GRB 130511A

F. Yuan, M. Childress, S. Rapoport, B. Schmidt, M. Dopita (Australian National University) and J. Scharwachter (Observatoire de Paris)

We observed the field of GRB 130511A (Krimm et al., GCN 14620
Loading...
 
 ) using the Wide Field Spectrograph (WiFeS) on the ANU 2.3m. Three 900s integration at resolution R=3000, covering 540 - 950nm, were obtained starting at 2013-05-11 12:03 UTC, ~32 minutes after the Swift trigger.

Spectral photometry of the sky-subtracted data cube was carried out in a 6" diameter aperture. Compared to a nearby field star, we measure the optical afterglow to be at r ~ 20.2 and i ~ 20.1 at a mean time of ~ 1 hr after the burst.
We thank Tiantian Yuan, Fred Vogt and Rebecca Davis for performing this observation.

M. Im (CEOU/SNU), H.-I. Sung (KASI), & Y. Urata (NCU)
on behalf of a larger collaboration

We observed GRB 130511A (Krimm et al., GCN 14620
Loading...
 
 ) 
in BVRI filters using a 0.6m telescope at the Sobaeksan
Optical Astronomy Observatory (SOAO), starting at 76min 
after the BAT alert.

In stacked images of 6 x 300sec exposures, we identify
the optical afterglow with the following magnitude
(Cucchiara et al. GCN 14621
Loading...
 
 ; Takaki et al. GCN 14626
Loading...
 
 ),
calibrated against a USNO-B1 star in the vicinity.

   T(mid, UT)         Mag
05-11 13:50:12     R=20.78 +- 0.13

The afterglow is detected in the other bands, but at
a lower S/N.

We thank the staffs at SOAO for performing the observation.

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

We have analysed 8.4 ks of XRT data for GRB 130511A (Krimm  et al. GCN
Circ. 14620
Loading...
 
 ),  from 57 s to 36.5 ks after the  BAT trigger. The data
comprise 8 s in Windowed Timing (WT) mode (taken while Swift was
slewing), with the remainder in Photon Counting (PC) mode. The enhanced
XRT position for this burst was given by Goad et al. (GCN. Circ 14622).

The light curve can be modelled with  a power-law decay with a decay
index of alpha=0.99 (+/-0.04).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.03 (+0.20, -0.19). The
best-fitting absorption column is  1.1 (+0.5, -0.4) x 10^21 cm^-2, in
excess of the Galactic value of 2.1 x 10^20 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.6 x 10^-11 (4.8 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.1 (+0.5, -0.4) x 10^21 cm^-2
Galactic foreground: 2.1 x 10^20 cm^-2
Excess significance: 3.5 sigma
Photon index:	     2.03 (+0.20, -0.19)

If the light curve continues to decay with a power-law decay index of
0.99, the count rate at T+24 hours will be 2.6 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.4 x
10^-14 (1.2 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/00555600.

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

K. Takaki, K. Kawaguchi, K. S. Kawabata, M. Ohno and M. Yoshida 
(Hiroshima Univ.) report on behalf of Kanata team:

We performed optical observations of GRB 130511A (Krimm et al., GCN 14620
Loading...
 
 )
with HOWPol attached to the 1.5-m Kanata telescope at Higashi-Hiroshima
Observatory, Japan. The observation started at 11:32 UT on 2013 May 11 
with imaging-polarimetry mode, followed by observation with imaging mode 
after 12:10 UT. We detected the optical afterglow of the GRB.

Photometric results are shown below. We calibrated the Rc magnitude using
USNO-B1.0 R2 magnitudes of nearby stars. Our result seems to be consistent 
with the brightness upper-limits reported in Xin et al. (GCN 14623
Loading...
 
 ) and 
Kuroda et al. (GCN 14625
Loading...
 
 ). The decline rate between these two epochs can 
be approximated by a single power-law with an index of -0.7.

Mid time from  Total Exp   Filter    Magnitude
trigger (s)    (s)
-------------------------------------------------
2571            300x2        Rc    20.0+-0.1
8768            300x2        Rc    21.0+-0.2
-------------------------------------------------

This message may be cited.

