GRB 150203A

D. Kawamura, T. Sakamoto, A. Yoshida (AGU) 

We observed the field of GRB 150203A detected by Swift (trigger #629578; 
Ukwatta et al., GCN Circ. 17377
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 ) with the iTelescope.Net (http://www.itelescope.net) 
T11 (0.50 m Plane Wave) telescope located at the New Mexico Skies Observatory (NM, USA). 
20 images of 60 sec exposures were taken in the R filter starting from February 3 
4:22:11 (UT) about 13.3 minutes after the trigger and stopped on February 3 4:47:29 (UT).  
We do not detect the optical afterglow both in the individual images and the stacked 
image at the enhanced X-ray afterglow position (Evans et al., GCN Circ. 17378
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 ).  
The estimated five sigma upper limit of the combined image (total exposure of 1200 sec) 
is ~18.9 using the USNO-B1 catalog.

T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (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),
(i.e. the Swift-BAT team):

Using the data set from T-120 to T+1190 sec from the
recent telemetry downlink, we report further analysis of
BAT GRB GRB 150203A (trigger #629578) (Ukwatta, et al.,
GCN Circ. 17377
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 ).The BAT ground-calculated position is
RA, Dec = 98.394, 6.952 deg which is
   RA(J2000)  =  06h 33m 34.5s
   Dec(J2000) = +06d 57' 07.1"
with an uncertainty of 1.1 arcmin, (radius, sys+stat,
90% containment). The partial coding was 84%.

BAT light curve shows a single multi-peaked episode starting
around T-2 sec, and ending around T+32 sec. The two main
peaks of the light curve can be seen at T+1 sec and T+18 sec.
T90 (15-350 keV) is 25.8 +- 5.0 sec (estimated error
including systematics).

The time-averaged spectrum from T-0.8 to T+32.3 sec
is best fit by a simple power-law model.  The power law
index of the time-averaged spectrum is 1.90 +- 0.12.
The fluence in the 15-150 keV band is 9.1 +- 0.6 x 10^-07
erg/cm2. The 1-sec peak photon flux measured from T+16.79
sec in the 15-150 keV band is 0.9 +- 0.1 ph/cm2/sec.
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/629578/BA/

J. Wren, W.T. Vestrand, P. Wozniak, and H. Davis,
of Los Alamos National Laboratory report:

The RAPTOR network of robotic optical telescopes made observations of Swift trigger 629578 (Ukwatta, et al., GCN 17377
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 ).  Our narrow-field instruments located in Los Alamos, NM, USA, arrived on target 4.6 s after receipt of the notice (T+30.9 s after the BAT trigger time).  No optical counterpart is detected within the Swift XRT counterpart location.  Typical 3-sigma limiting magnitudes for our initial 5 s exposures were R~16.6 and I~15.7 based on comparision to the USNO-B1 R-band catalog.

The burst location was also within the field of view of our wide-field sky monitors during the gamma-ray emitting interval.  No optical counterpart is detected in any of our wide-field monitor images.  Typical 3-sigma unfiltered limiting magnitudes during this period were V~9.7 based on comparison to the
Tycho-2 V-band catalog.

M. M. Chester (PSU) and T. N. Ukwatta (LANL) report on behalf of the 
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150203A
83 s after the BAT trigger (Ukwatta et al., GCN Circ. 17377
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 ).
No optical afterglow consistent with the enhanced XRT position 
(Evans et al. GCN Circ. 17384
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 ) 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         83         232         147     >20.6
white            83        1197         353     >21.2 
v               624        1246          78     >18.7
b               550        1172          58     >19.4
u_FC            295         545         246     >20.0
u               295        1148         285     >20.0
w1              674        1278          61     >18.8
m2              649        1271          78     >18.7
w2              600        1222          78     >19.0

The magnitudes in the table are not corrected for the large Galactic 
extinction in the direction of the burst (reddening of E(B-V) = 0.9; 
Schlegel et al. 1998).

L. Elenin (KIAM),  A. Volnova (IKI), E. Mazaeva (IKI),  I. Molotov  (KIAM), 
A. Pozanenko (IKI) report on behalf of larger GRB  follow-up  collaboration:

We observed the field of the Swift GRB 150203A (Ukwatta et al., GCN 17377
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 ) 
with 0.4-m telescope of ISON-NM observatory in robotic mode starting on 
Feb., 03 (UT) 04:10:19  i.e. 72 seconds after burst trigger. We obtained 60 
unfiltered images of 30 s exposure. We do not detect any source within 
enhanced XRT error circle (Evans et al., GCN 17384
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 ):

Date          UT start   t-T0             Exp.    Filter   UL (3sigma)
                               (mid.,days)    (s)
2014-02-03 04:10:19  0.00130       2*30    Clear   18.0
2014-02-03 04:10:19  0.01836     60*30    Clear   19.7

