An "optically dark" burst GRB 051022 was detected by GRB 051022 was detected by HETE-2. The detections of candidate X-ray and radio afterglows were reported, whereas no optical afterglow was found in spite of quick follow-up observations. The optical spectroscopic observations of the host galaxy revealed the redshift z = 0.8. Using the data derived by HETE-2 observation of the prompt emission, we found the constant absorption N H = 8.8-2.9+3.1 × 1022 cm -2 and the visual extinction AV = 49-16 +17 mag in the host galaxy. If this is the case, no detection of any optical transient would be quite reasonable. The absorption derived by the Swift XRT observations of the afterglow is fully consistent with those obtained from the early HETE-2 observation. Our analysis implies an interpretation that the absorbing medium may be outside the external shock at R ≥ 1016 cm, which could be a dusty molecular cloud.
ASJC Scopus subject areas
- Physics and Astronomy(all)