M85 optical transient 2006-1 ( M85 OT 2006-1 ) is the most luminous member of the small family of V838 Mon-like objects , whose nature is still a mystery .
This event took place in the Virgo cluster of galaxies and peaked at an absolute magnitude of M _ { I } \approx - 13 .
Here we present Hubble Space Telescope images of M85 OT 2006-1 and its environment , taken before and after the eruption , along with a spectrum of the host galaxy at the transient location .
We find that the progenitor of M85 OT 2006-1 was not associated with any star forming region .
The g and z -band absolute magnitudes of the progenitor were fainter than about -4 and -6 mag , respectively .
Therefore , we can set a lower limit of \sim 50 Myr on the age of the youngest stars at the location of the progenitor that corresponds to a mass of < 7 M _ { \odot } .
Previously published line indices suggest that M85 has a mean stellar age of 1.6 \pm 0.3 Gyr .
If this mean age is representative of the progenitor of M85 OT 2006-1 , then we can further constrain its mass to be less than 2 M _ { \odot } .
We compare the energetics and mass limit derived for the M85 OT 2006-1 progenitor with those expected from a simple model of violent stellar mergers .
Combined with further modeling , these new clues may ultimately reveal the true nature of these puzzling events .