[vsnet-grb-info 26849] IceCube-201120A in the Cygnus region: No enhanced TeV gamma-ray flux detected by HAWC

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28952
SUBJECT: IceCube-201120A in the Cygnus region: No enhanced TeV gamma-ray flux detected by HAWC
DATE:    20/11/25 03:05:23 GMT
FROM:    Hugo Ayala at Pennsylvania State University  <hgayala at psu.edu>

Hugo Ayala (Penn State) reports on behalf of the HAWC
collaboration (http://www.hawc-observatory.org/collaboration):

On 2020/11/20 09:44:40 UTC, the IceCube collaboration reported a
track-like very-high-energy event  that has a high probability of
being an astrophysical neutrino, IceCube-201120A. Location is at
RA: 307.53 (+ 5.34 - 5.59 deg 90% PSF containment) J2000
Dec: 40.77 (+ 4.97 - 2.80 deg 90% PSF containment) J2000
(GCN circular 28927).

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.

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. This region corresponds to the
Cygnus Cocoon region.
The best position of the IceCube event is close to the HAWC catalog source
3HWC J2031+415 RA 307.93, Dec: 41.51 (±0.06 deg 68% containment) J2000
Significance: 23.56
Flux: 30.7e-15 +1.3e-15 -1.4e-15 [Tev cm2 s]^-1 at 7 TeV
Index: -2.36 ± 0.04

Other 3HWC sources in the region:
3HWC J2020+403 RA 305.16 Dec 40.37 (±0.09 deg 68% containment) J2000
Significance: 9.69
Flux: 11.4e-15 ±1.2e-15  [Tev cm2 s]^-1 at 7 TeV
Index: -3.11 ± 0.07

3HWC J2022+431 RA 305.522 Dec: 43.158 (±0.10 deg 68% containment) J2000
Significance: 28.95
Flux: 6.0e-15 ±1.1e-15  [Tev cm2 s]^-1 at 7 TeV
Index: -2.34 ± 0.12

3HWC J2043+443 RA 310.89 Dec: 44.30 (±0.24 deg 68% containment) J2000
Significance: 5.35
 Flux: 9.7e-15 +2.1e-15 -2.2e-15 [Tev cm2 s]^-1 at 7 TeV
Index: -2.33 +0.14 -0.15

Search for a transient source. We assume a power-law spectrum with an index
of -2.3
with pivot energy of 1 TeV.

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 2020/11/20 01:52:08 UTC and ended
2020/11/22 02:06:34 UTC.

We found 4 hotspots in the region of the IceCube uncertainty.
3 of them are consistent with 3HWC sources. One is not.

|  RA  | Dec | Unc. |p-value|Flux [TeV^-1 cm^-2 s^-1]|Nearby source|
|------|-----|-----|------|------------------------------|---------|
|305.2|40.0|0.4| 0.20 |7.9e-12 (+8.0e-12 -5.2e-12)|3HWC J2020+403|
|309.0|40.4|0.2| 0.25 |7.2e-12 (+8.3e-12 -5.1e-12)|None|
|305.1|43.0|0.3| 0.84 |4.5e-12 (+7.1e-12 -3.6e-12)|3HWC J2020+431|
|307.6|41.4|0.7| 0.91 |7.7e-12 (+9.1e-12 -5.8e-12)|3HWC J2031+415|

Position and uncertainty (68%) are in degrees.
P-values are post-trials. None of the hotspots is a significant detection,
nor we see any significant flux enhancements.

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.