NICER observations of 4FGL J0658.6+0636, candidate counterpart to the IceCube neutrino event IceCube-201114A
ATel #14202; Dheeraj Pasham (MIT), Keith Gendreau, Zaven Arzoumanian (NASA/GSFC), Sara Buson (Univ. Wuerzburg), Marcos Santander (Univ. Alabama)
on 20 Nov 2020; 02:59 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Dheeraj Pasham (drreddy@mit.edu)
Subjects: X-ray, Gamma Ray, Neutrinos, Transient
Referred to by ATel #: 14225
The Fermi-LAT catalogued source 4FGL J0658.6+0636 (4FGL) is located 0.81 degrees away from the best-fit sky position of the IceCube neutrino event IC201114A and within the neutrino 90% localization region. IC201114A was detected on 14 November 2020 at 15:05:31.96 UT (T0; GCN#28887). Swift/XRT observed 4FGL J0658.6+0636 roughly 16 hours after the IceCube alert and found a flux enhancement by a factor of 2.6 compared to archival data from May 2012 (ATel#14178). Following the Swift/XRT detection, NICER observed this field of view and accumulated over 12 ks of clean exposure between 2020-11-15 22:35:40 (T0+31.5 hrs) and 2020-11-18 05:09:00 (T0+86 hrs).
4FGL J0658.6+0636 is detected above the background between 0.5-2 keV. We fit the summed NICER X-ray spectrum in this energy range with a power-law modified by absorption (tbabs*pow in Xspec). The best-fit power-law index and absorbing column are 2.9 +/-0.6 and (0.31 +/-0.1) x 10^22 cm^-2. These values are consistent with XRT measurements from T0+16 hours. The mean NICER 0.3-10 keV unabsorbed and absorbed flux estimates are 1.5e-12 erg/s/cm^2 and 5e-13 erg/s/cm^2, respectively. The unabsorbed flux value is consistent with archival eROSITA measurements from April 2020 and October 2020, and also with XRT measurements from T0+16 hrs (ATel#14201).
Coordinated radio (eMERLIN) and NICER observations are planned and multi-wavelength observations are encouraged.
NICER carries out prompt follow-up observations of X-ray-bright extragalactic transients and tracks alerts from LIGO/VIRGO. NICER is a 0.2-12 keV X-ray telescope operating on the International Space Station. The NICER mission and portions of the NICER science team activities are funded by NASA.
