- GCN/BACODINE POSITION NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 16 Apr 05 11:04:57 UT
NOTICE_TYPE: Swift-BAT GRB Position
TRIGGER_NUM: 114753, Seg_Num: 0
GRB_RA: 188.478d {+12h 33m 55s} (J2000),
188.545d {+12h 34m 11s} (current),
187.853d {+12h 31m 25s} (1950)
GRB_DEC: +21.043d {+21d 02' 36"} (J2000),
+21.014d {+21d 00' 51"} (current),
+21.319d {+21d 19' 08"} (1950)
GRB_ERROR: 4.00 [arcmin radius, statistical only]
GRB_INTEN: 2897 [cnts] Peak=165 [cnts/sec]
TRIGGER_DUR: 0.512 [sec]
TRIGGER_INDEX: 68 E_range: 15-50 keV
BKG_INTEN: 35359 [cnts]
BKG_TIME: 39872.00 SOD {11:04:32.00} UT
BKG_DUR: 8 [sec]
GRB_DATE: 13476 TJD; 106 DOY; 05/04/16
GRB_TIME: 39884.48 SOD {11:04:44.48} UT
GRB_PHI: 79.12 [deg]
GRB_THETA: 36.27 [deg]
SOLN_STATUS: 0x3
RATE_SIGNIF: 19.26 [sigma]
IMAGE_SIGNIF: 11.00 [sigma]
MERIT_PARAMS: +1 +0 +0 +0 +1 +11 +0 +0 +81 +1
SUN_POSTN: 24.64d {+01h 38m 33s} +10.24d {+10d 14' 41"}
SUN_DIST: 144.97 [deg]
MOON_POSTN: 117.93d {+07h 51m 44s} +26.35d {+26d 21' 03"}
MOON_DIST: 64.10 [deg]
MOON_ILLUM: 49 [%]
GAL_COORDS: 268.70, 82.72 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 178.97, 22.59 [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.
- red DSS finding chart
ps-file
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 16 Apr 05 11:06:12 UT
NOTICE_TYPE: Swift-XRT Nack-Position
TRIGGER_NUM: 114753, Seg_Num: 0
POINT_RA: 188.479d {+12h 33m 55s} (J2000)
POINT_DEC: +21.053d {+21d 03' 10"} (J2000)
GRB_DATE: 13476 TJD; 106 DOY; 05/04/16
GRB_TIME: 39963.63 SOD {11:06:03.63} UT
COUNTS: 17 Min_needed= 20
STD_DEV: 0.00 Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER: 1 Max_iter_allowed= 4
ERROR_CODE: 1
COMMENTS: SWIFT-XRT Nack Position.
COMMENTS: No source found in the image.
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 16 Apr 05 11:08:45 UT
NOTICE_TYPE: Swift-BAT GRB Lightcurve
TRIGGER_NUM: 114753, Seg_Num: 0
GRB_RA: 188.478d {+12h 33m 55s} (J2000),
188.545d {+12h 34m 11s} (current),
187.853d {+12h 31m 25s} (1950)
GRB_DEC: +21.043d {+21d 02' 36"} (J2000),
+21.014d {+21d 00' 51"} (current),
+21.319d {+21d 19' 08"} (1950)
GRB_DATE: 13476 TJD; 106 DOY; 05/04/16
GRB_TIME: 39884.48 SOD {11:04:44.48} UT
TRIGGER_INDEX: 68
GRB_PHI: 79.12 [deg]
GRB_THETA: 36.27 [deg]
DELTA_TIME: 65460.00 [sec]
LC_URL: sw00114753000msb.lc
SUN_POSTN: 24.64d {+01h 38m 33s} +10.24d {+10d 14' 41"}
SUN_DIST: 144.97 [deg]
MOON_POSTN: 117.93d {+07h 51m 44s} +26.35d {+26d 21' 03"}
MOON_DIST: 64.10 [deg]
MOON_ILLUM: 49 [%]
GAL_COORDS: 268.70, 82.72 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 178.97, 22.59 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-BAT GRB Lightcurve.
COMMENTS: This does not match any source in the ground catalog.
