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

Existing Transient Surveys:High Energy II:X-ray Binaries

Geoff Bower

Discovery of X-ray Stars

Giacconi et al 1962

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

New Detectors

• Geiger counters

• Greater collecting area

• Anti-coincidence shields

• 50-100 times more sensitive than solar X-ray experiments

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?

Two Sources Discovered

Giacconi et al 1964

More Sources Found

Rossi 1967

•SNR•Nearby AGN•Galactic sources

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

Pulsations & Occultations

Schreier et al 1972

~ 4 Seconds R < 10^9 cm

Binary Model

Mx ~ 1 MsunM* ~ 17 – 46 Msun

Neutron Star & Black Hole Binaries

• Periodic Fluctuations• Bursts of X-ray

emission following accretion

• Masses exceeding 3 Msun

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

Galactic Distribution

O LMXB* HMXBGrimm et al 2002

Galactic Distribution

Luminosity Distributions

Super-Eddington Accretors

GRS 1915+105

• Discovered in gamma-rays but strong X-ray source

• LMXB– 15 M_sun BH– K giant companion

Fender & Belloni 2004

Variability on Wide Range of Time Scales

RXTEASM

Coupling Between Hardness, Temperature, and Radius

Well Defined X-ray States

Markward et al 1999

Cool, distant disk Hot, close disk

Photon Index

Superluminal Motion

Coupled Radio/X-ray Activity

Comparison to AGN

• Tau ~ M^-1/2• Jet Quenching at 1 -

10% L_EDD

Triangles: XRBSquares: AGN

Chandra Observations of the Galactic Center

Muno et al 2002

1 Msec2300 sources< 10 multi-wavelength counterparts

Foreground Separation

Galactic X-ray Sources

GC Transients

Overabundance of Transients in Central Parsec

Radius Transients Stellar Mass Transient Rate

1 pc 4 2 X 10^6 M_sun

20 pc 3 3 x 10^7 1

Two Explanations for Transient Overdensity

• LMXBs

• Dynamical friction drives compact objects to GC

• Three-body interactions produces LMXB

• HMXB

Ghez et al 2006

One LMXB Known

X-ray eclipsesPorquet et al 2005

Double-lobe radio sourceBower et al 2005

The Transient Universe: AY 250 Spring 2007 Existing Transient Surveys: High Energy II: X-ray Binaries Geoff Bower.

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