Gamma-ray Burst 020813

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE


TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Tue 13 Aug 02 02:48:33 UT
NOTICE_TYPE:    HETE S/C_Alert
TRIGGER_NUM:    2262,   Seq_Num: 1
GRB_DATE:       12499 TJD;   225 DOY;   02/08/13
GRB_TIME:       9859.17 SOD {02:44:19.17} UT
TRIGGER_SOURCE: Trigger on the 25-400 keV band.
GAMMA_RATE:     146  [cnts/s]  on a 1.300 [sec] timescale
SC_-Z_RA:       297 [deg]
SC_-Z_DEC:      -23 [deg]
SC_LONG:        272 [deg East]
WXM_CNTR_RA:    296.630d {+19h 46m 31s} (J2000),
                296.668d {+19h 46m 40s} (current),
                295.900d {+19h 43m 36s} (1950)
WXM_CNTR_DEC:   -19.608d {-19d 36' 27"} (J2000),
                -19.601d {-19d 36' 04"} (current),
                -19.731d {-19d 43' 51"} (1950)
WXM_MAX_SIZE:   28.00 [arcmin] diameter
WXM_LOC_SN:     31 sig/noise (pt src in image)
WXM_IMAGE_SN:   X= 17.4 Y= 20.1 [sig/noise]
WXM_LC_SN:      X= -3.9 Y= 22.7 [sig/noise]
SUN_POSTN:      142.61d {+09h 30m 26s}  +14.75d {+14d 44' 59"}
SUN_DIST:       154.77 [deg]
MOON_POSTN:     199.68d {+13h 18m 44s}   -3.70d {-03d 42' 10"}
MOON_DIST:       95.32 [deg]
MOON_ILLUM:     25 [%]
GAL_COORDS:     20.82,-20.65 [deg] galactic lon,lat of the burst
ECL_COORDS:     294.99,1.55 [deg] ecliptic lon,lat of the burst
COMMENTS:       Probable GRB.
COMMENTS:       WXM error box is circular; not rectangular.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Tue 13 Aug 02 02:48:43 UT
NOTICE_TYPE:    HETE S/C_Last  
TRIGGER_NUM:    2262,   Seq_Num: 2
GRB_DATE:       12499 TJD;   225 DOY;   02/08/13
GRB_TIME:       9859.17 SOD {02:44:19.17} UT
TRIGGER_SOURCE: Trigger on the 25-400 keV band.
GAMMA_RATE:     146  [cnts/s]  on a 1.300 [sec] timescale
SC_-Z_RA:       297 [deg]
SC_-Z_DEC:      -23 [deg]
SC_LONG:        272 [deg East] 
WXM_CNTR_RA:    296.630d {+19h 46m 31s} (J2000),
                296.668d {+19h 46m 40s} (current),
                295.900d {+19h 43m 36s} (1950)
WXM_CNTR_DEC:   -19.608d {-19d 36' 27"} (J2000),
                -19.601d {-19d 36' 04"} (current),
                -19.731d {-19d 43' 51"} (1950)
WXM_MAX_SIZE:   28.00 [arcmin] diameter
WXM_LOC_SN:     31 sig/noise (pt src in image)
WXM_IMAGE_SN:   X= 17.4 Y= 20.1 [sig/noise]
WXM_LC_SN:      X= -3.9 Y= 22.7 [sig/noise]
SUN_POSTN:      142.61d {+09h 30m 26s}  +14.75d {+14d 44' 59"}
SUN_DIST:       154.77 [deg]
MOON_POSTN:     199.68d {+13h 18m 44s}   -3.70d {-03d 42' 10"}
MOON_DIST:       95.32 [deg] 
MOON_ILLUM:     25 [%]
GAL_COORDS:     20.82,-20.65 [deg] galactic lon,lat of the burst
ECL_COORDS:     294.99,1.55 [deg] ecliptic lon,lat of the burst
COMMENTS:       Probable GRB.
COMMENTS:       WXM error box is circular; not rectangular.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Tue 13 Aug 02 04:36:58 UT
NOTICE_TYPE:    HETE Ground Analysis
TRIGGER_NUM:    2262,   Seq_Num: 3
GRB_DATE:       12499 TJD;   225 DOY;   02/08/13
GRB_TIME:       9859.16 SOD {02:44:19.16} UT
TRIGGER_SOURCE: Trigger on the 25-400 keV band.
GAMMA_RATE:     146  [cnts/s]  on a 1.300 [sec] timescale
SC_-Z_RA:       296 [deg]
SC_-Z_DEC:      -23 [deg]
SC_LONG:        272 [deg East] 
WXM_CNTR_RA:    296.661d {+19h 46m 39s} (J2000),
                296.699d {+19h 46m 48s} (current),
                295.931d {+19h 43m 43s} (1950)
WXM_CNTR_DEC:   -19.623d {-19d 37' 22"} (J2000),
                -19.616d {-19d 36' 58"} (current),
                -19.746d {-19d 44' 46"} (1950)
WXM_MAX_SIZE:   8.00 [arcmin] diameter
WXM_LOC_SN:     31 sig/noise (pt src in image)
WXM_IMAGE_SN:   X= 25.0 Y= 25.0 [sig/noise]
WXM_LC_SN:      X= 12.7 Y= 25.0 [sig/noise]
SUN_POSTN:      142.61d {+09h 30m 26s}  +14.75d {+14d 44' 59"}
SUN_DIST:       154.80 [deg]
MOON_POSTN:     199.68d {+13h 18m 44s}   -3.70d {-03d 42' 10"}
MOON_DIST:       95.34 [deg] 
MOON_ILLUM:     25 [%]
GAL_COORDS:     20.81,-20.68 [deg] galactic lon,lat of the burst
ECL_COORDS:     295.01,1.53 [deg] ecliptic lon,lat of the burst
COMMENTS:       Definite GRB.
COMMENTS:       WXM error box is circular; not rectangular.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Tue 13 Aug 02 05:48:35 UT
NOTICE_TYPE:    HETE Ground Analysis
TRIGGER_NUM:    2262,   Seq_Num: 4
GRB_DATE:       12499 TJD;   225 DOY;   02/08/13
GRB_TIME:       9859.16 SOD {02:44:19.16} UT
TRIGGER_SOURCE: Trigger on the 25-400 keV band.