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sat 16 Apr 05 11:10:18 UT
NOTICE_TYPE: Swift-XRT Lightcurve
TRIGGER_NUM: 114753, Seg_Num: 0
POINT_RA: 188.477d {+12h 33m 54s} (J2000)
POINT_DEC: +21.054d {+21d 03' 16"} (J2000)
LC_START_DATE: 13476 TJD; 106 DOY; 05/04/16
LC_START_TIME: 39966.31 SOD {11:06:06.31} UT
LC_STOP_DATE: 13476 TJD; 106 DOY; 05/04/16
LC_STOP_TIME: 40206.90 SOD {11:10:06.90} UT
LC_LIVE_TIME: 236.94 [sec], 98.5%
DELTA_TIME: 86159.41 [sec]
N_BINS: 100
TERM_COND: 0
LC_URL: sw00114753000msx.lc
SUN_POSTN: 24.64d {+01h 38m 34s} +10.25d {+10d 14' 43"}
SUN_DIST: 144.96 [deg]
MOON_POSTN: 117.95d {+07h 51m 47s} +26.35d {+26d 20' 55"}
MOON_DIST: 64.08 [deg]
MOON_ILLUM: 49 [%]
GAL_COORDS: 268.64, 82.73 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 178.96, 22.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-XRT Lightcurve.
- GCN notice #3264
T. Sakamoto (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC),
D. Burrows (PSU), M. Chester (PSU), J. Cummings (GSFC/NRC),
E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD),
J. Kennea (PSU) , H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS), M. Suzuki (Saitama),
M. Tripicco (GSFC-SSAI), J. Tueller (GSFC), D. Burrows (PSU),
on behalf of the Swift team:
At 11:04:44.5 UT, the Swift Burst Alert Telescope (BAT) triggered and
located on-board GRB050416 (trigger #114753). The BAT on-board
calculated location is RA, dec 188.478, 21.043 (J2000) with an
uncertainty of 3.00 arcmin (radius, 3-sigma, including estimated
systematic uncertainty). The BAT light curve shows double
structures with a duration of about three seconds. The peak
count rate measured by BAT was about 3000 counts/sec in the 15 -
350 keV band. The burst signal is mostly seen in 15-50 keV.
The XRT observed the target field at 11:06:12 UT and detected 17 counts in
a single CCD frame, just under the number needed for a reliable on-board
centroid. Initial indications based on the raw spectra and lightcurve
transmitted via TDRSS suggest that there is a real X-ray source in the
field. We will issue an update following the next ground station pass at
12:18 UT.
- GCN notice #3265
S. Bradley Cenko and Derek B Fox report on behalf of the Caltech-NRAO-
Carnegie GRB Collaboration:
We have imaged the error circle of the Swift GRB050416 with the
automated Palomar 60-inch Telescope. We find the presence of a bright,
stationary source not present in the DSS at the location:
RA: 12:33:54.6
Dec: +21:03:26.7
J2000.0
We tentatively identify this object as the afterglow of GRB050416
- GCN notice #3266
Gemma Anderson, Marilena Salvo, Josh Rich and Brian P Schmidt
(Australian National University) report on behalf of a larger collaboration
"We observed a 6' region covering the BAT position of the SWIFT burst
GRB 050416
using the ANU 2.3m telescope on April 12.51 UT in R band. The object
identified by Cenko and Fox is mvisible and clearly has faded in
comparison with their image. This indicate that this object is likely
the afterglow of GRB 050416
- GCN notice #3267
D. A. Frail (NRAO) and A. M. Soderberg (Caltech) report on behalf of
the Caltech-NRAO-Carnegie GRB Collaboration:
"We observed the field centered on the BAT position of the Swift burst
GRB 050416 (GCN#3264) using the VLA at a frequency of 8.46 GHz and
starting at 11:42 UT, about 37 minutes after the burst. There are no
bright radio sources (> 260 microJy) within 1 arcminute of the BAT
position. At the position of the afterglow candidate of Cenko and Fox
(GCN#3265), the peak radio flux is 20 +/- 51 microJy.
