Chandra ACIS Survey of M33 (ChASeM33): X-Ray Imaging Spectroscopy of M33SNR 21, the Brightest X-Ray Supernova Remnant in M33
We present and interpret new X-ray data for M33SNR 21, the brightest X-ray supernova remnant (SNR) in M33. The SNR is in seen projection against (and appears to be interacting with) the bright H ii region NGC 592. Data for this source were obtained as part of the Chandra ACIS Survey of M33 (ChASeM33) Very Large Project. The nearly on-axis Chandra data resolve the SNR into a 500 diameter (20 pc at our assumed M33 distance of 817 58 kpc) slightly elliptical shell. The shell is brighter in the east, which suggests that it is encountering higher density material in that direction. The optical emission is coextensive with the X-ray shell in the north, but extends well beyond the X-ray rim in the southwest. Modeling the X-ray spectrum with an absorbed sedov model yields a shock temperature of 0:46þ0:01 0:02 keV, with an ionization timescale of net ¼ 2:1þ0:2 0:3 ; 1012 cm3 s and half-solar abundances (0:45þ0:12 0:09). Assuming Sedov dynamics gives an average preshock H density of 1:7 0:3 cm3 . The dynamical age estimate is 6500 600 yr, while the best-fit net value and derived ne gives 8200 1700 yr; the weighted mean of the age estimates is 6700 600 yr. We estimate an X-ray luminosity (0.25Y4.5 keV) of (1:2 0:2) ; 1037 ergs s1 (absorbed), and (1:7 0:3) ; 1037 ergs s1 (unabsorbed), in good agreement with the recent XMM-Newton determination. No significant excess hard emission was detected; the luminosity P1:2 ; 1035 ergs s1 (2Y8 keV ) for any hard point source.
The Astrophysical Journal, Vol. 663, 234-243, 2007 July 1.