GRB 080804
GCN Circular 8056
Subject
GRB 080804: ROTSE-III Detection of Optical Counterpart
Date
2008-08-04T23:28:02Z (17 years ago)
From
Wiphu Rujopakarn at U AZ/Steward <wiphu@as.arizona.edu>
W. Rujopakarn (Steward), E.S. Rykoff (UCSB) report on behalf of the ROTSE
collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded to GRB 080804 (Swift trigger 319016). The first image was at
23:20:34.3 UT, 19.6 s after the burst (6.3 s after the GCN notice time).
The unfiltered images are calibrated relative to USNO A2.0. We detect a
17.2 magnitude, brightening source with coordinates:
21:54:40.1 -53:11:03.8 (J2000), with positional uncertainty
of 1" or better
start UT mag mlim(of image)
----------------------------------
23:20:50.2 17.2 16.9
This source is not visible in DSS (second epoch), 2MASS or the MPChecker
database.
A jpeg image is available at
http://www.rotse.net/images/gsb319016_3c01_img.jpg Note that the object
marked 38 is the candidate in question.
Continuing observations are in progress.
GCN Circular 8057
Subject
GRB 080804: Swift detection of a burst with optical afterglow
Date
2008-08-04T23:37:27Z (17 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
J. L. Racusin (PSU), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), M. M. Chester (PSU),
N. Gehrels (NASA/GSFC), D. Grupe (PSU),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
C. Pagani (PSU), D. M. Palmer (LANL), M. C. Stroh (PSU) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:
At 23:20:14 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080804 (trigger=319016). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 328.701, -53.195 which is
RA(J2000) = 21h 54m 48s
Dec(J2000) = -53d 11' 40"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows multiple overlapping
peaks with a duration of about 20 sec. The peak count rate
was ~1500 counts/sec (15-350 keV), at ~3 sec after the trigger.
The XRT began observing the field at 23:21:53.7 UT, 99.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 328.66583, -53.18532 which
is equivalent to:
RA(J2000) = 21h 54m 39.80s
Dec(J2000) = -53d 11' 07.2"
with an uncertainty of 3.0 arcseconds (radius, 90% containment). This
location is 83 arcseconds from the BAT onboard position, within the BAT
error circle.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of
1.63e+20 cm^-2 (Kalberla et al. 2005).
The initial flux in the 2.5 s image was 5.50e-10 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of nominal 100 seconds with the White
(160-650 nm) filter starting 109 seconds after the BAT trigger. There is a
candidate afterglow in the list of sources generated on-board at
RA(J2000) = 21:54:40.2 = 328.6675
DEC(J2000) = -53:11:05 = -53.18472
with a 1-sigma error radius of about 1.0 arc sec. The estimated white
magnitude is 16.8 with a 1-sigma error of about 0.5 mag. No correction
has been made for a Galactic extinction corresponding to a reddening of
0.02 mag along the line of sight.
Burst Advocate for this burst is J. L. Racusin (racusin AT astro.psu.edu).
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 8058
Subject
GRB 080804: UVES redshift
Date
2008-08-05T03:21:55Z (17 years ago)
From
Antonio Deugarte at IAA-CSIC <deugarte@iaa.es>
Christina C. Thoene (DARK/NBI), Antonio de Ugarte Postigo (ESO),
PaulM. Vreeswijk, Daniele Malesani (DARK/NBI), Palli Jakobsson
(Univ. Hertfordshire) report on behalf of a larger collaboration:
We observed the afterglow of GRB 080804 (Racusin et al., GCN 8057;
Rujopakarn & Rykoff, GCN 8056) with the UVES high-resolution
spectrograph at the VLT. Observations started on 2008 Aug 5.008 UT (50
min after the GRB). We obtained two spectra with exposure times of 30
and 45 minutes. The spectra cover the wavelength range from 3500 to
9460 Angstroms.
We detect a strong DLA as well as a large range of absorption lines
including SiII, SII, OI, CII, AlII, MgI and SiII* from which we derive
a redshift of z=2.2045.
