GRB 050922C
GCN Circular 4095
Subject
Photometric calibration of Swift/UVOT and Re-analysis of Swift/UVOT GRB 050922C data
Date
2005-10-14T19:23:02Z (20 years ago)
From
Weidong Li at UC Berkeley KAIT/LOSS <weidong@astron.berkeley.edu>
W. Li, S. Jha, A. V. Filippenko, J. S. Bloom, D. Pooley, R. J. Foley,
and D. A. Perley (University of California, Berkeley) report:
We would like to alert the community to the photometric calibration
of Swift/UVOT, for the U, B, and V filters, in an accepted paper
scheduled to be published in PASP in Jan. 2006 (available as
astro-ph/0505504, and significantly updated from its original
version). A simple, yet detailed, step-by-step recipe for
photometry is provided in Section 3.6 of the paper.
In particular, we have determined optimal aperture and sky regions,
and measured precise (+/- 0.01 mag) photometric zeropoints for the U,
B, and V filters, based on hundreds of observations of Landolt and
secondary standard stars. We also introduce a theoretically
motivated single parameter (m_infinity) to correct for coincidence
loss; this parameter is determined for all three filters to +/- 0.02 mag.
With these calibration results, we have re-analyzed the Swift/UVOT
UBV data on GRB 050922C, tabulated below. The preliminary analysis
by Hunsberger et al. (GCN 4041), based on the preliminary in-orbit
zeropoints, is listed for comparison whenever possible:
Filter Tmid(s) Exp(s) Mag Mag(err) GCN 4041
V 160.5 99.8 14.68 +- 0.03 14.60 +- 0.10
V 289.9 9.8 15.29 +- 0.12
V 374.5 9.8 15.46 +- 0.13 15.49 +- 0.17
V 458.9 9.8 16.00 +- 0.16
V 543.5 9.8 15.94 +- 0.16 15.99 +- 0.21
V 627.9 9.8 15.89 +- 0.15
V 712.5 9.8 16.04 +- 0.17 16.01 +- 0.21
V 4543.5 899.8 17.68 +- 0.04 17.62 +- 0.11
V 15962.5 899.8 18.99 +- 0.10 18.89 +- 0.21
V 28443.5 899.8 20.26 +- 0.24 >19.95 (3sigma upper limit)
V 40821.5 721.3 20.09 +- 0.22
V 52450.0 805.9 20.82 +- 0.38
V 64023.0 806.7 20.47 +- 0.29
B 261.5 9.8 15.88 +- 0.09 15.88 +- 0.13
B 345.5 9.8 16.02 +- 0.10
B 430.5 9.8 16.23 +- 0.10 16.36 +- 0.15
B 514.5 9.8 16.31 +- 0.11
B 598.5 9.8 16.46 +- 0.12 16.45 +- 0.16
B 683.5 9.8 16.64 +- 0.13
B 767.0 8.4 16.72 +- 0.14 16.91 +- 0.20
B 11133.5 899.8 19.15 +- 0.05 19.12 +- 0.11
B 22648.5 899.8 20.20 +- 0.10 20.13 +- 0.21
B 39108.5 897.3 21.14 +- 0.25 20.70 +- 0.38
B 50681.5 899.8 21.24 +- 0.26 20.74 +- 0.39
B 62254.5 899.8 20.81 +- 0.20
U 246.5 9.8 15.34 +- 0.10 15.09 +- 0.19
U 331.5 9.8 15.29 +- 0.09
U 416.5 9.7 15.80 +- 0.12 15.69 +- 0.20
U 500.5 9.8 15.97 +- 0.13
U 584.5 9.8 15.92 +- 0.12 15.84 +- 0.21
U 669.5 9.8 15.94 +- 0.12
U 753.5 9.7 15.99 +- 0.13 16.00 +- 0.21
U 10226.5 899.8 18.55 +- 0.05 18.58 +- 0.18
U 21749.0 900.0 19.48 +- 0.08 19.13 +- 0.20
U 34939.5 507.6 20.17 +- 0.17 19.88 +- 0.31
U 46660.0 814.1 20.38 +- 0.15 19.89 +- 0.26
U 58236.5 807.0 20.78 +- 0.20
U 69598.0 348.5 20.63 +- 0.27
Note the significantly improved photometric precision, especially for
the long-exposure observations. Our re-analyzed UVOT photometry for
GRB 050922C confirms the break in the light curve reported by Fynbo et
al. (GCN 4040), Covino et al. (GCN 4046), and Andreev et al. (GCN 4048).
