GRB 140413A

K. Varela, C. Delvaux (both MPE Garching), A. Nicuesa Guelbenzu (TLS
Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND
team:

We observed the field of GRB 140413A (Swift trigger 595616; D'Elia et al.,
GCN #16098
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 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2 m MPG telescope at La Silla Observatory
(Chile).

Observations started at 00:13 UT on 13 April 2014, less than 5 min after
the GRB trigger, and are continuing. They are performed at a mean airmass
of 1.9 and a mean seeing of 0.9".

We find a single point source within the 5.8" Swift/XRT error circle at
coordinates

   RA(J2000)  =  04:21:49.23
   Dec(J2000) = -51:10:58.0.

At a midtime of 00:17 UT we measure the following preliminary AB magnitudes:

r' = 20.2 +/- 0.1,
i' = 19.6 +/- 0.1,
z' = 19.3 +/- 0.1.

The source is also visible in g. At present we cannot decide if the source
is fading. Data processing is still ongoing, observations are continuing.

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)=0.02 mag in the
direction of the burst (Schlegel et al. 1998).

V. D'Elia (ASDC) and L. Izzo (URoma/ICRA) report for the Swift/XRT team:

The XRT began observing the field of GRB 140413A at 00:46:31.37 UT, 2211.2 seconds after the BAT trigger. We find an uncatalogued X-ray source located at RA, Dec 65.4544, -51.1831 which is equivalent to:
�RA(J2000) �=+04h 21m 49.0s
�Dec(J2000) =-51d 10' 59.1"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This location is 80 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received.

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 140413A detected by SWIFT
(trigger 595616) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 92.3s after the GRB trigger
(16.4s after the notice) probably during the end of
the prompt gamma emission regarding the BAT light curve.
The elevation of the field decreased from 36 degrees
above horizon and weather conditions were good.

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 the GROND OT candidate (Varela et al.
GCNC 16099) with a limiting magnitude of:
t0+92.3s to t0+152.3s : Rlim = 17.0

The second image is 30.0s exposure in tracking mode:
t0+165.6s to t0+195.6s : Rlim = 17.6

We co-added series of exposures:
t0+165.6s to t0+457.5s : Rlim = 19.3
t0+468.3s to t0+ 1362s : Rlim = 19.3

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

S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
V. D'Elia (ASDC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (NASA/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 140413A (trigger #595616)
(D'Elia, et al., GCN Circ. 16098
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 ).  The BAT ground-calculated position is
RA, Dec = 65.439, -51.188 deg, which is 
   RA(J2000)  =  04h 21m 45.4s 
   Dec(J2000) = -51d 11' 15.1" 
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 12%.
 
The mask-weighted light curve shows a slow rise starting at ~T-65 sec,
peaking at ~T+80 sec, and a faster decay out to ~T+115 sec.
T90 (15-350 keV) is 139.6 +- 12.6 sec (estimated error including systematics).
 
The time-averaged spectrum from T-52.0 to T+120.4 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.49 +- 0.08.  The fluence in the 15-150 keV band is 9.4 +- 0.5 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+77.05 sec in the 15-150 keV band
is 2.3 +- 0.5 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/595616/BA/

L. Izzo (URoma/ICRA) and V. D'Elia (ASDC) report on behalf of the
Swift-XRT team:

We have analysed 13 ks of XRT data for GRB 140413A,  from 2.2 ks to
83.3 ks after the  BAT trigger. The data comprise 2.1 ks in Windowed
Timing (WT) mode with the remainder in Photon Counting (PC) mode. Using
3951 s of PC mode data and 4 UVOT images, we find an enhanced XRT
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 65.45475, -51.18310 which is
equivalent to:

RA (J2000): 04h 21m 49.14s
Dec(J2000): -51d 10' 59.2"

with an uncertainty of 1.6 arcsec (radius, 90% confidence).

