Gamma-ray Burst 050326

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 26 Mar 05 13:51:28 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     112453,   Seg_Num: 0 
GRB_RA:            6.857d {+00h 27m 26s} (J2000), 
                   6.914d {+00h 27m 39s} (current),
                   6.312d {+00h 25m 15s} (1950)
GRB_DEC:         -71.375d {-71d 22' 29"} (J2000), 
                 -71.346d {-71d 20' 45"} (current),
                 -71.652d {-71d 39' 05"} (1950) 
GRB_ERROR:       4.00 [arcmin radius, statistical only]
GRB_INTEN:       9418 [cnts]    Peak=18395 [cnts/sec]
TRIGGER_DUR:     0.512 [sec]   
TRIGGER_INDEX:   127     E_range: unknown_E_range keV
BKG_INTEN:       45757 [cnts]
BKG_TIME:        35624.00 SOD {09:53:44.00} UT
BKG_DUR:         8 [sec]
GRB_DATE:        13455 TJD;    85 DOY;   05/03/26
GRB_TIME:        35635.58 SOD {09:53:55.58} UT
GRB_PHI:         -71.37 [deg]
GRB_THETA:        26.55 [deg]    
SOLN_STATUS:     0x3 
RATE_SIGNIF:     116.09 [sigma]
IMAGE_SIGNIF:    21.00 [sigma]
MERIT_PARAMS:     +0  +1  +0  +0  -1  +3 +24  +0  +0 -28
SUN_POSTN:         5.36d {+00h 21m 28s}   +2.32d {+02d 19' 15"}
SUN_DIST:         73.67 [deg]
MOON_POSTN:      191.70d {+12h 46m 48s}   -3.89d {-03d 53' 30"}
MOON_DIST:       104.70 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      305.67,-45.63 [deg] galactic lon,lat of the burst (or transient)   
ECL_COORDS:      312.84,-62.20 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.

red DSS finding chart ps-file
GCN notice #3143
C. Markwardt (GSFC/UMD), S. Barthelmy, L. Barbier (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD), H. Krimm (GSFC/USRA), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), M. Suzuki (Saitama), M. Tashiro (Saitama U.), J. Tueller (GSFC), N. White (GSFC), on behalf of the Swift team:
At 09:53:55 UT Swift-BAT detected trigger number 111453, a bright burst designated GRB050326. Due to a TDRSS-to-GCN problem there were no real-time notices. The BAT-derived position is (RA,Dec) = 6.857,-71.375 (J2000). The lightcurve has 5 peaks with a total duration of ~30 sec. The peak count rate is ~20,000 cnts/sec.
GCN notice #3144
D. N. Burrows, S. Hunsberger, S. Kobayashi (PSU) and A. Moretti (INAF-OAB) report on behalf of the Swift XRT team:
GRB 050326 was discovered by the Swift BAT instrument at 09:53:55 UT today (Markwardt et al. 2005, GCN 3143). The burst was within the Swift Earth constraint and observations were delayed by nearly an hour. When the XRT observed the field at 10:48:13 UT, there was no afterglow strong enough for an on-board centroid determination (which is normal when we observe this long after the burst). Unfortunately, this burst occurred during the daily 6 to 7 hour period when Swift is out of contact with the ground station, so we cannot perform ground analysis to search for an X-ray afterglow until about 19:00 UT. We will issue an updated GCN Circular once we can process those data.
GCN notice #3145
J. Cummings (GSFC/NRC), S. Barthelmy, L. Barbier (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), M. Suzuki (Saitama), M. Tashiro (Saitama U.), J. Tueller (GSFC), N. White (GSFC) on behalf of the Swift/BAT team:
At 09:53:55 UT Swift-BAT detected GRB 050326 (Markwardt et al. GCN Circ 3143). The refined BAT ground position is (RA,Dec) = 6.892, -71.376 [deg; J2000] +- 3 arcmin, (95% containment).
The burst had 6 distinct peaks, with several smaller peaks. There was an initial weak peak (at T-9) followed by a 10 times larger peak, which caused the trigger (defined as 0 seconds). Major peaks were at +5, +9, +19, and +23 seconds, all of similar spectral shape.
