- GCN/BACODINE POSITION NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 03 Oct 07 07:41:11 UT
NOTICE_TYPE: Swift-BAT GRB Position
TRIGGER_NUM: 292934, Seg_Num: 0
GRB_RA: 301.856d {+20h 07m 25s} (J2000),
301.948d {+20h 07m 47s} (current),
301.261d {+20h 05m 03s} (1950)
GRB_DEC: +10.960d {+10d 57' 35"} (J2000),
+10.983d {+10d 58' 57"} (current),
+10.814d {+10d 48' 50"} (1950)
GRB_ERROR: 3.00 [arcmin radius, statistical only]
GRB_INTEN: 12258 [cnts] Image_Peak=673 [image_cnts]
TRIGGER_DUR: 1.024 [sec]
TRIGGER_INDEX: 155 E_range: 50-350 keV
BKG_INTEN: 36030 [cnts]
BKG_TIME: 27637.73 SOD {07:40:37.73} UT
BKG_DUR: 8 [sec]
GRB_DATE: 14376 TJD; 276 DOY; 07/10/03
GRB_TIME: 27655.01 SOD {07:40:55.01} UT
GRB_PHI: 57.90 [deg]
GRB_THETA: 31.74 [deg]
SOLN_STATUS: 0x3
RATE_SIGNIF: 105.73 [sigma]
IMAGE_SIGNIF: 17.83 [sigma]
MERIT_PARAMS: +1 +0 +0 +0 +3 +23 +0 +0 +39 +1
SUN_POSTN: 188.94d {+12h 35m 44s} -3.85d {-03d 51' 05"}
SUN_DIST: 113.31 [deg] Sun_angle= -7.5 [hr] (East of Sun)
MOON_POSTN: 99.50d {+06h 37m 59s} +27.68d {+27d 40' 31"}
MOON_DIST: 135.64 [deg]
MOON_ILLUM: 51 [%]
GAL_COORDS: 51.67,-11.40 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 306.93, 30.41 [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: This trigger occurred at longitude,latitude = 144.34,19.09 [deg].
- red DSS finding chart
ps-file
- GCN NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 03 Oct 07 07:44:32 UT
NOTICE_TYPE: Swift-BAT GRB Lightcurve
TRIGGER_NUM: 292934, Seg_Num: 0
GRB_RA: 301.856d {+20h 07m 25s} (J2000),
301.948d {+20h 07m 47s} (current),
301.261d {+20h 05m 03s} (1950)
GRB_DEC: +10.960d {+10d 57' 35"} (J2000),
+10.983d {+10d 58' 57"} (current),
+10.814d {+10d 48' 50"} (1950)
GRB_DATE: 14376 TJD; 276 DOY; 07/10/03
GRB_TIME: 27655.01 SOD {07:40:55.01} UT
TRIGGER_INDEX: 155
GRB_PHI: 57.90 [deg]
GRB_THETA: 31.74 [deg]
DELTA_TIME: 32.00 [sec]
TRIGGER_DUR: 1.024 [sec]
SOLN_STATUS: 0x3
RATE_SIGNIF: 105.73 [sigma]
IMAGE_SIGNIF: 17.83 [sigma]
LC_URL: sw00292934000msb.lc
SUN_POSTN: 188.94d {+12h 35m 45s} -3.85d {-03d 51' 08"}
SUN_DIST: 113.31 [deg] Sun_angle= -7.5 [hr] (East of Sun)
MOON_POSTN: 99.53d {+06h 38m 07s} +27.67d {+27d 40' 19"}
MOON_DIST: 135.66 [deg]
MOON_ILLUM: 51 [%]
GAL_COORDS: 51.67,-11.40 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 306.93, 30.41 [deg] ecliptic lon,lat of the burst (or transient)
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: This trigger occurred at longitude,latitude = 144.34,19.09 [deg].
