GRB 050525
GCN Circular 3466
Subject
GRB 050525: Swift Detection of a Bright, Possibly Short Burst
Date
2005-05-25T01:36:14Z (20 years ago)
From
David L. Band at NASA/GSFC <dband@lheapop.gsfc.nasa.gov>
D. Band (GSFC/UMBC), J. Cummings (GSFC/NRC), M. Perri
(ASDC), S. Holland (GSFC/USRA), D. N. Burrows (PSU), N.
Gehrels (GSFC), J. E. Hill, J. A. Kennea, S. Hunsberger
(PSU), C. Markwardt (GSFC/UMD), D. Palmer (LANL) on behalf
of the Swift Team.
At 00:02:53 UT, the BAT instrument on the Swift spacecraft
triggered (trigger=130088) and located GRB 050525. The BAT
on-board calculated location is RA,Dec 278.144 , +26.340
(18h 32m 35s +26d 20' 23") (J2000) with an uncertainty of 3
arcmin (radius, 3-sigma, including systematic uncertainty).
This is a very bright burst, yielding about 1500 counts
over background in 64 ms (preliminary) in the 25-100 keV
range in the BAT instrument. This would correspond to a
rate of 10 counts/sec/cm2 in that 64 ms interval, but the
peak rate in a later interval may be greater. Although
light curves are not yet available, the BAT rate trigger
continued to evaluate different timescales while data from
the first 64 ms was being imaged. The merit parameters
indicate that the highest significance rate trigger is for
a 1 second interval, consistent with a short burst. More
details will be available after the full data pass.
The XRT was pointed promptly at the burst and took an image
at 00:04:58 UT (125 s after the BAT burst trigger). The
XRT found a bright X-ray source near the center of the
field of view, with position RA(J2000) = 18h 32m 32.3s
Dec(J2000) = +26d 20' 17.5" We estimate an uncertainty of
about 6 arcseconds radius (90% containment). This position
is 31 arcseconds from the BAT position and 8 arcseconds
from the ROTSE position (Rykoff et al, GCN 2465).
We caution that the XRT is in the middle of engineering
tests and is in an unusual mode. While the X-ray afterglow
looks unusually strong, there are also indications that the
XRT instrument configuration is abnormal due to the tests
being performed.
The XRT position is outside of the UVOT-TDRSS image.
Analysis of the UVOT data will take place after the next
full data pass.
This is a bright burst that appears to be in the short
category; the Sun and moon angles are conducive for optical
observations. Followup observations are strongly
encouraged.
GCN Circular 3467
Subject
GRB 050525 - Very Bright, Not Short
Date
2005-05-25T02:14:26Z (20 years ago)
From
Craig Markwardt at NASA/GSFC/UMD <craigm@milkyway.gsfc.nasa.gov>
C. Markwardt (GSFC/UMD), S. Barthelmy (NASA/GSFC), L. Barbier (GSFC),
J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (UMD), H. Krimm (GSFC/USRA), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS),
M. Suzuki (Saitama), J. Tueller (GSFC)
on behalf of the Swift-BAT team:
GRB 050525 (Swift trigger 130088) was observed by Swift BAT. At the
present, only rate data are available. This initial data indicate
that the burst was very intense (peak rate of 80,000 ct/s above
background). The light curve consists of at least two ragged peaks,
with a total duration of approximately 10 seconds (15 - 200 keV).
Thus, this is not a short burst as initially speculated (Band et
al. GCN #3466), but it is one of the brightest bursts of the year.
GCN Circular 3468
Subject
GRB050525: ROTSE-III Refined Analysis
Date
2005-05-25T04:09:26Z (20 years ago)
From
Eli Rykoff at U of Michigan/ROTSE <erykoff@umich.edu>
E.S. Rykoff (U Mich), S.A. Yost (U Mich), H. Swan (U Mich), R. Quimby (U
Texas), report on behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site in Namibia, and ROTSE-IIId at
the Turkish National Observatory in Turkey responded automatically to
Swift GRB 050525 (GCN 3466, 3467). Our first 5-s exposure from
ROTSE-IIIc begain at 00:08:56.7 UT; the response in Turkey was delayed
approximately 30 minutes due to bad weather. The images in Namibia were
affected by clouds passing through the images.
We confirm the fading nature of the afterglow reported in GCN 2465. The
afterglow is well detected in images from both ROTSE-IIIc and
ROTSE-IIId. The afterglow is 9" (3 pixels) from a 17.2 magnitude USNO
star, which affected our initial position estimate. The revised
position is:
18:32:32.6 +26:20:23.5 (J2000)
with an uncertainty of ~1". We note that this is 7.2" from the XRT
position reported by Band et al (GCN 2465).
