GRB 150110C

GRB 150110C: MAXI/GSC detection

S. Nakahira (JAXA), H. Negoro (Nihon U.),  S. Ueno, H. Tomida, 
M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), 
T. Mihara, M. Sugizaki, M. Serino, M. Morii, J. Sugimoto, T. Takagi, A. Yoshikawa, 
M. Matsuoka (RIKEN), N. Kawai, Y. Tachibana, T. Yoshii (Tokyo Tech), 
A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), 
H. Tsunemi, D. Uchida (Osaka U.), M. Nakajima, K. Fukushima, T. Onodera, 
K. Suzuki, M. Fujita, F. Honda, T. Namba (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 hard X-ray 
transient source at UT2015-01-10T23:41:01.

Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (68.576 deg, -16.869 deg) = (04 34 18, -16 52 08) (J2000) 
with a statistical 90% C.L. elliptical error region 
with long and short radii of 0.19 deg and 0.17 deg respectively. 
The roll angle of long axis from the north direction is 165.0 deg 
counterclockwise. There is an additional systematic uncertainty of 0.1 deg 
(90% containment radius).
The X-ray flux averaged over the scan was 281 +- 32 mCrab (4-10keV, 1 sigma 
error).
There was no significant excess flux in the previous transit at UT 22:08 
with an upper limit of 20 mCrab.

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 150110C. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00037

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.

K.L. Page (U. Leicester) reports on behalf of the Swift-XRT team:

Swift-XRT has observed the error circle of the MAXI GRB 150110C in a
series of observations tiled on the sky. The total exposure time is
3.8 ks spread over 4 fields; the maximum exposure within the sky observed
was 2.4 ks. The observations started 54.2 ks after the MAXI trigger.
Within these data we detect an uncatalogued X-ray source at RA, Dec =
68.48007, -16.96802 which is equivalent to:
  RA (J2000.0)	= 04h 33m 55.22s
  Dec (J2000.0) = -16d 58' 04.9"
with an uncertainty of 7.0 arcsec (radius, 90% confidence). The source has
a mean X-ray (0.3-10 keV) count rate of 4.0 (+/- 2.2) x 10^-3 count s^-1.
The exposure at this location was 1.5 ks. At the present time we cannot be
sure whether or not this source is the afterglow.

The results of the automatic processing for this source are available
at http://www.swift.ac.uk/xrt_products/TILED_GRB00037/index_1.php
This circular is an official product of the Swift-XRT team.

Paul Kuin (MSSL/UCL) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of MAXI GRB 150110C
54ks after the trigger.  No optical afterglow consistent with the XRT
position
(Page, GCN Circ. No. 17301)  is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures
are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

u                54238        59786         1896         >20.9

The magnitudes in the table are not 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).