Other
Scientific paper
May 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21642807b&link_type=abstract
American Astronomical Society, AAS Meeting #216, #428.07; Bulletin of the American Astronomical Society, Vol. 41, p.841
Other
Scientific paper
We present a spectral analysis of our 250 ks Chandra observation of the youngest Galactic supernova remnant G1.9+0.3. While the integrated spectrum is dominated by synchrotron emission, radio-bright but X-ray faint regions show prominent thermal emission, with K alpha emission from Si, S, Ar, Ca, and Fe. We find Doppler broadening velocities of order 26,000 km/s, and an overall blueshift of -4,000 km/s. Enhanced abundances are suggested. Most strikingly, we find that an additional spectral line is required at 4.1 keV, which we identify with an inner-shell transition in radioactive 44Sc produced by the electron-capture decay of 44Ti, with a mean life of 89 yr. The line flux we obtain implies an initial mass of 44Ti synthesized in the explosion of 1.9 (2.9) x 10-5 solar masses, for an assumed age of 100 (140) yr. The 44Sc line is produced independently of electron excitation, so can be seen in both shocked and unshocked-ejecta regions. We show evidence of 44Sc emission toward the remnant center, where other lines are weaker. Our inferred 44Ti mass is consistent with several predictions for both Type Ia and core-collapse supernovae. For Type Ia, the mass is more consistent with the results of recent nonspherical calculations.
We map the spatial distribution of heavy-element ejecta with a multiscale image estimation method suitable for our photon-limited Chandra data. Joint spatio-spectral denoising directly applied to Chandra data cubes allows us to spatially localize ejecta clumps down to arcsec scales, notwithstanding low (about 500) total counts in lines. The brightest ejecta knot, located in the middle of the radio-bright shell in the north, exhibits very strong lines of Si, S, Ar, C, and Fe, but the Sc line is much weaker, if present at all. The presence of Fe-rich ejecta favors a Type Ia explosion.
Borkowski Kazimierz J.
Green David A.
Hwang Una
Krishnamurthy Kalyani
Petre Rob
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