GRB 130527A

B.P. Gompertz (U Leicester), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), M. M. Chester (PSU),
N. Gehrels (NASA/GSFC), J. A. Kennea (PSU),
A. Y. Lien (NASA/GSFC/ORAU), F. E. Marshall (NASA/GSFC),
C. J. Mountford (U Leicester), C. Pagani (U Leicester),
D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the
Swift Team:

At 14:21:30 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 130527A (trigger=556753).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 309.279, -24.728 which is 
   RA(J2000) = 20h 37m 07s
   Dec(J2000) = -24d 43' 39"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex peak
structure with a duration of at least 20 sec.  The peak count rate
was ~25000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 14:23:15.4 UT, 105.2 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 309.2749, -24.7244 which is equivalent to:
   RA(J2000)  = +20h 37m 5.98s
   Dec(J2000) = -24d 43' 27.8"
with an uncertainty of 5.0 arcseconds (radius, 90% containment). This
location is 18 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

The initial flux in the 2.5 s image was 2.88e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 113 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
0.04. 

Burst Advocate for this burst is B.P. Gompertz (bpg6 AT le.ac.uk). 
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 130527A, we find an
enhanced XRT position of the afterglow: RA, Dec: 309.2762, -24.7246
which is equivalent to:
   RA (J2000)  = 20 37 06.28
   Dec (J2000) = -24 43 28.6
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/556753.

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.

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

Using 872 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 130527A, 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 = 309.27631, -24.72515 which is equivalent
to:

RA (J2000): 20h 37m 6.32s
Dec (J2000): -24d 43' 30.6"

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. J. Castro-Tirado (IAA-CSIC), J. Gorosabel (IAA-CSIC, UPV-EHU), A.
Guijarro (CAHA) and M. Jelínek (IAA-CSIC), on behalf of a larger
collaboration, report:

"Following the detection of GRB 130527A by Swift (Gompertz et al. GCNC
14703), follow-up observations have been conducted with the 0.6m TELMA
telescope (+ COLORES, i'-band) at the BOOTES-2 station in Málaga and with
the 3.5m CAHA (+ Omega2000, zYJHK) at the German-Spanish Calar Alto
Observatory. Data was gathered starting at 2:30 UT (i.e. ~12.1 hr post
burst), at high airmass and with the moon only 11 degrees away. At the
position of the X-ray afterglow (Evans et al. GCNC 14705), no optical/nIR
source is detected down to J ~ 20. Further data analysis is ongoing."

V. Mangano (INAF-IASFPA), A. Melandri (INAF-OAB), B. Sbarufatti
(INAF-OAB/PSU), J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows
(PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani
(U. Leicester) and B.P. Gompertz report on behalf of the Swift-XRT
team:

We have analysed 5.9 ks of XRT data for GRB 130527A (Gompertz  et al.
GCN Circ. 14703
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 ),  from 94 s to 18.3 ks after the  BAT trigger. The
data comprise 203 s in Windowed Timing (WT) mode (the first 10 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 14704).

The late-time light curve (from T0+4.9 ks) can be modelled with  a
power-law decay with a decay index of alpha=1.15 (+0.24, -0.23).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.70 (+/-0.09). The
best-fitting absorption column is  2.4 (+/-0.3) x 10^21 cm^-2, in
excess of the Galactic value of 3.7 x 10^20 cm^-2 (Kalberla et al.
2005). The PC mode spectrum has a photon index of 1.67 (+0.16, -0.15)
and a best-fitting absorption column of 1.5 (+/-0.5) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 4.5 x 10^-11 (5.5 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.5 (+/-0.5) x 10^21 cm^-2
Galactic foreground: 3.7 x 10^20 cm^-2
Excess significance: 3.9 sigma
Photon index:	     1.67 (+0.16, -0.15)

If the light curve continues to decay with a power-law decay index of
1.15, the count rate at T+24 hours will be 5.7 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.6 x
10^-13 (3.1 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/00556753.

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

W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
E. E. Fenimore (LANL), N. Gehrels (GSFC), B.P. Gompertz (U Leicester),
H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), G. Sato (ISAS),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-700 to T+302 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 130527A (trigger #556753)
(Gompertz, et al., GCN Circ. 14703
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 ).  The BAT ground-calculated position is
RA, Dec = 309.282, -24.726 deg, which is 
   RA(J2000)  =  20h 37m 07.6s 
   Dec(J2000) = -24d 43' 35.1" 
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 10%.
 
The mask-weighted light curve shows many overlapping peakst starting
at ~T-10 sec, peaking at ~T+1 sec, and ending at ~T+170 sec.
T90 (15-350 keV) is 44 +- 16 sec (estimated error including systematics).
 
The time-averaged spectrum from T-2.9 to T+90.7 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.25 +- 0.06.  The fluence in the 15-150 keV band is 1.2 +- 0.04 x 10^-5 erg/cm2.
The 1-sec peak photon flux measured from T+0.06 sec in the 15-150 keV band
is 20.1 +- 1.4 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/556753/BA/

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 (UCSC),
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 130527A (Gompertz, et al., GCN 14703
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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 2013/05 28.35 to 2013/05 28.47 UTC (18.13 to
20.91 hours after the BAT trigger), obtaining a total of 1.97 hours
exposure in the r' and i' bands and 0.73 hours exposure in the Z, Y, J, and
H bands.


