Download Multiwavelength observations of XTE J1118+480`s outburst

The most obscured
high energy
sources
Or how infrared observations allow
to reveal mysteries of the most
obscured X-ray sources of our
Galaxy…
Sylvain CHATY
(Université Paris 7 / Service d’Astrophysique, France)
ESO - 28 novembre 2006
Plan




The INTEGRAL observatory
Discovery of new sources in our Galaxy
How to understand their nature?
Multi-wavelength optical/NIR/MIR observations:




Obscured X-ray sources: the archetype IGR J16318-4848
Supergiant Fast X-ray Transients: the archetype IGR J17544-2619
Results and discussion on new INTEGRAL sources
Conclusions and perspectives
S. Chaty - ESO - 28/11/2006
Plan




The INTEGRAL observatory
Discovery of new sources in our Galaxy
How to understand their nature?
Multi-wavelength optical/NIR/MIR observations:




Obscured X-ray sources: the archetype IGR J16318-4848
Supergiant Fast X-ray Transients: the archetype IGR J17544-2619
Results and discussion on new INTEGRAL sources
Conclusions and perspectives
S. Chaty - ESO - 28/11/2006
The INTEGRAL observatory
INTEGRAL satellite: 2 keV – few MeV
Launched on 17 October 2002 by PROTON rocket on excentric orbit
S. Chaty - ESO - 28/11/2006
INTEGRAL observatory


4 instruments
2 coded mask
telescopes: imager IBIS
and spectro-imager SPI:
10keV-4MeV



Resolution 12’, fov 19°
1 coded mask X telescope
JEM-X: 2-100keV
1 optical telescope: OMC
S. Chaty - ESO - 28/11/2006
Multi-wavelength observations


Ground and space…
Multi-wavelength
observations (radio, infrared
and X/ rays
S. Chaty - ESO - 28/11/2006
Plan




The INTEGRAL observatory
Discovery of new sources in our Galaxy
How to understand their nature?
Multi-wavelength optical/NIR/MIR observations:




Obscured X-ray sources: the archetype IGR J16318-4848
Supergiant Fast X-ray Transients: the archetype IGR J17544-2619
Results and discussion on new INTEGRAL sources
Conclusions and perspectives
S. Chaty - ESO - 28/11/2006
The Milky Way, our Galaxy
(seen from inside)
S. Chaty - ESO - 28/11/2006
The Milky Way, our Galaxy
(seen from outside)
Side view
S. Chaty - ESO - 28/11/2006
Face-on
The Milky Way, our Galaxy
S. Chaty - ESO - 28/11/2006
Discovery of a new type of sources in the sky

Mystery of the X-ray background
Observations of the Milky Way:

IBIS resolved it in many point sources

New sources towards the
Norma arm of the Galaxy,
previously unknown…

(>200: Bird et al. 2006)
Still present at higher energies
Zoom on the center
And this Norma arm is full of
star formation regions!
G-rays
(INTEGRAL/ISGRI)
IR (COBE)
S. Chaty - ESO - 28/11/2006Lebrun et al. 2004
Tomsick et al. 2004
Plan




The INTEGRAL observatory
Discovery of new sources in our Galaxy
How to understand their nature?
Multi-wavelength optical/NIR/MIR observations:




Obscured X-ray sources: the archetype IGR J16318-4848
Supergiant Fast X-ray Transients: the archetype IGR J17544-2619
Results and discussion on new INTEGRAL sources
Conclusions and perspectives
S. Chaty - ESO - 28/11/2006
Unidentified INTEGRAL sources

Among IGR sources:




~1/10: already known faint ASCA sources (Sugizaki)
A few already known RXTE sources
~1/10: certainly AGNs (Bassani et al.)
25% of INTEGRAL sources have a likely ROSAT
counterpart

