Abstract:
IceCube-170922A was an EHE neutrino event (GCN/AMON NOTICE 2016) identified and distributed by the IceCube Observatory via AMON and GCN within δt~43s of its detection at 20:54:30 UT on 2017 September 22 (GCN/AMON NOTICE IceCube-170922A 2017ApJ...843..109G). A refined localization was reported four hours later (Kopper & Blaufuss 2017GCN.21916....1K): RAJ2000=77.43
-0.8+1.3°, DEJ2000=+5.72
-0.4+0.7° (90% containment ellipse).
IceCube-170922A triggered the Neil Gehrels Swift Observatory in automated fashion via AMON cyberinfrastructure, resulting in rapid-response mosaic-type follow-up observations, covering a roughly circular region of sky centered on the prompt localization in a 19-point tiling that began 3.25hr after the neutrino detection. This initial epoch of Swift observations spanned 22.5hr and accumulated ~800s exposure per pointing. The mosaic tiling yielded coverage of a region with radius ~0.8° centered on RAJ2000=05:09:08.784, DEJ2000=+05:45:13.32, amounting to a sky area of 2.1deg
2.
Source 2 from these observations (marked as X2 on Figure 1), located 4.6' from the center of the neutrino localization, was identified by us as the likely X-ray counterpart to QSO J0509+0541, also known as TXS 0506+056. This was the first report to connect TXS 0506+056 to IceCube-170922A (Keivani+ 2017GCN.21930....1K).
Following the Fermi report that TXS 0506+056 was in a rare GeV-flaring state (Tanaka+ 2017ATel10791....1T), we commenced a Swift monitoring campaign on September 27 (Evans+ 2017ATel10792....1E). Swift monitored TXS 0506+056 for 36 epochs by November 30 with 53.7ks total exposure time (Table 1).
The Swift-UVOT also participated in the rapid-response follow-up observations of the IceCube-170922A and the subsequent monitoring of the flaring blazar TXS 0506+056.
(2 data files).
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