THE AFTERGLOWS OF<i>SWIFT</i>-ERA GAMMA-RAY BURSTS. II. TYPE I GRB VERSUS TYPE II GRB OPTICAL AFTERGLOWS

Abstract

We use a large sample of GRB afterglow and prompt-emission data (adding\nfurther GRB afterglow observations in this work) to compare the optical\nafterglows (or the lack thereof) of Type I GRBs with those of Type II GRBs. In\ncomparison to the afterglows of Type II GRBs, we find that those of Type I GRBs\nhave a lower average luminosity and show an intrinsic spread of luminosities at\nleast as wide. From late and deep upper limits on the optical transients, we\nestablish limits on the maximum optical luminosity of any associated supernova,\nconfirming older works and adding new results. We use deep upper limits on Type\nI GRB optical afterglows to constrain the parameter space of possible mini-SN\nemission associated with a compact-object merger. Using the prompt emission\ndata, we search for correlations between the parameters of the prompt emission\nand the late optical afterglow luminosities. We find tentative correlations\nbetween the bolometric isotropic energy release and the optical afterglow\nluminosity at a fixed time after trigger (positive), and between the host\noffset and the luminosity (negative), but no significant correlation between\nthe isotropic energy release and the duration of the GRBs. We also discuss\nthree anomalous GRBs, GRB 060505, GRB 060614, and GRB 060121, in the light of\ntheir optical afterglow luminosities. (Abridged)\n