Upper limits on bolometric luminosities of three type Ia supernova progenitors - New results in the ongoing Chandra archival search for type Ia supernova progenitors

We present analysis of Chandra archival, pre-explosion data of the positions of three nearby (< 25 Mpc) type Ia supernovae, SN2011iv, SN2012cu & SN2012fr. No sources corresponding to the progenitors were found in any of the observations. Combining all sources with well defined backgrounds does not reveal any evidence for X-ray emission from the progenitors either. We calculated upper limits on the bolometric luminosities of the progenitors, under the assumption that they were black bodies with effective temperatures between 30 and 150 eV, corresponding to 'canonical' supersoft X-ray sources. The upper limits of SN2012fr straddles the Eddington luminosity of canonical supersoft sources, but fainter canonical supersoft sources cannot be ruled out by this study. We also compare our upper limits with known compact binary supersoft X-ray sources. This study is a continuation of the campaign to directly detect or constrain the X-ray characteristics of pre-explosion observations of nearby type Ia supernova progenitors; with the results reported in Nielsen, Voss & Nelemans (see reference in Introduction), the number of nearby type Ia supernovae for which pre-explosion images are available in the Chandra archive is now 13 and counting.