- GCN/BACODINE POSITION NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Thu 21 Jul 05 04:31:17 UT
NOTICE_TYPE: Swift-BAT GRB Position
TRIGGER_NUM: 146970, Seg_Num: 0
GRB_RA: 253.445d {+16h 53m 47s} (J2000),
253.532d {+16h 54m 08s} (current),
252.661d {+16h 50m 39s} (1950)
GRB_DEC: -28.390d {-28d 23' 22"} (J2000),
-28.398d {-28d 23' 53"} (current),
-28.308d {-28d 18' 29"} (1950)
GRB_ERROR: 4.00 [arcmin radius, statistical only]
GRB_INTEN: 21583 [cnts] Image_Peak=195 [image_cnts]
TRIGGER_DUR: 5.504 [sec]
TRIGGER_INDEX: 489 E_range: 50-350 keV
BKG_INTEN: 181877 [cnts]
BKG_TIME: 16088.00 SOD {04:28:08.00} UT
BKG_DUR: 48 [sec]
GRB_DATE: 13572 TJD; 202 DOY; 05/07/21
GRB_TIME: 16154.28 SOD {04:29:14.28} UT
GRB_PHI: 91.37 [deg]
GRB_THETA: 39.08 [deg]
SOLN_STATUS: 0x83
RATE_SIGNIF: 15.09 [sigma]
IMAGE_SIGNIF: 6.22 [sigma]
MERIT_PARAMS: +1 +0 +0 +2 +3 +4 +0 +1 +72 +1
SUN_POSTN: 120.64d {+08h 02m 34s} +20.45d {+20d 27' 18"}
SUN_DIST: 136.65 [deg]
MOON_POSTN: 297.43d {+19h 49m 44s} -26.06d {-26d 03' 47"}
MOON_DIST: 38.89 [deg]
MOON_ILLUM: 100 [%]
GAL_COORDS: 353.95, 9.66 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 255.41, -5.79 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: SWIFT-BAT GRB Coordinates.
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: Since the IMAGE_SIGNIF is less than 7 sigma, this is a questionable detection.
- red DSS finding chart
ps-file
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Thu 21 Jul 05 04:34:25 UT
NOTICE_TYPE: Swift-BAT GRB Lightcurve
TRIGGER_NUM: 146970, Seg_Num: 0
GRB_RA: 253.445d {+16h 53m 47s} (J2000),
253.532d {+16h 54m 08s} (current),
252.661d {+16h 50m 39s} (1950)
GRB_DEC: -28.390d {-28d 23' 22"} (J2000),
-28.398d {-28d 23' 53"} (current),
-28.308d {-28d 18' 29"} (1950)
GRB_DATE: 13572 TJD; 202 DOY; 05/07/21
GRB_TIME: 16154.28 SOD {04:29:14.28} UT
TRIGGER_INDEX: 489
GRB_PHI: 91.37 [deg]
GRB_THETA: 39.08 [deg]
DELTA_TIME: 65504.00 [sec]
LC_URL: sw00146970000msb.lc
SUN_POSTN: 120.64d {+08h 02m 34s} +20.45d {+20d 27' 18"}
SUN_DIST: 136.65 [deg]
MOON_POSTN: 297.43d {+19h 49m 44s} -26.06d {-26d 03' 47"}
MOON_DIST: 38.89 [deg]
MOON_ILLUM: 100 [%]
GAL_COORDS: 353.95, 9.66 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 255.41, -5.79 [deg] ecliptic lon,lat of the pointing direction
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: Since the IMAGE_SIGNIF is less than 7 sigma, this is a questionable detection.
- GCN notice #3654
GRB050721A: Swift-BAT detection of a weak burst
L.A. Antonelli (INAF/OAR), K. Page (U. Leicester), D. Morris (PSU), P.
Romano (INAF/OAB), N. Gehrels (GSFC), P. Roming (PSU), P. Schady
(MSSL), G. Tagliaferri (INAF/OAB) S. Barthelmy (GSFC), H. Krimm
(GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), on behalf of
the Swift team:
At 04:29:14.28 UT, Swift-BAT triggered and located GRB050721
(trigger=146970). The spacecraft slewed immediately. The BAT on-board
calculated location is RA, Dec 253.445d,-28.390d {+16h 53m 47s,-28d 23'
22"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment,
stat+sys). The BAT light curve shows a peak with a total duration of
~10 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~5
seconds after the trigger.
