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We present Swift UVOT (1600-3000A) 3-band photometry for 41 galaxies in 11nearby (<4500km/s) Hickson Compact Groups (HCGs) of galaxies. We use theuvw2-band (2000A) to estimate the dust-unobscured component, SFR_UV, of thetotal star-formation rate, SFR_T. We use Spitzer MIPS 24-micron photometry toestimate SFR_IR, the dust-obscured component of SFR_T. We obtainSFR_T=SFR_UV+SFR_IR. Using 2MASS K_s band based stellar mass, M*, estimates, wecalculate specific SFRs, SSFR=SFR_T/M*. SSFR values show a clear andsignificant bimodality, with a gap between low (<~3.2x10^-11 / yr) and highSSFR (>~1.2x10^-10 / yr) systems. All galaxies with MIR activity index a_IRAC<= 0 (>0) are in the high- (low-) SSFR locus, as expected if high levels ofstar-formation power MIR emission from polycyclic aromatic hydrocarbonmolecules and a hot dust continuum. All elliptical/S0 galaxies are in thelow-SSFR locus, while 22 out of 24 spirals/irregulars are in the high-SSFRlocus, with two borderline cases. We divide our sample into three subsamples(I, II and III) according to decreasing HI-richness of the parent galaxy groupto which a galaxy belongs. Consistent with the SSFR and a_IRAC bimodality, 12out of 15 type-I (11 out of 12 type-III) galaxies are in the high- (low-) SSFRlocus, while type II galaxies span almost the full range of SSFR values. UnlikeHCG galaxies, galaxies in a comparison quiescent SINGS sub-sample arecontinuously distributed both in SSFR and a_IRAC. Any uncertainties can onlyfurther enhance the SSFR bimodality. These results suggest that an environmentcharacterized by high galaxy number-densities and low galaxyvelocity-dispersions, such as the one found in compact groups, plays a key rolein accelerating galaxy evolution by enhancing star-formation processes ingalaxies and favoring a fast transition to quiescence.(abridged)

UV+IR Star Formation Rates: Hickson Compact Groups with Swift and Spitzer