[vsnet-grb-info 20938] GRB 18020B long follow up requested
GCN Circulars
gcncirc at capella2.gsfc.nasa.gov
Wed Jul 25 17:53:35 JST 2018
TITLE: GCN CIRCULAR
NUMBER: 23036
SUBJECT: GRB 18020B long follow up requested
DATE: 18/07/25 08:52:55 GMT
FROM: Arnon Dar at Technion-Israel Inst. of Tech <arnon at physics.technion.ac.il>
Long follow up of the afterglow of the extremely bright GRB
180720B (Swift-BAT detection: Siegel et al., GCN #22973, GCN
#22975; Fermi-LAT detection: Bissaldi and Racusin, GCN #22980;
Fermi-GBM detection: Roberts et al., GCN #22981; Konus Wind
detection: Frederiks et al. GCN 230110) is urged. It will provide
another critical test of GRB theories. Its current late-time X-ray
afterglow, measured with Swift XRT, decays like a single power-law
with a temporal index alpha=1.34+/-0.01 and an unabsorbed spectral
index beta=0.82+/-0.04 (Evans et al. Swift-XRT GRB lightcurve
repository). It satisfies well the Cannonball model closure relation
alpha=beta+1/2 (e.g., Dado and Dar, PhRvD, 94, 3007 (2016)) for
the late time unabsorbed afterglows of SN-GRBs (while those of
SN-less GRBs satisfy alpha=2, e.g., Dado and Dar arXiv:1807.08726).
An SN akin to SN1998bw may be resolved from the optical afterglows
around day ~15. An achromatic break in the late time afterglow
is expected only if the host galaxy is aligned near face on.
More information about the vsnet-grb-info
mailing list