Gamma-ray Burst 030528

(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:    Wed 28 May 03 13:03:26 UT
NOTICE_TYPE:    HETE S/C_Alert 
TRIGGER_NUM:    2724,   Seq_Num: 1
GRB_DATE:       12787 TJD;   148 DOY;   03/05/28
GRB_TIME:       46982.83 SOD {13:03:02.83} UT
TRIGGER_SOURCE: Trigger on the 25-400 keV band.
GAMMA_RATE:     153  [cnts/s]  on a 1.300 [sec] timescale 
SC_-Z_RA:       276 [deg]
SC_-Z_DEC:      -15 [deg]
SC_LONG:        122 [deg East] 
SUN_POSTN:       64.97d {+04h 19m 52s}  +21.45d {+21d 26' 43"}
MOON_POSTN:      36.34d {+02h 25m 22s}  +12.32d {+12d 19' 12"}
MOON_ILLUM:     6 [%]
COMMENTS:       Probable GRB.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Wed 28 May 03 13:03:40 UT
NOTICE_TYPE:    HETE S/C_Update
TRIGGER_NUM:    2724,   Seq_Num: 2
GRB_DATE:       12787 TJD;   148 DOY;   03/05/28
GRB_TIME:       46982.83 SOD {13:03:02.83} UT
TRIGGER_SOURCE: Trigger on the 25-400 keV band.
GAMMA_RATE:     153  [cnts/s]  on a 1.300 [sec] timescale 
SC_-Z_RA:       276 [deg]
SC_-Z_DEC:      -15 [deg]
SC_LONG:        122 [deg East] 
WXM_CNTR_RA:    255.859d {+17h 03m 26s} (J2000),
                255.911d {+17h 03m 39s} (current),
                255.106d {+17h 00m 25s} (1950)
WXM_CNTR_DEC:   -22.802d {-22d 48' 07"} (J2000),
                -22.807d {-22d 48' 24"} (current),
                -22.733d {-22d 43' 56"} (1950)
WXM_MAX_SIZE:   60.00 [arcmin] diameter
WXM_LOC_SN:     7 sig/noise (pt src in image)
WXM_IMAGE_SN:   X= 7.7 Y= 1.5 [sig/noise]
WXM_LC_SN:      X= 13.0 Y= 2.2 [sig/noise]
SUN_POSTN:       64.97d {+04h 19m 52s}  +21.45d {+21d 26' 43"}
SUN_DIST:       169.77 [deg]
MOON_POSTN:      36.34d {+02h 25m 22s}  +12.32d {+12d 19' 12"}
MOON_DIST:      140.98 [deg] 
MOON_ILLUM:     6 [%]
GAL_COORDS:     359.82,11.29 [deg] galactic lon,lat of the burst
ECL_COORDS:     256.98,0.00 [deg] ecliptic lon,lat of the burst
COMMENTS:       Probable GRB.
COMMENTS:       WXM error box is circular; not rectangular.
COMMENTS:       WXM S/N is less than a reasonable value.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Wed 28 May 03 13:03:52 UT
NOTICE_TYPE:    HETE S/C_Update
TRIGGER_NUM:    2724,   Seq_Num: 3
GRB_DATE:       12787 TJD;   148 DOY;   03/05/28
GRB_TIME:       46982.83 SOD {13:03:02.83} UT
TRIGGER_SOURCE: Trigger on the 25-400 keV band.
GAMMA_RATE:     153  [cnts/s]  on a 1.300 [sec] timescale
SC_-Z_RA:       276 [deg]
SC_-Z_DEC:      -15 [deg]
SC_LONG:        122 [deg East]
WXM_CNTR_RA:    255.841d {+17h 03m 22s} (J2000),
                255.893d {+17h 03m 34s} (current),
                255.088d {+17h 00m 21s} (1950)
WXM_CNTR_DEC:   -22.802d {-22d 48' 06"} (J2000),
                -22.807d {-22d 48' 23"} (current),
                -22.732d {-22d 43' 55"} (1950)
WXM_MAX_SIZE:   60.00 [arcmin] diameter
WXM_LOC_SN:     10 sig/noise (pt src in image)
WXM_IMAGE_SN:   X= 10.0 Y= 2.0 [sig/noise]
WXM_LC_SN:      X= 18.7 Y= 3.2 [sig/noise]
SUN_POSTN:       64.97d {+04h 19m 52s}  +21.45d {+21d 26' 43"}
SUN_DIST:       169.79 [deg]
MOON_POSTN:      36.34d {+02h 25m 22s}  +12.32d {+12d 19' 12"}
MOON_DIST:      141.00 [deg]
MOON_ILLUM:     6 [%]
GAL_COORDS:     359.81,11.30 [deg] galactic lon,lat of the burst
ECL_COORDS:     256.97,-0.00 [deg] ecliptic lon,lat of the burst
COMMENTS:       Probable GRB.
