TITLE:   GCN CIRCULAR
NUMBER:  32802
SUBJECT: GRB 221009A X-ray light-curve and the indication of TeV light-curve
DATE:    22/10/19 15:28:45 GMT
FROM:    Remo Rufinni at ICRA  <ruffini@icra.it>

Y. Aimuratov, L. Becerra, C.L. Bianco, C. Cherubini, S. Filippi, M.
Karlica, Liang Li, R. Moradi, F. Rastegar Nia, J.A. Rueda, R. Ruffini, N.
Sahakyan, Y. Wang, S.S. Xue, on behalf of the ICRANet team, report:

LHAASO observed more than 5000 very high energy (VHE) photons in GRB
221009A, with the highest energy reaching 18 TeV (GCN 32677). Previously,
high energy TeV emissions were also observed in GRB 180720B (Abdalla et al.
2019), 190114C (MAGIC Collaboration 2019), 190829A (H.E.S.S. Collaboration
2021) and 201216C (Blanch et al. GCN 29075). A common feature of these
bursts is that the TeV light-curve follows a power-law decay with a similar
index as the X-ray light-curve, and the TeV luminosity is tens of percent
of the X-ray luminosity (see attached figure 1 and the references of
Abdalla et al. 2019, MAGIC Collaboration 2019 and H.E.S.S. Collaboration
2021, Ruffini et al. 2021, Rueda et al. 2022, Rastegarnia et al. 2022, Wang
et al. 2022). Here we present the X-ray light-curve of GRB 221009A observed
by Swift-XRT (GCN 32651), and the t0 is taken from the Fermi-GBM trigger
time (GCN 32636), see attached figure 2, a power-law of index -1.58 is
fitted. The shadow region shows 20%-60% of the X-ray luminosity, which is
expected to be the 0.3-1 TeV luminosity (17% less luminous for 0.5-18 TeV
assuming a power-law spectrum of photon index -2) of this new burst if it
shares the same behavior as the previous ones. We encourage further
observations, especially the VHE observations, because this burst probably
is more luminous than the previous ones, and it will be precious to have a
late time (after days) VHE luminosity which was never achieved before, as
well as the optical observations for the supernova appearance (GCN 32670,
GCN 32780).

Figure 1: http://www.icranet.org/docs/fig1.png
Figure 2: http://www.icranet.org/docs/fig2.png



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