[vsnet-grb-info 26434] IceCube-200926B: No significant detection in HAWC

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28534
SUBJECT: IceCube-200926B: No significant detection in HAWC
DATE:    20/09/30 15:04:32 GMT
FROM:    Alberto Carraminana at AzTEC  <alberto at inaoep.mx>

Alberto Carramiñana (INAOE) reports on behalf of the HAWC 
collaboration (http://www.hawc-observatory.org/collaboration):

On 2020/09/26 22:35:29 UTC, the IceCube collaboration reported a 
track-like very-high-energy event  that has a moderate probability of 
being an astrophysical neutrino, IceCube-200926B. Location is at 
RA: 184.75 (+3.64/-1.55 deg  90% PSF containment) J2000
Dec: 32.93 (+1.15/-0.91 deg 90% PSF containment) J2000  
(GCN circular 28509).

We performed two types of analyses for the follow-up. The first is for a 
steady source in archival data and the second is a search for a transient 
source. We assume a power-law spectrum with an index of -2.3 for both 
analyses. 

- Search for a steady source in archival data:

The archival data spans from November 2014 to June 2019. We searched
inside the reported IceCube error region. 

The most significant location, with p-value 2.72e-03 (1.38e-01 post-trials), 
is at RA 185.24 deg, Dec +32.58 deg (±0.16 deg 68% containment) J2000. 
We set a time-integrated 95% CL  upper limit on gamma rays at the 
maximum position of:

E^2 dN/dE = 2.78e-13 (E/TeV)^-0.3 TeV.cm^-2.s^-1

- Search for a transient source. 

Since the event was not in our field of view at the time reported,
we report the combined result for the transits before and after the
IceCube event.

Data acquisition started on 2020/09/25 21:30:27 UTC and ended
2020/09/27 21:45:47 UTC.
The most significant location, with p-value 1.66e-02 (5.98e-01 post-trials),
is at RA 185.45 deg, Dec +32.49 deg (±0.20 deg 68% containment) J2000.
We set a time-integrated 95% CL upper limit at the position of 
maximum significance of:

E^2 dN/dE = 7.79e-12 (E/TeV)^-0.3 TeV.cm^-2.s^-1

HAWC is a very-high-energy gamma-ray observatory operating in Central 
Mexico at latitude 19 deg. north. Operating day and night with over 
95% duty cycle, HAWC has an instantaneous field of view of 2 sr and 
surveys 2/3 of the sky every day. It is sensitive to gamma rays from 
300 GeV to 100 TeV.