Gamma-ray Burst 060501

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 May 06 08:20:33 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     208050,   Seg_Num: 0
GRB_RA:          328.367d {+21h 53m 28s} (J2000),
                 328.430d {+21h 53m 43s} (current),
                 327.868d {+21h 51m 28s} (1950)
GRB_DEC:         +43.983d {+43d 58' 59"} (J2000),
                 +44.013d {+44d 00' 47"} (current),
                 +43.747d {+43d 44' 48"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       5540 [cnts]    Image_Peak=263 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   150     E_range: 25-100 keV
BKG_INTEN:       31761 [cnts]
BKG_TIME:        29686.83 SOD {08:14:46.83} UT
BKG_DUR:         8 [sec]
GRB_DATE:        13856 TJD;   121 DOY;   06/05/01
GRB_TIME:        29698.86 SOD {08:14:58.86} UT
GRB_PHI:         -170.26 [deg]
GRB_THETA:        47.71 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     23.30 [sigma]
IMAGE_SIGNIF:    11.15 [sigma]
MERIT_PARAMS:     +1  +0  +0  +1  +2  +8  +0  +1 -42  +1 
SUN_POSTN:        38.41d {+02h 33m 38s}  +15.07d {+15d 04' 26"}
SUN_DIST:         65.26 [deg]   Sun_angle= 4.7 [hr] (West of Sun)
MOON_POSTN:       85.86d {+05h 43m 26s}  +28.53d {+28d 31' 50"}
MOON_DIST:        87.66 [deg]
MOON_ILLUM:      15 [%]
GAL_COORDS:       92.32, -8.06 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      353.48, 51.93 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This Notice was delayed by more than 30 sec past the end of the trigger integration interval;  
COMMENTS:        probably due to it occurring during a Malindi downlink session.  
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 = 17.63,-16.13 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 May 06 08:21:01 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     208050,   Seg_Num: 0
GRB_RA:          328.367d {+21h 53m 28s} (J2000),
                 328.430d {+21h 53m 43s} (current),
                 327.868d {+21h 51m 28s} (1950)
GRB_DEC:         +43.983d {+43d 58' 59"} (J2000),
                 +44.013d {+44d 00' 47"} (current),
                 +43.747d {+43d 44' 48"} (1950)
GRB_DATE:        13856 TJD;   121 DOY;   06/05/01
GRB_TIME:        29698.86 SOD {08:14:58.86} UT
TRIGGER_INDEX:   150
GRB_PHI:         -170.26 [deg]
GRB_THETA:        47.71 [deg]
DELTA_TIME:      76.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     23.30 [sigma]
IMAGE_SIGNIF:    11.15 [sigma]
LC_URL:          sw00208050000msb.lc
SUN_POSTN:        38.41d {+02h 33m 38s}  +15.07d {+15d 04' 26"}
SUN_DIST:         65.26 [deg]   Sun_angle= 4.7 [hr] (West of Sun)
MOON_POSTN:       85.86d {+05h 43m 27s}  +28.53d {+28d 31' 50"}
MOON_DIST:        87.66 [deg]
MOON_ILLUM:      15 [%]
GAL_COORDS:       92.32, -8.06 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      353.48, 51.93 [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 = 17.63,-16.13 [deg].

GCN Circular #5040
V. La Parola (INAF-IASFPA), S. D. Barthelmy (GSFC), N. Gehrels (NASA/GSFC), V. Mangano (INAF-IASFPA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), P. Romano (INAF-OAB) and E. Troja (INAF-IASFPA) report on behalf of the Swift Team:
At 08:14:58 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060501 (trigger=208050). Swift did not slew due to the earth-observing constraint. The BAT on-board calculated location is RA,Dec 328.367, +43.983 {21h 53m 28s, +43d 58' 59"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows single roughly triangular shaped peak starting at T-5 sec and ending at ~T+20 sec. The peak count rate was ~2400 counts/sec (15-350 keV), at ~0 sec after the trigger.