The XRT started the observation at 04:32:20 UT with XRT in automatic
state, 186 sec after the BAT Trigger. An uncatalogued X-ray source was
detected at the following position RA, Dec 16h 53m 44.7s, -28d 22'
53''.3 with an uncertainty of about 6 arcsec (90% containment). This is
42 arcsec from the BAT position reported above.
Based on the UVOT finding chart there is no new source at the XRT
position.
- GCN notice #3655
K. Torii (Osaka U.) reports:
"The error region of the Swift GRB 050721a (Antonelli et al. GCN
3654) was imaged with the 0.3 m telescope in the New Mexico Skies
observatory. The observation started at 2005 July 21, 04:35:23 UT
(369 s after the trigger) and several 120 s integrations in I band
were obtained.
We identify a bright (I~15 mag) fading object whose position is
consistent with the XRT afterglow candidate reported in GCN
3654. However, this source does not seem to be spatially resolved with
a nearby 2MASS star in our frames. Further observations and analyses
are in progress."
- GCN notice #3657
S. Covino, P. D'Avanzo (INAF/OABr), S. Bagnulo, T. Szeifert (ESO), D.
Malesani (SISSA), G. Tagliaferri (INAF/OABr), G. Chincarini (Univ.
Milano-Bicocca), S. Piranomonte, L.A. Antonelli, and L. Stella
(INAF/OAR), on behalf of the MISTICI collaboration, report:
We observed the field of GRB 050721A (Antonelli et al., GCN 3654) with
the ESO-VLT UT2. Observations were carried out with the FORS1 instrument
in the R filter, starting on 2005 Jul 21, 4:54 UT (~25 minutes after the
GRB) and are still in progress.
Inside the XRT error box, we find a fiding source at the approximate
coordinates:
alpha = 16:53:44.53
delta = -28:22:51.8
with an error of ~1".
This lies 1.1" E, 0.7" N of the USNO star U0600_22125777, and is likely
the same source reported by Torii (GCN 3655).
This rapid response by an 8m-class telescope was possibile thanks to the
special Rapid Response Mode provided by ESO.
This message can be cited.
- GCN notice #3658
P. D'Avanzo, S. Covino, (INAF/OABr), D. Malesani (SISSA), S. Bagnulo, T.
Szeifert (ESO), G. Tagliaferri (INAF/OABr), G. Chincarini (Univ. Milano-
Bicocca), S. Piranomonte, L.A. Antonelli, and L. Stella (INAF/OAR), on
behalf of the MISTICI collaboration, report:
We performed a preliminary analysis on our R-band images (Covino et al.,
GCN 3657) of the field of GRB050721 (Antonelli et al., GCN 3654).
The afterglow indicated by Torii (GCN 3655) and confirmed by Covino et
al. (GCN 3657) faded by ~ 0.9 mag in the R band between July 21.204 UT
and July 21.226 UT (25 and 56 minutes after the GRB respectively). This
implies a decay index of ~ 1.
At our last epoch, the afterglow magnitude was R ~ 18.6, with reference
to USNO star UO600_22128314 assumed to be R = 17.4
This message can be cited.
- GCN notice #3659
P. Romano (INAF-OAB), L.A. Antonelli (INAF-OAR), G. Chincarini, A.
Moretti, G. Tagliaferri (INAF-OAB), K. Page (U. Leicester), F. Marshall
(GSFC), P. Boyd (GSFC-UMBC) on behalf of the Swift-XRT team:
We have analyzed the Swift XRT data from the first orbit observation of
GRB 050721A (Antonelli et al., GCN 3654). The new refined coordinates are:
RA(J2000) = 16h 53m 44.9s Dec(J2000) = -28 22 51.7
This position is 41 arcseconds from the BAT position given in GCN 3654.
We estimate an uncertainty of 6 arcseconds radius (90% containment).
A preliminary spectral fit (simple absorbed power-law) to the combined
PC and WT data yields a photon index of 1.7+/-0.1 in the [0.5-10] keV
band. The derived NH is 3.16E21 cm^-2, which is higher than the Galactic
value (1.57E21 cm^-2; Dickey & Lockman 1990). The average (194-323
seconds from trigger for WT and 324-463 seconds from trigger for PC)
estimated unabsorbed 0.5-10 keV flux is then 3.5E-10 ergs/s/cm^2.
