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GCN Circular 27121

Subject
LIGO/Virgo (S200213t/IceCube neutrino candidate: No counterpart candidates in the Swift-XRT Observations
Date
2020-02-18T10:08:35Z (4 years ago)
From
Stefan Countryman at ICECUBE/Columbia U <stc2117@columbia.edu>
S. Countryman (Columbia U.), P. A. Evans (U. Leicester), A. Tohuvavohu
(PSU), A. Keivani (Columbia U.),  J. A. Kennea (PSU), Z. Marka
(Columbia U.), S. Marka (Columbia U.), I. Bartos (U. Florida), D. B.
Fox (PSU), N.J. Klingler (PSU)

The Neil Gehrels Swift Observatory observed the field of the IceCube
track-like muon neutrino candidate (RA, Dec = 45.21d, 31.74d; GCN
#27043) consistent with the sky localization of gravitational-wave
candidate S200213t (GCN #27042) covering ~0.5 sq degrees in 7 tiles to
cover the most probable regions of the joint GW and neutrino
localization (90%-containment radius: 0.4d).  The observations started
at 09:54 UT on February 13th and ended at 10:26 UT on February 13th,
2020, and the typical sensitivity was 2e-13 erg cm^-2 s^-1 (0.3-10
keV).

In total we found 3 "good" X-ray sources, all of which were classified
as "rank 3", i.e. uncatalogued in X-rays, but with fluxes below
historical upper limits. 2 further rank 3 sources were found with
detection flag of "poor", indicating that they are likely spurious.
Details of the good sources are:

| Source ID    | RA             | Dec            | Err90  | Flux*   |
|  S200213t_X2 | 03h 01m 23.65s | +31d 42' 02.3" |   5.8" | 7.9e-13 |
|  S200213t_X4 | 02h 59m 58.48s | +31d 28' 17.1" |   7.1" | 2.2e-13 |
|  S200213t_X6 | 03h 00m 16.09s | +31d 58' 48.9" |   4.7" | 2.3e-13 |

(* 0.3-10 keV, erg cm^-2 s^-1, assuming a power-law spectrum with
photon index of 1.7 and NH=3e20cm^-2).

Full details of all sources are available at:
https://www.swift.ac.uk/LVC/S200213t/
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