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)
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
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
X-ray Binaries ???
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
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
• Porb : 16.65 days
• Outbursts: during optical minima
• Psuper-orbital : ~ 421 days ( Be equatorial disk forms and disperses)
A0538-66 : the archetypal BeX
MJD (+2448623.5)
Alcock et al., 2001McGowan & Charles, 2003
A0538-66 : the archetypal BeX
Data used
- MACHO [ MAssive Compact Halo Objects]o 1.27 m telescopeo Data available : from 1992 - 2000
( Alcock et al., 1996)
- OGLE [ Optical Gravitational Lensing Experiment]
( Udalsky et al,. 1997) o 1.3 m Warsaw telescope o Phase II : 1997 - 2000o Phase III : 2001 - 2009o Phase IV : First light on September 2009
MACHO + OGLE projects ~ 18 years
Resultsand findings
Long-term variations
i > 90o - α
(where α is the opening angle of the disk)
i < 90o - α
SXP : SMC X-ray Pulsar
V vs. V-R diagram of selected SMC BeX sources
Rajoelimanana, Charles & Udalski ., 2010
V vs. V-R diagram
28 out of 31 sources show this behaviour.
WHY ???
Inclination probability
P ( i < 90o- α ) = 1 – cos (90o- α )
P (i < 80o ) = 0.83Assuming α ~ 10o
31 sources 4-5 sources with i > 80o
Consistent with the number of source which get redder when fainter (3 sources) .
Outbursts amplitude vs. brightness
• The strength of the outburst increases with the brightness of the source.
Variation of outbursts amplitude
Rajoelimanana, Charles &
Udalski ., 2010
Outbursts profiles
• Transient profile.• Double peaks Misalignment Supernova kick (Brandt & Podsiadlowski, 1995)
Orbital and super-orbital period correlation
• Linear correlation coefficient of 0.73
Rajoelimanana, Charles & Udalski ., 2010
Shorter period : truncated at smaller radius
• Exposure: 1200 s
• SAAO 1.9m (Sutherland)
• Interstellar absorption distance of 1kpc
• broad line widths and asymmetries
outflow or jets
Optical spectroscopy of XMMU J115113.3-623730
J. P. Hughes, P. Slane, B. Posselt, P. Charles, A. Rajoelimanana, R. Sefako, J. Halpern, and D. Steeghs, 2010, Atel #2771
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
Summary
Thank you
