Julia C. Lee

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We present detailed evidence for a warm absorber in the Seyfert 1 galaxy MCG–6-30-15 and refute earlier claims for relativistic O line emission. The HETG spectra show numerous absorption lines from a wide range 2 − 1snp resonance line series to n = 9 are clearly detected at rest in the AGN frame. We attribute previous reports of an apparently highly(More)
We present an analysis of the long Rossi X-ray Timing Explorer (RXTE) observation of the Seyfert 1 galaxy MCG?6-30-15, taken in July 1997. We have earlier used the data to place constraints for the first time on the iron abundance-reflection fraction relationship, and now expand the analysis to investigate in detail the spectral X-ray variability of the(More)
We present X-ray, infrared, optical and radio observations of four previously unidentified Galactic plane X-ray sources, AX J163252–4746, AX J184738–0156, AX J144701–5919 and AX J144547–5931. Detection of each source with the Chandra X-ray Observatory has provided sub-arcsecond localizations, which we use to identify bright infrared counterparts to all four(More)
We present analyses of a 50 ks observation of the supergiant X-ray binary system Cygnus X-1/HDE 226868 taken with the Chandra High Energy Transmission Grating Spectrometer (HETGS). Cyg X-1 was in its spectrally hard state and the observation was performed during superior conjunction of the black hole, allowing for the spectroscopic analysis of the accreted(More)
We describe a methodology for transforming sets of database transactions into sets of conflict-free transactions which can be executed independently and in parallel. The method identifies conflicting tuples and uses buffers in high-speed memory to hold those tuples. The separate transactions are then modified to operate on both the database and the relevant(More)
We present X-ray dust scattering halo results based on our 76 ks Chandra ACIS-S/HETGS observation of the LMXB dipping source 4U 1624-490. Through analysis of the halo light curves with 2-6 keV spectra over the persistent and dipping periods, we estimate a geometric distance of ∼15 kpc to 4U 1624-490. We also fit halo radial profiles with different ISM dust(More)
We present detailed evidence for a warm absorber in the Seyfert 1 galaxy MCG–6-30-15 and dispute earlier claims for relativistic O line emission. The HETG spectra show numerous narrow, unresolved (FWHM ∼ < 200 km s −1) absorption lines from a wide range of ionization states of N edge and 1s 2 − 1snp resonance line series to n = 9 are clearly detected at(More)
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