GRB 050801
GCN Circular 3723
Subject
GRB 050801: ROTSE-III Detection of Possible Counterpart
Date
2005-08-01T18:34:58Z (20 years ago)
From
Eli Rykoff at U of Michigan/ROTSE <erykoff@umich.edu>
E.S. Rykoff (U Mich), S.A. Yost (U Mich), W. Rujopakarn (U Mich) report
on behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded to GRB 050801 (Swift trigger 148522). The first image was at
18:28:23.9 UT, 21.9 s after the burst (7.9 s after the GCN notice time).
The unfiltered images are calibrated relative to USNO A2.0. We detect a
new object, not visible in the DSS (second epoch), with coordinates:
13:36:35.4 -21:55:42.0 (J2000)
start UT mag mlim(of image)
----------------------------------
18:28:23.9 15.0 17.0
Continuing observations are in progress.
GCN Circular 3724
Subject
GRB050801: GCN XRT position is incorrect
Date
2005-08-01T18:50:03Z (20 years ago)
From
Jamie A. Kennea at PSU/Swift-XRT <kennea@astro.psu.edu>
J.A. Kennea and D.N. Burrows (PSU)
The XRT position sent through GCN for GRB050801 is not correct due to the
XRT centroiding on a artifact in the CCD, and not the afterglow. The
current best position for this from Swift is the BAT position.
[GCN OPS NOTE(01aug05): Per author's request, "050701" was changed to "050801"
in both places.]
GCN Circular 3725
Subject
GRB050801: Swift-BAT detection of a burst
Date
2005-08-01T19:25:50Z (20 years ago)
From
Scott Barthelmy at NASA/GSFC <Scott@lheamail.gsfc.nasa.gov>
D.L. Band (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC),
N. Gehrels (GSFC), C. Gronwall (PSU) S. Hunsberger (PSU),
J. Kennea (PSU), D. Palmer (LANL), M. Perri (ASDC)
on behalf of the Swift team:
At 18:28:02.07 UT, Swift-BAT triggered and located GRB050801 (trigger=148522).
The spacecraft slewed immediately. The BAT on-board calculated location
is RA,Dec 204.139d,-21.950d {+13h 36m 33s,-21d 57' 00"} (J2000), with an
uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The BAT
light curve shows a single FRED structure with a total duration of 3 sec.
The peak count rate was ~900 counts/sec (15-350 keV), which peaks
at ~T+0.5 seconds.
The XRT began observing at 18:29:03 UT, 61 seconds after the BAT trigger.
XRT did centroid on a position, but on-ground examination of the image
revealed that the object found by the centroiding algorithm is a CCD
artifact (Kennea, GCN 3724).
Swift-UVOT began observations of GRB 050801 after the slew, however,
the UVOT dark burst image did not come down via TDRSS so no information
is available at this time. Detailed analysis will be performed
when data is available after the next Malindi pass.
Because of orbit trajectory with respect to the Malindi ground station,
we will not have access to the full data sets to produce the refined analyses
for several hours.
GCN Circular 3726
Subject
GRB 050801: ROTSE-III Early Afterglow Break
Date
2005-08-01T19:50:15Z (20 years ago)
From
Eli Rykoff at U of Michigan/ROTSE <erykoff@umich.edu>
E.S. Rykoff (U Mich), S.A. Yost (U Mich), W. Rujopakarn (U Mich), H.
Swan (U Mich), K. Alatalo (Berkeley), R. Quimby (U Texas) report on
behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, is
observing the optical counterpart to GRB 050801 (Swift trigger 148522,
Band et al, GCN 3725). The early afterglow reported in GCN 3723 is
characterized by a broken power-law, which does not decay significantly
from t+21s to t+200s, followed by a decline with a power law index of
~-1.1. Our preliminary photometry, relative to the USNO A2.0 catalog,
also shows some possible sub-structure to the lightcurve.
tstart-tburst exptime mag
---------------------------------
21.8 5.0 14.99+/-0.06
203.0 20.0 15.01+/-0.03
1590.3 60.0 17.29+/-0.15
GCN Circular 3728
Subject
GRB 050801, afterglow observations
Date
2005-08-01T20:54:15Z (20 years ago)
From
Arne A. Henden at AAVSO <arne@aavso.org>
B. Monard (Bronberg Observatory) reports on behalf
of the AAVSO International High Energy Network:
We observed the afterglow (Rykoff et. al., GCN 3723) for
the Swift burst GRB 050801 (Band et al., GCN 3725), using
the 30cm telescope plus ST-7XME CCD camera of Bronberg
Observatory. Using the UCAC2 star at 13:36:40.87
-21:55:58.6 as having a derived Rc magnitude of 14.5,
we obtain the following photometry:
UT / CR mag
19:03.0 17.5
19:05.5 17.7
19:08.0 17.9
19:10.5 18.1
19:14.5 18.4:
Uncertainty in timing : 30sec absolute, 10 sec relative
Uncertainty in magnitude : 0.3 in accuracy, 0.1 in precision
No further observations are planned.
