  The effect of galaxy interactions on star formation has been investigated
using Data Release 1 of the Sloan Digital Sky Survey (SDSS). Both the imaging
and spectroscopy data products have been used to construct a catalogue of
nearest companions to a volume limited (0.03 < z < 0.1) sample of galaxies
drawn from the main galaxy sample of SDSS. Of the 13973 galaxies in the volume
limited sample, we have identified 12492 systems with companions at projected
separations less than 300 kpc. Star-formation rates for the volume-limited
sample have been calculated from extinction and aperture corrected H-alpha
luminosities and, where available, IRAS data. Specific star formation rates
were calculated by estimating galaxy masses from z-band luminosities, and
r-band concentration indices were used as an indicator of morphological class.
The mean specific star-formation rate is found to be strongly enhanced for
projected separations of less than 30 kpc. For late-type galaxies the
correlation extends out to projected separations of 300 kpc and is most
pronounced in actively star-forming systems. The specific star-formation rate
is observed to decrease with increasing recessional velocity difference, but
the magnitude of this effect is small compared to that associated with the
projected separation. We also observe a tight relationship between the
concentration index and pair separation; the mean concentration index is
largest for pairs with separations of approximately 75 kpc and declines rapidly
for separations smaller than this. This is interpreted as being due to the
presence of tidally-triggered nuclear starbursts in close pairs. Further, we
find no dependence of star formation enhancement on the morphological type or
mass of the companion galaxy
