An extended search for transient events in the COBE/DMR database associated with cosmic gamma-ray bursts

We report on an extension of earlier work to search the archival database of the Differential Microwave Radiometers (DMR) aboard the COBE satellite for evidence of transient events at microwave wavelengths associated with cosmic gamma-ray bursts (GRBs). Over its four-year lifetime the DMR experiment repeatedly surveyed the sky to measure fluctuations in the cosmic microwave background. On a number of occasions at least one of the horns of the DMR was also serendipitously pointing in the direction of a cosmic gamma-ray burst at the moment of burst occurrence. Our original investigation covered the eight-month period April–December 1991 when a number of GRBs were observed by the COBE/DMR at or within a few seconds of the CGRO/BATSE trigger time. Upper limits only were obtained for any simultaneous microwave flux from these events, in the range 7–42 kJy. Most recently, we have extended our search using the additional 24 months of COBE DMR data now publicly available, covering the time period January 1992 thr...