OBSERVATIONAL EVIDENCE FOR STELLARMASS BLACK HOLES Jorge Casares IAC

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• OBSERVATIONAL EVIDENCE FOR STELLAR-MASS BLACK
  HOLES Jorge Casares (IAC)

P. Charles (SAAO) T. Shahbaz (IAC) C. Zurita
(Obs. San Pedro Martir) R. Hynes (Lousiana State
Univ.) D. Steeghs (Harvard-Smithsonian Center for
Astroph.)
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Impact in Astrophysics
1st observational evidence of BHs not until
last 3 decades Fundamental objects throughout
astrophysics (XRB, AGN) Stellar-mass BH best
opportunity for detailed studies

• Test SNe models and evolution of massive stars
  
• e.g. V404 Cyg, GRS 1915105

• Chemical enrichment of the Galaxy
• e.g. GRO J1655-40, A0620-00, V4641 Sgr, XTE
  J1118480

• Accretion physics, outflows and production of
  VHE radiation
• e.g. microquasars GRS 1915105, GRO
  J1655-40, LS 5039 ()

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Outline

• 1.- Introduction dynamical evidence
• 1st BH candidates in X-ray Binaries
• From candidates to confirmed black holes
• 2.- Demography
• Population number
• Masses, distribution and implications
• 3.- Conclusions

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Early History
1.- Introduction

• 60s X-ray astronomy (UHURU, Ariel)
• Population of 102 X-ray sources in the Galaxy
  with LX 1038 erg/s and
  variability down to millisec
• Compact object accreting 10-9 M?/yr from a
  close companion star

(Shklovskii 1967)
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Two types of X-ray binaries

• 1) High Mass (HMXBs)
• O-B I
• Lopt/LX ? 10
• 2) Low Mass (LMXBs)
• K-M V
• Lopt/LX ? 10-2

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Cyg X-1 ( HDE 226868)

• O9.7 Iab
• Velocity K 64 km/s (latter refined to 75 km/s)
  and Porb 5.6 d.

Webster Murdin 1972 Nature 235 37 Bolton 1972
Nature 240 124
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The mass function
f (M) lt MX
Typically O9.7 Iab has 33 M? (and then MX 7
M?, i90º)
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EoS of Neutron Stars

• Oppenheimer Volkoff (1939) maximum mass for NS
  stable against gravitional collapse

• Rhoades Ruffini (1974) upper limit 3.2 M?
  assuming causality holds beyond ?nm 3x1014
  g/cm3.
• Kalogera Baym (1996) 2.9 M? with EoS
  accurate 2?nm

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A 0620-00 ( N. Mon 75)
X-ray Nova discovered by Ariel in 1975 with Fx
50 Crabs
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A 0620-00 ( N. Mon 75)
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Black Hole Candidates

• Historic debate about existence of BHs (80s)
• 3 candidates
• Cyg X-1 f (M)0.25 0.01 M?
• LMC X-3 f (M)2.3 0.3 M?
• A0620-00 f (M)3.2 0.2 M?
• Alternative models
• Multiple stars (Fabian, Pringle, Whelan 1974)
• Q stars (Bahcall et al. 90)

Holy Grail would be f(M) gt 5 M? (McClintock 86)
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V404 Cygni (GS 2023338)

• XRT discovered in 1989 by Ginga with Lx ? 1039
  erg/s

Casares, Charles Naylor 1992 Nature 355 614

• K0IV donor
• P 6.5 d.
• K 211 km/s

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GX 339-4 a novel technique

• Classic Black Hole candidate based on X-ray
  properties
• Quiescence in 2000-01 but companion undetected
• New outburst in 2002 NIII/CIII emission lines
  at ??4630-40

Donor not detected but use irradiated lines to
trace its orbit
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GX 339-4
Multigausian fit to NIII lines
Porb1.76 d from HeII velocities
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Confirmed Black Holes with dynamical evidence

