GRB 070406
GCN Circular 6298
Subject
GRB 070406: Swift XRT refined analysis
Date
2007-04-16T16:15:33Z (19 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
E. Troja (U. Leicester/INAF-IASFPa), K. L. Page (U. Leicester), S. McBreen
(MPE), D. N. Burrows (PSU) and N. Gehrels (NASA/GSFC) report on behalf of
the Swift XRT team:
Swift monitored the field of GRB 070406 (Cummings et al., GCN Circ. 6247)
for nine days, starting 20.6 hr after the burst. From the analysis of the
full data set, consisting of 115 ks of total exposure in XRT/Photon
Counting mode, no X-ray afterglow is detected within the BAT refined error
circle (Krimm et al., GCN Circ.6261).
The two X-ray sources (S1 and S2 - Troja et al., GCN Circ. 6265) inside
the BAT error region do not show a fading behavior, therefore none of them
can be identified as the X-ray counterpart of GRB 070406.
The non detection in the first follow-up observation (from T0+20.6 hr to
T0+41.9 hr) implies an X-ray afterglow fainter than 7.5e-04 cts/s (3-sigma
upper limit). Assuming a power-law spectral shape with photon index 2 and
a Galactic absorption of 1.8e20 cm-2 (Dickey & Lockman, 1990), it
corresponds to an observed (unabsorbed) limiting flux of 2.7e-14 (2.9e-14)
erg cm-2 s-1 in the 0.3-10 keV band.
No further Swift observations are planned.
This circular is an official product of the Swift XRT Team.
GCN Circular 6266
Subject
GRB 070406: "Star" in XRT error circle S2 is an AGN?
Date
2007-04-10T21:45:34Z (19 years ago)
From
Edo Berger at Carnegie Obs <eberger@ociw.edu>
E. Berger (Carnegie Observatories) reports:
"Inspection of our Gemini-North/GMOS images taken on 2007 April 8.39 UT in
0.55" seeing reveal that the source near the center of XRT source S2 (GCN
6265), which is classified as a star in SDSS, is embedded within a clearly
extended source. This may be a chance superposition of a star on top of a
background galaxy, or more likely, it is a bright AGN, similar to the
source coincident with XRT source S1 (GCN 6262). Additional XRT
observations are required to verify whether the source is steady.
We also note that in addition to the galaxy located 3.7" from the XRT
position, our images reveal five fainter extended sources within the error
circle."
GCN Circular 6265
Subject
GRB 070406: Swift XRT team further analysis
Date
2007-04-10T21:10:25Z (19 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
E. Troja (U. Leicester/INAF-IASFPa), K. L. Page (U. Leicester), J. Racusin
(PSU), S. McBreen (MPE), J. P. Osborne (U. Leicester), V. La Parola
(INAF-IASFPa), D. N. Burrows (PSU) and N. Gehrels (NASA/GSFC) report on
behalf of the Swift XRT team:
We have performed further analysis on Swift XRT observations of the field
of GRB 070406 (Cummings et al., GCN Circ. 6247). Our data set consists of
56 ks of XRT observations taken in Photon Counting (PC) mode.
Thirteen serendipitous X-ray sources are detected with S/N > 3 with the
WAVDETECT algorithm, five of which have nearby optical counterparts in the
SDSS catalogue. We match these sources to obtain a best fit mean frame
shift, carefully accounting for several instrumental factors including
exposure map correction, and additional hot pixel removal. The resulting
astrometric corrected position of the X-ray source (S1), proposed as the
afterglow candidate (Troja et al., GCN Circ. 6255), is:
RA (J2000) = 13h 15m 51.59s
Dec(J2000) = +16d 30' 46.6"
with an estimated error radius of 4.7'' (90% containment). This position
lies 1.9 arcsec from the position quoted in Butler et al. (GCN Circ.
6263) and 1.7 arcsec from the bright optical source reported by Kann (GCN
Circ. 6256).
The X-ray lightcurve of S1 can be found at:
http://www.ifc.inaf.it/~troja/grb070406_s1.gif
It displays a steady behavior with a fairly constant count rate of 1.5e-03
cts/s. It seems unlikely that S1 is the X-ray counterpart of GRB 070406,
as noted by Butler et al. (GCN Circ. 6263), and it is more likely
associated with AGN activity (Berger et al., GCN Circ. 6262).
Examining the observations performed between 2 d and 3.5 d after the
burst, another faint source (S2) is detected within the refined BAT error
circle (Krimm et al., GCN Circ. 6261). Its astrometric corrected position
is:
RA (J2000) = 13h 15m 43.42s
Dec(J2000) = +16d 31' 09.3"
with an estimated error radius of 5.7'' (90% containment). This position
lies 92 arcsec from the BAT refined position given in Krimm et al. (GCN
Circ. 6261). According to the SDSS catalogue, two galaxies lie 3.7 and
13.6 arcsec from the X-ray position of S2, respectively. A third object,
classified as a star, is 1.3 arcsec from the X-ray source.