The late-time light curve (from T0+38.1 ks) can be modelled with  a
power-law decay with a decay index of alpha=1.7 (+/-0.4).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.989 (+0.025, -0.024). The
best-fitting absorption column is  4.04 (+/-0.13) x 10^21 cm^-2, in
excess of the Galactic value of 1.4 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.9 x 10^-11 (6.0 x 10^-11) erg
cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:	     4.04 (+/-0.13) x 10^21 cm^-2
Galactic foreground: 1.4 x 10^20 cm^-2
Excess significance: 49.9 sigma
Photon index:	     1.989 (+0.025, -0.024)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00595616.

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

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

The long GRB 140413A (Swift-BAT trigger #595616:
D'Elia et al., GCN 16098
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 ; T0(BAT)=00:09:40 UT)
was detected by Konus-Wind in the waiting mode.

The light curve shows a broad emission pulse which started
~65 s before the BAT trigger, peaked at ~T0(BAT)+80 s,
and lasted till ~T0(BAT)+120 s.

A possible soft precursor is seen at ~T0(BAT)-950 s
in the softest KW energy band, however its association with
GRB 140413A is not confirmed yet.

The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB140413A/

As observed by Konus-Wind, the burst had a fluence of
(2.9 � 0.3)x10^-5 erg/cm2 and a 2.944-s peak energy flux,
measured from ~T0(BAT)+80 s, of (5.2 � 0.5)x10^-7 erg/cm2
(both in the 20 - 10000 keV energy range).

Modeling the KW 3-channel time-integrated spectrum
(from T0(BAT)-60 s to T0(BAT)+121 s) by a power law
with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -1.37 � 0.11, and Ep = 228 � 42 keV.

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

S. T. Holland (STScI) and V. D'Elia (ASDC) report on behalf of the
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 140413A
2221 s after the BAT trigger (D'Elia et al., 2014, GCNC 16098).  The
preliminary UVOT position is

     RA (J2000)  04:21:49.23  =   65.45512 (deg)
    Dec (J2000) -51:10:58.0   =  -51.18278 (deg)

with an estimated uncertainty of 1.79 arcsec (radius, 90% confidence,
statistical + systematic).  We detect the optical afterglow at the
position reported by Varela et al. (2014, GCNC 16099).  Preliminary
UVOT photometry and 3-sigma upper limits are presented below.

----------------------------------------------------------------
Filter        TSTART     TSTOP   Exposure       Mag   Err  Sigma
----------------------------------------------------------------
v               2377      4303        375     >19.7
b               2476      3747        235     >21.0
u               2451      3542        236     >19.9
uvw1            2427      3336        236     >19.8
uvm2            2931      3131        197     >19.5
uvw2            3957      4157        197     >20.1
white           2221      2370        147     >20.3
                3752      3951        197      21.10 0.29    3.8
----------------------------------------------------------------

The quoted magnitudes and upper limits have not been corrected for the
Galactic extinction along the line of sight to this burst of E_{B-V} =
0.01 mag (Schlafly et al. 2011, ApJS, 737, 103).  The photometry is in
the UVOT photometric system (Breeveld et al. 2011, AIP
Conf. Proc. 1358, 373).

C. Delvaux (MPE Garching), D. A. Kann, S. Schmidl (both TLS Tautenburg),
and J. Greiner (MPE Garching) report on behalf of the GROND team:

We re-observed the field of GRB 140413A (Swift trigger 595616; D'Elia et
al., GCN # 16098) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at La Silla
Observatory (Chile).

Further epochs were obtained at 1, 2, 3 and 5 days after the trigger. The
source detected in the XRT error circle in early observations (Varela et
al., GCN # 16099) has faded by about 3 magnitudes in the r' band,
confirming that it is the afterglow of GRB 140413A. In the later epochs we
obtain detections in g'r'i'z'J at a constant level, possibly the host
galaxy of the GRB. If it is the host galaxy, this may be indicative of a
relatively low redshift.