We have measured the afterglow flux with our PSF fitting software and
have found that the early lightcurve is fading with a slow power-law
decline with index ~-0.5, with a peak of 15.1+/-0.1 at 601s post-burst.
The images are unfiltered and calibrated relative to USNO B1.0 R-band
magnitudes. This bright afterglow with a slow decline should still be
bright for follow-up spectroscopy.
An image of the afterglow and burst field from ROTSE-IIId is available at:
http://www.rotse.net/grb_reports/050525_btab.html
GCN Circular 3469
Subject
GRB 050525: observatons of the optical afterglow
Date
2005-05-25T04:29:31Z (20 years ago)
From
Daniele Malesani at SISSA-ISAS,Trieste,Italy <malesani@sissa.it>
D. Malesani (SISSA), S. Piranomonte, F. Fiore (INAF/OARm), G.
Tagliaferri, D. Fugazza (INAF/OABr), and R. Cosentino (INAF/TNG), report
on behalf of a larger collaboration:
We imaged the field of the bright GRB 050525 (Band et al., GCN 3466;
Markwardt et al., GCN 3467) with the Italian 3.6m TNG. Observations were
performed under good observing conditions (seeing ~1.1"), even if close
to the bright Moon.
The object reported by Rykoff et al. (GCNs 3465, 3468) is clearly
detected in a single R-band image (2 min exposure) starting on 2005 Apr
25.07138 UT, 1.7 h after the GRB. Based on several nearby USNO stars,
its magnitude is R ~ 17.4. We thus confirm the fading behaviour of this
object.
This message can be cited.
GCN Circular 3470
Subject
GRB 050525: Optical observation
Date
2005-05-25T04:44:38Z (20 years ago)
From
Ken ichi Torii at RIKEN <torii@crab.riken.go.jp>
K. Torii (Osaka U.) and Matt BenDaniel (http://Slooh.com) report:
"The error region of the bright GRB 050525 (Band et al. GCN 3466;
Markwardt et al. GCN 3467) was observed with the Slooh 14 inch f/6.3
telescope at Observatorio del Teide in the Canary Islands.
The observation started at 2005 May 25, 00:50 UT (47 minutes after
the burst) and a 30 s exposure in each of red, green, and blue filter
was obtained. We stacked the three frames and compared it with the DSS
frames.
As a result of the preliminary analysis, we note a 3.3-sigma
enhancement at position
(R.A., Dec.) = (18:32:32.65 +26:20:24.5) (J2000, 1.3" uncertainty)
with R~16.6 (USNO-A2.0 magnitude).
This is 8".4 away from the Swift XRT position (GCN 3466) while it agrees
with the refined position (Rykoff et al. GCN
3468) for the optical afterglow candidate (Rykoff et al. GCN 3465)."
GCN Circular 3471
Subject
GRB 050525, infrared observations
Date
2005-05-25T08:55:01Z (20 years ago)
From
Peter Garnavich at U of Notre Dame <pgarnavi@nd.edu>
J. Rosenberg (CfA) and P. Garnavich (Notre Dame)
We imaged the field of GRB 050525 (Band et al. GCN 3466)
and the optical afterglow reported by Rykoff et al. (GCN 3465)
with the 1.2m telescope of the Fred Whipple Observatory
and Stelircam infrared imager. Imaging in J and K' began
on May 25.22 (UT). Quick reduction of the K' data shows
a new source not visible in the 2MASS K image at 18:32:32.61
+26:20:22 +/-1.0" (J2000) based on the USNO A-2.0 catalog.
This is in agreement with the position provided by
Rykoff et al. (GCN 3468) and Torii & BenDaniel (GCN 3470)
given their quoted errors. The brightness is roughly K'=14.
This message may be cited.
GCN Circular 3472
Subject
INTEGRAL detection of GRB 050525
Date
2005-05-25T09:16:08Z (20 years ago)
From
Sandro Mereghetti at IASF/CNR <sandro@mi.iasf.cnr.it>
D. Gotz, S. Mereghetti (IASF, Milano), N. Mowlavi, S. Shaw, M. Beck (ISDC,
Versoix), J. Borkowski (CAMK, Torun) on behalf of the IBAS Localization
Team and N. Lund (DSRI, Copenhagen) on behalf of the ISWT report:
Offline analysis of the IBAS data showed that GRB 050525 discovered by
Swift (Band et al. GCN 3466, Markwardt et al. GCN 3467), has been detected
also by the IBIS/ISGRI instrument on board INTEGRAL.
