Sylvain CHATY Sylvain CHATY (Université Paris 7 / Service d’Astrophysique, France) ESO ESO - 28 novembre 2006 - 28 novembre 2006 The most obscured high energy sources Or how infrared observations allow to reveal mysteries of the most obscured X-ray sources of our Galaxy…
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Sylvain CHATY (Université Paris 7 / Service d’Astrophysique, France) ESO - 28 novembre 2006 The most obscured high energy sources Or how infrared observations.
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Sylvain CHATYSylvain CHATY(Université Paris 7 / Service d’Astrophysique, France)
ESOESO - 28 novembre 2006 - 28 novembre 2006
The most obscured high energy sources
Or how infrared observations allow to reveal mysteries of the most obscured X-ray sources of our Galaxy…
The INTEGRAL observatoryThe INTEGRAL observatory Discovery of new sources in our GalaxyDiscovery of new sources in our Galaxy How to understand their nature?How to understand their nature? Multi-wavelength optical/NIR/MIR observations:Multi-wavelength optical/NIR/MIR observations:
Obscured X-ray sources: the archetype IGR J16318-4848Obscured X-ray sources: the archetype IGR J16318-4848 Supergiant Fast X-ray Transients: the archetype IGR J17544-Supergiant Fast X-ray Transients: the archetype IGR J17544-
26192619 Results and discussion on new INTEGRAL sourcesResults and discussion on new INTEGRAL sources Conclusions and perspectivesConclusions and perspectives
The INTEGRAL observatoryThe INTEGRAL observatory Discovery of new sources in our GalaxyDiscovery of new sources in our Galaxy How to understand their nature?How to understand their nature? Multi-wavelength optical/NIR/MIR observations:Multi-wavelength optical/NIR/MIR observations:
Obscured X-ray sources: the archetype IGR J16318-4848Obscured X-ray sources: the archetype IGR J16318-4848 Supergiant Fast X-ray Transients: the archetype IGR J17544-Supergiant Fast X-ray Transients: the archetype IGR J17544-
26192619 Results and discussion on new INTEGRAL sourcesResults and discussion on new INTEGRAL sources Conclusions and perspectivesConclusions and perspectives
The INTEGRAL observatoryThe INTEGRAL observatory Discovery of new sources in our GalaxyDiscovery of new sources in our Galaxy How to understand their nature?How to understand their nature? Multi-wavelength optical/NIR/MIR observations:Multi-wavelength optical/NIR/MIR observations:
Obscured X-ray sources: the archetype IGR J16318-4848Obscured X-ray sources: the archetype IGR J16318-4848 Supergiant Fast X-ray Transients: the archetype IGR J17544-Supergiant Fast X-ray Transients: the archetype IGR J17544-
26192619 Results and discussion on new INTEGRAL sourcesResults and discussion on new INTEGRAL sources Conclusions and perspectivesConclusions and perspectives
The INTEGRAL observatoryThe INTEGRAL observatory Discovery of new sources in our GalaxyDiscovery of new sources in our Galaxy How to understand their nature?How to understand their nature? Multi-wavelength optical/NIR/MIR observations:Multi-wavelength optical/NIR/MIR observations:
Obscured X-ray sources: the archetype IGR J16318-4848Obscured X-ray sources: the archetype IGR J16318-4848 Supergiant Fast X-ray Transients: the archetype IGR J17544-Supergiant Fast X-ray Transients: the archetype IGR J17544-
26192619 Results and discussion on new INTEGRAL sourcesResults and discussion on new INTEGRAL sources Conclusions and perspectivesConclusions and perspectives
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 X-ray Binaries (HMXBs). Optical companion with spectral type O or B. Mass transfer via decretion disk (Be stars) or via strong wind or Roche-lobe overflow (OB SG). 131 known HMXBs.
Low Mass X-ray Binaries (LMXBs). Optical companion with spectral type later than B. Mass transfer via Roche-lobe overflow.149 known LMXBs.
Discovery of a new type of sourcesDiscovery of a new type of sources
How to identify all these new INTEGRAL sources?