50% of the sources detected by par INTEGRAL! (Stephen et al)
S. Chaty - ESO - 28/11/2006
X-RAY BINARIES
X-ray binary: binary system containing a compact object (neutron star or
stellar-mass black hole) accreting matter from the companion star. Accreted
matter carries angular momentum and on its way to the compact object usually
forms an accretion disk, responsible for the X-ray emission.
280 X-ray binaries are known (Liu et al. 2000, 2001).
High Mass and Low Mass X-Ray Binary Systems
 HMXB : companion mass M2 > M
 Luminous, young, early type (O, B)
 Stellar Wind fed systems
 LMXB : companion mass M2  M
 Faint, old, late spectral type (K, M)
 Roche-Lobe / Disk fed systems
High Mass X-ray Binaries (HMXBs). Optical companion with spectral type O
DYNAMICAL
ESTIMATE
or B. Mass transfer
viaMASS
decretion
disk (Be stars) or via strong wind or Rochelobe overflow (OB
SG).
131
 Orbital
parameter
fromknown
measures ofHMXBs.
GRS 1915+105
Doppler shifts of Optical or IR lines/bands
 Derived Mass Function
f (M) = 9.5 M
f (M) = (M1cos i)3 / (M1 + M2)2  M1
can
provide estimate of Compact Object Mass
Low Mass X-ray Binaries (LMXBs). Optical companion with spectral type
later than B. Mass
transfer
overflow.
Masses
larger thanvia
3 M Roche-lobe
must imply BH
149 known LMXBs.
(Greiner et al 01)

S. Chaty - ESO - 28/11/2006
Galactic distribution


A fair fraction of new INTEGRAL
sources should be High Mass X-ray
Binaries (HMXBs)
Over-density of INTEGRAL sources in
the region tangent to the Norma arm
(5–8kpc)
131
149
New : -0.9
HMXB : -0.6
HMXB+new: -0.6
HMXB (XTE): -0.6±0.1
Walter et al. 2006
S. Chaty - ESO - 28/11/2006
Discovery of a new type of sources

How to identify all these new INTEGRAL sources?

To observe in X/ rays is not enough:


ISGRI localisation not enough to identify the counterpart
To observe in optical is difficult:

Sources mainly in the plane (centre) of the Galaxy: too much absorption
(interstellar dust and gas)
S. Chaty - ESO - 28/11/2006

Programme of study of new high energy binary sources


Identification of counterparts, nature of system, compact object, companion
star, distance, accretion type…
characterize presence, temperature, composition of dust

Photometry/Spectroscopy on 15 INTEGRAL sources

3 domains:




Optical EMMI (400-800 nm): La Silla (3.5m-NTT)
Near-infrared SOFI (1-2.5 mm): La Silla (3.5m-NTT)
Mid-Infrared VISIR (5-20mm): Paranal (8m-VLT/UT3)
2 modes of observations (European Southern Observatory):


« Target of Opportunity mode»: ~16h/semester to observe new binary systems
« Visitor mode »: 3 nights 07/2004, 1 night 06/2005, 2 nights 06/2006
S. Chaty - ESO - 28/11/2006
Plan




The INTEGRAL observatory
Discovery of new sources in our Galaxy
How to understand their nature?
Multi-wavelength optical/NIR/MIR observations:




Obscured X-ray sources: the archetype IGR J16318-4848
Supergiant Fast X-ray Transients: the archetype IGR J17544-2619
Results and discussion on new INTEGRAL sources
Conclusions and perspectives
S. Chaty - ESO - 28/11/2006
Plan




The INTEGRAL observatory
Discovery of new sources in our Galaxy
How to understand their nature?
Multi-wavelength optical/NIR/MIR observations:




Obscured X-ray sources: the archetype IGR J16318-4848
Supergiant Fast X-ray Transients: the archetype IGR J17544-2619
Results and discussion on new INTEGRAL sources
Conclusions and perspectives
S. Chaty - ESO - 28/11/2006
The Obscured INTEGRAL source IGR J16318-4848:

From INTEGRAL high energy …
…to Optical/MIR observations.