GAMMA_RATE:     146  [cnts/s]  on a 1.300 [sec] timescale
SXC_RATE:       449 [cnts/s]
SC_-Z_RA:       295 [deg]
SC_-Z_DEC:      -23 [deg]      
SC_LONG:        272 [deg East] 
SXC_CNTR_RA:    296.658d {+19h 46m 38s} (J2000),
                296.696d {+19h 46m 47s} (current),
                295.928d {+19h 43m 43s} (1950)
SXC_CNTR_DEC:   -19.588d {-19d 35' 16"} (J2000),
                -19.581d {-19d 34' 52"} (current),
                -19.711d {-19d 42' 40"} (1950)
SXC_MAX_SIZE:   2.00 [arcmin] diameter
SXC_LOC_SN:     12 sig/noise (pt src in image)
SUN_POSTN:      142.61d {+09h 30m 26s}  +14.75d {+14d 44' 59"}
SUN_DIST:       154.80 [deg]
MOON_POSTN:     199.68d {+13h 18m 44s}   -3.70d {-03d 42' 10"}
MOON_DIST:       95.34 [deg]
MOON_ILLUM:     25 [%]
GAL_COORDS:     20.85,-20.66 [deg] galactic lon,lat of the burst
ECL_COORDS:     295.02,1.57 [deg] ecliptic lon,lat of the burst
COMMENTS:       Definite GRB.
COMMENTS:       SXC error box is circular; not rectangular.
COMMENTS:       Burst_Validity flag is true.

finding chart
GCN notice #1470
D.W. Fox and C. Blake (Caltech) with P. Price (RSSA/ANU) report:
"We have observed the localization of GRB020813 (HETE Trigger #2262) with the Oschin/NEAT system for three 120s unfiltered exposures beginning at 13 August 2002 04:37, 04:43, and 04:47 UT. Inspection of the images reveals a star-like object that is not present in DSS images of the region. The coordinates of the object are:
```
    RA 19:46:41.88, Dec -19:36:05.1 (J2000)
```
with a one-sigma uncertainty of 0.5 arcsec in each axis, remaining constant over the time span of our exposures. We suggest that this object is the optical afterglow of GRB020813."
GCN notice #1471
J. Villasenor, C. Graziani, Y. Shirasaki, G. Ricker, D. Lamb, and S. Woosley on behalf of the HETE Science Team;
R. Vanderspek, J. Doty, G. Crew, G. Monnelly, N. Butler, T. Cline, J.G. Jernigan, A. Levine, F. Martel, E. Morgan, G. Prigozhin, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams;
N. Kawai, M. Matsuoka, T. Tamagawa, K. Torii, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, T. Tavenner, and T. Donaghy, on behalf of the HETE WXM Team;
J-L Atteia, M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf of the HETE FREGATE Team;
write:
At 02:44:19.17 UTC (9859.17 s UT) on 13 Aug 2002, the HETE FREGATE, WXM, and SXC instruments detected event H2262, a bright, long GRB. The WXM flight localization was correct and was reported in a GCN Position Notice at 10:50:48 UT, 4 min 14 sec after the burst. Ground analysis of the WXM data for the burst produced a refined location, which was reported in a GCN Position Notice at 04:36:58 UT, 117 minutes after the burst. The WXM location can be expressed as a 90% confidence circle that is 4 arcminutes in radius (due entirely to the systematic error) and is centered at
```
RA = 19h 46m 41s, Dec = -19o 38' 42" (J2000).
```
Ground analysis of the SXC data for the burst also produced a refined location, which was reported in a GCN Position Notice at 05:48:35 UT, 184 minutes after the burst. The SXC location can be expressed as a 90% confidence circle that is 60 arcseconds in radius (due entirely to the systematic error) and is centered at
```
RA = 19h 46m 38s, Dec = -19o 35' 16" (J2000).
```
In the FREGATE 8-40 keV band, the burst had a duration of >125 seconds. In the WXM 2-25 keV band, the burst also had a duration of >125 seconds. The WXM localization SNR was >100. The SXC localization SNR was 12.
Further information (including a light curve) for GRB020812 is provided at the following URL:
http://space.mit.edu/HETE/Bursts/
This message is citable.
GCN notice #1472
Mike Gladders (Carnegie) and Pat Hall (Princeton/Catolica) report:
"We have observed the localization of GRB020813 (HETE Trigger #2262; GCN 1471) with the Magellan Baade 6.5m telescope + TEK5 camera. I-band images taken at 05:46 UT and 06:36 UT confirm the presence of the transient reported by Fox, Blake & Price (GCN 1470) and demonstrate an 0.13 mag fading of the source over this interval. A very rough calibration to USNO-2 magnitudes puts the OT at about I=18. More accurate photometry is underway."
GCN notice #1473
W. D. Li, A. V. Filippenko, and R. Chornock (UC Berkeley) report on behalf of the Lick Observatory and Tenagra Observatory Supernova Search (LOTOSS):
"We have observed a rectangle region of about 10' x 7' around the position of GRB020813 (HETE Trigger #2262) with the 0.8-m Katzman Automatic Imaging Telescope (KAIT) with 21 unfiltered exposures (30s, 120s and 300s) beginning on Aug 13 04:27 UT and lasted until 7:33 UT. Comparison with DSS II images identified the apparent new object reported by Fox, Blake, & Price (GCN #1470), with a precise position measured at RA = 19:46:41.89, Decl. = -19:36:04.5 (J2000). The object is also apparently fading with the following unfiltered magnitudes
```
Aug 13 4.4625 UT, mag 17.75
Aug 13 4.5200 UT, mag 17.77
Aug 13 4.7786 UT, mag 17.82
Aug 13 5.9683 UT, mag 18.10
Aug 13 7.5550 UT, mag 18.42
```
We therefore strongly suggest that this is the afterglow of GRB020813. This photometry sequence is consistent with a power law of index -0.6. A finding chart of the object can be found at http://astron.berkeley.edu/~weidong/grb020813.gif."
This message may be cited.
GCN notice #1474
James Rhoads (STScI), Matthew Holman (CfA), JJ Kavelaars (McMaster), Andrew Fruchter (STScI), and Andrew Levan (STScI) report:
We observed the error circle of GRB 020813 (HETE Trigger #2262) with the CTIO 4m Blanco telescope and Mosaic II imager starting at 020813 04:34 UT (110 minutes after the burst) and continuing for an hour. We obtained a total of ten 300 second images, four in B band and three each in R and I bands. The weather was good with subarcsecond seeing. Preliminary analysis of the first image (a B band frame) confirms the transient reported by Price et al (GCNC 1470). Astrometric calibration using 759 USNO-A2 stars brighter than R=16 places this image on a world coordinate system. We find coordinates of 19:46:41.865 -19:36:04.76 (J2000.0) for the optical transient, with an estimated error of 0.3" on each axis based on the 0.28" RMS residuals of the USNO star positions.
Crude photometric calibration using the blue USNO-A2 magnitudes of three nearby stars gives B=18.6 at 04:36 UT. This B band detection immediately implies an upper limit z < 3.8 to the GRB redshift. (The positions and adopted magnitudes of the reference stars were
```
 19:46:43.477 -19:36:05.66  B=17.10
 19:46:42.729 -19:36:06.65  B=17.20 
 19:46:42.187 -19:35:37.00  B=15.90 .)
```
The third B band image, taken 14 minutes later, shows a decline of 0.07 magnitudes, corresponding to a rough decay slope of -0.55, consistent with that reported by Li et al (GCNC 1473). Analysis of the full data set is underway and will give both refined decay slopes and spectral slopes.