COMMENTS:       WXM error box is circular; not rectangular.
COMMENTS:       WXM S/N is less than a reasonable value.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Wed 28 May 03 13:03:55 UT
NOTICE_TYPE:    HETE S/C_Update
TRIGGER_NUM:    2724,   Seq_Num: 4
GRB_DATE:       12787 TJD;   148 DOY;   03/05/28
GRB_TIME:       46982.83 SOD {13:03:02.83} UT
TRIGGER_SOURCE: Trigger on the 25-400 keV band.
GAMMA_RATE:     153  [cnts/s]  on a 1.300 [sec] timescale 
SC_-Z_RA:       276 [deg]
SC_-Z_DEC:      -15 [deg]
SC_LONG:        122 [deg East] 
WXM_CNTR_RA:    255.859d {+17h 03m 26s} (J2000),
                255.911d {+17h 03m 39s} (current),
                255.106d {+17h 00m 25s} (1950)
WXM_CNTR_DEC:   -22.802d {-22d 48' 07"} (J2000),
                -22.807d {-22d 48' 24"} (current),
                -22.733d {-22d 43' 56"} (1950)
WXM_MAX_SIZE:   60.00 [arcmin] diameter
WXM_LOC_SN:     12 sig/noise (pt src in image)
WXM_IMAGE_SN:   X= 12.5 Y= 2.5 [sig/noise]
WXM_LC_SN:      X= 23.5 Y= 3.2 [sig/noise]
SUN_POSTN:       64.97d {+04h 19m 52s}  +21.45d {+21d 26' 43"}
SUN_DIST:       169.77 [deg]
MOON_POSTN:      36.34d {+02h 25m 22s}  +12.32d {+12d 19' 12"}
MOON_DIST:      140.98 [deg] 
MOON_ILLUM:     6 [%]
GAL_COORDS:     359.82,11.29 [deg] galactic lon,lat of the burst
ECL_COORDS:     256.98,0.00 [deg] ecliptic lon,lat of the burst
COMMENTS:       Probable GRB.
COMMENTS:       WXM error box is circular; not rectangular.
COMMENTS:       WXM S/N is less than a reasonable value.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Wed 28 May 03 13:07:30 UT
NOTICE_TYPE:    HETE S/C_Last  
TRIGGER_NUM:    2724,   Seq_Num: 5
GRB_DATE:       12787 TJD;   148 DOY;   03/05/28
GRB_TIME:       46982.83 SOD {13:03:02.83} UT
TRIGGER_SOURCE: Trigger on the 25-400 keV band.
GAMMA_RATE:     153  [cnts/s]  on a 1.300 [sec] timescale 
SC_-Z_RA:       276 [deg]
SC_-Z_DEC:      -15 [deg]
SC_LONG:        122 [deg East] 
WXM_CNTR_RA:    255.859d {+17h 03m 26s} (J2000),
                255.911d {+17h 03m 39s} (current),
                255.106d {+17h 00m 25s} (1950)
WXM_CNTR_DEC:   -22.802d {-22d 48' 07"} (J2000),
                -22.807d {-22d 48' 24"} (current),
                -22.733d {-22d 43' 56"} (1950)
WXM_MAX_SIZE:   60.00 [arcmin] diameter
WXM_LOC_SN:     12 sig/noise (pt src in image)
WXM_IMAGE_SN:   X= 12.5 Y= 2.5 [sig/noise]
WXM_LC_SN:      X= 23.5 Y= 3.2 [sig/noise]
SUN_POSTN:       64.97d {+04h 19m 52s}  +21.45d {+21d 26' 43"}
SUN_DIST:       169.77 [deg]
MOON_POSTN:      36.34d {+02h 25m 22s}  +12.32d {+12d 19' 12"}
MOON_DIST:      140.98 [deg] 
MOON_ILLUM:     6 [%]
GAL_COORDS:     359.82,11.29 [deg] galactic lon,lat of the burst
ECL_COORDS:     256.98,0.00 [deg] ecliptic lon,lat of the burst
COMMENTS:       Probable GRB.
