GRB 150123A

K. Fukushima, H. Negoro (Nihon U.), M. Serino (RIKEN), S. Nakahira (JAXA),
S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA),
T. Mihara, M. Sugizaki, M. Morii, J. Sugimoto, T. Takagi, A. Yoshikawa, M. Matsuoka (RIKEN),
N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech),
A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU),
H. Tsunemi, D. Uchida (Osaka U.),
M. Nakajima, T. Onodera, K. Suzuki, T. Namba, M. Fujita, F. Honda (Nihon U.),
Y. Ueda, M. Shidatsu, T. Kawamuro, T. Hori (Kyoto U.),
Y. Tsuboi, A. Kawagoe (Chuo U.),
M. Yamauchi, Y. Morooka, D. Itoh (Miyazaki U.),
K. Yamaoka (Nagoya U.)
report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 15:01:50 UT .
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (111.560 deg, -9.691 deg) = (07 26 14, -09 41 27) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.14 deg and 0.13 deg respectively.
The roll angle of long axis from the north direction is 110.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 332 +- 36 mCrab
(4-10keV, 1 sigma error).
There was no significant excess flux in the previous transit at UT 13:29
and in the next transit at 16:34 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 150123A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00038

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; and 2009, MNRAS, 397, 1177).

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

A. Melandri, P. D'Avanzo, M.G. Bernardini (INAF-OAB) & P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has observed the error circle of the MAXI GRB 150123A in a series of observations tiled on the sky. The total exposure time is 3.7 ks spread over 4 fields; the maximum exposure within the sky observed was 1.6 ks. The observations started 9.8 ks after the MAXI trigger. 

Within these data there are 3 objects which are not catalogued in the X-rays.

Source details:

Source 1
RA:  111.36420 = 07h 25m 27.41s (J2000)
Dec:  -9.74880	 = -09d 44' 55.7" (J2000)
Err: 5.9 (radius, 90% confidence)
Exposure time: 814 s
Online products:
http://www.swift.ac.uk/xrt_products/TILED_GRB00038/index_1.php

Source 2
RA:  111.52056 = 07h 26m 4.93s (J2000)
Dec:  -9.65269	 = -09d 39' 09.7" (J2000)
Err: 4.4 (radius, 90% confidence)
Exposure time: 1.3 ks
Online products:
http://www.swift.ac.uk/xrt_products/TILED_GRB00038/index_2.php

Source 3
RA:  111.40659 = 07h 25m 37.58s (J2000)
Dec:  -9.55462	 = -09d 33' 16.6" (J2000)
Err: 5.2 (radius, 90% confidence)
Exposure time: 1.5 ks
Online products:
http://www.swift.ac.uk/xrt_products/TILED_GRB00038/index_3.php


Source #1 is located 3" from an optical source present in the USNO-B1.0 catalogue with a magnitude of R=15.5. Source #2 is located 4" from an optical source present in the USNO-B1.0 catalogue with a magnitude of R=18.0. Source #3 matches the position of the known bright star TYC 5400-1552-1 (R=10.8). 

At the present time we cannot be sure which, if any, of these is the afterglow.

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

S. R. Oates (IAA-CSIC/UCL-MSSL) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of MAXI GRB 150123A
8.7ks after the trigger. No optical afterglow is detected within the MAXI 
error circle (Fukushima, GCN Circ. No. 17345). Using the UVOT photometric 
system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) We obtain a typical 
3 sigma upper limit of >20.6 in the u filter. This magnitude has not been corrected 
for the Galactic extinction due to the reddening of E(B-V) = 0.04 in the direction 
of the burst (Schlegel et al. 1998).

In the error circles for XRT candidates #1, #2, and #3 we note the presence of objects 
that are catalogued in the USNO-B1, as discussed in Melandri et al. (GCN Circ. No. 17348). 
At the present time we cannot determine if any of these objects are fading.

S. Golenetskii, R.Aptekar, V. Pal'shin, D. Frederiks, P. Oleynik,
M.Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind
team report:

The long GRB 150123A localized by MAXI/GSC (Fukushima et al., GCN
17345
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 ) was detected by Konus-Wind in the waiting mode.

The burst light curve shows a single pulse started at ~T0(MAXI)-39 s 
with a duration of ~70 s.

As observed by Konus-Wind, the burst had a fluence of
7.42(-0.80,+0.88)x10^-6 erg/cm2 and a 2.944-s peak flux,
measured from ~T0(MAXI)-1 s, of (1.6 +/- 0.7)x10^-7 erg/cm2 (both in the 
20 - 1200 keV energy range).

Fitting the K-W 3-channel time-integrated spectrum (from T0(MAXI)-39 s 
to T0(MAXI)+31 s) by a simple power-law model yields a power law index 
of 1.82 +/- 0.1 (chi2=1.0/1 dof).

All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.

The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB150123A/

E. Gorbovskoy, V. Lipunov,  N.Tyurina, P.Balanutsa, D.Denisenko,
A.Kuznetsov, V.Kornilov, D.Kuvshinov
Lomonosov Moscow State University,
Sternberg Astronomical Institute

O.Gres, K.Ivanov,  S.Yazev, N.M.Budnev,  V.A.Poleshchuk
Irkutsk State University

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov
Blagoveschensk Educational State University


A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory

V.Krushinsky, I.Zalozhnih,  A. Popov
Ural Federal University, Kourovka

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

H. Levato and C. Saffe
Instituto de Ciencias Astronomicas de la Tierra y del Espacio (ICATE),
San Juan, Argentina

C. Mallamacci, C. Lopez and F. Podest
Observatorio Astronomico Felix Aguilar (OAFA), San Juan National University, 
Argentina


MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Tunka, Kislovodsk and SAAO made inspection inside MAXI 
GRB150123A  (Fukushima et. al GCN 17345
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 ) error box  which starting 3297 
sec after trigger time at 2015-01-23 15:56:47 UT. We don't find creadible 
OT candidate in MAXI error box  on single and coadd images with following 
upper limits.

T_start  T-Tmid   Exp  Site Coadd Mlimit  Comment
15:56:47   3297   180 Tunka    --   15.0  High clouds
15:56:55   3305   180 Kilov    --   17.0  5 images only
16:28:50   6562  1800 Tunka    10   19.0
17:14:03   8974  1800 Tunka    10   19.0
18:44:04  13186   180 SAAO     --   18.5  Starting after sunset.
18:44:04  14398  1620 SAAO      9   20.6
19:20:41  17075  1800 SAAO     10   20.6

We also check all Swift-XRT transints (Melandri et. al. GCN 17348
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 ) on all 
out images.
Source #1 is a galaxy with no avidance for brightening.
Source #2 empty space with no OT and known stars at edge of error circle
Source #3 position is blended by close bright stars.



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