GCN notice #1475
P.A. Price (RSAA, ANU), J.S. Bloom (Harvard/CfA, Caltech), R.W. Goodrich (Keck), A.J. Barth (Caltech), M.H. Cohen (Caltech) and D.W. Fox (Caltech) report:
We have observed the afterglow of GRB 020813 (Fox, Blake & Price, GCN #1470) with LRIS in spectropolarimetry mode on Keck I at Aug 13.31 UT. We identify at an absorption system of Mg II, Mg I, Ca II, Fe II, Mn II at a redshift of z = 1.254 +/- 0.005. We identify a second absorption system at z = 1.222 +/- 0.005, based on Mg II, Mg I, Mn II. We conclude that the redshift of GRB 020813 is z >= 1.254.
This message may be cited.
GCN notice #1476
J. S. Bloom (Harvard/CfA, Caltech), D. W. Fox (Caltech) and M. P. Hunt (Caltech) report:
"Using the Palomar 200 inch + LFC, we observed the afterglow of GRB 020813 (GCN #1470) starting 06:49:50 August 13, 2000 UT, a little over four hours after the GRB trigger (GCN #1471). From that time, until 08:41:03 UT, preliminary photometry indicates that the OT faded by 0.30 +/- 0.02 mag in R(Steidel) band. A power-law decline in flux between these epochs was thus -0.75. Given the shallower decline reported from earlier epochs (-0.55, GCN #1474; -0.6, GCN #1473), the OT may have undergone a temporal break. We note that a break this early in the light curve is typical of high fluence, high energy events such as GRB 020813."
This message may be cited.
GCN notice #1477
A. J. Barth (Caltech), M. H. Cohen (Caltech), R. W. Goodrich (Keck), P.A. Price (RASAA, ANU), J. S. Bloom (Harvard/CfA, Caltech), and D. W. Fox (Caltech) report:
We have observed the afterglow of GRB 020813 (Fox, Blake, & Price, GCN #1470) with the dual-beam LRIS spectropolarimeter on the Keck I 10 m telescope. GCN #1475 discusses absorption features seen in these data. A preliminary reduction of one hour of polarization data reveals significant linear polarization of 3.0% +/- 0.1% at a p.a. of 166 +/- 1 degrees from 3500-5500 Ang., and 2.8% +/- 0.1% at p.a. 158 +/- 1 degrees from 6000-9000 Ang. The fractional polarization is effectively flat and featureless with wavelength and the polarization angle exhibits a slight decrease towards the red.
This message may be cited.
GCN notice #1478
A. Henden (USRA/USNO) and H. Guetter (USNO), on behalf of the USNO GRB Team, report:
We have imaged the field of GRB020813 (GCN 1471), containing the afterglow candidate reported by Fox et al. (GCN 1470). Two Ic-band exposures were made with the USNO 1.55m Strand astrometric telescope, centered at 020813.2974 UT. Rhoads et al. (GCN 1474) reported coordinates using USNO-A2.0; we have independently derived the position of the afterglow candidate using the UCAC2 astrometric catalog. Our position is:
```
  19:46:41.874  -19:36:04.81  (J2000)
```
with an estimated uncertainty of under 50mas in each coordinate.
The 1.0m telescope is undergoing repairs, but should be available starting UT 020815. Our intention is to calibrate this field at UBVRI shortly after this date unless other calibration is published in the interim.
GCN notice #1480
E. Rykoff, D. Smith on behalf of the ROTSE Collaboration, report:
"ROTSE-IIIa responded automatically to GRB020813 (HETE trigger 2262) and started imaging at 13 August 2002 02:48:48.50 UT, 4.48 minutes after the start of the burst, and 15 seconds after receipt of GRB coordinates from the GCN. This response was during early twilight at Los Alamos National Laboratory, and our first several images were saturated by bright sky. Our first usable exposure, 60 seconds in duration beginning at 03:02:36.28, shows no optical transient to an unfiltered limiting magnitude ~ 16.0 under adverse conditions. Our typical limit is several magnitudes deeper. This limit is around 0.5 magnitude brighter than the extrapolation of the decay of the OT as reported by Li, et. al. (GCN circular 1473)."
This message may be cited.
GCN notice #1482
K. Hurley, on behalf of the Ulysses and HETE GRB teams,
T. Cline, on behalf of the Ulysses, HETE, and Konus-Wind GRB teams,
E. Mazets and S. Golenetskii, on behalf of the Konus-Wind GRB team,
I. Mitrofanov, D. Anfimov, A. Kozyrev, M. Litvak and A. Sanin, on behalf of the HEND/Odyssey GRB team,
W. Boynton, C. Fellows, K. Harshman, C. Shinohara and R. Starr, on behalf of the GRS/Odyssey GRB team, and
G. Ricker, J-L Atteia, N. Kawai, D. Lamb, S. Woosley, J. Doty, R. Vanderspek, J. Villasenor, G. Crew, G. Monnelly, N. Butler, J.G. Jernigan, A. Levine, F. Martel, E. Morgan, G. Prigozhin, J. Braga, R. Manchanda, G. Pizzichini, Y. Shirasaki, C. Graziani, M. Matsuoka, T. Tamagawa, K. Torii, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, T. Tavenner, T. Donaghy, M. Boer, J-F Olive, and J-P Dezalay, on behalf of the HETE GRB team, report:
Konus-Wind and Mars Odyssey-HEND observed this burst (HETE 2262, GCN 1471). (Ulysses data are being downlinked and should become available within several hours). The triangulation annulus is centered at RA, Decl(2000) = 322.225, -16.080, and has a radius of 24.559 +/- 0.040 degrees. The center line of this annulus lies approximately 28 arcseconds from the optical transient reported by Fox et al. (GCN 1470). Further refinements to this triangulation are possible. This localization is consistent with, and constrains, the HETE WXM error circle; although it does not constrain the HETE SXC position, it serves as a good calibration for the IPN, which should ultimately allow us to constrain systematic uncertainties.
A map will be posted shortly at ssl.berkeley.edu/ipn3/020813.
GCN notice #1483
K. Hurley and T. Cline, on behalf of the Ulysses, Konus, and HETE GRB teams,
E. Mazets and S. Golenetskii, on behalf of the Konus-Wind GRB team,
I. Mitrofanov, D. Anfimov, A. Kozyrev, M. Litvak and A. Sanin, on behalf of the HEND/Odyssey GRB team,
W. Boynton, C. Fellows, K. Harshman, C. Shinohara and R. Starr, on behalf of the GRS/Odyssey GRB team, and
G. Ricker, J-L Atteia, N. Kawai, D. Lamb, S. Woosley, J. Doty, R. Vanderspek, J. Villasenor, G. Crew, G. Monnelly, N. Butler, J.G. Jernigan, A. Levine, F. Martel, E. Morgan, G. Prigozhin, J. Braga, R. Manchanda, G. Pizzichini, Y. Shirasaki, C. Graziani, M. Matsuoka, T. Tamagawa, K. Torii, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, T. Tavenner, T. Donaghy, M. Boer, J-F Olive, and J-P Dezalay, on behalf of the HETE GRB team, report:
Ulysses, Mars Odyssey-HEND, HETE-FREGATE, and Konus-Wind observed this GRB (HETE 2262). As observed by Ulysses, it had a duration of approximately 125 seconds, a 25-100 keV fluence of approximately 3.8E-05 erg/cm2, and a peak flux of approximately 1.2E-06 erg/cm2 s over 0.50 seconds.