The burst occurred at an off-axis angle of 14.7 degrees, very close to the
edge of the IBIS/ISGRI field of view, and illuminated through the coded
mask only 6% of the detector surface.
The preliminary value of the peak flux is 33 photons (3.2E-6 ergs)/cmsq/s
(1 sec integration time, 20-200 keV).
Owing to a small gap caused by telemetry saturation, we can only derive a
lower limit on the fluence of 144 photons (1.2E-5 ergs)/cmsq (12 s
integration time, 20-200 keV).
A plot of the multi peaed light curve is posted at:
http://ibas.mi.iasf.cnr.it/IBAS_Results.html
This message can be cited.
GCN Circular 3473
Subject
GRB 050525: TAROT observations of the early afterglow
Date
2005-05-25T10:01:39Z (20 years ago)
From
Jean-Luc Atteia at Lab d Astrophys.,OMP,Toulouse <atteia@ast.obs-mip.fr>
Klotz, A. (CESR-OMP), Boer M. (OHP), and Atteia, J.L. (LAT-OMP) report:
We imaged the entire field of GRB 050525 detected by SWIFT (Band et al. GCNC 3466)
with the TAROT robotic telescope (D=25cm) located at the Calern observatory,
France. Observations started at 00:08:52s UT, 4 seconds after the GCN notice,
and 6 min after the GRB. The field had an elevation of 62 degrees
above horizon at the begining of the observations.
The afterglow reported by Rykoff et al. (GCNC 3465) is clearly seen
in TAROT images, with a magnitude R=15.1, 6 minutes after the GRB,
and R=17.1, 108 minutes after the GRB. The unfiltered TAROT images are
calibrated relative to R-band magnitudes in the USNO A1 Catalog.
Further information, including a light-curve of the afterglow
during the first two hours after the GRB can be found at the following address:
http://www.cesr.fr/~klotz/grb050525/
This notice can be cited.
GCN Circular 3474
Subject
Konus-Wind observation of GRB 050525
Date
2005-05-25T11:28:56Z (20 years ago)
From
Valentin Pal'shin at Ioffe Inst <val@mail.ioffe.ru>
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and
T. Cline on behalf of the Konus-Wind team report:
A long bright GRB 050525 (Swift-BAT trigger=130088: GCN 3466,3467)
triggered Konus-Wind at 176.704 s UT (00:02:56.704).
As observed by Konus-Wind, it had a duration of ~11.5 s,
fluence (7.84 +/- 0.06)10-5 erg/cm2,
peak flux on 16-ms time scale (8.7 +/- 0.7)10-6 erg/cm2 s
(both in the 20 keV - 1 MeV energy range).
In ~2800 s after trigger, Konus-Wind detected
even more intense burst. Because it was detected
during data readout, only time history in the G2
window (74-295 keV) with 3-s time resolution is available.
It had a duration of ~20 s and fluence 25100 counts in
74-295 keV energy range (the fluence of the trigger burst
was 8500 counts in the same energy range). Assuming
it had the same spectrum as the trigger burst,
the energy fluence can be estimated as ~2.3x10^-4 erg/cm2.
Whether the second burst relates to the first one
or it is different GRB accidentaly registered close to
the trigger burst can be clarified by data
from other instruments
(but the chance to register two very bright bursts so close
to each other seems to be poor).
The time-integrated spectrum of the GRB 050525
is well fitted by a power law with
exponential roloff model:
dN/dE ~ E^alpha exp(-E/E0)
with alpha = -1.10 +/- 0.05,
and E0 = 93.6 +/- 5.3 keV.
The peak energy Ep = 84.1 +/- 1.7 keV.
GCN Circular 3475
Subject
Swift/UVOT UV and optical detections of GRB 050525
Date
2005-05-25T12:29:37Z (20 years ago)
From
Alexander Blustin at MSSL-UCL <ajb@mssl.ucl.ac.uk>
S. Holland (GSFC), D. Band (GSFC/UMBC), A. Blustin,
S. Rosen (MSSL), P. Roming (PSU), P. Schady (MSSL/PSU),
K. Mason (MSSL), C. Gronwall (PSU), A. Breeveld (MSSL),
T. Poole, C. James, K. McGowan, M. de Pasquale (MSSL)
S. Hunsberger, C. Pagani, P. Brown, M. Ivanushkina (PSU),
B. Hancock, T. Kennedy (MSSL), P. Broos, S. Koch (PSU),
P. Smith, H. Huckle (MSSL), M. Still, P. Boyd,
W. Landsman (GSFC), J. Nousek (PSU), N. Gehrels (GSFC)
on behalf of the Swift UVOT team.
