GRB 140331A

B.-B. Zhang (UAH), S. D. Barthelmy (GSFC), V. D'Elia (ASDC),
J. A. Kennea (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 05:49:48 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 140331A (trigger=594081).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 134.845, +2.707 which is 
   RA(J2000) = 08h 59m 23s
   Dec(J2000) = +02d 42' 25"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual for an image trigger,
there is no obvious variation in the BAT light curve. 

The XRT began observing the field at 05:56:13.2 UT, 385.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source with an enhanced position: RA, Dec 134.8644,
2.7174 which is equivalent to:
   RA(J2000)  = 08h 59m 27.45s
   Dec(J2000) = +02d 43' 02.7"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 79 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

The initial flux in the 2.5 s image was 6.70e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 393 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 expected extinction corresponding to E(B-V) of
0.05. 

Burst Advocate for this burst is B.-B. Zhang (bbzhang AT psu.edu). 
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.)

Owen Littlejohns (ASU), 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), 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 140331A (Zhang, et al., GCN 16049
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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 2014/03 31.26 to 2014/03
31.32 UTC (0.35 to 1.87 hours after the BAT trigger), obtaining a total of
1.04 hours exposure in the r and i bands and 0.44 hours exposure in the
Z, Y, J, and H bands.

For a source within the Swift-XRT error circle, in comparison with
the SDSS DR9 and 2MASS, we obtain the following detections:

  r     22.02 +/- 0.11
  i     20.79 +/- 0.04
  Z     20.14 +/- 0.06
  Y     19.81 +/- 0.07
  J     19.75 +/- 0.08
  H     19.76 +/- 0.12

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB. This position coincides with a
previously detected source, SDSS J085927.51+024304.0. We note that our
r, i and Z band magnitudes are broadly consistent with those of the SDSS.

Fitting Milky Way, LMC and SMC extinction laws in addition to the IGM
(see Littlejohns, et al. 2014) we find the source is possibly of high
redshift, with a photometric redshift of z = 4.65 (+0.34,-2.80; 90% conf.).
The large lower limit in the confidence region is due to a potential
solution
with a high quantity of Milky Way type dust.

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

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

Using 4193 s of XRT Photon Counting mode data and 7 UVOT
images for GRB 140331A, 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 = 134.86440, +2.71729 which is equivalent
to:

RA (J2000): 08h 59m 27.46s
Dec (J2000): +02d 43' 02.3"

with an uncertainty of 1.7 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.

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 collaboration:

We observed the field of GRB 140331A (Zhang et al., GCNC 16049)
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 2014-03-31 10:40:24 UT (~4.8 h after the burst).
We could not detect the previously reported afterglow (Littlejohns et al.,
GCNC 16050) in all the three bands.

Three sigma upper limits of the OT are listed below.
We used SDSS-DR7 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'     Rc     Ic
-----------------------------------------------------
0.21730    11:02:43    2040.0   >19.6  >19.7  >18.7
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]

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 140331A detected by SWIFT
(trigger 594081) with the Zadko robotic telescope (D=100cm)
located at the observatory - Gingin, Australia.

The observations started 8.26h after the GRB trigger.
The elevation of the field was at 50 degrees above
horizon and weather conditions were good.

We co-added two series of unfiltered
exposures. They show clearly the presence of the object
reported by Littlejohns  et al. (GCNC 16050) that
coincides with SDSS J085927.51+024304.0:

=start=  =end=  Rmag
  8.26h   8.68h  20.1 +/- 0.3
  9.74h  10.43h  20.1 +/- 0.3

The magnitude remains constant during our observation
and is compatible with the magnitude found in visible
bands by Littlejohns  et al. (GCNC 16050) with RATIR
less than two hours after the trigger.
This suggests that the optical object is probably not
the afterglow of GRB 130331A.

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

M. H. Siegel (PSU) and B.-B. Zhang (UAH)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 140331A
394 s after the BAT trigger (Zhang et al., GCN Circ. 16049
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 ).
No optical afterglow consistent with either the enhanced XRT position
(Beardmore et al. GCN Circ. 16052
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 ) or the RATIR detection
(Littlejohns et al. GCN Circ. 16050
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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) exposure and subsequent exposures are:

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

white_FC           394          543          147         >21.1
white              394         8016          764         >21.9
v                  550         7092          568         >19.7
b                  649         7912          568         >20.8
u                  624         7707          568         >21.1
w1                 600         7502          563         >21.1
m2                 575         7297          529         >20.5
w2                 700         6887          352         >21.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).