A single power-law fit to the UVOT UBV data yields a decline index of
-0.87, but the fit is relatively poor (reduced chi^2 about 3.0).
Using a broken power-law fit (with parameters as in Li et al. 2003, PASP,
115, 844), we find t(break) = 2.7 +- 0.7 hours, alpha1 = -0.82 +- 0.06,
alpha2 = -1.16 +- 0.14, and s = 30.5 +- 5.0, with a reduced chi^2 = 1.21.
This fit can be seen at
http://astron.berkeley.edu/~weidong/grb050922c.lc1.gif .
If we instead force the break to be smoother (s = 1; e.g., Stanek et
al., 1999, ApJ, 522, L39), we derive t(break) = 4.3 +- 0.6 h, alpha1 =
-0.71 +- 0.08, and alpha2 = -1.37 +- 0.16, with a reduced chi^2 =
1.46. This fit is shown at
http://astron.berkeley.edu/~weidong/grb050922c.lc2.gif .
In contrast, the UBV photometry reported in GCN 4041 can accommodate a
single power-law fit with a decline index of -0.84 (reduced chi^2 = 0.58).
We urge the community to make use of the calibration and photometric
recipe in astro-ph/0505504 for Swfit/UVOT U, B, and V data until even
better calibration results are available.
GCN Circular 4048
Subject
GRB050922C: optical observation
Date
2005-09-29T13:12:57Z (20 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
M. Andreev (Institute of Astronomy), A. Pozanenko, V. Loznikov (IKI) and
V.Rumyantsev (CrAO), on behalf of larger GRB follow up collaboration report:
We observed OT (GCNs 4011, 4012, Rykoff et al.) of GRB050922C (GCN4013
Norris et al.) in R-band with 60 cm telescope of Peak Terskol observatory
starting Sep. 22 (UT) 20:08:45 (Andreev et al. GCN4016). 61 images of 60 s
exposure were taken between (UT) 20:08:45 and 21:18:20. The photometry
calibration was done against USNO-A2.0.
Light curve of OT may be approximated with two power laws: index alpha
= -0.67 (0.02) between T0+ 0.00862d and T0+ 0.04338d, alpha = -1.24 (0.15)
starting on T0+ 0.04338d with a break at ~T0+1h.
Preliminary light curve can be found in http://grb.rssi.ru/GRB050922c/
The message may be cited.
GCN Circular 4046
Subject
GRB 050922C: further VLT observations
Date
2005-09-28T17:17:39Z (20 years ago)
From
Stefano Covino at Brera Astronomical Observatory <covino@merate.mi.astro.it>
S. Covino, S. Piranomonte, D. Fugazza, F. Fiore, D. Malesani, G.
Tagliaferri, G. Chincarini, L. Stella on behalf of the MISTICI
collaboration report:
We are following the decay of the optical afterglow of GRB 050922C
(Norris et al., GCN 4013) with the ESO VLT+FORS1.
Multi-band BVR photometry was carried out on September 24 at 00:10 UT,
about 1.2 days after the high-energy event.
A preliminary calibration, based on Landolt standard stars, have been
performed and the OT magnitude in the R band was:
R = 21.57 +/- 0.05
confirming the break in the light curve reported by Fynbo et al. (GCN
4040).
This message can be quoted.
GCN Circular 4044
Subject
GRB050922C: UVES/VLT high resolution spectroscopy
Date
2005-09-28T16:55:22Z (20 years ago)
From
Silvia Piranomonte at OAR <piranomonte@mporzio.astro.it>
V. D'Elia, S. Piranomonte, F. Fiore (INAF-OAR), S. Covino (INAF/OABr),
L.A. Antonelli, G.L. Israel,
L. Stella, L. Sbordone (INAF-OAR), D. Fugazza, G. Tagliaferri
(INAF/OABr), D. Malesani (SISSA), G. Chincarini (Univ. Milano-Bicocca),
on behalf of the MISTICI collaboration, report:
"Starting on September 22, 2005 23:28:59 UT (~3.5 hours after the GRB
trigger) we have obtained high resolution spectra (R~40,000, 7.5 km/s
in the observer frame) of the optical afterglow of GRB050922C (Krimm et
al., GCN 4020, Rykoff et al. GCN 4011) using UVES at VLT/Kueyen. The
observations consisted of 2 exposures for a total of 6000 seconds net
integration covering the full spectral range 3100-10000 Angstrom, under
good seeing conditions. At the time of the observations the afterglow
magnitude was R~19-19.5. The resulting continuum signal to noise per
resolution element spans from 10 to 20 in the 4000-7000 Angstrom
range. The afterglow is clearly detected down to ~3300 Angstrom.
