* Astronomy

Blobrana · L

RE: Sagittarius A East

Blobrana · L

Title: Three-Dimensional Observations of H_2 Emission around Sgr A East - I. Structure in the Central 10 Parsecs of Our Galaxy
Authors: Sungho Lee, Soojong Pak, Minho Choi, Christopher J. Davis, T. R. Geballe, Robeson M. Herrnstein, Paul T. P. Ho, Y. C. Minh, Sang-Gak Lee

We have obtained velocity-resolved spectra of the H_2 v=1-0 S(1) (lambda = 2.1218 micron) emission line at 2 arcsec angular resolution (or 0.08 pc spatial resolution) in four regions within the central 10 pc of the Galaxy where the supernova-like remnant Sgr A East is colliding with molecular clouds. To investigate the kinematic, physical, and positional relationships between the important gaseous components in the centre, we compared the H_2 data cube with previously published NH_3 data. The projected interaction-boundary of Sgr A East is determined to be an ellipse with its centre offset 1.5 pc from Sgr A* and dimensions of 10.8 pc X 7.6 pc. This H_2 boundary is larger than the synchrotron emission shell but consistent with the dust ring which is believed to trace the shock front of Sgr A East. Since Sgr A East is driving shocks into its nearby molecular clouds, we can determine their positional relationships using the shock directions as indicators. As a result, we suggest a revised model for the three-dimensional structure of the central 10 pc. The actual contact between Sgr A East and all of the surrounding molecular material, including the circum-nuclear disk and the southern streamer, makes the hypothesis of infall into the nucleus and feeding of Sgr A* very likely.

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Blobrana · L

Date: Jun 10 00:04 2005

Title: A Candidate Neutron Star Associated with Galactic Center Supernova
Remnant Sagittarius A East
Authors: Sangwook Park (Penn State), Michael P. Muno (UCLA), Frederick K.
Baganoff (MIT), Yo****omo Maeda (ISAS), Mark Morris (UCLA), George Chartas
(Penn State), Divas Sanwal (Penn State), David N. Burrows (Penn State), and
Gordon P. Garmire (Penn State)
Comments: ApJ preprint style 28 pages, 1 color fig (fig1), Accepted by ApJ
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We present imaging and spectral studies of the supernova remnant (SNR)
Sagittarius (Sgr) A East from deep observations with the Chandra X-Ray Observatory. The spatially-resolved spectral analysis of Sgr A East reveals the presence of a two-temperature thermal plasma (kT _ 1 keV and 5 keV) near the center
of the SNR. The central region is dominated by emission from highly-ionized iron rich ejecta.
We estimate a conservative upper limit on the total Fe ejecta mass
of the SNR, MFe less than 0.27 M⊙. Comparisons with standard SN nucleosynthesis models suggest that this Fe mass limit is consistent with a Type II Supernova explosion for the origin of Sagittarius A East.
On the other hand, the soft X-ray emission extending toward the north of the SNR can be described by a single-temperature (kT_ 1.3 keV) thermal plasma with normal chemical composition. This portion of the supernova remnant is thus X-ray emission from the heated interstellar medium rather than the metal-rich stellar ejecta.
We point out that a hard pointlike source CXOGC J174545.5-285829 (the so-called “cannonball”) at the northern edge of the supernova remnant shows unusual X-ray characteristics among other Galactic centre sources. The
morphological, spectral, and temporal characteristics of this source suggest an identification as a high-velocity neutron star.
Based on the suggested Type II origin for the SNR Sgr A East and the proximity between the two, we propose that CXOGC J174545.5-285829 is a high-velocity neutron star candidate, born from the core-collapse supernova which also created the supernova remnant Sgr A East.

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(Fixed this link - Ed)

-- Edited by Blobrana at 22:18, 2005-06-10