Gamma-ray Burst 060421

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Apr 06 00:39:37 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     206257,   Seg_Num: 0
GRB_RA:          343.630d {+22h 54m 31s} (J2000),
                 343.692d {+22h 54m 46s} (current),
                 343.143d {+22h 52m 34s} (1950)
GRB_DEC:         +62.727d {+62d 43' 37"} (J2000),
                 +62.761d {+62d 45' 38"} (current),
                 +62.460d {+62d 27' 36"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1896 [cnts]    Image_Peak=133 [image_cnts]
TRIGGER_DUR:     0.256 [sec] 
TRIGGER_INDEX:   123     E_range: 25-100 keV
BKG_INTEN:       32819 [cnts]
BKG_TIME:        2350.85 SOD {00:39:10.85} UT
BKG_DUR:         8 [sec]
GRB_DATE:        13846 TJD;   111 DOY;   06/04/21
GRB_TIME:        2363.33 SOD {00:39:23.33} UT
GRB_PHI:         -178.89 [deg]
GRB_THETA:        28.94 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     25.59 [sigma]
IMAGE_SIGNIF:    8.34 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2 +16  +0  +1 -49  +1 
SUN_POSTN:        28.66d {+01h 54m 39s}  +11.75d {+11d 44' 48"}
SUN_DIST:         60.13 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:      302.40d {+20h 09m 35s}  -24.94d {-24d 56' 32"}
MOON_DIST:        93.62 [deg]
MOON_ILLUM:      52 [%]
GAL_COORDS:      109.99,  2.83 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       28.13, 60.10 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 140.95,7.11 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Apr 06 00:40:58 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     206257,   Seg_Num: 0
POINT_RA:        343.618d {+22h 54m 28s} (J2000)
POINT_DEC:       +62.717d {+62d 43' 00"} (J2000)
IMG_START_DATE:  13846 TJD;   111 DOY;   06/04/21
IMG_START_TIME:  2450.89 SOD {00:40:50.89} UT,   87.6 [sec] since BAT Trigger Time
COUNTS:          31    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        4    Max_iter_allowed= 4
ERROR_CODE:      2
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        Algorithm did not converge; too many interations.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Apr 06 00:43:05 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     206257,   Seg_Num: 0
GRB_RA:          343.630d {+22h 54m 31s} (J2000),
                 343.692d {+22h 54m 46s} (current),
                 343.143d {+22h 52m 34s} (1950)
GRB_DEC:         +62.727d {+62d 43' 37"} (J2000),
                 +62.761d {+62d 45' 38"} (current),
                 +62.460d {+62d 27' 36"} (1950)
GRB_DATE:        13846 TJD;   111 DOY;   06/04/21
GRB_TIME:        2363.33 SOD {00:39:23.33} UT
TRIGGER_INDEX:   123
GRB_PHI:         -178.89 [deg]
GRB_THETA:        28.94 [deg]
DELTA_TIME:      32.00 [sec]
TRIGGER_DUR:     0.256 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     25.59 [sigma]
IMAGE_SIGNIF:    8.34 [sigma]
LC_URL:          sw00206257000msb.lc
SUN_POSTN:        28.66d {+01h 54m 39s}  +11.75d {+11d 44' 51"}
SUN_DIST:         60.13 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:      302.43d {+20h 09m 44s}  -24.93d {-24d 56' 01"}
MOON_DIST:        93.60 [deg]
MOON_ILLUM:      52 [%]
GAL_COORDS:      109.99,  2.83 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       28.13, 60.10 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        The next comments were copied from the BAT_POS Notice:  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 140.95,7.11 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Apr 06 00:54:36 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     206257,   Seg_Num: 0
POINT_RA:        343.618d {+22h 54m 28s} (J2000)
POINT_DEC:       +62.717d {+62d 43' 01"} (J2000)
POINT_ROLL:      126.963d
IMG_START_DATE:  13846 TJD;   111 DOY;   06/04/21
IMG_START_TIME:  2447.32 SOD {00:40:47.32} UT,   84.0 [sec] since BAT Trigger Time
FILTER:          3, V
BKG_MEAN:        4.399
N_STARS:         190
X_OFFSET:        418 [pixels]
Y_OFFSET:        479 [pixels]
X_MAX:           1377 [pixels]
Y_MAX:           1438 [pixels]
DET_THRESH:      17
PHOTO_THRESH:    10
SL_URL:          sw00206257000msufc0083.fits
SUN_POSTN:        28.67d {+01h 54m 41s}  +11.75d {+11d 45' 00"}