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 130511A (Krimm et al., GCNC 14620)
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 2013-05-11 12:01:00 UT (~30 min after the burst).
We did not find any new point source within the enhanced XRT error circle
(Osborne et al., GCNC 14622) in all the three bands.

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

#T0+[day]  MID-UT    T-EXP[sec]   g'     Rc     Ic
-----------------------------------------------------
0.16126    15:23:00    5940.0   >20.7  >20.7  >19.8
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]

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/GSFC/ORAU), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU),T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):

Using the data set from T-240 to T+950 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 130511A (trigger #555600)
(Krimm, et al., GCN Circ. 14620
Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 196.654, 18.709 deg which is
    RA(J2000)  =  13h 06m 36.9s
    Dec(J2000) = +18d 42' 33.7"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 57%.

The mask-weighted light curve shows an initial sharp double-peak at T0
of duration ~0.5 seconds, transitioning to a FRED-like decay lasting ~5
seconds, after which the light curve returns to baseline.
T90 (15-350 keV) is 5.43 +- 2.22 sec (estimated error including systematics).

The time-averaged spectrum from T-0.07 to T+6.03 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.35 +- 0.31.  The fluence in the 15-150 keV band is 2.2 +- 0.4 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T-0.09 sec in the 15-150 keV band
is 1.3 +- 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/555600/BA/

L. P. Xin, J. Y. Wei, Y. L. Qiu,  J. Wang, 
J. S. Deng, C. Wu, X. H. Han  report on behalf of EAFON team:

We began to observe the field of GRB 130511A  (Krimm et al. GCN 14620
Loading...
 
 )
using  80cm TNT telescope located at Xinglong observatory, China,
at 41.9 min after the burst on 12:12:41 UT, May 11th, 2013.    
15*300sec R-band images was obtained.  

The reported optical counterpart (Krimm et al. GCN 14620
Loading...
 
 ;  Cucchiara et a. GCN 14621
Loading...
 
 )  
was not detected in all single images and the combined image,  
down to the upper limit of R~19.6 mag calibrated by USNO B1.0 R2 mag,
 at the mean time of  62.3 min after the trigger time. 

This message may be cited.

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

Using 1521 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 130511A, 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 = 196.64526, +18.70977 which is equivalent
to:

RA (J2000): 13h 06m 34.86s
Dec (J2000): +18d 42' 35.2"

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. Cucchiara (UCSC) and N. R. Tanvir (U. Leicester) 
report on behalf of a larger collaboration:

On May 11.511 UT (~45 minutes after the Swift trigger)
we observed the optical counterpart of GRB 130511A
(Krimm et al. GCN 14620
Loading...
 
 ) with the GMOS spectrograph
mounted on the Gemini-North telescope.

The observation consists of 2x900s exposures
using the B600 grating and covers the 5100-7900
Angstroms wavelength range.

The resulting spectrum presents several absorption lines, 
including FeII(2344,2382,2374,2600), FeII*(2338,2349), 
FeI2463, MnII(25762594), MgII doublet (2796,2803A), and 
MgI2853 at the common redshift of z=1.3033.

We therefore propose this as the redshift of GRB 130511A.

We thank the Gemini staff for performing this
observation, in particular Tom Geballe.

H. A. Krimm (CRESST/GSFC/USRA), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the
Swift Team:

At 11:30:47 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 130511A (trigger=555600).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 196.639, +18.698 which is 
   RA(J2000) = 13h 06m 33s
   Dec(J2000) = +18d 41' 51"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single short
peak of duration ~0.5 sec followed by a 10-second tail. The peak count rate
was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 11:31:58.9 UT, 71.6 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 196.64698, 18.70893 which is equivalent
to:
   RA(J2000)  = 13h 06m 35.28s
   Dec(J2000) = +18d 42' 32.1"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 47 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 in excess of the Galactic value (2.08 x
10^20 cm^-2, Kalberla et al. 2005), with an excess column of 2.5
(+1.47/-1.33) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 74 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	13:06:34.96 = 196.64567
  DEC(J2000) = +18:42:36.0  =  18.70999
with a 90%-confidence error radius of about 0.64 arc sec. This position is 7.0
arc sec. from the center of the XRT error circle. The estimated magnitude is
19.18 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.03. 

Burst Advocate for this burst is H. A. Krimm (krimm AT milkyway.gsfc.nasa.gov). 
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.)