The fluence derived from the event data was 1.9 X 10^-5 erg/cm^2 in the 15-350 keV band. The 1-s peak flux was 17 ph/cm^2/s (also 15-350 keV). The photon index of the 1-s peak spectrum (T+0 s) was 0.98 +/- 0.05 (90% confidence). The time-averaged spectrum yields a photon index of 1.28 +/- 0.03 (90% confidence). The overall measure of burst duration was T90 = 29.5 +/- 2 s (including systematics) T50 was 19 seconds.
Clarification on recent BAT triggers and notices: This was BAT trigger number 111453, for which no real-time notices were sent. It was NOT trigger 112467, a provisional trigger, for which real-time notices WERE sent.
GCN notice #3146
M.Cwiok, K.Krupska, K.Kwiecinska, L.Mankiewicz, K.Nawrocki, B.Pilecki, L.W.Piotrowski, G.Pojmanski, M.Sokolowski, D.Szczygiel, G.Wrochna, on behalf of "Pi of the Sky / ASAS" collaboration http://grb.fuw.edu.pl
The GRB 050326 (GCN 3143) error box was observed by "Pi of the Sky" apparatus at Las Campanas Observatory at 9:20 UT, i.e. 33 min before the GRB. 3 exposures, 10s each, have been taken. No new object has been found within the Swift-BAT error box. The limiting magnitude on 3 coadded frames is 11m (unfiltered).
GCN notice #3147
A. Moretti, S. Campana, P. Romano, G. Chincarini (INAF-OAB), J. L. Racusin, D. N. Burrows (PSU), J. P. Osborne, A. P. Beardmore (U. Leicester), G. Cusumano, T. Mineo (INAF-IASF/Palermo), M. Perri, F. Tamburelli (ASDC), S. Hunsberger, S. Kobayashi, P. Meszaros (PSU), D. Malesani (INAF-OAB), and N. Gehrels (GSFC), report on behalf of the Swift XRT team:
The Swift XRT observed the field of GRB 050326 beginning at 10:48:14 UT. The instrument was in Auto State and attempted to calculate a centroid, but found only 7 photons in 2.5 seconds from the GRB position, insufficient to obtain an on-board centroid. Based on 335 seconds of Photon-Counting mode observations from the first orbit of data, we find a bright uncataloged X-ray source located at:
```
RA(J2000) = 0:27:48.7,
Dec(J2000) = -71:22:17.2
```
We estimate an uncertainty of about 6 arcseconds. This source is located 83 arcseconds from the BAT position given in GCN 3145.
GCN notice #3148
XMM-Newton will observe GRB 050326 (Swift-BAT trigger 111453, Markwardt et al. GCN Circ 3143, Cummings et al. GCN Circ 3145) at location (RA=00h 27m 34.1s, DEC=-71d 22' 33.6", J2000), starting at 18:27:00 UT, on March 26, 2005, for an exposure of 45800 seconds.
GCN notice #3149
M. Ehle and R. Perez Martinez report:
Quick-Look-Analysis of the XMM-Newton observation of the GRB 050326 field based on a 3 ks exposure in the EPIC pn camera that started at 19:34 UT, shows the presence of a source within the SWIFT/XRT error circle (Markwardt et al. GCN Circ 3143, Cummings et al. GCN Circ 3145, Moretti et al. GCN Circ 3147).
```
XMMU J002748.8-712217 (J2000):
R.A. = 00h 27m 48.8s  Decl. = -71deg 22' 17.6''
with an estimated EPIC/pn count rate of 0.68 [counts/sec];
```
At this stage of reduction the position error is expected to be less than 6''.
GCN notice #3150
S. T. Holland, M. Still (GSFC/USRA), W. Landsman (GSFC), Adam Morgan, S. Hunsberger (PSU), A. Breeveld (MSSL), P. Roming (PSU), K. Mason, P. Schady (MSSL), M. Ivanushkina (PSU), T. Poole (MSSL), C. Gronwall (PSU), A. Blustin (MSSL), P. Brown (PSU), S. Rosen, K. McGowan, M. De Pasquale (MSSL), P.Boyd (GSFC/UMBC), M. Carter, H. Huckle (MSSL), P. Broos (PSU), T. Kennedy, P. Smith, B. Hancock (MSSL), H. Krimm (GSFC/USRA), S. Kock (PSU), K. Gendreau (GSFC), M.Chester (PSU), J. Nousek (PSU), N. Gehrels (GSFC), on behalf of the Swift UVOT team.