• System Porb f(M)
  Spect. Type Classification
• GRS 1915105 33.5 d 9.5 3.0
  M? K/MIII
  Transient
• V404 Cyg 6.470 d 6.08
  0.06 M? K0IV
  ,,
• Cyg X-1 5.600 d 0.244
  0.005 M? 09.7Iab
  Persistent
• LMC X-1 4.229 d 0.14
  0.05 M? 07III
  ,,
• XTE J1819-254 2.817 d 2.74 0.04
  M? B9III
  Transient
• GRO J1655-40 2.620 d 2.73 0.09
  M? F3/5IV ,,
• BW Cir 2.545d 5.75
  0.30 M? G5IV
  ,,
• GX 339-4 1.754 d 5.8
  0.5 M? --
  ,,
• LMC X-3 1.704 d 2.3
  0.3 M? B3 V
  Persistent
• XTE J1550-564 1.542 d 6.86 0.71
  M? G8/K8IV Transient
• 4U 1543-475 1.125 d 0.25
  0.01 M? A2V
  ,,
• H1705-250 0.520 d 4.65
  0.21 M? K3/7V
  ,,
• GS 1124-684 0.433 d 3.01
  0.15 M? K3/5V
  ,,
• XTE J1859226 0.382 d 7.4 1.1 M?
  --
  ,,
• GS2000250 0.345 d 5.01
  0.12 M? K3/7V
  ,,
• A0620-003 0.325 d 2.72
  0.06 M? K4V
  ,,
• XTE J1650-500 0.3205 d 2.73 0.56
  M? K4V ,,

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Further support absence of a hard surface

• Lack of pulses/X-ray bursts (Remillard et al.
  2006)

• Differences in X ray colour-colour diagram (Done
  Gierlinski 2003) and Temperatures of the
  ultrasoft component at high accretion
  luminosities (e.g. Remillard et al. 2006).

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2.- Demography number, masses
How many are there and what is the mass-spectrum
?
BH XRTs are the tip of iceberg of Galactic
population
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Weighing BHs
1)

• 2) Measure Vrot sini

3) Fit ellipsoidal modulation
Amplitude is strong function of inclination
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Mass spectrum of BHs
15 reliable masses of BHs 4-14 M?
Typical errors 30

• Goals
• improve statistics
• reduce errors to 10

• Do BH masses cluster at a particular value?
• What are the edges of the BH distribution?
• Is there a continuum distribution between NS
  BHs?

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Comparison with SNIb Models
Fryer Kalogera (1999)

• V404 Cyg/GRS1915105 BH masses 122 M? 144
  M? just above mass cut mass-loss during WR phase
  overestimated?

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Conclusions

• Best observational evidence for stellar-mass BHs
  based on dynamical studies of X-ray binaries.
• First BH candidates Cyg X-1 (1972) A0620-00
  (1986).
• BH candidates confirmed with discovery of f(M)6
  M? V404 Cyg (1992)
• X-ray properties (lack pulsations/bursts, weak
  quiescent Lx) supports presence of event
  horizon.
• XRTs are best hunting ground for new BHs with 17
  cases. Masses range between 414 M? .
• Tip of iceberg of hidden population of 103 BH
  binaries and 108 stellar-mass BHs in the Galaxy.
• Better statistics needed to derive constraints to
  close binary evolution and SNe models.

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Further support absence of a hard surface
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Israelian et al. 1999 Nature 401 142
Parecen estrellas normales pero deberían
mostrar indicios de un pasado violento (explosión
de SN, erupciones de rayos X...)
XTE J1655-40

• enriquecimiento un factor 6-10 de elementos ? en
  la compañera F6III (MC2.3 M? )

• Sólo se sintetizan en el interior de estrellas gt
  10 M?
• La compañera fue enriquecida por la
  explosión de la SN
• que formó el AN en este sistema.

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X0921-63 ADC with K0III donor in P9.0 d

• Shahbaz et al. 2004 ApJ 493 L39
  Jonker et al. 2004 MNRAS 356 621

• Firts radial velocity curve (some evidence for
  irradiation?)
• MX sin3 i gt 1.9 0.25 M? i70-90
  (eclipses)

Massive NS or low-mass BH??
Mx2.0-4.3 M? (no irradiation)
Mx1.9-2.9 M? (irradiation model)
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New Technique for dynamical studies

• Steeghs Casares 2002 ApJ 568 273
• Sharp NIII CIII Bowen lines in Sco X-1
• Doppler shift traces orbit of donor star

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X1822-371

• Doppler Tomography Kem 300
  8 km/s ? K

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Proving the BH in BW Cir

• Faint X-ray Binary in quiescence at R21
• VLT FORS2 at R 4300

Porb2.55 days K279 5 km/s
Vrot sin i71 km/s Mc/MX 0.13
f(M)5.8 0.3M?
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The latest BH BW Cir (GS 1354-64)

• Vrot sin i71 km/s q
  0.13
• i lt 70o (no eclipses)

MX gt7.8 M?
65 veiling
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The latest BH BW Cir (GS 1354-64)

• Companion is G0-8 Teff5100-5700 K and veiled
  by 65
• R ? 3.6R? set by size of Roche lobe