A preliminary analysis of the data shows a very rich spectrum. We
find four main systems at z=2.199, 2.077, 2.008 and 1.9985 (the first
2 systems have been previously reported by Jakobsson et al., GCN
4029, and by Piranomonte et al., GCN 4032). The latter two systems are
shifted by only 950 km/s (rest frame). The strongest absorption lines
of the four systems are the following.
z=2.199: Lyalpha, Lybeta, OVI1032,1038, SiII1190,1193, SiII1260,
FeII1260, SiII*1264, SiII*1266, OI1302, SiII1304, OI*1304, OI*1306,
SiII*1309, CII1334, CII*1335, SiIV1393,1402, SiII*1533, CIV1548,1550,
FeII1608, FeII*1621, AlII1670, AlIII1862,1854,
FeII2344,2374,2382,2586,2600, MgII2796,2803
z=2.077: Lyalpha, OI_1302, SiII1304, CII1334, SiIV1393,1402,
CIV1548,1550, FeII1608, AlII1670, AlIII1854,
FeII2344,2374,2382,2586,2600
z=2.008 Lyalpha, CIV1548,1550, SiIV1402,1393
z=1.9885 Lyalpha, CIV1548,1550, SiIV1402,1393
Therefore, fine-structure lines of CII*, SiII*, OI*, FeII*, witnessing
a high density environment, are detected only for the highest redshift
systems, likely associated with the GRB host galaxy.
A full analysis is underway.
We thank Paul Vreeswijk and Poshak Gandhi of the ESO staff for the
excellent support in performing these observations in service mode."
This message can be cited.
GCN Circular 4041
Subject
GRB050922C - Swift UVOT preliminary analysis
Date
2005-09-26T21:13:03Z (20 years ago)
From
Caryl Gronwall at PSU/Swift-UVOT <caryl@astro.psu.edu>
S. D. Hunsberger (PSU), F. Marshall (GSFC), S. T. Holland (GSFC),
P. Brown (PSU), A. Morgan (PSU), P. Roming (PSU), and
A. Cucchiara (PSU) on behalf of the Swift/UVOT teams
The UVOT began observing GRB050922C at 19:57:41UT, 111 seconds
after the BAT trigger (Norris et al., GCN 4013). A fading
optical counterpart is detected at 21:09:33.0 -08:45:30.1. The
afterglow is apparent in the UBV filters and there is a marginal
detection in UVW1 which is likely due to the redward edge of the
filter response overlapping the U bandpass. The UVOT magnitudes
listed below are not corrected for extinction. Tmid is the time
since trigger of the midpoint of the exposure(s).
Filter Tmid(s) Exp(s) Mag
V 115.5 99.8 14.60 +- 0.10
V 374.5 9.8 15.49 +- 0.17
V 543.5 9.8 15.99 +- 0.21
V 712.5 9.8 16.01 +- 0.21
V 4543.5 899.8 17.62 +- 0.11
V 15962.5 899.8 18.89 +- 0.21
V 28443.5 899.8 19.95 is 3sigma upper limit
B 261.5 9.8 15.88 +- 0.13
B 430.5 9.8 16.36 +- 0.15
B 598.5 9.8 16.45 +- 0.16
B 767.0 8.4 16.91 +- 0.20
B 11133.5 899.8 19.12 +- 0.11
B 22648.5 899.8 20.13 +- 0.21
B 39108.5 897.3 20.70 +- 0.38
B 50681.5 899.8 20.74 +- 0.39
U 246.5 9.8 15.09 +- 0.19
U 416.5 9.7 15.69 +- 0.20
U 584.5 9.8 15.84 +- 0.21
U 753.5 9.7 16.00 +- 0.21
U 10226.5 899.8 18.58 +- 0.18
U 21749.0 900.0 19.13 +- 0.20
U 34939.5 507.6 19.88 +- 0.31
U 46660.0 814.1 19.89 +- 0.26
UVW1 487.0 68.6 17.70 +- 0.29 (co-added 10s exposures)
UVW1 6233.5 651.1 19.96 +- 0.41
UVW1 17730.0 806.0 20.18 is 3sigma upper limit
UVM2 473.0 68.5 18.86 is 3sigma upper limit (co-added)
UVM2 5450.5 899.8 20.48 is 3sigma upper limit
UVW2 487.5 58.8 19.30 is 3sigma upper limit (co-added)
UVW2 11969.5 753.2 20.62 is 3sigma upper limit
Magnitudes are based on preliminary zeropoints, measured in orbit, and
may require further refinement.