To observe in X/To observe in X/ rays is not enough: rays is not enough: ISGRI localisation not enough to identify the counterpartISGRI localisation not enough to identify the counterpart
To observe in optical is difficult:To observe in optical is difficult: Sources mainly in the plane (centre) of the Galaxy: too much Sources mainly in the plane (centre) of the Galaxy: too much
absorption (interstellar dust and gas)absorption (interstellar dust and gas)
Programme of study of new high energy binary sourcesProgramme of study of new high energy binary sources Identification of counterparts, nature of system, compact object, companion star, Identification of counterparts, nature of system, compact object, companion star,
distance, accretion type…distance, accretion type… characterize presence, temperature, composition of dustcharacterize presence, temperature, composition of dust
Photometry/Spectroscopy on 15 INTEGRAL sourcesPhotometry/Spectroscopy on 15 INTEGRAL sources
3 domains:3 domains: Optical EMMI (400-800 nm): La Silla (3.5m-NTT)Optical EMMI (400-800 nm): La Silla (3.5m-NTT) Near-infrared SOFI (1-2.5 Near-infrared SOFI (1-2.5 m): La Silla (3.5m-NTT)m): La Silla (3.5m-NTT) Mid-Infrared VISIR (5-20Mid-Infrared VISIR (5-20m): Paranal (8m-VLT/UT3)m): Paranal (8m-VLT/UT3)
2 modes of observations 2 modes of observations (European Southern Observatory)(European Southern Observatory):: « Target of Opportunity mode»: ~16h/semester to observe new binary systems« 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« Visitor mode »: 3 nights 07/2004, 1 night 06/2005, 2 nights 06/2006
The INTEGRAL observatoryThe INTEGRAL observatory Discovery of new sources in our GalaxyDiscovery of new sources in our Galaxy How to understand their nature?How to understand their nature? Multi-wavelength optical/NIR/MIR observations:Multi-wavelength optical/NIR/MIR observations:
Obscured X-ray sources: the archetype IGR J16318-4848Obscured X-ray sources: the archetype IGR J16318-4848 Supergiant Fast X-ray Transients: the archetype IGR J17544-Supergiant Fast X-ray Transients: the archetype IGR J17544-
26192619 Results and discussion on new INTEGRAL sourcesResults and discussion on new INTEGRAL sources Conclusions and perspectivesConclusions and perspectives
The INTEGRAL observatoryThe INTEGRAL observatory Discovery of new sources in our GalaxyDiscovery of new sources in our Galaxy How to understand their nature?How to understand their nature? Multi-wavelength optical/NIR/MIR observations:Multi-wavelength optical/NIR/MIR observations:
Obscured X-ray sources: the archetype IGR J16318-4848Obscured X-ray sources: the archetype IGR J16318-4848 Supergiant Fast X-ray Transients: the archetype IGR J17544-Supergiant Fast X-ray Transients: the archetype IGR J17544-
26192619 Results and discussion on new INTEGRAL sourcesResults and discussion on new INTEGRAL sources Conclusions and perspectivesConclusions and perspectives
Strong photoelectric absorption:Strong photoelectric absorption: Fe absorption edge at 7.1keVFe absorption edge at 7.1keV Fe KFe K, K, K, Ni K, Ni K Fluorescence lines Fluorescence lines
Variability: RXTE: no oscillation detectedRXTE: 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 Variations of lines and continuum on
temporal scale of 1000s: size of emitting temporal scale of 1000s: size of emitting region < 3 x 10region < 3 x 1013 13 cm cm (Walter et al. 2003)(Walter et al. 2003)
X-ray properties ~ CI Cam, Vela X1, GX X-ray properties ~ CI Cam, Vela X1, GX 301-2301-2
EPIC PN, EPIC MOS2 and ISGRI spectra(Matt & Guainazzi 2003; Walter et al. 2003)(Matt & Guainazzi 2003; Walter et al. 2003)
Discovery of the optical/NIR counterpartDiscovery of the optical/NIR counterpart
photometric observations on 23-photometric observations on 23-25/02/200325/02/2003
Discovery of the R, I, Z counterpartDiscovery of the R, I, Z counterpart Comparison Comparison with USNOUSNO B1.0 plate R band: only one of the two : only one of the two
sources varied in the XMM EPIC 4” uncertainty circle.sources varied in the XMM EPIC 4” uncertainty circle. Confirmation of NIR counterpart proposed by Walter et al. Confirmation of NIR counterpart proposed by Walter et al.