The light curves in Windowed Timing (WT) and Photon Counting (PC) mode
start 194 and 324 seconds from the BAT trigger (T0), and they show a
fading afterglow with a preliminary decay slope -1.99+/-0.07 (first
orbit only). The unabsorbed 0.5-10.0 keV flux at 1 hour after the burst
is estimated to be 5E-12 ergs/s/cm^2.
- GCN notice #3661
E. Fenimore (LANL), L. Barbier (GSFC), S. Barthelmy (GSFC),
J. Cummings (GSFC/NRC), N. Gehrels (GSFC), D. Hullinger (UMD),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
T. McMahon (Langston U), T. Mitani (ISAS), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS),
M. Suzuki (Saitama), J. Tueller (GSFC), N. White (GSFC),
on behalf of the Swift/BAT team:
At 04:29:14.28 UT Swift-BAT detected GRB 050721 (trigger=146970)
(GCN Circ 3654, A. Antonelli et al.). This burst has been called
GRB 050721A in some circulars, although it is so far the only bona fide
burst of the day. The refined BAT ground position is (RA,Dec) =
253.452, -28.386 {16h 53m 48.5s, -28d 23' 10"} (J2000) +- 3 arcmin
(radius, 90% containment, stat+sys). The partial coding was 13%.
The masked-weighted light curve shows a FRED-like structure with a
single large peak starting to rise at T-5 seconds, peaking at T+3.7 seconds
and decaying back to background levels by T+50 seconds. The peak
is visible in the 15-100 keV energy band, but not at higher energies.
The calculated T90 (15-350 keV) is 39 +- 2 sec (estimated error
including systematics).
The power-law photon index of the time-averaged spectrum is 1.81 +- 0.08.
The fluence in the 15-350 keV band is (5.05 +- 0.25) x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+3.7 sec in the 15-350
band is (3.4 +- 0.8) ph/cm2/sec. All the quoted errors are at the 90%
confidence level.
- GCN notice #3662
V. Testa, L.A. Antonelli (INAF/OAR), D. Malesani (SISSA), S. Covino, P.
D'Avanzo, G. Tagliaferri (INAF/OABr), G. Chincarini (Univ.
Milano-Bicocca), G.L. Israel, S. Piranomonte, L. Stella (INAF/OAR),
report on behalf of the MISTICI collaboration:
We analyzed the full dataset of the early light curve of the afterglow
of GRB 050721 (Antonelli et al., GCN 3654; Torii, GCN 3655; Covino et
al., GCN 3657), obtained with the ESO VLT in rapid response mode.
The observation, performed in the R band, started 25 min after the GRB
and lasted for 107 minutes (till the object set). It was composed by
several short (30 s), repeated exposures. The light curve is well
described by a single power law, with decay index 1.20 +- 0.01. The
decay is smooth, without any significant rebrightening or deep.
We acknowledge the excellent support provided by the ESO staff in
performing the observations.
This message can be cited.
- astro-ph/0603730 from 27 Mar 2006
Antonelli: The multiwavelength afterglow of GRB 050721: a puzzling rebrightening seen in the optical but not in the X-ray
Context. GRB050721 was detected by Swift and promptly followed-up, in the
X-ray by Swift itself and, in the optical band, by the VLT operated, for the
first time, in rapid response mode. A multiwavelength monitoring campaign was
performed in order to study its afterglow behavior. Aims. We present the
analysis of the early and late afterglow emission in both the X-ray and optical
bands, as observed by Swift, a robotic telescope, and the VLT. We compare early
observations with late afterglow observations obtained with Swift and the VLT
in different bands in order to constrain the density of the medium in which the
fireball is expanding. Methods. We have analyzed both the X-ray and the optical
light curves and compared the spectral energy distribution of the afterglow at
two different epochs. Results. We observed an intense rebrightening in the
optical band at about one day after the burst which was not seen in the X-ray
band. This is the first observation of a GRB afterglow in which a rebrightening
is observed in the optical but not in the X-ray band. The lack of detection in
X-ray of such a strong rebrightening at lower energies can be described with a
variable external density profile. In such a scenario, the combined X-ray and
optical observations allow us to derive the matter density at 10^15 cm from the
burst. This is about a factor of 10 higher than in the inner region.