ANTARES neutrino detection and possible Swift X-ray counterpart

ATel #7987; D. Dornic (CPPM), S. Basa (LAM), P. A. Evans (U. Leicester), J. A. Kennea (PSU), J. P. Osborne (U. Leicester) and V. Lipunov (MSU)
on 3 Sep 2015; 12:18 UT
Credential Certification: Phil Evans (pae9@star.le.ac.uk)

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On September 1st, 2015, at 07:38:25 UT, ANTARES has detected a bright neutrino at a location of:

   RA(J2000) = 16h 25m 42s
   DEC (J2000) = -27d 23m 24s
with an uncertainty of 18 arcmin (radius, 50% containment)

A target of opportunity alert has been sent immediately to Swift. The XRT onboard Swift followed the ANTARES error box 10 hours after the neutrino detection. An uncatalogued X-ray source has been detected above the limit of RASS, with the flux varying between 5e-13 and 1.4e-12 erg cm^-2 s^-1 (0.3-10 keV), at location:

   RA(J2000) = 16h 26m 2.12s
   DEC (J2000) = -27d 18m 14.8s

with an uncertainty of 2.4 arcsec (radius, 90% containment).

The detected X-ray source seems to be variable. By contrast no transient source in the visible domain with MASTER SAAO has been observed so far until the magnitude 18.5 with a galactic extinction of 2 (Schlegel et al). Further Swift observations have been planned.

We encourage strongly further multi-wavelength observations to identify this X-ray source.