Gamma-ray Burst 100518A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Tue 18 May 10 11:34:00 UT
NOTICE_TYPE:    INTEGRAL Wakeup
TRIGGER_NUM:    6014,   Sub_Num: 0
GRB_RA:         304.8075d {+20h 19m 14s} (J2000),
                304.9621d {+20h 19m 51s} (current),
                304.0618d {+20h 16m 15s} (1950)
GRB_DEC:        -24.5437d {-24d 32' 36"} (J2000),
                -24.5107d {-24d 30' 38"} (current),
                -24.7012d {-24d 42' 03"} (1950)
GRB_ERROR:      2.82 [arcmin, radius, statistical only]
GRB_INTEN:      13.10 [sigma]
GRB_TIME:       41627.05 SOD {11:33:47.05} UT
GRB_DATE:       15334 TJD;   138 DOY;   10/05/18
SC_RA:          300.53 [deg] (J2000)
SC_DEC:         -31.60 [deg] (J2000)
SUN_POSTN:       55.15d {+03h 40m 36s}  +19.58d {+19d 35' 02"}
SUN_DIST:       115.78 [deg]   Sun_angle= 7.3 [hr] (West of Sun)
MOON_POSTN:     116.13d {+07h 44m 31s}  +20.26d {+20d 15' 54"}
MOON_DIST:      170.80 [deg]
GAL_COORDS:      18.66,-29.47 [deg] galactic lon,lat of the burst
ECL_COORDS:     301.41, -4.82 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Possibly real GRB event

red DSS finding chart ps-file

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Tue 18 May 10 11:36:59 UT
NOTICE_TYPE:    INTEGRAL Refined
TRIGGER_NUM:    6014,   Sub_Num: 1
GRB_RA:         304.8049d {+20h 19m 13s} (J2000),
                304.9595d {+20h 19m 50s} (current),
                304.0592d {+20h 16m 14s} (1950)
GRB_DEC:        -24.5367d {-24d 32' 11"} (J2000),
                -24.5037d {-24d 30' 12"} (current),
                -24.6942d {-24d 41' 38"} (1950)
GRB_ERROR:      2.77 [arcmin, radius, statistical only]
GRB_INTEN:      14.48 [sigma]
GRB_TIME:       41635.13 SOD {11:33:55.13} UT
GRB_DATE:       15334 TJD;   138 DOY;   10/05/18
SC_RA:          300.53 [deg] (J2000)
SC_DEC:         -31.60 [deg] (J2000)
SUN_POSTN:       55.15d {+03h 40m 37s}  +19.58d {+19d 35' 04"}
SUN_DIST:       115.78 [deg]   Sun_angle= 7.3 [hr] (West of Sun)
MOON_POSTN:     116.16d {+07h 44m 39s}  +20.26d {+20d 15' 26"}
MOON_DIST:      170.83 [deg]
GAL_COORDS:      18.66,-29.47 [deg] galactic lon,lat of the burst
ECL_COORDS:     301.40, -4.81 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Possibly real GRB event

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Tue 18 May 10 12:21:55 UT
NOTICE_TYPE:    INTEGRAL Offline
TRIGGER_NUM:    6014,   Sub_Num: 2
GRB_RA:         304.7997d {+20h 19m 12s} (J2000),
                304.9543d {+20h 19m 49s} (current),
                304.0539d {+20h 16m 13s} (1950)
GRB_DEC:        -24.5607d {-24d 33' 38"} (J2000),
                -24.5277d {-24d 31' 39"} (current),
                -24.7181d {-24d 43' 04"} (1950)
GRB_ERROR:      1.60 [arcmin, radius, statistical only]
GRB_INTEN:      14.48 [sigma]
GRB_TIME:       41635.13 SOD {11:33:55.13} UT
GRB_DATE:       15334 TJD;   138 DOY;   10/05/18
SC_RA:          300.53 [deg] (J2000)
SC_DEC:         -31.60 [deg] (J2000)
SUN_POSTN:       55.18d {+03h 40m 44s}  +19.59d {+19d 35' 28"}
SUN_DIST:       115.82 [deg]   Sun_angle= 7.3 [hr] (West of Sun)
MOON_POSTN:     116.61d {+07h 46m 27s}  +20.14d {+20d 08' 26"}
MOON_DIST:      171.13 [deg]
GAL_COORDS:      18.64,-29.47 [deg] galactic lon,lat of the burst
ECL_COORDS:     301.39, -4.83 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       refined_coordinates_after_offline_analysis

GCN Circular #10772
S.Mereghetti, A. Paizis (IASF- Milano), D.Gotz (CEA-Saclay), E. Bozzo, C.Ferrigno, P. Bordas, M. Beck (ISDC, Versoix), and J. Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report:
a long gamma ray burst has been detected by IBAS in the IBIS/ISGRI data at 11:33:35 U.T. on May 18th. It has a FRED light curve lasting about 30 s. Its refined coordinates (J2000) are:
```
R.A.:     304.7999 [deg]
DEC.:    -24.5609  [deg]
```
with an uncertainty of 1.6 arcmin (90% c.l.).
