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Long-term Properties of Be/X-ray Pulsars in the SMC

This study investigates the long-term properties of Be/X-ray pulsars in the Small Magellanic Cloud (SMC). The research examines X-ray binaries, specifically High Mass X-ray Binaries (HMXBs) and Supergiant X-ray Binaries (SgrXBs), with a focus on Be/X-ray binaries (BeX). The analysis includes results on outburst amplitude variations, orbital and super-orbital period correlations, and color-magnitude diagrams of selected SMC BeX sources. Optical spectroscopy of XMMU J115113.3-623730 is discussed, as presented in Atel #2771, along with insights into the degenerate primary objects and the multi-wavelength nature of these systems. The iconic BeX source A0538-66 is compared in terms of orbital and super-orbital periods, outburst characteristics, and the presence of a misalignment effect. Overall, the study provides a comprehensive overview of the observational findings and trends observed in Be/X-ray pulsars within the SMC.

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Long-term Properties of Be/X-ray Pulsars in the SMC

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  1. Long-term properties of Be/X-ray pulsars in the SMC Andry RAJOELIMANANA 1 , 2‏ Supervisor : Prof Phil CHARLES 1 , 2 Co-supervisor : Prof Brian Warner 1 1 University of Cape Town (UCT), 2 South African Astronomical Observatory (SAAO)

  2. Outline • Introduction and Background • X-ray binary • High Mass X-ray Binaries (HMXBs) • Supergiant X-ray Binaries (SgrXBs) • Be/X-ray binary (BeX) • A0538-66 (For Comparison) • Some results • Variation of outbursts amplitude. • Orbital and super-orbital period correlation. • Colour magnitude diagram of selected SMC BeX. • Misalignment effect • Optical spectroscopy of XMMU J115113.3-623730 (ATel #2771) • Summary

  3. X-ray Binaries ??? • Degenerate primary ( a NS, or a BH) • 1035 erg s-1 < Lx < 1039 erg s-1 • LMXBs or HMXBs. • Multi-wavelength objects: • Gamma-ray : Inverse-Compton scattering • X-ray : compact objects : NS or BH • Optical : Primary star, and accretion disc • Radio : Jets, synchrotron radiation

  4. Supergiant X-ray binaries (SGXBs) • Early-type Supergiants + Compact object( NS or BH) • Period ~ 3-15 d ‏ • Circular orbits • Persistent X-ray sources (Lx~1036 erg.s-1) • Accretion from strong radiative stellar wind

  5. Be/X-ray binaries (BeX) • Be Star + X-ray pulsar • Transient X-ray sources (Lx~1037 erg.s-1) • Wide and eccentric orbit (0.1<e<0.9) • Accretion from the Be equatorial disc

  6. A0538-66 : the archetypal BeX • Porb : 16.65 days • Outbursts: during optical minima • Psuper-orbital : ~ 421 days ( Be equatorial disk forms and disperses) Alcock et al., 2001 McGowan & Charles, 2003 MJD (+2448623.5)

  7. A0538-66 : the archetypal BeX

  8. Data used - MACHO[ MAssiveCompact Halo Objects] • 1.27 m telescope • Data available : from 1992 - 2000 • ( Alcock et al., 1996) • ‏ - OGLE [ Optical Gravitational LensingExperiment] ( Udalsky et al,. 1997) • 1.3 m Warsaw telescope • Phase II : 1997 - 2000 • Phase III : 2001 - 2009 • Phase IV : First light on September 2009 MACHO + OGLE projects ~ 18 years

  9. Results and findings

  10. Long-term variations i > 90o - α (where α is the opening angle of the disk) i < 90o - α SXP : SMC X-ray Pulsar

  11. V vs. V-R diagram of selected SMC BeX sources Rajoelimanana, Charles & Udalski ., 2010

  12. V vs. V-R diagram 28 out of 31 sources show this behaviour. WHY ???

  13. Inclination probability P ( i < 90o- α ) = 1 – cos (90o- α ) Assumingα ~ 10o P (i < 80o ) = 0.83 31 sources  4-5 sources with i > 80o Consistent with the number of source which get redder when fainter (3 sources) .

  14. Outbursts amplitude vs. brightness • The strength of the outburst increases with the brightness of the source.

  15. Variation of outbursts amplitude Rajoelimanana, Charles & Udalski ., 2010

  16. Outbursts profiles • Transient profile. • Double peaks Misalignment Supernova kick • (Brandt & Podsiadlowski, 1995)

  17. Orbital and super-orbital period correlation • Linear correlation coefficient of 0.73 Shorter period : truncated at smaller radius Rajoelimanana, Charles & Udalski ., 2010

  18. Optical spectroscopy of XMMU J115113.3-623730 • Exposure: 1200 s • SAAO 1.9m (Sutherland) • Interstellar absorption  distance of 1kpc • broad line widths and asymmetries •  outflow or jets J. P. Hughes, P. Slane, B. Posselt, P. Charles, A. Rajoelimanana, R. Sefako, J. Halpern, and D. Steeghs, 2010, Atel #2771

  19. Summary • 19 super-orbital periods • compiled and updated their orbital periods (36 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, from asymmetric • supernova kick) • Optical spectroscopy of XMMU J115113.3-623730  V Sagittae stars

  20. Thank you

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