Black Holes: ObservationsLecture 2: BHs in close binaries

Plan of the lecture
Close binaries. Evolution.
BH candidates
Mass determination
Systems BH+PSR – the astrophysical Holy Grail
Spectra and states
Variability. QPO.
ULX – ultraluminous X-ray sources

Reviews
astro-ph/0606352 X-ray Properties of Black-Hole Binaries
astro-ph/0306213 Black Hole Binaries
astro-ph/0308402 Intermediate-Mass Black Holes
astro-ph/0410536 Accreting Neutron Stars and Black Holes:
A Decade of Discoveries
astro-ph/0410381 What can we learn about black-hole formation
from black-hole X-ray binaries?
gr-qc/0506078 Black Holes in Astrophysics
astro-ph/0504185 Black Hole States: Accretion and Jet Ejection
astro-ph/0501298 Class Transitions in Black Holes
astro-ph/0410556 Inclination Effects and Beaming in Black Hole X-ray Binaries
astro-ph/0312033 Evidence for Black Hole Spin in GX 339-4: XMM-Newton EPIC-pn and RXTE Spectroscopy of the Very High State
arxiv:0706.2389 Models for microquasars
arxiv:0706.2562 X-ray observations of ultraluminous X-ray sources

X-ray observations: Cyg X-1
“In the case of Cyg X-1
black hole – is the most
conservative hypothesis”
Edwin Salpeter
The history of exploration
of binary systems with BHs
started about 35 years ago...

X-ray novae
Low-mass binaries
with BHs
One of the best candidates
In the minimum it is
possible to see the
secondary companion,
and so to get a good mass
estimated for a BH.

X-ray nova light curve
(Psaltis astro-ph/0410536)
A NS system
A BH system

BH candidates
Among 20 good candidates
17 are X-ray novae.
3 belong to HMXBs
(Cyg X-1, LMC X-3, GRS 1915+105).
(J. Orosz, from astro-ph/0606352)

Candidates properties
(astro-ph/0606352)
Also there are about 20 “canditates to candidates”.

Mass determination
here mx, mv - masses of a compact object and of a normal
(in solar units), Kv – observed semi-amplitude of the line of sight velocity of
the normal star (in km/s), P – orbital period (in days),
e – orbital eccentricity, i – orbital inclination (the angle between the line of sight
and the normal to the orbital plane).
As one can see, the mass function of the normal star is the absolute lower limit
for the mass of the compact object.
The mass of the compact object can be calculated as:
So, to derive the mass of the compact object in addition to the line of sight velocity
it is necessary to know independently two more parameters:
the mass ratio q=mx/mv, and the orbital inclination i.

Black hole masses
(Orosz 2002, see also
Psaltis astro-ph/0410536)
The horizontal line corresponds to
the mass equal to 3.2 solar.

Systems BH + radio pulsar: a Holy Grail
The discovery of a BH in pair with a radio pulsar can provide
the most direct proof of the very existence of BHs.
Especially, it would be great to find a system with a millisecond pulsar
observed close to the orbital plane.
Computer models provide different estimates of the abundance of such systems.
Lipunov et al (1994) give an estimate about
one system (with a PSR of any type)
per 1000 isolated PSRs.
Pfahl et al. (astro-ph/0502122) give much
lower estimate for systems BH+mPSR:
about 0.1-1% of the number of binary NSs.
This is understandable, as a BH should be
born by the secondary (i.e. initially less
massive) component of a binary system.

Parameters of systems BH+PSR
(Lipunov et al. 1994)

Spectra of BH candidates
(Psaltis astro-ph/0410536)
XTE 1118+480

The spectrum of Cyg X-1
(Miller et al. 2002, see Psaltis astro-ph/0410536)
Absorption features are formed in the wind of the companion.

Jet from GRS 1915+105
(Mirabel, Rodrigez 1994, see Psaltis astro-ph/0410536)
VLA data. Wavelength 3.5 cm.

States (luminosity+spectrum+jet)
astro-ph/0306213 McClintock, Remillard
Black holes on binary systems
Now there are several classifications
of states of BH binaries.
The understading that BH binaries
can pass through different “states”
(characterized by luminosity, spectrum,
and other features, like radio emission)
appeared in 1972 when Cyg X-1
suddenly showed a drop in soft X-ray flux,
rise in hard X-ray flux,
and the radio source was turned on.

Three-state classification
(Remillard, McClintock astro-ph/0606352)
In this classification the luminosity is
not used as one of parameters.

Discs and jets
(Fender et al. 2004,
Remillard, McClintock astro-ph/0606352)
The model for systems with radio jets
LS – low/hard state
HS – high/soft state
VHS/IS –very high and
intermediate states
The shown data are
for the source GX 339-4.

