GRB 080506
GCN Circular 7685
Subject
GRB 080506: Swift detection of a burst with optical afterglow
Date
2008-05-06T18:06:27Z (17 years ago)
From
Wayne Baumgartner at GSFC <wayne@milkyway.gsfc.nasa.gov>
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
M. M. Chester (PSU), G. Cusumano (INAF-IASFPA),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
C. Guidorzi (INAF-OAB), S. T. Holland (CRESST/USRA/GSFC),
S. Immler (CRESST/GSFC/UMD), J. A. Kennea (PSU),
V. La Parola (INAF-IASFPA), V. Mangano (INAF-IASFPA),
F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),
C. Pagani (PSU), P. Romano (INAF-IASFPA), T. Sakamoto (NASA/UMBC),
M. Stamatikos (NASA/ORAU), T. N. Ukwatta (GSFC/GWU) and
H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:
At 17:46:21 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080506 (trigger=311159). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 329.435, +39.002 which is
RA(J2000) = 21h 57m 44s
Dec(J2000) = +39d 00' 08"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). As this is an image trigger, the BAT light curve does
not show meaningful emission from the burst.
The XRT began observing the field at 17:48:41.3 UT, 140.1 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 329.42145, 38.98413 which
is equivalent to:
RA(J2000) = 21h 57m 41.15s
Dec(J2000) = +38d 59' 02.9"
with an uncertainty of 3.3 arcseconds (radius, 90% containment). This
location is 74 arcseconds from the BAT onboard position, within the BAT
error circle. The XRT light curve from TDRSS data is fading.
A power-law fit to a spectrum formed from promptly downlinked event
data does not constrain the column density, so we cannot provide limits
on the redshift using spectroscopy and the relation from Grupe et al.
(2007). A summary of the promptly downlinked data is given at
http://www.swift.ac.uk/sper/311159/.
The initial flux in the 2.5 s image was 5.50e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 400 seconds with the V filter starting
143 seconds after the BAT trigger. There is a candidate afterglow in the
rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 21:57:41.83 = 329.4243
DEC(J2000) = +38:59:06.4 = 38.9851
with a 1-sigma error radius of about 0.5 arc sec. This position is 8.0 arc sec.
from the center of the XRT error circle. The estimated magnitude is 18.3 with a
1-sigma error of about 0.5 mag. No correction has been made for the expected
extinction of about 0.8 magnitudes.
Burst Advocate for this burst is W. H. Baumgartner (wayne AT milkyway.gsfc.nasa.gov).
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 7686
Subject
GRB 080506: Optical observation with KANATA/TRISPEC
Date
2008-05-06T20:56:40Z (17 years ago)
From
Koji Kawabata at HASC,Hiroshima U <kawabtkj@hiroshima-u.ac.jp>
K. S. Kawabata, M. Sasada, M. Uemura, T. Yamashita and T. Ohsugi
(Hiroshima Univ.) and R. G. Lundock (Tohoku Univ.) report on behalf
of KANATA/TRISPEC observation team:
We performed a series of simultaneous optical(Rc) and NIR (J, Ks)
imaging observations for the optical counterpart associated with
GRB 080506 (Baumgartner et al, GCN 7685) using TRISPEC attached to
the 1.5-m KANATA telescope. Our quick-look analysis showed that Rc
magnitude of the counterpart was 17.5 at 220 sec after the BAT
trigger. It then faded and reached 19.5 at ~5050 sec. We used USNO
A2.0 1275-16800533 (R=15.1) and 1275-16801542 (R=15.1) stars for
comparison. Further analysis is ongoing.
GCN Circular 7687
Subject
GRB 080506: Enhanced Swift-XRT position
Date
2008-05-07T03:31:53Z (17 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester)
report on behalf of the Swift-XRT team.
Using 221 s of overlapping XRT Photon Counting mode and UVOT
data for GRB 080506, 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 = 329.42431, +38.98470 which is equivalent
to:
RA (J2000): 21h 57m 41.83s
Dec (J2000): +38d 59' 04.9"
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 7688
Subject
GRB 080506: TLS afterglow detection in VRIZ
Date
2008-05-07T04:02:27Z (17 years ago)
From
Alexander Kann at TLS Tautenburg <kann@tls-tautenburg.de>
D. A. Kann, C. Hoegner and S. Ertel (TLS Tautenburg) report:
We observed the afterglow of Swift GRB 080506 (Baumgartner et al., GCN
7685, Kawabata et al., GCN 7686) with the Tautenburg 1.34m Schmidt
telescope 0.32 days after the GRB in good conditions (moderate
transparency but excellent seeing). We obtained a total of six 600 sec
exposures, in the sequence Rc, V, Ic, Z, Z, Z before twilight forced us to
shut down. The afterglow is well (Rc, V, Ic) and faintly (Z) detected in
single images, and well detected in the 1800 sec stack of the three Z
images.
