Gamma-ray Burst 100324A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #10544
  J. R. Cummings (GSFC/UMBC) and D. M. Palmer (LANL) on behalf of the Swift team
  At 00:21:27 on March 24, 2010, Swift-BAT detected a rate increase. The source was found onboard, but not at sufficient significance to trigger an automated GRB followup response. A significant source was found in ground analysis at RA, Dec 98.612, -9.735, which is:

  RA (J2000)    06h 34m 26.8s
  Dec (J2000)   -9d 44' 6.4"
  

  with an estimated uncertainty of 2.5 arcmin (radius, 90% containment).
  The burst had multiple peaks with a T90 of about 6 seconds.
  The spectrum of the burst is best fit with a simple powerlaw with a rather soft index of 2.4 +- 0.3. The fluence in the range 15-150 keV was 7 +- 3 x 10^-8 erg/cm^2 (68% confidence). The 1-second peak flux from T-0.3 sec was 0.3 +- 0.1 photons/cm^2.
  Because the burst was not triggered onboard, there are no automated data products. A Swift TOO has been requested.
• GCN Circular #10545
  A. Updike (Clemson University), M. Nardini, A. Rau, F. Olivares, and J.Greiner (all MPE Garching) report on behalf of the GROND team:
  We observed the field of GRB 100324A (ground analysis of Swift/BAT data, Cummings et al., GCN #10544) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPI/ESO telescope at La Silla Observatory (Chile). Observations started on 24 March 2010 at 23:41 UT, 23.3 hours after the GRB. The field was observed during a second epoch, starting at 00:10 UT on 26 March 2010, 47.9 hours after the burst.
  Our i'-band and H-band observations cover 95% and 100% of the 2.5' BAT error circle, respectively. Image subtraction between the two observing epochs does not reveal any variable source. The first image, consisting of 24.8 min exposure in g'r'i'z' and 20 min in JHK, yields the following 3-sigma upper limits (both AB magnitudes):

  i' > 23.6 mag
  H > 21.6 mag
  

  which were obtained using the GROND zero points and 2MASS field stars as reference. The given magnitudes are not corrected for the significant Galactic extinction corresponding to a reddening of E(B-V) = 0.71 mag (Schlegel et al. 1998).