We have triangulated it to a preliminary, 3 sigma error box whose approximate area is ~ 33. sq. arcmin. and whose coordinates are:
```
    RA(2000)                              DEC(2000)
 ERROR BOX CENTER:  19 h 46 m 38.65 s    -19 o 37 '   7.79 "
 ERROR BOX CORNER 1: 19 h 46 m 40.11 s    -19 o 34 '  48.69 "
 ERROR BOX CORNER 2: 19 h 46 m  4.26 s    -19 o 43 '  49.28 "
 ERROR BOX CORNER 3: 19 h 47 m 13.28 s    -19 o 30 '  24.23 "
 ERROR BOX CORNER 4: 19 h 46 m 37.21 s    -19 o 39 '  26.80 "
```
This error box restricts both the HETE WXM and SXC error circles given in GCN 1471, and is consistent with the position of the OT reported in GCN 1470. A map will be posted shortly at ssl.berkeley.edu/ipn3/020813. For clarity, the Mars Odyssey-Konus annulus reported in GCN 1482 has been omitted from the map.
This error box may be improved.
GCN notice #1484
G. Masi, F. Mallia and U. Tagliaferri (Campo Catino Astronomical Observatory, Italy) report:
On Aug. 13.859 2002 UT, we imaged the field of GRB020813 (GCN 1471) with our 0.8-m, f/8 reflector + CCD, assuming the position provided by Henden et al. (GCN 1478). We find the optical afterglow candidate (Fox, et al., GCN 1470) to be clearly visible, with an R magnitude (based on USNO A2.0) around 19.5. The astrometry, using about 200 reference stars from USNO A2.0, gives the following position:
```
  RA= 19 46 41.89  Decl: -19 36 04.6 (J2000.0)
```
Mean residuals= 0.2" in both axes.
The image will be available later today at our website: web.tiscalinet.it/aoccsite
The photometry will be improved when secondary standards become available.
GCN notice #1485
Y. Urata (1,2), T. Miyata (3), S. Nishiura (3), Y. Nakata (3), T. Aoki (3), T. Soyano (3), K. Tarusawa (3), H. Mito(3), A. Yoshida (1,4), T. Tamagawa (1)
1: RIKEN, 2: Titech, 3: Tokyo Univ. 4:AGU
We have observed the optical transient (OT) of GRB020813 (Fox, Blake & Price, GCN #1470) with the KISO observatory 1.05 m Schmidt telescope. We obtained four data sets for each B,V,R,I band during 2002 Aug. 13 10:52 to 16:46 UT.
We detected the OT in the first data set of B (11:58-12:17 UT) , R(10:52-11:11 UT), I (11:14-11:33 UT). Due to the bad weather condition, we could not detect it in V band. A preliminary analysis suggests that the OT is at R=19 in comparison with the USNO-A2.0 star (U0675_34232257). Analysis of the full data set is underway.
These images can be found at http://cosmic.riken.go.jp/urata/GRB/GRB020813/ .
This message may be cited.
GCN notice #1487
Millimeter observations of GRB 020813
The burst has been observed with the IRAM Plateau de Bure Interferometer in a five-antenna compact configuration from August 13, 21:13 UT to August 14, 00:58 UT under good meteorological conditions, on the position given in GCN 1474 : (EQ 2000) 19:46:41.865 -19:36:04.76 . The source was not detected.
Results of UV plane fits fixed on the phase center:
```
Frequency       Flux and 1 sigma error            Beam size
----------------------------------------------------------------------
 89.188 GHz :  -0.13 (+-0.37) mJy/beam    15.6" by 6.5" at PA -158 deg
232.032 GHz :  -0.63 (+-2.06) mJy/beam     6.5" by 2.6" at PA   27 deg
```
No other source was detected above the 3 sigma level within the half-power width of the primary beams (55.5" at 89.188 GHz and 31.3" at 232.032 GHz).
Michael Bremer (IRAM) and Alberto J. Castro-Tirado (IAA-CSIC)
GCN notice #1488
U. Kiziloglu, A. Alpar, A. Baykal, S. Y. Kaan, A. Ankay, (METU); O. Huseyin, (AU); O. Terekov, R. Sunyaev, A. Tkachenko, D. Denissenko, (IKI); I. Bikmaev, N. Sakhibullin, V. Suleymanov, (KSU); I. Khamitov, (TUG) reports:
We have observed the optical transient (OT) of GRB020813 (HETE Trigger #2262; GCN 1471) with TUG's (TUBITAK National Observatory, Turkey) RTT150 1.5m telescope and SDSU camera on 13th August 2002, with 1.0 arcsec seeing.
We also confirm the presence of the transient reported by Fox, Blake & Price (GCN 1470).
A combined image of eight R-band exposures (sums up to 24 minutes) centered at 20:40 UT (almost 18 hours after the event) gives R=20.0+/-0.2, using USNO-A2 magnitude estimates. Analysis of the full data set is underway.
Combined image can be found at: http://astroa.physics.metu.edu.tr/GRB020813/
GCN notice #1490
D. A. Frail (NRAO) and E. Berger report on behalf of the Caltech-NRAO-CARA GRB collaboration:
"On 2002, August 14.36 UT we made a short observation toward the optical afterglow candidate reported by Fox et al. (GCN 1470). We detect a 0.3 mJy radio source coincident with the position of the optical source. Further observations with the VLA are planned."
GCN notice #1491
W. D. Li, R. Chornock, and A. V. Filippenko (UC Berkeley) report on behalf of the Lick Observatory and Tenagra Observatory Supernova Search (LOTOSS; see IAU Circ. 7906):
"We have obtained additional observations of the optical afterglow of GRB020813 with the 0.8-m Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory. We continue to detect the object first reported by Fox et al. (GCN 1470) and also observed by us (GCN 1473). An unfiltered observation (600 s) obtained at 14 Aug 04:36 UT shows an extended object at the position of the afterglow. Another image (600 s unfiltered) obtained at 06:56 UT under better conditions shows two unresolved objects at that position separated by about 3.7". We identify one of these objects with the fading GRB afterglow, and suggest that the other object is a possible host galaxy (although it could be an unrelated faint object). We measured the following unfiltered magnitudes, in addition to those reported in GCN 1473:
```
13 Aug 8.3542 UT, mag 18.55 +/- 0.05
14 Aug 4.5972 UT, mag 20.55 +/- 0.25 (host?+GRB)
14 Aug 6.9333 UT, mag 21.08 +/- 0.30 (GRB only) host? = 20.70 +/- 0.25.
 
```
We note that the first and third observations imply a power-law decay index of about -1.44. This is substantially steeper than the decay rate implied by the early observations (GCN 1473, 1474), supporting the hypothesis of Bloom et al. (GCN 1476) that the object may have undergone a temporal break."
