@article {21701, title = {VizieR Online Data Catalog: Swift follow-up obs. of the TXS 0506+056 blazar (Keivani+, 2018)}, year = {2019}, month = {2019/08/1}, pages = {J/ApJ/864/84}, 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{\textdegree}, DEJ2000=+5.72-0.4+0.7{\textdegree} (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{\textdegree} centered on RAJ2000=05:09:08.784, DEJ2000=+05:45:13.32, amounting to a sky area of 2.1deg2.

Source 2 from these observations (marked as X2 on Figure 1), located 4.6{\textquoteright} 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).}, keywords = {BL Lac objects, Photometry: UBV, Ultraviolet, X-ray sources}, url = {https://ui.adsabs.harvard.edu/abs/2019yCat..18640084K}, author = {Keivani, A. and Murase, K. and Petropoulou, M. and Fox, D. B. and Cenko, S. B. and Chaty, S. and Coleiro, A. and Delaunay, J. J. and Dimitrakoudis, S. and Evans, P. A. and Kennea, J. A. and Marshall, F. E. and Mastichiadis, A. and Osborne, J. P. and Santander, M. and Tohuvavohu, A. and Turley, C. F.} }