108-9 yr
HMXB:
HMXB
high-mass donor, 5-10Mo
stellar wind accretion
young, 106-7 yr
X-Ray Binary Populations: pre-Chandra
the Milky Way:
first discovered in our Galaxy
~ 100 known 'low-mass' XRBs
~ 30 known 'high-mass' XRBs
long-standing problem with distance estimates:
very hard to study the X-ray luminosity function
and spatial distribution
other properties, e.g., orbital period, donor masses
known only for a few systems
X-Ray Binary Populations: pre-Chandra
other galaxies:
discovered in the LMC/SMC, M31,
and another ~15 galaxies (all spirals)
a handful of point X-ray sources (< 10)
long-standing problems with
low angular resolution and source confusion
> XLF reliably constructed only for M31 and M101
> 'super-Eddington' sources were tentatively
identified
X-Ray Binary Populations: post-Chandra
other galaxies:
more than ~100 galaxies observed
they cover a wide range of galaxy types
and star-formation histories
~ 10-100 point sources in each:
population studies become feasible
known sample distance: great advantage for
studies of X-ray luminosity functions
and spatial distributions
Population Modeling
Current status: observationally-driven
Chandra observations provide an excellent challenge
and opportunity for progress in the study of global
XRB population properties.
Population Synthesis Calculations: necessary
Basic Concept of Statistical Description:
evolution of an ensemble of binary and
single stars with focus on XRB formation and
their evolution through the X-ray phase.
How do
X-ray binaries
form ?
primordial binary
Common Envelope:
orbital contraction
and mass loss
NS or BH formation
courtesy
Sky & Telescope
Feb 2003 issue
X-ray binary
at Roche-lobe
overflow
Population Synthesis Elements
Star formation conditions:
> time and duration, metallicity, IMF, binary properties
Population Synthesis Elements
Star formation conditions:
> time and duration, metallicity, IMF, binary properties
Modeling of single and binary evolution
> mass, radius, core mass, wind mass loss
> orbital evolution: e.g., tidal synchronization and
circularization, mass loss, mass transfer
> mass transfer modeling:
stable driven by nuclear evolution or angular momentum loss
thermally unstable or dynamically unstable
> compact object formation: masses and supernova kicks
> X-ray phase: evolution of mass-transfer rate
and X-ray luminosity
Population Synthesis Elements
Star formation conditions:
> time and duration, metallicity, IMF, binary properties
Modeling of single and binary evolution
> mass, radius, core mass, wind mass loss
> orbital evolution: e.g., tidal synchronization and
circularization, mass loss, mass transfer
> mass transfer modeling:
stable driven by nuclear evolution or angular momentum loss
thermally unstable or dynamically unstable
> compact object formation: masses and supernova kicks
> X-ray phase: evolution of mass-transfer rate
and X-ray luminosity
Population Synthesis Elements
Star formation conditions:
> time and duration, metallicity, IMF, binary properties
Modeling of single and binary evolution
> mass, radius, core mass, wind mass loss
> orbital evolution: e.g., tidal synchronization and
circularization, mass loss, mass transfer
> mass transfer modeling:
stable driven by nuclear evolution or angular momentum loss
thermally unstable or dynamically unstable
> compact object formation: masses and supernova kicks
> X-ray phase: evolution of mass-transfer rate
and X-ray luminosity
Population Synthesis Elements
Star formation conditions:
> time and duration, metallicity, IMF, binary properties
Modeling of single and binary evolution
> mass, radius, core mass, wind mass loss
> orbital evolution: e.g., tidal synchronization and
circularization, mass loss, mass transfer
> mass transfer modeling:
stable driven by nuclear evolution or angular momentum loss
thermally unstable or dynamically unstable
> compact object formation: masses and supernova kicks
> X-ray phase: evolution of mass-transfer rate
and X-ray luminosity
Population Synthesis Elements
Star formation conditions:
> time and duration, metallicity, IMF, binary properties
Modeling of single and binary evolution
> mass, radius, core mass, wind mass loss
> orbital evolution: e.g., tidal synchronization and
circularization, mass loss, mass transfer
> mass transfer modeling:
stable driven by nuclear evolution or angular momentum loss
thermally unstable or dynamically unstable
> compact object formation: masses and supernova kicks
> X-ray phase: evolution of mass-transfer rate
and X-ray luminosity
Population Synthesis Elements
Star formation conditions:
> time and duration, metallicity, IMF, binary properties
Modeling of single and binary evolution
> mass, radius, core mass, wind mass loss
> orbital evolution: e.g., tidal synchronization and
circularization, mass loss, mass transfer
population
> massOur
transfer
modeling:synthesis code:
stable driven by nuclear
evolution or angular momentum loss
StarTrack
thermally unstable
or dynamically
unstable
Belcynski
et al. 2006
> compact object formation: masses and supernova kicks
> X-ray phase: evolution of mass-transfer rate
and X-ray luminosity
In this talk …
- some of the puzzles Are HMXBs connected to Super Star Clusters ?
