GRB 040511

E. Berger (Caltech) reports:

"A re-examination of the spectra of GRB 040511 obtained with the Low
Resolution Imaging Spectrometer on the Keck-I telescope, and comparison
with later spectroscopic observations of the region, reveal that the lines
(and hence redshift) identified previously (GCN 2599
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 ) are in fact not
associated with the optical afterglow (OA) position (GCN 2597
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 ), but are
instead associated with a galaxy 10.6" away.  No continuum or lines are
identified at the actual OA position.  We apologize for any inconvenience
that this may have caused."

D. Bersier, J. M. Castro Cerón, J. Rhoads, A. Fruchter (STScI), A. Levan
(U. of Leicester), J. Gorosabel (IAA-CSIC), C. Kouveliotou (NASA/MSFC,
NSSTC), S. Patel (USRA, NSSTC), M. Merrill (NOAO), J. Bally, J.
Walawender, (U. Colorado), and B. Reipurth (Hawaii) report on behalf of
a larger collaboration:

We have observed the field of GRB 040511 (GCN Dullighan et al. 2004, GCN
2588
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 ) with the CTIO 4m telescope on the nights of May 11 and May 12.
Our R-band photometry of the candidate afterglow (Fox et al. 2004, GCN
2597
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 ) shows that this source decayed by 2.5 mag between 0.79d and 1.60d
after the burst.  Assuming that the decay follows a power law, we derive
an index of -3.2. If the variable source is indeed the afterglow of GRB
040511, this would be among the fastest decay indices ever observed.

GRB040511: REM telescope robotic NIR observations.

V. Testa, L.A. Antonelli (INAF-OAR), L.Calzoletti (Univ. Roma Sapienza),
S. Covino (INAF-OAB), G. Chincarini (Univ. Milano Bicocca), F. M. Zerbi
(INAF-OAB), E. Palazzi (IASF-CNR,Bologna), G. Tosti (Univ. Perugia),
L. Nicastro (IASF-CNR,Palermo), on behalf of the REM collaboration report:

On May 12 the 60cm robotic telescope REM at ESO-La Silla observed the field of
GRB040511, that was detected by HETE2 ~12 hours before, during day time at
La Silla. The observations were performed with the REMIR near-IR camera during
commissioning phase in the wide band filters J,H and Ks in fully
automatic mode, following a predefined sequence suited for late grb alerts.
Frames obtained in the three filters were co-added together to obtain
three images per filter, having total exposure times of 60, 360 and 720s.
The comparison with the 2MASS catalog did not reveal evident new sources,
with 3 sigma upper limits, on the 720s images, of 18.6 in the J filter,
18.2 in the H filter and 16.6 in the Ks filter. Images were calibrated by 
using a number of 2MASS stars in the field with high S/N ratio. 
It was not possible to observe simultaneously in the optical bands because the 
optical spectrograph ROSS was in maintenance.

[GCN OPS NOTE:  This Circular was delayed 13 hours until daytime
when I could register V.Testa as a new member of the list.]

E. Berger, D.B. Fox, S.G. Djorgovski (Caltech) with T. Treu and M. Malkan
(UCLA) report:

"We obtained three 900-sec spectra of the GRB 040511 afterglow candidate
(GCN 2597
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 ) with the Low Resolution Imaging Spectrometer (LRIS) on the
Keck-I telescope. Inspection of the 2-d spectra reveals two strong
emission lines which we identify as Lyman-alpha and HeII 1640A at a
redshift of 2.63.  We also note a decrease in the continuum flux level
blueward of the line we identify as Ly-alpha, strengthening the
association.  We conclude that this is the likely redshift of the GRB.
The detection of a strong HeII line suggests the presence of a source of
strongly-ionizing photons in the host, e.g. an AGN."

Kenzo Kinugasa (Gunma Astronomical Observatory),
 Ken'ichi Torii (Osaka University), and Mitsuhiro Kohama (RIKEN),
 report;

 The SXC error region of GRB 040511 (HETE trigger #3218, GCN 2588
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 )
 was automatically observed with the GETS system
 of the Gunma Astronomical Observatory, starting at 2004 May 11, 
 15:18:02 UT. The telescope is 25-cm Schmidt Cassegrain
 equipped with unfiltered CCD camera (AP7p).

 After co-adding a set of 15 frames of 30 sec exposures (mean 
 epoch 15:25:52 UT), we compared the image with the USNO A2.0 
 catalog. We found no new source brighter than R=15 mag in the 
 SXC error region. Also, an upper limit of R=15.1 mag is 
 obtained for the afterglow candidate (Fox, et al. GCN 2597
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 ).

D.B. Fox, E. Berger and D. Moon (Caltech), with K. von Braun and
B. Lee (Carnegie), report: 

"We have imaged the SXC localization region for GRB040511 (Dulligan et
al., GCN 2588
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 ) in the J-band with the Dupont telescope + WIRC imager
at Las Campanas Observatory, on two occasions.  Our first-night
imaging consists of 21 minutes' exposure at mean epoch May 12.05 UT
(12.2 hours post-burst) in 1" seeing; our second-night imaging
consists of 15 minutes' exposure at mean epoch May 13.35 UT (43.4
hours post-burst) in 0.75" seeing.

