  Solar-like oscillations have been observed by {{\it Kepler}} and CoRoT in
several solar-type stars.
  We study the variations of stellar p-mode linewidth as a function of
effective temperature.
  Time series of 9 months of Kepler data have been used. The power spectra of
42 cool main-sequence stars and subgiants have been analysed using both Maximum
Likelihood Estimators and Bayesian estimators, providing individual mode
characteristics such as frequencies, linewidths and mode heights.
  Here we report on the mode linewidth at maximum power and at maximum mode
height for these 42 stars as a function of effective temperature.
  We show that the mode linewidth at either maximum mode height or maximum
amplitude follows a scaling relation with effective temperature, which is a
combination of a power law plus a lower bound. The typical power law index is
about 13 for the linewidth derived from the maximum mode height, and about 16
for the linewidth derived from the maximum amplitude while the lower bound is
about 0.3 microHz and 0.7 microHz, respectively. We stress that this scaling
relation is only valid for the cool main-sequence stars and subgiants, and does
not have predictive power outside the temperature range of these stars.
