GRB 070621
GCN Circular 6560
Subject
GRB 070621: Swift detection of a burst
Date
2007-06-21T23:36:31Z (18 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
B. Sbarufatti (INAF-IASFPA), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), P. J. Brown (PSU),
M. M. Chester (PSU), C. Guidorzi (Univ Bicocca&INAF-OAB),
S. T. Holland (CRESST/GSFC/USRA), J. A. Kennea (PSU),
C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC),
C. Pagani (PSU), D. M. Palmer (LANL),
P. Romano (Univ. Bicocca & INAF-OAB), M. Stamatikos (NASA/ORAU) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:
At 23:17:39 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070621 (trigger=282808). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 323.804, -24.806 which is
RA(J2000) = 21h 35m 13s
Dec(J2000) = -24d 48' 20"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows multiple peaks
with a total duration of at least 40 sec. The peak count rate
was ~1500 counts/sec (15-350 keV), at ~8 sec after the trigger.
The XRT began observing the field at 23:19:30 UT, 111 seconds after
the BAT trigger. XRT found a bright and fading X-ray source located
at RA, Dec 323.7909, -24.8181 which is
RA(J2000) = 21h 35m 09.8s
Dec(J2000) = -24d 49' 05.1"
with an uncertainty of 4.7 arcseconds
(radius, 90% containment). This location is 61 arcseconds from the
BAT on-board position, within the BAT error circle. The initial flux
in the 2.5s image was 3.7e-09 erg/cm2/s (0.2-10 keV).
UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 120 seconds after the BAT trigger. No
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 3-sigma
upper limit is about 19.2 mag. The upper limit has not been corrected
for the expected Galactic extinction along the line of sight
corresponding to a reddening of E_{B-V} = 0.05 mag.
GCN Circular 6561
Subject
GRB 070621: ROTSE-III Prompt Optical Limits
Date
2007-06-21T23:46:58Z (18 years ago)
From
Eli Rykoff at U of Michigan/ROTSE <erykoff@umich.edu>
E.S. Rykoff (U Mich), W. Rujopakarn (Steward), B. E. Schaefer (Louisiana
State), H. Swan (U Mich), J. Aretakis (U Mich), R. Quimby (U Texas),
report on behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded to GRB 070621 (Swift trigger 282808, Sbarufatti, et al., GCN
6560), producing images beginning 6.1 s after the GCN notice time. An
automated response took the first image at 23:18:03.1 UT, 23.3 s after
the burst, and during gamma-ray emission. 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 ongoing.
Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma Swift/BAT error circle or the XRT error circle, for both single
images and coadding into sets of 10. Individual images have limiting
magnitudes ranging from 16.4-17.8; we set the following specific limits.
start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd?
--------------------------------------------------------------------
23:18:03.1 23:18:08.1 5 16.6 23.3 N
23:18:03.1 23:19:20.7 77 17.5 23.3 Y
23:19:28.5 23:24:16.3 287 18.5 108.7 Y
23:24:25.7 23:35:51.6 685 18.8 405.9 Y
GCN Circular 6562
Subject
GRB 070621: Watcher Observations
Date
2007-06-22T01:28:07Z (18 years ago)
From
John French at UCD,Ireland <jfrench@bermuda.ucd.ie>
John French (University College Dublin), Petr Kubanek (GACE Valencia),
Gary Melady (University College Dublin), Martin Jelinek (IAA CSIC Granada)
report on behalf of the Watcher collaboration:
The Watcher 40cm robotic telescope, located at Boyden Observatory,
South Africa, began imaging the field of GRB 070621
(Sbarufatti et al., GCN 6560) at 23:18:21 UT, 40s after the Swift trigger.
Our first 10s unfiltered image shows no new source in the XRT error circle
down to an R-band limiting magnitude of 16.1. Subsequent 10s exposures
were combined to create a 360s exposure with a mean time of 23:21:47
(247s after the trigger). No new source is detected in the XRT error
circle down to an R-band limiting magnitude of 17.9.
Observations are ongoing.
