TITLE:   GCN CIRCULAR
NUMBER:  28756
SUBJECT: IceCube-201021A: Optical counterpart of WISEA J172314.13+142101.5
DATE:    20/10/23 08:08:26 GMT
FROM:    Myungshin Im at Seoul Nat U  <mim@astro.snu.ac.kr>

Myungshin Im, Gregory S. Paek, Gu Lim, Sungyong Hwang (CEOU/SNU) and H.-I.
Sung (KASI), on behalf of a larger collaboration

Using the LOAO 1m telescope at Mt. Lemmon, Arizona, USA, we observed the
field centered on WISEA J172314.13+142101.5, an IR source suggested as a
possible counterpart of the gamma ray source Fermi J1725.5+1312 (Buson et
al., GCN 28751). Note that  Fermi J1725.5+1312 is a new gamma ray source
that appeared recently within the 90% localization of the neutrino event,
IC201021A (IceCube collaboration, GCN 28715). The observation started at
2020-10-23 01:51:54 (UT). The images were taken in R-band with on-source
integration time of 27 min.

We find an optical counterpart of WISEA J172314.13+142101.5 near the
detection limit of the stacked LOAO image with a tentative magnitude of
R=21.0 +- 0.3 AB mag. The PS1 DR2 archive (Chambers, K. C. et al.) shows
that this source has a mean magnitude of r=21.22 +- 0.04 AB mag (PSF
magnitude). Examination of the PS1 data also shows the variability of this
object at the level of a few tenths of magnitude in the past. Our result
indicates that the object has not brightened significantly (<0.2 mag)
compared to the historic mean. A deeper observation is desirable to better
constrain the current optical variability state of this source.

We thank the staff of LOAO, Jaehyuk Yoon, for performing the observation.