Carpet-2 observation of two E>100 TeV photon-like events associated with the IceCube 201120A neutrino alert in the Cygnus Cocoon
ATel #14255; D. Dzhappuev, A. Kudzhaev, V. Petkov, S. Troitsky on behalf of the Carpet-2 group (INR RAS)
on 9 Dec 2020; 12:27 UT
Credential Certification: Sergey Troitsky (st@ms2.inr.ac.ru)
Subjects: VHE, UHE, Neutrinos, Transient
We have recently reported upper limits on the fluence of E>100 TeV photons associated with the IceCube 201120A neutrino alert (GCN #28927) from the Cygnus Cocoon direction, obtained with the Carpet-2 experiment from observations within a 24-hour interval centered at the alert time, see ATel # 14237 for more details. The standard alert follow-up procedure adopted by Carpet-2 also includes the analysis of a 30-day interval; here we report the results of this search. Two E>100 TeV photon candidates have been detected (on November 10 and 26). The total number of photon candidates from this direction observed during the observational run (2018-2020) is six, consistent with no persistent source. Preliminary estimates give the probability of the chance coincidence of order 0.02 and the fluence estimate of (5.5+-2.3) GeV/cm2, consistent with expectations for a flare of a Galactic source producing a single IceCube GOLD neutrino event. More details will be published after further elaborated analysis.
Carpet-2 is an air-shower array at Baksan Neutrino Observatory of the Institute for Nuclear Research of the Russian Academy of Sciences, capable of detecting cosmic gamma rays above 100 TeV (see (Dzhappuev et al. 2020 for the description of neutrino-alert analyses and further references). The Cygnus Cocoon is a star-forming region discussed as a particle acceleration site (see Bykov at al. 2020) and a possible high-energy neutrino source (Yoast-Hull et al. 2017).