Swift/UVOT has detected GRB 050525 in all of its UV and
optical filters. Using data from 65 seconds after the
burst, we obtain the following magnitudes from images
summed between the T_start and T_stop times in the table:
Filter Magnitude Exp (s) T_start T_stop
V 14.97 +/- 0.02 287 65 1292
B 16.53 +/- 0.03 188 224 1084
U 15.32 +/- 0.03 98 90 979
UVW1 15.63 +/- 0.04 98 196 2046
UVM2 15.75 +/- 0.06 98 182 952
UVW2 16.62 +/- 0.05 188 952 1189
Where T_start and T_stop are in seconds after the
trigger (Band et al. GCN 3466).
The magnitudes are based on preliminary zero-points,
measured in orbit, and will require refinement with
further calibration.
GCN Circular 3476
Subject
GRB 050525: pseudo-redshift
Date
2005-05-25T12:50:03Z (20 years ago)
Edited On
2025-04-09T18:43:39Z (2 months ago)
From
Jean-Luc Atteia at Lab d Astrophys.,OMP,Toulouse <atteia@ast.obs-mip.fr>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Tyler Barna at University of Minnesota <tylerpbarna@gmail.com>
J-L. Atteia & A. Pelangeon (LAT-OMP) report:
Taking into account the spectral parameters of GRB 050525
provided by Golenetskii et al. (GCNC 3474), we have computed
its pseudo-redshift, using the method described in Atteia, 2003, A&A, 407, L1.
We find a pseudo-redshift pz=0.36 +/- 0.1
We thank S. Golenetskii et al. for quickly providing
the spectral parameters of this GRB.
This notice can be cited.
GCN Circular 3478
Subject
GRB050525: Optical observations
Date
2005-05-25T14:07:59Z (20 years ago)
From
Aaron Price at AAVSO <aaronp@aavso.org>
D. T. Durig (Cordell-Lorenz Observatory, University of the South), A. Oksanen
(Nyrola Observatory), C. Pullen (AAVSO) and A. Price (AAVSO) report on behalf of
the AAVSO International High Energy Network on optical observations of GRB050525
(GCN #3466; Band et al.):
An afterglow candidate is found at the location reported by Rykoff et al. (GCN
#3468) and Band et al. (GCN #3465). At 08:13 UT it is detected at an unfiltered
magnitude of 18-19 (fading over 100 mins centered on 08:13UT). The USNO star near
18 32 34.5 +26 20 24 can not completely be resolved from the afterglow candidate.
Full details and FITS image URL is below.
Name: Dr. Douglas T. Durig
email: ddurig@sewanee.edu
Observer: Dr. D. T. Durig ( CLW01)
Site: Cordell-Lorenz Observatory
Location: Sewanee, Tenn., USA
LatitudeLongitude: 35 12 N 85 55 W
Elevation: 600 m
Scope: SCT 0.30 m
ScopeFocalRatio: f/5.8 1765 mm
CCDVendor: SBIG STL-1001E
CCDDetector: KAF 1001E
CCDSize: 1024x1024
CCDPixelScale: 2.8
CCDFOV: 48x48 full, 12x12 quarter frame cropped
Object: GRB050525
ObsDate: 2005 05 25
ObsMidPointTime: 08 13 25
TimePerFrame: 120 sec
NumberOfFrames: 75
Filters: CR
Processing: dark, flat, register, co-add, 1/4 frame crop
Seeing: 5-6 arc sec
LimitingMag: 19.5-20 ???
Sky: very clear but breezy with Bright Moonlight
afterglowmag: 18-19
afterglowerr: 1
compstars: 1300 UCAC ref stars in full frame
Report: The USNO star near 18 32 34.5 +26 20 24 can not completely be resolved
from the afterglow candidate, but I do see it fade by around 1 mag over a little
over 100 min by summing a series of 30 consecutive 120 sec exposures. I get a
measured position of 18 32 33.9 +26 20 23 and 18 mag at 7:23 UT falling to 19 mag
at 9:03 UT, but this includes some contribution from the USNO star.
comments: UT dec.day CR mag
7:23:28 25.30796 18.0
7:40:09 25.31955 18.2
7:56:43 25.33105 18.3
8:13:25 25.34265 18.3
8:30:10 25.35428 18.3
8:46:49 25.36584 18.6
9:03:28 25.37741 19.0
A FITS image has been uploaded to
ftp://ftp.aavso.org/grb/Dr.DouglasT.Durig_GRB050525_2453516.00275_.fits
The AAVSO thanks the Curry Foundation for their continued support of the
AAVSO International High Energy Network.
