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

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

MMW ~ 50 * MSMC

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

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

Be/X-ray binaries (BeX )

• Porb : 16.65 days• Outbursts: during optical minima• Psuper-orbital : ~ 421 days ( Be equatorial disk forms and disperses)

A0538-66 : the archetypal BeX

Alcock et al., 2001

MJD (+2448623.5)

McGowan & Charles, 2003

BeStar

Data used

- MACHO [ MAssive Compact Halo Objects]o 1.27 m telescopeo 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 - 2000o Phase III : 2001 - 2009o Phase IV : First light on September 2009

MACHO + OGLE projects ~ 16 years

Resultsand findings

Long-term variations

i > 90o - α (where α is the opening angle of the disk)

i < 90o - α

• SXP stands for Small Magellanic clouds X-ray Pulsar

Outbursts amplitude vs. brightness

• The strength of the outburst increases with the brightness of the source.

Outbursts profiles

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

Rajoelimanana et al. , 2009 in preparation 17 Psuper-orbital

33 Porb

Super-orbital vs. Orbital periods

Rajoelimanana et al. , 2009 in preparation

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 ).

Summary and future work

Thank you