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GCN notice #1492
G.G.Williams (Steward Observatory), C.Blake (CalTech/Princeton), Dieter Hartmann (Clemson), and the S-LOTIS collaboration report:
The error box of GRB020813 (HETE Trigger 2262, GCN 1471) was observed in R band with the 0.6m Super-LOTIS telescope, located at Kitt Peak, beginning at 4.42 UT on August 13, 2002. In total, 110 individual 60s images were taken. By coadding the first 9 images, taken between 4.42 and 4.62 UT, the OT reported by Fox et al. (GCN 1470) was detected at the 3 sigma level. This represents the earliest detection of the OT through a standard photometric filter. Using F band photographic magnitudes from the GSC2.2, the magnitude of the OT was determined by comparison to several nearby stars. We report an R band magnitude of 18.38+/-0.38 at UT 4.51. This magnitude is consistent with a decay slope of approximately -1 to the later-time R band data reported by Masi (GCN 1484), Urata et al. (GCN 1485), and Kiziloglu et al. (GCN 1488). Analysis of the rest of the S-LOTIS data is in progress.
```
=========================================
OT 19:46:41.874 -19:36:04.81 (J2000)
=========================================
R=18.38+/-.38 at UT 4.51 August 13, 2002. 
=========================================
```
GCN notice #1494
GRB020813(=H2262): Revised Localization with HETE Soft X-ray Camera (SXC)
J.G. Jernigan, R. Vanderspek, J. Villasenor, G. Monnelly, J. Doty, G. Crew, N. Butler, T. Cline, A. Levine, F. Martel, E. Morgan, G. Prigozhin, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Optical-SXC and HETE Operations Teams;
G. Ricker, J-L Atteia, N. Kawai, D. Lamb, and S. Woosley on behalf of the HETE Science Team;
Y. Shirasaki, C. Graziani, M. Matsuoka, T. Tamagawa, K. Torii, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, T. Tavenner, and T. Donaghy, on behalf of the HETE WXM Team;
M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf of the HETE FREGATE Team;
write:
Analysis of the full data set derived from the HETE Soft X-ray Camera (SXC) has resulted in a revised location for GRB020813(=H2262; Villasenor et al, GCN Circular #1471). The revised SXC location can be expressed as a 90% confidence circle that is 50 arcseconds in radius (due entirely to systematic errors) and is centered at:
```
  RA = 19h 46m 41.8s, Dec = -19o 35' 39" (J2000)
 
```
We conclude that the Fox et al (GCN Circular #1470) afterglow candidate for GRB020813 lies 26 arcseconds from the SXC location, well within the error circle reported here.
Further information regarding GRB020813 is provided at the following URL: http://space.mit.edu/HETE/Bursts/
This message is citable.
GCN notice #1495
Mike Gladders (Carnegie Observatories) and Pat Hall (Princeton/Catolica) report:
"Baade 6.5m (Magellan I) observations with the TEK5 camera of the field of GRB020813 acquired on the nights of August 13 and 14, starting at 13 August 5.76583 UT, do not show any evidence for extended emission coincident with the OT position. The OT first reported by Fox et al. (GCN 1470) and confirmed as fading by us (GCN 1472) is detected as a point source in all available images. In the best-seeing late-time images, detailed below, the PSF of the OT is indistinguishable in all filters from that of other nearby point sources of similar magnitude. In these excellent seeing images, the nearest object is a star 3".86 almost due N of the OT, and presumably the possible associated object reported in GCN 1491. This star has a similar magnitude in I to the OT, but is much redder, and has a fainter companion of similar color 0".99 away that could cause it to appear extended in more typical ground-based images."
```
Filter  Start UT        Int. Time       Seeing
I       14 Aug 1.0761   60 sec          0".305
R       14 Aug 1.2364   60 sec          0".304 
V       14 Aug 1.3653   60 sec          0".352
B       14 Aug 1.2064   60 sec          0".396
```
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GCN notice #1497
F. Bertoldi (MPIfR Bonn), D.A. Frail (NRAO), A. Weiss (IRAM Granada), K.M. Menten (MPIfR Bonn), S. Kulkarni (Caltech), E. Berger (Caltech) report:
The afterglow of GRB 020813 (Fox et al., GCN 1470) was observed at 250 GHz (1.2 mm) with the 37 channel Max-Planck Millimeter Bolometer (MAMBO) array (80 GHz bandwidth, 10.7 arcsec HPBW) at the IRAM 30 m telescope on Pico Veleta (Spain), at the position reported by Rhoads et al. (GCN 1474).
The observation dates, average elevations, 250 GHz zenith opacities, on-sky integration time, and (1/rms^2 weighted) average flux densities are listed in the following table:
```
date    UT           EL   tau_z  t_int  flux [mJy]
-----------------------------------------------------
Aug 13, 19:10-21:10  32d   0.50  2950s  1.45 +-1.15
Aug 14, 23:10-23:55  31d   0.39  1260s  1.08 +-1.39

                         total:  4210s  1.30 +-0.89
```
Given the high line of sight opacity we were not able to detect the GRB afterglow at sufficient significance. Our flux density limits are consistent with those found by Bremer et al. (GCN 1487) at 232 GHz, -0.63 +-2.06 mJy.
This message may be quoted.
GCN notice #1498
S. Covino, D. Malesani, G. Ghisellini, P. Saracco, G. Tagliaferri, F. Zerbi (Observ. of Brera, Milan, Italy); S. Di Serego, A. Cimatti, M. Della Valle (Observ. of Arcetri, Florence, Italy); F. Fiore, G.L. Israel, L. Stella (Observ. of Monte Porzio, Rome, Italy); M. Vietri (Univ. Rome 3, Italy); N. Kawai (Tokyo Tech, Japan); D. Lazzati (IoA, Cambridge, UK); S. Ortolani (Univ. of Padua, Italy); L. Pasquini (ESO, Germany); G. Ricker (MIT, USA); E. Le Floch, P. Goldoni, F. Mirabel (CEA, France) report:
We observed the optical counterpart to GRB020813 (Villasenor et al., GCN 1471; Fox, Blake & Drake, GCN 1470) between August 13.994 and August 14.148 (22.9 to 24.8 hours after the GRB trigger). The observations were performed with the ESO VLT-3 (Melipal) telescope equipped with FORS1 with a Bessel V band filter in the imaging polarimetry mode. The transient source is clearly detected in the acquisition image.
