Challenges of high-energy observations : Carinae as seen by the. European -ray
observatory. Jean-Christophe Leyder. Institut d'Astrophysique et de ...
Challenges of high-energy observations : ! Carinae as seen by the European "-ray observatory Jean-Christophe Leyder Institut d’Astrophysique et de Géophysique de Liège Roland Walter (ISDC) & Gregor Rauw (IAGL) ESO Vitacura Santiago, July 2008
Outline
• X-ray and gamma-ray satellites • High-energy emission from colliding-wind binaries
• INTEGRAL observations of Eta Carinae • Future prospects
Multi-wavelength observations
Focusing photons in X-rays
Focusing photons in X-rays
Imaging in gamma-rays : INTEGRAL
“Coded masks”
Imaging in gamma-rays : INTEGRAL
Coded mask
Shadowgram
Image
Hard X-ray and #-ray emission from colliding-wind binaries
• Colliding-wind binaries
! Hydrodynamical shock ! Acceleration of particles ! Relativistic electrons
• Early-type stars
! Huge UV radiation field
• Inverse Compton scattering
! Hard X-rays and soft gamma-rays Bell 1978, Pittard & Dougherty 2006
Eta Carinae
• Known for its eruption in 1843 • Mass-loss rate of 10 − 10 M • Period of 5.5 years in!: −3
−4
(Viotti 1995)
" /year
optical observations (Damineli et al. 2000) infrared observations (Whitelock et al. 2004) X-ray observations (Corcoran 2005) NASA, ESA, UCB, STScI/AURA 2007
Eta Carinae
• Known for its eruption in 1843 • Mass-loss rate of 10 − 10 M • Period of 5.5 years in!: −3
−4
(Viotti 1995)
" /year
optical observations (Damineli et al. 2000) infrared observations (Whitelock et al. 2004) X-ray observations (Corcoran 2005) NASA, ESA, UCB, STScI/AURA 2007
Eta Carinae
• Known for its eruption in 1843 • Mass-loss rate of 10 − 10 M • Period of 5.5 years in!: −3
−4
(Viotti 1995)
" /year
optical observations (Damineli et al. 2000) infrared observations (Whitelock et al. 2004) X-ray observations (Corcoran 2005)
Eta Carinae J. M. Pittard and M. F. Corcoran: In hot pursuit of the hidden companion of η Carinae
• Known for its eruption in 1843 • Mass-loss rate of 10 − 10 M • Period of 5.5 years in!: 30
PCU2 L1 net counts Colliding wind lightcurve (Pittard et al. 1998)
(Viotti 1995)
Net PCU2 L1 counts s
-1
25
−3
−4
" /year
20
15
10
5
optical observations (Damineli et al. 2000) infrared observations (Whitelock et al. 2004) X-ray observations (Corcoran 2005) 1.0
1.5
Orbital Phase
2.0
2.5
Pittard & Corcoran 2005
ig. 1. Lightcurve of η Car observed with the RXTE satellite and phased to the 5.5 yr orbital period. Plotted are counts dete layer 1 of the second proportional counter unit (PCU2) and a predicted lightcurve (Pittard et al. 1998) from a num odel of the wind-wind collision. The two agree well, particularly the duration of the minimum. The rise from minimum i good agreement, but this is thought to be due to the limitations of modelling the wind collision in 2D. The rapid chan
Eta Carinae as a colliding-wind binary
• Binary system made of : a Luminous Blue Variable a less extreme (O or WR) star (Iping et al. 2005)
• High eccentricity (0.9) • X-ray spectrum ! Colliding-wind binary (Corcoran et al. 2001)
(Corcoran 2005)
BeppoSAX observations 4 observations with PDS (Viotti et al. 2004) :
• High-energy excess (13-20 keV) at $ = 0.83, 1.37, 1.46
• No excess at $ = 1.05 ... but this needs confirmation...
• High-energy tail up to 50 keV (June 2000)
INTEGRAL observations : image
• 1131 pointings, i.e. 3.3 Ms
! Effective exposure time of 1.1 Ms
• 3 sources in the PDS field
INTEGRAL observations : image
•
Eta Carinae (22-100 keV) : significance = 7.3 luminosity = 7E33 erg/s
• •
Anomalous X-ray Pulsar 1E 1048.1-5937 IGR J10447-6027
• 1131 pointings, i.e. 3.3 Ms
! Effective exposure time of 1.1NACO/VLT Ms
• 3 sources in the PDS field
Leyder, Walter & Rauw 2008
INTEGRAL observations : spectrum
• Up to 100 keV • wabs*mekal (kT = 5.1 keV, NH = 4.3E22) • powerlaw ! photon index of 1 ± 0.4
BeppoSAX
INTEGRAL
10!5
10!4
• Up to 100 keV • wabs*mekal (kT = 5.1 keV, NH = 4.3E22) • powerlaw ! photon index of 1 ± 0.4 • •
10!6
keV/cm2 s keV
10!3
0.01
INTEGRAL observations : spectrum
2
wabs*mekal (kT = 5.1 keV, NH = 4.3E22) powerlaw ! photon index gamma of 1 ± 0.4 5
10
20
channel energy (keV)
50
100
Leyder, Walter & Rauw 2008
INTEGRAL observations : mechanism
• High-energy non-thermal emission from a colliding-wind binary
• Inverse Compton scattering of UV or optical
photons by high-energy electrons accelerated in the collision zone (Benaglia & Romero 2003)
• Total power in stellar1 wind interactions L=
2 ˙ ΘM v
2 37 L1 + L2 ! 10 erg/s
(Pittard & Stevens 2002)
INTEGRAL observations : variability?
• 3 major periods of observations!: $ = 1.99-2.01; 122 ks; significance = --$ = 2.16-2.19; 717 ks; significance = 6.2 $ = 2.35-2.37; 180 ks; significance = 3.3
• X-ray lightcurve
INTEGRAL observations : variability?
J. M. Pittard and M. F. Corcoran: In hot pursuit of the hidden companion of η Carinae 30
PCU2 L1 net counts Colliding wind lightcurve (Pittard et al. 1998)
Net PCU2 L1 counts s
-1
25
• 3 major periods of observations!: 20
15
$ = 1.99-2.01; 122 ks; significance = ---
10
$ = 2.16-2.19; 717 ks; significance = 6.2
5
•
$ = 2.35-2.37; 180 ks; significance = 3.3 1.0
X-ray lightcurve
1.5 Orbital Phase
2.0
2.5
Pittard & Corcoran 2005
ig. 1. Lightcurve of η Car observed with the RXTE satellite and phased to the 5.5 yr orbital period. Plotted are counts dete layer 1 of the second proportional counter unit (PCU2) and a predicted lightcurve (Pittard et al. 1998) from a num odel of the wind-wind collision. The two agree well, particularly the duration of the minimum. The rise from minimum i good agreement, but this is thought to be due to the limitations of modelling the wind collision in 2D. The rapid chan osition angle of the stars through periastron passage skews the shock cone which causes the line of sight in fully 3D mod main in the denser wind of the primary until later phases, increasing the absorption at these times (Pittard 2000).
Colliding-wind binary ! Increase in column density ! Decrease in plasma emission measure
Future prospects
• Systematic search for : Wolf-Rayet stars non-thermal radio emitting early-type stars O-type stars (magnitude V < 8)
• Variability of Eta Car in gamma-rays? 1Ms of observations during next periastron