GCN Circular 3481
Subject
GRB 050525: BART optical observation
Date
2005-05-25T18:21:49Z (20 years ago)
From
Martin Jelinek at Inst.Astrophys.Andalucia,Granada <mates@asu.cas.cz>
Martin Jelinek (IAA CSIC Granada, Spain),
Petr Kubanek, Martin Nekola and Rene Hudec
(ASU AV CR Ondrejov, Czech Republic)
report:
The robotic telescope BART located at Astronomical Institute
in Ondrejov, Czech Republic, observed the errorbox of the
GRB050525 (Band et al. GCN 3466, Markwardt et al. GCN 3467,
Cummings et al. GCN 3469) with it's Wide-field camera. First
exposure started 18s after issuing the GCN alert (and 6m13s
after the GRB onset). Co-add of first ten minutes of
observation reveals the OT reported by Rykoff et al. (GCN
3468) at the detection limit of the image, which is V=15.5
according to our callibration made against GSC-1.2.
GCN Circular 3484
Subject
GRB 050525, spectral lag pseudo-redshift
Date
2005-05-25T22:19:26Z (20 years ago)
From
Jay Norris at NASA-GSFC/LHEA <jnorris@lheapop.gsfc.nasa.gov>
J. Norris, S. Barthelmy, N. Gehrels (GSFC), J. Cummings (GSFC/NRC),
D. Band (GSFC/UMBC), L. Barbier (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), A. Parsons (GSFC), J. Tueller (GSFC)
Analysis of the Swift/BAT light curves, between channels
100-350 keV and 25-50 keV, yields an estimate of the spectral
lag of 0.124 +- 0.006 seconds for GRB 050525 (GCN 3466, Band
et al.; (GCN 3479, Cummings et al.).
Assuming the lag-luminosity relation (Norris et al. 2000, ApJ,
534, 248), using the Band model spectral parameters measured
during the 1-second peak of the burst's light curve --
alpha = -1.0, beta = -8.9, Epeak = 79 keV, and the 1-second
peak flux, 48 photon/cm^2/s, 15-350 keV --
we estimated a spectral-lag pseudo redshift of z = 0.72 +- 0.15,
in broad agreement with the spectroscopic redshift, z = 0.606,
reported by Foley et al. (GCN 3483).
Uncertainty in the high-energy spectral shape, and the difference
between the BATSE and BAT bandpass dependences of the lag-luminosity
relation on peak flux, combine to require the error of order
delta_z = 0.15.
GCN Circular 3485
Subject
GRB050525: Super-LOTIS observations
Date
2005-05-26T00:23:27Z (20 years ago)
From
Peter A. Milne at super-LOTIS <pmilne@as.arizona.edu>
P.A.Milne, G.G.Williams (Steward Obs), H.-S.Park (LLNL),
on behalf of the Super-LOTIS GRB team report:
We observed the field of GRB 050525 (SWIFT trigger 130088)
starting at UT=06:02:41 (05:59:48 after the burst),
with the 0.6m Super-LOTIS telescope at Kitt Peak, AZ.
We obtained 20 x 30-sec images in each of the R,V and I
filters. Observing conditions were affected by thin clouds
in addition to the bright moon.
Inspection of the three resulting co-added images reveals no source brighter
than our limitting magnitude at the location of the candidate
optical counterpart first reported by Rykoff et al. (GCN 3465,3468).
Comparisons were based upon the DSS2 image and the afterglow finders
provided by the ROTSE-III and TAROT collaborations.
We report upper limits of:
filter <UT> upper limit
R 06:16 17.5
V 06:47 17.5
I 07:18 18.0
These values can be compared with the unfiltered detections reported by
Durig et al. (GCN 3478).
The upper limits are based upon three stars in the USNOB catalog,
1163-0325237, 1163-0325216, 1163-0325240.
This message may be cited.
