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O n the evening of January 28th - 29th LOTIS responded to 4 GCN Triggers.

BATSE Trigger 7359 - Maxbc

BATSE Trigger 7360 - Original

BATSE Trigger 7360 - Final

BATSE Trigger 7360 - Locburst

G RB 990129b (Trigger 7359) was detected by BATSE at 3:41:38.9 UT (7:41:38.9 PST). This burst was a short single peaked burst lasting only 0.1 seconds. Due to insufficient counts an 'Original' GCN trigger was not ditributed. Approximately 640 seconds after the BATSE trigger the 'Maxbc' GCN coordinates of RA=99.67, Dec=+16.08 were distributed to LOTIS. Over the next 180 minutes LOTIS obtained approximately 150 images of this position. The final Huntsville Coordinates of this burst were RA=100.97, Dec=-19.08 with a statistical error of 12.21 degrees. Due to the large difference between the 'Maxbc' coordinates and the Huntsville coordinates and the size of the one sigma error box this is not considered a 'good' LOTIS event.

G RB 990129 (Trigger 7360) was detected by BATSE at 5:15:50.9 UT (9:15:50.9 PST). The duration of the burst was approximately 220 seconds. This was a complex burst with many peaks which reached maximum flux at Trigger + 47 seconds.

L OTIS received the 'Original' GCN coordinates of RA=107.60, Dec=-1.73 at 5:15:56.7 UT. After a slew time of 3.7 seconds LOTIS began imaging at 5:16:00.4 UT, just 9.5 seconds after the burst began.

A t 5:18:09.7 UT or approximately 138.8 seconds after the burst began LOTIS received the 'Final' GCN coordinates of RA=101.81, Dec=-7.81. At 5:18:09.7 after a 2.0 second slew time LOTIS began imaging the area of these more accurate coordinates. The burst was still emitting gamma-rays when LOTIS began imaging this location.

L OTIS obtained six images of the position centered on the 'Original' GCN coordinates and 49 images of the position centered on the 'Final' GCN coordinates. The final Huntsville coordinates of GRB 990129 are RA=94.93, Dec=-12.28 with a statistical error of 0.354 degrees. The plot below shows the gamma-ray light curve of GRB 990129. The shaded areas show the times of the first seven LOTIS images.

GRB 990129 Gamma-Ray Light Curve

T he plots below show the LOTIS coverage together with the BATSE 1-sigma and 3-sigma error circles. The top plot shows the coverage during the first six images and the bottom plot shows the coverage for the next 49 images.

L OTIS covered approximately 2/3 of the BATSE 3-sigma error circle simultaneous with gamma-ray emission.

GRB 990129 Coverage

GRB 990129 Coverage

A pproximately 18 minutes after the start of GRB 990129 LOTIS received the even more accurate 'Locburst' GCN coordinates of RA=99.11, Dec=-8.23. LOTIS continued to image this area for the remainder of the evening obtaining a total of more than 450 images.

A nalysis of this event is ongoing.

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