2003 by an improved astrometry2003 by an improved astrometry
NIR spectroscopy: 0.95-2.5 NIR spectroscopy: 0.95-2.5 mm
Unusual spectrum very rich in many strong emission linesUnusual spectrum very rich in many strong emission lines Strong H (Br, Pa, Pf) and HeI (P-Cyg): emanate from dense, ionised windStrong H (Br, Pa, Pf) and HeI (P-Cyg): emanate from dense, ionised wind• He II: highly excited region in vicinity of compact objectHe II: highly excited region in vicinity of compact object• [FeII]: indication of shock heated material[FeII]: indication of shock heated material• FeII => densities > 10FeII => densities > 1055-10-1066 cm cm-3-3
• NaI: cool/dense regions shielded from stellar and compact object radiationNaI: cool/dense regions shielded from stellar and compact object radiation• Lines originate from different media (various densities, temperature)Lines originate from different media (various densities, temperature)
• Highly complex, stratified circumstellar environment + enveloppe, wind…Highly complex, stratified circumstellar environment + enveloppe, wind…• =>=> luminous post main sequence star: most likely an uncl/sgB[e] star: luminous post main sequence star: most likely an uncl/sgB[e] star:
High-mass X-ray binary system,High-mass X-ray binary system, similar to CI Camsimilar to CI Cam
Position computed for 2 Position computed for 2 different absorptions different absorptions (11.8 and 17.4 mag) (11.8 and 17.4 mag) and for distances and for distances between 1 and 8 kpcbetween 1 and 8 kpc
Parameter space indicate Parameter space indicate a hot supergiant a hot supergiant between 1 and 6 kpcbetween 1 and 6 kpc
Absorption <17.4mag Absorption <17.4mag
Compatible with OB type Compatible with OB type supergiantssupergiants
Need for extra (e.g. dust) component. Need for extra (e.g. dust) component. Extension of this dust component Extension of this dust component seems to suggest that it is enshrouding the whole binary system.seems to suggest that it is enshrouding the whole binary system.
Nature of the compact objectNature of the compact objectCorrelation in LHS black Correlation in LHS black
hole systems between X-hole systems between X-ray/radio flux densities:ray/radio flux densities:50-100 mCrab X-ray flux 50-100 mCrab X-ray flux => 10 mJy radio 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 with low/hard X-ray emission => compact emission => compact object is a neutron starobject is a neutron star
Gallo et al. 2004But correlation not always verified…
Nature of IGR J16318-4848Nature of IGR J16318-4848
High Mass X-ray Binary system:High Mass X-ray Binary system: neutron star + early-type supergiant B[e] starneutron star + early-type supergiant B[e] star
the 2nd HMXB with sgB[e] after CI Camthe 2nd HMXB with sgB[e] after CI Cam Distance 1 to 6 kpcDistance 1 to 6 kpc
Absorption:Absorption: in X-rays 2 orders of magnitude > IRin X-rays 2 orders of magnitude > IR in opt/IR 2 orders of magnitude > line of sightin opt/IR 2 orders of magnitude > line of sight
System surrounded by dense and absorbing dusty System surrounded by dense and absorbing dusty circumstellar material/enveloppe, + 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.
The INTEGRAL observatoryThe INTEGRAL observatory Discovery of new sources in our GalaxyDiscovery of new sources in our Galaxy How to understand their nature?How to understand their nature? Multi-wavelength optical/NIR/MIR observations:Multi-wavelength optical/NIR/MIR observations:
Obscured X-ray sources: the archetype IGR J16318-4848Obscured X-ray sources: the archetype IGR J16318-4848 Supergiant Fast X-ray Transients: the archetype IGR J17544-Supergiant Fast X-ray Transients: the archetype IGR J17544-
26192619 Results and discussion on new INTEGRAL sourcesResults and discussion on new INTEGRAL sources Conclusions and perspectivesConclusions and perspectives
Blue supergiant O9 Ib (25-28 M, T~32000K)High-mass X-ray binaryExistence 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)
The INTEGRAL observatoryThe INTEGRAL observatory Discovery of new sources in our GalaxyDiscovery of new sources in our Galaxy How to understand their nature?How to understand their nature? Multi-wavelength optical/NIR/MIR observations:Multi-wavelength optical/NIR/MIR observations:
Obscured X-ray sources: the archetype IGR J16318-4848Obscured X-ray sources: the archetype IGR J16318-4848 Supergiant Fast X-ray Transients: the archetype IGR J17544-Supergiant Fast X-ray Transients: the archetype IGR J17544-
26192619 Results and discussion on new INTEGRAL sourcesResults and discussion on new INTEGRAL sources Conclusions and perspectivesConclusions and perspectives
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!
