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SUMMARY:Short term variability from some ULXs: Missing in action? - Lucy H
 eil\, University of Leicester
DTSTART:20090916T161500Z
DTEND:20090916T163000Z
UID:TALK19882@talks.cam.ac.uk
CONTACT:Alexander Blustin
DESCRIPTION:We present results from a study of short term variability in 1
 9 archival observations by XMM-Newton of 16 Ultraluminous X-ray Sources (U
 LXs). Eight observations (six sources) showed intrinsic variability with p
 ower spectra in the form of either a power law or broken power law-like co
 ntinuum and in some cases quasi-periodic oscillations (QPOs) seen in previ
 ous studies of these observations. Seven observations (seven sources) yiel
 ded upper limits comparable to\, or higher than\, the values measured from
  those observations with detectable variations. These represented the seve
 n faintest sources all with f_x < 3x10^-12^ erg cm^-2^ ~ s^-1^.In contrast
  there are four observations (three sources) that gave upper limits signif
 icantly lower than both the values measured from the ULX observations with
  detectable variations\, and the values expected by comparison with lumino
 us Galactic black hole X-ray binaries (BHBs) and Active Galactic Nuclei (A
 GN). The lack of detectable variability from these bright sources\, in the
  observed frequency bandpass (10^-3^ - 1 Hz)\, is at odds with the expecta
 tions based on observations of Galactic BHBs and AGN. We present an analys
 is of these results in terms of the fluxes and X-ray luminosities from the
  observations\, and discuss solutions for suppression of variability from 
 these sources. 
LOCATION:Sackler Lecture Theatre\, IoA
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