Nature of X-ray binaries in the Magellanic Clouds Andry RAJOELIMANANA 1, 2 (MSc) Supervisor : Prof Phil CHARLES 1, 2 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 to the project  X-ray binaries :  Why are we interested in Magellanic Clouds?  Objectives and method used  Some preliminary results and findings  Future work  Microquasars( SS433, … )  Conclusions  References

Background X–ray binaries :  Degenerate primary ( NS, BH)  erg s -1 < L x < erg s -1  Low Mass X-ray Binaries (LMXB)  High Mass X-ray Binaries (HMXB)

Background ( HMXBs ) Young luminous massive stars 2 types :  Supergiant X-ray binaries  Be/X-ray pulsar ( BeX ) Supergiant X-ray binaries  Supergiant companion star  Mass : M sun  P < 10 days  Accretion modes : radially outflowing stellar wind

BeX binaries ■ Be star + X-ray pulsar ■ 2 discs : - Be equatorial disc - NS accretion disc ■ 3 possible periods  Pulse period  Orbital period  Super-orbital period (such as in A )

 M MW / M SMC ~ 50  65 known HMXB in our galaxy  Now, we know 47 HMXBs in SMC Where are the Black Hole systems in the SMC ? Coe et al., in the SMC Remarkable number of HMXBs in SMC expected  Closest approach of the SMC to the LMC ~ 100 Myrs ago.

Objectives and method used  Studying the temporal properties of SMC/LMC X-ray binaries  Why are these SMC HMXBs all neutron star systems? where are the BH equivalents?  Do any of these BeX have the same properties as BeX system A which shows a 421 days superorbital periodicity? What is causing this ?  Do any of this large number of HMXBs show properties similar to the microquasar SS433 ?

Data used Data used : long-term database.  MACHO [MAssive Compact Halo Objects] ( Alcock et al., 1996) o 1.25 m telescope at Mount Stromlo Observatory, Australia o Data available : from 1992 June January  OGLE [ Optical Gravitational Lensing Experiment] ( Udalsky et al,. 1997) o 1.3 m Warsaw telescope o at Las Campanas observatory, Chile o Phase II : January ~ Dec 2000 o Phase III : June until now

Method used  We combined the light curves from MACHO, OGLE II, and OGLEIII of all known BeX. Macho data available from : OGLE II data : OGLE III data :  Run Starlink PERIOD (package) to study their temporal properties.  Lomb-Scargle periodogram (Lomb, 1976) and (Scargle, 1982 )  Phase dispersion minimization (PDM) (Stellingwerf, 1978)  Monte Carlo simulation  Fold the data

Variability of A P orb : days Super-orbital period : ~ 421 days Formation and depletion of the Be equatorial disc Alcock et al., 2001

Some results and findings

SXP6.85 (or XTE J )  Similar behaviour A  Peaks at P= 671 days

SXP293 (or RX J )  Outbursts amplitude increases with the flux  Orbital period P orb = 59 days

SXP293 (or RX J ) Peak at a period P orb = 59 days

SXP756 (or AX J , or RX J ) Periodical outbursts near periastron passages

LMXB : Supersoft X-ray sources (SSS) T BB ~ eV L bol ~ erg s -1 SSS system :  WD  Sub-giant companion  High accretion rate, > M sun yrs -1 WD burns H steadily at its surface Contraction model : (Southwell et al., 1996)  accretion rate drops Optical luminosity decreases  rise in T eff  increase in X-ray luminosity CAL 83 : X-ray emission occurs only during optical low state ( Grenier & Di Stefano, 2002)

CAL83 ( X-ray / optical correlation) X-ray data : ROSAT Optical : MACHO ( blue ) Optical low X-ray on Optical high X-ray off Greiner & Di Stefano, 2002

Lightcurve of CAL83 and RXJ [MACHO+Ogle III] Folded Lightcurve of CAL83 and RJX0513 with a P = 450 and 167 days, respectively

Power spectrum of CAL83 and RXJ Peaks at P = days Peaks at P = days

Future work Finding more sources showing similar behaviour to A using OGLE III data. Why the compact object of all of these HMXBs are neutron star? More understanding on the Supersoft X-ray binary Investigating the variability of all these Be/X-ray pulsar if any of these has a periodicity comparable to 162 days as seen in SS433. Finding the next SS433-like (continuous and precessing jets[disc]) among those HMXB in SMC. Publish the result

SS433 properties SS433 : first known X-ray binary that emits relativistic jet Only continuously emitting micro-quasar Key feature : inclination : 79 o e < 0.05 (Margon & Anderson 1989) Jet velocity : 0.26 d = 5.5 kpc (Blundell et al. 2004) P orb = days P prec = days (Abell & Margon,1979) f Ciatti et al., 1981

Conclusion Some BeX sources shows similar behaviour to A SSS CAL83 and RXJ show a variability in a timescale 450 days and days respectively. We still need more Ogle III data or other long term optical data for some sources. Investigation of the next SS433-like among those large number of HMXB needs to be done

References Grimm et al.,2003, Astron. Astrophys. Vol. 3, Suppl., 257–269 Coe et al., 2008, astro-ph v1 Gardiner L.T. & Noguchi M, 1996,MNRAS, 278,191 Alcock, C., Allsman, R.A., Alves, D. et al. 1996, MNRAS 280, L49 Alcock, C. et al. 2001, MNRAS 321, 678. Udalski, A., Kubiak, M., & Szymanski, M. 1997, Acta Astron., 47, 319 Lomb, N. R. 1976, Ap&SS, 39, 447 Stellingwerf, R. F.1978, ApJ 224, 953S Scargle, J. D. 1982, ApJ, 263,835 Greiner, J. and DiStefano, R. (2002), A&A 387, 944–54 Ciatti et al., 1981 Southwell, K.A., Livio, M., Charles, P.A., O’Donoghue, D. and Sutherland, W.J. (1996), ApJ 470, 1065–74