GRB 100621A
GCN Circular 10870
Subject
GRB 100621A: Swift detection of a burst
Date
2010-06-21T03:16:45Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
T. N. Ukwatta (GSFC/GWU), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), V. D'Elia (ASDC),
N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU),
S. T. Holland (CRESST/USRA/GSFC), C. B. Markwardt (CRESST/GSFC/UMD),
M. H. Siegel (PSU), M. Stamatikos (OSU/NASA/GSFC), M. A. Stark (PSU)
and G. Stratta (ASDC) report on behalf of the Swift Team:
At 03:03:32 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100621A (trigger=425151). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 315.308, -51.086 which is
RA(J2000) = 21h 01m 14s
Dec(J2000) = -51d 05' 10"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a triple-peaked
structure with a duration of about 100 sec. The peak count rate
was ~25,000 counts/sec (15-350 keV), at ~25 sec after the trigger.
The XRT began observing the field at 03:04:48.8 UT, 76.0 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 315.3004, -51.1063 which is equivalent to:
RA(J2000) = 21h 01m 12.09s
Dec(J2000) = -51d 06' 22.6"
with an uncertainty of 5.0 arcseconds (radius, 90% containment). This
location is 73 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy.
The initial flux in the 0.1 s image was 7.49e-08 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 84 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag.
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.03.
Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.com).
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 10871
Subject
GRB 100621A: ROTSE-III Optical Limits
Date
2010-06-21T03:40:05Z (15 years ago)
From
Shashi Bhushan Pandey at ROTSE <shaship@umich.edu>
S. B. Pandey (U Mich), W. Rujopakarn (Steward), T. Guver (U Arizona), W.
Zheng (U Mich), report on behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded to GRB 100621A (Swift trigger 425151; Ukwatta T. N., GCN 10870),
producing images beginning 5.0 s after the GCN notice time. An automated
response took the first image at 03:04:05.0 UT, 32.2 s after the burst, and
during the gamma-ray emission, under fair conditions. We took 10 5-sec, 10
20-sec and 10 60-sec exposures. These unfiltered images are calibrated
relative to USNO A2.0 (R). Imaging is on going.
Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma Swift/BAT error circle or the XRT error circle; the field is not
crowded. Individual images have limiting magnitudes ranging from 16.1-17.3;
we set the following specific limits.
start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd?
--------------------------------------------------------------------
03:04:05.0 03:04:10.0 5 16.1 32.2 N
03:05:30.0 03:09:13.0 200 18.4 232.2 Y
GCN Circular 10872
Subject
GRB 100621A: Prompt enhanced Swift-XRT position
Date
2010-06-21T03:56:48Z (15 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Using 0 s of promptly downlinked XRT event data for GRB 100621A, we
find an enhanced XRT position of the afterglow: RA, Dec: 315.3052,
-51.1060 which is equivalent to:
RA (J2000) = 21 01 13.24
Dec (J2000) = -51 06 21.7
with an uncertainty of 2.0 arc sec (radius, 90% confidence). Analysis
of the promptly available data is online at
http://www.swift.ac.uk/sper/425151.
Position enhancement is is described by Goad et al. (2007, A&A, 476,
1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular is an official product of the Swift-XRT team.
GCN Circular 10873
Subject
GRB 100621A: Enhanced Swift-XRT position
Date
2010-06-21T09:33:26Z (15 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester)
report on behalf of the Swift-XRT team.
Using 3262 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 100621A, 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 = 315.30466, -51.10624 which is equivalent
to:
RA (J2000): 21h 01m 13.12s
Dec (J2000): -51d 06' 22.5"
with an uncertainty of 1.7 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) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 10874
Subject
GRB 100621A: GROND observation of bright NIR afterglow
Date
2010-06-21T09:56:56Z (15 years ago)
From
Jochen Greiner at MPI <jcg@mpe.mpg.de>
Adria Updike (Clemson Univ.), Ana Nicuesa (Tautenburg Obs.), Marco Nardini,
Thomas Kruehler and Jochen Greiner (all MPE Garching) report on behalf of
the GROND team:
We observed the field of GRB 100621A (Swift trigger 425151; Ukwatta et
al., GCN #10870) simultaneously in g'r'i'z'JHK with GROND (Greiner et
al. 2008, PASP 120, 405) mounted at the 2.2 m MPI/ESO telescope at La
Silla Observatory (Chile). Observations started at 03:07 UT on June 21st,
4 minutes after the GRB trigger, and continued for 3 hours. They were
performed at an average seeing of 1.5" under clear sky conditions.