COMMENTS:       WXM error box is circular; not rectangular.
COMMENTS:       WXM S/N is less than a reasonable value.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Wed 28 May 03 14:50:02 UT
NOTICE_TYPE:    HETE Ground Analysis
TRIGGER_NUM:    2724,   Seq_Num: 6
GRB_DATE:       12787 TJD;   148 DOY;   03/05/28
GRB_TIME:       46982.83 SOD {13:03:02.83} UT
TRIGGER_SOURCE: Trigger on the 25-400 keV band.
GAMMA_RATE:     153  [cnts/s]  on a 1.300 [sec] timescale 
SC_-Z_RA:       275 [deg]
SC_-Z_DEC:      -15 [deg]
SC_LONG:        122 [deg East] 
SXC_CNTR_RA:    256.009d {+17h 04m 02s} (J2000),
                256.060d {+17h 04m 14s} (current),
                255.256d {+17h 01m 01s} (1950)
SXC_CNTR_DEC:   -22.650d {-22d 38' 59"} (J2000),
                -22.655d {-22d 39' 15"} (current),
                -22.581d {-22d 34' 50"} (1950)
SXC_MAX_SIZE:   4.00 [arcmin] diameter
SXC_LOC_SN:     5 sig/noise (pt src in image)
SUN_POSTN:       64.97d {+04h 19m 52s}  +21.45d {+21d 26' 43"}
SUN_DIST:       169.65 [deg]
MOON_POSTN:      36.34d {+02h 25m 22s}  +12.32d {+12d 19' 12"}
MOON_DIST:      140.87 [deg]
MOON_ILLUM:     6 [%]  
GAL_COORDS:     0.03,11.27 [deg] galactic lon,lat of the burst
ECL_COORDS:     257.11,0.17 [deg] ecliptic lon,lat of the burst
COMMENTS:       Definite GRB.
COMMENTS:       SXC error box is circular; not rectangular.
COMMENTS:       Burst_Validity flag is true.
COMMENTS:       SXC data refined since S/C_Last Notice.

red DSS finding chart ps-file
GCN notice #2252
M. Uemura, R. Ishioka, T. Kato, (Kyoto U) and H. Yamaoka (Kyushu U) report:
"We have been performing the unfiltered CCD imaging of the field of GRB 030528 (=H2724) with a 25-cm telescope at Kyoto University, starting at 13:07:15 UT (252 seconds after burst). The first five images (30 seconds exposure each) fully covered the SXC error circle (Seq_Num 6). The visual comparison with the DSS 2 red image revealed no new source up to 16.0 mag (based on USNO-A2.0 red magnitudes) on each image. Further observation and analysis is underway.
This message can be cited."
GCN notice #2253
K. Torii (RIKEN) reports:
The entire SXC error region of GRB 030528 (HETE trigger 2724, Sequence number 6) was observed by the automated system at RIKEN. Observations with 0.20-m telescope (f/4.0, equipped with unfiltered AP7p) and 0.25-m telescope (f/6.8, equipped with unfiltered AP6E) started at 13:04:48 UT and 13:05:31 UT on 2003 May 28, respectively.
Preliminary inspection of the first frame from the 0.25-m telescope (60-s integration) does not show an optical transient candidate brighter than about 15.8 mag (USNO-A2.0 red magnitude). Further analysis and observation are in progress.
GCN notice #2256
J-L Atteia, N. Kawai, D. Lamb, G. Ricker, and S. Woosley on behalf of the HETE Science Team;
C. Barraud, M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf of the HETE FREGATE Team;
N. Butler, G. Crew, J. Doty, G. Prigozhin, R. Vanderspek, J. Villasenor, T. Cline, J. G. Jernigan, A. Levine, F. Martel, E. Morgan, G. Monnelly, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams;
K. Torii, C. Graziani, Y. Shirasaki, T. Donaghy, M. Matsuoka, M. Suzuki, T. Tamagawa, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, T. Tavenner, Y. Nakagawa, R. Satoh, Y. Urata, T. Yamazaki and Y. Yamamoto, on behalf of the HETE WXM Team;
At 13:03:02.83 UTC (46982.83 UT) on 28 May 2003, the HETE FREGATE, SXC, and WXM instruments detected event H2724, a long GRB.
