TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2917 SUBJECT: GRB041219; RXTE ASM Observations DATE: 04/12/28 16:42:09 GMT FROM: Al Levine at MIT Alan Levine and Ron Remillard (MIT) on behalf of the RXTE ASM Team at MIT and GSFC: GRB041219 (Mereghetti et al., GCN Circular 2866; and Barthelmy et al., GCN Circular 2874) was observed during two dwells, each of duration 90 s, with Scanning Shadow Camera 3 of the RXTE ASM. The observations cover the interval 2004 December 19 1:42:24 to 1:45:30 UTC except for a single 6 s gap in the middle of the interval. Automated real-time analysis of RXTE ASM data yielded a detection of GRB041219 and an error box: RA, Dec (error box center; J2000): 7.085 62.727 degrees Position angle of the error box long direction): 105.72 degrees Error box half width: 0.037 degrees Error box half length: 0.7 degrees in which is found the position derived by Bloom et al. (GCN Circular 2893). In count rate data, the event appears as a single peak with possible substructure lasting about 50 s in the 1.5-3 keV and 3-5 keV bands and about 25 s in the 5-12 keV band. The peak fluxes were approximately 3, 4 and 6 Crab in the 1.5-3, 3-5, and 5-12 keV bands, respectively. The initial sharp rise of this peak (best defined in the 5-12 keV band) occurs at UTC 2004:354:01:43:30 with an uncertainty of about 2 seconds. The background before this time appears to vary; this could be the tail of an earlier GRB-related peak or it could be variation of an unrelated source. The times quoted herein are times at the position of the spacecraft; they have not been corrected to the barycenter of the solar system. In the time interval covered by the ASM, the Swift BAT light curves (Fenimore et al., GCN Circular 2906) show a single relatively inconspicuous small enhancement that appears to start at about the same time as the peak seen in the ASM data. The ASM coverage does not cover the first peak seen by BAT or the later strong peaks. This message is citeable.