The photometry is based on nearby USNO-B1.0  stars

USNO-B1.0    RA              Dec             R2
0968-0105340 06:33:22.23 +06:53:43.2 15.41
0969-0108800 06:33:26.73 +06:56:58.4 14.77
0969-0108730 06:33:22.76 +06:55:10.3 15.73

B.P. Gompertz (U. Leicester), M. de Pasquale (INAF-IASFPA), A. Maselli 
(INAF-IASFPA), A. Melandri (INAF-OAB), J.A. Kennea (PSU), V. Mangano
(PSU), M.C. Stroh (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester) and T.N. Ukwatta report on behalf of the Swift-XRT team:

We have analysed 5.7 ks of XRT data for GRB 150203A (Ukwatta et al. GCN
Circ. 17377
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 ), from 64 s to 24.0 ks after the  BAT trigger. The data
comprise 76 s in Windowed Timing (WT) mode (the first 8 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 Evans et
al. (GCN Circ. 17378
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 ).

The light curve can be modelled with an initial power-law decay with an
index of alpha=2.84 (+0.15, -0.13), followed by a break at T+355 s to
an alpha of 0.59 (+0.09, -0.08).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.87 (+0.29, -0.27). The
best-fitting absorption column is  1.20 (+0.35, -0.30) x 10^22 cm^-2,
in excess of the Galactic value of 6.5 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.1 (+0.4, -0.3) and
a best-fitting absorption column of 1.5 (+0.5, -0.4) x 10^22 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 5.3 x 10^-11 (1.2 x 10^-10) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.5 (+0.5, -0.4) x 10^22 cm^-2
Galactic foreground: 6.5 x 10^21 cm^-2
Excess significance: 3.5 sigma
Photon index:	     2.1 (+0.4, -0.3)

If the light curve continues to decay with a power-law decay index of
0.59, the count rate at T+24 hours will be 0.011 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.6 x
10^-13 (1.2 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00629578.

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

D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ),
S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech)
report on behalf of MITSuME and OISTER collaboration:

We observed the field of GRB 150203A (Ukwatta et al., GCNC 17377)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.

The observation started on 2015-02-03 10:36:11 UT (~6.5 h after the burst).
We did not find any new point source within the enhanced XRT circle
(Evans et al., GCNC 17384) in all the three bands.

Three sigma upper limits of the OT are listed below.
We used GSC2.3 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'     Rc     Ic
-----------------------------------------------------
0.36578    12:55:51    6060.0   >19.8  >19.5  >18.7
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]

P. D'Avanzo, S. Covino (INAF-OAB), V. D'Elia (ASI/ASDC & INAF/OAR) report on behalf of the REM team: 

We observed the field of GRB 150203A (Ukwatta et al., GCN 17377
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 ) with the 60-cm robotic telescope
REM located at the La Silla Observatory (Chile). The observations started at 04:10:09 UT, 62 seconds 
after the GRB, and were carried out simultaneously with in the g, r, i, z and H bands.

No source is detected at the X-ray afterglow position reported by Evans et al. (GCN 17384
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 ). 
At a mean t-t0 of 181 s, we obtain the following 3sigma upper limits: 

g > 17.8 mag
r > 17.7 mag
i > 17.5 mag
H > 17.5 mag

All magnitudes are in the AB system and are not corrected for Galactic reddening. 
The photometry is calibrated against the APASS (optical) and 2MASS (NIR) catalogues.

V. Pelassa (UAH) and H.-F. Yu (MPE) report on behalf of the Fermi GBM Team:

"At 04:09:10.06 UT on 03 Feb 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150203A (trigger 444629353 / 150203173), which
was also detected by Swift (Ukwatta et al. 2015, GCN 17377
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 ). The GBM
on-ground location is consistent with the Swift position. The angle from
the Fermi LAT boresight is 97 degrees.

The GBM light curve shows a single pulse with a duration (T90) of
about 26 s (50-300 keV). The time-averaged spectrum from T0-2.048 s
to T0+ 27.648 s is well fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.82 +/- 0.32 and the cutoff
energy, parameterized as Epeak, is 59 +/- 8 keV.

The event fluence (10-1000 keV) in this time interval is
(1.29 +/- 0.13)E-06 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+13.952 s in the 10-1000 keV band is 1.8 +/- 0.3 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

Klotz A., Turpin D. (IRAP-CNRS-OMP),
Boer M., Gendre B., Siellez K., Dereli H., Bardho O. (UNS-CNRS-OCA),
Atteia J.L. (IRAP-CNRS-OMP) report:

We imaged the field of GRB 150203A detected by SWIFT
(trigger 629578) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 37.1s after the GRB trigger
(13.6s after the notice). The elevation of the field decreased from
45 degrees above horizon and weather conditions
were good but the field of view is located at low
galactic latitude (extinction estimated > 14 magnitudes
in the R band).