GCN Circular 4040
Subject
GRB 050922C: break in the lightcurve
Date
2005-09-26T20:13:40Z (20 years ago)
Edited On
2024-11-07T20:01:27Z (a year ago)
From
Brian Lindgren Jensen at U.of Copenhagen <brian_j@astro.ku.dk>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>
Johan P. U. Fynbo, Brian L. Jensen, Páll Jakobsson,
Jens Hjorth, Jesper Sollerman, José María Castro Cerón
(DARK, NBI), Karianne Holhjem (NOT, La Palma), Ricardo Salinas
(Universidad de Concepción, Chile) report:
We have obtained further imaging of the afterglow of GRB 050922C
(GCN 4011, 4012, 4013) using the ALFOSC at the Nordic Optical
Telescope on La Palma and DFOSC at the Danish 1.5m telescope at La
Silla, Chile. We find that the early decay slope of about 1 (GCN 4012)
extends to less than a day post burst, after which the decay slope
steepens to about alpha=1.7+-0.3. Further observations are planned.
A preliminary lightcurve can be seen at:
http://www.astro.ku.dk/~brian_j/grb/grb050922.830/
GCN Circular 4032
Subject
GRB050922C: TNG spectroscopic observations
Date
2005-09-23T17:37:41Z (20 years ago)
From
Silvia Piranomonte at OAR <piranomonte@mporzio.astro.it>
S. Piranomonte (INAF/OAR), A. Magazzu (TNG), G. Mainella (TNG),
F. Fiore (INAF/OAR), S. Covino (INAF/OABr), D. Fugazza (INAF/OABr),
A. Antonelli (INAF/OAR), G. Israel (INAF/OAR), G. Chincarini (Univ. Milano-Bicocca),
D. Malesani (SISSA), , F. Mannucci (INAF/Arcetri), G. Tagliaferri (INAF/OABr),
and L. Stella (INAF/OAR) on behalf of the CIBO collaboration, report:
Starting on September 22 21:17:35 UT (about 82 min after the GRB
trigger) we have obtained low resolution spectra
of the optical afterglow of GRB050922C (Rykoff et al.
GCN#4012). The observations consisted of 5 exposures for 300 sec each with
DOLORES@TNG, using grism LR-B, with a 1" slit. This set-up provides
a resolution of about 5 angstrom.
At the time of the observations the afterglow magnitude varied between
R~16.7 and R=17.7.
A preliminary analysis of the data confirms a very rich spectrum
(see Jakobsson et al. GCN#4017, GCN#4029).
We detect strong Lyalpha, SiII1304, CII1334, SiIV1393, SiII1526,
CIV1548,1550, AlII1670, SiII1808 absorption lines at z=2.198+/-0.001,
We also confirm the strong Lyalpha absorption at z=2.07.
A full analysis is underway.
We thank the TNG staff for the excellent support in performing these
observations.
This message can be quoted.
GCN Circular 4030
Subject
Konus-Wind observation of GRB 050922C
Date
2005-09-23T16:05:24Z (20 years ago)
From
Valentin Pal'shin at Ioffe Inst <val@mail.ioffe.ru>
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and
T. Cline on behalf of the Konus-Wind team report:
The GRB 050922C (Swift-BAT trigger #156467;
Norris et al., GCN 4013, Krimm et al., GCN 4020)
triggered Konus-Wind at T0=71754.480 s UT (19:55:54.480).
As observed by Konus-Wind it had a duration of ~5 s,
fluence (7.3 +/- 0.5)10-6 erg/cm2,
peak flux on 128-ms time scale (4.5 +/- 0.7)10-6 erg/cm2/s
(both in the 20 keV - 2 MeV energy range).
The time-integrated spectrum of the GRB
(from T0 to T0+8.448 s) is well fitted (in the 20 keV - 2 MeV range)
by a power law model with photon index 1.55 +/- 0.07.
The spectrum does not demonstrate an exponential cutoff
with E0 ~100 keV reported by HETE Fregate (Crew et al., GCN 4021).
Assuming z = 2.17 (Jakobsson et al., GCN 4017) and a standard cosmology
model with H_0 = 70 km/s/Mpc, Omega_M = 0.3, Omega_\Lambda = 0.7,
the isotropic energy release is E_iso ~8.1x10^52 erg,
the maximum luminosity is (L_iso)_max ~1.6x10^53 erg/s.
