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The Transient Universe: AY 250 Spring 2007
Existing Transient Surveys:High Energy II:X-ray Binaries
Geoff Bower
The Transient Universe: AY 250 Spring 2007
Discovery of X-ray Stars
Giacconi et al 1962
The Transient Universe: AY 250 Spring 2007
Aerobee Rocket
• Designed by James van Allen
• Aerojet booster• Bumblebee second stage
• Maximum altitude of 225 km
• Above 80 km for 350 seconds
• Traveled for 120 km
The Transient Universe: AY 250 Spring 2007
New Detectors
• Geiger counters
• Greater collecting area
• Anti-coincidence shields
• 50-100 times more sensitive than solar X-ray experiments
The Transient Universe: AY 250 Spring 2007
The Transient Universe: AY 250 Spring 2007
Two Discoveries
• Sco X-1• No optical counterpart
known– Eventually 13th mag Lx ~ 10^3 Lopt
• Radio counterparts expected
• X-ray background detected
• Earth origin?
The Transient Universe: AY 250 Spring 2007
Two Sources Discovered
Giacconi et al 1964
The Transient Universe: AY 250 Spring 2007
More Sources Found
Rossi 1967
•SNR•Nearby AGN•Galactic sources
The Transient Universe: AY 250 Spring 2007
Characterizing Sco X-1
• Some variability– X-ray– Optical
• 1000 x energy in X-rays than any other band
• Thermal spectrum 50 x 10^6 K
• Atomic lines in optical
• No clear understanding in early days
The Transient Universe: AY 250 Spring 2007
Pulsations & Occultations
Schreier et al 1972
~ 4 Seconds R < 10^9 cm
The Transient Universe: AY 250 Spring 2007
Binary Model
Mx ~ 1 MsunM* ~ 17 – 46 Msun
The Transient Universe: AY 250 Spring 2007
Neutron Star & Black Hole Binaries
• Periodic Fluctuations• Bursts of X-ray
emission following accretion
• Masses exceeding 3 Msun
The Transient Universe: AY 250 Spring 2007
LMXB & HMXB
• Low mass companion (< 10 Msun)
• Star overfills its Roche lobe
• Lifetime – 10^7 – 10^9 y
• High mass companion
• Stellar wind drives mass accretion
• Lifetimes < 10^7 y
Only hundreds in the entire galaxyDozens known
The Transient Universe: AY 250 Spring 2007
Galactic Distribution
O LMXB* HMXBGrimm et al 2002
The Transient Universe: AY 250 Spring 2007
Galactic Distribution
The Transient Universe: AY 250 Spring 2007
Luminosity Distributions
The Transient Universe: AY 250 Spring 2007
Super-Eddington Accretors
The Transient Universe: AY 250 Spring 2007
GRS 1915+105
• Discovered in gamma-rays but strong X-ray source
• LMXB– 15 M_sun BH– K giant companion
Fender & Belloni 2004
The Transient Universe: AY 250 Spring 2007
Variability on Wide Range of Time Scales
RXTEASM
The Transient Universe: AY 250 Spring 2007
Coupling Between Hardness, Temperature, and Radius
The Transient Universe: AY 250 Spring 2007
Well Defined X-ray States
Markward et al 1999
Hard
Soft
Cool, distant disk Hot, close disk
The Transient Universe: AY 250 Spring 2007
Photon Index
Tem
pera
ture
The Transient Universe: AY 250 Spring 2007
Superluminal Motion
The Transient Universe: AY 250 Spring 2007
Coupled Radio/X-ray Activity
The Transient Universe: AY 250 Spring 2007
The Transient Universe: AY 250 Spring 2007
Comparison to AGN
• Tau ~ M^-1/2• Jet Quenching at 1 -
10% L_EDD
Triangles: XRBSquares: AGN
The Transient Universe: AY 250 Spring 2007
Chandra Observations of the Galactic Center
Muno et al 2002
1 Msec2300 sources< 10 multi-wavelength counterparts
The Transient Universe: AY 250 Spring 2007
Foreground Separation
The Transient Universe: AY 250 Spring 2007
Galactic X-ray Sources
The Transient Universe: AY 250 Spring 2007
GC Transients
The Transient Universe: AY 250 Spring 2007
Overabundance of Transients in Central Parsec
Radius Transients Stellar Mass Transient Rate
1 pc 4 2 X 10^6 M_sun
20
20 pc 3 3 x 10^7 1
The Transient Universe: AY 250 Spring 2007
Two Explanations for Transient Overdensity
• LMXBs
• Dynamical friction drives compact objects to GC
• Three-body interactions produces LMXB
• HMXB
Ghez et al 2006
The Transient Universe: AY 250 Spring 2007
One LMXB Known
X-ray eclipsesPorquet et al 2005
Double-lobe radio sourceBower et al 2005