(Chaty & Rahoui, 2006; Chaty & Filliatre, Ap&SS, 2005; Filliatre & Chaty, ApJ, 2004)
S. Chaty - ESO - 28/11/2006
Discovery of IGR J16318-4848 by INTEGRAL


1st source discovered by
INTEGRAL (IBIS/ISGRI) on 29
January 2003
Position:




(l,b)~(336°, 0.5°)
RA=16h31.8m, DEC=-48°48’
Localisation accuracy: 2’ with
INTEGRAL (Moon: 30’!)
Non-absorbed Flux:

15-40 keV Flux: 50-100 mCrab
(Courvoisier et al. 2003)

L5kpc = 1-20
S. Chaty - ESO - 28/11/2006
1036 erg/s
INTEGRAL/ISGRI (15-40 keV)
Norma arm region image (Walter
et al. 2003)
ToO observations with XMM-Newton

XMM observations (28ks ToO on
10/02/2003): 4” localisation

Comptonised spectrum:




Strong photoelectric absorption:



Fe absorption edge at 7.1keV
Fe K, K, Ni K Fluorescence lines
Variability:







Nh=1.84+/-0.06x1024 cm-2
kT = 9±0.5 keV
Photon index ~ 2
RXTE: no oscillation detected
variable flux (factor 20)
10 hours between each flare
Sometimes 2-3 days of inactivity
Nh-flux correlation?
Variations of lines and continuum on
temporal scale of 1000s: size of emitting
region < 3 x 1013 cm (Walter et al. 2003)
X-ray properties ~ CI Cam, Vela X1, GX
301-2
S. Chaty - ESO - 28/11/2006
EPIC PN, EPIC MOS2 and ISGRI spectra
(Matt & Guainazzi 2003; Walter et al. 2003)
Discovery of the optical/NIR counterpart
B>25.4+/-1; V>21.1+/-0.1
R=17.72+/-0.12; I=16.05+/-0.54
J=10.33+/-0.14; H=8.33+/-0.10
Ks=7.20+/-0.05
IGR J16318-4848


photometric observations on 23-25/02/2003
Discovery of the R, I, Z counterpart


Comparison with USNO B1.0 plate R band: only one of the two sources
varied in the XMM EPIC 4” uncertainty circle.
Confirmation of NIR counterpart proposed by Walter et al. 2003
by an improved astrometry
S. Chaty - ESO - 28/11/2006
Absorption in
optical/NIR

B, V, R, I, J, H, K
magnitudes of
candidate and 4
neighbours
IGR source exhibits unusual 17.4mag
absorption
•stronger than absorption along line
of sight objects (11.4mag),
•but 100 x lower than X-rays!!!
Material absorbing in X-rays must be
concentrated near the compact object
S. Chaty - ESO - 28/11/2006
NIR spectroscopy: 0.95-2.5 mm
Unusual spectrum very rich in many strong emission lines

•
•
•
•
•
•
Strong H (Br, Pa, Pf) and HeI (P-Cyg): emanate from dense, ionised wind
He II: highly excited region in vicinity of compact object
[FeII]: indication of shock heated material
FeII => densities > 105-106 cm-3
NaI: cool/dense regions shielded from stellar and compact object radiation
Lines originate from different media (various densities, temperature)
Highly complex, stratified circumstellar environment + enveloppe, wind…
• => luminous post main sequence star: most likely an uncl/sgB[e] star:
High-mass X-ray binary system, similar to CI Cam
S. Chaty - ESO - 28/11/2006
Spectral Energy Distribution
Fit parameters:
L ~ 106 d26kpcLSun
T = 20 250 K
M = 30 MSun
High L, T and M:
Supergiant star
Distance = 6kpc




Av = 17.5 mag
r/D=5x10-10
• Unusual absorption:
cocon of dust?
Hertzprung-Russel Diagram
S. Chaty - ESO - 28/11/2006
Color-magnitude diagramme
Position computed for 2
different absorptions (11.8
and 17.4 mag) and for
distances between 1 and 8
kpc
Parameter space indicate a
hot supergiant between 1
and 6 kpc
Absorption <17.4mag
Compatible with OB type
supergiants
S. Chaty - ESO - 28/11/2006
IGR J16318-4848 Optical -> mid-infrared SED
Spitzer
•Unusual absorption:
cocoon of dust?
ESO/NTT
VLT/VISIR

Model:





Companion star: sgB[e], T=23500 K, R=20.4 Rsun = 15 106 km
Dust component: T=900K, R=12 R* = 1ua
Av=17.6, D=1.2 kpc
Result: Fit 2/dof=89.4/99
Need for extra (e.g. dust) component. Extension of this dust component
seems to suggest that it is enshrouding the whole binary system.
S. Chaty - ESO - 28/11/2006
Nature of the compact object
Correlation in LHS black
hole systems between Xray/radio flux densities:
50-100 mCrab X-ray flux
=> 10 mJy radio flux
Radio ATCA observation on
2003 Feb 9: no detection
up to 0.1 mJy associated
with low/hard X-ray
emission => compact
object is a neutron star
But correlation not always verified…
S. Chaty - ESO - 28/11/2006
Gallo et al. 2004
Nature of IGR J16318-4848

High Mass X-ray Binary system:

neutron star + early-type supergiant B[e] star



Absorption:




the 2nd HMXB with sgB[e] after CI Cam
Distance 1 to 6 kpc
in X-rays 2 orders of magnitude > IR
in opt/IR 2 orders of magnitude > line of sight
System surrounded by dense and absorbing dusty
circumstellar material/enveloppe, + cold and hot stellar
wind components
Because they are obscured, the « Norma arm » sources can only be
studied in high-energy and infrared domains.
S. Chaty - ESO - 28/11/2006
Plan




The INTEGRAL observatory
Discovery of new sources in our Galaxy
How to understand their nature?
Multi-wavelength optical/NIR/MIR observations:




Obscured X-ray sources: the archetype IGR J16318-4848
Supergiant Fast X-ray Transients: the archetype IGR J17544-2619
Results and discussion on new INTEGRAL sources
Conclusions and perspectives
S. Chaty - ESO - 28/11/2006
The SFXT (Supergiant Fast X-ray Transient) source IGR J17544-2619…

From INTEGRAL high energy …
…to Optical/MIR observations.


(Chaty & Rahoui 2006, proc. INTEGRAL; Pellizza, Chaty, Negueruela, 2006, A&A)
S. Chaty - ESO - 28/11/2006
IGR J17544-2619
Recurrent transient X-ray source discovered by
INTEGRAL (09/2003) near the Galactic center
(Sunyaev et al. 2003, ATel 190)
Bursts last ~hours, long quiescence periods, no
radio emission reported
(Gonzalez-Riestra et al. 2004, A&A 420, 589)
Very hard X-ray spectrum, Nh~2 1022, another
highly absorbed galactic XB?
Negueruela, Smith, Reig, Chaty, Torrejon, 2005
(Gonzalez-Riestra et al. 2004, A&A 420, 589)
Similar to other IGR sources (J16318-4848, J16320-4851, J16358-4726)
(Chaty 2004, Gonzalez-Riestra et al. 2004, A&A 420, 589; Smith 2005, ATEL 338)
A new kind of XBs? Important to establish their nature
Optical/NIR Target of Opportunity observations 1 day after discovery!
S. Chaty - ESO - 28/11/2006
Image Ks
IGR J17544-2619 optical/NIR counterpart
2’
Ks-band image
XMM: 4” error radius
1RXS J175428: ROSAT source not
connected with IGR J17544
IGR J17544-2619
(Pellizza, Chaty, Negueruela, 2006, A&A)
S. Chaty - ESO - 28/11/2006
J-band image 5.5’x5.5’
INTEGRAL: 2’ error radius
ROSAT: 23” error radius
XMM: 4” error radius
Chandra: 0.4’’
IGR J17544-2619 optical/NIR counterpart
1 bright candidate (B) identified in USNO & 2MASS
3 very faint candidates (F1-3): foreground dwarf stars?
1 extended object (E) high-z galaxy?
S. Chaty - ESO - 28/11/2006
Candidate B spectrum
Blue supergiant O9 Ib (25-28 M, T~32000K)
High-mass X-ray binary
Existence of a stellar wind: 265 ± 20 km/s (unusually mild for O stars, cf. 400 km/s
in IGR J16318-4848: Filliatre & Chaty 2004, ApJ 616, 469)
S. Chaty - ESO - 28/11/2006
IGR J17544-2619 Optical -> mid-infrared SED
ESO/NTT
Presence of dust?
Spitzer
VLT/VISIR

Model:




Companion star: O9Ib, T=30500K, R=21.9 Rsun
Av=5.9, D=3.9kpc
Fit result: 2/dof=84/48
no need for extra (e.g. dust) component
S. Chaty - ESO - 28/11/2006
Nature of IGR
J17544-2619
•HMXB with companion of 25-28 M supergiant O9Ib
QuickTime™ et un
décompresseur TIFF (non compressé)
sont requis pour visionner cette image.
•Presence of mild stellar wind
•Compact object: likely Neutron Star (in’t zand 2005)
•Distance: 3-4 kpc
•Faint intrinsic absorption (1022cm-2), Long Poutburst=165d
•Detection of flux variations during quiescence
•Archetype of “SFXTs”: Supergiant Fast X-ray transients:
O/B
supergiant companions,
Compact object = BH or NS,
faint quiescent emission, outbursts lasting only hours.
S. Chaty - ESO - 28/11/2006
Plan




The INTEGRAL observatory
Discovery of new sources in our Galaxy
How to understand their nature?
Multi-wavelength optical/NIR/MIR observations:




Obscured X-ray sources: the archetype IGR J16318-4848
Supergiant Fast X-ray Transients: the archetype IGR J17544-2619
Results and discussion on new INTEGRAL sources
Conclusions and perspectives
S. Chaty - ESO - 28/11/2006
Results
•IGR J16318-4848 and IGR J17544-2619 exhibit common
characteristics:
•High Mass X-ray Binaries with O/B companion
•Compact object: neutron star or black hole
•X-ray transients
•No radio emission
•But they also exhibit differences:
•High intrinsic absorption around the compact object / the binary
system
•A new population of sources revealed by INTEGRAL.
Because some are obscured, these sources can only be studied at
high-energies and IR.
S. Chaty - ESO - 28/11/2006
Characteristics of the studied INTEGRAL sources
Source
Region
Pspin
Nh
Nhgal
NhEB-V
193
2.1
<4.2
Porb
Persistent sources
IGRJ16318-4848
Norma
IGRJ16320-4751
Norma
1250s
18
2.1
IGRJ16393-4641
Norma
912s
24
2.2
<2.7
IGRJ17252-3616
GC
413s
15
1.5
<5.3
IGRJ17597-2201
GC
5
1.2
<2.9
IGRJ18027-2016
GC
139s
9
1.1
<2.1
IGRJ16358-4726
Norma
5880s
39
2.2
<4.2
IGR J16418-4532
Norma
965s
10
2.0
<3.6
IGRJ16465-4507
Norma
228s
60
1.6
<1.0
IGR J16479-4514
Norma
8
2.1
<4.8
IGRJ17544-2619
GC
2
1.4
<2.5
9d
9.7d
4.6d
Transient sources
Zurita 2006 adapted
S. Chaty - ESO - 28/11/2006
NS
165d?
Results of 2004 NTT-SOFI/EMMI and 2005/2006 Paranal UT3-VISIR observations
Source
Type
Spectral
type
PAH1
(8.59 mm)
mJy
PAH2
(11.25 mm)
mJy
Q2
(18.72 mm)
mJy
Dust
Temp
(K)
Dust
Radius
(R*)
IGR J16195-4945
SFXT?/OBS
OB
<6
<8
<50
950
6.1
IGR J16318-4848
OBS
sgB[e]
409
322
172
900
11.9
IGR J16320-4751
OBS
OB
12
6
-
IGR J17391-3021
SFXT
O8Iab(f)
70
46
-
IGR J17544-2619
SFXT
O9Ib
36
20
-
B0
22 (extended)
9
<53
880
10.1
IGR J16207-5129
IGR J16358-4726
OBS
<7
-
-
IGR J16418-4532
SFXT
<6
-
-
IGR J16465-4507
SFXT/OBS?
B0.5I
9
5
-
IGR J16479-4514
SFXT
OB
12
7
-
IGR J17252-3616
OBS
OB
6
2
-
IGR J17597-2201
Late?
<6
-
-
IGR J18027-2016
sgOB
<6
-
-
IGR J19140+0951
OB?
35 (2 sources)
19 (2
sources)
-
S. Chaty - ESO - 28/11/2006
9 sources detected in MIR out of 14 = 2/3:
MIR (stellar) emission seems usual around these sources,
but the case of IGR J16318-4848 remains exceptional!
The systems









