397 research outputs found
Performance of single photon-counting X-ray charge coupled devices
Results of intial performance tests on X-ray sensing properties of charge-coupled devices (CCDs) are presented. CCDs have demonstrated excellent spatial resolution and good spectral resolution, superior to that of non-imaging proportional counters
0103-72.6: A New Oxygen-Rich Supernova Remnant in the Small Magellanic Cloud
010372.6, the second brightest X-ray supernova remnant (SNR) in the Small
Magellanic Cloud (SMC), has been observed with the {\it Chandra X-Ray
Observatory}. Our {\it Chandra} observation unambiguously resolves the X-ray
emission into a nearly complete, remarkably circular shell surrounding bright
clumpy emission in the center of the remnant. The observed X-ray spectrum for
the central region is evidently dominated by emission from reverse shock-heated
metal-rich ejecta. Elemental abundances in this ejecta material are
particularly enhanced in oxygen and neon, while less prominent in the heavier
elements Si, S, and Fe. We thus propose that 010372.6 is a new
``oxygen-rich'' SNR, making it only the second member of the class in the SMC.
The outer shell is the limb-brightened, soft X-ray emission from the swept-up
SMC interstellar medium. The presence of O-rich ejecta and the SNR's location
within an H{\small II} region attest to a massive star core-collapse origin for
010372.6. The elemental abundance ratios derived from the ejecta suggest an
18 M progenitor star.Comment: 6 pages (ApJ emulator format), including 5 figures and 2 tables. For
high quality Figs.1,2, & 3, contact [email protected]. Accepted by the ApJ
Letter
The Radial Structure of SNR N103B
We report on the results from a Chandra ACIS observation of the young,
compact, supernova remnant N103B. The unprecedented spatial resolution of
Chandra reveals sub-arcsecond structure, both in the brightness and in spectral
variations. Underlying these small-scale variations is a surprisingly simple
radial structure in the equivalent widths of the strong Si and S emission
lines. We investigate these radial variations through spatially resolved
spectroscopy using a plane-parallel, non-equilibrium ionization model with
multiple components. The majority of the emission arises from components with a
temperature of 1 keV: a fully ionized hydrogen component; a high ionization
timescale (n_e*t > 10^12 s cm^-3) component containing Si, S, Ar, Ca, and Fe;
and a low ionization timescale (n_e*t ~ 10^{11} s cm^-3) O, Ne, and Mg
component. To reproduce the strong Fe Kalpha line, it is necessary to include
additional Fe in a hot (> 2 keV), low ionization (n_e*t ~ 10^10.8 s cm^-3)
component. This hot Fe may be in the form of hot Fe bubbles, formed in the
radioactive decay of clumps of 56Ni. We find no radial variation in the
ionization timescales or temperatures of the various components. Rather, the Si
and S equivalent widths increase at large radii because these lines, as well as
those of Ar and Ca, are formed in a shell occupying the outer half of the
remnant. A shell of hot Fe is located interior to this, but there is a large
region of overlap between these two shells. In the inner 30% of the remnant,
there is a core of cooler, 1 keV Fe. We find that the distribution of the
ejecta and the yields of the intermediate mass species are consistent with
model prediction for Type Ia events.Comment: 34 pages, including 7 tables and 7 figures, Accepted by Ap
Joint Astrophysics Nascent Universe Satellite:. utilizing GRBs as high redshift probes
The Joint Astrophysics Nascent Universe Satellite (JANUS) is a multiwavelength cosmology mission designed to address fundamental questions about the cosmic dawn. It has three primary science objectives: (1) measure the massive star formation rate over 5 ≤ z ≤ 12 by discovering and observing high-z gamma-ray bursts (GRBs) and their afterglows, (2) enable detailed studies of the history of reionization and metal enrichment in the early Universe, and (3) map the growth of the first supermassive black holes by discovering and observing the brightest quasars at z ≥ 6. A rapidly slewing spacecraft and three science instruments – the X-ray Coded Aperture Telescope (XCAT), the Near InfraRed Telescope (NIRT), and the GAmma-ray Transient Experiment for Students (GATES) – make-up the JANUS observatory and are responsible for realizing the three primary science objectives. The XCAT (0.5–20 keV) is a wide field of view instrument responsible for detecting and localizing ∼60 z ≥ 5 GRBs, including ∼8 z ≥ 8 GRBs, during a 2-year mission. The NIRT (0.7–1.7 µm) refines the GRB positions and provides rapid (≤ 30 min) redshift information to the astronomical community. Concurrently, the NIRT performs a 20, 000 deg2 survey of the extragalactic sky discovering and localizing ∼300 z ≥ 6 quasars, including ∼50 at z ≥ 7, over a two-year period. The GATES provides high-energy (15 keV −1.0 MeV) spectroscopy as well as 60–500 keV polarimetry of bright GRBs. Here we outline the JANUS instrumentation and the mission science motivations
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