Aarnio, Alicia - Angular Momentum Loss Considerations in Large Scale T Tauri Flares
Bressert, Eli - Smoothing Algorithm that Preserves Structures of Astronomical X-ray Data
den Herder, Jan-Willem - EDGE: Explorer of Diffuse emission and Gamma-ray burst Explosions
den Herder, Jan-Willem - EDGE: Explorer of Diffuse emission and Gamma-ray burst Explosions
Huang, Hsiu-Hui - Study of HST counterparts to Chandra X-ray sources in the Globular Cluster M71
Smith, Randall - An X-ray Calorimeter on the Spectrum-X Gamma Mission
Xiang, Jinge - Probing the 4U 1624-490 Ionized Gas and Dust distribution along the LOS
Alicia Aarnio (Vanderbilt University) , Keivan Stassun (Vanderbilt University)
The Chandra Orion Ultradeep Project was able to observe a number of T Tauri stars during highly energetic X-ray flare events. Favata et al. (2005) then applied a uniform cooling loop model effective in modeling solar magnetic field loops to derive loop arc lengths on the order of 100 stellar radii in the most extreme cases. In the context of pre-main sequence evolution, are we to interpret these loops as structures connecting star to disk or, using a solar analogue, do they represent extreme "coronal mass ejections" (CMEs)? We have created Monte Carlo models of the spectral energy distributions of the stars with the largest flaring loops and found that the majority of the sample appears to lack circumstellar disk material. This surprising result is the impetus for detailed analysis of the mass and angular momentum lost via CME events of this magnitude. We present estimates of angular momentum loss via large scale flare events and discuss the implications of this work for stellar angular momentum evolution of young low-mass stars.
Eli Bressert (Chandra X-ray Center) , Kim Kowal Arcand (Chandra X-ray Center), Peter Edmonds (Chandra X-ray Center)
We have processed numerous X-ray data sets using several well-known algorithms such as Gaussian and adaptive smoothing for public related image releases. These algorithms are used to smooth images and retain the overall structure of observed objects. Recently, a new PDE algorithm and program, provided by Dr. David Tschumperle and referred to as GREYCstoration, has been tested and is in the progress of being implemented into the Chandra EPO imaging group. Results of GREYCstoration will be presented and compared to the currently used methods for X-ray images. What demarcates Tschumperle's algorithm from the current algorithms used by the EPO imaging group is its ability to preserve the main structures of an image strongly, while optimizing the image for visual analysis. In addition to smoothing images, GREYCstoration can be used to erase artifacts accumulated during observation and mosaicking stages. GREYCstoration produces results that are comparable and in some cases more preferable than the current smoothing algorithms. From our early stages of testing, the results of the new algorithm will provide insight on the algorithm's capabilities and its potential uses for future applications and images.
Patrick Broos (Penn State University) , Leisa Townsley (Penn State University)
Fields with thousands of X-ray point sources pose significant data analysis challenges to the Chandra/ACIS observer, ranging from source detection to spectral modeling. We describe three innovations we are exploring as part of the ACIS Team's on-going development of the ACIS Extract (AE) analysis package, which has been publicly available since 2002. (1) Point source detection in crowded fields is difficult. We describe a procedure that first proposes sources by identifying peaks in a simple Richardson-Lucy restoration of ACIS image data, and then carefully computes a confidence level for each candidate source using the AE machinery. (2) Accurate local background estimation is critical for effective source detection and for spectral analysis of weak sources. We describe a model-based approach to background estimation, now available in AE, that addresses the crowded field problem. (3) Perhaps the best approach for modeling the low-count spectra produced by the majority of ACIS sources is simultaneous fitting of the raw (not grouped) source and background spectra using the C-statistic. However, the background model employed by XSPEC (when the C-statistic is selected and a background spectrum is supplied) is known to produce biased results. We describe a simple alternative background model that seems to perform well.