GRO J1655-40 during a burst
(Remillard, McClintock astro-ph/0606352)
Red crosses – thermal state,
Green triangles – steep power-law (SPL),
Blue squares – hard state.

4U 1543-47 and H1743-322
(Remillard, McClintock astro-ph/0606352)

XTE J1550-564 and XTE J1859-226

QPO
BH candidates demonstrate two main types of QPOs:
Low-frequency (0.1-30 Hz) and high-frequency (40-450 Hz).
Low-frequency QPOs are found in 14 out of 18 objects.
They are observed during different states of sources.
Probably, in different states different mechanisms of QPO are working.
High-frequency QPOs are known in a smaller number of sources (7).
It is supposed that frequencies of these QPOs correspond to the ISCO.

QPO and flux from a disc
(Remillard, McClintock astro-ph/0606352)
SPL – green triangles
Hard – blue squares
Intermediate states – black circles
Probably, QPO mechanisms in the hard state
and in the SPL state are different.
Low-frequency QPOs
(their frequency and amplitude)
correlate with spectral parameters.

QPO at high (for BHs) frequency
(Remillard, McClintock astro-ph/0606352)
All QPO at >100 Hz
are observed only
in the SPL state.
Blue curves: for
the range 13-30 keV.
Red curves: for a
wider range (towards
lower energies).

QPOs and BH masses
(Remillard, McClintock astro-ph/0606352)
XTE J1550-564,
GRO J1655-40,
GRS 1915+105
Dashed line is plotted for the relation
ν0 = 931 Hz (M/MO)-1

Quescent luminosity vs. Orbital period
(Garcia et al. 2001,
see Psaltis astro-ph/0410536)
Open symbols – neutron stars
black symbols – black holes.

GS 2000+25 and Nova Oph 1997
(Psaltis astro-ph/0410536)
On the left – Hα spectrum,
On the right – the Dopler image
See a review in Harlaftis 2001
(astro-ph/0012513)
GS 2000+25
Nova Oph 1997
There are eclipse mapping, dopller tomography (shown in the figure),
and echo tomography (see 0709.3500).

IR observ. of sources in quescent state
arXiv:0707.0028 E. Gallo et al.
“The spectral energy distribution of quiescent black hole X-ray binaries:
new constraints from Spitzer”
Excess at 8-24 microns.
Possible explanation: jet synchrotron emission.

Ultraluminous X-ray sources
ULXs are sources with fluxes which
correspond to an isotropic luminosity
larger than the Eddington limit
for a 10 solar mass object.
Now many sources of this type are
known. Their nature is unclear.
Probably, the population contains both:
stellar mass BHs with anisotropic
emission and intermediate mass BHs.

ULXs in NGC 4490 and 4485
Six marked sources are ULXs

Spectrum of the ULX in NGC 1313
NGC 1313 X-1
Green line –
the IMBH model.
Red – thermal component.
Blue – power-law.
(arXiv 0726.2562)

Spectra of ULXs
(arXiv 0706.2562)

ULX in galaxies of different types
In the following two slides there are images of
several galaxies from the SDSS in which positions of ULXs are marked.
Crosses (x) mark sources with luminosities >1039 erg/s.
Pluses (+) mark sources with luminosities >5 1038 erg/s.
The size of one square element of the grid is 1.2 arcminute
(except IZW 18, in which case the size is 0.24 arcminute in right ascension
and 0.18 in declination).
Galaxies NGC 4636, NGC 1132, NGC 4697, NGC 1399 are ellipticals,
IZW 18 – irregular, the rest are spiral galaxies.
Ellipses mark the 25-th magnitude isophotes
(this a typical way to mark the size of a galaxy).

ULX in galaxies of different types
NGC 1132
IZW 18
NGC 253
NGC 1291
IC 2574
NGC 1399

ULX in galaxies of different types
NGC 2681
NGC 4697
NGC 4631
NGC 3184
NGC 4636

The source X-1 in М82
The source M82 X-1 is one of the most
luminous, and so it is the best candidate
to be an intermediate mass BH.
QPOs are observed in this source.
Their properties support the hypothesis
of an intermediate mass BH.
(http://www.pd.astro.it/oapd/2/2_1/2_1_5/2_1_5_1.html)

М82, stellar clusters and ULXs
Intermediate mass BHs can be
formed in dense stellar clusters.
See, however, 0710.1181 where
the authors show that for
solar metallicity even
very massive stars most
probably cannot produce BHs
massive enough.
McCrady et al (2003)