GCN Circular 6563
Subject
GRB 070621: TAROT Calern observatory optical observations
Date
2007-06-22T01:29:39Z (18 years ago)
From
Alain Klotz at CESR-CNRS <Alain.Klotz@free.fr>
Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report:
We imaged the field of GRB 070621 detected by SWIFT
(trigger 282808) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.
The observations started 23.5s after the GRB trigger
(6.4s after the notice). The elevation of the field increased from
from 3 degrees above horizon and weather conditions
were poor.
The date of trigger : t0 = 2007-06-21T23:17:39.840
The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect any OT at the XRT location
(Sbarufatti et al. GCNC 6560) with a limiting magnitude of:
t0+23.5s to t0+83.5s : R > 14.9
The second image is 30.0s exposure in tracking mode:
t0+90.3s to t0+120.3s : R > 15.4
Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.
This message may be cited.
GCN Circular 6564
Subject
GRB070621: OPTIMA-Burst optical upper limit
Date
2007-06-22T02:41:36Z (18 years ago)
From
Alexander Stefanescu at MPE <astefan@mpe.mpg.de>
A. Stefanescu (1), Z. Ioannou (2)(4), G. Kanbach (1), S. Duscha (1), F.
Schrey (1), A. Slowikowska (2)(3), H. Steinle (1)
((1)=MPE Garching, (2)=FORTH, Heraklion (3)=NCAC, Torun, (4)=Univ. of
Crete) of the OPTIMA-Burst Team report the following:
OPTIMA-Burst at the 1.3m Skinakas Observatory, of the University of
Crete, Greece observed the Swift XRT error circle of GRB 070621 (GCN
Circ 6560, B. Sbarufatti et al.). Observations started at 23:54:52 UT
(2233s after the trigger) at an airmass of 2.5.
We see no source at the XRT error circle, neither in single exposures,
nor in stacked exposures. Data of the exposures are:
t-t_0 (mid exp) t_exp R-limit
2263s 60s 20.0 (first exposure)
3271s 1680s 20.9 (stack of all avail. exposures)
GCN Circular 6565
Subject
GRB 070621: NOT observations
Date
2007-06-22T06:33:01Z (18 years ago)
From
Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center <malesani@astro.ku.dk>
D. Malesani, C.C. Thoene, J.P.U. Fynbo (DARK/NBI), N.R. Tanvir (Univ.
Leicester), A. Tziamtzis (NOT), report on behalf of a larger collaboration:
We observed the field of GRB 070621 (Sbarufatti et al., GCN 6530) with
the NOT equipped with ALFOSC. Observations were carried out in the R and
I bands, for a total of 15 min per filter, at mean times 22.17 and
22.184 UT (4.84 and 5.12 hr after the GRB, respectively).
At the edge of the XRT error circle, there is an object at the
coordinates (J2000, 0.5" uncertainty):
RA = 21:35:10.07
Dec = -24:49:07.7
with R~22.3 calibrated with respect to the USNO-B1 star 0651-0871887. It
might be extended, although the low S/N does not allow firm statements.
No other objects are detected inside the XRT error circle down to R~23.4
and I~22.5.
GCN Circular 6567
Subject
GRB 070621: UVOT-enhanced XRT position
Date
2007-06-22T08:56:15Z (18 years ago)
From
Boris Sbarufatti at INAF-IASF-Pa <sbarufatti@ifc.inaf.it>
B. Sbarufatti (INAF-IASF Pa), P. A. Evans (LU) report on behalf of
the Swift team
Using 746 s of overlapping XRT Photon Counting mode and UVOT V-band
data, 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 =
323.79225, -24.81752 which is equivalent to:
RA (J2000): 21 35 10.10
Dec (J2000): -24 49 03.1
with an uncertainty of 2.0 arcsec (90% confidence).
GCN Circular 6568
Subject
GRB 070621: Gemini South optical imaging
Date
2007-06-22T11:27:19Z (18 years ago)
From
Daniel Perley at U.C. Berkeley <dperley@astro.berkeley.edu>
J. S. Bloom (UC Berkeley), H.-W. Chen (U Chicago), D. A. Perley (UC
Berkeley), and L. Pollack (UC Santa Cruz) report:
"The receipt of the BAT_POSITION notice for GRB 070621 (Sbarufatti et
al. GCN #6560) triggered our automated imaging program on Gemini South
at 23:18:26 UT and the first images were obtained at 22 June 2007
04:54:57 UT by Byran Miller and the Gemini staff once the conditions
cleared. Images in griz-bands were obtained, with a total of 5x180
second exposures in each band.
