GRB 050826: A SUBLUMINOUS EVENT AT z = 0.296 FINDS ITS PLACE IN THE LUMINOSITY DISTRIBUTION OF GAMMA-RAY BURST AFTERGLOWS

We present the optical identification and spectroscopy of the host galaxy of GRB 050826 at a redshift z = 0.296±0.001. Image subtraction among observations obtained on three consecutive nights, reveals a fading object 5 hr after the burst, confirming its identification as the optical afterglow of this event. Deep imaging shows that the optical afterglow is offset by 0.4 (1.76 kpc) from the center of its irregular host galaxy, which is typical for long-duration gamma-ray bursts. Combining these results with X-ray measurements acquired by the Swift XRT instrument, we find that GRB 050826 falls entirely within the subluminous, subenergetic group of long gamma-ray bursts at low redshift (z <∼ 0.3). The results are discussed in the context of models that possibly account for this trend, including the nature of the central engine, the evolution of progenitor properties as a function of redshift, and incompleteness in current gamma-ray burst samples. Subject headings: gamma rays: bursts – supernovae: general