Sylvain CHATY (Université Paris 7 / Service d’Astrophysique, France) ESO - 28 novembre 2006 The most obscured high energy sources Or how infrared observations.

Sylvain CHATY (Université Paris 7 / Service d’Astrophysique, France) ESO - 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…

S. Chaty - ESO - 28/11/2006Plan The INTEGRAL observatory The INTEGRAL observatory Discovery of new sources in our Galaxy Discovery 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 J16318-4848 Obscured X-ray sources: the archetype IGR J16318-4848 Supergiant Fast X-ray Transients: the archetype IGR J17544-2619 Supergiant Fast X-ray Transients: the archetype IGR J17544-2619 Results and discussion on new INTEGRAL sources Results and discussion on new INTEGRAL sources Conclusions and perspectives Conclusions and perspectives

S. Chaty - ESO - 28/11/2006 INTEGRAL satellite: 2 keV – few MeV by PROTON rocket on excentric orbit Launched on 17 October 2002 by PROTON rocket on excentric orbit The INTEGRAL observatory

S. Chaty - ESO - 28/11/2006 INTEGRAL observatory 4 instruments 4 instruments 2 coded mask  telescopes: imager IBIS and spectro-imager SPI: 10keV-4MeV 2 coded mask  telescopes: imager IBIS and spectro-imager SPI: 10keV-4MeV Resolution 12’, fov 19° Resolution 12’, fov 19° 1 coded mask X telescope JEM-X: 2-100keV 1 coded mask X telescope JEM-X: 2-100keV 1 optical telescope: OMC 1 optical telescope: OMC

S. Chaty - ESO - 28/11/2006 Ground and space… Ground and space… Multi-wavelength observations (radio, infrared and X/  rays  Multi-wavelength observations (radio, infrared and X/  rays  Multi-wavelength observations

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 viewFace-on

S. Chaty - ESO - 28/11/2006 The Milky Way, our Galaxy

S. Chaty - ESO - 28/11/2006 Discovery of a new type of sources in the sky Observations of the Milky Way: IR (COBE)  -rays (INTEGRAL/ISGRI) Zoom on the center Mystery of the X-ray background Mystery of the X-ray background IBIS resolved it in many point sources IBIS resolved it in many point sources (>200: Bird et al. 2006) (>200: Bird et al. 2006) Still present at higher energies Still present at higher energies Lebrun et al. 2004Tomsick et al. 2004 New sources towards the Norma arm of the Galaxy, previously unknown… And this Norma arm is full of star formation regions!

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 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. X-RAY BINARIES

S. Chaty - ESO - 28/11/2006 131 149 New : -0.9 HMXB : -0.6 HMXB+new: -0.6 HMXB (XTE): -0.6±0.1 Galactic distribution Walter et al. 2006 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)

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: To observe in X/  rays is not enough: ISGRI localisation not enough to identify the counterpart ISGRI 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 absorption (interstellar dust and gas) 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 Programme of study of new high energy binary sources Identification of counterparts, nature of system, compact object, companion star, distance, accretion type… Identification of counterparts, nature of system, compact object, companion star, distance, accretion type… characterize presence, temperature, composition of dust characterize presence, temperature, composition of dust Photometry/Spectroscopy on 15 INTEGRAL sources Photometry/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  m): La Silla (3.5m-NTT) Near-infrared SOFI (1-2.5  m): La Silla (3.5m-NTT) Mid-Infrared VISIR (5-20  m): Paranal (8m-VLT/UT3) Mid-Infrared VISIR (5-20  m): Paranal (8m-VLT/UT3) 2 modes of observations (European Southern Observatory): 2 modes of observations (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

