GRB 130604A

A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), C. Gronwall (PSU),
C. B. Markwardt (NASA/GSFC), C. Pagani (U Leicester),
D. M. Palmer (LANL), M. H. Siegel (PSU) and
R. L. C. Starling (U Leicester) report on behalf of the Swift Team:

At 06:54:26 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 130604A (trigger=557354).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 250.080, +68.210 which is 
   RA(J2000) = 16h 40m 19s
   Dec(J2000) = +68d 12' 36"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
FRED-like structure with a duration of about 70 sec.  The peak count 
rate was ~1500 counts/sec (15-350 keV), at ~5 sec after the trigger. 

The XRT began observing the field at 06:56:06.2 UT, 99.3 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source with an enhanced position: RA, Dec 250.1889,
68.2260 which is equivalent to:
   RA(J2000)  = 16h 40m 45.34s
   Dec(J2000) = +68d 13' 33.6"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 156 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 4.70
x 10^20 cm^-2 (Kalberla et al. 2005). 

The initial flux in the 2.5 s image was 1.76e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT data are not available at this time. Analysis is awaiting the full
data set. 

Burst Advocate for this burst is A. Melandri (andrea.melandri AT brera.inaf.it). 
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.)

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

The Palomar 60-inch telescope responded automatically to GRB 130604A 
(Melandri et al., GCN 14752
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 ) and began a series of images at 06:58:16 
UT, three minutes after the alert notice.  We detect a faint (~20 mag) 
source near the center of the XRT error circle in the initial 60-second 
r-band and i-band exposures.  It is not clearly detected in z-band.  The 
coordinates of the optical transient candidate are:

RA  = 16:40:45.290
DEC = +68:13:33.58
(+/- 0.9", J2000)

Observations are continuing.

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

We observed the afterglow of GRB 130604A (Melandri et al., GCN 14752
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 )
with the 0.76-m Katzman Automatic Imaging Telescope (KAIT) located at
Lick Observatory. Observations started at 06:57:07 UT, 161 s after the
burst, with an automatic sequence in V, I, and clear filters (20 s
exposure for each image). We do not detect the afterglow at the position
reported by Perley (GCN 14753
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 ). We estimate the limiting magnitude in
our first clear-band (close to R) image to be about 18.5 at a time of
330 s after the burst. 

Continuing observations are in progress.

L. Elenin (KIAM),  V. Savanevych (KNURE),  A. Bryukhovetskiy (NSFCTC),  I. 
Molotov (KIAM), A. Pozanenko (IKI) report on behalf of  larger GRB 
follow-up collaboration:

We observed of  the field of  the Swift GRB 130604A (Melandri et al., GCN 
14752
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 )  with 0.45-m telescope of ISON-NM observatory on June. 04 (UT) 
06:56:11, i.e. 105 s after burst trigger. Series of 30 s and 60 s exposures 
were obtained in clear filter. In the combined image of the first 3 images 
we do not detect afterglow candidate (Perley, GCB 14753).  Preliminary 
photometry  is based  on the USNO-B1.0 (R2)  nearby  stars:

UT start,      T0+        Exposure,  OT,              UL (3 sigma)
                   days      s

06:56:11       0.0019  3x30           n/d              19.7

L. Elenin (KIAM),  V. Savanevych (KNURE),  A. Bryukhovetskiy (NSFCTC),  I. 
Molotov (KIAM), A. Pozanenko (IKI) report on behalf of  larger GRB follow-up 
collaboration:

After further inspection of images after observation of the Swift GRB 
130604A (Melandri et al., GCN 14752
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 )  with 0.45-m telescope of ISON-NM 
(Elenin, et al., GCN 14756
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 ) we identified faint object (S/N ~ 3) in 
coordinates (J2000) 16 40 45.34   +68 13 34.5  with uncertainty of  0.2" (in 
both coordinates). Within errors this position coincides with the afterglow 
candidate (Perley, GCB 14753) and the error circle of XRT reported by 
Melandri et al. (GCN 14752
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 ). This object is not detected in our later 
combined images and can be the afterglow of GRB 130604A. Preliminary 
photometry  of our images obtained in clear filter is based  on USNO-B1.0 
(R2)  nearby  stars:

UT start,      T0+          Exposure,  OT,                 UL (3 sigma)
                   mid,days  s

06:56:11       0.0019    3x30           n/d                  19.7
06:56:11       0.0035    9x30           20.3 +/- 0.3      20.0
06:56:11       0.0091  30x30           n/d                  20.5
06:56:11       0.0171  60x30           n/d                  20.8

Finding chart can be found at 
http://grb.rssi.ru/GRB130604A/GRB130604A_ISON_NM_9x30.png

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 130604A (Melandri et al., GCNC 14752)
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 2013-06-04 11:52:48 UT (~5.0 h after the burst).
We could not detect the previously reported afterglow
(Perley, GCNC 14753; Elenin et al., GCNC 14758) in all the three bands.

