[vsnet-grb-info 5314] GRB 071025 Milagro GeV/TeV Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7004
SUBJECT: GRB 071025 Milagro GeV/TeV Observations
DATE:    07/10/25 23:08:35 GMT
FROM:    Pablo Saz Parkinson at UCSC/Milagro  <pablo at scipp.ucsc.edu>

Pablo Saz Parkinson (UC Santa Cruz) on behalf of the Milagro
collaboration reports:

We have searched Milagro data for emission at GeV/TeV energies from
GRB 071025 detected by Swift (GCN Circ 6986, C. Pagani et al.),
during the main period of emission lasting 422s (GCN Circ 6996, S. D.
Barthelmy et al.). No evidence for prompt GeV/TeV emission was found.
TeV photons are attenuated by pair production with infrared photons in
intergalactic space. We calculate uppers limits using the extragalactic
infrared background light (EBL) absorption model of
Primack et al. 2005 (AIP Conf. Proc. 745, p. 23).

A preliminary analysis, assuming a differential photon spectral
index of -2.4, gives upper limits on E^2dN/dE at 99% confidence of:

E^2 dN/dE at 200 GeV < 1.4 * 10^(-6) erg cm^(-2) (Assuming z=0)

and

E^2 dN/dE at 200 GeV < 2.3 * 10^(-5) erg cm^(-2) (Assuming z=0.5)
E^2 dN/dE at 200 GeV < 2.0 * 10^(-3) erg cm^(-2) (Assuming z=2.0)

These upper limits are preliminary and will be refined with further
analysis.