What determines the shape of
X-Ray Luminosity Functions (XLF) ?
What is the nature of Ultra-Luminous X-ray Sources
(ULX) ?
Super Star Clusters
(SSCs)
• Compact, young analog to globular clusters
• Found frequently in starburst environments
• Masses range from ~104 to ~106 Mo
•
Ages range from a few to tens of Myr
Distribution of X-Ray point sources
Kaaret et al. 2004
• Lx ≥ (0.5-3)x1036 erg/s
< 1 XRB per cluster!
Distribution of X-Ray point sources
Kaaret et al. 2004
• XRBs closely associated
with star clusters
• Median distance ~30-100 pc
• Lx ≥ 5x1035
Is this all due to
erg/sSupernova Kicks ?
N1569
50%
N5253
< 1 XRB per cluster!
M82
Theoretical XRB Distributions
Sepinsky et al. 2005, ApJL
Models:
Population Syntheses of XRBs and
Kinematic Orbit Evolution in Cluster Potential
• cluster mass: ~5x104 Mo
• LX > 5x1035 erg/s
• average of 1,000 cluster
simulations
• Significant age dependence
• < 1 XRB per cluster
1
10
100
1000
Distance from Cluster Center [pc]
HMXBs and SSCs
XRB models without cluster dynamics appear
in agreement with observations

or
M < 105 Mo and 10-50Myr
more massive and ~50Myr
Supernova kicks: eject XRBs @ D > 10pc
especially for M < 105 Mo
Chandra X-Ray Binary Populations
» Starbursts: dominated by recent/ongoing
burst of star formation,
and young HMXBs
» Spirals:
mix of ages and metallicities
mix of LMXBs and HMXBs
» Ellipticals:
clean samples of LMXBs
X-Ray Luminosity Functions
M81
Tennant et al. 2001
Characterizing
XLFs:
power-laws,
slopes,
breaks …
X-Ray Luminosity Functions
M81
Old populations:
flatter
(slopes: -0.8 to -0.4)
Young/Mixed
populations:
steeper
(slopes: up to
-1.0 or -1.5)
Tennant et al. 2001
NGC 1569
courtesy
Schirmer, HST
courtesy
Martin,
CXC,NOAO
(post-)starburst galaxy at 2.2Mpc
with well-constrained SF history:
> ~100Myr-long episode,
probably ended 5-10Myr
ago, Z ~ 0.25 Zo
> older population with
continuous SF for ~ 1.5Gyr,
Z ~ 0.004 or 0.0004,
but weaker in SFR than
recent episode by factors
of >10
Vallenari & Bomans 1996;
Greggio et al. 1998;
Aloisi et al. 2001;
Martin et al. 2002
NGC 1569
XLF modeling
Old: 1.5 Gyr
Young: 110 Myr
SFR Y/O: 20
Belczynski, VK
et al. 2004, ApJL
Hybrid of
2 populations:
 underlying old
 starburst young
Old: 1.5 Gyr
Young: 70 Myr
SFR Y/O: 20
Old: 1.3 Gyr
Young: 70 Myr
SFR Y/O: 40
XRBs in Starbursts
Current understanding of XRB formation and
evolution produces XLF properties consistent
with observations
Model XLFs can be used to constrain
star-formation properties, e.g., age and
metallicity
Shape of model XLFs appear robust against
variations of most binary evolution parameters
XLFs in Elliptical Galaxies
Summary of observations
(5+-1.6)x1038erg/s
Below 5x1038erg/s
XLF slope: 0.8+-0.2
Kim & Fabbiano 2004;
confirmed by Gilfanov 2004
Above 5x1038erg/s
XLF slope: 1.8+-0.6
Kim & Fabbiano 2004
XLF slope: 3.9-7.3
Gilfanov 2004
Maximum Lx:
2x1039 erg/s
XLFs in Elliptical Galaxies
Fabbiano et al., Kim et al. 2006
2x1036 - 6x1038 erg/s
6x1036 - 5x1038 erg/s
XLF slope: 0.9 +- 0.1
XLFs in Elliptical Galaxies
Fragos, VK, et al.
