Gamma-ray Burst 081001

(All information courtesy of the instrument teams.)

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SuperAGILE NOTICE
NOTICE_DATE:     Wed 01 Oct 08 22:43:00 UT
NOTICE_TYPE:     SuperAGILE GRB Ground Position
TRIGGER_NUM:     691
GRB_RA:          276.576d {+18h 26m 18s} (J2000),
                 276.696d {+18h 26m 47s} (current),
                 275.893d {+18h 23m 34s} (1950)
GRB_DEC:          -8.754d {-08d 45' 13"} (J2000),
                  -8.748d {-08d 44' 53"} (current),
                  -8.784d {-08d 47' 02"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical plus systematic]
GRB_INTEN:       240.106   207.792 [X & Y cnts]
GRB_SIGNIF:      9.53  7.45 [sigma]
GRB_DATE:        14740 TJD;   275 DOY;   08/10/01
GRB_TIME:        76665.00 SOD {21:17:45.00} UT
SUN_POSTN:       188.38d {+12h 33m 30s}   -3.61d {-03d 36' 47"}
SUN_DIST:         87.79 [deg]   Sun_angle= -5.9 [hr] (East of Sun)
MOON_POSTN:      215.39d {+14h 21m 34s}  -19.42d {-19d 25' 09"}
MOON_DIST:        60.12 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:       22.28,  1.54 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      276.71, 14.53 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SuperAGILE GRB Coordinates.  
COMMENTS:        This is a GRB.  
COMMENTS:        SuperAGILE ground GRB coordinates