- GCN Circular #6837
P. Schady (MSSL-UCL), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
C. B. Markwardt (CRESST/GSFC/UMD), P. T. O'Brien (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL), G. Sato (GSFC/ISAS)
and R. L. C. Starling (U Leicester) report on behalf of the Swift
Team:
At 07:40:55 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 071003 (trigger=292934). The BAT on-board calculated location is
RA, Dec 301.856, +10.960 which is
RA(J2000) = 20h 07m 25s
Dec(J2000) = +10d 57' 35"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a multi-peaked
structure with a duration of about 25 sec. The peak count rate
was ~16000 counts/sec (15-350 keV), at ~0 sec after the trigger.
Because Swift is in the process of returning to normal operations,
automatic slewing to GRBs is currently disabled outside of
business hours (US EDT). Therefore, there
are no prompt XRT or UVOT observations of this burst.
Burst Advocate for this burst is P. Schady (ps AT mssl.ucl.ac.uk).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
- GCN Circular #6838
W. Li, University of California, Berkeley, on behalf of the KAIT GRB
team, report:
The robotic 0.76-m Katzman Automatic Imaging Telescope (KAIT) at Lick
Observatory observed GRB 071003 detected with Swift (Trigger 292934;
Schady et al. GCN 6837). The automatic sequence started at 07:41:37,
42 s after the burst. The BAT location has been monitored in V, I,
and clear filters, with varying exposure times. Our image processing
pipeline found a new object within the BAT error circle, with the
following position:
R. A. = 20:07:24.12
DEC. = +10:56:51.8 (J2000)
The OA has magnitude of 12.8 (calibrated with USNO B1.0) in a 5s
unfiltered exposure started at 07:41:37 UT, 42s after the BAT trigger.
The new object is close to a bright foreground star. Further Analysis
is ongoing. A finder chart can be found at
http://astro.berkeley.edu/~weidong/grb071003.finder.gif
This message may be cited.
- GCN Circular #6839
S. B. Cenko (Caltech) and D. B. Fox (Penn State) report on behalf of a
larger collaboration:
We have imaged the field of GRB071003 (Schady et al., GCN 6837) with the
automated Palomar 60-inch telescope. Observations began approximately 3
minutes after the burst (~ 07:44 UT 10 October) and were taken at high
airmass (~ 2.5). At the location of the optical afterglow candidate (Li,
GCN 6838) we detect a fading source in the g, R, i', and z' filters.
While photometry is complicated by the nearby bright star (Li, GCN 6838),
we estimate a magnitude of R ~ 14.5 in our first 60 s image (photometric
calibration was performed relative to several nearby objects from the
USNO-B catalog). The corresponding decay index is ~ -1.0.
- GCN Circular #6840
K. Misra, S. B. Pandey, Rupak Roy (ARIES, NainiTal, India) and Alberto
J. Castro-Tirado (IAA, Granada) on behalf of larger Indian GRB collaboration
The Swift GRB 071003 (Schady et al. GCN 6837) was observed using 1.04 m
Sampurnanand Telescope. The optical afterglow candidate reported by Li
(GCN 6838), Cenko & Fox (GCN 6839) is clearly seen in U and B band
frames in 300 sec exposure each. The fading nature of the source is seen
and U ~ 17 mag was measured around 7.5 hours after the burst. The
contamination due
to the nearby bright stars makes the photometry complicated. Multiband
observations and detailed observations are underway.
This message may be cited.
- GCN Circular #6841
H. Swan (U Mich), I. Smith (Rice), W. Rujopakarn (Steward), F. Yuan (U
Mich), S. Yost (College of St. Benedict), C. Akerlof (U Mich), M.
Skinner (Boeing), R. Russell (Aerospace Corporation) report on behalf of
the MARGE collaboration:
The AEOS Burst Camera (ABC) on the AEOS telescope, located at the Maui
Space Surveillance System on Haleakala, observed the fading counterpart
to GRB071003 (Swift trigger 292934 (P. Schady et al. GCN 6837)). The
images are unfiltered 10s exposures which started ~9 minutes after the
trigger and ended ~ 3 hours later.