Further observations are planned."
- GCN notice #3268
J. A. Kennea, J. L. Racusin, D. N. Burrows (PSU), V. Mangano
(IASF/Palermo), T. Sakamoto (GSFC/NRC), N. Gehrels (NASA/GSFC) report on
behalf of the Swift XRT team:
The Swift BAT instrument detected a GRB at 11:04:45 UT on 16th April 2005
(GCN Circ 3264). The observatory executed an automated slew to the BAT
position and the XRT began taking data at 11:06:03 UT. The XRT was in
Auto state but was not able to centroid on the afterglow due to low source
brightness. From downlinked data we find a uncataloged fading X-ray source
located at:
RA(J2000) = 12:33:54.6,
Dec(J2000) = +21:03:24.
We estimate an uncertainty of about 5 arcseconds radius (90% containment). This
position is 49 arcseconds from the BAT position reported in GCN 3264, and
2.7 arcseconds from the P60 optical afterglow candidate reported in GCN
3265.
- GCN notice #3269
S. Bradley Cenko, Derek B. Fox, and Avishay Gal-Yam (Caltech) report on
behalf of the Caltech-NRAO-Carnegie GRB Collaboration:
We have imaged the field of GRB050416 with the Wide-Field Infrared
Camera (WIRC) mounted on the Palomar 200-inch Hale Telescope. Images
were taken in Ks-band and began approximately 6 minutes after the burst.
The afterglow candidate reported in GCN 3265 is clearly detected. The
object fades by 0.8 mag from approximately 11:15 UT to 12:05 UT (10 - 50
minutes after the burst), confirming the results of Anderson et al. (GCN
3266).
- GCN notice #3270
W. Li, R. Chornock, S. Jha, and A. V. Filippenko (University of
California, Berkeley) report:
"The Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory
robotically observed Swift GRB 050416 (Trigger #114753; Sakamoto et
al., GCN 3264). The first 3x15s R-band grid image started at 11:05:25
UT (40.5s after the burst), which did not detect the afterglow as
observed by Cenko and Fox (GCN 3265) to a limiting magnitude of about
16.5 when compared to the USNO A2.0 catalog. Our subsequent images
have varying exposure times from 15s to 360s, and were observed with
R, I, V, and z filters. Due to the depth of the images, only a 60s
I-band image started 11:12:09 UT (444.5s after the burst) has a
marginal detection of the afterglow. Further analysis is in progress."
- GCN notice #3271
E.Sonoda,S.Maeno,Y.Tokunaga,M.Yamauchi
(University of Miyazaki)
"We have observed the field covering the error circle of
GRB 050416 (GCN3264 ; Swift-BAT Trigger time is 11:04:57 UT)
with the unfiltered CCD camera on the 30-cm telescope
at University of Miyazaki.
The observation was started 11:09:18 UT on Apr.16.
After co-adding a set of 5 images (11:09:18 - 11:14:52 UT)
of 30 sec exposures, we have compared with the USNO A2.0 catalog.
Preliminary analysis shows there is no new source brighter than
16.7 mag. at the reported position by S.Bradley Cenko et al.
(GCN3265) and J.A.Kennea et al.(GCN3268)."
- GCN notice #3272
K. Torii (Osaka U.) reports
"The error region of GRB 050416 (Sakamoto, et al. GCN 3264) was
observed with the ART 14 inch telescope. VRcIc imaging started at
11:05:36 UT (52s after trigger) and 60s exposure was repeated.
As a result of the preliminary analyses, the optical afterglow (Cenko
and Fox GCN 3265; Anderson, et al. GCN 3266) is not detected in our
frames and the following upper limit is derived relative to USNO-A2.0
(R) magnitude.
Start(UT) Magnitude Exposure
11:07:53 >16.6Rc 60s
"
- GCN notice #3273
T. Sakamoto (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC),
J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS),
M. Suzuki (Saitama), M. Tashiro (Saitama U.), J. Tueller (GSFC),
on behalf of the Swift/BAT team:
At 11:04:44.5 UT Swift-BAT detected GRB 050416 (trigger=114753)
(GCN Circ 3264, Sakamoto et al.). The refined BAT ground position
is (RA,Dec) = 188.490, 21.053, [deg; J2000] +- 3 arcmin, (95%
containment). This is 0.7 arc minutes from the position determined
by the XRT (GCN Circ 3268, Kennea, et al.).