L ? 10 L?
Radial velocity of Galactic rotation curve 104
km/s, consistent with measured ?-velocity
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OSIRIS BH Target XTE J1859226
Zurita et al. 2002 MNRAS 334 999
Ellipsoidal modulation at P7.7 or 9.2 hr
R22.48 0.07

• Filipenko Chornock (IAUC 7644) announced
  f(M)7.4 1.1 M?
• Requires
  confirmation!!
• OSIRIS IN SPECTROSCOPIC MODE AT R2000- 5000

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X0921-63 ADC with K0III donor in P9.0 d

• Shahbaz et al. 2004 ApJ 493 L39
  Jonker et al. 2004 MNRAS 356 621

• Firts radial velocity curve (some evidence for
  irradiation?)
• MX sin3 i gt 1.9 0.25 M? i70-90
  (eclipses)

Massive NS or low-mass BH??
Mx2.0-4.3 M? (no irradiation)
Mx1.9-2.9 M? (irradiation model)
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To learn more about the early epoch see Bradt et
al. (1992). The complete story at http//heasarc.
gsfc.nasa.gov/docs/heasarc/headates/heahistory.htm
l
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Gallo et al. (2003) found a correlation between
radio and X-ray flux for Black Holes in the
low/hard state. If the X-rays not beamed, then
the Lorentz factors of the compact radio jets
should be smaller than 2 to account for the small
scattering of the correlation.
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Why should we expect microquasars to be ?-ray
emitters?

• Their extragalactic analogous, the quasars, are
  ?-ray emitters
• (analogy quasar-microquasar Mirabel
  Rodríguez, Nature 1992,1994)
• Theoretical models predict ?-rays from
  microquasars, i.e.
• Leptonic models SSC Atoyan
  Aharonian 1999, MNRAS 302, 253
• 
  Latham et al. 2005, AIP CP745, 323
• 
  EC Kaufman Bernadó et al. 2002, AA 385, L10
• 
  
  Georganopoulos et al. 2002, AA 388, L25
• SSCEC
  Bosch-Ramon et al. 2004 AA 417, 1075
• Synchrotron jet emission Markoff
  et al. 2003, AA 397, 645
• Hadronic models Pion decay Romero et
  al. 2003, AA 410, L1
• 
  
  Bosch-Ramon et al. 2005, AA 432, 609

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We have obtained a radial velocity curve of LS
5039 with the INT (IDS) during 2 campaigns on
2002 and 2003 (Casares et al. 2005). The orbital
period is found to be 3.906 d and the orbital
parameters depend on the spectral lines used in
the analysis. All Balmer and He lines
included
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The results suggest that LS 5039 might be a black
hole with 3-5 solar masses (Casares et al. 2005)
(but optically thin radio spectrum). The orbit is
eccentric.
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Reminder of different error box sizes. Importance
of position accuracy from TeV observations.
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• With the new orbital ephemerides (Casares et al.
  2005), we have been able to see correlated TeV
  and X-ray orbital variability
• Accretion changes in an eccentric orbit.
• VHE gamma-ray absorption by pair creation with
  photons of the companion.
• HESS
• RXTE

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We have enough information to build up a Spectral
Energy Distribution
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Radio, L0.1-100 GHz 1?1031 erg/s
Synchrotron Radiation
e-
e-
e-
g-ray, E gt 100 MeV, Lg 4?1035 erg/s
Inverse Compton Scattering
UV, E 10 eV
Lopt 1?1039 erg/s
e-

ge 103
X-ray L3-30 keV 5?1034 erg/s
O6.5V((f))
e-
vjet ? 0.15c
e-
Proposed scenario
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We have enough information to build up a Spectral
Energy Distribution to extract physical
information. A leptonic model with external
comptonization can explain the observations
(Paredes et al. 2006).
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Current status on LS 5039 VLA observations
covering several orbital cycles reveal no
periodic variability, and a progressive cut-off
towards high radio frequencies. The source is one
order of magnitude brighter than the correlation
for BH in the low/hard state. New detailed
observations have been conducted with HESS.
Results challenging models will be published
soon. We are analyzing further VLBI observations
to better trace the inner jet structure and
eventually measure the jet speed. New models
including all angle dependencies (for IC
scattering, gamma-ray absorption by photon-photon
pair creation, cascading) are being produced, and
will hopefully be tested soon against new data
(see Dubus 2005, Paredes et al. 2006, Bednarek
2006). Alternative models based on the
interaction between the relativistic wind of a
non-accreting millisecond pulsar and the UV
photons of the massive companion have also been
proposed (Dubus 2006).