Image of Alice in Wonderland at the Mad Hatter's tea party You are cordially invited to afternoon tea and biscuits wine and chocolate

Astronomy Tea Talks at Caltech

Mondays, Hameetman auditorium (Cahill)
Tea:  4.00pm
Talk: 4.15pm

Organized by:

2008 - 2009 season:
11 June 2009
Poshak Gandhi (RIKEN, Japan)

New constraints on accretion from rapid optical and X-ray timing observations of black hole binaries

Rapid, continuous flickering of light is a characteristic feature of
compact, accreting sources, mostly seen in X-rays. Now, in one of the
fastest coordinated timing studies of black hole X-ray binaries to date,
we have discovered correlated optical and X-ray variability in two
Galactic sources: GX 339-4 and SWIFT J1753.5-0127. The observations were
carried out simultaneously with VLT/Ultracam and RXTE, and the data reveal
intriguing patterns down to the shortest time resolution available (~50
ms). Reprocessing can be ruled out as the origin of the aperiodic optical
power. Instead, the variability may be driven by synchrotron emission from
the inner accretion flow regions, with interactions between the disk, jet
and corona resulting in the complex correlation patterns.

I also show that both the optical and X-ray lightcurves are intrinsically
'non-linear', in the sense that the absolute variability r.m.s. amplitude
linearly increases with flux. The implication is that variability at both
wavelengths is not due to local fluctuations alone (i.e. additive shot
flares can be ruled out), but rather arises as a result of coupling of
perturbations over a wide range of radii and timescales. These
observations provide key constraints for modeling not only accretion, but
also hot plasma processes in the Sun.

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Last modified on 20th Jul 2011 by Scott Schnee.  

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