Accreting NS dominate over BH accretors
XLF - DCtr=1%
XLF - DCtr=10%
No transients
Donors of
Persistent LMXBs:
MS
very low-mass,
degenerate
He WD
Red Giant
model XLF slope: 0.9
XLFs in Elliptical Galaxies
Fragos, VK, et al.
Accreting NS dominate over BH accretors
XLF - DCtr=1%
XLF - DCtr=10%
No transients
Donors of
Persistent LMXBs:
MS
very low-mass,
degenerate
He WD
Red Giant
model XLF slope: 0.9
LMXB origin in Ellipticals: Clusters and/or Field ?
Bildsten & Deloye 2004: NS Ultra-Compact Binaries from Clusters
Analytical models of Ultra-Compacts
Matches observed XLF slope below BREAK at ~5x1038 erg/s
Persistent sources
LMXB origin in Ellipticals: Clusters and/or Field ?
Bildsten & Deloye 2004: NS Ultra-Compact Binaries from Clusters
Juett 2005:Ellipticals’ Field Must Contribute
Irwin 2005: Ellipticals’ Field Must Contribute
based on how population properties
scale with the frequency of clusters
per unit galaxy mass
LMXB origin in Ellipticals: Clusters and/or Field ?
Bildsten & Deloye 2004: NS Ultra-Compact Binaries from Clusters
Juett 2005:Ellipticals’ Field Must Contribute
Irwin 2005: Ellipticals’ Field Must Contribute
Ivanova & VK 2005: Brightest sources Field BH LMXBs
Sources with Lx > 5x1038 erg/s too bright for NS accretor
BH LMXBs not expected in GCs,
(VK, 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/s
implies max BH mass of 15-20Mo
consistent with stellar evolution
LMXB origin in Ellipticals: Clusters and/or Field ?
Bildsten & Deloye 2004: NS Ultra-Compact Binaries from Clusters
Juett 2005:Ellipticals’ Field Must Contribute
Irwin 2005: Ellipticals’ Field Must Contribute
Ivanova & VK 2005: Brightest sources are Field BH LMXBs
Fragos, VK, Belczynski, et al. 2006:NS Ultra-Compacts from Field
Matches observed XLF slope below BREAK at ~5x1038 erg/s
Persistent sources
LMXB origin in Ellipticals: Clusters and/or Field ?
Bildsten & Deloye 2004: NS Ultra-Compact Binaries from Clusters
Juett 2005:Ellipticals’ Field Must Contribute
Irwin 2005: Ellipticals’ Field Must Contribute
Ivanova & VK 2005: Brightest sources are Field BH LMXBs
Fragos, VK, Belczynski, et al. 2006:NS Ultra-Compacts from Field
NS Ultra-Compacts dominate Ellipticals’ LMXBs
Field and Cluster Ultra-Compacts: same properties
Cluster and Field XLFs very similar, as observed
Consistent answer appears to be: Both Clusters & Field
Ultra-Luminous X-ray Sources
 Single sources with LX > 1039 erg/s
 Associated with young populations
and star clusters
 What is their origin?
 Intermediate-Mass Black Holes?
(50 - 1000Mo)
 Anisotropic/Beamed XRB emission ?
Do accreting IMBH in clusters form
observable ULXs ?
Hopman, Portegies Zwart, Alexander 2004: YES
IMBH binary: through tidal capture (TC) of MS companions
ULX phase duration: > 10Myr
Blecha, Ivanova, VK, et al. 2005:
NOT LIKELY
IMBH binary: through exchanges with stellar binaries
ULX phase duration: < 0.1Myr
Do accreting IMBH in clusters form
observable ULXs ?
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 IMBH
for 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: >10Myr
Fraction of Clusters with IMBH-MS ULX:
30-50%
Do accreting IMBH in clusters form
observable ULXs ?
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
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%
Average ULX phase duration per cluster: <0.1Myr
Observational Diagnostic for ULXs
VK, Henninger, Ivanova, & King 2003
IMBH or
thermal-timescale
mass transfer with
anisotropic emission ?
Minimum accretor mass for transients
In young ( >100Myr )
stellar environments
transient behavior
is shown to be
associated with
accretion onto an
IMBH
What to Expect in the Future ?
Systematic modeling of galaxy samples:
dependence on SFR, galaxy mass,
age, metallicity
spirals and mixed populations, bulges and disks
Bigger source samples: probing the rare brightest sources,
questions of BH formation, ULXs
Long-term time monitoring:
identification of X-ray transients
and clues to ULX nature