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Nature of High mass X-ray binaries in the Magellanic Clouds

Nature of High mass X-ray binaries in the Magellanic Clouds. Andry RAJOELIMANANA 1 , 2 ‏ Supervisor : Prof Phil CHARLES 1 , 2 Co-supervisor : Prof Brian Warner 1. 1 University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa .

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Nature of High mass X-ray binaries in the Magellanic Clouds

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  1. Nature of High mass X-ray binaries in the Magellanic Clouds Andry RAJOELIMANANA 1 , 2 ‏ Supervisor : Prof Phil CHARLES 1 , 2 Co-supervisor : Prof Brian Warner 1 1 University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa 2 South African Astronomical Observatory , P.O. Box 9, Observatory 7935, South Africa

  2. Outline • Introduction and Background • Why are we interested in the SMC ? • Be/X-ray binary (BeX) • A0538-66 (For Comparison) • data used • results and findings • Summary and future work

  3. Remarkable number of HMXBs in SMC • MMW ~ 50 * MSMC • 65 known HMXBs in our galaxy ~ 1 - 2 in the SMC Where are the Black Hole systems in the SMC ? ( Coe et al., 2008 )

  4. Be/X-ray binaries (BeX ) ‏ System:Be star + X-ray pulsar‏ Orbit: - wide (Porb ~ months) - eccentric (0.1<e<0.9) 2 disks :-Be equatorial disk - NS accretion disk 3 possible periods : - Pulse period (X-ray)‏ - Orbital period (X-ray and optical)‏ - Super-orbital period (Optical) such as seen in A0538-66

  5. A0538-66 : the archetypal BeX • Porb : 16.65 days • Outbursts: during optical minima • Psuper-orbital: ~ 421 days ( Be equatorial disk forms and disperses) Alcock et al., 2001 McGowan & Charles, 2003 MJD (+2448623.5) Be Star

  6. Data used - MACHO[ MAssiveCompact Halo Objects] • 1.27 m telescope • Data available : from 1992 - 2000 • ( Alcock et al., 1996) • ‏ - OGLE [ Optical Gravitational LensingExperiment] ( Udalsky et al,. 1997) • 1.3 m Warsaw telescope • Phase II : 1997 - 2000 • Phase III : 2001 - 2009 • Phase IV : First light on September 2009 MACHO + OGLE projects ~ 16 years

  7. Results and findings

  8. Long-term variations • SXP stands for Small Magellanic clouds X-ray Pulsar i > 90o - α (where α is the opening angle of the disk) i < 90o - α

  9. Outbursts amplitude vs. brightness • The strength of the outburst increases with the brightness of the source.

  10. Outbursts profiles • Transient profile (faster rise, and slower decline) • Double peaks Misalignment Supernova kick • (Brandt & Podsiadlowski, 1995)

  11. 17 Psuper-orbital • 33 Porb Rajoelimanana et al. , 2009 in preparation

  12. Super-orbital vs. Orbital periods Rajoelimanana et al. , 2009 in preparation

  13. Summary and future work • We have studied 44 SMC BeX sources. • found 17 super-orbital and 33 orbital periods. • Brightness increases with Colour (MACHO ‘blue’ – ’red’) for i < 90o - α • The outbursts amplitude vary with the brightness of the source. • outbursts profiles : - faster rise, slower decline • - double peaks (misalignment) • Future work : • Optical Spectroscopy of the SMC Be star using SAAO 1.9 m telescope ( week 20th January – 26th January). • Other SMC HMBXs (not identified as X-ray pulsar, possibly a low-mass BH) • Correlations between Optical and X-ray observations (Time of outbursts, relationship between X-ray outbursts and optical brightness ).

  14. Thank you

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