A number of faint sources are detected near the UVOT-enhanced XRT
position (Sbarufatti et al., GCN #6567), including the source (s1 =
21:35:10.14, -24:49:06.9) to the South of the XRT position which may be
the same source noted by Malesani et al. (GCN #6565). There is an
apparent galaxy (s4: 21:35:10.34, -24:49:02.2, PA ~ -45 deg) to the east
of the GRB but outside the current XRT position. A color image of the
field has been posted (*) along with a ds9 region file (**) giving the
J2000 locations of the sources near the GRB.
We note the presence of an asteroid, not found in the Minor Planet
Checker (***), moving near the GRB at the time of the Gemini
observations. The quickly derived parameters for this asteroid are:
apparent motion: 10.4 S "/hr, 4.69 W "/hr
position (ecliptic): lambda = +318:07:27.207, beta = -09:53:28.791 @
22 June 2007 05:22:37.4 UTC
(*) http://lyra.berkeley.edu/~jbloom/grb070621-gemini.png
(**) http://lyra.berkeley.edu/~jbloom/grb070621-gemini.reg
(***) http://scully.harvard.edu/~cgi/CheckSN
We thank Bryan Miller and the Gemini Staff for observing this ToO."
GCN Circular 6569
Subject
GRB070621: Swift XRT refined analysis
Date
2007-06-22T11:31:25Z (18 years ago)
From
Boris Sbarufatti at INAF-IASF-Pa <sbarufatti@ifc.inaf.it>
B. Sbarufatti (INAF-IASFPA), P. Romano, C. Guidorzi (Univ. Bicocca &
INAF-OAB)
A. Moretti (INAF-OAB) report, on behalf of the Swift-XRT team
We have analysed the first three orbits of Swift XRT data for GRB070621
(Sbarufatti et al., GCN Circ. 6560), consisting of 150 s in Window
Timing
mode data and 1.3 ks in Photon Counting mode.
The UVOT enhanced XRT position (Sbarufatti et al., GCN Circ. 6567) is
RA, Dec = 323.79225, -24.81752 which is equivalent to:
RA (J2000): 21 35 10.14
Dec (J2000): -24 49 03.1
with an uncertainty of 2.0 arcsec (90% confidence).
The X-ray light curve exhibits an initial steep decay (index -3.8
+/-0.1)
up to T+380 s. A flare is observed around T+150s. After the break, the
count-rate decays with a power-law index of -0.91 +/- 0.04. If the
present
slow decay continues, the predicted count rate 24h after the trigger is
2.1E-2 counts/s, corresponding to a flux of 1.8E-12 ergs cm^-2 s^-1.
The WT and PC spectra can be fitted simultaneously with an absorbed
power-law model with a photon index 2.5+/-0.3 and a column density
(4.4 +/- 0.9)E21 cm^-2, significantly in excess with respect to the
galactic value (3.5E20 cm^-2, Dickey & Lockman, 1990). The absorbed
(unabsorbed) fluxes are 8.4E-10 (2.2E-09) ergs cm^-2 s^-1 for
the WT spectrum and 1.4E-11 (3.6E-11) ergs cm^-2 s^-1 for
the PC spectrum.
This circular is an official product of the XRT team.
GCN Circular 6570
Subject
WHT observations of GRB070621
Date
2007-06-22T12:33:06Z (18 years ago)
From
Evert Rol at U.Leicester <er45@star.le.ac.uk>
N. Tanvir, E. Rol (University of Leicester) and A. Cardwell (ING), report
on behalf of a larger collaboration:
We observed the position of GRB070621 (Sbarufatti, GCNC 6560) with the
Auxiliary Port Instrument on the William Herschel Telescope at La
Palma, for 25 minutes starting at 4:14 UT, June 22 (average time 5.17
hours after burst).
We detect the extended object mentioned by Malesani et al. (GCNC
6565), at a magnitude of I = 21.21 +/- 0.05.