The burst triggered FREGATE in the 30-400 keV energy band. The WXM flight software detected the GRB and calculated a location, which was reported in a GCN Notice at 13:03:40, 37 seconds after the beginning of the burst and while the burst was still in progress. The flight localization was strong in the X detector, but weak in the Y detector: the low S/N in the Y localization resulted in a reported error circle of 30' radius.
Ground analysis of the SXC data produced a refined location which was reported in a GCN Notice at 14:50:02, 107 minutes after the beginning of the burst. The SXC localization SNR was 5. The SXC localization may be expressed as a 90% confidence circle that is 2 arcminutes in radius and is centered at:
R.A. = 17h 04m 02s, Dec. = -22d 38' 59" (J2000).
The fluence of the burst was 4.3 x 10^-6 erg cm^-2 in the 7-30 keV energy band, and 4.8 x 10^-6 erg cm^-2 in the 30-400 keV energy band. The peak flux over 1 s is 1.1 x 10^-7 erg/cm2/s in the 7-30 keV band, and 4.9 x 10^-8 erg/cm2/s in the 30-400 keV band.
The T90 duration of the burst in the 30-400 keV energy band was 21.6 seconds; in the 7-30 keV band, T90 was > 60s.
A light curve and a skymap for GRB030528 are available at the following URL:
http://space.mit.edu/HETE/Bursts/GRB030528
GCN notice #2257
K. Ayani (Bisei Astronomical Observatory) and H. Yamaoka (Kyushu Univ.) report:
"R-filtered CCD images of the field of GRB 030528 (GCN 2256) were taken with a 1.01-m telescope at Bisei Astronomical Observatory. The Stacked image of 5 exposures (60 seconds each) taken on 15:22-15:28 UT (139 - 145 minutes after burst) fully contains the SXC error circle (GCN 2256). Visual examination with DSS red image revealed no new object down to R ~ 18.7 (based on GSC-2.2 F magnitudes) within the error circle.
This message can be cited.
GCN notice #2258
G. Valentini, G. Alleva, E. Brocato (INAF-OACT), E. Palazzi (IASF/CNR, Bologna) report:
"Three unfiltered optical images of error box of the GRB030528 (GCN 2256) were acquired starting on 2003 May 29.04, with the 0.72-m TNT telescope of the Astronomical Observatory of Collurania - Teramo (Italy), for a total exposure time of 2200 seconds. The average seeing was 4.5 arcsec.
No new or noticeable object down to a magnitude of about 20.5 is detected inside the error circle when we compare our summed frame with the DSS-II Digital Sky Survey.
This message is citeable."
GCN notice #2261
GRB030528(=H2724): Revised SXC Localization
J. Villasenor, N. Butler, G. Crew, J. Doty, G. Prigozhin, R. Vanderspek, T. Cline, J. G. Jernigan, A. Levine, F. Martel, E. Morgan, G. Monnelly, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams;
G. Ricker, J-L Atteia, N. Kawai, D. Lamb, and S. Woosley on behalf of the HETE Science Team;
C. Barraud, M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf of the HETE FREGATE Team;
K. Torii, C. Graziani, Y. Shirasaki, T. Donaghy, M. Matsuoka, M. Suzuki, T. Tamagawa, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, Y. Nakagawa, R. Satoh, Y. Urata, T. Yamazaki and Y. Yamamoto, on behalf of the HETE WXM Team;
write:
Further analysis of the spacecraft aspect data near the time of GRB030528 indicates that an additional systematic correction to the HETE SXC localization reported in GCN2256 (Atteia et al) is required. This analysis uses the known position of Sco X-1, which was within the SXC field-of-view at the time of GRB030528. We conclude that a best estimate location for GRB030528 is:
```
RA (J2000) = 17h 03m 58s,	Dec (J2000) = -22d 38m 00s
```
with an error radius of 2.5 arcminutes. This revised location is displaced by 1.3 arcmin from the one reported in GCN2256.
This message may be cited.
GCN notice #2264
GRB030528: Planned Target of Opportunity Observations with Chandra X-ray Observatory
G. Ricker, P. Ford, N. Butler, R. Vanderspek, J. Villasenor (MIT), D. Lamb (U. Chicago), and J.G. Jernigan (UCB), on behalf of a Chandra GRB ToO Team,
write:
Chandra target-of-opportunity observations of the HETE SXC error circle for GRB030528 (=H2724: Atteia et al, GCN 2256; Villasenor et al, GCN 2261) are currently planned. The region to be imaged with ACIS will extend +/- 4 arcmin about the revised location reported by Villasenor et al (GCN2261). The first epoch observation should take place near 3-4 June, with a second epoch observation ~1 week later.