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)
Nature of systems: Nature of systems: Corbet DiagrammeCorbet Diagramme 80% of Norma sources are X-ray pulsars High spin periods Star Porb=10d, M=20Msol, a=50Rsol < Rdust
So, what are these sources?Different geometries, different possible scenarii
A new population of sources of our Galaxy revealed by INTEGRALA new population of sources of our Galaxy revealed by INTEGRAL ~15 ~15 sources with same characteristics: not by chance!sources with same characteristics: not by chance! 80% are neutron stars orbiting around super-giant stars (hot, massive, luminous):80% are neutron stars orbiting around super-giant stars (hot, massive, luminous):
Presence of a cocoon of dense and absorbing dust concentrated:Presence of a cocoon of dense and absorbing dust concentrated:
1) Either around the 1) Either around the compact object: SFXTs (~IGR J17544):: Wide orbit, neutron star penetrates inside the atmosphere/envelope of companion star, causing outbursts?Wide orbit, neutron star penetrates inside the atmosphere/envelope of companion star, causing outbursts?
2) Or enshrouding the whole system: obscured sources (2) Or enshrouding the whole system: obscured sources (~IGR J16318) :~IGR J16318) : neutron star orbits within a dense equatorial windneutron star orbits within a dense equatorial wind density 10density 1011–1211–12 cm cm–3–3
Disc thickness 10Disc thickness 1012–1312–13 cm (10-100 R cm (10-100 RSunSun)) Disc radius 10Disc radius 1013–1413–14 cm (1-10 a.u.) cm (1-10 a.u.)
The answer will be given by orbital periods of these sources…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
The INTEGRAL observatoryThe INTEGRAL observatory Discovery of new sources in our GalaxyDiscovery of new sources in our Galaxy How to understand their nature?How to understand their nature? Multi-wavelength optical/NIR/MIR observations:Multi-wavelength optical/NIR/MIR observations:
Obscured X-ray sources: the archetype IGR J16318-4848Obscured X-ray sources: the archetype IGR J16318-4848 Supergiant Fast X-ray Transients: the archetype IGR J17544-Supergiant Fast X-ray Transients: the archetype IGR J17544-
26192619 Results and discussion on new INTEGRAL sourcesResults and discussion on new INTEGRAL sources Conclusions and perspectivesConclusions and perspectives
• 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?)
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?dominant population born with two very massive components?• Primary progenitors of NS/NS or NS/BH mergers:Primary progenitors of NS/NS or NS/BH mergers:
• Link with short/hard gamma-ray bursts?Link with short/hard gamma-ray bursts?• Good candidates of gravitational waves emitters?Good candidates of gravitational waves emitters?
What is the geometry of these systems (size of orbit, orbital period…)?
No radio emission: does geometry or dust prevent jet formation? And also, where does this dust come from?And also, where does this dust come from?
How were they formed? Link with region of stellar formation of Norma arm?
How will they evolve? (neutron star decelerated?)
Does this circumstellar environment result from Does this circumstellar environment result from binarity or stellar evolution?binarity or stellar evolution?
These sources will allow to better understand birth, evolution and geometry These sources will allow to better understand birth, evolution and geometry of HMXB with supergiants.of HMXB with supergiants.
To answer to these questions: new observing campaigns foreseen or pending, To answer to these questions: new observing campaigns foreseen or pending, in high energies and NIR/MIR, during and inbetween flaresin high energies and NIR/MIR, during and inbetween flares
Naturaleza Azul, Naturaleza Azul, Francisco Brugnoli
Se acabo… gracias!Se acabo… gracias!
El universo es tremendamente El universo es tremendamente creativo, lo que nos obliga a creativo, lo que nos obliga a abrirnos a lo desconocido…abrirnos a lo desconocido…(Alberto Ludwig Urquieta, 1926)(Alberto Ludwig Urquieta, 1926)