GCN Circular 3729
Subject
GRB 050801, SMARTS optical/IR afterglow observations
Date
2005-08-02T02:37:50Z (20 years ago)
From
Bethany Cobb at Yale U <cobb@astro.yale.edu>
B. E. Cobb and C. D. Bailyn (Yale), part of the larger SMARTS
consortium, report:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 050801
(GCN 3725, Band et al.) with a mid-exposure time of
2005-08-02 00:01 UT, which is ~5.5 hours post-burst.
Total summed exposure times amounted to 15 minutes in I and V and
12 minutes in J and K.
The afterglow of GRB 050801 (GCN 3723, Rykoff et al.) is
detected in our optical images. However, the afterglow
is not significantly detected in our IR images.
Preliminary photometry, obtained in comparison with
USNO-B1.0 stars, indicates the magnitude of the
afterglow at ~5.5 hours post-burst to be I = 20.2+/-0.2.
The afterglow is not bright enough in the individual optical
frames to significantly measure its decay over our ~40 minutes
of observations.
In comparison with 2MASS stars, the limiting IR magnitudes
are J > 18.6+/-0.2 and K > 17.0+/-0.2.
GCN Circular 3730
Subject
GRB 050801: Swift-BAT refined analysis
Date
2005-08-02T03:50:15Z (20 years ago)
From
Takanori Sakamoto at NASA/GSFC <takanori@milkyway.gsfc.nasa.gov>
T. Sakamoto (GSFC/NRC), C. Markwardt (GSFC/UMD),
L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC),
E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD),
H. Krimm (GSFC/USRA), F. Marshall (GSFC),
D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS),
T. Takahashi (ISAS), J. Tueller (GSFC), on behalf of the Swift-BAT team:
At 18:28:02 UT Swift-BAT detected GRB 050801 (trigger=148522)
(GCN Circ 3725, Band, et al.). The refined BAT ground position
is (RA,Dec) = 204.140, -21.937 [deg; J2000] {13h36m33.6s,-21d59'14.7"}
+-3 arcmin, (95% containment). The partial coding was 99 %.
The light curve shows two peaks which are separated by about 3 seconds.
The second peak is weaker and has a softer spectrum than the first peak.
T90 (15-350 keV) is (20 +- 3) seconds (estimated error including
systematics).
The power law index of the time-averaged spectrum is 2.0 +- 0.2.
The fluence in the 15-350 keV band is (4.4 +- 1.0) x 10^-7 erg/cm2.
The 1-s peak photon flux measured from T0+0.27 second in the 15-350 keV
band is (1.7 +- 0.2) ph/cm2/s. All the quoted errors are at the 90%
confidence level.
GCN Circular 3733
Subject
GRB050801: Swift/UVOT Optical and UV detections
Date
2005-08-02T07:57:28Z (20 years ago)
From
Alexander Blustin at MSSL-UCL <ajb@mssl.ucl.ac.uk>
A. J. Blustin (UCL-MSSL), D. Band (GSFC), S. Hunsberger (PSU),
C. Gronwall (PSU), M. Carter (UCL-MSSL), P. Smith (UCL-MSSL)
on behalf of the Swift/UVOT team report:
The Swift/UVOT began observing the afterglow of GRB050801 at
2005-08-01T18:32:00, 238 s after the BAT trigger (Band et al.,
GCN 3725). The afterglow was detected in all six optical and
UV filters at a position (J2000, corrected to the DSS
coordinates) of:
RA 13:36:35 (+/- 1 arcsec)
DEC -21:55:41 (+/- 1 arcsec)
We give two lightcurve points for each filter in the table
below so that decay slopes may be determined.