The scheduling of contemporaneous observations at other wavelengths is strongly encouraged.
GCN notice #2267
A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:
We have acquired BVRcIc all-sky photometry for a 11x11 arcmin field centered at the coordinates of the SXC error box for the HETE burst GRB030528 (Villasenor et al., GCN 2261) with the USNOFS 1.0-m telescope on one photometric night. Stars brighter than V=13.5 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/grb030528.dat The astrometry in this file is based on linear plate solutions with respect to UCAC2. The external errors are less than 100mas. However, due to the crowding in this galactic field, only isolated stars will have decent astrometry or photometry.
As always, you should check the dates on the .dat file prior to final publication to get the latest photometry. We anticipate one more night of photometry to be acquired during this week.
GCN notice #2269
GRB030528(=H2724): Observations with the Chandra X-ray Observatory
N. Butler, A. Dullighan, P. Ford, G. Ricker, R. Vanderspek (MIT); K. Hurley , G. Jernigan (U.C.- Berkeley); and D. Lamb (U.Chicago)
on behalf of the Chandra GRB ToO Team and the HETE Science Team
write:
On 3 June, the Chandra Observatory targeted the field of GRB030528, which was localized by the HETE satellite (Atteia et al, GCN2256). The 25 ksec observation spanned the interval 12:22-20:08 UT, 5.97 - 6.29 days after the burst. The revised SXC error region from Villasenor et al. (GCN2261) was completely contained within the field-of-view of the Chandra ACIS-S3 chip (see planning comments in Ricker et al. GCN2264).
Within the revised SXC error region, we detected four sources in the 0.5-8 keV band:
```
 #      Chandra Name           RA           DEC       dR(s) dD(") Cts
  1 CXOU J170400.3-223710  17 4  0.31  -22 37  9.99  0.053  0.91  39
  4 CXOU J170348.4-223826  17 3 48.39  -22 38 25.93  0.054  0.92  30
  9 CXOU J170400.1-223548  17 4  0.11  -22 35 48.10  0.053  0.92  11
 10 CXOU J170354.0-223654  17 3 53.95  -22 36 53.67  0.054  0.93   9
```
The # column refers to the source's relative ranking (in terms of total counts) among all the sources detected in the entire ACIS-S3 field-of-view. For completeness, we tabulate below seven additional sources that are within the ACIS-S3 field-of-view but are outside the revised SXC error region:
```
 #      Chandra Name           RA           DEC       dR(s) dD(") Cts
  2 CXOU J170358.7-224237  17 3 58.67  -22 42 36.67  0.063  0.94  31
  3 CXOU J170355.7-223503  17 3 55.73  -22 35  2.66  0.053  0.92  23
  5 CXOU J170342.8-223548  17 3 42.81  -22 35 48.19  0.053  0.92  24
  8 CXOU J170403.9-223543  17 4  3.87  -22 35 43.30  0.053  0.92  13
 14 CXOU J170341.4-223646  17 3 41.44  -22 36 46.07  0.053  0.95   6
 15 CXOU J170411.2-224032  17 4 11.24  -22 40 32.01  0.055  0.96  11
 17 CXOU J170345.8-224133  17 3 45.81  -22 41 32.71  0.060  1.00  10
```
The astrometry was calibrated using six stars with detectable X-ray emission from the list generated by A. Henden (GCN2267) that lay within the ACIS-S3 field-of-view.
In the above 2 tables, dR, the uncertainty in RA, and dD, the uncertainty in DEC, were established by summing the following in quadrature for each coordinate: the X-ray centroiding error, the correlation error between the X-ray and optical positions, and the error estimates from the reference stars.
We gratefully acknowledge the timely assistance of the personnel at the Chandra Science Center in the acquisition and preliminary processing of these data.
This message may be cited.
GCN notice #2270
D. A. Frail (NRAO) and E. Berger (Caltech) report on behalf of a larger collaboration:
"On 2003 June 3.32 UT we used the VLA to image the 2.5-arcmin error circle of the HETE SXC of GRB 030528 (GCN#2261). A 15-minute integration was taken at a frequency of 8.46 GHz with the VLA in the A-array configuration, producing a synthesized beam of 0.5" x 0.25".
