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

4. System : Be star + X-ray pulsar ‏ Orbit : - wide ( P orb ~ 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 Be/X-ray binaries ( BeX ) ‏

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

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

7. Results and findings

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

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. Rajoelimanana et al., 2009 in preparation  17 P super-orbital  33 P orb

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

13.  We have studied 44 SMC BeX sources.  found 17 super-orbital and 33 orbital periods.  Brightness increases with Colour (MACHO ‘blue’ – ’red’) for i < 90 o - 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 20 th January – 26 th 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 ). Summary and future work

14. Thank you