In stacked images of 6 min total integration time in g'r'i'z' and 8 min in JHK,
centered at 03:20 UT, we detect a bright, uncatalogued NIR source within the
Swift/XRT error circle (Evans et al. GCN #10872) at the following coordinates:
RA (2000.0) = 21h 01m 13.08s
DEC (2000.0) = -51d 06' 22.5"
with an error of +-0.3". This coincides with the enhanced XRT position
(Evans et al. 2010, GCN #10873).
In the first hour the source faded by about 1 mag in the JHK bands,
thus we identify this object as the GRB afterglow of GRB 100621A.
Our preliminary photometry centered at 03:45 UT is (in AB
magnitudes):
g' = 22.7+-0.4
r' = 21.6+-0.1
i' = 20.5+-0.1
z' = 19.7+-0.1
J = 17.3+-0.1
H = 16.3+-0.1, and
K = 15.8+-0.1
These magnitudes were derived by calibrating the images against the GROND
zeropoints and 2MASS field stars and are not corrected for the Galactic
foreground extinction corresponding to a reddening of E_(B-V)= 0.03 in the
direction of the burst (Schlegel et al. 1998).
We note that there are indications of this source in the DSS2 images.
Also, there is no fading in the g' band, suggesting that this is the
underlying host galaxy at a redshift smaller than about 3. The extremely
red colour then is likely due to severe intrinsic dust extinction.
We encourage spectroscopic observations.
GCN Circular 10875
Subject
GRB 100621A: Swift-BAT refined analysis
Date
2010-06-21T13:10:27Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
T. N. Ukwatta (GWU) S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC),
(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 100621A (trigger #425151)
(Ukwatta, et al., GCN Circ. 10870). The BAT ground-calculated position is
RA, Dec = 315.309, -51.102 deg, which is
RA(J2000) = 21h 01m 14.1s
Dec(J2000) = -51d 06' 08.8"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 97%.
The mask-weighted light curve shows three main overlapping peaks starting
at ~T-8 sec, with the main peak at ~T+25 sec, and ending at ~T+220 sec.
T90 (15-350 keV) is 63.6 +- 1.7 sec (estimated error including systematics).
The time-averaged spectrum from T-6 to T+204 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.90 +- 0.03. The fluence in the 15-150 keV band is 2.1 +- 0.0 x 10^-5 erg/cm2.
The 1-sec peak photon flux measured from T+24.46 sec in the 15-150 keV band
is 12.8 +- 0.3 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/425151/BA/
GCN Circular 10876
Subject
GRB 100621A: VLT/X-shooter redshift
Date
2010-06-21T14:00:38Z (15 years ago)
From
Bo Milvang-Jensen at Dark Cosmology Centre,NBI,U. Copenhagen <milvang@astro.ku.dk>
B. Milvang-Jensen (DARK/NBI), P. Goldoni (APC/Univ. Paris 7 and SAp/CEA),
N. R. Tanvir, K. Wiersema (Univ. Leicester), D. Malesani (DARK/NBI),
A. de Ugarte Postigo (INAF-OAB), V. D'Elia (INAF-OAR and ASDC),
S. D. Vergani (GEPI/Obs. Paris and APC/Univ. Paris 7),
J. P. U. Fynbo (DARK/NBI), L. Kaper (Univ. Amsterdam),
J. Sollerman (Univ. Stockholm), on behalf of the X-shooter GRB
collaboration, and
A. Updike (Clemson Univ.), J. Greiner, T. Kruehler (MPE Garching),
on behalf of the GROND team, report:
We observed the optical afterglow of GRB 100621A (Ukwatta et al., GCN
10870; Updike et al., GCN 10874) with the ESO VLT equipped with the
X-shooter spectrograph. The afterglow was detected in the I-band
acquisition image. Four spectra lasting 10 minutes each were obtained,
covering the spectral range 3000-25000 AA, starting on 2010 June 21,
at 10:09 UT (7.1 hr after the GRB); the observations were done during
twilight. Preliminary inspection of the spectrum reveals emission
features which we interpret as due to [O II] 3727, Hbeta and the
[O III] doublet from the underlying host galaxy, at a common redshift
z = 0.542. The [O II] line is very weak. This, together with the low
redshift and the optically faint and red afterglow supports high
extinction internal to the host (Updike et al., GCN 10874).