We found linear polarization at the level of P = (1.17 +/- 0.16)% with position angle (158 +/- 4) degrees (uncertanties are 1-sigma errors).
Once we also remove the effect of ISM in our Galaxy measuring the polarization of field stars, the intrinsic polarization of the optical transient turns out to be P = (0.80 +/- 0.16)% and P.A.= (144 +/- 6) degrees.
The detected polarization level is significantly lower (~6 sigma) than the previous one measured by Barth et al. (GCN 1477) at UT 13.31 while the position angle remains constant to within the errors.
This is therefore the most significant and larger degree of variability ever detected in the polarization level of a GRB optical afterglow and confirms that the detected polarization is related to the afterglow emission and not induced by intervening matter.
Such a degree of variability is predicted in current models for beamed afterglows (Ghisellini & Lazzati, 1999, MNRAS, 309, L7) and allows us to predict that the jet break occurred ~one day after the GRB event. According to these models, the polarization angle should then rotate by 90 degrees and reach a peak up to ~10% around Aug 17.0 UT. Further polarization measurements are strongly urged to test such models.
This message is citeable.
GCN notice #1500
D. Malesani and S. Covino (INAF, Merate Obs., Milan), D. Fugazza and R. Barrena (TNG), E. Pian and N. Masetti (IASF/CNR, Bologna), on behalf of a larger collaboration, report:
We observed the optical counterpart of GRB 020813 on Aug 13.99, 15.04 and 16.03 UT, using the VLT and TNG telescopes and a standard Bessel V filter. The source is clearly detected and it shows a fading by 1.04 +/- 0.05 magnitudes between the first and the second epoch, and by 0.62 +/- 0.10 magnitudes between the second and third epoch. The afterglow is hence decaying with time according to a sharply defined power-law with a slope of delta = -1.4 +/- 0.02.
The break in the decay suggested in GCN #1476 (Bloom, Fox & Hunt) and #1491 (Li, Chornock & Filippenko) is therefore confirmed.
Complete analysis of the photometric data is underway.
This message can be cited.
GCN notice #1501
T. Kawabata (BAO), Y. Urata (Titech / RIKEN), H. Yamaoka (Kyushu U) report:
We have obtained 36 R band images (each exposure time 60 seconds) of the afterglow of GRB020813 (Fox, Blake & Price, GCN #1470) with the Bisei Astronomical Observatory (BAO) 1.01-m telescope during 2002 Aug. 13 11:44 to 12:40 UT. A combined image of all exposures gives R = 19.35 +/- 0.13 using r magnitudes of near USNO_A2.0 stars as photometric references.
A combined image can be found at http://www.town.bisei.okayama.jp/bao/astro/grb/grb020813.jpg
This message may be cited.
GCN notice #1502
S. Covino, D. Malesani, G. Ghisellini, P. Saracco, G. Tagliaferri, F. Zerbi (Observ. of Brera, Milan, Italy); S. Di Serego, A. Cimatti, M. Della Valle (Observ. of Arcetri, Florence, Italy); F. Fiore, G.L. Israel, L. Stella (Observ. of Monte Porzio, Rome, Italy); M. Vietri (Univ. Rome 3, Italy); N. Kawai (Tokyo Tech, Japan); D. Lazzati (IoA, Cambridge, UK); S. Ortolani (Univ. of Padua, Italy); L. Pasquini (ESO, Germany); G. Ricker (MIT, USA); E. Le Floch, P. Goldoni, F. Mirabel (CEA, France) report:
In GCN 1498 we claimed that the polarization measurements performed by Barth et al. (GCN 1477) and our group on the GRB 020813 afterglow allow to single out "the most significant and larger degree of variability ever detected in the polarization level of a GRB optical afterglow".
However, according to the result of Bersier et al. (astro-ph/0206465) a large amount of variability in the polarization level could have been present in GRB 020405 if compared to the polarization level measured again by our own group (Covino et al., GCN 1431).
In this case, the measurements performed for GRB 020813 are only a confirmation for the large variability in a short time scale (~24 hours) in the polarization level of a GRB optical afterglow.
GCN notice #1503
A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:
We have acquired UBVRcIc all-sky photometry for an 11x11 arcmin field centered at the optical transient coordinates for GRB020813 (Villasenor et al. GCN 1471; Fox et al. GCN 1470) with the USNOFS 1.0-m telescope on one photometric night. Stars brighter than V=14.0 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/grb020813.dat The astrometry in this file is based on linear plate solutions with respect to UCAC2. The external errors are less than 100mas.
While the night was photometric, the extinction was high due to nearby forest fires. The GRB field is towards our southern horizon and so there is a greater risk of zeropoint errors due to nonuniform smoke. We estimate the present zeropoint errors to be about 0.03mag. The current calibration also has a brighter limiting magnitude than normal due to the moonlit sky. We will be extending this calibration fainter and with additional nights to ensure against a systematic zeropoint error. You should check the dates on the .dat file prior to final publication to get the latest photometry.
GCN notice #1504
GRB020813: Fading X-ray Afterglow Observed with Chandra
R. Vanderspek, H. L. Marshall, P. G. Ford, and G. R. Ricker (MIT Center for Space Research)
report:
Beginning at August 13.990 (t[burst] + 21.02 hr) and continuing until August 14.892 (t[burst] + 42.67 hr), Chandra High Energy Transmission Grating Spectrometer (HETGS) observations were conducted of a field centered on the optical afterglow candidate (Fox et al, GCN1470) for GRB020813, which was accurately localized by both the HETE WXM and SXC instruments (Villasenor et al, GCN1471; Jernigan et al, GCN1494). We have detected a moderately bright, fading X-ray afterglow consistent in position with the optical source (Henden et al, GCN1478). Over the 76.8 ksec of data accumulation (livetime) for the Chandra observations, the mean counting rate was 0.19 counts/s (summed over the dispersed signal from the HEG and the MEG gratings, and including the 0th order flux). The source we detected faded in brightness according to a power law, with a decay time slope of -1.42 +/- 0.05. (This value is remarkably close to the decay slope values near -1.4 being reported for the afterglow of GRB020813 in the optical; e.g. Malesani et al, GCN1500, and references therein.) The source spectrum we derive from our preliminary analysis of the dispersed HETGS counts is characterized as follows:
nH = 7 x 10^20 cm^(-2), consistent with the anticipated galactic absorption in the source direction;
dN/dE = A * E^ (-gamma) ph cm^(-2) s^(-1) keV^(-1) , over the 0.6-6 keV range, with A = 0.00051, and gamma = 1.75
Thus, the mean flux for the 0.6 to 6 keV band over the duration of the Chandra observation was ~2.2 x 10^(-12) ergs cm^(-2) s^(-1).
Our analyses are continuing, and more detailed results will be posted at:
http://space.mit.edu/HETE/
We thank Harvey Tananbaum for his generous allocation of Director's Discretion Time to this observation, and the Chandra X-ray Observatory Operations personnel for the impressive promptness with which this observation was planned and carried out.