We acknowledge excellent support from the observing staff at Paranal,
including Swetlana Hubrig, Thomas Rivinius, and Yuri Belestky. We are
especially indebted to Swetlana Hubrig and Martin Netopil for using
part of their telescope time.
GCN Circular 8064
Subject
GRB 080804: Faulkes Telescope South observations
Date
2008-08-05T15:05:59Z (17 years ago)
From
Cristiano Guidorzi at INAF-OAB <cristiano.guidorzi@brera.inaf.it>
C. Guidorzi (INAF-OAB) and I. Steele (LJMU) on behalf of a
larger collaboration report:
On 2008 August 05 (12:44:12 UT) we began observing the field of GRB 080804
(Racusin et al. GCN Circ. 8057) with the Faulkes Telescope South using
the R filter.
In our coadded frame we detect the optical afterglow at the position
fully consistent with that reported by Swift-UVOT (Racusin et al. GCN
Circ. 8057) and slighly outside the error circle given by ROTSE-III
(Rujopakarn et al. GCN Circ. 8056) which is 1.5 arcsec away.
Telescope Filter T_mid[hr] Exposure[s] Mag
-----------------------------------------------------------
FTS R 14.235 1200 21.6 +/- 0.1
-----------------------------------------------------------
The calibration was performed using the R2 magnitudes of several
USNOB-1 catalogue field objects. The uncertainty reported above does
not include the additional ~0.3 mag of the USNOB-1 catalogue.
From the comparison with the value reported by UVOT we infer an
average power-law decay index of ~0.7.
GCN Circular 8065
Subject
GRB080804: Gemini South redshift confirmation
Date
2008-08-05T15:34:42Z (17 years ago)
From
Antonino Cucchiara at PSU <cucchiara@astro.psu.edu>
A. Cucchiara, D. B. Fox (Penn State), S. B. Cenko (Caltech) and E. Berger
(Harvard U.) report on behalf of a larger collaboration:
Starting at 01:27 UT on 2008 August 5 we observed the optical counterpart
of GRB 080804 (Rujopakarn et al., GCN 8056, Racusin et al., GCN 8057) using
Gemini-South with GMOS spectrograph (R~1200).
We acquired 2x900s spectra which covered the wavelength range 4000A-8000A
and 2x900s spectra covering the range 6000A-10000A.
We detect some of the metal absorption features identified by Thoene et al.
(GCN 8058), like FeII (1608, 2260), NiII (1741 and 1751) and we also detect
MgII doublet (2796,2803). We also detect part of the red wing of the Lyman
break indicating a possible DLA associated with the grb host galaxy.
All these features confirm that the grb redshift is z = 2.20.
We thank the Gemini staff for conducting these observations.
GCN Circular 8066
Subject
GRB 080804: Enhanced Swift-XRT position
Date
2008-08-05T15:42:09Z (17 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester)
report on behalf of the Swift-XRT team.
Using 6979 s of XRT Photon Counting mode data and 8 UVOT
images for GRB 080804, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 328.66755, -53.18483 which is equivalent
to:
RA (J2000): 21h 54m 40.21s
Dec (J2000): -53d 11' 05.4"
with an uncertainty of 1.5 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position
can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is
described by Goad et al. (2007, A&A, 476, 1401
http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an
extension of this method.
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 8067
Subject
GRB 080804, Swift-BAT refined analysis
Date
2008-08-05T15:54:46Z (17 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
C. Markwardt (GSFC/UMD), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), K. McLean (GSFC/UMD), D. Palmer (LANL),
J. L. Racusin (PSU), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 080804 (trigger #319016)
(Racusin, et al., GCN Circ. 8057). The BAT ground-calculated position is
RA, Dec = 328.675, -53.189 deg which is
RA(J2000) = 21h 54m 41.9s
Dec(J2000) = -53d 11' 20.2"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 19%.
