GCN Circular 2656
Subject
XRF040812: possible afterglow second Chandra observation
Event
Date
2004-08-25T08:53:50Z (22 years ago)
Edited On
2026-04-24T17:49:56Z (6 hours ago)
From
Sergio Campana at INAF-OAB <campana@merate.mi.astro.it>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov>
S. Campana and A. Moretti (INAF-Osservatorio astronomico di Brera) report on
behalf of a larger team:
"We analyzed the second Chandra ACIS-S observation of the XRF040812
(Gotz et
al. 2004, GCN 2640). We carried out spectral analysis of our previous
afterglow candidate (CXOJ162602.3-444349, Campana & Moretti GCN 2649,
see also
Patel et al. GCN 2648, 2655). The source is still very hard with a power law
photon index of 0.9+/-0.6 (fixing the column density to the Galactic
value of
5.3x10^21 cm-2 and using Cash statistics in the XSPEC fit). The spectrum is
slightly softer than in the first observation (Campana & Moretti GCN
2649). The unabsorbed 0.5-10 keV source flux is 9.30x10^-14 erg cm-2 s-1 a
factor of ~3 lower than in the previous Chandra observation. A constant
temporal evolution is not consistent with the data at a ~4.5 sigma level. A
power law decay describes better the temporal evolution with a time decay as
t^-1.4(+/-0.6) (90% confidence level, note that this is different from the
Patel et al. GCN 2655, since we fitted the flux evolution and not the counts
evolution)."
This message can be cited.