Jan-Willem den Herder (SRON) , L. Piro (INAF-Rome), T. Ohashi (Tokyo Metropolitan University), C. Kouveliotou (MSFC) on behalf of the EDGE consortium
How structures on various scales formed and evolved from the early Universe up to present time is a fundamental question of astrophysical cosmology. EDGE will trace the cosmic history of the baryons from the early generations of massive star by Gamma-Ray Burst (GRB) explosions, through the period of cluster formation, down to very low redshifts, when between a third and one half of the baryons are expected to reside in cosmic filaments undergoing gravitational collapse by dark matter (Warm Hot Intragalactic Medium: WHIM). In addition EDGE, with its unprecedented observational capabilities, will provide key results on several other topics including: the study of feedback mechanisms into the Interstellar Medium (Supernova Remnants, galaxy/Active Galactic Nuclei outflows), constraints on the Dark Matter and Dark Energy content of the Universe (through clusters and GRBs), equation of state of the densest matter (neutron stars), GRB physics, upper limits on light dark matter particles, accurate measurement of the geometry of space-time by measuring X-ray afterglows of black hole mergers detected through gravitational waves, Active Galactic Nuclei and stellar population surveys, and Solar System physics. The science is feasible with a medium class mission using existing technology combined with innovative instrumental and observational capabilities on a single satellite by: a) observing with fast reaction Gamma-Ray Bursts with a high spectral resolution (R 500). This enables the study of their (star-forming) environment from the Dark to the local Universe and the use of GRB as back light of large scale cosmological structures b) Observing and surveying extended sources (clusters, WHIM) with high sensitivity using two wide field of view X-ray telescopes (one with a high angular resolution and the other with a high spectral resolution). The mission concept includes four main instruments: a Wide-field Spectrometer with excellent energy resolution (3 eV, 1 eV goal), a Wide-Field Imager with high angular resolution (15”) constant over the full 1.4 degree field of view, and a Wide Field Monitor with a FOV of ¼ of the sky, which will trigger the fast repointing. Extension of its energy response up to 1 MeV will be achieved with a GRB detector with no imaging capability. This mission is proposed to ESA as part of the Cosmic Vision call. We will describe the science drivers and the payload of this mission.
Jan-Willem den Herder (SRON) , L. Piro (INAF-Rome), T. Ohashi (Tokyo Metropolitan University), C. Kouveliotou (MSFC) on behalf of the EDGE consortium
How structures on various scales formed and evolved from the early Universe up to present time is a fundamental question of astrophysical cosmology. EDGE will trace the cosmic history of the baryons from the early generations of massive star by Gamma-Ray Burst (GRB) explosions, through the period of cluster formation, down to very low redshifts, when between a third and one half of the baryons are expected to reside in cosmic filaments undergoing gravitational collapse by dark matter (Warm Hot Intragalactic Medium: WHIM). In addition EDGE, with its unprecedented observational capabilities, will provide key results on several other topics including: the study of feedback mechanisms into the Interstellar Medium (Supernova Remnants, galaxy/Active Galactic Nuclei outflows), constraints on the Dark Matter and Dark Energy content of the Universe (through clusters and GRBs), equation of state of the densest matter (neutron stars), GRB physics, upper limits on light dark matter particles, accurate measurement of the geometry of space-time by measuring X-ray afterglows of black hole mergers detected through gravitational waves, Active Galactic Nuclei and stellar population surveys, and Solar System physics. The science is feasible with a medium class mission using existing technology combined with innovative instrumental and observational capabilities on a single satellite by: a) observing with fast reaction Gamma-Ray Bursts with a high spectral resolution (R 500). This enables the study of their (star-forming) environment from the Dark to the local Universe and the use of GRB as back light of large scale cosmological structures b) Observing and surveying extended sources (clusters, WHIM) with high sensitivity using two wide field of view X-ray telescopes (one with a high angular resolution and the other with a high spectral resolution). The mission concept includes four main instruments: a Wide-field Spectrometer with excellent energy resolution (3 eV, 1 eV goal), a Wide-Field Imager with high angular resolution (15”) constant over the full 1.4 degree field of view, and a Wide Field Monitor with a FOV of ¼ of the sky, which will trigger the fast repointing. Extension of its energy response up to 1 MeV will be achieved with a GRB detector with no imaging capability. This mission is proposed to ESA as part of the Cosmic Vision call. We will describe the science drivers and the payload of this mission.
Hsiu-Hui Huang (MPE, GERMANY) , Werner Becker (MPE, Germany), Bau-Ching Hsieh (ASIAA, Taiwan), Ronald Elsner (MSFC, USA), Peter Edmonds (SAO, USA), et al.