Because of an Earth limb constraint, the spacecraft did not slew promptly to the BAT position, and so there are no immediate XRT or UVOT data products to analyze.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 May 06 09:10:43 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     208050,   Seg_Num: 0
POINT_RA:        328.352d {+21h 53m 24s} (J2000)
POINT_DEC:       +43.984d {+43d 59' 01"} (J2000)
IMG_START_DATE:  13856 TJD;   121 DOY;   06/05/01
IMG_START_TIME:  33008.07 SOD {09:10:08.07} UT,   3309.2 [sec] since BAT Trigger Time
COUNTS:          1    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        0    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 May 06 09:12:36 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     208050,   Seg_Num: 0
POINT_RA:        328.351d {+21h 53m 24s} (J2000)
POINT_DEC:       +43.984d {+43d 59' 01"} (J2000)
POINT_ROLL:      92.599d
IMG_START_DATE:  13856 TJD;   121 DOY;   06/05/01
IMG_START_TIME:  33011.76 SOD {09:10:11.76} UT,   3312.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.200
N_STARS:         190
X_OFFSET:        562 [pixels]
Y_OFFSET:        530 [pixels]
X_MAX:           1521 [pixels]
Y_MAX:           1489 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00208050000msufc3312.fits
SUN_POSTN:        38.44d {+02h 33m 46s}  +15.08d {+15d 05' 05"}
SUN_DIST:         65.29 [deg]   Sun_angle= 4.7 [hr] (West of Sun)
MOON_POSTN:       86.40d {+05h 45m 35s}  +28.55d {+28d 32' 56"}
MOON_DIST:        87.96 [deg]
MOON_ILLUM:      15 [%]
GAL_COORDS:       92.31, -8.05 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      353.47, 51.94 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 May 06 09:14:58 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     208050,   Seg_Num: 0
POINT_RA:        328.351d {+21h 53m 24s} (J2000)
POINT_DEC:       +43.984d {+43d 59' 01"} (J2000)
POINT_ROLL:      92.599d
IMG_START_DATE:  13856 TJD;   121 DOY;   06/05/01
IMG_START_TIME:  33011.76 SOD {09:10:11.76} UT,   3312.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.200
N_STARS:         190
X_OFFSET:        562 [pixels]
Y_OFFSET:        530 [pixels]
X_MAX:           1521 [pixels]
Y_MAX:           1489 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00208050000msufc3312.fits
SUN_POSTN:        38.44d {+02h 33m 46s}  +15.09d {+15d 05' 07"}
SUN_DIST:         65.29 [deg]   Sun_angle= 4.7 [hr] (West of Sun)
MOON_POSTN:       86.42d {+05h 45m 41s}  +28.55d {+28d 32' 59"}
MOON_DIST:        87.97 [deg]
MOON_ILLUM:      15 [%]
GAL_COORDS:       92.31, -8.05 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      353.47, 51.94 [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:     Mon 01 May 06 09:15:12 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     208050,   Seg_Num: 0
POINT_RA:        328.351d {+21h 53m 24s} (J2000)
POINT_DEC:       +43.984d {+43d 59' 01"} (J2000)
ROLL:            92.599d
IMG_START_DATE:  13856 TJD;   121 DOY;   06/05/01
IMG_START_TIME:  33011.76 SOD {09:10:11.76} UT,   3312.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     168167412
X_OFFSET:        882 [pixels]
Y_OFFSET:        850 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1042
Y_GRB_POS:       1010
BINNING_INDEX:   1
IM_URL:          sw00208050000msuni3312.fits
SUN_POSTN:        38.44d {+02h 33m 46s}  +15.09d {+15d 05' 07"}
SUN_DIST:         65.29 [deg]   Sun_angle= 4.7 [hr] (West of Sun)
MOON_POSTN:       86.42d {+05h 45m 42s}  +28.55d {+28d 32' 59"}
MOON_DIST:        87.97 [deg]
MOON_ILLUM:      15 [%]
GAL_COORDS:       92.31, -8.05 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      353.47, 51.94 [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:     Mon 01 May 06 09:16:57 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     208050,   Seg_Num: 0
POINT_RA:        328.351d {+21h 53m 24s} (J2000)
POINT_DEC:       +43.984d {+43d 59' 01"} (J2000)
ROLL:            92.599d
IMG_START_DATE:  13856 TJD;   121 DOY;   06/05/01
IMG_START_TIME:  33011.76 SOD {09:10:11.76} UT,   3312.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     168167412
X_OFFSET:        882 [pixels]
Y_OFFSET:        850 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1042
Y_GRB_POS:       1010
BINNING_INDEX:   1
IM_URL:          sw00208050000msuni3312.fits
SUN_POSTN:        38.44d {+02h 33m 47s}  +15.09d {+15d 05' 08"}
SUN_DIST:         65.29 [deg]   Sun_angle= 4.7 [hr] (West of Sun)
MOON_POSTN:       86.44d {+05h 45m 46s}  +28.55d {+28d 33' 01"}
MOON_DIST:        87.98 [deg]
MOON_ILLUM:      15 [%]
GAL_COORDS:       92.31, -8.05 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      353.47, 51.94 [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 #5041
E.S. Rykoff (U Mich), B. E. Schaefer (Louisiana State), S.A. Yost (U Mich), R. Quimby (U Texas), report on behalf of the ROTSE collaboration:
ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 060501 (Swift trigger 208050, GCN 5040), producing usable images beginning 92 s after the GCN notice time. An automated response took the first image at 08:22:4.6 UT, 426 s after the burst, under fair conditions with high airmass. We took 7 20-s exposures before bad weather forced the system to close. These unfiltered images are calibrated relative to USNO A2.0 (R).
Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma error circle. Individual images have limiting magnitudes ranging from 16.3-16.4; we set the following specific limits.
```
  start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
  --------------------------------------------------------------------
  08:22:04.6   08:22:24.6        20     16.4          426         N
  08:22:04.6   08:25:29.4       140     17.4          426         Y
```
GCN Circular #5042
V. La Parola (INAF-IASFPa), E. Troja (INAF-IASFPa), G. Tagliaferri (INAF-OAB), D. N. Burrows (PSU) and J. Kennea (PSU) report on behalf of the Swift XRT Team:
The XRT attempted to centroid on GRB 060501 at 09:10:08 UT, 3309 s after the burst. However, at this late time the burst was too faint for an on-board detection in the 2.5 s centroiding image, and the XRT switched immediately to PC mode.
Using the first 4.5 ksec data set from the Malindi download, we find a single weak previously uncatalogued source within the BAT error box at:
```
RA:    21 53 29.9  (J2000)
Dec:  +43 59 53.4 (J2000)
```
with 5.5 arcsec uncertainty (90% confinement). The estimated flux is 2.6e-13 erg/sec/cm2, assuming Galactic absorption and a power law spectrum with photon index 2.0. This source is 58 arcsec from the BAT on-board position.
The available data do not allow us to establish if this source is fading.
GCN Circular #5043
D. Palmer (LANL), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/ORAU), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), M. Koss (UMD), V La Parola (INAF-IASFPA), C. Markwardt (GSFC/UMD), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of the Swift-BAT team:
Using the data set from T-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 060501 (trigger #208050) (La Parola, et al., GCN 5040). The BAT ground-calculated position is RA,Dec = 328.383,+43.993 deg {21h 53m 32.0s,+43d 59' 34.4"} (J2000) +- 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 36%.
The mask-weighted lightcurve shows a single peak starting at T-4 sec and ending at T+14 sec. T90 (15-350 keV) is 26 +- 2 sec (estimated error including systematics). Because the burst location was in an Earth observing constraint, the spacecraft then executed a slew to a preplanned target and the new burst location went out of the BAT FOV at T+148 sec.
The time-averaged spectrum from T-1.3 to T+26.1 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.44 +- 0.15. 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+0.36 sec in the 15-150 keV band is 1.9 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
GCN Circular #5044
D. B. Fox (Penn State) and S. B. Cenko (Caltech) report on behalf of a larger collaboration:
"The robotic Palomar 60-inch telescope (P60) has imaged the localization region of GRB060501 (Swift trigger 208050; La Parola et al., GCN 5040) in a series of exposures beginning 08:48 UT (33 minutes after the burst). We have compared our i-band images to the second-epoch digitized sky survey (XDSS) in a search for new sources consistent with the XRT localization (La Parola et al., GCN 5042). We estimate the XDSS limit in this region, by reference to USNO-B1.0 catalog photometry, as I~19.5 mag. We note that due to the location of this field close to the Galactic plane, the background stellar density is large and the estimated Galactic extinction (E_(B-V)~0.3 mag) is substantial. In particular, there are three star-like objects in XDSS consistent with the XRT localization.
We find no new i-band sources within or near the XRT localization, to a limit of I~19 mag in a coaddition of 4x60s images with mean epoch 08:58 UT (43 minutes after the burs).
A deeper coaddition of 5x150s images with mean epoch 09:47 UT (92 minutes after the burst) reveals no new source within the XRT localization to I~21 mag. However, we do identify a single new point-like source with I~19.3 mag, 8.1" from the center of the XRT localization, at coordinates:
R.A. 21:53:29.52, Dec. +43:59:49.9 (J2000)
(estimated uncertainty of 0.3" in each coordinate). There is no evidence of this source in XDSS survey images.
The source is not resolved from a neighboring star in our earlier images, which have poorer seeing; however, these images do constrain the object to not be significantly brighter at 43 minutes post-burst than at our first detection, 92 minutes post-burst.
Given the absence of evidence for variability, and the distance of the source from the XRT position, we consider the association of this source with GRB060501 tentative at this point."