A preliminary analysis gives a peak flux in the 20-200 keV range of about 0.5 ph/cmsq/s (1 s integration time) and a fluence over the same energy range of about 5 10e-7 erg/cmsq.
A plot of the light curve will be posted at
http://ibas.iasf-milano.inaf.it/IBAS_Results.html
This message can be cited.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 18 May 10 14:23:19 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     20138,   Seg_Num: 1
GRB_RA:          304.7890d {+20h 19m 09.35s} (J2000),
                 304.9436d {+20h 19m 46.46s} (current),
                 304.0432d {+20h 16m 10.36s} (1950)
GRB_DEC:         -24.5543d {-24d 33' 15.4"} (J2000),
                 -24.5213d {-24d 31' 16.5"} (current),
                 -24.7117d {-24d 42' 41.9"} (1950)
GRB_ERROR:       4.4 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15334 TJD;   138 DOY;   10/05/18
IMG_START_TIME:  51173.00 SOD {14:12:53.00} UT,   9558.0 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        55.27d {+03h 41m 04s}  +19.61d {+19d 36' 35"}
SUN_DIST:        115.91 [deg]   Sun_angle= 7.4 [hr] (West of Sun)
MOON_POSTN:      117.84d {+07h 51m 20s}  +19.82d {+19d 49' 11"}
MOON_DIST:       171.91 [deg]
MOON_ILLUM:      24 [%]
GAL_COORDS:       18.64,-29.46 [deg] galactic lon,lat of the burst
ECL_COORDS:      301.39, -4.83 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice is generated as a result of an uploaded TOO -- this is not a normal BAT-detected burst.  
COMMENTS:        And the IMG_START_DATE/TIME fields are the current epoch -- not the original detection.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 1.1% < P(seren) < 2.8%.

GCN Circular #10775
M. Stamatikos (OSU/NASA/GSFC), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), M. M. Chester (PSU), P. A. Evans (U Leicester), J. M. Gelbord (PSU), J. A. Kennea (PSU), C. Pagani (U Leicester), J. L. Racusin (NASA/GSFC) and L. Vetere (PSU) report on behalf of the Swift Team:
Swift began a target of opportunity observation of GRB 100518A on May 18, 2010 at 14:10 UT, approximately 2.6 hours after the burst was detected by INTEGRAL. Swift data for these observations utilize Target ID 20138.
The XRT began observing the field at 14:12:42.5 UT, 9.5 ks after the INTEGRAL trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 304.78875, -24.55459 which is equivalent to:
```
   RA(J2000)  = 20h 19m 9.30s
   Dec(J2000) = -24d 33' 16.5"
```
with an uncertainty of 4.1 arcseconds (radius, 90% containment). This location is 42 arcseconds from the INTEGRAL position, within the INTEGRAL error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 6.4e+20 cm^-2 (Kalberla et al. 2005).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 9551 seconds after the INTEGRAL trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.07.