For a source within the Swift-XRT error circle (Evans, et al., GCN 14705
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 ),
in comparison with USNO-B1 and 2MASS, we obtain the following upper limits
(3-sigma):

  r'    > 21.9
  i'    > 22.3
  Z     > 20.7
  Y     > 20.6
  J     > 20.6
  H     > 20.3

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

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

Z. Cano (U. Iceland), D. Malesani (DARK), N. R. Tanvir (U. Leicester), 
D. Xu (DARK/NBI), T. Kangas (U. Turku), and J. Kajava (NOT) report on 
behalf of a larger collaboration:

On 2013 May 28, beginning at 03:55 UT, we observed the field of GRB 
130527A (Gompertz et al., GCN 14703
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 ) with the Nordic Optical Telescope 
(NOT) equipped with the ALFOSC instrument using the z filter, for a 
total exposure time of 40 minutes. Observations were carried out at 
moderate airmass, with the bright Moon only 18 deg away, at a mean epoch 
of May 28.179 UT (13.94 hr after the GRB).

Inside the refined XRT error circle (Evans et al., GCN 14705
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 ; see also 
http://www.swift.ac.uk/xrt_positions/) we do not detect any bright 
source, but there is a faint, apparently extended object with magnitude 
z = 21.4 +- 0.2. The limiting magnitude for an isolated object in our 
coadded image is z = 22.1. Calibration has been derived using two stars 
in the USNO B1 catalog (0652-0853265 and 0652-0853288), and converting 
their R2 and I magnitudes into z using the transformation equations from 
Jordi et al. (2006, A&A, 460, 339). The source could be the GRB host.

A snapshot showing our coadded image can be found at the URL 
http://www.astro.ku.dk/~malesani/GRB/130527A/GRB130527A_finder_NOT.jpg

M. M. Chester (PSU) and B. P. Gompertz (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 130527A
113 s after the BAT trigger (Gompertz et al., GCN Circ. 14703
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 ).
No optical afterglow consistent with the XRT position (Evans et al. 
GCN Circ. 14705
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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           113          263          147         >21.2
white              113         1547          392         >21.1
white             4949        12020          623         >21.8

v                  655         1596          117         >18.7
v                 5359         5559          197         >19.5

b                  581         1693          114         >20.2
b                 6179        11579          906         >21.3

u_FC               325          575          246         >20.3
u                  325         1671          343         >20.2
u                 5974        18261         1072         >21.1

w1                 704         1646           97         >19.8
w1                5769        17356         1082         >21.1

m2                 680         1621          117         >20.0
m2                5564         5764          197         >19.8

w2                 630         1572          117         >20.6
w2                5154         5354          197         >20.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).

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

The long-duration intense hard-spectrum GRB 130527A
(Swift-BAT trigger 556753: Gompertz et al., GCN 14703
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 ;)
Baumgartner et al., GCN 14708
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 )
triggered Konus-Wind at T0=51688.300s UT (14:21:28.300).

The light curve shows a bright hard multi-peaked
emission complex from ~T0 s to ~T0+10s,
followed by the weaker and softer emission out to ~T0+40s.

The emission is seen up to 10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB130527_T51688/

As observed by Konus-Wind, the burst
had a fluence of (1.1 � 0.05)x10-4 erg/cm2,
and a 64-ms peak flux, measured from T0+3.200s,
of (5.0 � 0.3)x10-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+38.656 s)
is best fit in the 50 keV - 15 MeV range
by the cutoff power law model with the following parameters:
the photon index alpha = -1.04 � 0.04,
the peak energy Ep = 1380 � 120 keV,
chi2 = 96/90 dof.

The spectrum at the maximum count rate
(measured from T0+0.256 to T0+5.888 s)
is best fit in the 50 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
by the cutoff power law model with the following parameters:
the photon index alpha = -0.97 � 0.04,
the peak energy Ep = 1429 � 84 keV,
chi2 = 72/79 dof.

All the quoted results are preliminary.

H. Ueno, M. Tashiro, Y. Terada, T. Yasuda, Y. Ishida,
S. Sugimoto (Saitama U.), M. Ohno, K. Takaki, T. Kawano,
R. Nakamura, S. Furui, Y. Fukazawa (Hiroshima U.),
M. Yamauchi, N. Ohmori, M. Akiyama (Univ. of Miyazaki),
K. Yamaoka (Nagoya U.), S. Sugita (Ehime U.), Y. E. Nakagawa,
M. Kokubun, T. Takahashi (ISAS/JAXA), W. Iwakiri(RIKEN),
Y. Hanabata (ICRR), Y. Urata (NCU), K. Nakazawa,
K. Makishima (Univ. of Tokyo) on behalf of the Suzaku WAM team, report:


The bright, long GRB 130527A (Swift-BAT detection: W. H. Baumgartner,
et al. , GCN 14708
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 ) triggered the Suzaku Wide-band All-sky Monitor (WAM)
which covers an energy range of 50 keV - 5 MeV at UT 14:21:27.030(=T0).

The observed light curve shows a multi-peaked structure starting at
T0-0.5 s, ending at T0+13 s with a duration (T90) of about 7.4 seconds.
The fluence in 100 - 1000 keV was 5.26 (-0.36, +0.39) *10^-5 erg/cm^2.
The 1-s peak flux measured from T0+4.5 s was
20.26 (-0.92, +1.12) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from
T0-1 s to T0+13 s is well fitted by a GRB Band model as follows.
the low-energy photon index alpha: -0.87 (-0.13, +0.10),
the high-energy photon index beta: -2.68 (-0.36, +0.14),
and the peak energy Epeak: 1426 (-123, +221) keV,
(chi^2/d.o.f = 36.3/28).

Due to the brightness of this burst, a 3% systematic error was added
for low energy channels.
All the quoted errors are at statistical 90% confidence level.

The light curves for this burst are available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html