PSF-matched image subtraction of the combined images from these two
nights reveals a single source within the SXC region that fades
significantly between the two epochs, from J~19.0 mag to J~20.9 mag as
referenced to 2MASS photometry of the field.  Since the source is also
observed to fade (by ~1.3 mag) in the contemporaneous (t+11 hour and
t+36 hour, respectively) R-band imaging of Morrell et al. (GCN 2594
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 )
and Chen et al. (GCN 2591
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 ), we conclude that it is a likely afterglow
candidate.  The source coordinates are:

    RA 14:47:49.33,  Dec -44:14:21.8 (J2000)

as referenced to 2MASS catalog astrometry; the uncertainty in this
position is < 0.5".  The image-pixel coordinate position of the
candidate on the first-epoch imaging of Chen et al. (see
http://www.graasp.org/, "DATA" section, file "grb040511_R1.fits") is
X=1214.6, Y=1463.8.

The authors would like to express their gratitude to the the Carnegie
Supernova Program for this allocation of time, and to the GRAASP
collaboration for the public release of their data in FITS format.

D. A. Smith (NSF/U of Michigan) reports on behalf of the ROTSE collaboration:
  
The ROTSE-IIIa telescope (at SSO, Australia) responded rapidly to both the
intitial on-board alert and the final ground analysis alert distributed by
HETE-2 for GRB 040511 (HETE #3218, Dullighan et al., GCN Circ. #2588
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 ).  In both
cases, the first ROTSE-IIIa exposure began within 3.5 s of the alert time
stamp.  The final SXC localization was outside the field of view of the first
series of ROTSE-IIIa images, so those data are not included in this report.
The second series of images began at 15:11:34.57 UTC, ~2.2 h after the burst
trigger time.  The instrument responded automatically with a pre-programmed
sequence of ten 5-s and ten 20-s images, after which it recorded 44 60-s
images.  The first 60 images were co-added in sets of ten, reaching limiting
magnitudes of ~17.2 for the 5-s images and ~17.5 for the others.  (ROTSE-III
images are unfiltered, but calibrated to USNO A2.0 R-band.)  Comparison of
these images to the USNO catalogs and the DSS 2nd Generation R-band image
reveal no new sources.  The detected foreground sources are estimated to cover
~10-15% of the SXC error circle.

In short, ROTSE-IIIa provides the following approximate R-band upper limits
(the first column is the elapsed time to the middle of the co-added exposure):

Time from              Exp. Time            Upper Limit
Burst Trigger
(hours)                 (sec)
2.18                      50                    17.2
2.24                     200                    17.5
2.37                     600                    17.5
2.57                     600                    17.5
2.76                     600                    17.6
2.95                     600                    17.5

GRB 040511: Second Epoch Optical Observations

Nidia Morrell (Las Campanas Observatory), Hsiao-Wen Chen (MIT), Joshua S.
Bloom (Harvard/CfA), Jason X. Prochaska (UCO/Lick), A. Dullighan, G.
Ricker, N. Butler, and R. Vanderspek (MIT):

"We have obtained a second epoch of R-band images of the field around GRB
040511 (Dullinghan et al., GCN #2588
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 ) using the SITe#3 CCD imager on the
40 inch Swope telescope at the Las Campanas Observatory.  The observations
were carried out starting at 01:30 UT 13 May 2004 (~36 hours after the
burst).  Three exposures of 600 sec duration were taken under photometric
and sub-arcsec seeing conditions.  The 5-sigma depth of the stacked image
is R~23.6 mag over a 2"-diameter aperture.

A comparison of the stacked image with the first-epoch images obtained at
~11 hr after the burst (Chen et al., GCN #2591
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 ) shows that none of the
~7100 sources of Rc <~ 23 in the 14.8' x 20' region have variability by
more than 0.25 mag. The few larger-amplitude outliers in the magnitude
(epoch1) vs. magnitude (epoch2) plot are due to detector artifacts."

The magnitude-magnitude plot that shows the comparison of object
photometry obtained from two epochs and all the imaging data are publicly
available at http://www.graasp.org/. Click the "Data" link.

This message may be cited.

J. Gorosabel and  M. Jelinek (IAA-CSIC Granada)
J. Mendez (ING Group, La Palma)
P. Ruiz-Lapuente (Univ. de Barcelona)
J. M. Castro Ceron (STScI, Baltimore)
A. de Ugarte Postigo and A. J. Castro-Tirado (IAA-CSIC)

report:

"We have obtained several exposures covering the HETE/SXC
error box for GRB 040511 (Dullighan et al. GCN 2588
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 ) with the
Prime Focus Camera at the 4.2 m William Herschel telescope
at La Palma.  The images were taking at a considerable airmass
starting on May 11.991--12.022 UT (R-band filter, with a
stacked exposure time of 1800-s). After a visual comparison
with the Digital Sky Survey (DSS-2) red plate, no variable
object is found down to about R = 21 in a ~ 8' x 12' field
around the 3' SXC position."

This message can be cited.