The BAT mask weighted light curve shows a single peak of about one
second duration followed by a small bump. Most of the emission is
in the 15-50 keV band. T90 (15-350 keV) is (2.4 +- 0.2) seconds
(estimated error including systematics).
The photon index of the spectrum is 2.9 +- 0.2. The fluences in
the 15-50 keV band and in the 15-350 keV band are
(2.8 +- 0.2) x 10^-7 erg/cm2 and (3.8 +- 0.4) x 10^-7 erg/cm2 respectively.
The peak photon fluxes in the 15-50 keV band and in the 15-350 band are
(4.4 + 0.8) ph/cm2/s and (4.8 +- 0.6) ph/cm2/s respectively. All the
quoted errors are in 90% confidence level.
The BAT team cautions that while there appears to be a deficit of
counts below 20 keV, this is likely due to systematic errors in the
response matrix being accentuated by the steep spectrum.
- GCN notice #3274
B. Kahharov, M. Ibrahimov, D. Sharapov (MAO), A.Pozanenko (IKI)
V.Rumyantsev (CrAO), G.Beskin (SAO) on behalf of larger collaboration
report:
We observed the Swift GRB050416 (Sakamoto et al. GCN3264) with 1.5m
telescope of the Maidanak Astronomical Observatory (MAO), Uzbekistan The
observation started at (UT) 15:34 , April 16 in R and B bands. We found a
source at the position afterglow (Cenko & Fox GCN3265). A preliminary
R-photometry of first frames against of USNO-B1.0 Catalog is the following:
Mean time Exposure Mag.
(UT) (s)
15:44 3x300 20.85 +/- 0.12
Observation is continuing.
- GCN notice #3275
G. Cusumano, V. La Parola, T. Mineo, V. Mangano (IASF/Palermo), G.
Chincarini, S. Campana, G. Tagliaferri, P. Romano, P. Giommi, M. Perri
(INAF-OAB), M. Capalbi (ASDC), D. N. Burrows, J. A. Kennea (PSU), N.
Gehrels (NASA/GSFC)
We have analyzed the Swift-XRT data from the first orbit observation of
GRB050416 (Sakamoto et al. 2005, GCN3264). The new refined coordinates
are:
RA(J2000) = 12:33:54.8
Dec(J2000) = +21:03:25.1
This position is 17.7 arcseconds from the BAT position given in GCN 3273
(Sakamoto et al. 2005) and 1.3 arcsec from the preliminary XRT position
(GCN3268, Kennea et al. 2005). We estimate an uncertainty of 5 arcseconds
radius (90% containment).
The [0.2-10] keV light curve in Photon Counting (PC) mode starts ~90
seconds from the BAT trigger (T0). We clearly detect a rapidly fading
source. The light curve can be fitted with a single power law with alpha=
-0.6 +/- 0.3.
A preliminary spectral fit to the PC data gives a spectral power law
photon index of 2.02+/-0.21 in the [0.2-10] keV band, with a column
density of (0.25+/-0.05)E22 cm^-2 (the Galactic line-of-sight absorption
is 2.06E20 cm^-2). The average estimated unabsorbed 0.2-10 keV flux is
1.7E-11 erg cm^-2 s^-1.
- GCN notice #3276
P. Schady (MSSL), T. Sakamoto (GSFC/NRC), K. McGowan (MSSL), P. Boyd
(GSFC/UMBC), P. Roming (PSU), J. Nousek (PSU), N. Gehrels (GSFC), on behalf of
the Swift UVOT team.
