Download Study of Dynamical Cross Correlation in a Black hole source

Study of Dynamical Cross Correlation
function in a Black hole source XTE
J1550-564
K. Sriram
Osmania University
Science with LAXPC/ASTROSAT
16 December 2014
Introduction
• Emission modes cannot be wholly independent in BH/NS
sources, so by comparing their interconnection, we can learn
about the physical conditions from the main emission region:
the inner disk around a BH/NS .
• Cross-correlation function (CCF) provide us with information
about the time lags between the different components of the
emission (i.e., between the physical processes happening in
the objects).
• In general, soft and hard X-rays have different emission
locations in the accretion disk (2-5 keV, from Keplerian disk
portion & >15 keV, Compton cloud or jet), but associated
locations for optical/IR and UV emission is still not clear.
Probable wavelength emission and
Locations
Hard X-rays
Soft X-rays
Optical/IR
Motivation
• We know that BH sources show variations from milli
sec to days
• The picture of accretion disk is not clearly
understood at smaller time scales.
• Dynamical CCF provide clues of the behaviour and
unviel interdependency of various mechanisms at
smaller time scale.
CCF at longer time scale
•
GRS 1915+105
GX 339-4
H1743-322
GX339-4, RXTE/soft and INTEGRAL/ hard
CCF: Optical/IR vs X-ray at a shorter scale
Based on this, Gandhi et al. (2008) ruled out
reprocessing origin of optical photons
2-4 keV vs Optical red ,
Durant et al. 2011
Dynamic CCFs, upper left: SWIFT J1753, upper right: GX339, Bottom: Sco X-1,
Durant et al. 2011
Dynamic CCF (2-5 keV vs 13-60 keV)
of XTE J1550-564
Left: few CCFs
Correlation length :50 s,
Right: Dynamical CCF
time resolution 1s
Results
• Found correlated positive and negative lags (>20 s)
• Occasionally observed anti-correlated lags (<20 s)
• Magnitude of lags are similar to the lags observed in
CCF between optical/IR vs X-rays in other BH/NS
sources.
• Assuming accretion disk size ~106 km, 3-4 s could be
due to LTT effect and remaining could be reprocessing
or dissipation time scale, however clear picture is
lacking
Future study..
 Is the Hard X-rays and optical/IR are correlated
(Observational confirmation is required)
Because in general emitting source of IR and hard X-ray is
assumed to be Synchrotron in nature which is spanned
from IR to few hundred keVs.
 Is there any connection between the structure of CCFs and
the strength of QPO
 How the structure of CCFs varies in all the spectral
states/similar state observations
ASTROSAT: Energy domain, perfect for studying lags!!!
Thanks!!!!