30% of sources detected by INTEGRAL/IBIS were not known.
80% of Norma sources are X-ray pulsars, high spin periods
Spectra typical of neutron stars
No radio emission
85% of sources are highly absorbed (X-ray observations): column density NH>1023 cm-2
X-ray absorption >> IR => absorbing matter local to neutron star
NH variation on short periods? => link with accretion column/geometry?
A big fraction of these sources are close to the galactic plane |b|< 1°
They are HMXBs, some identified with OB types (Opt/NIR observations)
S. Chaty - ESO - 28/11/2006
Nature of systems:
Corbet Diagramme



Underfilled Roche lobe Supergiants
80% of Norma sources are X-ray pulsars
High spin periods
Star Porb=10d, M=20Msol, a=50Rsol < Rdust
(Rdust=240RSunfor IGR J16318)
•HMXBs Pspin vs Porb:
•Be Binaries
•supergiant Roche lobe overflow
systems
•super-giant wind accretors
S. Chaty - ESO - 28/11/2006
So, what are these sources?
Different geometries, different possible scenarii

A new population of sources of our Galaxy revealed by INTEGRAL


~15 sources with same characteristics: not by chance!
80% are neutron stars orbiting around super-giant stars (hot, massive, luminous):

Presence of a cocoon of dense and absorbing dust concentrated:

1) Either around the compact object: SFXTs (~IGR J17544):


Wide orbit, neutron star penetrates inside the atmosphere/envelope of companion star, causing outbursts?
2) Or enshrouding the whole system: obscured sources (~IGR J16318) :




neutron star orbits within a dense equatorial wind
density 1011–12 cm–3
Disc thickness 1012–13 cm (10-100 RSun)
Disc radius 1013–14 cm (1-10 a.u.)

The answer will be given by orbital periods of these sources…

High and persistent column density => special wind configuration
Many such sources => geometry favours accretion

S. Chaty - ESO - 28/11/2006
Plan




The INTEGRAL observatory
Discovery of new sources in our Galaxy
How to understand their nature?
Multi-wavelength optical/NIR/MIR observations:




Obscured X-ray sources: the archetype IGR J16318-4848
Supergiant Fast X-ray Transients: the archetype IGR J17544-2619
Results and discussion on new INTEGRAL sources
Conclusions and perspectives
S. Chaty - ESO - 28/11/2006
Conclusions
• Obscured sources and SFXTs share similar properties:
• High Mass X-ray Binaries with O/B supergiant secondaries
• But they are not the same!
• Intrinsic absorption around the compact object / whole system
• Extension of the absorbing material (dust…)
• X-ray transient/persistent (due to geometry?)
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INTEGRAL doubled the population of massive binaries with supergiant
in our Galaxy, and revealed a class of highly absorbed binaries.
• This new population will constrain the geometry and
evolution of X-ray binaries:
• dominant population born with two very massive components?
• Primary progenitors of NS/NS or NS/BH mergers:
• Link with short/hard gamma-ray bursts?
• Good candidates of gravitational waves emitters?
S. Chaty - ESO - 28/11/2006
And then?
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Still many questions:
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No radio emission: does geometry or dust prevent jet formation?
And also, where does this dust come from?
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How were they formed?
Link with region of stellar formation of Norma arm?
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How will they evolve? (neutron star decelerated?)
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Does this circumstellar environment result from binarity or stellar evolution?
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What is the geometry of these systems (size of orbit, orbital period…)?
These sources will allow to better understand birth, evolution and geometry of HMXB
with supergiants.
To answer to these questions: new observing campaigns foreseen or pending, in high
energies and NIR/MIR, during and inbetween flares
S. Chaty - ESO - 28/11/2006
Se acabo… gracias!
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El universo es tremendamente
creativo, lo que nos obliga a
abrirnos a lo desconocido…
(Alberto Ludwig Urquieta, 1926)
S. Chaty - ESO - 28/11/2006
Naturaleza Azul,
Francisco Brugnoli