GCN Circular 4029
Subject
GRB 050922C: Refined redshift
Date
2005-09-23T15:39:42Z (20 years ago)
Edited On
2024-11-07T19:52:34Z (a year ago)
From
Pall Jakobsson at Niels Bohr Inst <pallja@astro.ku.dk>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>
Páll Jakobsson, Johan P. U. Fynbo, (DARK, NBI), Danka Paraficz,
John Telting (NOT, La Palma), Brian L. Jensen, Jens Hjorth and
José María Castro Cerón (DARK, NBI) report:
Using new wavelength calibration files, we have refined the
GRB 050922C redshift obtained at the NOT (GCN 4017). Based on the
detection of Lyman-alpha, OI+SiII, CII, SiIV, FeII, AlII, SiII* and
SiII in absorption, we measure a redshift of z = 2.198+-0.001.
There is additional strong absorption, possibly corresponding to
Lyman-alpha at z = 2.07.
GCN Circular 4026
Subject
GRB050922C: observation at MonteBoo
Date
2005-09-23T12:38:40Z (20 years ago)
From
Martin Jelinek at Inst.Astrophys.Andalucia,Granada <mates@asu.cas.cz>
T. Henych, M. Kocka, F. Hroch (MU Brno, Czech Republic),
Martin Jelinek (IAA Granada, Spain) and
Rene Hudec (ASU AV CR Ondrejov, Czech Republic)
report:
We have observed the optical transient of GRB050922C reported
by Rykoff et al. (GCN 4011) for 1.2h with the mean time 0.100d
after the GRB trigger (Norris et al., GCN 4013) with the 60cm
telescope at MonteBoo Observatory equipped with an ST8 CCD. We
have found the OT at roughly R=18 decaying with an index
\alpha = -0.5 .
This message may be cited.
GCN Circular 4023
Subject
GRB050922C: Optical Observations
Date
2005-09-23T04:43:10Z (20 years ago)
From
Aaron Price at AAVSO <aaronp@aavso.org>
D. T. Durig (Cordell-Lorenz Observatory - University of the South) and A.
Price (AAVSO) report on behalf of the AAVSO International High Energy
network on optical observations of GRB050922C.
After glow reported by Rykoff et al (GCN #4011) was visible in 2 hours of
exposures. The first three measurements are below and a link to the rest
is in the full report at the bottom of the e-mail. Uncertainty is
estimated at +/-0.2 mag.
09 23.03833 19.1 Rc
09 23.07725 19.5 Rc
09 23.10989 20.1 Rc
The AAVSO would like to thank the Curry Foundation and NASA for their
support of the AAVSO International High Energy Network.
Name: Dr. Douglas T. Durig
email: ddurig@sewanee.edu
Observer: D. T. Durig, K. T. Crockett, L. R. Johnson
Site: Cordell-Lorenz Observatory
Location: Sewanee, TN, USA
LatitudeLongitude: 35 12 N 85 55 W
Elevation: 600 m
Scope: SCT 0.30 m
ScopeFocalRatio: f/5.9 1770 mm
CCDVendor: SBIG ST-8E
CCDDetector: KAF-1600E
CCDSize: 1530x1020 binned 3x3 for 510x340
CCDPixelScale: 3.14 arc sec per pixel
CCDFOV: 26.7x17.8 full, 13.3x8.9 cropped submitted
Object: GRB050922C
ObsDate: 2005 09 23
ObsMidPointTime: 01:51:14 UT
TimePerFrame: 300 sec
NumberOfFrames: best 24 out of 30
Filters: CR
Processing: dark,flat, register,co-add, 1/2 frame crop
Seeing: 5-6 arc sec
LimitingMag: ~21.5 ???
Sky: clear, but very gusty winds
afterglowmag: 19 fading to 20 over two hours time
afterglowerr: 0.2 mag
compstars: 94 UCAC, 188 B1.0 subframe
Report: Full frame covers entire error box. After glow reported by Rykoff et al (GCN 4011) was visible in single 300 sec exposure but 6 frames were added to improved S/N for measurements. We measure a position of
21 09 33.10 -08 45 30.2
First three photometric measurements shown below.