GCN Circular 3486
Subject
GRB 050525 : Lulin optical afterglow observations
Date
2005-05-26T07:00:28Z (20 years ago)
From
Kuiyun Huang at IANCU <d919003@astro.ncu.edu.tw>
GRB 050525 : Lulin optical afterglow observations
P.S. Chiang (NCKU), K.Y. Huang, W.H. Ip (NCU), Y. Urata(RIKEN),
Y. Qiu (BAO), Y.Q. Lou (THCA) on behalf of EAFON report:
" We have imaged the GRB 050525 optical afterglow position reported by
Rykoff et al.(GCN 3468) and Torii et al. (GCN 3470) using 1.0-m
telescope at Lulin Observatory, Taiwan. The afterglow was detected at
LOT images. The R band magnitude of afterglow is about 21.3 +/-0.1
around 17.74 hours after burst ( exposure time 300sec x 4) which
compared with USNOB-1.0 stars.
Further analysis are in progress. This message may be
cited."
GCN Circular 3489
Subject
GRB 050525: MITSuME Optical Observation in VRI
Date
2005-05-26T15:49:41Z (20 years ago)
From
Nobuyuki Kawai at Tokyo Tech <nkawai@hp.phys.titech.ac.jp>
K. Yanagisawa (OAO/NAOJ), H. Toda, and N. Kawai (Tokyo Tech) report on
behalf of the MITSuME collaboration:
"We observed the field of GRB 050525 (Band et al.; GCN 3466) with the
3-color MITSuME 50cm Telescope at Okayama, Japan starting at 12:03(UT)
on May 25, 2005. We obtained a 5400 sec exposure (120 sec x 45 frames;
midtime=13:02 UT) simultaneously in V, R, and I-bands. We confirmed
the optical afterglow (Rykoff et al.; GCN 3465) in R and I bands at
the position
RA=18:32:32.6, DEC=+26:20:22 (J2000)
with magnitudes R = 19.30 +/- 0.17 and I = 20.12 +/- 0.29. We did not
detect the optical transient in the V-band image with an upper limit
of V=19.2."
GCN Circular 3493
Subject
GRB 050525: RTT150, Optical observations
Date
2005-05-27T15:44:50Z (20 years ago)
From
Irek Khamitov at TUG <irekk@tug.tug.tubitak.gov.tr>
Z. Aslan, I. Khamitov, T. Ozisik, K. Uluc (TUG), U. Kiziloglu (METU),
I. Bikmaev, N. Sakhibullin (KSU/AST), A. Alpar (SabUni),
A.Yaskovich, R.Burenin, M. Pavlinsky, R. Sunyaev (IKI),
report:
We have observed the field of OT of GRB 050525 (Rykoff et al, GCN3465)
with 2k*2k Andor CCD attached to the Russian-Turkish 1.5-m telescope
(Bakirlitepe, Turkey) in VRc bands.
We made series of 5*90s exposures in V, starting at 00:22UT May 26,
and 20*60s exposures in Rc, starting at 01:18 UT May 26.
On 20 co-added R-images we clearly see the OT at the position
RA = 18:32:32.57 (2000.0), DEC=+26:20:22.5 (2000.0)
based on the USNO-B1 catalog, its uncertainty is about 0.1 arcsec.
We estimate m_R magnitude of OT using USNO-B1 as 21.76+/-0.17
corresponding to the midtime of 25.5 hours after the burst.
This message may be cited.
GCN Circular 3855
Subject
GRB050525, GRB050607, GRB050802 BVRcIc field photometry
Date
2005-08-22T15:26:26Z (20 years ago)
From
Arne A. Henden at AAVSO <arne@aavso.org>
A. Henden (AAVSO/USNO) reports on behalf of the USNO GRB Team:
We have acquired BVRcIc all-sky photometry for 23x23arcmin
fields centered on the coordinates of recent GRB localizations
with the USNOFS 1.0-m telescope on 1 or 2 photometric nights
but with bright moonlight and variable seeing. Stars brighter
than V=12.0 are saturated and should be used with care. We have
placed the photometric data on our anonymous ftp site:
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050525.dat
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050607.dat
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050802.dat
The astrometry in these files is based on linear plate solutions
with respect to UCAC2 or USNO-A2.0. The external errors are usually
200mas or better. The estimated external photometric error is
about 0.03mag. Some fields are relatively crowded, and the
large apertures required to handle the variable seeing also
blended some measurements, so choose comparison stars wisely.
We have one additional night for GRB050525 that will be
added when reductions are complete.
As always, you should check the dates on the .dat file prior to
final publication to get the latest photometry. There is
a README file on the ftp directory to give you information
about the procedures used to calibrate these fields.