Transcript The ultra-luminous x-ray sources near center of M82

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 ~ 1.381038 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!
Models to explain ULXs
 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)
X-ray Image of the Central Region of the
Starburst Galaxy M82 (NGC 3034, Cigar Galaxy)
Transient Source (on)
M82 X-1
Transient Source (off)
Supernovae Remnant
Galactic dynamical center
Possible background AGN
M82 X-1 is so far the best IMBH candidate, which is not an
AGN and has a luminosity around ~1041 erg/s.
Ultraluminous X-ray Sources in M82
 Chandra 0.3-7 keV images of the central 45”45” region of M82
1999-09-20 ObsID 361
radius of circle ~ 1 arcsec ~17 pc
2002-06-18 ObsID 2933
Best Candidate of IMBH – M82 X-1
 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
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 Source
Best 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
2005-08-17
75.1 ks exposure time
Energy Spectrum of the possible Background AGN
Fitted 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 AGN
Fitted with an ionized absorber + power law model,
power-law index  = 2, NH = 9 1023 cm-2
Energy Spectrum of the Supernovae Remnant
Fitted 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 Remnant
Fitted 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)
Summary
Transient behavior & hard X-ray spectrum – rule out
the supernovae remnants and background AGN
High X-ray isotropic luminosity (~1040 erg/s) – black
hole accretor
No short-term variability (hours) – unlikely to be
relativistically beaming jet
No 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