We have posted our first 2 hours of exposure at http://arthur.sewanee.edu/obsv/view.php
comments: 09 23.03833 21 09 33.10 -08 45 30.2 19.1 R
09 23.07725 21 09 33.12 -08 45 30.4 19.5 R
09 23.10989 21 09 33.12 -08 45 30.7 20.1 R
A FITS image has been uploaded to ftp://ftp.aavso.org/grb/Dr.DouglasT.Durig_GRB050922C_2453636.66853_.fits
GCN Circular 4022
Subject
GRB 050922C: Swift XRT refined analysis
Date
2005-09-23T02:57:43Z (20 years ago)
From
Jamie A. Kennea at PSU/Swift-XRT <kennea@astro.psu.edu>
J. A. Kennea, D. N. Burrows (PSU), M. Goad (U. Leicester), J. Norris and
N. Gehrels (GSFC) report on behalf of the Swift/XRT Team:
We report on detailed ground analysis of the first 2 orbits of data from
X-ray afterglow of GRB050922C (GCN 4013) utilizing downlinked Swift/XRT
data. We find a refined position for the XRT afterglow of:
RA(J2000): 21:09:33.3,
Dec(J2000): -8:45:27.5,
with an estimated uncertainty of 6 arcseconds radius (90% containment). We note
that this position is 4.6 arcseconds from the NOT optical afterglow position
reported in GCN 4015.
We have extracted a lightcurve of combined Window Timing and Photon
Counting mode data from the first two orbits of XRT observations, covering
6500ks of time. The lightcurve of the afterglow is well described by a
single powerlaw model with a slope of -1.14 +/- 0.02.
The spectrum of the afterglow is well fit (reduced Chi^2 = 0.94 with 44 dof) by
an absorbed power-law model with the following parameters:
N_H = (6.5 +/- 2.7) x 10^20 cm^-2
Photon Index = 1.89 +/- 0.16
The absorption seen here is consistant with the expected Galactic absorption of
5.75 x 10^20 cm^-2. Utilizing this spectral model, we estimate the flux of this
burst (corrected for absorption) to be:
BAT Trigger +1 hour: 1.5 x 10^-11 erg/s/cm^2 (0.5 - 10 keV)
BAT Trigger +1 day: 3.9 x 10^-13 erg/s/cm^2 (0.5 - 10 keV)
Note that the latter flux estimate assumes that the lightcurve does not
break.
Observations of this burst by Swift are on-going.
GCN Circular 4021
Subject
HETE Fregate observations of GRB 050922C
Date
2005-09-23T01:18:28Z (20 years ago)
From
Roland Vanderspek at MIT <roland@space.mit.edu>
HETE Fregate observations of GRB 050922C
G. Crew, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley, on
behalf of the HETE Science Team;
M. Arimoto, T. Donaghy, E. Fenimore, M. Galassi, C. Graziani,
J. Kotoku, M. Maetou, M. Matsuoka, Y. Nakagawa, T. Sakamoto, R. Sato,
Y. Shirasaki, M. Suzuki, T. Tamagawa, K. Tanaka, Y. Yamamoto,
and A. Yoshida, on behalf of the HETE WXM Team;
N. Butler, J. Doty, G. Prigozhin, R. Vanderspek, J. Villasenor,
J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga, R. Manchanda,
and G. Pizzichini, on behalf of the HETE Operations and HETE
Optical-SXC Teams;
M. Boer, J-F Olive, J-P Dezalay, and K. Hurley, on behalf of the HETE
FREGATE Team;
report:
The HETE Fregate instrument detected GRB 050922C (Swift trigger 156647;
Norris et al, GCN 4013). The flight instruments did not trigger because
they were processing another trigger (H3934) which occurred 204 seconds
earlier.
The burst was clearly detected in Fregate in the 7-30, 7-80, and 30-400
keV bands. The burst spectrum is best fit with a cutoff power law of
photon index 0.83 (-0.26/+0.23) and Epeak of 130.5 keV (-26.8/50.9). The
2-30 keV fluence is 5.4e-7 erg/cm2; the 30-400 keV fluence is 2.6e-6 erg/cm2.
The ratio of the 2-30 keV to 30-400 keV fluence is 0.2: thus, GRB 050922C
is a classical GRB.
Due to the hardness of the spectrum, we have not been able to determine
the high-energy slope (beta) of the Band function for this burst. The
determination of bolometric fluence is therefore subject to systematic
uncertainty. Assuming z=2.17 (Jakobbson et al., GCN 4017) and assuming
the above cutoff power-law applies in the source-frame energy range of
1-10000 keV, the lower bound on E_iso is E_iso=3.7E+52 erg. The upper
bound, obtained assuming beta=-2.0, is E_iso=7.0E+52 erg.
