Discovery of enhanced radiative recombination continua of He-like iron and calcium from IC 443 and its implications

Journal Article · Thu Mar 20 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/784/1/74· OSTI ID:22351481

Ohnishi, Takao; Uchida, Hiroyuki; Tsuru, Takeshi Go; Koyama, Katsuji ^[1]; Masai, Kuniaki ^[2]; Sawada, Makoto ^[3]

---

1. Division of Physics and Astronomy, Graduate School of Science, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan)
2. Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan)
3. Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe 5-10-1, Sagamihara, Kanagawa 252-5258 (Japan)

We present deep observations of the Galactic supernova remnant IC 443 with the Suzaku X-ray satellite. We find prominent K-shell lines from iron and nickel, together with a triangle residual at 8-10 keV, which corresponds to the energy of the radiative recombination continuum (RRC) of He-like iron. In addition, the wavy residuals have been seen at ∼5.1 and ∼5.5 keV. We confirm that the residuals show the first enhanced RRCs of He- and H-like calcium found in supernova remnants. These facts provide robust evidence for the recombining plasma. We reproduce the plasma in the 3.7-10 keV band using a recombining plasma model at the electron temperature 0.65 keV. The recombination parameter n {sub e} t (n {sub e} is electron density and t is elapsed time after formation of a recombining plasma) and abundances of iron and nickel are strongly correlated, and hence the errors are large. On the other hand, the ratio of nickel to iron relative to the solar abundances is well constrained to 11{sub −3}{sup +4} (1σ). A possibility is that the large abundance ratio is a result of an asymmetric explosion of the progenitor star.

• OSTI ID: 22351481
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 784; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
ASYMMETRY
CALCIUM
ELECTRON DENSITY
ELECTRON TEMPERATURE
ERRORS
EXPLOSIONS
GALAXIES
IRON
K SHELL
KEV RANGE
NICKEL
PLASMA
RECOMBINATION
SATELLITES
STARS
SUPERNOVA REMNANTS
X RADIATION