The Swift Ultra-Violet/Optical Telescope (UVOT) began settled observations of
the field of GRB 050416 (Sakamoto et al; GCN 3264) at 11:05:49 UT, 65s
after the BAT trigger. A comparison of the 100s finding chart in the V
filter against the Digitized Sky Survey reverals a new source inside the
XRT error circle at
RA = 12 33 54.56 Dec = +21 03 27.73
and consistent with the P60 positition reported by Bradley Cenko & Fox (GCN
3265). The V band magnitude is V = 19.38. The magnitude is based on preliminary
zero-points, measured in orbit and will require refinement with further
calibration.
Further detailed analysis is ongoing.
- GCN notice #3280
P. Schady (MSSL), T. Sakamoto (GSFC/NRC), K. McGowan (MSSL), P. Boyd
(GSFC/UMBC), P. Roming (PSU), J. Nousek (PSU), N. Gehrels (GSFC), on behalf of
the Swift UVOT team.
Starting with the data taken ~207s after the BAT trigger (Sakamoto et al., GCN
3264) we have co-added the early time data of GRB 050416 in each of the
Ultra-Violet/Optical Telescope (UVOT) U, B, and V bands. The co-added images
are made up of 9 x 10s exposures. A source is detected at the position of the
afterglow (Cenko & Fox, GCN 3265) in the U and B band with magnitudes U = 19.34
+/- 0.2 and B = 19.85 +/- 0.2. No source is detected in the V co-added
image down to a 5-sigma limiting magnitude V > 19.57. There is ~173s
difference between the start of the finding chart exposure, in which a
source was detected (Schady et al., 3276) and the co-added image.
The magnitudes are based on preliminary zero-points, measured in orbit and will
require refinement with further calibration.
- GCN notice #3286
Y. Qiu, C.L. Lu (BAO), Y.Q. Lou (THCA), K.Y. Huang (NCU), Y. Urata (RIKEN)
on behalf of EAFON report
" We have imaged the GRB 050416 optical afterglow position (Bradley et
al, GCN 3265) using 0.8-m telescope at XingLong Observatory, China.
The observations started at 18.65 UT (~ 7.57 hours after the
burst). Due to the bad weather condition (seeing ~ 4"), the limiting
magnitude of our R band co-added image is ~ 18.6 compared with
USNOB1.0 stars. No new source was detected under the limiting
magnitude.
This message may be cited."
- GCN notice #3287
K. Yanagisawa (OAO/NAO), H. Toda, and N. Kawai (Tokyo Tech) report on
behalf of the Mitsume Collaboration:
"The field of GRB050416 (Sakamoto et al.; GCN 3264) was observed by
the 3-color Mitsume 50cm Telescope at Okayama, Japan starting at
13:27 (UT). With the first 60 min exposure, we did not detect a
source brighter than V=18.0, R=19.6, and I=19.0 at the position of
the afterglow reported by Cenko and Fox (GCN 3265)."
- GCN notice #3290
G. Greco, C. Bartolini, A. Guarnieri, A. Piccioni (Bologna University),
G.Pizzichini (IASF-CNR, sezione di Bologna), R. Poggiani (Pisa
University) and I. Bruni (Osservatorio di Bologna) report:
"We observed the field of GRB 050416A (Sakamoto et al., GCN 3264) using
the 1.52-cm G. D. Cassini telescope of Bologna University, equipped with
the BFOSC CCD imager.
We obtained 2x1200s images in Rc light on 2005 April 16.345 and 16.361 UT.
Due to the poor weather conditions, a seeing ~ 3", and the nearness of
the Moon, we evaluate the limiting magnitude of our co-added images
at ~ 19.6.
We did not detect the OT given by Bradley et al. (GCN 3265).
This message may be cited."
- GCN notice #3312
P.A. Price (IfA), T. Minezaki (U. Tokyo), L. Cowie (IfA) and Y. Yoshii
(U. Tokyo) report on behalf of the UH-MAGNUM GRB collaboration:
We observed the optical afterglow of GRB 050416 (Cenko & Fox, GCN #3265)
with the automated MAGNUM telescope + MIP dual-beam optical-NIR imager,
commencing at April 16.53 UTC. The observations were performed in poor
seeing with clouds which prevented detection in the I and K bands.