We report on the archival Hubble Space Telescope (HST) observations of the globular cluster M71 (NGC 6838). Those observations which cover the core of the globular cluster are performed by the Advanced Camera for Surveys (ACS) and the Wide Field Planetary Camera 2 (WFPC2). Inside the half-mass radius (r_h =1.65') of M71, 29 X-ray sources have been detected by the Chandra Observations (Elsner et al. 2007) in the energy range of 0.3 - 8.0 keV, and 5 of which lie within one core radius (r_c =0.63') from the cluster center. We find 26 candidate optical counterparts to Chandra X-ray sources inside the half-mass radius of M71. Based on the X-ray and optical properties of the identifications, candidates of cataclysmic variables(CVs), chromospherically active binaries (ABs), and background galaxies located along the line of sight to M71 are classified in our research.
Randall Smith (JHU & NASA/GSFC)
The Russian Spectrum-X-Gamma (SXG) Mission is now under development to carry out the first moderate-resolution, all-sky survey of the x-ray sky since ROSAT. This mission shares the name of the original SXG developed in the 1980s (and not launched due to budget problems) but has been completely redesigned. SXG is a medium-sized satellite ( 2200 kg) to be launched in 2011/12 into a 600 km equatorial (<5 deg) orbit from Kourou or into a <30 deg orbit from Baikonur as a fallback option. The payload includes eROSITA (extended ROentgen Survey with an Imaging Telescope Array, MPE, Germany) with 7 Wolter-type telescopes, the wide field X-ray monitor Lobster (LU, UK), the X-ray concentrator based on Kumakhov optics ART or coded-mask X-ray telescopes as a fallback (IKI, Russia) and GRB detector (Russian consortium). The mission will conduct the first all-sky survey with an imaging telescope in the 2-12 keV band to discover the hidden population of several hundred thousand obscured supermassive black holes and the first all-sky imaging x-ray time-variability survey. It will observe the extragalactic sky with high enough sensitivity to detect 50,000-100,000 clusters of galaxies for follow-up pointed observations of selected sources to provide a rich new data set for probing dark matter and dark energy. The survey will also provide valuable data on point sources, populations of unresolved sources that make up galactic diffuse emission along the plane, and diffuse emission from hot gas. SXG will also include an x-ray calorimeter spectrometer developed by NASA/GSFC to provide grating-level spectral resolution, recovering part of the science that was lost from the untimely demise of the Suzaku/XRS. The design will incorporate a 1.6 m f/l x-ray telescope (an copy of one of the eROSITA units) coupled to a spare x-ray calorimeter from the XRS program. Operating in a dewar designed and built in Japan, we expect a resolution of 4 eV (FWHM) at 6 keV. The dewar would be based on flight-heritage cryocoolers and cable of long life without cryogens. With this instrument, the long-standing puzzles of the Galactic x-ray emission would finally be addressed with high spectral resolution and better than 2 arcmin spatial resolution over the entire sky. This would create the best chance ever for disentangling and physically identifying the numerous Galactic components responsible for the diffuse x-ray emission. In addition, the instrument could be used for pointed-mode observations (e.g early in the mission and at the completion of the surveys), thereby creating the possibility of a sampling of scientific topics that were planned for the original Suzaku program.
Jinge Xiang (Harvard University) , Julia C. Lee (Harvard University), Michael A. Nowak, Norbert S. Schulz (MIT)
We present results based on our 76 ks Chandra HETGS observation of the "Big Dipper" 4U 1624-490. Specifically, we discuss how the detected Fe line absorption evolves with orbital phase during persistent phases in the context of the geometry of the system as well as changes in plasma conditions over the 4U 1624-490 binary orbit. We show that the evolution of these lines can be modeled using the ``XSTAR'' photoionized code which places the location of "hot" (
K) gas in a region where an Accretion Disk Corona (ADC) is expected to exist an the location of "warm" (
K) gas in a region between the ADC and the disk edge. In addition, we will show how we have used the associated dust scattering halo to derive a geometric distance of 15 kpc to this binary, as well as assess location, uniformity and density of ISM dust grains along the line of sight to this source.