The preliminary results reported here may be cited.
GCN notice #1505
A. Di Paola (1), A. Arkharov (2), V. Larionov (3), L. A. Antonelli (1)
1) Rome Astronomical Observatory (IT) 2) Pulkovo Observatory (RU) 3) St.Petersburg University (RU)
on the behalf of the GROAR Team, report:
We have imaged the GRB020813 OT (GCN 1471) from the Campo Imperatore Observatory both with the 60cm Schmidt telescope at optical wavelengths and with the 1.1 meters AZT-24 telescope at NIR wavelengths.
Observations started on 2002-08-13 19:50:00 UT and ended the same day on 23:52:00 UT, respectively 16.1 and 21.1 hours after the burst.
The extremely low elevation (always between 2 and 3 airmasses) and the consequent poor seeing conditions allow us to barely distinguish between the OT and the double star located about 3.8" to the North (see U. Kiziloglu et al. GCN 1488, W. D. Li et al. GCN 1491, M. Gladder et al. GNC 1495). For this reason the following magnitudes have to be considered lower limits until we will complete the subtraction of the field components.
We obatined V, R, I, J and K images at:
```
2002-08-13 19.42 V-band: OT ~ 19.90 +- 0.20
2002-08-13 19.77 R-band: OT ~ 18.85 +- 0.20
2002-08-13 20.49 I-band: OT ~ 19.90 +- 0.20
2002-08-13 21.61 R-band: OT ~ 19.70 +- 0.20
2002-08-13 22.88 V-band: OT ~ 20.35 +- 0.20
2002-08-13 23.38 I-band: OT ~ 20.15 +- 0.20
```
and a continuous repetition of J and K images starting from 18.83 up to 23.88 UT.
We extimated the color indexes between optical and NIR bands:
```
  V-J ~ 1.3 +- 0.5 
  V-K ~ 3.1 +- 0.5 
```
and the magnitudes at J and K to be about 18.8 and 17.0 respectively.
The magnitudes calibration is obtained from A. Henden GCN 1503 for the optical points and from 2MASS catalog for the infrared points.
The refined analysis is underway.
GCN notice #1513
Mike Gladders (Carnegie Observatories) and Pat Hall (Princeton/Catolica) report:
"A total of 37 images (16 in I, 10 in R, 11 in V) of the OT associated with GRB020813 were acquired with the Baade 6.5m (Magellan I) telescope and TEK5 camera on the night of August 13 UT, under conditions of excellent seeing and transparency. A further 15 images (5 in I, 4 each in BR and 2 in V) were acquired on the night of August 14 UT, under similar conditions, though with some possible cirrus.
"A preliminary analysis of these images yields the magnitudes below for the OT associated with GRB020813. Magnitudes have been computed differentially relative to approximately 20 stars straddling the magnitude range of OT, located in the same field (2x2 arcminutes). Internal uncertainties (estimated from residuals in the differential corrections) are about 0.01 magnitudes on August 13 UT, and about 0.02 on August 14UT, and the systematic uncertainty in the calibration of the zero-points is less than 0.05 magnitudes in most cases. The B-band zero-point, established on August 14 UT, may be affected by light cirrus on the science frames, and is questionable."
```
August 13 UT:
-------------

I-band:
-------
 UT     Magnitude


 5.7742 17.910
 5.8922 17.928
 6.6153 18.061 
 6.7461 18.090
 6.7733 18.108 
 6.7986 18.078
 6.8236 18.106
 6.8486 18.104
 7.0036 18.139
 7.2939 18.192
 7.4225 18.208
 7.5400 18.249
 7.5650 18.241
 7.5900 18.233
 7.6153 18.228
 7.6403 18.273

R-band:
-------
 UT     Magnitude
 6.7061 18.491
 6.9122 18.520
 6.9422 18.536 
 7.1478 18.578
 7.1728 18.579 
 7.1978 18.582
 7.2228 18.591
 7.3222 18.608
 7.3925 18.625
 7.5083 18.654
 
V-band: 
------- 
 UT     Magnitude
 6.6767 18.850
 6.8836 18.882
 6.9739 18.916
 7.0400 18.922
 7.0653 18.930
 7.0906 18.929
 7.1156 18.932
 7.2614 18.953
 7.3592 18.982 
 7.4508 19.000
 7.4781 18.999 
 
 
August 14 UT: 
------------- 
 
I-band: 
------- 
 UT     Magnitude
 1.0033 19.854
 1.0344 19.862
 1.0594 19.837
 1.0844 19.891
 1.1094 19.848

R-band: 
------- 
 UT     Magnitude
 1.2447 20.420
 1.2697 20.411 
 1.2947 20.420
 1.3197 20.419
 
V-band:
-------
 UT     Magnitude
 1.3486 20.805
 1.3736 20.811
 
B-band: 
------- 
 UT     Magnitude
 1.1397 21.365
 1.1647 21.315
 1.1897 21.343
 1.2147 21.338
```
GCN notice #1514
Mike Gladders (Carnegie Observatories) and Pat Hall (Princeton/Catolica) report:
"The photometric data reported previously by us yield the following decay slopes for the OT of GRB020813. The decay slopes in various filters implied by the data from August 13UT are:
```
    I: -0.677+-0.016 (all data August 13UT)
    I: -0.76+-0.03 (only UT>6.5, to match R&V time range)
    R: -0.82+-0.06
    V: -0.75+-0.05
```
"These data are consistent with the same power law decay in all three filters in the time interval 6.5 "Also, the data yield decay slopes between August 13 and 14 UT of -0.96+-0.04,-1.02+-0.01,-1.01+-0.02 in I,R and V respectively. These values lie midway between the early time slope (above, and GCN #1476), and the later time slope of -1.4+-0.02 (August 13.99 UT to August 16.03 UT, GCN #1500). The slope derived here is nominally inconsistent with the decay reported in GCN #1491 (-1.44) over a time window similar to the data reported here. However, allowing for the uncertainties of the three data points in GCN #1491 yields a decay slope of -1.3+-0.30, consistent with the results reported here.
"It thus appears that the decay slope of this OT has continued to steepen with time, rather than having undergone a simple break."
GCN notice #1518
A.J. Levan, A.S. Fruchter, I. Burud and J.E. Rhoads (STScI) report for the larger GOSH collaboration:
The field containing the optical counterpart of GRB 020813 was imaged by HST using ACS/HRC, ACS/WFC and NICMOS on 17th August beginning at 04:00 UT approximately 98 hours after the burst.
The optical counterpart is clearly visible in our images. Using the zeropoints for the filters on ACS/WFC, as given below, we find the magnitude of the counterpart to be:
```
FILTER    Z_P(AB) OT MAG(AB)
==========================
F435W     25.47     23.20
F606W     26.35     22.71
F814W     25.86     22.33
```
This is consistent with a spectral slope of beta =-0.8.