S. Chaty - ESO - 28/11/2006 The Obscured INTEGRAL source IGR J16318-4848: From INTEGRAL high energy … From INTEGRAL high energy … …to Optical/MIR observations. …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 1 st source discovered by INTEGRAL (IBIS/ISGRI) on 29 January 2003 1 st source discovered by INTEGRAL (IBIS/ISGRI) on 29 January 2003 Position: Position: (l,b)~(336°, 0.5°) (l,b)~(336°, 0.5°) RA=16 h 31.8 m, DEC=-48°48’ RA=16 h 31.8 m, DEC=-48°48’ Localisation accuracy: 2’ with INTEGRAL (Moon: 30’!) Localisation accuracy: 2’ with INTEGRAL (Moon: 30’!) Non-absorbed Flux: 15-40 keV Flux: 50-100 mCrab (Courvoisier et al. 2003) 15-40 keV Flux: 50-100 mCrab (Courvoisier et al. 2003) L 5kpc = 1-20 10 36 erg/s INTEGRAL/ISGRI (15-40 keV) Norma arm region image (Walter et al. 2003)

S. Chaty - ESO - 28/11/2006 ToO observations with XMM-Newton XMM observations (28ks ToO on 10/02/2003): 4” localisation XMM observations (28ks ToO on 10/02/2003): 4” localisation Comptonised spectrum: N h =1.84+/-0.06x10 24 cm -2 N h =1.84+/-0.06x10 24 cm -2 kT = 9±0.5 keV Photon index ~ 2 Photon index ~ 2 Strong photoelectric absorption: Strong photoelectric absorption: Fe absorption edge at 7.1keV Fe absorption edge at 7.1keV Fe K , K , Ni K  Fluorescence lines Fe K , K , Ni K  Fluorescence lines Variability: RXTE: no oscillation detected 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 10 13 cm (Walter et al. 2003) Variations of lines and continuum on temporal scale of 1000s: size of emitting region < 3 x 10 13 cm (Walter et al. 2003) X-ray properties ~ CI Cam, Vela X1, GX 301-2 X-ray properties ~ CI Cam, Vela X1, GX 301-2 EPIC PN, EPIC MOS2 and ISGRI spectra (Matt & Guainazzi 2003; Walter et al. 2003)

S. Chaty - ESO - 28/11/2006 Discovery of the optical/NIR counterpart photometric observations on 23-25/02/2003 photometric observations on 23-25/02/2003 Discovery of the R, I, Z counterpart 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 Confirmation of NIR counterpart proposed by Walter et al. 2003 by an improved astrometry 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

S. Chaty - ESO - 28/11/2006 B, V, R, I, J, H, K magnitudes of candidate and 4 neighbours 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 Absorption in optical/NIR

S. Chaty - ESO - 28/11/2006 NIR spectroscopy: 0.95-2.5  m Unusual spectrum very rich in many strong emission lines Strong H (Br, Pa, Pf) and HeI (P-Cyg): emanate from dense, ionised wind Strong H (Br, Pa, Pf) and HeI (P-Cyg): emanate from dense, ionised wind He II: highly excited region in vicinity of compact object He II: highly excited region in vicinity of compact object [FeII]: indication of shock heated material [FeII]: indication of shock heated material FeII => densities > 10 5 -10 6 cm -3 FeII => densities > 10 5 -10 6 cm -3 NaI: cool/dense regions shielded from stellar and compact object radiation NaI: 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: High-mass X-ray binary system, similar to CI Cam=> 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: Fit parameters: L ~ 10 6 d 2 6kpc L Sun T = 20 250 K M = 30 M Sun 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 Model: Model: Companion star: sgB[e], T=23500 K, R=20.4 Rsun = 15 10 6 km Companion star: sgB[e], T=23500 K, R=20.4 Rsun = 15 10 6 km Dust component: T=900K, R=12 R * = 1ua Dust component: T=900K, R=12 R * = 1ua Av=17.6, D=1.2 kpc Av=17.6, D=1.2 kpc Result: Fit  2 /dof=89.4/99 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. Need for extra (e.g. dust) component. Extension of this dust component seems to suggest that it is enshrouding the whole binary system. Unusual absorption: cocoon of dust? ESO/NTT Spitzer VLT/VISIR