red DSS finding chart ps-file
GCN Circular #8305
F. Lazzarotto, E. Del Monte, I. Donnarumma, Y. Evangelista, M. Feroci, L. Pacciani, P. Soffitta, E. Costa, I. Lapshov, M. Rapisarda (INAF/IASF Rome), A. Giuliani, S. Vercellone, A. Chen, S. Mereghetti, A. Pellizzoni, F. Perotti, F. Fornari, P. Caraveo (INAF/IASF Milan), A. Bulgarelli, F. Gianotti, M. Trifoglio, G. Di Cocco, C. Labanti, F. Fuschino, M. Marisaldi, M. Galli, (INAF/IASF Bologna), M. Tavani, G. Pucella, F. D'Ammando, V. Vittorini, A. Argan, A. Trois (INAF/IASF Rome), G. Barbiellini, F. Longo (INFN Trieste), P. Picozza, A. Morselli (INFN Roma-2), M. Prest, E. Vallazza (Universita` dell'Insubria), P. Lipari, D. Zanello (INFN Roma-1), and P. Giommi, C. Pittori, B. Preger, P. Santolamazza, F. Verrecchia (ASDC) and L. Salotti (ASI), on behalf of the AGILE Team, report:
"SuperAGILE detected a gamma ray burst on 1st October 2008, at 21:17:42 UT. The event had a duration of about 40 s in the 20-60 keV energy range, with a first 10-s long bright peak, followed by a second broad peak about 20s apart. Assuming a Crab-like energy spectrum, the peak flux on 1-s timescale was about 6 ph/cm2/s or 5E-07 erg/cm2/s (20-60 keV). The burst position was reconstructed as (RA, Dec) (276.576 deg, -8.754 deg), which is:
```
RA(J2000)  = 18h 26m 18.34s
Dec(J2000) = -8d 45' 14.65"
```
with an uncertainty of 3' radius. The given uncertainty accounts for both the statistical and systematic errors.
An analysis of the AGILE Gamma Ray Imager (GRID) data is in progress."
This message may be cited.
GCN Circular #8306
Martin Jelinek, Rene Duffard, Pablo Santos Sanz and Alberto J. Castro Tirado (IAA CSIC Granada) report on behalf of a larger collaboration:
We observed the errorbox of the SuperAGILE GRB081001 (Lazzarotto et al., GCN 8305) with the 40cm ASH-Centurion telescope at Cerro Burek in Argentina starting at 23:28 UT.
The combined 600s unfiltered image with exposure mid-time 2.30h after the GRB trigger does not reveal any new source down to limiting magnitude of ~19.0 in comparison to the Digitized Sky Survey.
This message may be cited.
GCN Circular #8307
K.L. Page (U. Leicester) and H.A. Krimm (CRESST/GSFC/USRA) report on behalf of the Swift-XRT team:
Swift-XRT started observing the field of the SuperAGILE GRB 081001 (Lazzarotto et al., GCN Circ. 8305) 15.5 ks after the trigger. A single, fading source was identified within the SuperAGILE error circle, which we identify as the X-ray afterglow.
Using 4307 s of XRT Photon Counting mode data and 4 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 = 276.59076, -8.71903 which is equivalent to:
```
RA (J2000):   18 26 21.78
Dec (J2000): -08 43 08.5
```
with an uncertainty of 2.0 arcsec (radius, 90% confidence).
This circular is an official product of the Swift-XRT team.
GCN Circular #8308
E. A. Hoversten (PSU), and H.A. Krimm (CRESST/GSFC/USRA) report on behalf of the Swift UVOT team:
The Swift/UVOT began observations of the field of GRB 081001 14.5 ks after the SuperAGILE dectection (Lazzarotto et al., GCN Circ. 8305). No afterglow is detected within the Swift XRT error circle (Page et al., GCN 8307) in any of the observed UVOT filters.
UVOT magnitude 3-sigma upper limits are reported in the following table:
```
Filter   T_start   T_stop   Exp(s)  Mag (3-sigma upper limit)
-------------------------------------------------------------
v         16285    22214      350       > 19.84
b         15213    21209      416       > 20.90
u         14997    20992      416       > 20.51
uvw1      14568    20776      834       > 20.84
uvm2      16502    16696      191       > 19.81
uvw2      15431    22064     1670       > 21.65
```
The quoted upper limits have not been corrected for the large expected Galactic extinction along the line of sight of E(B-V) = 2.63 mag (Schlegel et al., 1998). All photometry is on the UVOT photometry system described in Poole et al. (2008, MNRAS, 383, 627).
GCN Circular #8310
A. de Ugarte Postigo (ESO, Santiago), F. Aceituno, M. Jel=EDnek, J. Gorosabel and A.J. Castro-Tirado (IAA-CSIC, Granada) on behalf of a larger collaboration report,
We have observed the field of the SuperAGILE GRB 081001 (Lazzarotto et al., GCN 8305) and in particular the Swift/XRT error box (Page et al., GCN 8307) from the 1.5m OSN telescope at Sierra Nevada Observatory in Granada (Spain). The observation consisted of 3x300s I-band exposures with a mean time of Oct 2.8348 UT (22.7 hours after the burst). We detect just one source on the edge of the XRT error box, located at the following coordinates (J2000 +/- 0.7"):
```
R.A.: 18:26:21.65
Dec.: -08:43:07.6
```
With a magnitude of I =3D 19.90+/-0.26 as compared to several USNO-B1 stars. A finding chart (with the object is marked as A) can be found in: http://www.sc.eso.org/~adeugart/GRB/081001/081001.gif No variability can be established at this point. Rechecking of the unfiltered image reported by Jel=EDnek et al. (GCN 8306) does not show any significant emission at the location of the object. Further observations would be needed in order to determine any relation of this source with the GRB.
GCN Circular #8322
A. de Ugarte Postigo (ESO, Santiago), F. Aceituno, M. Jel=EDnek, J. Gorosabel and A.J. Castro-Tirado (IAA-CSIC, Granada) on behalf of a larger collaboration report,
We have observed again the field of GRB 081001 (Lazzarotto et al., GCN 8305, Page et al., GCN 8307) from the 1.5m OSN telescope at Sierra Nevada Observatory in Granada (Spain). In a combined 5x300s exposure in I-band we still detect the source reported in our previous GCN (de Ugarte Postigo et al. GCN 8310) with no variation in brightness indicating that it is probably unrelated with the GRB. No further source is detected within the XRT error box. The 3-sigma limiting magnitudes of the images obtained from OSN are I > 20.7 0.95 days after the burst and I > 21.2 1.94 days after the burst.
GCN Circular #8353
S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, P. Oleynik, D. Svinkin, M. Ulanov and T. Cline, on behalf of the Konus-Wind team report:
The GRB 081001 localized by SuperAGILE (Lazzarotto et al., GCN 8305) triggered Konus-Wind at T0=76663.649 s UT (21:17:43.649).
The burst light curve shows a main pulse with a duration of ~6 s followed by a much weaker pulse at T0+~30 s with a duration of ~10 s.
As observed by Konus-Wind the burst had a fluence of 9.70(-0.86, +1.00)x10^-6 erg/cm2, and a 64-ms peak flux measured from T0+0.688 s of 5.63(-1.12, +1.16)x10^-6 erg/cm2/s (both in the 20 keV - 2 MeV energy range).
The spectrum of the main pulse (from T0 to T0+8.448 s) is well fitted (in the 20 keV-2 MeV range) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.99(-0.18, +0.21), and Ep = 239(-32, +45) keV (chi2 = 54.9/61 dof). Fitting by GRBM (Band) model yields: the low-energy photon index is alpha = -0.95(-0.21, +0.48), the high energy photon index beta < -2.14, the peak energy Ep = 227(-70, +52) keV (chi2 = 54.1/60 dof). All the quoted errors are at the 90% confidence level.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB081001_T76663/

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Jochen Greiner, last update: 10-Oct-2008 [Disclaimer]