We detect the OT first identified by W. Li (GCN 6838). A preliminary
analysis gives a magnitude of approximately 16.04+/-0.01 at 7:40:55 UT.
We calibrated the OT to the USNO-B1.0 R2 band magnitudes of several
nearby stars. We find that the early ABC data fades as a power law decay
with index ~1.9.
We note that the lightcurve has a flatter decay index after about 2000
seconds. This may be partially due to contamination from the nearby
10.79 mag star that will be resolved by more careful analysis. It is
possible that the OT is still visible (< 22nd mag).
Further observations are planned.
- GCN Circular #6842
T. Ukwatta (GWU), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS),
P. Schady (MSSL-UCL), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+584 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 071003 (trigger #292934)
(Schady, et al., GCN Circ. 6837). The BAT ground-calculated position is
RA, Dec = 301.857, 10.954 deg which is
RA(J2000) = 20h 07m 25.8s
Dec(J2000) = 10d 57' 16"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 34%.
The mask-weighted light curve shows a strong first peak with multiple
overlapping subpeaks starting at ~T-20sec, peaking at T+0 sec, and ending
at ~T+55 sec. The second, much weaker peak starts at ~T+130 sec, peaks at
~T+145 sec, and ends at ~T+220 sec. T90 (15-350 keV) is 150 +- 10 sec
(estimated error including systematics).
The time-averaged spectrum from T-7.6 to T+167.4 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.36 +- 0.07. The fluence in the 15-150 keV band is 8.3 +- 0.3 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.37 sec in the 15-150 keV band
is 6.3 +- 0.4 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
- GCN Circular #6843
D. A. Perley (UCB), J. X. Prochaska (UCSC), J. S. Bloom (UCB), and G.
Smith (UCO/Lick) report on behalf of the GRAASP collaboration:
We observed GRB 071003 (Schady et al., GCN 6837) with Keck/HIRESr
starting at UT 10:24 for one exposure of 1700s. The data were acquired
through very high airmass and have a low S/N ratio (~1 per 1.3 km/s
pixel at 5000A).
We identify no obvious absorption features in either the 2D image nor 1D
spectrum. Allowing for the following priors, we place the following
upper limits on the GRB redshift:
1. Assuming the GRB host galaxy would emit no flux below the Lyman
limit, we infer z_GRB < 3.4
2. Assuming the GRB host galaxy would imprint a damped Lya profile on
the spectrum, we infer z_GRB < 2.5
3. Assuming the GRB host galaxy would imprint a strong MgII absorber on
the spectrum (EW > 1A), we infer z_GRB < 1.
Given these constraints and the U-band detection from Mishra et al. (GCN
6840), it is possible that this GRB is at low redshift. We encourage
follow-up observations to search for, or place limits on, a low-redshift
host galaxy or associated supernova.
- GCN Circular #6844
W. Li, R. Chornock, A. V. Filippenko, D. A. Perley, J. S. Bloom (University
of California, Berkeley), on behalf of the KAIT GRB team, report:
We have analyzed the KAIT observations of the GRB 071003 optical
afterglow (OA) reported by Li (GCN 6838) and confirmed by Cenko
and Fox (GCN 6839). Our preliminary unfiltered light curve, calibrated
with USNO B1.0, shows two potential breaks for the OA in the first
10 minutes after the burst. We measured a steep power law index of
-1.52 +/- 0.06 between t = 0.7 min and 1.2 min after the burst (from
5 x 5s images), possibly signaling the detection of the optical reverse
shock emission from the GRB. A shallower power law index of -0.89
+/- 0.03 is measured between t = 1.2 min and 4.3 min (from 3 images),
suggesting a break in the light curve between t = 1.2 min to 2.8 min.
The second potential break occurred at about 4 minutes after the burst,
with the power law decay index measured as -1.85 +/- 0.10 from 3 images
observed between t = 4.3 min to 7.4 min. We note this power law decay
index is consistent with the value reported by Swan et al. (GCN 6841)
at later times. Our observations ended at about 27 minutes after the
burst due to physical limits of KAIT. The analysis of all the data is
still ongoing.