The mask-weighted light curve shows the main peak starting at ~T-10sec,
peaking at ~T+2 sec, and ending at ~T+100 sec. T90 (15-350 keV) is
34 +- 16 sec (estimated error including systematics).
The time-averaged spectrum from T-0.4 to T+62.8 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.19 +- 0.09. The fluence in the 15-150 keV band is 3.6 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+1.57 sec in the 15-150 keV band
is 3.1 +- 0.4 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/319016/BA/
GCN Circular 8069
Subject
GRB 080804: Swift/UVOT Refined Analysis
Date
2008-08-05T18:29:58Z (17 years ago)
From
Paul Kuin at MSSL <npkuin@googlemail.com>
N. P. M. Kuin (MSSL/UCL), and J. L. Racusin (PSU), report
on behalf of the Swift UVOT team
The Swift UltraViolet/Optical Telescope (UVOT) began observations
of GRB 080804, on August 4, 2008, at 23:21:45 UT, 91 seconds after
the initial Swift BAT trigger (Racusin et al., GCN Circ. 8057), and
started the finding chart exposure in the white filter at 111
seconds after the trigger.
The refined uvot position of GRB080804 is RA=0328.66750 Dec=-53.18461
deg.(= 21:54:40.2 -53:11:04.6), with an accuracy of 0.4", consistent
with the positions reported in GCN Circ. 8056 (Rujokaparn et al.),
8057 (Racusin et al.) and 8066 (Beardmore et al.).
The magnitudes with 1-sigma errors for GRB080804 are given below
for the initial observation sequence.
Filter Tstart(s) Tstop(s) Exp(s) Magnitude
wh 111 210 98.2 16.83 +/- 0.03
wh 711 720 9.6 18.3 +/- 0.16
v 217 616 393.5 17.17 +/- 0.05
v 752 771 19.4 17.85 +/- 0.30
uvm2 623 642 19.5 >17.6 (3 sigma UL)
uvw1 648 667 19.4 >18.2 (3 sigma UL)
b 697 706 9.6 18.1 +/- 0.27
u 672 691 19.4 17.4 +/- 0.17
uvw2 727 746 19.5 >18.2 (3 sigma UL)
uvw1 648 7442 529.3 20.9 +/- 0.4
uvm2 623 7237 529.4 >20.8 (3 sigma UL)
uvw2 727 6827 1179.5 >21.8 (3 sigma UL)
The upper limits in uvw2, uvm2, and weak detection in uvw1 are
consistent with the reported redshift of z=2.2045 by Thoene
et al. (GCN Circ. 8058).
The values quoted above are on the UVOT Photometric System
(Poole et al, 2008, MNRAS 383,627). They are not corrected for the
expected galactic reddening of E(B-V) = 0.016 in the direction of
the burst (Schlegel et al. 1998).
GCN Circular 8070
Subject
GRB 080804: Swift-XRT Refined Analysis
Date
2008-08-05T20:24:05Z (17 years ago)
From
Judith Racusin at PSU <racusin@astro.psu.edu>
J. Racusin, C. Pagani (PSU) report on behalf of the Swift-XRT team:
We have analysed the first five orbits of Swift-XRT data available for GRB
080804 (Racusin et al., GCN 8057) consisting of 123 s of WT mode data, and
11.0 ks of PC mode data. The enhanced XRT position is given in Beardmore
et al. (GCN Circ. 8066).
The preliminary 0.3-10.0 keV lightcurve can be fit with a single power-law
with a decay index of 1.09+/-0.03.
The WT and PC spectra can be jointly fit with an absorbed power-law with a
photon index of 1.6 +/- 0.2. The intrinsic absorption is at a level of
1.7e21 cm^-2 (using z=2.2045, Thoene et al., GCN Circ. 8058), in addition
to the Galactic absorption along the line of sight (1.6e20 cm^-2, Kalberla
et al. 2005). The average observed (unabsorbed) flux is 2.5e-10 (2.6e-10)
ergs cm^-2 s^-1 and 1.2e-11 (1.2e-11) ergs cm^-2 s^-1, for the WT and PC
spectra respectively.