SUN_DIST:         60.13 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:      302.55d {+20h 10m 12s}  -24.91d {-24d 54' 19"}
MOON_DIST:        93.53 [deg]
MOON_ILLUM:      51 [%]
GAL_COORDS:      109.98,  2.82 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       28.11, 60.09 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Apr 06 00:55:39 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     206257,   Seg_Num: 0
POINT_RA:        343.618d {+22h 54m 28s} (J2000)
POINT_DEC:       +62.717d {+62d 43' 01"} (J2000)
POINT_ROLL:      126.963d
IMG_START_DATE:  13846 TJD;   111 DOY;   06/04/21
IMG_START_TIME:  2447.32 SOD {00:40:47.32} UT,   84.0 [sec] since BAT Trigger Time
FILTER:          3, V
BKG_MEAN:        4.399
N_STARS:         190
X_OFFSET:        418 [pixels]
Y_OFFSET:        479 [pixels]
X_MAX:           1377 [pixels]
Y_MAX:           1438 [pixels]
DET_THRESH:      17
PHOTO_THRESH:    10
SL_URL:          sw00206257000msufc0083.fits
SUN_POSTN:        28.67d {+01h 54m 41s}  +11.75d {+11d 45' 01"}
SUN_DIST:         60.13 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:      302.56d {+20h 10m 15s}  -24.90d {-24d 54' 10"}
MOON_DIST:        93.53 [deg]
MOON_ILLUM:      51 [%]
GAL_COORDS:      109.98,  2.82 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       28.11, 60.09 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Apr 06 00:56:32 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     206257,   Seg_Num: 0
POINT_RA:        343.618d {+22h 54m 28s} (J2000)
POINT_DEC:       +62.717d {+62d 43' 01"} (J2000)
ROLL:            126.963d
IMG_START_DATE:  13846 TJD;   111 DOY;   06/04/21
IMG_START_TIME:  2447.32 SOD {00:40:47.32} UT,   84.0 [sec] since BAT Trigger Time
FILTER:          3, V
EXPOSURE_ID:     167272848
X_OFFSET:        738 [pixels]
Y_OFFSET:        799 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       898
Y_GRB_POS:       959
BINNING_INDEX:   1
IM_URL:          sw00206257000msuni0083.fits
SUN_POSTN:        28.67d {+01h 54m 41s}  +11.75d {+11d 45' 02"}
SUN_DIST:         60.13 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:      302.57d {+20h 10m 17s}  -24.90d {-24d 54' 02"}
MOON_DIST:        93.52 [deg]
MOON_ILLUM:      51 [%]
GAL_COORDS:      109.98,  2.82 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       28.11, 60.09 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 21 Apr 06 00:57:39 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     206257,   Seg_Num: 0
POINT_RA:        343.618d {+22h 54m 28s} (J2000)
POINT_DEC:       +62.717d {+62d 43' 01"} (J2000)
ROLL:            126.963d
IMG_START_DATE:  13846 TJD;   111 DOY;   06/04/21
IMG_START_TIME:  2447.32 SOD {00:40:47.32} UT,   84.0 [sec] since BAT Trigger Time
FILTER:          3, V
EXPOSURE_ID:     167272848
X_OFFSET:        738 [pixels]
Y_OFFSET:        799 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       898
Y_GRB_POS:       959
BINNING_INDEX:   1
IM_URL:          sw00206257000msuni0083.fits
SUN_POSTN:        28.67d {+01h 54m 42s}  +11.75d {+11d 45' 03"}
SUN_DIST:         60.13 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:      302.58d {+20h 10m 20s}  -24.90d {-24d 53' 52"}
MOON_DIST:        93.51 [deg]
MOON_ILLUM:      51 [%]
GAL_COORDS:      109.98,  2.82 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       28.11, 60.09 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN Circular #4985
M. R. Goad (U Leicester), L. M. Barbier (NASA/GSFC), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), P. J. Brown (PSU), D. N. Burrows (PSU), J. R. Cummings (NASA/ORAU), N. Gehrels (NASA/GSFC), S. T. Holland (GSFC/USRA), J. A. Kennea (PSU) and D. M. Palmer (LANL) report on behalf of the Swift Team:
At 00:39:23 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060421 (trigger=206257). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 343.630,+62.727 {22h 54m 31s, +62d 43' 37"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a multi-peak structure starting at about T-5sec and lasting to at least T+20 sec (a duration of about 25 sec). The peak count rate was ~6000 counts/sec (15-350 keV), at ~3 sec after the trigger.