GCN Circular #5045
P.A.Milne (Steward Obs) reports on behalf of the Super-LOTIS GRB team:
We observed the location of the BAT error circle of the GRB 060501, as reported in GCN 5040 (Swift trigger 208050; La Parola et al.,) using the 60cm Super-LOTIS telescope at Kitt Peak, Arizona. Imaging began at 09:30:30 UT, 1.25 hours after the burst, and consisted of three series of one-minute exposures in the R filter (12, 23 & 17 images per series, respectively). Seeing was typically 2.7".
A source is detected at the positionreported by Fox and Cenko (GCN 5044) in all three summed images created from the individual exposures. Using 8 stars from the USNO-B1 catalog, a single image produced from the first two series led to the following magnitudes for the suggested counterpart, R1=18.39 +/- 0.11, R2=18.54 +/- 0.12. However, these magnitudes are very close to the magnitude of the star 1339-0447675, which is listed at a position consistent with the optical counterpart position listed by Fox and Cenko.
We therefore suggest that the optical counterpart candidate reported in GCN 5044 is instead star 1339-0447675 from the USNO-B1.0 catalog.
Analysis of the last series of exposures is on-going.
GCN Circular #5046
J. P. Halpern (Columbia U.) and N. Mirabal (U. Michigan) report:
"We observed the error box of Swift GRB 060501 (La Parola et al., GCN 5040) in the R band on the MDM 1.3m telescope starting on May 01 08:28 UT, 13.4 minutes after the trigger, and continuing until 11:39 UT. Because of poor seeing at high airmass, we were only able to detect the candidate afterglow (Fox & Cenko, GCN 5044) near the possible X-ray afterglow (La Parola et al., GCN 5042) beginning at 09:01 UT, or 46 minutes post-burst. While the candidate is clearly distinguished from nearby brighter stars, one of which was apparently measured by Milne (GCN 5045), it was not clearly variable during the monitoring period. Although it is difficult to measure due to contamination from nearby stars, we estimate R~20.7. Also, because of the nearby stars, it is not possible to rule out that it is present at this level on the POSS II, and the DSS R and I images show a hint of it.
A finding chart for the candidate from the MDM images is available at
http://www.astro.columbia.edu/~jules/grb/060501/mdm.jpg
This message may be cited."
GCN Circular #5050
A. Breeveld (UCL-MSSL), V. La Parola (INAF-IASFPA), D. Vanden Berk (PSU), F. Marshall (GSFC), on behalf of the SWIFT UVOT team:
The Swift/UVOT began taking data on the field of GRB060501 3296s after the BAT trigger (which includes the 10s V settling exposure). Swift did not slew immediately after the trigger because of an earth constraint (La Parola et al., GCN 5040). At the edge of the refined XRT error circle (La Parola et al., GCN 5042) there are two optical sources which are already present in the USNO B1.0 catalogue, but in the summed images there are no new sources within the error circle to the following 5 sigma upper limits:
```
Filter  T_range(s)  Exp(s)  5sig_UL(mag)
V       3296-16535  927.6   19.3
B       3626-3825   196.6   19.5
U       3422-10542  723.7   19.9
UVW1    9097-9996   885.5   20.0
UVM2    4445-4571   124.1   19.3
UVW2    4036-15788  1082.2  20.5
White (160-650nm)  3313-4030   394.6    20.0
```
These upper limits are uncorrected for the estimated Galactic reddening of E(B-V) = 0.282 mags.
GCN Circular #5058
S. B. Cenko (Caltech) and D. B. Fox (Penn State) report on behalf of a larger collaboration:
We have re-imaged the field of GRB 060501 (La Parola et al., GCN 5040) with the automated Palomar 60-inch telescope. 5 x 150 s images were taken in the i filter at a mean epoch of approximately 10:54 2 May 2006 UT (~ 26.7 hours after the burst). The afterglow candidate identified by Fox and Cenko (GCN 5044; see also Halpern and Mirabal, GCN 5046) is clearly visible and has not faded significantly since our previous observations, over 24 hours earlier. We therefore consider it unlikely to be the afterglow of GRB 060501.
In addition, we find no evidence for variability in any sources in the near vicinity of the XRT error circle (La Parola et al., GCN 5042). We re-iterate the following limits for any afterglow emission in the XRT error circle from our previous notice:
```
Limiting Magnitude		Mean Time Since Burst
---------------------------------------------------------------------
I > 19.0			43 min
I > 21.0			92 min
```
No further observations are planned.

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Jochen Greiner, last update: 02-May-2006 [Disclaimer]