We find an afterglow position
R.A. (J2000) = 21:57:41.775
Dec. (J2000) = +38:59:05.86
in comparison with the USNOB1.0 catalog, with a precision of 0".5 in each
coordinate. This is fully in agreement with the UVOT (Baumgartner et al.,
GCN 7685) and enhanced XRT (Osborne et al., GCN 7687) positions.
Assuming the star at
R.A. (J2000) = 21:57:39.84
Dec. (J2000) = +38:58:28.25
to have Rc = 16.7 (magnitude is basically identical in R1 and R2
magnitudes), we find for the afterglow:
time Rc dRc
0.31576 20.77 0.13
Taking the two measurements from Kawabata et al. (GCN 7686), we find a
shallow decay slope of alpha = 0.6 between 0.0025 and 0.316 days after the
GRB.
Our (and Swift's) clear detection in the V band implies z <~ 4. On the
other hand, this was an image trigger, with faint emission seen up to ~
200 seconds. The initial XRT light curve (XRT repository, Evans et al.
2007) is flat until 200 seconds before dropping off very steeply. This may
suggest that this GRB lies at moderately high redshift (3 - 4).
Spectroscopy is encouraged.
This message may be cited.
GCN Circular 7689
Subject
GRB 080506: optical observation from Ondrejov
Date
2008-05-07T05:09:29Z (17 years ago)
From
Matus Kocka at Monteboo Obs,Masaryk U,Brno <koci@astronom.sk>
M. Kocka, M. Nekola, J. Strobl, R. Hudec, C. Polasek (AsU AV CR, Ondrejov),
M. Jelinek, P. Kubanek (IAA CSIC, Granada),
F. Munz (IASF/INAF, Bologna) A. de Ugarte Postigo (ESO) report
We observed the OT of the GRB080506 (Baumgartner et al,
GCN 7685) with the 0.5m telescope at ASU Ondrejov in
Czech Republic. We obtained a set of R-band exposures
at ~7.1h after the GRB.
Using the same calibration as Kawabata et al. (GCN 7686) we find the
brightness R ~ 21.2+-0.4.
This message may be cited.
GCN Circular 7690
Subject
GRB 080506: Observations from NOT
Date
2008-05-07T05:51:42Z (17 years ago)
From
Antonio Deugarte at IAA-CSIC <deugarte@iaa.es>
A. de Ugarte Postigo (ESO), C. C. Thoene,
J. P. U. Fynbo (DARK/NBI), E. Leitet (Uppsala Univ.) and
L. M. Trinchant (Stockholm Univ.) report on behalf of a
larger collaboration:
We have observed the field of GRB 080506 (Baumgartner
et al., GCN 7685) using the 2.5m NOT telescope (+ALFOSC)
at Roque de Los Muchachos Observatory, in La Palma (Spain)
using U, B and R filters. A 300s R-band observation with
mid exposure time 7.1518 May 2008 UT (9.87hr after the burst)
reveals the object at a magnitude of 21.05 � 0.11, using the
reference stars given in GCN 7686 for calibration. Combining
this datapoint with those of Kawabata et al. (GCN 7686),
Kann et al. (GCN 7688) and Kocka et al. (GCN 7689, where
it should say R= 20.2+/-0.4, private communication) we measure
a decay rate of alpha = 0.64 � 0.02 (f~t^-alpha), consistent with
the value reported by Kann et al. The object is clearly detected in
all filters, including the U-band frame, implying a redshift < 3.
GCN Circular 7692
Subject
GRB 080506, Swift-BAT refined analysis
Date
2008-05-07T14:23:57Z (17 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
K. McLean (GSFC/UMD), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+903 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 080506 (trigger #311159)
(Baumgartner, et al., GCN Circ. 7685). The BAT ground-calculated position is
RA, Dec = 329.467, 38.961 deg, which is
RA(J2000) = 21h 57m 52.1s
Dec(J2000) = +38d 57' 40.0"
with an uncertainty of 2.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 60%.
