Nature of X-ray binaries in the Magellanic Clouds

1. 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

2. 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

3. Background X–ray binaries : • Degenerate primary ( NS , BH) • 1035 erg s-1 < Lx < 1039 erg s-1 • Low Mass X-ray Binaries (LMXB) • High Mass X-ray Binaries (HMXB)

4. 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 : 18 - 20 Msun • P < 10 days • Accretion modes : radiallyoutflowing stellar wind

5. 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 A0538-66)

6. Remarkable number of HMXBs in SMC • MMW / MSMC ~ 50 • 65 known HMXB in our galaxy • Now, we know 47 HMXBs in SMC 1 - 2 in the SMC expected Where are the Black Hole systems in the SMC ? Coe et al., 2008 • Closest approach of the SMC to the LMC ~ 100 Myrs ago.

7. 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 A0538-66 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 ?

8. Data used • Data used : long-term database. • MACHO [MAssive Compact Halo Objects] ( Alcock et al., 1996) • 1.25 m telescope at Mount Stromlo Observatory, Australia • Data available : from 1992 June - 2000 January • OGLE [ Optical Gravitational Lensing Experiment] ( Udalsky et al,. 1997) • 1.3 m Warsaw telescope • at Las Campanas observatory, Chile • Phase II : January 1997 - ~ Dec 2000 • Phase III : June 2001 - until now

9. Method used • We combined the light curves from MACHO, OGLE II, and OGLEIII of all known BeX. Macho data available from : http://wwwmacho.anu.edu.au/Data/MachoData.html OGLE II data : http://ogle.astrouw.edu.pl/ OGLE III data : http://ogle.astrouw.edu.pl/ogle3/xrom/xrom.html • 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

10. Variability of A0538-66 • Porb : 16.65 days • Super-orbital period : ~ 421 days • Formation and depletion of the Be equatorial disc Alcock et al., 2001

11. Some results and findings

12. SXP6.85 (or XTE J0103-728) • Similar behaviour A0538-66 • Peaks at P= 671 days

13. SXP293 (or RX J0058.2-7231) • Outbursts amplitude increases with the flux • Orbital period Porb = 59 days

14. SXP293(or RX J0058.2-7231) Peak at a period Porb = 59 days

15. SXP756 (or AX J0049.4-7323, or RX J0049.7-7323) Periodical outbursts near periastron passages

16. LMXB :Supersoft X-ray sources (SSS) • TBB ~ 20-50 eV • Lbol ~ 1037 - 1038erg s-1 • SSS system : • WD • Sub-giant companion • High accretion rate , > 10-7Msun yrs-1 • WD burns H steadily at its surface • Contraction model : (Southwell et al., 1996) • accretion rate drops Optical luminosity decreases • rise in Teff • increase in X-ray luminosity • CAL 83 : X-ray emission occurs only during optical low state ( Grenier & Di Stefano, 2002)

17. 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

18. Lightcurve of CAL83 and RXJ0513.9-6951 [MACHO+Ogle III] Folded Lightcurve of CAL83 and RJX0513 with a P = 450 and 167 days , respectively

19. Power spectrum of CAL83 and RXJ0513.9-6951 Peaks at P = 167.94 days Peaks at P = 450.24 days

20. Future work • Finding more sources showing similar behaviour to A0538-66 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

21. SS433 properties • SS433 : first known X-ray binary that emits relativistic jet • Only continuously emitting micro-quasar • Key feature : inclination : 79o e < 0.05 (Margon & Anderson 1989) Jet velocity : 0.26 d = 5.5 kpc (Blundell et al. 2004) Porb = 13.08 days Pprec = 162.5 days (Abell & Margon,1979) • f Ciatti et al., 1981

22. Conclusion • Some BeX sources shows similar behaviour to A0538-66. • SSS CAL83 and RXJ0513.9-6951 show a variability in a timescale 450 days and 167.94 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

23. References • Grimm et al. ,2003, Astron. Astrophys. Vol. 3 , Suppl., 257–269 • Coe et al., 2008, astro-ph 0809.2665v1 • 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

24. Thanks for your attention