The overall behavior of the OA of GRB 071003 OA is similar to that of
GRB 061126 (Perley et al., astro-ph/0703538), but with the breaks
occurring at an earlier stage of the evolution. We expect contamination
from the nearby bright star as discussed by Li (GCN 6838), Cenko and Fox
(GCN 6839), and Misra et al. (GCN 6840) to slightly affect the above
power indices, but not the overall photometric behavior.
Some selected KAIT unfiltered photometry:
t_start(s) Exptime(s) Mag Mag(err)
42 5.000 12.83 0.02
67 5.000 13.56 0.03
249 20.000 14.82 0.03
431 20.000 15.89 0.06
This message may be cited.
- GCN Circular #6845
R. Starling (U. Leicester) and P. Schady (MSSL/UCL) report on behalf of
the Swift team:
Swift XRT observed the GRB 071003 (trigger=292934, Schady et al., GCN
Circ. 6837) beginning 22 ks after the BAT trigger.
In 2650 s of Photon Counting mode data spanning 22--25 ks after the
trigger a bright X-ray source (approximate count rate 0.1 count/s) is
detected at the position RA,Dec = 301.85102, +10.94688 deg, equivalent to:
RA(J2000) = 20h 07m 24.25s
Dec(J2000)= +10d 56' 48.8"
with an error of radius 5.7 arcseconds (90%, including boresight
uncertainties). This is 35.5 arcseconds from the BAT refined position
(Ukwatta et al., GCN Circ. 6842) and 3.6 arcseconds from the optical
afterglow position (Li, GCN Circ. 6838).
Further analysis will be reported in a subsequent circular.
This is an official product of the Swift XRT team.
- GCN Circular #6846
C.Y. Shih, Y.H. Lee, Y. Urata and K.Y. Huang on behalf of the EAFON team
"We have performed R-band observations for GRB 071003 field (Schady et
al., GCN 6837; Li GCN 6838) using Lulin 1-m telescope at 11:41:44 UT
(about 4 hours after the burst). There is no optical afterglow
emission in our combined image with R<21.5 (3-sigma limit) derived
from USNO-B1.0 red stars."
- GCN Circular #6847
D. A. Perley, W. Li, J. S. Bloom (UC Berkeley), C. Fassnacht (UC Davis),
and P. Nugent (LBL) report:
On the night of 2007-10-04 (UT) we imaged the field of GRB 071003 with
Keck I + LRIS, in g+R filters simultaneously for 3 exposures of 300
seconds, starting at 04:49 UT.
We detect at the position reported by Li (GCN 6838) a bright source with
an estimated magnitude of R~20, though photometry is complicated by the
presence of the nearby 11th magnitude star. The position is consistent
within 0.3" of the KAIT detection, strongly suggesting that this is the
same source. Given the rapid fading noted in earlier circulars (GCN
6841, GCN 6844) and the limit of R > 21 reported by Shih et al. (GCN
6848) this may suggest that the optical afterglow is rebrightening,
either due to a late-time flare or a rising low-redshift supernova.
We also note what appears to be a faint, extended object approximately
2" to the southwest of the afterglow (towards the bright star), which
may be the host galaxy of this burst.
Further analysis is in progress. Additional observations are strongly
encouraged to further examine the nature of this transient.
- GCN Circular #6848
C. Guidorzi (U. Bicocca & INAF-OAB), D.F. Bersier, R.J. Smith,
C.J. Mottram, M.F. Bode, D. Carter, S. Kobayashi, A. Melandri,
C.G. Mundell, I.A. Steele (Liverpool JMU), A. Gomboc (U. Ljubljana),
P. O'Brien, E. Rol, N. Bannister (U. Leicester) report:
The 2-m Faulkes Telescope North robotically followed up GRB071003
(Schady et al., GCN Circ. 6837) beginning 189 s after the GRB
trigger time (UT 07:40:55).