There are no sources in the SXC error circle above a level of 350 uJy (about 5-sigma). We have made a deeper search in the vicinity of the four Chandra X-ray sources (GCN#2269) but we find no significant (>3-sigma) detections."
This message may be cited.
GCN notice #2271
J. Greiner, A. Rau (both MPE Garching) and S. Klose (Thueringer Landessternwarte Tautenburg) report for the GRACE collaboration:
We have observed the original, 2 arcmin radius error box of GRB 030528 (=H2724) (Atteia et al, GCN 2256) with the near-infrared camera SOFI at the NTT (La Silla, ESO) on three epochs as given below:
```
   Date (Start UT)   Filters   Exposure time   Seeing    
  -------------------------------------------------------
  2003-05-29 04:58    JHKs      15 min each     0.6"
  2003-05-30 04:54    JHKs      20 min each     1.0"
  2003-06-01 04:07     Ks       60 min          0.7"
```
The Chandra sources #1 and #10 (Butler et al., GCN 2269) are within our field of view, the other two Chandra sources from within the shifted GRB location (Villasenor et al, GCN 2261) are outside our images. Comparing the Ks band images of the first and third epoch reveals a counterpart for each of the two Chandra sources. One of these two sources, i.e. #1 = CXOU J170400.3-223710 shows a fading by about 0.9 mag. The other of these two Chandra sources, #10 = CXOU J170354.0-223654 is about 4 magnitudes brighter in Ks, and constant to within 0.1 mag (provisional photometric calibration was done against the 2MASS catalog, taken from the NASA/ IPAC Infrared Science Archive).
We therefore propose Chandra source #1 = CXOU J170400.3-223710 and its near-infrared counterpart as the tentative afterglow of GRB 030528. K band images of two epochs for this source will be displayed at http://www.mpe.mpg.de/~jcg/grb030528.html.
Since we are missing two of the Chandra sources due to the shift of the GRB location, only a second Chandra observation can (dis)prove this tentative counterpart. We note, that the proposed counterpart is the brightest X-ray source in the previous Chandra image, so a second Chandra observation of the same exposure time can already be decisive.

K band images at two epochs around the Chandra source #1 (blue circle) with the proposed NIR counterpart marked with two dashes. Green circles denote 2MASS sources. North is to the left, and the field of view is 37 arcsec.
GCN notice #2273
N. Mirabal & J. P. Halpern (Columbia U.) report on behalf of the MDM Observatory GRB follow-up team:
"We obtained I-band images on the MDM 1.3m for 1.5 hours on June 5.28, covering the positions of most of the Chandra X-ray sources listed by Butler et al. (GCN 2269).
We detect optical counterparts of three of the four sources within the revised SXC region reported by Villasenor et al. (GCN 2261). The source CXOU J170400.3-223710, tentatively proposed as the GRB afterglow by Greiner et al. (GCN 2271), is not detected in any of our images to a preliminary limiting magnitude I > 21.5. Comparison with prior observations and deeper optical images of this location would be useful."
This message may be cited.
GCN notice #2275
GRB 030528: Infrared Observations and the Proposed IR Counterpart
M. Bogosavljevic, A. Mahabal, and S. G. Djorgovski (Caltech), report on behalf of the Caltech-NRAO-CARA GRB collaboration:
On June 3, 2003, 08:30 UT we observed the field of the tentative near-IR afterglow of GRB 030528 (Greiner et al, GCN 2271), using the WIRC camera at the Palomar 200-inch Hale telescope. A total of 30 min on-source exposure was obtained in the Ks band. The average seeing was ~1.0".
The proposed afterglow of GRB 030528, Chandra source #1 (CXOU J170400.3-223710, Butler et al., GCN 2269) is not detected down to our 3-sigma detection limit of Ks~19.5, indicating a continued fading (see Greiner et al, GCN 2271), and strengthening its interpretation as the afterglow of GRB 030528.
Our 8x8 arcmin FOV also covers Chandra sources #4, #9, #10, all of which are within the SXC revised error region. All three are detected. IR images and magnitude estimates will be placed at:
http://www.astro.caltech.edu/~milan/GRB030528/
The field also includes Chandra sources #3, #5, #8, #14, #15 and #17, from the additional list outside the SXC error region (Butler et al., GCN 2269 and ref. therein).
This message can be cited.