Burst Advocate for this burst is M. Stamatikos (Michael.Stamatikos-1 AT nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
GCN Circular #10776
Z. Cano (Liverpool JMU), A. Gomboc (U. Ljubljana), C. Guidorzi (U. Ferrara) report on behalf of a larger collaboration:
On 2010 May 18 at 11:37:46 UT the 2-m Faulkes Telescope North automatically began observing the INTEGRAL GRB 100518A (Mereghetti et al., GCN 10772).
The LT-TRAP automatically detected a fading object in R and i at the following position:
```
Ra:   20:19:09.33
Dec: -24:33:16.50 (J2000)
```
This lies 0.4 arcseconds from the XRT centroid (Stamatikos et al., GCN 10775).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 18 May 10 15:01:53 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     20138,   Seg_Num: 1
GRB_RA:          304.7884d {+20h 19m 09.21s} (J2000),
                 304.9430d {+20h 19m 46.31s} (current),
                 304.0426d {+20h 16m 10.21s} (1950)
GRB_DEC:         -24.5549d {-24d 33' 17.6"} (J2000),
                 -24.5219d {-24d 31' 18.7"} (current),
                 -24.7123d {-24d 42' 44.1"} (1950)
GRB_ERROR:       4.0 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15334 TJD;   138 DOY;   10/05/18
IMG_START_TIME:  51173.00 SOD {14:12:53.00} UT,   9558.0 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        55.29d {+03h 41m 11s}  +19.62d {+19d 36' 56"}
SUN_DIST:        115.94 [deg]   Sun_angle= 7.4 [hr] (West of Sun)
MOON_POSTN:      118.22d {+07h 52m 53s}  +19.72d {+19d 42' 57"}
MOON_DIST:       172.14 [deg]
MOON_ILLUM:      24 [%]
GAL_COORDS:       18.64,-29.46 [deg] galactic lon,lat of the burst
ECL_COORDS:      301.39, -4.83 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice is generated as a result of an uploaded TOO -- this is not a normal BAT-detected burst.  
COMMENTS:        And the IMG_START_DATE/TIME fields are the current epoch -- not the original detection.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 1.1% < P(seren) < 2.8%.

GCN Circular #10778
A. de Ugarte Postigo (INAF-OAB), A.J. Castro-Tirado, J. Gorosabel, M. Jelinek (IAA-CSIC), P. Kubanek (IPL UV, IAA-CSIC), R. Cunniffe, S. Guziy (IAA-CSIC), P. Yock (Auckland Univ.), W.H. Allen (Vintage Lane Obs.), I. Bond (Massey Univ.), G. Christie (Stardome Obs.) report on behalf of a larger collaboration:
"We have observed the field of the INTEGRAL GRB 100518A (Mereghetti et al., GCN 10772) using the 0.6m Yock-Allen robotic telescope (BOOTES-3) located in Blenheim, New Zealand. Preliminary analysis of a combined 40x60s unfiltered exposure taken (mid-epoch) on 18th May 2010, 14:01 UT (2.47 hours after the burst, when acceptable weather allowed to perform the observations) does not show any source at the position of the optical afterglow candidate (Cano et al., GCN 10776) down to a 3-sigma limiting magnitude of R ~ 20.7 using USNO-B1.0 as photometric reference."
GCN Circular #10779
D. Kopac (U. Ljubljana), C. Guidorzi (U. Ferrara), Z. Cano (Liverpool JMU), A. Gomboc (U. Ljubljana), report on behalf of a larger collaboration:
The 2-m Faulkes Telescope North observed the optical afterglow of GRB 100518A (Cano et al. GCN Circ. 10776) from 4.2 min to 3.7 hours from the INTEGRAL trigger time (Mereghetti et al. GCN Circ. 10772) in the BVRi filters. Within this time interval the afterglow is observed to decay in both R and i filters with an average power-law decay slope of 0.7 +/- 0.1, with the following initial magnitudes:
```
Mid time from   Total Exp   Filter    Magnitude
trigger (min)    (s)
-------------------------------------------------
4.9             3x10        R         19.4 +- 0.1
9.8             10          i         18.8 +- 0.2
-------------------------------------------------
```
Magnitudes have been calibrated from nearby USNOB-1 stars.