We clearly detect the afterglow (Li et al., GCN Circ. 6838).
We measure the following magnitudes in the R filter:
Start Time from trigger
(s) Exp(s) mag R
----------------------------------------------------
189 10 14.72 +/- 0.01
210 10 14.81 +/- 0.01
229 10 14.90 +/- 0.01
----------------------------------------------------
Magnitudes are calibrated with respect to several nearby
USNO-B1 objects.
- GCN Circular #6849
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
and T. Cline on behalf of the Konus-Wind team report:
The long GRB 071003 (Swift-BAT trigger #292934:
Schady et al., GCN 6837; Ukwatta et al., GCN 6842) triggered
Konus-Wind at T0=27655.120 s UT (07:40:55.120).
The burst light curve shows a multipeaked structure
with a duration of ~30 s. There is a hint of
the weak extended emission reported by BAT
(Ukwatta et al., GCN 6842) in the Konus-Wind data.
As observed by Konus-Wind the burst
had a fluence of 5.32(-0.67, +0.30)x10^-5 erg/cm2,
and a 64-ms peak flux measured from T0+2.464 s
of 1.22(-0.22, +0.19)x10^-5 erg/cm2/s
(both in the 20 keV - 4 MeV energy range).
The time-integrated spectrum of the burst
(from T0 to T0+30.720 s) is well fitted
(in the 20 keV - 4 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ E^(-alpha)*exp(-E*(2-alpha)/Ep)
with alpha = 0.97 +/- 0.07
and Ep = 799(-100, +124) keV (chi2 = 74.2/74 dof).
The spectrum of the most intense part
(from T0 to T0+14.336 s) is well fitted
(in the same range)
by a power law with exponential cutoff model
with alpha = 0.76 (-0.07, +0.06)
and Ep = 780(-70, +81) keV (chi2 = 75.6/74 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/GRB071003_T27655/
- GCN Circular #6850
D. A. Perley, R. Chornock, J. S. Bloom (UC Berkeley), C. Fassnacht, and
M. W. Auger (UC Davis) report on behalf of GRAASP:
We obtained spectroscopic follow-up of the bright transient associated
with GRB 071003 (Schady et al., GCN 6837; Li, GCN 6838) starting at
07:51 UT on the night of 2007-10-04 using Keck I + LRIS (range 3300-8630
Angstroms). Two 10-minute exposures were acquired.
The source is well-detected and a preliminary reduction reveals a smooth
spectrum consistent with a GRB afterglow with multiple absorption-line
systems. We identify a pair of absorption features at 5870 and 5886
Angstroms with the Mg II 2796, 2803 Angstrom doublet at a redshift of
1.100. Other absorption features are consistent with Fe II 2382, 2586,
and 2599 Angstroms at this redshift. This absorption system sets a
lower limit on the redshift of the GRB of z=1.100.
In addition, numerous lines (e.g., Mg II 2796, 2803 Angstroms, Mg I 2852
Angstroms, and Fe II 2599 Angstroms) are present from an intervening
absorption system at z=0.372.
No strong supernova features or host-galaxy emission lines are seen in
the spectrum.
This suggests that the transient is a GRB afterglow undergoing a bright
late-time optical flare, similar to the afterglow of GRB 070311 (e.g.
Halpern & Armstrong, GCN 6203; Guidorzi et al., astroph/0708.1383),
rather than a supernova. That flare peaked at R~22 approximately two
days after the burst. Improved photometry of the optical transient
associated with GRB 071003 gives a magnitude of R = 19.1 +/- 0.3 at
04:49 UT (0.88 days after the trigger) and further rebrightening appears
possible. Further monitoring is strongly encouraged.