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 with a limiting magnitude of:
t0+37.1s to t0+97.1s : Rlim = 15.8

The second image is 90.0s exposure in tracking mode:
t0+391s to t0+481s : Rlim = 16.4

We co-added a series of exposures:
t0+391s to t0+1203s : Rlim = 17.0

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

N.B. Galactic coordinates are lon=204.7072 lat= -0.7535

C. Delvaux, K. Varela and J. Greiner (all MPE Garching) report on behalf
of the GROND team:

We observed the field of GRB 150203A (SWIFT-629578; Ukwatta et al., GCN
#17377
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 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla
Observatory (Chile).

Observations started on February 3rd, 2015, at 04:20 UT, 11 minutes after
the GRB trigger. They were performed at an average seeing of 1.2" and at
an average airmass of 2.1. The distance from the moon was only 28 deg.

We do not detect a source inside the 2.1 arcsec error circle reported by
Ukwatta et al. (GCN #17377
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 ). Based on a total exposure of 0.83 hours in
g'r'i'z'
and 0.80 hours in JHK, at a midtime of 0.7 hour after the burst, we measure
the following preliminary upper limits (AB magnitudes system):

g' > 23.5 mag,
r' > 23.9 mag,
i' > 24.0 mag,
z' > 24.1 mag,
J > 21.5 mag,
H > 20.9 mag, and
K > 18.6 mag.

Given magnitudes are calibrated against GROND zeropoints as well as 2MASS
field stars and are not corrected for the expected Galactic foreground
extinction corresponding to a reddening of E_(B-V) = 0.88 mag in the
direction of the burst (Schlegel et al. 1998).

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

Using 1115 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 150203A, 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 = 98.39900, +6.95372 which is equivalent
to:

RA (J2000): 06h 33m 35.76s
Dec (J2000): +06d 57' 13.4"

with an uncertainty of 1.9 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.

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB),
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús
González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and
Harvey Moseley (GSFC) report:

We observed the field of GRB 150203A (Ukwatta, et al., GCN 17377
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 ) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on
Sierra San Pedro Mártir from 2015/02 3.19 to 2015/02 3.26 UTC (0.50 to 2.14
hours after the BAT trigger), obtaining a total of 1.28 hours exposure in
the r, i, and z bands.

We find no uncatalogued sources within the Swift-XRT error circle (Evans,
et al., GCN 17378
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 ).  In comparison with USNO-B1 and 2MASS, we obtain the
following upper limits (3-sigma):

  r > 23.1
  i > 23.3
  z > 20.1

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

We thank the staff of the Observatorio Astronómico Nacional in San Pedro
Mártir.

D. A. Perley (Caltech) reports on behalf of a larger collaboration:

The Palomar 60-inch robotic telescope responded to the Swift alert for 
GRB 150203A (Ukwatta et al., GCN 17377
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 ) and began automatic follow-up at 
04:11:42 UT, 155 s after the BAT trigger.  The telescope acquired a 
series of cycling 60-second r, i, and z exposures under good seeing 
conditions.

We detect no source in or near the XRT position (Evans et al., GCN 
17378
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 ), in any individual exposure or in a stack of the first several 
minutes of imaging acquired in each filter.  An approximate limiting 
magnitude of the r-band stack (7 minutes of imaging at a median time of 
13.0 minutes post-trigger) is >21.5 mag, calibrated relative to USNO B1.0.

Given the low galactic latitude, no further follow-up is planned.

WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:

The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRB 150203A (Ukwatta et al.,
GCN 17377
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 ) starting at 04:10:55 UT, 108 s after the burst, with
thin cloud condition. Observations were performed with an automatic
sequence in the clear (roughly R), V, and I filters, and the
exposure time was 20 s per image. We do not detect any new source
neither in our single images, nor in the co-add of the first 5 images,
within the enhanced XRT error (Evans, GCN 17378
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 ). The typical
limiting magnitude of our single clear image is about 17.8 calibrated
to USNO B1.0.

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

Using  promptly downlinked XRT event data for GRB 150203A, we find an
enhanced XRT position of the afterglow: RA, Dec: 98.3993, 6.9532 which
is equivalent to:
   RA (J2000)  = 06 33 35.84
   Dec (J2000) = +06 57 11.5
with an uncertainty of 2.1 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/629578.

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.

T. N. Ukwatta (LANL), W. H. Baumgartner (GSFC/UMBC),
M. M. Chester (PSU), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:

At 04:09:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150203A (trigger=629578).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 98.415, +6.968 which is 
   RA(J2000) = 06h 33m 39s
   Dec(J2000) = +06d 58' 04"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 30 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 04:10:21.5 UT, 74.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
98.3997, 6.9533 which is equivalent to:
   RA(J2000)  = 06h 33m 35.92s
   Dec(J2000) = +06d 57' 11.9"
with an uncertainty of 2.3 arcseconds (radius, 90% containment). This
location is 76 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 6.52
x 10^21 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 1.31e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 82 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 T. N. Ukwatta (tilan.ukwatta 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.)