The talks are in the same order as the Program Schedule.
Kallman, Tim - HETG Observations of AC211 in the Globular Cluster M15
Isobe, Naoki - Spectral transition of an ultra-luminous X-ray source, NGC 2403 Source 3
Schulz, Norbert S. - Warm Absorbers in Galactic X-ray Binaries
LI JI (MIT Kavli Institute for Astrophysics & Space Research) , N.S. Schulz (MKI), M. Nowak(MKI) & H.L. Marshall(MKI)
We present an analysis of six high-resolution Chandra grating observations of the X-ray binary pulsar Her X-1. With a total exposure of 170 ks, the observations are separated by years and cover three combinations of orbital and super-orbital phases. Our goal is to determine the properties of the photoionized emission and its dependence on phase-dependent variations of the continuum. We find that the continua can be described by a partial covering model which is consistent with the high energy spectra observed with RXTE. Moreover, an additional thermal blackbody component is required to fit the soft band below 12 Å( 1 keV). Most of the variability is caused by high absorption columns varying from (1 - 3) x 1023 cm-2. Most spectra show strong line emission stemming from a photoionized accretion disk corona. We model the line emission with generic thermal plasma models as well as with the photoionization code XSTAR and determine changes of the ionization balance with orbital and superorbital phases. Most spectra also show strong and variable fluorescence line emission from near neutral Fe,likely associated with the cooler, outer portions of the disk.
Tim Kallman (NASA/GSFC, Laboratory for X-ray Astrophysics) , L. Angelini, N. E. White (NASA/GSFC), J. Sepinsky (NWU)
We report on a 60 ksec observation of the low mass X-ray binary AC211/4U2127+119 in the Globular CLuster M15 using the Chandra HETG. The presence of the confusing source 3 arc-seconds away necessitates careful observation planning and analysis to disentangle the two spectra. The observation spans approximately one binary orbit, and the HETG spectrum shows emission lines from highly ionized Si, Mg, Ne, and O,and also features which correspond to the K lines of iron. The ratios of the helium-like lines from Mg and Si provide a lower limit on the density or the UV radiation field in the line emitting region. The relative strengths of the H- and He-like lines are consistent with photoionization equilibrium, with a narrow range of allowed ionization parameters. This provides an upper limit on the distance of the line-emitting gas from the source of X-ray continuum. The line emission is crudely consistent with that expected from an accretion disk corona, although there are important differences between this source and other likely ADC sources. One example is the strength of the iron line. We discuss these differences, and interpret them in the context of other information about this source: its orbital parameters and the nature of the companion star.
Michael McCollough (SAO) , Lynne Valencic (NASA/GSFC)
Cygnus X-3 is a well know microquasar which shows state changes, strong radio emission, hard X-ray-radio correlations, and relativistic jets. The exact nature of compact object associated with this system is still uncertain. In this presentation are shown new results which will further illustrate the complexity and uniqueness of this system. In 2003 extended X-ray emission was discovered associated with Cygnus X-3 using Chandra (Heindl et al. 2003). One of the most likely interpretations of this feature was that of a jet impact region. In 2006 a longer Chandra observation during which Cygnus X-3 was in a brighter X-ray state has revealed a much better look at this emission. We will show that even though this feature is 16" away from Cygnus X-3 it demonstrates remarkable time correlated activity associated with Cygnus X-3. The behavior of this emission and the possible nature of this feature will be discussed in this presentation.
Naoki Isobe (RIKEN) , Kazuo Makishima (RIKEN/University of Tokyo), Atsushi Senda (RIKEN), Madoka Kawaharada (RIKEN), Hiromitsu Takahashi (Hiroshima University), Tsunehumi Mizuno (Hiroshima University), Ryohei Miyawaki (University of Tokyo), Tessei Yoshida (Tokyo University of Science), Richard Mushotzky (NASA/GSFC)
We report the study of the spectral variation over 5 years, of an ultra-luminous X-ray source NGC 2403 Source 3, which is located in the arm region of a normal spiral galaxy NGC 2403. We performed a Suzaku observation of NGC 2403 during the Science working group phase on 2006 March 16. All the available archival Chandra and Newton data are also analysed. Except for one Chandra observation, the X-ray spectra of NGC 2403 source 3 are successfully described with a multi-color disk (MCD) model. The innermost disk temperature and bolometric luminosity of the source is found to be rather stable, Tin = 1.04 - 1.18 keV and
ergs/s, respectively. The innermost disk radius is determined to be 96 - 130 km, indicating that the mass of the source is about 10 - 15 times the solar masses. As a result, the source is inferred to be shining near the Eddington limit. In the remaining Chandra observation, conducted in 2004 November, we have discovered that the source showed a transition to a power-law (PL) spectrum with a photon index of Gamma = 
. In this observation, the lumineosity of the source is lower by abou 10 /
Norbert S. Schulz (MIT Kavli Institute for Astrophysics & Space Research)
X-ray binaries, specifically the ones labeled as microquasars, are considered to be the small-scale Galactic counterparts of active galactic nuclei (AGN). Physically they are distinctly different in that they are stellar binaries in which a compact object, in most cases a stellar black hole, accretes matter from a stellar companion. These objects exhibit relativistic jets and outflow patterns reminicent of their of their extragalactic cousins. While their radio and X-ray emission indeed provide many signatures that resemble the ones we ususally see in AGNs, they provide an upclose view of the various accretion phenomena common in these objects. This presentation investigates warm absorbers. Until quite recently, warm absorbers were mostly discussed in the context of AGN, but recent observations with high resolution X-ray spectrometers provided a manifold of different warm absorber activity in X-ray binaries, not all of them are considered to actually be microquasars. This presentation reviews recent results involving microquasars (i.e. GROJ1655-40, Cir X-1) and normal X-ray binaries (i.e. 4U 1624-49, EXO 0748-676) with a wide range ionization parameters and column densities. Only recently have we begun to understand and identify warm absorber features which provide novel clues to understand the accretion process onto compact objects.