GRB 190828A

S. Sugita,  H. Nishida, M. Serino (AGU), H. Negoro (Nihon U.), K.
Asakura (Osaka U.),
M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.),
T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN),
T. Sakamoto, A. Yoshida (AGU),
W. Iwakiri, Y. Tsuboi,  R. Sasaki, H. Kawai, T. Sato (Chuo U.),
M. Shidatsu (Ehime U.),
N. Kawai, M. Sugizaki, M. Oeda, K. Shiraishi (Tokyo Tech),
S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, N.Isobe, R.
Shimomukai, M. Tominaga (JAXA),
Y. Ueda, A. Tanimoto, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake
(Kyoto U.),
H. Tsunemi, T. Yoneyama, S. Ide (Osaka U.),
M. Yamauchi, S. Iwahori, Y. Kurihara, K. Kurogi, K. Miike (Miyazaki U.),
T. Kawamuro (NAOJ),
K. Yamaoka (Nagoya U.),
Y. Kawakubo (LSU)
report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray
transient source at 07:58:01 UT on 2019 August 28.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (58.011 deg, 46.448 deg) = (03 52 02, +46 26 52)  (J2000)
with a 90% C.L. statistical error of 0.25 deg and an additional
systematic uncertainty of 0.1 deg (90% containment radius).

Without assumptions on the source constancy, we obtain a rectangular error
box for the transient source with the following corners:
(56.303, 46.041) deg = (03 45 12, +46 02 27) (J2000)
(56.644, 45.605) deg = (03 46 34, +45 36 17) (J2000)
(60.044, 46.816) deg = (04 00 10, +46 48 57) (J2000)
(59.724, 47.262) deg = (03 58 53, +47 15 43) (J2000)

The X-ray flux averaged over the scan was 193 +- 27 mCrab
(4.0-10.0keV, 1 sigma error).

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a series of observations, tiled on the sky, of the
MAXI GRB 190828A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00086

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the MAXI event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.

J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U.
Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi  (INAF-IASFPA) , M.
Capalbi (INAF-IASFPA), B. Sbarufatti (PSU), D.N. Burrows (PSU) and P.A.
Evans (U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the MAXI-detected
burst GRB 190828A (Sugita et al. GCN Circ. 25502
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 ) in a series of
observations tiled on the sky. The total exposure time is 1.3 ks,
distributed over 7 tiles; the maximum exposure at a single sky location
was 393 s. The data were collected between T0+48.4 ks and T0+49.8 ks,
and are entirely in Photon Counting (PC) mode. 

No X-ray sources have been detected. The 3-sigma upper limit in the
field (not including the regions where the tiles overlap) ranges from
~0.02 to ~0.15 ct s^-1, corresponding to a 0.3-10 keV observed flux of
9.9e-13 to 5.8e-12 erg cm^-2 s^-1 (assuming a typical GRB spectrum).

The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00086.

This circular is an official product of the Swift-XRT team.