We caution that the data reduction was carried out using archival
calibration files. We acknowledge a particularly helpful and attentive
support from the ESO staff in Paranal: M. Olivares, T. Rivinius,
C. Ledoux, C. Martayan, and the visiting astronomers: F. Ferraro,
B. Lanzoni.
GCN Circular 10877
Subject
GRB 100621A: Swift XRT refined analysis
Date
2010-06-21T14:10:13Z (15 years ago)
From
Giulia Stratta at ASDC <giulia.stratta@gmail.com>
G. Stratta (ASDC), V. D'Elia (ASDC) and T. N. Ukwatta (GSFC/GWU) report on
behalf of the Swift-XRT team:
We have analysed 3.6 ks of XRT data for GRB 100621A (Ukwatta et al. GCN
Circ. 10870), from 79 s to 7.0 ks after the BAT trigger. The data comprise
322 s in Windowed Timing (WT) mode with the remainder in Photon Counting
(PC) mode. The enhanced XRT position for this burst was given by Evans et
al. (GCN. Circ 10872).
The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=3.41 (+0.11, -0.18). At T+153 s the decay
steepens to an alpha of 4.34 (+0.20, -0.12) before breaking again at T+389 s
to a final decay with index alpha=0.55 (+0.13, -0.07).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.73 (+0.07, -0.06). The
best-fitting absorption column is 6.11 (+0.27, -0.26) x 10^21 cm^-2, in
excess of the Galactic value of 2.9 x 10^20 cm^-2 (Kalberla et al. 2005).
The PC mode spectrum has a photon index of 2.15 (+0.17, -0.16) and a
best-fitting absorption column of 6.6 (+1.0, -0.9) x 10^21 cm^-2. The counts
to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum is 5.0 x 10^-11 (1.0 x 10^-10) erg cm^-2 count^-1.
If the light curve continues to decay with a power-law decay index of 0.55,
the count rate at T+24 hours will be 0.23 count s^-1, corresponding to an
observed (unabsorbed) 0.3-10 keV flux of 1.1 x 10^-11 (2.4 x 10^-11) erg
cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00425151.
This circular is an official product of the Swift-XRT team.
GCN Circular 10878
Subject
GRB 100621A: Swift/UVOT observations
Date
2010-06-21T14:30:51Z (15 years ago)
From
Samantha Oates at MSSL <sro@mssl.ucl.ac.uk>
S. R. Oates (MSSL-UCL) and T. N. Ukwatta (GSFC/GWU) report on behalf
of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of
GRB 100621A 85s after the BAT trigger (Ukwatta et al., GCN 10870).
We detect a source at the enhanced Swift XRT position
(Evans et al. GCN 10873) and at the location of the GROND source
(Updike et al. GCN 10874). This source is also observed in the
DSS and observed to be constant during the first 7000s and is
thus likely to be the host galaxy, which is also suggested by Updike
et al. (GCN 10874).
The magnitudes and 3-sigma upper limits for the finding chart
exposures (FC)
and summed images for this possible host galaxy are:
Filter T_start T_stop Exp(s) Magnitude/3-sigma upper limit
-------------------------------------------------------------
white (FC) 85 234 147 20.87 +/- 0.35
white 576 7093 519 20.46 +/- 0.15
u (FC) 297 546 246 > 20.18
u 700 6683 360 > 20.14
v 626 6067 391 19.49 +/- 0.31
b 552 6888 372 20.27 +/- 0.28
uvw1 1107 6478 352 19.64 +/- 0.25
uvm2 6073 6273 197 > 19.66
uvw2 5663 5863 197 19.60 +/- 0.28
-------------------------------------------------------------
The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight of E_(B-V) = 0.03 mag.
All photometry is on the UVOT photometric system described in Poole et
al. (2008, MNRAS, 383, 627).
GCN Circular 10880
Subject
GRB 100621A MOA-II optical limit
Date
2010-06-22T01:04:15Z (15 years ago)
From
Takashi Sako at Nagoya U./MOA <sako@stelab.nagoya-u.ac.jp>
D. Suzuki, F. Hayashi, S.Kobara, T. Sako, H. Naito, K. Omori (STE Lab, Nagoya Univ.)
on behalf of the MOA Collaboration report:
We searched for an optical afterglow of GRB 100621A (GCN 10870, T. N. Ukwatta et al.)
starting from 09:02 UT on 2010 June 21st (6 hours after the burst) with the
MOA-II 1.8m telescope at Mt.John observatory in New Zealand.
