TITLE:   GCN CIRCULAR
NUMBER:  28895
SUBJECT: Swift XRT observations of the Fermi-LAT source 4FGL J0658.6+0636, positionally consistent with the IceCube high-energy neutrino alert
DATE:    20/11/15 18:59:37 GMT
FROM:    Marcos Santander at U. Alabama/IceCube  <jmsantander@ua.edu>

Authors: S. Buson (Univ. Würzburg), M. Santander (Univ. Alabama), S. Garrappa (DESY-Zeuthen), R. Sharpe (Univ. Alabama) and P. Lynch (Univ. Alabama)

The Neil Gehrels Swift Observatory observed the field of the Fermi-LAT catalogued source  4FGL J0658.6+0636 positionally coincident with the ICECUBE_Astrotrack_Gold astrophysical neutrino candidate event IceCube-201114A (GCN 28887) starting on 2020 November 15 at 08:20:41 UT, about 16 hours after the neutrino detection.

Analysing the Neil Gehrels Swift Observatory X-ray Telescope (XRT) data quasi-simultaneous to the IceCube-201114A arrival, we detect 4FGL J0658.6+06361 with an unabsorbed X-ray flux of 9.76 (-1.49, +2.39) × 10-11 erg cm-2 s-1 (0.3-10 keV). A spectrum constructed from these data can be well described by an absorbed power law with N_H= 2.94×10^21 cm-2 (wilm abundances, vern cross-sections), and a photon index of 2.25 +/- 0.25. This is an elevated state for the source (~26 cts/ks) compared to archival observations from May 2012 when the source was observed at ~10 cts/ks.

We will continue monitoring the source over the coming days, multiwavelength observations of the source are encouraged.

We wish to thank the Swift Team for making these observations possible, in particular K.L. Page as the Swift Observatory Duty Scientist and Brad Cenko for approving these observations, which are part of Swift GI program 1619170.