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) 1035 erg s-1 < Lx < 1039 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 : 18 - 20 Msun

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 A0538-66)

MMW / MSMC ~ 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., 2008

1 - 2 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 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 ?

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, Australiao Data available : from 1992 June - 2000 January

OGLE [ Optical Gravitational Lensing Experiment] ( Udalsky et al,. 1997)

o 1.3 m Warsaw telescope o at Las Campanas observatory, Chileo Phase II : January 1997 - ~ Dec 2000o Phase III : June 2001 - until now

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

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

Some results and findings

SXP6.85 (or XTE J0103-728)

Similar behaviour A0538-66 Peaks at P= 671 days

SXP293 (or RX J0058.2-7231)

Outbursts amplitude increases with the flux Orbital period Porb = 59 days

SXP293 (or RX J0058.2-7231)

Peak at a period Porb = 59 days

SXP756 (or AX J0049.4-7323, or RX J0049.7-7323)

Periodical outbursts near periastron passages

LMXB : Supersoft X-ray sources (SSS)

• TBB ~ 20-50 eV

• Lbol ~ 1037 - 1038 erg s-1

• SSS system : WD Sub-giant companion High accretion rate , > 10-7 Msun 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)

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 RXJ0513.9-6951 [MACHO+Ogle III]

Folded Lightcurve of CAL83 and RJX0513 with a P = 450 and 167 days , respectively

Power spectrum of CAL83 and RXJ0513.9-6951

Peaks at P = 450.24 days Peaks at P = 167.94 days

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

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

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

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