Gamma-ray Burst 100331A

(All information courtesy of the instrument teams.)

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Wed 31 Mar 10 00:30:43 UT
NOTICE_TYPE:    INTEGRAL Wakeup
TRIGGER_NUM:    5994,   Sub_Num: 0
GRB_RA:         261.1120d {+17h 24m 27s} (J2000),
                261.3369d {+17h 25m 21s} (current),
                260.0158d {+17h 20m 04s} (1950)
GRB_DEC:        -58.9479d {-58d 56' 51"} (J2000),
                -58.9566d {-58d 57' 23"} (current),
                -58.9023d {-58d 54' 07"} (1950)
GRB_ERROR:      3.25 [arcmin, radius, statistical only]
GRB_INTEN:      8.27 [sigma]
GRB_TIME:       1830.59 SOD {00:30:30.59} UT
GRB_DATE:       15286 TJD;    90 DOY;   10/03/31
SC_RA:          243.50 [deg] (J2000)
SC_DEC:         -57.93 [deg] (J2000)
SUN_POSTN:        9.37d {+00h 37m 28s}   +4.04d {+04d 02' 10"}
SUN_DIST:       102.68 [deg]   Sun_angle= 7.2 [hr] (West of Sun)
MOON_POSTN:     199.25d {+13h 17m 00s}  -13.49d {-13d 29' 10"}
MOON_DIST:       64.24 [deg]
GAL_COORDS:     332.35,-12.74 [deg] galactic lon,lat of the burst
ECL_COORDS:     264.37,-35.68 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Possibly real GRB event

red DSS finding chart ps-file
GCN Circular #10555
S.Mereghetti, A. Paizis, (IASF- Milano), D.Gotz (CES-Saclay), E. Bozzo, C. Ferrigno, M. Beck (ISDC, Versoix), and J. Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report:
a long GRB has been detected by IBAS in IBIS/ISGRI data at 00:30:30 UT of January 31. The refined coordinates (J200) are
```
RA: 261.0831 [degrees]
DEC: -58.943 [degrees]
  
```
with an uncertainty of 2.5 arcmin
The lightcurve shows a single peak lastiing about 15 s. A preliminary analysis gives a 20-200 keV fluence of 4 10e-7 erg/cm2 and a peak flux of 0.5 ph/cm2/s (1 sec bin).
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/INTEGRAL NOTICE
NOTICE_DATE:    Wed 31 Mar 10 07:24:57 UT
NOTICE_TYPE:    INTEGRAL Offline
TRIGGER_NUM:    5994,   Sub_Num: 1
GRB_RA:         261.0831d {+17h 24m 20s} (J2000),
                261.3079d {+17h 25m 14s} (current),
                259.9869d {+17h 19m 57s} (1950)
GRB_DEC:        -58.9429d {-58d 56' 33"} (J2000),
                -58.9516d {-58d 57' 05"} (current),
                -58.8971d {-58d 53' 49"} (1950)
GRB_ERROR:      2.50 [arcmin, radius, statistical only]
GRB_INTEN:      8.27 [sigma]
GRB_TIME:       1830.59 SOD {00:30:30.59} UT
GRB_DATE:       15286 TJD;    90 DOY;   10/03/31
SC_RA:          243.50 [deg] (J2000)
SC_DEC:         -57.93 [deg] (J2000)
SUN_POSTN:        9.63d {+00h 38m 31s}   +4.15d {+04d 08' 51"}
SUN_DIST:       102.92 [deg]   Sun_angle= 7.2 [hr] (West of Sun)
MOON_POSTN:     203.21d {+13h 32m 51s}  -14.97d {-14d 58' 23"}
MOON_DIST:       61.01 [deg]
GAL_COORDS:     332.35,-12.73 [deg] galactic lon,lat of the burst
ECL_COORDS:     264.35,-35.68 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       refined_coordinates_after_offline_analysis

GCN Circular #10557
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, report:
We have observed the field of the INTEGRAL GRB 100331A (Mereghetti et al. GCN 10555) using the 0.6 Yock-Allen robotic telescope (BOOTES-3) located in Blenheim, New Zealand starting at 07:12 UT (6.7 hours after the burst). In a 35x60s combined exposure with clear filter, obtained under non optimal conditions, we do not detect any new source within the full INTEGRAL error circle down to a 3-sigma limiting magnitude of R~17.8. Further analysis is ongoing.
GCN Circular #10558
```
TITLE:   GCN CIRCULAR
NUMBER:  10558 
SUBJECT: INTEGRAL trigger 5994 / GRB 100331A: GROND detection of a variable
+source  
DATE:    10/03/31 15:23:42 GMT 
FROM:    Jochen Greiner at MPI  
```
Adria Updike (Clemson University), Arne Rau, Felipe Olivares, and Jochen Greiner (all MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 100331A (INTEGRAL trigger 5994; S. Mereghetti et al., GCN 10555) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m ESO/MPI telescope at La Silla Observatory (Chile).
Observations started at 03:55 UT on March 31st 2010, 3.42 hours after the Swift trigger, and a second epoch was obtained starting at 09:37 UT. They were performed at an average seeing of 1" and at airmasses of 2.4 and 1.15, respectively.
We found a single variable point source within the 2.5' INTEGRAL error circle reported by S. Mereghetti et al. at
```
RA  (J2000.0) =  17h 24m 18.61s
DEC (J2000.0) = -58d 56' 52.0" 
```
with an uncertainty of 0.5" in each coordinate. From the last epoch we estimate preliminary magnitudes (all in AB system) of the
```
g' = 16.7 +/- 0.1 mag,
r' = 16.3 +/- 0.1 mag,
i' = 16.4 +/- 0.1 mag,
z' = 16.2 +/- 0.1 mag,
J  = 16.3 +/- 0.1 mag,
H  = 16.5 +/- 0.1 mag
K  = 16.9 +/- 0.1 mag,
```
calibrated against GROND zeropoints, and not corrected for the expected galactic foreground extinction of E(B-V)=0.12 mag (Schlegel et al. 1998).
During the observations the source varied by 0.4 mag in the g' and only 0.2 mag in J, with no obvious fading over the 5.5 hrs. Both, the SED shape and the color evolution are different from any GRB afterglow observed so far with GROND. Though the object lies within 20 arcsec of the center of the INTEGRAL error circle, and the chance coincidence with a variable object within the 2.5 arcmin error circle is about 10^-4, the relation of this variable to the INTEGRAL trigger is likely, but cannot be proven at this stage.
We note the presence of an object in both, USNO and 2MASS at the location of the variable source. The 2MASS magnitudes are similar to our last epoch, bright state measurement, indicating that this object is a long-term variable. This excludes that this object is an host galaxy unresolved in our images. Spectroscopic observations are encouraged to establish the nature of this source.
GCN Circular #10559
G. Stratta, V. D'Elia, M. Perri (ASDC) report on behalf of the Swift Team:
Swift began a target of opportunity observation of the INTEGRAL detected GRB 100331A (Mereghetti et al., GCN #10555), at 14:29UT on March 31st, 2010, approximately 14 hours after the INTEGRAL detection. In 1890 s of Photon Counting mode data, no X-ray source is detected inside the INTEGRAL error cirlce.
This circular is an official product of the Swift-XRT team.

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Jochen Greiner, last update: 31-Mar-2010 [Disclaimer]