GRB 261012A

S. Yatsuzuka (Ehime U.) H. Negoro, M. Nakajima, K. Saito, T. Yokoyama, M. Wada (Nihon U.),
T. Mihara, A. Aoyama, M. Ota, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN),
T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, H. Hiramatsu, T. Kato, A. Yoshida (AGU),
Y. Tsuboi, Y. Ishihara, H. Ogaki (Chuo U.),
M. Shidatsu, C. Kang, M. Uenishi, T. Usuki, H. Aoe (Ehime U.),
I. Takahashi, Y. Yatsu (Science Tokyo),
S. Nakahira, S. Ueno, H. Tomida, M. Kurihara (JAXA),
Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.),
M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.),
K. Yamaoka (Nagoya U.),
M. Sugizaki (Kanazawa U.),
W. Iwakiri (Chiba U.),
T. Kawamuro (Osaka U.),
S. Yamada (Tohoku U),
S. Ogawa (TUS)

The MAXI/GSC nova alert system triggered a bright uncatalogued 
X-ray transient source at 05:36:19 UT on 12 October 2026.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (297.193 deg, -36.587 deg) = (19 48 46, -36 35 14) (J2000)
with a 90% C.L. statistical error of 0.32 deg and an additional 
systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 245 +- 43 mCrab
(4.0-10.0keV, 1 sigma error).
Without assumptions on the source constancy, we obtain a rectangular error
box for the transient source with the following corners:
(R.A., Dec) = (297.452, -37.121) deg = (19 49 48, -37 07 15) (J2000)
(R.A., Dec) = (297.946, -36.618) deg = (19 51 47, -36 37 04) (J2000)
(R.A., Dec) = (296.663, -35.796) deg = (19 46 39, -35 47 45) (J2000)
(R.A., Dec) = (296.166, -36.294) deg = (19 44 39, -36 17 38) (J2000)

There was no significant excess flux in the previous transit at 04:03 UT
and in the next transit at 07:09 UT with an upper limit of 20 mCrab for each.