Nevertheless, we detected the afterglow in the R, J and H bands. Based
on comparison with a single USNO-B1 star, we estimate that the optical
afterglow was about R ~ 21.3 mag at the epoch of our observations.
This message may be cited.
- GCN notice #3318
A. M. Soderberg (Caltech) reports on behalf of
the Caltech-NRAO-Carnegie GRB Collaboration:
"We observed the field centered on the XRT position of the Swift burst
GRB 050416a (GCN#3268) using the VLA at a frequency of 4.86 GHz
on Apr 22.04 UT (t ~ 5.6 days after the burst).
We detect a radio source coincident with the optical afterglow
position reported by Cenko & Fox (GCN#3265). The flux density of
the source is 260 +- 55 uJy.
Further observations are planned"
- GCN notice #3369
C. H. Ishwara-Chandra (National Centre for Radio Astrophysics, Pune,
India), A. P. Kamble and L. Resmi (Raman Research Institute, Bangalore,
India) report on behalf of a larger GRB collaboration:
We observed the GRB050416A field (GCN 3268) on 25th April 2005 (UT 17:30
to 22:20) with the Giant Meterwave Radio Telescope at 1280MHz. We do not
detect any source within the 5" error circle of the Swift XRT. At the
position of the VLA source reported by Soderberg et. al. (GCN 3318) we
place a 2 sigma upper limit of 94 micro Jansky.
This message may be cited.
[GCN OPS NOTE; This circular was delayed 2 hrs until an account could be set up.]
- GCN notice #3408
Derek B. Fox (Caltech) reports on behalf of a larger collaboration:
"We have created a summed image from the first 10.14 ksec of exposure
on GRB050416 (BAT trigger #114753; Sakamoto et al., GCN 3264) through
the "UVW2" filter of the Swift UVOT. Earlier reports have discussed
the detection of the optical afterglow of this event (Cenko & Fox, GCN
3265) in the U, B, and V filters (Schady et al., GCN 3280). The UVW2
sequence consists of nine ~10-second exposures taken from 4 to 15
minutes after the burst; two ~100-second exposures taken 18 and 29
minutes after the burst, and 11 ~900-second exposures taken from 92
minutes to 2 days after the burst. The final summed frame was
astrometrically registered to the USNO B-1.0 catalog.
At the position of the optical afterglow we detect a source at
>3-sigma confidence with a mean count rate of 6.0 +/- 0.7 cts/ksec
according to the default uvotdetect analysis. Examination of
individual frames suggests that the source is not distinguishable
above background in the individual short (10-s and 100-s) exposures,
being most prominent in the early ~900 second exposures of the
sequence.
The UVW2 filter bandpass is centered at 188 nm with a width of 76 nm.
Since it is unlikely that significant afterglow emission would be
detected blueward of the host galaxy Lyman limit at 91 nm -- with
significant suppression redward to the Lyman-alpha resonance at 122 nm
-- we suggest that this detection implies a redshift constraint for
GRB050416 of z <~ 1.0."
- GCN notice #3454
A. Henden (AAVSO/USNO) reports on behalf of the USNO GRB Team:
We have acquired BVRcIc all-sky photometry for 11x11arcmin
fields centered on the coordinates of recent GRB localizations
with the USNOFS 1.0-m telescope on one photometric night
but with bright moonlight. Stars brighter than V=12.0
are saturated and should be used with care. We have placed
the photometric data on our anonymous ftp site:
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050319.dat
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050401.dat
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050408.dat
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050416.dat
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050502a.dat
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb050509b.dat
The astrometry in these files is based on linear plate solutions
with respect to UCAC2. The external errors are less than 100mas.
The estimated external photometric error is about 0.03mag.
Since these bursts had identified optical afterglows, we expect
to improve the photometric calibration on subsequent nights.
As always, you should check the dates on the .dat file prior to
final publication to get the latest photometry. There is
a README file on the ftp directory to give you information
about the procedures used to calibrate these fields.