This source is coincident with the Cepheus OB3 molecular cloud association in our Galaxy. Therefore it is possible that this burst (galactic long,lat = 109.99, +2.83) was from a galactic source.
The XRT began taking data at 00:40:50 UT, 88 seconds after the BAT trigger. The XRT on-board centroid algorithm did not find a source in the image and no prompt position is available. Analysis of down-linked image data reveals no obvious X-ray point source in the field. We are waiting for the full down-linked dataset to detect and determine a position for the source, and to determine the nature of this source.
UVOT took a finding chart exposure of 400 seconds with the V filter starting 85 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of the BAT error circle. The typical 3-sigma upper limit has been about 18.5 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. The limiting magnitude is expected to be about 17.7. No correction has been made for the large, but uncertain extinction expected.
Results from analysis of downlinked data will not be available until approximately 09:00UT.
GCN Circular #4986
Jan Strobl, Martin Topinka, Martin Nekola and Ren=E9 Hudec (ASU Ondrejov, Czech Republic), Petr Kub=E1nek (ISDC Versoix, Swtzerland and ASU Ondrejov) and Martin Jel=EDnek (IAA Granada)
report
Robotic telescope BART located in Ondrejov observatory in Czech Republic, followed the Swift trigger 206257 (Goad et al, GCN 4985). The observation in fully automatic mode (under control of RTS2), started 33.7s after the Swift trigger time. We did not find any new optical source. Particularly we set the following limits:
```
Tmean   Exp   limit 
44s     20s  B>14.2
98.0s   20s  V>15.2
152s    20s  i>15.3
206s    20s  z>14.3
184s  8x45s  R>15.3
```
The magnitudes are calibrated against USNO-A2.0.
GCN Circular #4987
Mike Goad, Kim Page (U Leicester) report on behalf of the Swift XRT team :
From a ground analysis of 436 seconds of PC mode data starting 98 seconds after the BAT trigger (trigger no. 206257) we detect a fading source at position RA 22 54 32.4, Dec +62 43 49.0 (J2000), with an estimated uncertainty of 4.1 arcseconds (90% containment).
This circular is an official product of the Swift XRT team.
GCN Circular #4988
V. Lipunov, V.Kornilov, N.Tyurina, A.Belinski, D.Kuvshinov, E.Gorbovskoy, A.Krylov, G.Borisov, A.Sankovich, V.Vladimirov, P.Gritsyk, S.Korobkin
Sternberg Astronomical Institute, Moscow Union 'Optic' MASTER robotic system (http://observ.pereplet.ru) responded to GRB060421 (GRB_TIME is 2006-04-21 00:39:23.33, M. R. Goad et al. GCN4985).
Unfortunaly 2 minutes before notice time roof closed roboticaly due to meteo alert "cloudy". The first image was at 2006-04-21 00:48:45 UT, 562 s after the GRB time. The unfiltered image is calibrated relative to USNO A2.0 (0.8 R + 0.2 B). The robot not find OT-candidate in error box brighter then 16.8 (s/n=3) at Swift XRT position (Mike Goad, Kim Page GCN4987). This work is supported by RFFI 04-02-16411 grant. This message can be cited. Mailto: lipunov@sai.msu.ru
GCN Circular #4992
M.R. Goad, K.L. Page (U Leicester) and D.N. Burrows (PSU) report on behalf of the Swift-XRT team:
We have analysed the first 14 ks of Photon Counting (PC) mode data, starting 97 seconds after the BAT trigger time, determining a refined position of
```
RA (J2000):   22 54 32.63
Dec(J2000):  +62 43 50.07
```
with an estimated uncertainty of 3.8 arcsec (90% containment). This is 1.7 arcsec from the initial XRT position given by Goad & Page in GCN 4987 and 16.2 arcsec from the on-board BAT position quoted in GCN 4985 (Goad et al.)
The X-ray source was initially quite faint, with a peak count rate of only ~1 count s^-1. The light-curve shows a flat decay of alpha = 0.49 +/- 0.29, breaking to a steeper slope of alpha = 1.54 +/- 0.36, approximately 1500 seconds after the burst.
Because of the faintness of the afterglow, only 3 seconds of data were obtained in Windowed Timing mode before switching into PC. The first orbit of PC data (97-717 seconds post-trigger) can be modelled with a simple power-law of Gamma = 1.54 +/- 0.34, with the Galactic absorbing column of 1e22 cm^-2. The observed (unabsorbed) flux over 0.3-10 keV for this time period is 3.78e-11 (5.64e-11) erg cm^-2 s^-1.