GCN notice #2279
GRB030528(=H2724): X-ray Afterglow Identified in Second Epoch Observations with the Chandra X-ray Observatory
N. Butler, A. Dullighan, P. Ford, G. Ricker, R. Vanderspek (MIT); K. Hurley , G. Jernigan (U.C.- Berkeley); and D. Lamb (U.Chicago)
on behalf of the Chandra GRB ToO Team and the HETE Science Team
write:
From 9 June 8:14 UT to 9 June 14:19 UT, the Chandra Observatory targeted the field of the X-ray rich GRB030528, which was localized by the HETE satellite (Atteia et al. GCN2256; Villasenor et al. GCN2261). The 20 ksec second epoch (E2) observation with ACIS-S3 was a follow up to the 25 ksec first epoch (E1) observation performed with ACIS-S3 on 3 June (Butler et al. GCN 2269).
Of the 4 sources reported in GCN2269 lying within the revised SXC error region (Villasenor et al. GCN2261) and the 7 sources lying beyond this error region but inside the ACIS-S3 field-of-view, only one source declined in brightness with a significance greater than 2 sigma:
```
#     Chandra Name          RA          DEC       E1 Cnts  E2 Cnts
1 CXOU J170400.3-223710  17 4 0.31  -22 37 9.99     39       8
```
Thus, Chandra Source #1 faded by a factor of about 4 between our two observations (level of significance of approximately 4 sigma; the implied power law decay index is 2.0 +/- 0.8). Hence, we are quite confident that Chandra Source #1 is indeed the X-ray afterglow of GRB030528. Based on the coincidence in position and moderate early fading in Ks reported by Greiner et al. (GCN 2271) and the faint lower limit on Ks reported by Bogosavljevic et al. (GCN 2275), Chandra Source #1 appears to be associated with the NIR candidate first reported in GCN 2271.
In view of the imminent possibility of a "supernova bump" becoming visible from GRB030528, we urge continued deep optical and IR monitoring of Chandra Source #1.
This message may be cited.
astro-ph/0508394 from 18 Aug 2005
Rau et al: The host of GRB/XRF 030528 - an actively star forming galaxy at z=0.782
An important parameter for the distinction of X-ray flashes, X-ray rich bursts and Gamma-ray bursts in the rest frame is the distance to the explosion site. Here we report on the spectroscopic redshift determination of the host galaxy of XRF/GRB 030528 using the ESO VLT FORS2 instrument. From the strong oxygen and hydrogen emission lines the redshift was measured to be z=0.782+-0.001. Obtaining the line luminosities and ratios we find that the host is consistent with being an actively star forming galaxy with sub-solar metallicity. With a stellar mass of ~10E10 Msun the host is placed among the most massive GRB host galaxies at a similar redshift. Estimating the redshifted properties of the prompt emission, we find that XRF/GRB 030528 would be classified as an X-ray rich bursts in the rest frame rather than an X-ray flash in the typically used observer frame.
1002.3849 from 23 Feb 10
M. Arimoto et al.: Spectral Lag Relations in GRB Pulses Detected with HETE-2
T. Tamagawa, Y. Shirasaki, S. Sugita, I. Takahashi, J.-L. Atteia, A. Pelangeon, R. Vanderspek, C. Graziani, G. Prigozhin, J. Villasenor, J. G. Jernigan, G. B. Crew, T. Sakamoto, G. R. Ricker, S. E. Woosley, N. Butler, A. Levine, J. P. Doty, T. Q. Donaghy, D. Q. Lamb, E. Fenimore, M. Galassi, M. Boer, J.-P. Dezalay, J.-F. Olive, J. Braga, R. Manchanda, G. Pizzichini Using a pulse-fit method, we investigate the spectral lags between the traditional gamma-ray band (50-400 keV) and the X-ray band (6-25 keV) for 8 GRBs with known redshifts (GRB 010921, GRB 020124, GRB 020127, GRB 021211, GRB 030528, GRB 040924, GRB 041006, GRB 050408) detected with the WXM and FREGATE instruments aboard the HETE-2 satellite. We find several relations for the individual GRB pulses between the spectral lag and other observables, such as the luminosity, pulse duration, and peak energy (Epeak). The obtained results are consistent with those for BATSE, indicating that the BATSE correlations are still valid at lower energies (6-25 keV). Furthermore, we find that the photon energy dependence for the spectral lags can reconcile the simple curvature effect model. We discuss the implication of these results from various points of view.

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Jochen Greiner, last update: 23-Feb-2010 [Disclaimer]