S. Chaty - ESO - 28/11/2006 Nature of the compact object Correlation in LHS black hole systems between X- ray/radio flux densities: 50-100 mCrab X-ray flux => 10 mJy radio flux with low/hard X-ray emission => compact object is a neutron star 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 Gallo et al. 2004 But correlation not always verified…

S. Chaty - ESO - 28/11/2006 Nature of IGR J16318-4848 High Mass X-ray Binary system: High Mass X-ray Binary system: neutron star + early-type supergiant B[e] star the 2nd HMXB with sgB[e] after CI Cam Distance 1 to 6 kpc Absorption: 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 The SFXT (Supergiant Fast X-ray Transient) source IGR J17544-2619… From INTEGRAL high energy … From INTEGRAL high energy … …to Optical/MIR observations. …to Optical/MIR observations. (Chaty & Rahoui 2006, proc. INTEGRAL; Pellizza, Chaty, Negueruela, 2006, A&A) (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 10 22, another highly absorbed galactic XB? (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! Negueruela, Smith, Reig, Chaty, Torrejon, 2005

S. Chaty - ESO - 28/11/2006 IGR J17544-2619 optical/NIR counterpart IGR J17544-2619 (Pellizza, Chaty, Negueruela, 2006, A&A) 2’ J-band image 5.5’x5.5’ INTEGRAL: 2’ error radius ROSAT: 23” error radius XMM: 4” error radius Image Ks 1RXS J175428: ROSAT source not connected with IGR J17544 Chandra: 0.4’’ Ks-band image XMM: 4” error radius

S. Chaty - ESO - 28/11/2006 1 bright candidate (B) identified in USNO & 2MASS 3 very faint candidates (F1-3): foreground dwarf stars? 1 extended object (E) high-z galaxy? IGR J17544-2619 optical/NIR counterpart

S. Chaty - ESO - 28/11/2006 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) Candidate B spectrum

S. Chaty - ESO - 28/11/2006 IGR J17544-2619 Optical -> mid-infrared SED Model: Model: Companion star: O9Ib, T=30500K, R=21.9 Rsun Companion star: O9Ib, T=30500K, R=21.9 Rsun Av=5.9, D=3.9kpc Av=5.9, D=3.9kpc Fit result:  2 /dof=84/48 Fit result:  2 /dof=84/48 no need for extra (e.g. dust) component no need for extra (e.g. dust) component Presence of dust? ESO/NTT Spitzer VLT/VISIR

S. Chaty - ESO - 28/11/2006 HMXB with companion of 25-28 M  supergiant O9Ib Presence of mild stellar wind Compact object: likely Neutron Star (in’t zand 2005) Distance: 3-4 kpc Faint intrinsic absorption (10 22 cm -2 ), Long P outburst =165d Detection of flux variations during quiescence Archetype of “SFXTs”: Supergiant Fast X-ray transients: O/B supergiant companions, O/B supergiant companions, Compact object = BH or NS, Compact object = BH or NS, faint quiescent emission, outbursts lasting only hours. faint quiescent emission, outbursts lasting only hours. Nature of IGR J17544-2619

S. Chaty - ESO - 28/11/2006 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. Results

S. Chaty - ESO - 28/11/2006 Supergiant Fast X-ray Transients (SFXT): A new class of massive X-ray binaries 6 SFXTs: 6 SFXTs: XTE J1739-302, IGR J17544-2619, IGR J16465-4507, AX J1841.0-0536, IGR J11215-5952, SAX J1818.6-1703 8 Candidate SFXTs: 8 Candidate SFXTs: IGR J08408-4503, IGR J16195-4945, IGR J16418-4532, IGR J16479- 4514, IGR J17407-2808, XTE J1743-363, AX J1749.1-2733, XTE J1901+014

