Low redshift quasars in the SDSS Stripe 82: Associated companion
  galaxies and signature of star formation
  We obtained optical spectroscopy of close (< 80 kpc) companion objects of a
sample of 12 low redshift quasars (z < 0.3 ) selected from the SDSS Stripe82
area and that are in the subsample of 52 QSOs for which both multicolor host
galaxies properties and galaxy environment was recently investigated in detail.
We found that for 8 out of 12 sources the companion galaxy is associated to the
QSO having a difference of radial velocity that is less than 400 km/s. Many of
these associated companions exhibit [OII] $\lambda$3727 \AA~ emission lines
suggestive of episodes of (recent) star formation possibly induced by past
interactions. The SFR of the companion galaxies as derived from [OII] line
luminosity is, however, modest, with a median value of 1.0 +-0.8 M_sun/yr, and
the emission lines are barely consistent with expectation from gas ionization
by the QSO. The role of the QSO for inducing star formation in close companion
galaxies appears meager. For three objects we also detect the starlight
spectrum of the QSO host galaxy which is characterized by absorption lines of
old stellar population and [OII] emission line.