Three sigma upper limits of the OT are listed below.
We used GSC 2.3 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'     Rc     Ic
-----------------------------------------------------
0.24913    12:53:10    6360.0   >20.3  >20.2  >19.5
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]

S. B. Cenko (GSFC), N.R. Tanvir (Leicester)D. A Perley (Caltech), A. J. Levan (U. Warwick), and
A. Cucchiara (UCSC / Lick) report on behalf of a larger collaboration:

We have obtained optical spectra of the afterglow (Perley et al., GCN
14753
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 ) of GRB 130604A (Melandri et al., GCN 14752
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 ) with the Gemini
Multi-Object Spectrograph mounted on the 8 m Gemini North telescope.
Observations began at 8:16 UT on 2013 June 4 (~ 1.3 hr after the Swift
trigger) and cover the wavelength range from 4000 - 8000 A.

Superimposed on a faint continuum, we detect a single bright emission line
at an observed wavelength of ~ 7674.0 A.  There is some evidence the
emission line is spectrally resolved.  No other obvious features (in
emission or absorption) are detected over our wavelength range.  If we
assume this feature corresponds to [O II], this implies a redshift of z =
1.06 for GRB 130604A.

[GCN OPS NOTE(04Jun13): Per author's request, NRT was added to the author list.]

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

Using 832 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 130604A, 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 = 250.18823, +68.22651 which is equivalent
to:

RA (J2000): 16h 40m 45.18s
Dec (J2000): +68d 13' 35.4"

with an uncertainty of 2.1 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.

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

We have analysed 5.7 ks of XRT data for GRB 130604A (Melandri  et al.
GCN Circ. 14752
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 ),  from 105 s to 21.8 ks after the  BAT trigger. The
data comprise 146 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Goad et al. (GCN. Circ 14763).

The light curve can be modelled with  a power-law decay with a decay
index of alpha=2.02 (+0.08, -0.06).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.10 (+0.13, -0.12). The
best-fitting absorption column is  2.8 (+/-0.4) x 10^21 cm^-2, in
excess of the Galactic value of 4.7 x 10^20 cm^-2 (Kalberla et al.
2005). The PC mode spectrum has a photon index of 2.1 (+/-0.3) and a
best-fitting absorption column of 2.2 (+1.0, -0.9) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.8 x 10^-11 (5.9 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.2 (+1.0, -0.9) x 10^21 cm^-2
Galactic foreground: 4.7 x 10^20 cm^-2
Excess significance: 3.3 sigma
Photon index:	     2.1 (+/-0.3)

If the light curve continues to decay with a power-law decay index of
2.02, the count rate at T+24 hours will be 5.8 x 10^-5 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.2 x
10^-15 (3.5 x 10^-15) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00557354.

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

A. A. Breeveld (MSSL-UCL) and A. Melandri (INAF-OAB) report on behalf of 
the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 130604A 
109 s after the BAT trigger (Melandri et al., GCN Circ. 14752
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 ). No 
optical afterglow consistent with the optical position (Perley, GCN 
Circ. 14753
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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           109          258          147         >20.4
white              109        17767         1345         >21.8
v                 5004        11999         1055         >20.3
b                 4388        16933         1278         >21.5
u                  267         5818          378         >20.0
w1                5414         5613          197         >20.0
m2                5208         5408          197         >19.7
w2                4798        11112         1082         >21.3

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.03 in the direction of the 
burst (Schlegel et al. 1998).

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/GSFC/ORAU),
C. B. Markwardt (GSFC), A. Melandri (INAF-OAB), 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-240 to T+962 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 130604A (trigger #557354)
(Melandri, et al., GCN Circ. 14752
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 ).  The BAT ground-calculated position is
RA, Dec = 250.166, 68.225 deg, which is 
   RA(J2000)  =  16h 40m 39.9s 
   Dec(J2000) = +68d 13' 28.4" 
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 81%.
 
The mask-weighted light curve shows a FRED-like peak starting at ~T-1 sec,
peaking at ~T+10 sec, and ending at ~T+90 sec.
T90 (15-350 keV) is 37.7 +- 4.6 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.44 to T+43.58 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.51 +- 0.12.  The fluence in the 15-150 keV band is 1.4 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+14.39 sec in the 15-150 keV band
is 0.8 +- 0.2 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/557354/BA/