The Swift Ultra-Violet/Optical Telescope (UVOT) began observing the field of GRB 050326 (GCN 3143) at 10:48:16 UT. The burst was within the Earth-limb constraint at the time of the BAT trigger and therefore Swift did not slew to this burst for about another 54 minutes. We detect no source at the location of the X-ray position (GCN 3147) in any filter. The 5-sigma limiting magnitude for the first 100s exposure taken in the V-filter is V > 18.91 +/- 0.12 mag, based on preliminary in-orbit zero points.
GCN notice #3151
P. Tristram (Univ. of Canterbury, New Zealand),=20 M. Jelinek, A. de Ugarte Postigo, J. Gorosabel, A.J. Castro-Tirado, (IAA-CSIC, Granada, Spain), J. M. Castro Cer=F3n (Univ. of Copenhagen, Denmark) and Ph. Yock (Univ. of Auckland, New Zealand) report:
We have imaged the error box provided by Swift (trigger 112453, GCN 3147) with the 0.6m telescope (+MOA camera) at Mt.John Observatory. A 600s second integration taken at 16:47:45 UT (ie. 6.90 hours after burst, mean obs. time) reveals no apparent source down to limiting mag. 20.3 in comparison with DSS. Observation was performed=20 with MOA broad R-band filter (similar to Ic).
GCN notice #3152
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T. Cline on behalf of the Konus-Wind team report:
A bright long multipeak GRB 050326 (Swift-BAT trigger 111453, GCN 3143) triggered Konus-Wind at 35633.347 s UT (09:53:53.347). As observed by Konus-Wind, it had a duration of ~38 s, fluence (3.22 =B1 0.05)10-5 erg/cm2, peak flux (6.0 =B1 0.3)10-6 erg/cm2/s (both in the 20 keV - 3 MeV energy range). Time-integrated spectrum of the burst is fitted with the GRB (Band) model. The low-energy photon index is alpha =3D -0.74 =B1 0.09, the high energy photon index beta =3D -2.49 =B1 0.16, and the break energy E0 =3D 160 =B1 22 keV. The peak energy is Ep =3D 201 =B1 24 keV.
GCN notice #3293
Andrea De Luca (IASF Mi), Diego Gotz (IASF Mi), Sergio Campana (OAB) on behalf of a larger collaboraton report:
We have analyzed the data from the XMM-Newton observation of GRB050326, discovered by Swift on 2005, Mar 26, 09:53:55 UTC (Markwardt et al., GCN3143).
The XMM-Newton observation started on 2005, Mar. 26 at 18:25 UTC and lasted for ~45.8 ks.
A high particle background level affects the whole observation, with several soft proton flares, particularly evident in pn data.
We improved the astrometry of the XMM-Newton/EPIC images by matching X-ray sources in the field to stars in the USNO-B1 catalogue. The refined position (J2000) for the X-ray afterglow is
RA: 00h 27m 49.1s Dec: -71d 22' 16.3"
The 1 sigma error radius is 1.5 arcsec (including the rms error on the cross-correlation as well as systematic uncertainties in the optical catalogue). The position is fully consistent with the XRT coordinates (Moretti et al., GCN3147) as well as with the preliminary XMM-Newton position by Ehle & Perez-Martinez (GCN3149).
The MOS light curve (0.3-8 keV) is well fitted by a power law decay with index delta=1.81+/-0.11 (90% confidence level), with a reduced chi2 of 0.6 (21 dof). Adding pn data (with a larger bkg contamination) yields fully consistent results (delta=1.85+/-0.10), but with a poorer fit quality (owing to bkg fluctuations).