Filter T_mid Exp Magnitude
V 244 9.78 15.9 +/- 0.2
V 919 9.77 17.9 +/- 0.8
B 215 9.78 16.0 +/- 0.1
B 890 9.78 18.0 +/- 0.4
U 201 9.78 15.20 +/- 0.09
U 961 9.76 17.2 +/- 0.3
UVW1 187 9.78 15.5 +/- 0.1
UVW1 11316 899.77 20.1 +/- 0.3
UVM2 173 9.78 16.0 +/- 0.2
UVM2 6590 337.06 20.6 +/- 0.9
UVW2 230 9.78 17.4 +/- 0.4
UVW2 4524 670.56 21.0 +/- 0.4
Where Tmid is the midpoint of the exposure post-trigger in seconds.
The magnitudes are based on preliminary zero points, measured in
orbit, and will require refinement with further calibration. All
magnitudes are uncorrected for Galactic reddening.
GCN Circular 3736
Subject
GRB050801: Optical photometry and decay index
Date
2005-08-02T15:01:05Z (20 years ago)
From
Brian Lindgren Jensen at U.of Copenhagen <brian_j@astro.ku.dk>
GRB050801.769: Optical photometry and decay index
J. P. U. Fynbo, B. L. Jensen, J. Hjorth, K. G. Woller, D. Watson
(Niels Bohr Institute), P. Fouque (Obs-MiP, Toulouse), M. I. Andersen
(Potsdam, AIP) report on behalf of the DARK Cosmology Centre:
"We obtained BVR-band imaging of the XRT error circle of
GRB050801.769 (Band et al. GCN#3725, Perri et al. GCN#3731) with
the Danish 1.5m (La Silla) on Aug. 2.0 UT (approx. 6hr after the
burst). We detect the optical afterglow candidate source reported
by Rykoff et al. (GCN#3726), with position (RA, Dec)(J2000.0)
13:36:35.363, -21:55:42.03
Based on a preliminary std. star calibration, we obtain the
following photometry of the afterglow candidate:
Date (UT): Filter: Exptime: Mag.
Aug 1.997 B 600s 22.36+-0.05
Aug 2.012 V 600s 21.03+-0.05
Aug 1.989 R 600s 20.75+-0.04
Aug 2.005 R 600s 20.87+-0.04
Aug 2.020 R 600s 20.94+-0.05
(in this calibration, we obtain B=20.95, V=19.74, R=19.63 for the star
at: (RA, Dec) = (13:36:33.657, -21:55:29.55)).
Fitting a power-law to our three R-band data points gives a lightcurve,
which intersects the R=17.29 ROTSE-III (Rykoff et al. GCN#3726) data
point at t-t0=1590s, to within the errors of that data point.
Including the ROTSE-III data point in the fit, we find an R-band decay
slope of -1.29 +-0.05.
A findingchart of the field is shown at:
http://www.astro.ku.dk/~brian_j/grb/grb050801.769/ "
GCN Circular 3743
Subject
GRB050801: Unchanged decay slope
Date
2005-08-03T10:00:32Z (20 years ago)
From
Brian Lindgren Jensen at U.of Copenhagen <brian_j@astro.ku.dk>
GRB050801.769: Unchanged decay slope
J. P. U. Fynbo, B. L. Jensen, J. Hjorth, K. G. Woller, D. Watson,
J. Sollerman (Niels Bohr Institute), P. Fouque (Obs-MiP, Toulouse),
M. I. Andersen (Potsdam, AIP) report on behalf of the DARK Cosmology
Centre:
"We have obtained additional DK-1.5m R-band imaging (Aug 3.0 UT) of the
optical afterglow (Rykoff et al. GCN#3726) of GRB050801.769 (Band et
al. GCN#3725).
Extending the fit from Fynbo et al. (GCN#3726) yields a smooth
well-fitting power-law from t-t0=0.44h to 29.5h, with an R-band decay
slope of -1.31 +- 0.04.
The lightcurve is shown at:
http://www.astro.ku.dk/~brian_j/grb/grb050801.769/ "
GCN Circular 3762
Subject
GRB050801: Radio Observation
Date
2005-08-04T17:57:34Z (20 years ago)
From
Patrick B. Cameron at Caltech <pbc@astro.caltech.edu>
P. B. Cameron (Caltech) reports on behalf of the Caltech-NRAO-Carnegie
collaboration:
"We observed the field of GRB050801 (GCN 3725) with the Very Large Array
at 8.5 GHz beginning August 2.06 UT. No radio source is detected at the
position of the optical source (GCN 3723) with a 2-sigma upper limit of
60 uJy.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."