The mask-weighted light curve shows two episodes of emission, the first
starting at ~T+20 sec, peaking at ~T+40 sec, and returning to background
at ~T+90 sec. The second episode starts at ~T+100 sec, peaks at ~T+150 sec,
and ends at ~T+200 sec. T90 (15-350 keV) is 150 +- 20 sec
(estimated error including systematics).
The time-averaged spectrum from T+25.8 to T+188.8 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.87 +- 0.19. The fluence in the 15-150 keV band is 1.3 +- 0.2 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+134.48 sec in the 15-150 keV band
is 0.4 +- 0.1 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/311159/BA/
This burst satisfies Sakamoto/Ukwatta Swift-BAT possible high-z criteria
(Ukwatta et al. arXiv:0802.3815):
1) PL photon index = 1.87 (PL photon index < 2)
2) 1-s peak photon flux = 0.4 (1-s peak photon flux < 1.0 ph/cm2/s)
3) Light curve variance = 6.2x10-6 (Variance < 0.0001)
4) T90/(Peak photon flux) = 403 (T90/(Peak photon flux) > 100)
Based on a limited sample of bursts, these criteria yield
an 85% chance it has a redshift greater than 3.5.
GCN Circular 7693
Subject
GRB080506: Swift/UVOT observations
Date
2008-05-07T16:22:15Z (17 years ago)
From
Samantha Oates at MSSL <sro@mssl.ucl.ac.uk>
S.R. Oates (MSSL/UCL) and W. Baumgartner (NASA/GSFC) report on behalf of
the Swift/UVOT team
The Swift/UVOT began settled observations of the field of GRB 080506, 143s
after the BAT trigger (Baumgartner et al., GCN 7685). We detect the
afterglow in the v and b filters at the position:
RA(J2000.0) = 21:57:41.84
DEC(J2000.0) = +38:59:06.1
with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence).
This position is consistent with the UVOT enhanced XRT position (Osborne
et al., GCN 7687) and the TLS position (Kann et al., GCN 7688).
No observations were performed with the white filter due to the presence
of 7.5mag B star (HD 208837) 6 arcmins from the GRB position.
UVOT magnitudes and 3 sigma upper limits are reported below for the single
and coadded images:
Filter Tstart(s) Tstop Expo(s) Magnitude/3sigUL
-----------------------------------------------------
v 143 543 393 18.35 +/- 0.10
v 6728 6928 197 19.88 +/- 0.52
b 623 771 19 19.84 +/- 0.65 (1.7-sigma)
b 10818 11118 295 20.64 +/- 0.28 (3.8-sigma)
u 599 6311 254 > 20.29
w1 574 7338 471 > 20.44
m2 1284 7133 787 > 20.69
w2 639 6723 432 > 20.46
-----------------------------------------------------
These magnitudes are not corrected for the Galactic extinction
corresponding to a reddening of E{B-V} = 0.23 mag (Schlegel et al.
1998). The photometry is on the UVOT flight system described in Poole
et al. (2008,MNRAS,383,627).
GCN Circular 7694
Subject
GRB 080506: Swift XRT refined analysis
Date
2008-05-07T17:49:36Z (17 years ago)
From
Boris Sbarufatti at INAF-IASF-Pa <sbarufatti@ifc.inaf.it>
B. Sbarufatti, V. Mangano, V. La Parola (INAF-IASF PA) and
W. H. Baumgartner (GSFC/UMBC)
The Swift-XRT began observing GRB 080506 (trigger=311159, Baumgartner
et al., GCN Circ. 7685) in Window Timing mode, 146 s after the BAT
trigger. The enhanced XRT position was given in Osborne et al.
(GCN Circ. 7687).
The lightcurve is quite complex. It shows two initial bright flares
centered at 182+/-2 s and 254+/-2 s, with folding times of 22+/-1 s
and 88+/-2 s, respectively. Flaring activity is detected until times
> T+10 ks. The decay slope after 10 ks from the trigger time is
-0.6+/-0.2.
The spectrum of the first flare can be fit by a power-law model, with
a photon index of 1.46 � 0.06 and column density consistent with the
average Galactic column density in this direction of 1.66e21 cm-2
(Kalberla et al 2005). The observed (unabsorbed) 0.3-10 keV flux is
1.5e-9 (1.8e-9) erg cm-2 s-1.
The spectrum of the second flare can be fit by a power-law model, with
a photon index of 2.3 � 0.1 and column density consistent with the
average Galactic column density in this direction. The observed
(unabsorbed) 0.3-10 keV flux is 3.2e-10 (5.2e-9) erg cm-2 s-1.
