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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
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