Dense, Fe-rich Ejecta in Supernova Remnants DEM L238 and DEM L249: A New Class of Type Ia Supernova?

Abstract

We present observations of two LMC supernova remnants (SNRs), DEM L238 and DEM L249, with the Chandra and XMM-Newton X-ray satellites. Bright central emission, surrounded by a faint shell, is present in both remnants. The central emission has an entirely thermal spectrum dominated by strong Fe L-shell lines, with the deduced Fe abundance in excess of solar and not consistent with the LMC abundance. This Fe overabundance leads to the conclusion that DEM L238 and DEM L249 are remnants of thermonuclear (Type Ia) explosions. The shell emission originates in gas swept up and heated by the blast wave. A standard Sedov analysis implies about 50 solar masses in both swept-up shells, SNR ages between 10,000 and 15,000 yr, low (< 0.05 cm^-3) preshock densities, and subluminous explosions with energies of 3x10^50 ergs. The central Fe-rich supernova ejecta are close to collisional ionization equilibrium. Their presence is unexpected, because standard Type Ia SNR models predict faint ejecta emission with short ionization ages. Both SNRs belong to a previously unrecognized class of Type Ia SNRs characterized by bright interior emission. Denser than expected ejecta and/or a dense circumstellar medium around the progenitors are required to explain the presence of Fe-rich ejecta in these SNRs. Substantial amounts of circumstellar gas are more likely to be present in explosions of more massive Type Ia progenitors. DEM L238, DEM L249, and similar SNRs could be remnants of ``prompt'' Type Ia explosions with young (~100 Myr old) progenitors.

24 pages, 8 figures, ApJ, in press

References in corpus (2)

• Rates and properties of type Ia supernovae as a function of mass and star-formation in their host galaxies
• Late-Time Spectroscopy of SN 2002cx: The Prototype of a New Subclass of Type Ia Supernovae

Cited by in corpus (13)

• A Deep Chandra Observation of Kepler's Supernova Remnant: A Type Ia Event with Circumstellar Interaction
• The Stellar Ancestry of Supernovae in the Magellanic Clouds - I. the Most Recent Supernovae in the Large Magellanic Cloud
• The influence of supernova remnants on the interstellar medium in the Large Magellanic Cloud seen at 20--600 $\mu$m wavelengths
• X-ray Emitting Ejecta in Puppis A Observed with Suzaku
• A common-envelope wind model for Type Ia supernovae (I): binary evolution and birth rate
• New Optically Identified Supernova Remnants in the Large Magellanic Cloud
• Chandra View of DA 530: A Sub-Energetic Supernova Remnant with a Pulsar Wind Nebula?
• SRG/eROSITA discovery of a radio faint X-ray candidate supernova remnant SRGe J003602.3+605421=G121.1-1.9
• Rethinking the N(H2)/I(CO) Conversion Factor
• Common envelope to explosion delay time distribution (CEEDTD) of type Ia supernovae
• X-ray counterpart detection and gamma-ray analysis of the SNR G279.0+01.1 with eROSITA and Fermi-LAT
• Linking the properties of accreting white dwarfs with the ionization state of their ambient medium
• A look at the high energy aspects of the supernova remnant G309.8+00.0 with eROSITA and Fermi-LAT