In a single image of a 300sec exposure with a wide-band Red filter (center
wavelength ~ 750nm and FWHM ~ 250nm), we did not find any object
within the error circle of the Swift XRT source position (GCN 10873).
A 3 sigma upper limit is set in the I magnitude at 22.23 mag.
This photometry was done by using the DoPhot and calibrated against the
USNO-B1.0 catalog stars, and not corrected for the Galactic extinction.
GCN Circular 10881
Subject
GRB 100621A: IRSF/SIRIUS NIR Observation
Date
2010-06-22T15:37:21Z (15 years ago)
From
Hiroyuki Naito at Nagoya U <naito@stelab.nagoya-u.ac.jp>
H. Naito, T. Sako, D. Suzuki, S. Kobara and K. Omori (Nagoya Univ.) on
behalf of the MOA Collaboration,
T. Nagayama, M. Kurita (Nagoya Univ.) and N. Oi (The Graduate
University for Advanced Studies/NAOJ)
on behalf of the IRSF Collabration report:
We searched for a NIR afterglow of GRB 100621A (Ukwatta et al., GCN
10870) starting from
04:02 to 04:51 UT on 2010 June 21 with the SIRIUS on the IRSF 1.4m
telescope at SAAO in
South Africa. In images of a 300 sec exposure with J, H and Ks filter,
we detected an new source
within the error circle of the enhanced Swift XRT position (Evans et
al., GCN 10873) and at the
location of the GROND source (Updike et al., GCN 10874) . The
estimated magnitudes are the
followings.
---------------------------------------------------------------
Mid time from Total Exp. J-mag* H-mag* K-mag*
trigger (min) (s)
---------------------------------------------------------------
61.41 300 16.56 15.22 14.18
67.61 300 16.24 14.63 13.84
73.84 300 15.27 13.78 12.63
80.14 300 15.07 13.57 12.40
86.36 300 14.93 13.45 12.23
92.56 300 14.90 13.45 12.32
98.81 300 14.93 13.47 12.34
105.0 300 15.04 13.55 12.36
---------------------------------------------------------------
*Typical error is ~ 0.1 mag
This photometry was done by using the DoPhot and calibrated against
the 2MASS catalog stars,
and not corrected for the Galactic extinction. The source was
brightened up by >1mag during our
observation period while the other field stars were reasonably stable.
GCN Circular 10882
Subject
Konus-Wind observation of GRB 100621A
Date
2010-06-23T10:22:55Z (15 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin,
P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf
of the Konus-Wind team, report:
The long GRB 100621A (Swift-BAT trigger=425151;
Ukwatta et al., GCN 10870; Ukwatta et al., GCN 10875)
triggered Konus-Wind at T0=11013.352s UT (03:03:33.352)
The burst light curve shows multiple overlapping peaks
with a total duration of ~80 s.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB100621_T11013/
As observed by Konus-Wind the burst
had a fluence of 3.6(+/-0.4)x10-5 erg/cm2,
and a 256-ms peak flux measured from T0+26.880s
of 1.70(+/-0.13)x10-6 erg/cm2/s
(both in the 20 keV - 2 MeV energy range).
The time-integrated spectrum of the burst
(from T0 to T0+73.984 s) is best fit
in the 20 keV - 2 MeV range by the GRB (Band)
model, for which:
the low-energy photon index alpha = -1.70 (+/-0.13),
the high energy photon index beta = -2.45 ( <-2.3 ),
the peak energy Ep = 95(-13, +18)keV (chi2 = 65/57 dof).
The spectrum at the maximum count rate
(measured from T0+24.832 to T0+33.024 s) is best fit
in the 20 keV - 2 MeV range by the GRB (Band)
model, for which:
the low-energy photon index alpha = -1.15 (-0.2/+0.3),
the high energy photon index beta = -2.8 (-0.7/+0.3),
the peak energy Ep = 83(+/-9)keV (chi2 = 64/57 dof).
Assuming z=0.542 (Milvang-Jensen et al., GCN 10876) and
a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.27, Omega_Lambda = 0.73,
the isotropic energy release E_iso = 2.8(+/-0.3)x10^52 erg,
the peak luminosity (L_iso)_max = (2.04+/-0.16)x10^51 erg/s.
All the quoted results are preliminary.
All the quoted errors are at the 90% confidence level.