Assuming the X-ray emission continues to decline at the same rate, we
predict a 0.3-10.0 keV XRT count rate of 0.008 counts/s at T+24hr, which
corresponds to an observed flux of 3.4e-13 ergs cm^-2 s^-1.
This Circular is an official product of the Swift-XRT team.
GCN Circular 8073
Subject
GRB 080804: ATCA Radio Observations
Date
2008-08-06T03:36:41Z (17 years ago)
From
Alexander van der Horst at NASA/MSFC <avdhorst@science.uva.nl>
A.J. van der Horst (NASA/ORAU) and C. Kouveliotou (NASA/MSFC) report:
"We observed the position of the GRB 080804 afterglow at 4.8 and 8.6 GHz
with the Australia Telescope Compact Array at August 5 16.92 UT to 22.45
UT, i.e. 0.73 - 0.96 days after the burst (GCN 8057).
We do not detect a radio source at the position of the optical afterglow
(GCN 8056). The formal flux measurement for a point source at the location
of the optical counterpart is -41 +/- 64 microJy at 4.8 GHz, and 40 +/- 63
microJy at 8.6 GHz.
We would like to thank the staff of the Australia Telescope National
Facility, in particular Angel Lopez-Sanchez and Philip Edwards, for
scheduling and obtaining these Target of Opportunity observations."
GCN Circular 8075
Subject
GRB 080804: GROND observations
Date
2008-08-06T07:58:12Z (17 years ago)
From
Thomas Kruehler at MPE/MPI <kruehler@mpe.mpg.de>
T. Kruehler, F. Schrey, J. Greiner, A. Yoldas, C. Clemens, S. McBreen
(all MPE Garching),
A. Kupcu Yoldas (ESO) and G. Szokoly (Eoetvoes Univ., Budapest) report on
behalf of the GROND team:
GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI
telescope at La Silla Observatory (Chile), started observations of the
field of GRB 080804 (Racusin et al. 2008, GCN #8057) in g'r'i'z'JHK at
23:26 UT, 16 min after the burst. We clearly detect the optical
afterglow (Rujopakarn & Rykoff 2008, GCN #8056) in all filters at a
position consistent with UVOT (Racusin et al. 2008, GCN #8057) and the
Faulkes Telescope South (Guidorzi & Steele, GCN #8064). Observations
continued for 65 min and were resumed at 06:30 UT for 30 min.
Assuming the USNO-B1 star at RA(J2000)=328.6627, DEC(J2000)=-53.18288
having R2=18.08 mag, we measure the following r' magnitudes, not
corrected for the expected Galactic foreground extinction corresponding
to a reddening of E_(B-V)=0.02 (Schlegel et al. 1998):
Filter T_mid Exposure Brightness
(s) (s) (mag)
-----------------------------------------
r' 1160 67 18.09 +- 0.03
r' 1565 67 18.37 +- 0.03
r' 1996 115 18.66 +- 0.02
r' 2768 115 18.96 +- 0.02
r' 3672 375 19.25 +- 0.02
r' 26112 375 21.02 +- 0.04
The reported magnitudes are a subset of the complete observation
consisting of 24 individual frames. The total r band light curve is well
fitted by power law with index of 0.87 +- 0.03 between 0.32 h and 7.63 h
post burst. This decline is consistent with the Faulkes Telescope South
detection (Guidorzi & Steele, GCN #8064) at 14.235 h post burst.
Assuming the optical light curve continues the decline with the same
power law index, we predict r' band magnitudes of 22.7 at 2 days and
23.4 at 4 days post burst.
The broad band SED from g' to K can be fitted by a power law with index
0.8 +- 0.1 (statistical) +-0.1 (systematic), where the latter is due to
the lack of photometric calibration.