In several recent observational studies on Type Ib/c supernovae ( SNe Ib/c ) , the inferred ejecta masses have a peak value of 2.0 – 4.0 M _ { \sun } , in favor of the binary scenario for their progenitors rather than the Wolf-Rayet star scenario .
To investigate the observational properties of relatively low-mass helium stars in binary systems as SN Ib/c progenitors , we constructed atmospheric models with the non-LTE radiative transfer code CMFGEN , using binary star evolution models .
We find that these helium stars can be characterized by relatively narrow helium emission lines if the mass-loss rate during the final evolutionary phase is significantly enhanced as implied by many SN Ib/c observations .
The optical brightness of helium star progenitors can be meaningfully enhanced with a strong wind for M \gtrsim 4.4 ~ { } M _ { \sun } , but hardly affected or slightly weakened for relatively low-mass of \sim 3.0 ~ { } M _ { \odot } , compared to the simple estimate using blackbody approximation .
We further confirm the previous suggestion that the optical brightness would be generally higher for a less massive SN Ib/c progenitor .
In good agreement with previous studies , our results indicate that the optical magnitudes and colors of the recently detected progenitor of the SN Ib iPTF13bvn can be well explained by a binary progenitor with a final helium star mass of about 3.0 – 4.4 M _ { \sun } .