We also detect the source on the east edge of the refined XRT error
circle (Sbarufatti, GCNC 6569) mentioned by Bloom et al (GCNC 6568),
with a magnitude of I = 22.5 +/- 0.1.
Photometry was performed relative to the USNO star 0651-0871887, which
has an I2 magnitude of 17.21.
GCN Circular 6571
Subject
GRB 070621: Swift-BAT refined analysis
Date
2007-06-22T13:52:28Z (18 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
E. Fenimore (LANL), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), B. Sbarufatti (INAF-IASFPA),
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 070621 (trigger #282808)
(Sbarufatti, et al., GCN Circ. 6560). The BAT ground-calculated position is
RA, Dec = 323.806, -24.809 deg which is
RA(J2000) = 21h 35m 13.5s
Dec(J2000) = -24d 48' 32"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 31%.
The mask-weighted light curve shows several overlapping peaks starting at ~T-20 sec
and ending at ~T+40 sec. There is a low-significance bump (~3 sigma) from
T+70 to T+105 sec. T90 (15-350 keV) is 33.3 +- 1.0 sec (estimated error
including systematics).
The time-averaged spectrum from T-5.2 to T+36.4 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.57 +- 0.06. The fluence in the 15-150 keV band is 4.3 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+21.56 sec in the 15-150 keV band
is 2.5 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
GCN Circular 6572
Subject
Keck Laser Guide Star Adaptive Optics Imaging of GRB 070621
Date
2007-06-22T17:01:48Z (18 years ago)
From
Josh Bloom at UC Berkeley <jbloom@astron.berkeley.edu>
J. S. Bloom (UC Berkeley), L. Pollack (UC Santa Cruz), D. A. Perley
(UC Berkeley) report:
"We observed the field of GRB 070621 (GCN #6560) in the K-prime
filter using
the Laser Guide Star (LGS) Adaptive Optics (AO) system + NIRC2 on the
Keck II telescope. With integrations of 60 sec per frame, we stacked
45 frames with a mean time since GRB trigger of 13.8 hr. The brighter
compact sources in the field have typical FWHM of 130 mas, and the
preliminary 5 sigma detection threshold is K-prime = 21.5 mag. With
further refinements we expect this limit to improve.
A number of sources mentioned in previous circulars are detected (*)
as well as a few red and faint sources near the XRT position. In
particular, we note source l1 (ra=21:35:10.22, dec=-24:49:07.4, J2000)
which is 0.8 arcseconds East of apparent galaxy s1 (Bloom et al. GCN
#6568 = Malesani et al. source #1 GCN #6565?). The source near the
Eastern edge of the XRT position (l2) is nearly coincident with the
position of s4 (Bloom et al. GCN #6568 = Tanvir et al. source #2 GCN
#6570) but appears only marginally extended at K-prime. Both l1 (being
quite red and close to a galaxy) and l2 (appearing nearly point-like
and close to the XRT position) are of prime interest in the search for
the afterglow of this GRB. Given the large number of sources in the
field and the quality of the laser AO images, if either l1 or l2 are
confirmed as the GRB afterglow then the astrometric accuracy will be
comparable to that obtained previously with early and late HST
imaging of other afterglows."
(*) http://lyra.berkeley.edu/~jbloom/grb070621_bloom_kecklaser.pdf
We thank the WMKO staff for their assistance in obtaining these
observations, especially Randy Campbell and Al Conrad.
GCN Circular 6573
Subject
GRB 070621: Swift/UVOT Upper Limits
Date
2007-06-22T17:22:32Z (18 years ago)
From
Stephen Holland at USRA/NASA/GSFC/SSC <sholland@milkyway.gsfc.nasa.gov>
S. T. Holland (CRESST/GSFC/USRA) and B. Sbarufatti (INAF-IASFPA)
report on the behalf of the Swift UVOT team:
The Swift/UVOT observed the field of GRB 070621 starting 120 s
after the BAT trigger (Sbarufatti, et al. 2007, GCN Circ. 6560). We
do not find any source, in any of the UVOT observations, inside the
refined XRT error circle (Sbarufatti, et al., 2007 GCN Circ. 6567), or
at the location of the NOT source (Malesani, et al. 2007, GCN
Circ. 6565).