The PC mode spectrum, covering times > T+1000 s, is fit by a power
law model with photon index 2.0 � 0.2 and no evidence for any
additional column density with respect to the Galactic one.
The corresponding observed (unabsorbed) 0.3-10 keV fluxes are
2.3e-12 (3.5e-12 ) erg cm-2 s-1, respectively.
If the burst continues to decay at the same rate, we predict an XRT
count rate of 9.8 e-3 counts/s and 6.4 e-3 counts/s at T+24 hours
and T+48 hours, respectively. This corresponds to observed 0.3-10
keV fluxes of approximately 5.4e-13 and 3.6e-13 erg cm-2 s-1.
This circular is an official product of the Swift-XRT team.
GCN Circular 7696
Subject
GRB 080506: TLS 2nd Epoch - possible light curve break
Date
2008-05-08T03:18:02Z (17 years ago)
From
Alexander Kann at TLS Tautenburg <kann@tls-tautenburg.de>
D. A. Kann, C. Hoegner, and S. Ertel (TLS Tautenburg) report:
We observed the afterglow of Swift GRB 080506 (Baumgartner et al., GCN
7685) with the Tautenburg 1.34m Schmidt telescope 1.33 days after the GRB,
again in good conditions. We obtained a four 300 sec exposures in the Rc
band before twilight shut us down. The afterglow is faintly detected in
the stacked image.
Using the same comparison star as Kann et al. (GCN 7688), we find:
time (days) Rc dRc
1.3346 22.23 0.33
An extrapolation of the decay in the first 0.4 days (~0.63, Kann et al.,
GCN 7688, de Ugarte Postigo et al., GCN 7690) yields an expected magnitude
of Rc ~ 21.8 at 1.33 days after the GRB. Our measured value lies below the
extrapolation, indicating a break (possibly a jet break) may have occured.
We caution that the detection is rather marginal and the high sky
background may falsify the measurement.
This message may be cited.
GCN Circular 7698
Subject
GRB 080506: VLA radio upper limit
Date
2008-05-08T17:28:11Z (17 years ago)
From
Poonam Chandra at U Virginia/NRAO <pc8s@virginia.edu>
Poonam Chandra (NRAO/UVA) and Dale A. Frail (NRAO) report on behalf
of the Caltech-NRAO-Carnegie GRB Collaboration:
"We used the Very Large Array to observe the field of view toward GRB
080506 (GCN 7685) at a frequency of 8.46 GHz at 2008 May 8.53 UT.
We do not detect the GRB afterglow at Swift-XRT position (GCN 7687).
The flux density at the afterglow position is -40 +/- 40 uJy.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."
GCN Circular 7700
Subject
GRB 080506:Optical observations from HCT
Date
2008-05-08T19:41:11Z (17 years ago)
From
T.P. Prabhu at Indian Astro. Obs. <tpp@crest.ernet.in>
D.K. Sahu, G.C. Anupama (IIA, Bangalore), Kuntal Misra (ARIES) report.
The field of GRB 080506 (Baumgartner et al., GCN 7685) was observed using
HFOSC mounted on the 2-m Himalayan Chandra Telescope, Indian Astronomical
Observatory, India. A series of 300sec exposures were taken in R-band
between 20:45 UT and 23:00 UT on 06/05/2008. The optical counter part is
detected in all our frames. Using the calibration by Kawabata et al. (GCN
7686), the estimated R band magnitude of the optical counter part is
20.13+/-0.1 mag at 20:47UT. The optical counter part faded by ~ 0.6
magnitude during our observations.
This message may be cited.
GCN Circular 7709
Subject
GRB 080506: NAYUTA Optical Observation
Date
2008-05-12T14:19:21Z (17 years ago)
From
Ryo Iizuka at NHAO <iizuka@nhao.go.jp>
S. Maeno, H. Naito, S. Narusawa and R. Iizuka report on behalf of NHAO.
We observed the field of GRB 080506 (GCN 7685) with MINT on the
2.0-m NAYUTA telescope at Nishi-Harima Astronomical Observatory,
Japan. We detected the optical afterglow in R-band on 2008 May 6
17:58:02 UT (701 seconds after the BAT trigger).
The magnitudes relative to the USNO B1.0 catalog are below.
Start(UT) exp(sec) R-mag R-err
--------------------------------------------
02:58:02 150 18.23 0.11
03:03:51 240 18.22 0.12
03:14:22 300 18.51 0.13
03:32:29 300 18.95 0.13
03:53:52 450 19.26 0.13
04:10:55 450 19.64 0.21
--------------------------------------------