  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.