The 3-sigma upper limits for detecting a source inside the
refined XRT error circle in the initial data products are:
Filter T_start T_stop Exp(s) Mag (3-sigma upper limit)
-----------------------------------------------------------------
V 226 1360 806 20.2
B 702 714 10 18.6
U 680 4799 88 19.7
UVW1 656 4744 236 20.3
UVM2 631 802 38 18.8
UVW2 733 752 19 18.1
White 120 954 204 21.3
-----------------------------------------------------------------
The values quoted above are not corrected for the expected Galactic
extinction corresponding to a reddening of E_{B-V} = 0.05 mag in the
direction of the burst (Schlegel et al. 1998).
GCN Circular 6574
Subject
GRB 070621: VLT optical observations
Date
2007-06-22T18:38:01Z (18 years ago)
From
Paolo D'Avanzo at INAF-OAB <paolo.davanzo@brera.inaf.it>
P. D'Avanzo (INAF - OABr) V. D'Elia (INAF - OAR), D. Fugazza, G.
Tagliaferri (INAF - OABr) on behalf of the MISTICI collaboration and D.
Malesani and J.P.U. Fynbo (DARK/NBI) report:
We observed the field of GRB070621 (Sbarufatti et al., GCN 6560) with
the ESO-VLT equipped with the FORS1 camera in the R and I bands.
Observations were carried out on Jun 22.36 and 22.38 UT (0.39 and 0.41
days after the GRB) in the I and R filters, respectively.
We detect two extended sources near the revised XRT error box
(Sbarufatti et al. GCN 6569), reported by different authors (Malesani et
al. GCN 6565, Tanvir et al. GCN 6570, Bloom et al. GCN 6568 and GCN
6572), at the following coordinates (J2000):
S1) R.A. = 21:35:10.08, Dec. = -24:49:07.5
S2) R.A. = 21:35:10.27, Dec. = -24:49:02.8
with an uncertainty of 0.4".
A comparison between the NOT (Malesani et al. GCN 6565) and VLT images
shows that source S1 remained constant between the NOT and VLT
observation up to 0.1 mag.
Source S2 is not visible in the NOT image, so that a direct comparison
is not possible. When considering the roughly simultaneous WHT I-band
measurement by Tanvir et al. (GCN 6570), we note a small discrepancy
(~0.5 mag) in the magnitude of source S1. After taking into account this
uncertainty, no variability can be claimed for source S2 as well.
Source S1 appears elongated in the East/West direction, consistent with
the superposition of two objects as resolved in the adaptive-optics Keck
image (Bloom et al. GCN 6572).
We acknowledge the support of the ESO staff.
This message can be quoted.
GCN Circular 6575
Subject
GRB070621: RTT150 optical observations
Date
2007-06-23T14:22:12Z (18 years ago)
From
Irek Khamitov at TUG <irekk@tug.tug.tubitak.gov.tr>
I. Khamitov (TUG), I. Bikmaev, N. Sakhibullin (KSU/AST),
Z. Tunca (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.),
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI)
reports:
We observed the field of GRB 070621 (Sbarufatti et al., GCN 6530) with
Russian-Turkish 1.5-m telescope (RTT150, Bakyrlytepe,TUBITAK National
Observatory, Turkey). We made 16x60s exposures in R band, starting at June
21, 23:25:40UT, i.e. approximately 500 s after the burst.
We detected no sources inside the XRT error circle in any of 60~s image,
as well as in combined 16x60~s image with 3-sigma limiting magnitudes
m_R=~20.8 and m_R=~22.3 respectively.
The source reported by Melesani et al (GCN 6565) is clearly detected on
the level m_R=22.15+/-0.2 using the same reference star USNO-B1
0651-0871887, i.e. is not variable within the errors. The astrometric
position of this source is RA=21:35:10.12, DEC=-24:49:07.2 with 0.1 arcsec
accuracy.
The sourse to the east from XRT position, which was found in Gemini
South data (s4, Bloom et. al., GCN 6568), and in image from Keck II LGS
AO (i2, Bloom et. al., GCN 6572) is also detected marginally near the
limit of our combined image.
This message may be cited.