- GCN Report 87.1
GCN_Report 87.1 has been posted:
http://gcn.gsfc.nasa.gov/reports/report_87_1.pdf
by P. Schady
at MSSL-UCL
titled: "Swift Observations of 071003"
- GCN Circular #6851
D. Fugazza (INAF-OABr), F. Fiore, V. D'Elia (INAF-OAR), P. D'Avanzo
(INAF-OABr), S. Piranomonte, L.A. Antonelli (INAF-OAR), G. Chincarini
(Univ. Bicocca), S. Covino, G. Tagliaferri (INAF-OABr), M. Della Valle
(INAF-OAA), A. Fernandez Soto (Univ. Valencia) report on behalf of the
MISTICI collaboration:
We observed the optical afterglow of GRB 071003 (Schady et al., GCN
6837; Li et al. GCN 6838; Cenko et al. GCN 6839) with the ESO-Very Large
Telescope equipped with the FORS2 camera in spectroscopic mode. We took
a 1800s spectrum with the grism 600B (with a resolution of R = 780) on
Oct 04.055 UT (~ 0.735 days after the burst), under good seeing
conditions (1.0").
The detection of a MgII system at z=1.100 (Perley et al. GCN 6850),
cannot be confirmed by our data, because the 2803 AA component of the
MgII doublet is contamined by the NaI 5891 and 5897 AA doublet of the
nearby bright star.
We also find significant lines at 5417 and 5430 AA, which we interpret
as the MgII absorption doublet at 2797 and 2803 AA at z=0.937. FeII 2382
is also detected at the same redshift.
In addition, we find two more significant absorption lines (5417 and
5446 AA), that can be identified as Ca H and K at z=0.372.
Alternatively, the 5446 AA line can be interpreted as the 2803 AA
component of the MgII doublet at z=0.942, with the 2797 AA component
sharing the absorption feature at 5430 AA with the MgII 2803 of the
system at z=0.937. This can be another line-locking example like that of
the CIV system of GRB 021004 at z=2.3 (Fiore et al. 2005, ApJ, 624, 853;
Starling et al. 2005, MNRAS, 360, 305 ).
Finally, we find another MgII doublet at ~4000 AA (z=0.370), not
consistent with the Ca system at z=0.372. No emission lines are visible.
In summary our analysis of the FORS2 spectrum puts a lower limit on the
redshift of GRB 071003 to z=0.937.
We thank VLT staff for performing the observations, in particular Thomas
Szeifert and Alain Smette.
- GCN Circular #6853
P. Chandra (UVA/NRAO) and D. A. Frail (NRAO) report on behalf of the
Caltech-NRAO-Carnegie GRB Collaboration:
"We observed the field centered on the BAT position of the Swift burst
GRB 070923 (GCN#6837) using the VLA at a frequency of 8.46 GHz
and starting at 1.85 UT on Oct 5, 2007. We detect the radio afterglow at
KAIT optical position (GCN#6838) with flux density of 393 +/- 55 uJy.
Further observations are planned.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."
- GCN Circular #6855
R. Starling, P.A. Evans, K.L. Page, A.P. Beardmore (U. Leicester) and P.
Schady (MSSL/UCL) report on behalf of the Swift team:
We report on Swift XRT observations of the GRB 071003 (trigger=292934,
Schady et al., GCN Circ. 6837) beginning 22.3 ks and ending 244 ks after
the BAT trigger, totalling 29.6 ks of photon counting mode data.
We refine the position given in Starling and Schady, GCN Circ. 6845, to
RA,Dec(J2000) = 301.85090, 10.947225 deg, equivalent to:
RA(J2000) = 20h 07m 24.22s
Dec(J2000)= +10d 56' 50.0"
with an error of radius 5.5 arcseconds (90%, including boresight
uncertainties). This is 1.3 arcseconds away from the initial XRT position
and 2.3 arcseconds from the optical transient (Li, GCN Circ. 6838).
The light curve is best fit with a broken power law with initial decay
slope of alpha_1 = 1.0(+0.2/-0.4), T_bk = 3.9(+0.8/-0.4)E4 s and
alpha_2 = 1.8(+/-0.4).