We extracted time-averaged spectra from the three EPIC cameras and we generated ad-hoc response files. We quote here errors at 90% confidence level for a single interesting parameter unless otherwise specified. A simultaneous fit with an absorbed power law model yields a reduced chi2 of 1.11 (241 dof). The resulting NH=(1.20+/-0.15)x10^21 cm^-2 is higher than the expected Galactic value in the burst direction (NH=4.5x10^20 cm^-2, Dickey & Lockman, 1990); the best fitting power law photon index is Gamma=2.10+/-0.05.
A better fit (reduced chi2=1.05, 240 dof) may be obtained fixing the NH to the expected Galactic value (NH=4.5x10^20 cm^-2) and adding a neutral, redshifted absorber component to the spectral model. With a simple F-test we evaluate the chance occurrence probability of the improvement to be of 2.6x10^-4. Such model yields an intrinsic NH>3x10^21 and a redshift z>1 (90% confidence level for 2 parameters of interest). However, neither the intrinsic column density nor the redshift are well constrained towards large values, owing to the lack of absorption edges in the spectrum. The resulting power law photon index is Gamma=2.01+/-0.05. The observed flux is of 5.2x10^-13 erg cm^-2 s^-1 in 0.2-10 keV; the corresponding unabsorbed flux is of 7.4x10^-13 erg cm^-2 s^-1.
Finally, we divided the dataset into two time intervals of ~15900 s and ~27600 s (each containing about half of the counts from the afterglow) and we repeated the spectral analysis. We found no significant spectral changes in the two considered intervals.
This message may be cited.
astro-ph/0512392 from 15 Dec 2005
Moretti: Swift and XMM observations of the dark GRB 050326
We present Swift and XMM observations of GRB 050326, detected by Swift-BAT. The fluence was 7.7x10^-6 erg cm^-2 (20-150 keV), and its spectrum was hard, with a power law photon index 1.25. The afterglow light curve did not show any break nor flares between ~1 hr and ~6 d after the burst, and decayed with a slope 1.70. The afterglow spectrum is well fitted by a power-law model, suffering absorption both in the Milky Way and in the host galaxy. The rest-frame Hydrogen column density is significant, N_H_z > 4x10^21 cm^-2, and the redshift of the absorber is z > 1.5. There was good agreement between the Swift-XRT and XMM results. By comparing the prompt and afterglow fluxes, we found that an early break occurred before the XRT observation. The properties of the GRB 050326 afterglow are well described by a spherical fireball expanding in a uniform external medium, so a further steepening is expected at later times. The lack of such a break constrains the jet angle to be >7 deg. Using the redshift constraints provided by the X-ray analysis, we also estimated that the beaming-corrected gamma-ray energy was >3x10^51 erg, at the high end of GRB energies. Despite the brightness in X rays, only deep limits could be placed by Swift-UVOT at optical/UV wavelengths. Thus, this GRB was "truly dark", with the optical-to-X-ray spectrum violating the synchrotron limit. The optical and X-ray observations are consistent either with an absorbed event or with a high-redshift one. To obey the Ghirlanda relation, a moderate/large redshift z>4.5 is required. (abridged)
GCN Circular #5270
```
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5270
SUBJECT: GRB050326: Host Galaxy Candidates
DATE:    06/06/16 21:44:18 GMT
FROM:    Leonardo Pellizza at CEA/Saclay  
```
L.J. Pellizza (CEA Saclay, France & IAFE, Argentina), P.-A. Duc (CEA Saclay, France), E. Le Floc'h (Steward Obs., USA), & I.F. Mirabel (ESO), on behalf of the MISTICI collaboration.
We imaged the field of GRB 050326 (Markwardt et al. 2005, GCN 3143) on June 5, 2005. Ks (42 x 60 seconds) frames were obtained with ISAAC at VLT. In the combined frame we detect two objects within the revised XRT error circle (Moretti et al. 2006, A&A, 448, L9). These objects are barely above our 3-sigma limiting magnitude Ks_lim ~ 21. Their positions are RA(J2000) = 00:27:49.7, DEC(J2000) = -71:22:12.6 (object 1) and RA(J2000) = 00:27:49.5, DEC(J2000) = -71:22:12.3 (object 2) (0.5 arcsec error). Both astrometry and photometry were calibrated against 2MASS stars.

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