GRB 130407A

K. Fukushima, M. Nakajima, H. Negoro (Nihon U.), M. Serino (RIKEN), 
S. Ueno, H. Tomida, S. Nakahira, M. Kimura, M. Ishikawa (JAXA), 
T. Mihara, M. Sugizaki, M. Morii, T. Yamamoto, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), 
N. Kawai, R. Usui, K. Ishikawa, T. Yoshii (Tokyo Tech), 
A. Yoshida, T. Sakamoto, Y. Nakano (AGU), 
H. Tsunemi, M. Sasaki (Osaka U.), 
T. Onodera, K. Suzuki (Nihon U.), 
Y. Ueda, M. Shidatsu, T. Kawamuro (Kyoto U.), 
Y. Tsuboi, M. Higa (Chuo U.), 
M. Yamauchi, K. Yoshidome, Y. Ogawa, H. Yamada (Miyazaki U.), 
K. Yamaoka (Nagoya U.) report on behalf of the MAXI team

At 2013-04-07T23:37:01 UT, the MAXI/GSC nova alert system triggered on 
a bright uncatalogued X-ray transient source.
The transient emission started at and lasted at least 25 seconds
within the 41 second long triangular transit response of
MAXI/GSC. We identify this event as GRB 130407A.

Assuming that the source flux was constant over the transit,
we obtain the source position at

 (R.A., Dec) = (248.10 deg, 10.51 deg) = (16 32 23, +10 30 39) (J2000)

with a 90% C.L. statistical error of 0.2 deg and an additional systematic 
uncertainty of 0.1 deg (90% containment radius). The 4-10 keV flux was 
170 +- 30 mCrab.

There was no significant excess flux in the previous transit at 22:04UT 
and in the next transit at 4/8 01:10 UT with an upper limit of 20 mCrab for each.

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 130407A. Automated analysis of the XRT data will
be presented online at
http://www.swift.ac.uk/xrt_products/TILED_GRB00014

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website. 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; and 2009, MNRAS, 397, 1177).

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

C. Pagani (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the Swift XRT team:

Swift performed 4 tiled observations of the MAXI detected GRB 130407A (Fukushima et al., GCN 14359
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 ) to cover the MAXI error circle. The data are all in Photon Counting (PC) mode. No bright X-ray afterglow is detected in the XRT observations.

The 3sigma upper limit is 1.1 x 10^-2  cts/s. This corresponds to an observed 0.3-10 keV flux of 3.7 x 10^-13  erg/cm2/s, assuming a typical GRB spectrum with photon spectral index of 2. If we consider the Galactic absorption in this direction (4.9 x 10^20  cm^-2; Kalberla et al. 2005) this corresponds to an unabsorbed flux of 4.3 x 10^-13  erg/cm2/s.

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