- GCN notice #3542
S. B. Cenko, S. R. Kulkarni, A. Gal-Yam (Caltech) and E. Berger
(Carnegie Observatories) report on behalf of the Caltech-NRAO-Carnegie
Collaboration:
We have obtained 2 x 30 minute spectra of the host galaxy of GRB 050416
(a) with the Low Resolution Imaging Spectrometer mounted on the 10-m
Keck I Telescope. Observations were taken on 6 June, 2005 UT. We
identify several emission lines including [OII], H-beta, H-gamma, and H-
delta at a redshift of z = 0.6535 +/- 0.0002.
The spectrum indicates the host galaxy is faint and blue with large
amounts of ongoing star formation. We note the redshift is consistent
with the prediction of Fox (3408) based on the afterglow detection in
the Swift UVOT UVW2 filter.
Using a fluence of 3.8e-7 erg/cm^2 (10 - 350 keV, GCN 3273), we find an
isotropic gamma-ray energy release of 7.0e50 ergs.
- astro-ph/0512149 from 6 Dec 2005
Sakamoto: Confirmation of the Eps -- Eiso (Amati) relation from the X-ray flash XRF 050416A observed by Swift/BAT
We report Swift Burst Alert Telescope (BAT) observations of the X-ray Flash
(XRF) XRF 050416A. The fluence ratio between the 15-25 keV and 25-50 keV energy
bands of this event is 1.5, thus making it the softest gamma-ray burst (GRB)
observed by BAT so far. The spectrum is well fitted by the Band function with
E^{\rm obs}_{\rm peak} of 15.0_{-2.7}^{+2.3} keV. Assuming the redshift of the
host galaxy (z = 0.6535), the isotropic-equivalent radiated energy E_{\rm iso}
and the peak energy at the GRB rest frame (E^{\rm src}_{\rm peak}) of XRF
050416A are not only consistent with the correlation found by Amati et al. and
extended to XRFs by Sakamoto et al., but also fill-in the gap of this relation
around the 30 - 80 keV range of E^{\rm src}_{\rm peak}. This result tightens
the validity of the E^{\rm src}_{\rm peak} - E_{\rm iso} relation from XRFs to
GRBs.
We also find that the jet break time estimated using the empirical relation
between E^{\rm src}_{\rm peak} and the collimation corrected energy E_{\gamma}
is inconsistent with the afterglow observation by Swift X-ray Telescope. This
could be due to the extra external shock emission overlaid around the jet break
time or to the non existence of a jet break feature for XRF, which might be a
further challenging for GRB jet emission, models and XRF/GRB unification
scenarios.
- astro-ph/0603738 from 27 Mar 2006
Mangano: Swift XRT Observations of the Afterglow of XRF 050416A
Swift discovered XRF 050416A with the BAT and began observing it with its
narrow field instruments only 64.5 s after the burst onset. Its very soft
spectrum classifies this event as an X-ray flash. The afterglow X-ray emission
was monitored up to 74 days after the burst. The X-ray light curve initially
decays very fast, subsequently flattens and eventually steepens again, similar
to many X-ray afterglows. The first and second phases end about 172 and 1450 s
after the burst onset, respectively. We find evidence of spectral evolution
from a softer emission with photon index $\Gamma \sim 3.0$ during the initial
steep decay, to a harder emission with $\Gamma \sim 2.0$. The spectra show
intrinsic absorption in the host galaxy. The consistency of the initial photon
index with the high energy BAT photon index suggests that the initial phase of
the X-ray afterglow may be the low-energy tail of the prompt emission. This
also requires that the spectral peak energy of the burst decreased from the
time of the BAT to the time of the XRT observation, becoming as low as $\simlt
1$ keV. Hardness ratio evolution during the prompt emission also supports this
interpretation. The lack of jet break signatures in the X-ray afterglow light
curve is not consistent with the Ghirlanda and Liang relations. The standard
uniform jet model can give a possible description of the XRF 050416A X-ray
afterglow for an opening angle larger than a few tens degrees, although
numerical simulations show that the late time decay is slightly flatter than
expected from on-axis viewing of a uniform jet. A structured Gaussian-type jet
model with uniform Lorentz factor distribution and viewing angle outside the
Gaussian core is another possibility although a full agreement with data is not
achieved with the numerical models explored.