Upper limits on bolometric luminosities of ten type Ia supernova progenitors from Chandra observations
(3 votes over all institutions)
We present an analysis of Chandra observations of the position of ten nearby (< 25 Mpc) type Ia supernovae, taken before the explosions. No sources corresponding to progenitors were found in any of the observations. We calculated upper limits on the bolometric luminosities of the progenitors assuming black body X-ray spectra with temperatures of 30-150 eV. This is inspired by the fact that luminous supersoft X-ray sources have been suggested as the direct progenitors of type Ia supernovae. The upper limits of three supernovae in our sample are comparable to the luminosities of the brightest observed supersoft sources, ruling out such sources as the progenitors of these supernovae. Our findings are in agreement with statistical studies comparing the observed type Ia supernova rate to the number of supersoft sources or the integrated X-ray luminosity in external galaxies. This suggest that either the progenitors of type Ia supernovae are not accreting white dwarfs, or that they are but do not look like the classical supersoft sources, e.g. because they are obscured.