S. Chaty - ESO - 28/11/2006 Characteristics of the studied INTEGRAL sources SourceRegionPspinNhNhgalNhEB-VPorb Persistent sources IGRJ16318-4848Norma1932.1<4.2 IGRJ16320-4751Norma1250s182.19d IGRJ16393-4641Norma912s242.2<2.7 IGRJ17252-3616GC413s151.5<5.39.7d IGRJ17597-2201GC51.2<2.9 IGRJ18027-2016GC139s91.1<2.14.6d Transient sources IGRJ16358-4726Norma5880s392.2<4.2 IGR J16418-4532 Norma965s102.0<3.6 IGRJ16465-4507Norma228s601.6<1.0 IGR J16479-4514 Norma82.1<4.8 IGRJ17544-2619GCNS21.4<2.5165d? Zurita 2006 adapted

S. Chaty - ESO - 28/11/2006 Results of 2004 NTT-SOFI/EMMI and 2005/2006 Paranal UT3-VISIR observations SourceType Spectral type PAH1 (8.59  m) mJyPAH2 (11.25  m) mJy Q2 (18.72  m) mJy Dust Temp (K) Dust Radius (R*) IGR J16195-4945 SFXT?/OBSOB<6<8<509506.1 IGR J16318-4848 OBSsgB[e]40932217290011.9 IGR J16320-4751 OBSOB126- IGR J17391-3021 SFXTO8Iab(f)7046- IGR J17544-2619 SFXTO9Ib3620- IGR J16207-5129 B0 22 (extended) 9<53 IGR J16358-4726 OBS<7--88010.1 IGR J16418-4532 SFXT<6-- IGR J16465-4507 SFXT/OBS?B0.5I95- IGR J16479-4514 SFXTOB127- IGR J17252-3616 OBSOB62- IGR J17597-2201 Late?<6-- IGR J18027-2016 sgOB<6-- IGR J19140+0951 OB? 35 (2 sources) 19 (2 sources) - 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!

S. Chaty - ESO - 28/11/2006 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 N H >10 23 cm -2 X-ray absorption >> IR => absorbing matter local to neutron star N H 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) The systems

S. Chaty - ESO - 28/11/2006 Nature of systems: Corbet Diagramme 80% of Norma sources are X-ray pulsars High spin periods Star P orb =10d, M=20M sol, a=50R sol < R dust (R dust =240R Sun for IGR J16318) Underfilled Roche lobe Supergiants 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 A new population of sources of our Galaxy revealed by INTEGRAL ~15 sources with same characteristics: not by chance! ~15 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 (~IGR J16318) : 2) Or enshrouding the whole system: obscured sources (~IGR J16318) : neutron star orbits within a dense equatorial wind neutron star orbits within a dense equatorial wind density 10 11–12 cm –3 density 10 11–12 cm –3 Disc thickness 10 12–13 cm (10-100 R Sun ) Disc thickness 10 12–13 cm (10-100 R Sun ) Disc radius 10 13–14 cm (1-10 a.u.) Disc radius 10 13–14 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

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?) 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?

S. Chaty - ESO - 28/11/2006 And then? Still many questions: 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 binarity or stellar evolution? Does this circumstellar environment result from binarity or stellar evolution? These sources will allow to better understand birth, evolution and geometry of HMXB with supergiants. 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 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 Naturaleza Azul, Francisco Brugnoli Francisco Brugnoli Francisco Brugnoli Se acabo… gracias! El universo es tremendamente creativo, lo que nos obliga a abrirnos a lo desconocido… El universo es tremendamente creativo, lo que nos obliga a abrirnos a lo desconocido… (Alberto Ludwig Urquieta, 1926)

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 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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Presentation on theme: "Sylvain CHATY (Université Paris 7 / Service d’Astrophysique, France) ESO - 28 novembre 2006 The most obscured high energy sources Or how infrared observations."— Presentation transcript:

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