Assuming the current rate of decay continues, the estimated count rate at 24 hours is 4.2e-3 count s^-1, corresponding to an observed (unabsorbed) flux of 4.55e-14 (6.38e-14) erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
GCN Circular #4993
E. Fenimore (LANL), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/ORAU), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (ISAS), J. Tueller (GSFC), on behalf of the Swift-BAT team:
Using the data set from T-120 to T+78 sec from the recent telemetry downlink, we report further analysis of BAT GRB 060421 (trigger #206257) (Goad, et al., GCN 4985). The BAT ground-calculated position is (RA,Dec) = 343.627, 62.730 deg {22h 54m 30.4s, 62d 43' 47.0"} (J2000) +- 0.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 82%.
The mask-weighted light curve shows one strong peak followed by several smaller peaks extending out to 10 seconds after the trigger. T90 (15-350 keV) is 11 +- 1 sec (estimated error including systematics).
The time-averaged spectrum from T-3.8 to T+10.9 is well fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.53 +- 0.07. The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+2.28 sec in the 15-150 keV band is 3.0 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
Based on the shape of the light curve and the hard spectrum, we believe that this is a GRB, however, we can not rule out a hard x-tray transient nature of this event.
GCN Circular #4994
P. J. Brown (PSU), M. R. Goad (U Leicester), S. T. Holland (GSFC/USRA), & P. O'Brien (U Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began taking settled exposures of the field of GRB0604213 at 2006-04-21 00:40:48, 84 s after the BAT trigger (Goad et al., GCN 4985). Within the revised XRT error circle (Goad, Page, & Burrows GCN 4992) we detect a V=19.0 +/- 0.2 source at 22:54:32.18, +62:43:49.5 (+/- 1") which is coincident with 2MASS 22543217+6243493 and also visible in the DSS. This source does not vary over ~5 hours of observations and is not considered an afterglow candidate.
We do not detect this or any other sources in summed images from any of the other filters down to the following three-sigma upper limits.
```
Filter  T_range(s)  Exp(s) 3sig_UL

V        84-17355   1700   19.0
B       562-23873   1116   20.6
U       538-23145   2035   20.5
UVW1    514-22233   2204   20.2
UVM2    490-18091   2074   20.4
UVW2    578-16442   1318   20.2
```
These upper limits are uncorrected for extinction. The Galactic latitude is +2.83 degrees and the Schlegel et al. (1998) reddening in this direction is E(B-V)=1.28 mag. As noted in GCN 4985 the Cepheus OB3 molecular cloud association in our Galaxy is near this line of sight.

GCN Circular #4999
C. MacLeod, J. Harvey, A. Trotter, M. Nysewander, A. LaCluyze, D. Reichart, A. Crain, K. Ivarsen, A. Foster, J. Haislip, J. Kirschbrown, and J. Carpenter report on behalf of the UNC team of the FUN GRB Collaboration:
Skynet observed the localization of GRB 060421 (Goad et al., GCN 4985; Goad & Page, GCN 4987; Goad, Page & Burrows, GCN 4992) with 14.5-inch TTT in Colorado beginning 2.2 hours after the burst in variable conditions:

Filter   Start (UT)  Stop (UT)  Exposures  Total (min)
Red*     02:49:45    03:12:03    6 x 160s   16.0
Green**  03:13:48    03:34:41    6 x 160s   16.0
Blue     03:35:51    03:54:51    5 x 160s   13.3
Red*     03:57:17    04:15:58    5 x 160s   13.3
Green**  04:19:00    05:00:41   11 x 160s   29.3
Blue     05:02:14    05:42:19   11 x 160s   29.3
Red*     05:44:56    06:28:07   11 x 160s   30.7
		               + 1 x 80s
Green**  06:29:39    07:12:54   11 x 160s   29.3
Blue     07:14:37    07:55:35   11 x 160s   29.3
Red*     07:57:16    09:20:36   19 x 160s   50.7
Green**  09:22:42    10:45:43   21 x 160s   56.0
Blue     10:48:00    11:06:50    5 x 160s   13.3

* Approximates R band ** Approximates V band
No new source is found to V > 18.3 mag (3 sigma; calibrated to five NOMAD stars) at 4.0 hours after the burst.

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Jochen Greiner, last update: 24-Apr-2006 [Disclaimer]