The Ultra-luminous X-Ray Sources Near the Center of M82

NTHU

10/18/2007

Yi-Jung Yang

Outline

Nature of Ultraluminous X-ray Sources (ULXs)

Suggested models of ULXs

X-ray sources at central region of M82

X-ray sources and star clusters correlation

Lightcurves of target transient source

Spectral analysis

Some basic of X-Ray Binaries

Summary

Ultra-Luminous X-ray Sources (ULXs)

off-nuclear X-ray sources (not at the center)

with isotropic luminosities much higher than the Eddington limit for a solar mass black hole (Lx ~ 1.381038 erg/s)

Typical X-ray luminosities of ULXs are in between 1039 erg/s and 1041 erg/s (AGN > 1041 erg/s)

Many ULXs show strong variability suggesting that they are accreting compact objects!

Thin super-Eddington, radiation pressure-dominated accretion disks orbiting the stellar-mass black hole binaries

Stellar-mass black hole binaries with anisotropic X-ray emission (mechanical beaming)

Micro-blazars observed along the direction of their relativistically beamed jet

Young supernova remnants in a high-density medium or hypernova remnants.

Background AGN or foreground stars

Intermediate mass black hole binaries (IMBHs)

Models to explain ULXs

X-ray Image of the Central Region of the Starburst Galaxy M82 (NGC 3034, Cigar Galaxy)

Galactic dynamical center

M82 X-1Transient Source (on) Transient Source (off)

M82 X-1 is so far the best IMBH candidate, which is not an AGN and has a luminosity around ~1041 erg/s.

Possible background AGN

Supernovae Remnant

Ultraluminous X-ray Sources in M82

1999-09-20 ObsID 361 2002-06-18 ObsID 2933

Chandra 0.3-7 keV images of the central 45”45” region of M82

radius of circle ~ 1 arcsec ~17 pc

has luminosity ~ 1041 erg/sec

not at the center of the galaxy => Not an AGN

has a period of 62 days

very close to a young star cluster MGG-11

has quasi-periodic oscillation (QPO) around 55 mHz

has a mass > 500 Msolar

Best Candidate of IMBH – M82 X-1

X-ray Sources and Star Clusters Correlation

Chandra Observation Log

Short Term Light-curve of the Recurrent X-Ray Transient

Lightcurves extracted from Chandra observations taken from 1999 to 2005. The source was first appeared in 1999 October. It turned off in 2000 January, but later reappeared and has been

active since then.

Long Term Light-Curve of the Transient source

Long-term X-ray lightcurve of the ultraluminous X-ray transient.

The luminosities are determined by spectral fits.

Energy Spectrum of the Transient SourceBest fitted with a Power-law model, power-law index = 1.3 ~ 1.7

Lx = (8 ~13)1039 erg/s, NH 3 1022 cm-2

Chandra ACIS-S ObsID 5644 2005-08-1775.1 ks exposure time

Energy Spectrum of the possible Background AGNFitted with a Power-law model, power-law index = 0.6 ~ 2.2

Lx = (3 ~17)1039 erg/s, NH (12~21)1022 cm-2

Energy Spectrum of the possible Background AGNFitted with an ionized absorber + power law model,

power-law index = 2, NH = 9 1023 cm-2

Energy Spectrum of the Supernovae RemnantFitted with a Power-law model, power-law index = 2.7 ~ 4.5

Lx = (2 ~12)1039 erg/s, NH (2~4)1022 cm-2

Energy Spectrum of the Supernovae RemnantFitted with an absorbed Raymond-Smith + Power-law model,

power-law index = 2.01 , NH = 2.9 1022 cm-2

Power-Law Spectral Model Fit for J095551.0 (the Transient Source)

Power-Law Spectral Model Fit for J095551.2 (possible background AGN)

Power-Law Spectral Model Fit for J095550.6 (Supernovae Remnant)

HMXB• Donor star is usually young and massive• Accretor was short-lived and massive star• Prefer star-forming region & spiral arms• Period ~ days• Ages: Young ~ 107~108 years

LMXB• Donor star is usually white dwarf• Accretor might be lower mass star, slowly evolved to NS/BH• Prefer galactic bulges & globular clusters• Period ~ hours• Ages: Old > 109 years

M74

Antennae (NGC 4038/4039)

Transient behavior & hard X-ray spectrum – rule out the supernovae remnants and background AGNHigh X-ray isotropic luminosity (~1040 erg/s) – black hole accretorNo short-term variability (hours) – unlikely to be relativistically beaming jetNo disk emission & hard x-ray spectrum – unlikely to be anisotropic emission (beaming)Within the super star clusters region and associated with a young star cluster – ideal birth place to produce Intermediate-mass black hole

Summary