Comparing to early, 3 hour I Band observations (GCN 1513) gives an approximate slope of ~t^-1.07. Comparing to observations taken after 23 hours (also GCN 1513) indicates a somewhat faster (broken) slope of t^-1.35.
The OT appears largely point like, however a PSF subtraction reveals some evidence for a possible 25th magnitude host galaxy underlying the OT.
Images of the field of GRB 020813 may be found at
http://www.stsci.edu/~fruchter/GRB/020813
Analysis is continuing and further observations are planned.
GCN notice #1519
Mike Gladders (Carnegie Observatories) and Pat Hall (Princeton/Catolica):
On the basis of previous experience with the public release of GRB data taken by us at LCO (GCN #1209), we have decided to release the Baade 6.5m (Magellan I) data taken of GRB 020813 on the nights of August 13 and 14 UT for general use by the community. We anticipate that this high-quality data, which provides several hours of early photometry of the burst under sub 0".5 seeing conditions, will be of use to a number of researchers. As before, we anticipate that appropriate collaboration(s) will evolve as circumstances dictate. Meanwhile, the pre-processed data, including a README file detailing observing conditions and preliminary zeropoints for the images, can be downloaded by anonymous ftp from:
ftp.ociw.edu
pub/gladders/GRB/GRB020813
Raw science frames, as well as extensive calibration data can be provided if necessary; please contact Mike Gladders (gladders@ociw.edu) to arrange for this.
GCN notice #1524
F. Fiore, S. Savaglio (also JHU), L.A. Antonelli, A. Fontana, G. Marconi, L. Stella, A. Di Paola, G. Stratta, G. Israel (INAF-OAR), S. Covino, G. Chincarini, G. Ghisellini, P. Saracco, F. Zerbi (INAF-OABrera), D. Lazzati (Cambridge, UK), R. Perna (CfA), M. Vietri (Univ. Roma Tre), F. Frontera (Univ. di Ferrara), S. Mereghetti (CNR-IASF), E.J.A. Meurs (Dunsink Obs.) and N. Kawai (Titech, RIKEN) report:
"Starting on August 13 2002 23:32 UT we have obtained high resolution (R=40,000, 7.5 km/s in the observer frame) spectra of the optical afterglow of GRB020813 (Fox et al., GCN #1470) using UVES at VLT/Kueyen. This resolution is 4 times better than the best resolution obtained so far for GRB OT spectra, confirming that this kind of observations is capable to map accurately the kinematics and metallicities of medium-high redshift galaxies. Observations consisted of 3 exposures, for a total of 7,700 seconds, covering the full spectral range 3500-9800 Angstrom, in good seeing conditions (better than 1"). At the time of the observations the afterglow magnitude was R=20.4 and V=20.8 (see Gladders & Hall, GCN #1513).
A preliminary reduction of the spectra is already revealing the very rich and complex structure of the ISM in the putative GRB host galaxy. Strong absorption lines of MgI2852, MgII2803, MgII2796, FeII2344, FeII2374, FeII2382 at a mean redshift of z = 1.2545 are clearly detected (see Price et al., GCN #1475), spanning a total velocity range of up to about 400 km/s. Several narrow components are resolved down to a width of a few tens of km/s."
This message may be cited
GCN notice #1528
G.Beskin, A.Birjukov, S.Koposov, O.Spiridonova (SAO) and A.Pozanenko (IKI) report:
We have observed the OT of GRB020813 reported by D. Fox et al. (GCN 1470) with Zeiss-1000 telescope of Special Astrophysical Observatory (SAO). Three R-band images (exposure of each 303 sec) were taken on August 13 between 18:43 - 19:05 UT.
Using combined image of the 3 exposures and calibration data provided by A. Henden (GCN 1503) we obtained R magnitude of 19.70 +/- 0.25.
The combined image may be found at http://grb.rssi.ru/GRB020813
```
=================================
R=19.70 +/- 0.25 at UT 18.72 August 13, 2002
=================================
```
This message may be cited.
GCN notice #1651
J. Gorosabel* (IAA-CSIC, Granada), J.P.U. Fynbo* (Univ. of Aarhus),=20 J. Hjorth, H. Pedersen, B.L. Jensen (Univ. of Copenhagen), =20 S.T. Holland* (Notre Dame), J.M. Castro Cer=F3n* (ROA, San Fernando),=20 M. Andersen (AIP, Potsdam), A.J. Castro-Tirado (IAA-CSIC, Granada)=20 report:
We have imaged the GRB 020813 (GCN 1471) optical afterglow (GCN 1470) with the 1.54-m Danish Telescope (+DFOSC) as follows:
```
  Date              Filter Seeing   Exp.Time  Time Since   Mag
  (UT)                      (")       (s)     GRB (days)
 -------------------------------------------------------------------
 10.01-10.13/10/2002  R     1.0   2x1200+8x900  58.0    23.90+/-0.14
 09.02-09.17/10/2002  B     1.7     10x1200     57.0    24.46+/-0.19=20
 -------------------------------------------------------------------
```
The calibration is based on the photometric standards given in GCN=20 1503. The B-R colour of our measurements (B-R=3D0.56+/-0.24) is bluer than the ones reported for the afterglow to date (constant around B-R ~ 1, see GCN 1513).
This "blueing" could be due to a change of spectral slope in the=20 afterglow or the presence of an underlying blue host galaxy.
Given the epoch of our observations (~60 days after the gamma-ray=20 event) we consider the second possibility more likely. The=20 faintness of our detection does not allow us to see any extended structure.
Two gifs of the potential host galaxy can be seen at:
http://www.dsri.dk/~jgu/grb020813/GCN/grb020813R.gif http://www.dsri.dk/~jgu/grb020813/GCN/grb020813B.gif
-----------------------------------------------------
* Visitors at the Copenhagen University Observatory.
Barth et al (astro-ph/0212554)
astro-ph/0511669 from 23 Nov 2005
Sato: HETE-2 Localization and Observations of the Gamma-Ray Burst GRB 020813
A bright, long gamma-ray burst (GRB) was detected and localized by the instruments on board the High Energy Transient Explorer 2 satellite (HETE-2) at 02:44:19.17 UTC (9859.17 s UT) on 2002 August 13. The location was reported to the GRB Coordinates Network (GCN) about 4 min after the burst. In the prompt emission, the burst had a duration of approximately 125 s, and more than four peaks. We analyzed the time-resolved 2-400 keV energy spectra of the prompt emission of GRB 020813 using the Wide Field X-Ray Monitor (WXM) and the French Gamma Telescope (FREGATE) in detail. We found that the early part of the burst (17-52 s after the burst trigger) shows a depletion of low-energy photons below about 50 keV. It is difficult to explain the depletion with by either synchrotron self-absorption or Comptonization. One possibility is that the low-energy depletion may be understood as a mixture of ``jitter'' radiation the usual synchrotron radiation component.

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Jochen Greiner, last update: 28-Nov-2005 [Disclaimer]