GRB 040511: Optical Observations

Hsiao-Wen Chen (MIT), Nidia Morrell (Las Campanas Observatory), Joshua S.
Bloom (Harvard/CfA), Jason X. Prochaska (UCO/Lick) report on behalf of the
GRAASP (GRB Afterglows as Probes) Collaboration:

"We have obtained optical images of the field around GRB 040511
(Dullinghan et al., GCN #2588
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 ) using the SITe#3 CCD imager and Rc filter
on the 40" Swope telescope at the Las Campanas Observatory.  The camera
has a plate scale of 0.435 arcsec per pixel and covers an 14.7' x 20'
field of view. The observations were carried out starting at 00:15 UT 12
May 2004 (~11 hours after the burst).  Three exposures of 300 sec duration
were taken under photometric conditions.  The 5-sigma depth of the stacked
image is R~23.4 over a 2"-diameter aperture.

A comparison of our stacked image with the DSS/POSS2 red plate shows no
new source to the limit of the plate Rc=20.8."

A finding chart and all the imaging data are publicly available at
http://www.graasp.org/.

This message may be cited.

Brijesh Kumar*, Arti Goyal*, Ram Sagar* and D. Bhattacharya** 
(*  Aryabhatta Research Institute of Observational Sciences, Nainital)
(** Raman Research Institute, Bangalore)

report:

Optical observation of the field of GRB 040511 (HETE trigger #3218,
GCN 2588
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 ) was carried out using a 1k x 1k CCD Camera covering a field of 
6'x 6', mounted on the 104-cm Sampurnanand telescope located at Aryabhatta
Research Institute of Observational Sciences, Manora Peak, Nainital. We
took frames at 20:17 UT on 11 May, 2004 (7.16 hours after the burst) at
large (about 5.4) airmass. We obtained three 300s R band images.

Visual comparison of the combined images with the USNO-A2.0
catalog does not reveal any new source down to a limiting magnitude 
of R ~ 19.5 inside the 2.67 arcmin error circle around the position 
reported by HETE SXC (GCN 2588
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 ). Images can be obtained from the authors
(e-mail: brij@upso.ernet.in).

This message may be cited.

G.Bourban*, D.Naef* **, G.Burki*, F.Carrier* and L.Weber* report:
(*  Geneva Observatory, Switzerland)
(** ESO Santiago, Chile)

We have carried out optical observations of the field of GRB 040511 
(HETE trigger #3218, GCN 2588
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 ) using the C2 CCD Camera (12'x 12') 
mounted on the Swiss 1.2-meter telescope located at the ESO La Silla 
Observatory (Chile), beginning at 22:58 UT on 2004 May 11 (9.93 hours 
after the burst). We obtained four R filtered images, with exposure 
times of 180 and 480 s.

The comparison between these images with the USNO-A2 catalog does not 
reveal any new source down to a limiting magnitude of R < 19.4 inside 
the 80" error circle around the position provided by the HETE SXC Ground 
analysis (GCN 2588
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 ).

This message may be cited.

GRB040511 (=H3218):  A Long GRB Localized by HETE WXM and SXC

A. Dullighan, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb,
and S. Woosley, on behalf of the HETE Science Team;
    
T. Donaghy, E. Fenimore, M. Galassi, C. Graziani, M. Matsuoka,
Y. Nakagawa, T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki,
T. Tamagawa, K. Torii, Y. Urata, T. Yamazaki, Y. Yamamoto,
and A. Yoshida, on behalf of the HETE WXM Team;

N. Butler, G. Crew, J. Doty, G. Prigozhin, R. Vanderspek,
J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga,
R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and
HETE Optical-SXC Teams;

M. Boer, J-F Olive, J-P Dezalay, C. Barraud, and K. Hurley, on behalf
of the HETE FREGATE Team;

report:

At 13:01:46 UTC (46906 s UT) on 11 May 2004, the HETE FREGATE, WXM, and 
SXC instruments detected event GRB040511 (=H3218), a long, bright GRB.

The burst triggered FREGATE in the 30-400 keV energy band.  A flight
localization was distributed automatically 39 minutes after the trigger:
the long delay was due to dropouts in the HETE Burst Alert Network.
Subsequent analysis of the full data set revealed that the prompt WXM
Y location was in error:  the correct WXM localization is a box with 
corners located at

  RA = 14h 47m 30.2s, Dec = -44d 15m 00s
  RA = 14h 48m 43.2s, Dec = -44d 11m 42s
  RA = 14h 49m 09.1s, Dec = -44d 41m 13s
  RA = 14h 47m 55.9s, Dec = -44d 44m 34s (J2000).

Analysis of the SXC data reveal a 90% confidence  error region of 
80" radius (5.6 sq. arcmin area) centered at:

  SXC-Ground:  RA = 14h 47m 50s, Dec = -44d 15' 04" (J2000).

Preliminary analyses of the burst spectrum give a value of Epeak of
~100 keV and a 30-400 keV fluence of ~1e-5 erg/cm2, with a SNR of 32.2 
and a duration (t90) of 38 s.

Details of this burst can be found on the HETE web page at
http://space.mit.edu/HETE/Bursts/GRB040511.

This message can be cited.