1 / 49

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…. Sylvain CHATY (Université Paris 7 / Service d’Astrophysique, France) ESO - 28 novembre 2006. Plan. The INTEGRAL observatory

lionel-glass
Download Presentation

Sylvain CHATY (Université Paris 7 / Service d’Astrophysique, France) ESO - 28 novembre 2006

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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

  2. 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

  3. 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

  4. 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

  5. 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

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

  7. 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

  8. The Milky Way, our Galaxy (seen from inside) S. Chaty - ESO - 28/11/2006

  9. The Milky Way, our Galaxy (seen from outside) Side view Face-on S. Chaty - ESO - 28/11/2006

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

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

  12. 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

  13. 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

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

  15. Galactic distribution 131 • 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) 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

  16. Discovery of a new type of sources • How to identify all these new INTEGRAL sources? • To observe in X/g 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) => Observe in INFRARED S. Chaty - ESO - 28/11/2006

  17. ESO observations • 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

  18. 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

  19. 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

  20. 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

  21. 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 1036 erg/s INTEGRAL/ISGRI (15-40 keV) Norma arm region image (Walter et al. 2003) S. Chaty - ESO - 28/11/2006

  22. ToO observations with XMM-Newton • XMM observations (28ks ToO on 10/02/2003): 4”localisation • Comptonised spectrum: • Nh=1.84+/-0.06x1024 cm-2 • kT = 9±0.5 keV • Photon index ~ 2 • Strong photoelectric absorption: • Fe absorption edge at 7.1keV • Fe K, K, Ni K Fluorescence lines • Variability: • 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 EPIC PN, EPIC MOS2 and ISGRI spectra (Matt & Guainazzi 2003; Walter et al. 2003) S. Chaty - ESO - 28/11/2006

  23. Discovery of the optical/NIR counterpart • 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 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 Target of Opportunity S. Chaty - ESO - 28/11/2006

  24. Absorption in optical/NIR • B, V, R, I, J, H, K magnitudes of candidate and 4 neighbours • IGR source exhibits unusual 17.4magabsorption • 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

  25. 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

  26. 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

  27. 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

  28. IGR J16318-4848 Optical -> mid-infrared SED Spitzer • Unusual absorption: • cocoon of dust? • 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. ESO/NTT VLT/VISIR S. Chaty - ESO - 28/11/2006

  29. 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 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

  30. Nature of IGR J16318-4848 • 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

  31. 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

  32. 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

  33. IGR J17544-2619 Recurrent transient X-ray source discovered by INTEGRAL (09/2003) near the Galactic center (Sunyaev et al. 2003, ATel 190) Negueruela, Smith, Reig, Chaty, Torrejon, 2005 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? (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

  34. 2’ J-band image 5.5’x5.5’ INTEGRAL: 2’ error radius ROSAT: 23” error radius XMM: 4” error radius Image Ks IGR J17544-2619 optical/NIR counterpart 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) Chandra: 0.4’’ S. Chaty - ESO - 28/11/2006

  35. 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

  36. 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

  37. IGR J17544-2619 Optical -> mid-infrared SED ESO/NTT • 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 Presence of dust? Spitzer VLT/VISIR S. Chaty - ESO - 28/11/2006

  38. Nature of IGR J17544-2619 • 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 (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

  39. 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

  40. 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

  41. Characteristics of the studied INTEGRAL sources Zurita 2006 adapted S. Chaty - ESO - 28/11/2006

  42. Results of 2004 NTT-SOFI/EMMI and 2005/2006 Paranal UT3-VISIR observations 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

  43. 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

  44. 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

  45. 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

  46. 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

  47. 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? • 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

  48. 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? • 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? • 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 Multi-wavelength study necessary to reveal the nature of these sources... S. Chaty - ESO - 28/11/2006

  49. Se acabo… gracias! • El universo es tremendamente creativo, lo que nos obliga a abrirnos a lo desconocido… (Alberto Ludwig Urquieta, 1926) Naturaleza Azul, Francisco Brugnoli S. Chaty - ESO - 28/11/2006

More Related