GRB 150103A

L. M. Z. Hagen (PSU), J. R. Cummings (NASA/UMBC),
N. Gehrels (NASA/GSFC), M.E. Gropp (PSU), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA) and M. H. Siegel (PSU) report on behalf
of the Swift Team:

At 20:02:18 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150103A (trigger=623368).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 131.639, -48.890 which is 
   RA(J2000) = 08h 46m 33s
   Dec(J2000) = -48d 53' 24"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single peak about
40 seconds long.  The peak count rate was ~875 counts/sec (15-350 keV), 
at ~5 sec after the trigger. 

The XRT began observing the field at 20:04:29.5 UT, 130.5 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 131.66761, -48.88595 which is
equivalent to:
   RA(J2000)  = 08h 46m 40.23s
   Dec(J2000) = -48d 53' 09.4"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 69 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 8.96
x 10^21 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 135 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the large, but uncertain extinction expected. 

Burst Advocate for this burst is L. M. Z. Hagen (lea.zernow.hagen AT gmail.com). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

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

Using  promptly downlinked XRT event data for GRB 150103A, we find an
enhanced XRT position of the afterglow: RA, Dec: 131.6663, -48.8863
which is equivalent to:
   RA (J2000)  = 08 46 39.92
   Dec (J2000) = -48 53 10.6
with an uncertainty of 2.0 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/623368.

Position enhancement is is described by Goad et al. (2007, A&A, 476,
1401) and Evans et al. (2009, MNRAS, 397, 1177).

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

J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1050 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 150103A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 131.66600, -48.88593 which is equivalent
to:

RA (J2000): 08h 46m 39.84s
Dec (J2000): -48d 53' 09.4"

with an uncertainty of 1.8 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.

A. Klotz, D. Turpin (IRAP-CNRS-OMP), D. Macpherson (UWA/ICRAR), D. 
Coward (UWA),
M. Boer, B. Gendre, K. Siellez, H. Dereli, O. Bardho (UNS-CNRS-OCA),
A. Williams (PO-UWA), R. Martin (PO-UWA) report:

We imaged the field of GRB 150103A detected by SWIFT
(trigger 623368) with the Zadko robotic telescope (D=100cm)
located at the observatory - Gingin, Australia.

The observations started 121.6s after the GRB trigger
(44.7s after the notice). The elevation of the field decreased
from 62 degrees above horizon and weather conditions
were good but during the dawn.

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect any OT in the XRT error box provided by
Osborne et al. (GCNC 17272) with a limiting magnitude of:

t0+121.6s to t0+181.6s : Rlim = 16.7

The second image is 30.0s exposure in tracking mode:

t0+200.0s to t0+230.0s : Rlim = 18.9

The following images give the same limits:
t0+239s to t0+347s : Rlim = 18.9

Images taken later are saturated due to the dawn.

Magnitudes were estimated with the nearby NOMAD1 stars
and are not corrected for galactic dust extinction.

J. R. Cummings, S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
  
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 150103A (trigger #623368) (Hagen, et al.,
GCN Circ. 17269
Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 131.674, -48.896 deg which is
    RA(J2000)  =  08h 46m 41.9s
    Dec(J2000) = -48d 53' 45.2"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 67%.
  
The mask-weighted light curve shows a single broad peak.  T90 (15-350 keV) is
49.1 +- 9.8 sec (estimated error including systematics).
  
The time-averaged spectrum from T+6.06 to T+64.68 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index -0.03 +- 1.01,
and Epeak of 54.2 +- 12.8 keV (chi squared 54.70 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 8.2 +- 1.3 x 10^-07 erg/cm2
and the 1-sec peak flux measured from T+26.32 sec in the 15-150 keV band is
0.5 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.61 +- 0.18 (chi squared 66.38 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level.
  
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/623368/BA/

L. M. Z. Hagen (PSU) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150103A
135 s after the BAT trigger (Hagen et al., GCN Circ. 17269
Loading...
 
 ). No optical
afterglow consistent with the XRT position (Osborne et al. GCN Circ.
17272
Loading...
 
 ) 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 first finding
chart (FC) exposures and subsequent exposures are:

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

white (fc)         135          284          147         >20.49
white              573         7047          618         >21.08
v                  624         6018          293         >19.31
b                  549         6841          471         >20.41
u (fc)             293          543          245         >19.66
u                  698         6635          451         >19.95
uvw1               673         6429          471         >19.73
uvm2               648         6224          471         >19.54
uvw2               599         7179          417         >19.67

The magnitudes in the table are not corrected for the Galactic extinction
due to the large, but uncertain, reddening of E(B-V) = 1.46 in the
direction of the burst (Schlegel et al. 1998).

M.C. Stroh (PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), A.P. Beardmore
(U. Leicester), P.A. Evans (U. Leicester), B.P. Gompertz (U.
Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), M. de Pasquale
(INAF-IASFPA) and L.M.Z. Hagen report on behalf of the Swift-XRT team:

We have analysed 7.8 ks of XRT data for GRB 150103A (Hagen  et al. GCN
Circ. 17269
Loading...
 
 ),  from 116 s to 22.0 ks after the	BAT trigger. The data
comprise 231 s in Windowed Timing (WT) mode (the first 7 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Osborne et
al. (GCN Circ. 17270
Loading...
 
 ).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.65 (+0.27, -1.19), followed by a break at T+416 s to
an alpha of 2.56 (+0.47, -0.27).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.15 (+0.16, -0.15). The
best-fitting absorption column is  1.53 (+0.30, -0.27) x 10^22 cm^-2,
in excess of the Galactic value of 9.0 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.8 (+0.4, -0.3) and
a best-fitting absorption column of 1.9 (+0.6, -0.5) x 10^22 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 6.5 x 10^-11 (1.2 x 10^-10) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.9 (+0.6, -0.5) x 10^22 cm^-2
Galactic foreground: 9.0 x 10^21 cm^-2
Excess significance: 3.3 sigma
Photon index:	     1.8 (+0.4, -0.3)

If the light curve continues to decay with a power-law decay index of
2.56, the count rate at T+24 hours will be 3.0 x 10^-6 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.9 x
10^-16 (3.6 x 10^-16) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00623368.

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

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

E. Gorbovskoy,V. Lipunov, N.Tyurina, P.Balanutsa, D.Denisenko, M.Pruzhinskaya, 
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

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-SAAO  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in South Africa (Sutherland) was pointed to the  GRB150103A 33 
sec after notice time and 115 sec after trigger time at
2015-01-03 20:04:14 UT. On our first 
(20s exposure)  set we haven`t found optical transient  within SWIFT 
error-box (Hagen et al., GCN Circ 17269
Loading...
 
 ; Evans, GCN Circ 17270
Loading...
 
 ; Cummings 
et al., GCN Circ 17274
Loading...
 
 ; Stroh et al., GCN Circ 17277
Loading...
 
 ).

The 5-sigma upper limit has been about 17.0mag

This limit slightly yearly than Zadko (Klotz et al., GCN CIRC 17273
Loading...
 
 ) and 
Swift UVOT (Hagen, GCN CIRC 17275
Loading...
 
 ), but not contradict to them.

This message may be cited.