GCN Circular #10780
A. P. Beardmore, R. L. C. Starling, P. A. Evans (U. Leicester) and M. Stamatikos (OSU/NASA/GSFC) report on behalf of the Swift-XRT team:
We have analysed 4.7 ks of XRT data for the INTEGRAL triggered GRB 100518A (Mereghetti et al. GCN Circ. 10772, Stamatikos et al. GCN Circ. 10775), from 9.6 ks to 17.9 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. Using 2.4 ks of PC mode data and 3 UVOT images we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 304.78931, -24.55436 which is equivalent to:
```
RA (J2000): 20h 19m 9.43s
Dec (J2000): -24d 33' 15.7"
```
with an uncertainty of 2.2 arcsec (radius, 90% confidence). Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.68 +1.00 -0.96.
A spectrum formed from the entire PC mode dataset can be fitted with an absorbed power-law with a photon spectral index of 3.6 +1.4 -0.7. The best-fitting absorption column is (4.5 +3.5 -3.3) x 10^21 cm^-2, in excess of the Galactic value of 6.4 x 10^20 cm^-2 in the direction of the burst (Kalberla et al. 2005). The observed (unabsorbed) 0.3-10 keV flux for this spectrum is 6.1 x 10^-13 (5.4 x 10^-12) erg cm^-2 s^-1, resulting in a counts to observed (unabsorbed) 0.3-10 keV flux conversion factor of 2.7 x 10^-11 (2.4 x 10^-10) erg cm^-2 count^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020138.
This circular is an official product of the Swift-XRT team.
GCN Circular #10781
P.A. Curran (MSSL-UCL) and M. Stamatikos (OSU/NASA/GSFC) report on behalf of the Swift/UVOT team:
During Swift target of opportunity observations of GRB 100518A (Stamatikos et al. GCN Circ. 10775), Swift/UVOT began settled observations starting 9551 seconds after the INTEGRAL trigger (Mereghetti et al. GCN Circ. 10772). No optical afterglow consistent with the enhanced XRT position (Beardmore et al. GCN Circ. 10780) or the optical counterpart (Cano et al. GCN Circ. 10776) is detected in the UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter   T_start(s)   T_stop(s)   Exp(s)   Mag
------------------------------------------------
white    9551         9701        147      >21.4 (FC)
white    9551         11529       1033     >22.4
v        16324        17231       885      >20.7
b        9711         10618       885      >21.7
m2       17236        17899       652      >20.9
w2       11536        16318       1137     >21.6
```
The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.07 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #10782
P. Afonso, P. Schady, T. Kruehler and J. Greiner (all MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 100518A (Mereghetti et al., GCN 10772) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPI/ESO telescope at La Silla Observatory (Chile).
Observations started at 09:12 UT on May 19, 21.7 hours after the GRB trigger, and continued for 1 hour.
In stacked images of 50 min total integration time in g'r'i'z' we detect the optical afterglow (Cano et al., GCN 10776) in r'i' and z'.
Preliminary photometry yields the following AB magnitudes and upper limits:
```
g' > 25.3
r' = 23.8 +- 0.1
i' = 23.6 +- 0.2
z' = 23.5 +- 0.2
```
calibrated against the GROND zeropoints and 2MASS field stars. After correcting for the foreground reddening of E(B-V)=0.07 (Schlegel et al. 1998) and assuming no intrinsic extinction, a fit with Hyper-z (Bolzonella et al. 2000) results in a preliminary photometric redshift of z = 4.0+0.3-0.5.

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Jochen Greiner, last update: 18-May-2010 [Disclaimer]