GCN Circular 4020
Subject
GRB 050922C: Swift-BAT refined analysis
Date
2005-09-23T00:37:09Z (20 years ago)
From
Takanori Sakamoto at NASA/GSFC <takanori@milkyway.gsfc.nasa.gov>
H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. Barthelmy (GSFC),
J. Cannizzo (GSFC-UMBC), L. Cominsky (Sonoma State U.),
J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (UMD), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS),
J. Tueller (GSFC) on behalf of the Swift-BAT team:
Using the data set from T-10 to T+60 sec from the recent telemetry
downlink, we report further analysis of Swift-BAT GRB 050922C
(trigger #156467) (Norris, et al., GCN 4013). The refined BAT ground position
is (RA,Dec) = 317.381, -8.762 {21:09:32, -8:45:43} [deg; J2000]
+- 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding
was 53%.
The light curve shows the intense broad peak starting from T-3 to T+3 with
at least two sub-peaks on top. T90 (15-350 keV) is (5 +- 1) sec
(estimated error including systematics).
The power law index of the time-averaged spectrum is 1.33 +- 0.06.
The fluence in the 15-150 keV band is (1.7 +- 0.1) x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-0.02 sec in the 15-150 keV
band is (7.5 +- 0.3) ph/cm2/sec. All the quoted errors are at the 90%
confidence level.
GCN Circular 4018
Subject
GRB050922C: optical observations
Date
2005-09-22T23:50:07Z (20 years ago)
From
Eran Ofek at Tel Aviv U. <eran@wise1.tau.ac.il>
E. O. Ofek, Y. M., Lipkin, J. Dann (Wise observatory, TAU) report:
We have observed the Swift error box of GRB050922C
(Norris et al. GCN 4013) using the Wise observatory 1m
telescope starting at 2005, Sep 22nd, 22:10:56 UTC.
We obtained a 210 sec unfiltered image (mid exposure
time 0.0950 days after the Swift-BAT trigger) in which
we detected the optical transient (OT) discovered by
Rykoff et al. (GCN 4011).
At that epoch, the OT magnitude was R~17.9, assuming
R-mag=14.24 for the bright star 37 arcsec at PA=210deg
from the OT.
GCN Circular 4017
Subject
GRB 050922C: Absorption redshift from the Nordic Optical Telescope
Date
2005-09-22T23:33:59Z (20 years ago)
From
Pall Jakobsson at Niels Bohr Inst <pallja@astro.ku.dk>
Pall Jakobsson, Johan P. U. Fynbo, (DARK, NBI), Danka Paraficz,
John Telting (NOT, La Palma), Brian L. Jensen, Jens Hjorth and
Jose Maria Castro Ceron (DARK, NBI) report:
Using ALFOSC on the Nordic Optical Telescope (NOT) we have obtained
spectra of the afterglow of GRB 050922C (GCN#4013 Norris et al.
[Swift], GCN#4012 Rykoff et al. [ROTSE-III], GCN#4015
Jakobsson et al. [NOT]) on 2005, Sep 22.9 UT.
We find several absorption features, including strong Lyman-alpha,
OI+SiII, CII, SiIV, CIV, AlII and AlIII, corresponding to a redshift
of z = 2.17+-0.03 (based on a preliminary wavelength calibration).
There is additional strong absorption, possibly corresponding to
Lyman-alpha at z = 2.05+-0.03.
GCN Circular 4016
Subject
GRB 050922C: optical obserations
Date
2005-09-22T22:49:02Z (20 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
M. Andreev, A. Pozanenko on behalf of larger GRB follow up collaboration
report:
We observed the GRB 050922C field (Swift trigger: 156467, GCN4013 Norris et
al.) in R-band with 60 cm telescope of Terskol observatory. We confirm the
new OT found in by ROTSE-IIId (GCNs 4011, 4012, Rykoff et al.) OT is fading
and
preliminary photometry of the OT against of USNO A2.0 of the first image
taken at (UT) 20:08:45 is R~16.
The observation is continuing.
GCN Circular 4015
Subject
GRB 050922C: NOT optical observations
Date
2005-09-22T22:16:59Z (20 years ago)
From
Pall Jakobsson at Niels Bohr Inst <pallja@astro.ku.dk>
Pall Jakobsson (DARK, NBI), Danka Paraficz, John Telting
(NOT, La Palma), Johan P. U. Fynbo, Brian L. Jensen,
Jens Hjorth and Jose Maria Castro Ceron (DARK, NBI) report:
Using ALFOSC on the 2.56-meter Nordic Optical Telescope,
we have obtained a 300 s R-band image of the GRB 050922C
field (Swift trigger: 156467, GCN#4013 (Norris et al.)).
Using a preliminary photometric zeropoint we estimate the
following magnitude for the afterglow:
R ~ 16.5 @ 1 hour post-burst.