The spectrum can be modelled with a power law of photon index Gamma =
2.1(+/-0.2) with fixed Galactic absorption of nH = 1.4E21 cm^-2 and
allowing for intrinsic absorption at z = 1.1 (lower limit from Perley et
al., GCN Circ. 6850) which we find is consistent with zero.
The mean observed (unabsorbed) 0.3-10 keV flux is 7E-13 (1E-12)
erg/cm^2/s.
The count to flux conversion from these data is approximately 1 ct/s =
4.7E-11 erg/cm^2/s.
This is an official product of the Swift XRT team.
- GCN Report 87.2
GCN_Report 87.2 has been posted:
http://gcn.gsfc.nasa.gov/reports/report_87_2.pdf
by P. Schady
at MSSL-UCL
titled: "Final Swift Observations of GRB 071003"
- GCN Circular #7010
L. K. Pollack (UC Santa Cruz), M. A. van Dam (WM Keck Observatory), D.
Le Mignant (WM Keck Observatory, UC Santa Cruz), E. M. Johansson (WM
Keck Observatory), D. A. Perley (UC Berkeley), and J. S. Bloom (UC
Berkeley) report:
On October 19 at UT 05:14:04 we observed the afterglow of GRB 071003
(Schady et al., GCN 6837; Li, GCN 6838; Cenko et al. GCN 6839) with the
NIRC2 narrow-field camera (0.01 arcsec/pixel) on Keck II using natural
guide star adaptive optics (NGS AO). We took 15 exposures, each of 60
seconds and 2 coadds, resulting in a total integration time of 30
minutes. The natural guide star is located 6.5 arcseconds west of the
afterglow position, and has R=11 mag.
The K=12.011 +/- 0.024 mag 2MASS star located 7.8 arcseconds east of the
afterglow position was used as a photometric calibrator. Assuming no
changes in the AO-corrected PSF over these distances, we measure the
afterglow to have K' = 21.58 +/- 0.03. We find no host galaxy at the
position of the afterglow.
We detect the galaxy previously reported by Perley et al. (GCN 6874) at
a position 2.07 arcseconds southwest of the afterglow position.
Photometry on this extended object is difficult in the presence of the
bright nearby star; however, we measure the galaxy to have an
approximate brightness of K'=19.1 +/- 0.1 mags within an aperture of a
0.5 arcsecond radius.
An image of the observations has been posted to:
http://www.ucolick.org/~pollack/071003.jpg
We thank the Keck staff for performing these observations. In
particular, we would like to acknowledge the help of Al Conrad.
- 0805.2394from 17 May 2008
Perley: GRB 071003: Broadband Follow-up Observations of a Very Bright Gamma-Ray Burst in a Galactic Halo
Abstract: The optical afterglow of long-duration gamma-ray burst (GRB) 071003 is among
the brightest yet to be detected from any GRB, with R ~ 12 mag in Katzman
Automatic Imaging Telescope observations starting 42 s after the GRB trigger,
including filtered detections during prompt emission. However, our high
signal-to-noise ratio afterglow spectrum displays only extremely weak
absorption lines at what we argue is the host redshift of z=1.60435 - in
contrast to the three other, much stronger Mg II absorption systems observed at
lower redshifts. Together with Keck Adaptive Optics observations which fail to
reveal a host galaxy coincident with the burst position, our observations
suggest a halo progenitor and offer a cautionary tale about the use of Mg II
for GRB redshift determination. We present early through late-time observations
spanning the electromagnetic spectrum, constrain the connection between the
prompt emission and early variations in the light curve (we observe no
correlation), and discuss possible origins for an unusual, marked rebrightening
that occurs a few hours after the burst: likely either a late-time refreshed
shock or a wide-angle secondary jet. Analysis of the late-time afterglow is
most consistent with a wind environment, suggesting a massive star progenitor.
Together with GRB 070125, this may indicate that a small but significant
portion of star formation in the early universe occurred far outside what we
consider a normal galactic disk.
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