M. Stamatikos (OSU), 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 (NASA/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), J. Tueller (GSFC), T. N. Ukwatta (MSU), B.-B. Zhang (UAH)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+827 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 140331A (trigger #594081)
(Zhang, et al., GCN Circ. 16049
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 ).  The BAT ground-calculated position is
RA, Dec = 134.860, 2.755 deg, which is 
   RA(J2000)  =  08h 59m 26.4s 
   Dec(J2000) = +02d 45' 19.5" 
with an uncertainty of 3.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 98%.
 
The mask-weighted light curve shows a long weak peak starting
at ~T+70 sec and ending at around T+350 sec.  T90 (15-350 keV)
is 209 +- 33 sec (estimated error including systematics).
 
The time-averaged spectrum from T87.28to T+321.14 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.01 +- 0.29.  The fluence in the 15-150 keV band is 6.7 +- 1.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+292.49 sec in the 15-150 keV band
is 0.31 +- 0.13 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/594081/BA/

P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), D.N. Burrows (PSU), J.A.
Kennea (PSU), V. Mangano (PSU), P.A. Evans (U. Leicester), B.P.
Gompertz (U. Leicester), J.P. Osborne (U. Leicester), A. Maselli 
(INAF-IASFPA) and B.-B. Zhang report on behalf of the Swift-XRT team:

We have analysed 8.0 ks of XRT data for GRB 140331A (-B. Zhang	et al.
GCN Circ. 16049
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 ),  from 374 s to 42.6 ks after the  BAT trigger. The
data comprise 118 s in Windowed Timing (WT) mode (the first 9 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
Beardmore et al. (GCN Circ. 16052
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 ).

The light curve can be modelled with an initial power-law decay with an
index of alpha=3.57 (+0.22, -0.19), followed by a break at T+1389 s to
an alpha of 0.69 (+/-0.09).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.97 (+0.13, -0.12). The
best-fitting absorption column is  6.3 (+2.9, -2.0) x 10^20 cm^-2,
consistent with the Galactic value of 4.4 x 10^20 cm^-2 (Willingale et
al. 2013). The PC mode spectrum has a photon index of 1.90 (+0.16,
-0.11) and a best-fitting absorption column of 4.8 (+3.7, -0.4) x 10^20
cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.4 x 10^-11 (3.8 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     4.8 (+3.7, -0.4) x 10^20 cm^-2
Galactic foreground: 4.4 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.90 (+0.16, -0.11)

If the light curve continues to decay with a power-law decay index of
0.69, 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 3.8 x
10^-13 (4.2 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00594081.

This circular 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 again observed the field of GRB 140331A (Zhang, et al., GCN 16049
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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 first from 2014/04 1.13 to 2014/04 1.37 UTC
(21.27 to 27.13 hours after the BAT trigger), obtaining a total of 3.50
hours exposure in the r and i bands and 1.46 hours exposure in the Z, Y, J,
and H bands and then from 2014/04 3.18 to 2014/04 3.36 UTC (70.39 to 74.71
hours after the BAT trigger), obtaining a total of 2.56 hours exposure in
the r and i bands and 1.07 hours exposure in the Z, Y, J, and H bands.

We do not detect statistically significant flux variation for the source
reported by Littlejohns et al. (2014, GCN 16050
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 ), which was also noted to
be coincident with an SDSS galaxy at z~0.7.  We, therefore, conclude that
this source is not the GRB afterglow (see, also, Klotz et al. 2014, GCN
6057
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 ).

We can utilize the observations reported here to estimate the limiting
magnitudes for the GRB during our first night of observations (mean time ~1
hr after the GRB).  For a source within the Swift-XRT error circle
(Beardmore et al. 2014, GCN 16052
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 ) , in comparison with the SDSS DR9 and
2MASS, we obtain the following (3-sigma) upper limits:

 r > 23.5
 i > 23.2
 Z > 21.3
 Y > 21.3
 J > 21.2
 H > 21.0

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.  The r-band limit implies a very
faint or reddened afterglow.  Our r-band limit relative to the X-ray flux
at the same epoch (e.g., D'Avanzo et al. 2014, GCN 16065
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 ) implies a
broadband spectral index beta_OX<0.3 (3-sigma), which is significantly
lower than the standard cuttoff (beta_OX<0.5) defining optically-dark GRBs
(e.g, Jakobsson et al. 2004).

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