The coordinates are:
(RA, Dec)(J2000.0) = (21:09:33.083, -08:45:30.2)
with a 0.2" error in each coordiante.
A finding chart of the field is available at:
http://www.astro.ku.dk/~brian_j/grb/grb050922.830/
GCN Circular 4013
Subject
GRB 050922C: Swift detection of a bright burst
Date
2005-09-22T21:05:45Z (20 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <jayc@milkyway.gsfc.nasa.gov>
J. Norris (GSFC), L. Barbier (GSFC), D. Burrows (PSU), A. Cucchiara (PSU),
J. Cummings (GSFC/NRC), N. Gehrels (GSFC), M. Goad (U. Leicester),
O. Godet (U. Leicester), S.T. Holland (GSFC/USRA), J. Kennea (PSU),
F. Marshall (GSFC), D. Palmer (LANL), T. Sakamoto (GSFC/NRC),
on behalf of the Swift team:
At 19:55:50 UT Swift-BAT triggered and located GRB 050922C (Trigger=156467)
and immediately slewed. The BAT on-board calculated position is RA,Dec=
317.391d, -8.772d {21h 09m 34s, -08d 46' 17"} (J2000) with an uncertainty
of 3 arcmin (radius, 90% containment, stat+sys). The TDRSS light curve
shows an intense GRB with a rising precursor starting at T-5 seconds,
followed by 5-second long main peak surmounted by three spikes. The third
and most intense spike has a maximum count rate at T+1 sec of 15,000
counts/sec (15-350 keV).
XRT began observing the field at 19:57:38 UT, 108 seconds after the BAT
trigger. XRT performed an onboard centroid and found a previously
uncataloged fading source in the field of view at the following coordinates:
RA(J2000): 21:09:33.4,
Dec(J2000): -8:45:30.5,
with an estimated uncertainty of 8 arcseconds radius (90% containment). This
position is 49 arcseconds from the BAT position and within 4.5 arcsec of the
optical transient reported by Rykoff et al. (GCN circ 4011 [mistitled]).
UVOT began observing at 111 sec after the trigger. The small UVOT TDRSS
image does not overlap the XRT error circle. However, the full-field UVOT
source list contains a bright, uncataloged source within the XRT error
circle. We estimate the V magnitude at 15.5 +- 0.5 uncorrected for
extinction. The V-band extinction in this field is A_V = 0.34 mag.
[GCN OPS NOTE(22sep05): Per author's request, the Subject-line
was changed from "050822" to "050922".]
GCN Circular 4012
Subject
GRB 050922C: ROTSE-IIId Refined Analysis
Date
2005-09-22T20:31:39Z (20 years ago)
From
Eli Rykoff at U of Michigan/ROTSE <erykoff@umich.edu>
E.S. Rykoff (U Mich), S.A. Yost (U Mich), W. Rujopakarn (U Mich), R.
Quimby (U Texas), D. A. Smith (Guilford), F. Yuan (U Mich) report
on behalf of the ROTSE collaboration:
ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe,
Turkey, responded to GRB 050922C (Swift trigger 156467). (Note that the
burst designation in GCN 4011 is incorrect).
We obtained 10 5-s images followed by 12 20-s images before
precipitation ended observations. The object reported in GCN 4011 fades
significantly from 172 s post-burst to 651 s post-burst as a simple
power-law with index -1.0. At 640 s post-burst the counterpart was at
16.0+/-0.1 mag (unfiltered) relative to the USNO A2.0 R-band magnitudes.
A finding chart can be found at:
http://www.rotse.net/grb_reports/050922C_btab.html
GCN Circular 4011
Subject
GRB 050922C: ROTSE-III Detection of Possible Counterpart
Date
2005-09-22T20:04:53Z (20 years ago)
From
Eli Rykoff at U of Michigan/ROTSE <erykoff@umich.edu>
E.S. Rykoff (U Mich), S.A. Yost (U Mich), W. Rujopakarn (U Mich) report
on behalf of the ROTSE collaboration:
ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe,
Turkey, responded to GRB 050922C (Swift trigger 156467). The first image
was at 19:58:42.8 UT, 172.4 s after the burst (6.8 s after the GCN
notice time). The unfiltered images are calibrated relative to USNO
A2.0. We detect a new object, not visible in the DSS (second epoch),
with coordinates:
21:09:33.1 -08:45:29.8 (J2000)
start UT mag mlim(of image)
----------------------------------
19:58:42.8 14.7 16.1
Continuing observations are in progress.
[GCN OPS NOTE(22sep05): Per author's request, the two instances
of 'A' were changed to 'C'.]