The X-ray lightcurve of S2 can be found at:
http://www.ifc.inaf.it/~troja/grb070406_s2.gif
It shows some evidence of fading, but due to the faintness of the source
we are unable to clearly state whether the source is decaying. A
Kolmogorov-Smirnov test, performed on the arrival times of 20 source
photons, gives a probability of 10% that the source S2 is steady. The 10%
probability of constancy is much less than a two sigma detection of
variability; therefore the source may be consistent with being constant.
Swift follow-up observations will be performed to confirm its variability.
This Circular is an official product of the Swift XRT Team.
GCN Circular 6263
Subject
GRB 070406: Astrometrically Refined XRT Position, Unfading Source
Date
2007-04-09T19:53:43Z (19 years ago)
Edited On
2025-04-09T18:45:29Z (7 months ago)
From
Nat Butler at MIT/CSR <nrbutler@space.mit.edu>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Tyler Barna at University of Minnesota <tylerpbarna@gmail.com>
N. R. Butler and J. S. Bloom (UC Berkeley) report:
Using 53.6 ksec of exposure by the Swift XRT on the field of GRB070406
(Cummings et al.; GCN 6247), we derive a refined astrometrically-corrected
position for the X-ray afterglow candidate (Troja et al.; GCN 6255) of
RA= 13 15 51.51 , Dec= +16 30 48.1 +/- 2.7" (90% Conf.)
(http://astro.berkeley.edu/~nat/swift/xrt_pos.html, DSS position v1.3).
The position is within 1.4" of (and the X-ray source is likely associated
with) the bright optical source reported by Kann (GCN 6256) and found
to be a quasar by Berger et al. (GCN 6262).
Examining the arrival times for 70 source counts in comparison to the detector
on-times, we find a KS-test probability that the source rate is steady
and non-fading of 80%. It is thus very unlikely that this X-ray source
and the associated possible optical counterparts are the afterglow of
GRB070406.
GCN Circular 6262
Subject
GRB 070406: Bright galaxy in XRT error circle is a quasar
Date
2007-04-09T14:55:06Z (19 years ago)
From
Edo Berger at Carnegie Obs <eberger@ociw.edu>
E. Berger (Carnegie), D.B. Fox (Penn State), and E. Ofek (Caltech) report
on behalf of a larger collaboration:
"Starting on 2007 April 8.31 UT we used the Gemini Multi-Object
Spectrograph (GMOS) on Gemini-North to obtain a spectrum of the bright
galaxy located in the XRT error circle of the possible afterglow of GRB
070406 (GCNs 6255,6256,6259). We detect a narrow [OII] emission line and
broad H-gamma and H-delta emission features at z=0.703. The broad H-gamma
and H-delta lines are indicative of a quasar spectrum, and it is therefore
likely that the X-ray emission detected with XRT is due to AGN activity
and not the afterglow of GRB 070406. Further XRT observations are
essential to confirm fading versus long-term variability."
GCN Circular 6261
Subject
GRB 070406, Swift-BAT refined analysis
Date
2007-04-09T14:09:15Z (19 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <jayc@milkyway.gsfc.nasa.gov>
H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
C. Markwardt (GSFC/UMD), S McBreen (MPE), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC)
on behalf of the Swift-BAT team:
Using the data set from T-2.3 to T+7.7 sec, we report further analysis
of BAT GRB 070406 (trigger #274153) (Cummings, et al., GCN Circ. 6247).
The BAT ground-calculated position is RA, Dec = 198.956, 16.530 deg
which is
RA(J2000) = 13h 15m 49.3s
Dec(J2000) = 16d 31' 46"
with an uncertainty of 2.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 92%.
The lightcuve shows two peaks at T+0 and T+0.7 sec. The burst was very
faint in BAT, and additional peaks may be hidden in the noise.
T90 (15-350 keV) is 0.7 +- 0.2 sec (estimated error including systematics).
The time-averaged spectrum from T+0.0 to T+0.7 is best fit by
a simple power-law model.
The power law index of the time-averaged spectrum is 0.9 +- 0.4.
The fluence in the 15-150 keV band is 4.5 +- 1.0 x 10^-08 erg/cm2.
The 1-sec peak photon flux measured from T+0.00 sec in the 15-150 keV
band is 0.7 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90%
confidence level.
GCN Circular 6260
Subject
GRB 070406: Correction to the optical candidate in GCN6253
Date
2007-04-08T08:47:20Z (19 years ago)
From
W.K. Zheng at NAOC <zwk@bao.ac.cn>
L.P. Xin, M.Zhai, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J.S. Deng,
and W.K. Zheng on behalf of EAFON report:
We refined xinglong TNT data again, the candidate we
recommended before(GCN6253) may not be a real object
but a disturbance source due to CCD problem, we apologize
for this mistake and miss guidance.
We note there are several dark pixels at the CCD location
we mention before, and there is always a point-like source
at the same dark pixels of CCD positon in our white band
image even thought the field has changed. To confirm this
we performed third epoach observation with multi-band about
41 hours after the burst. We did not detect the candidate
in all White, R, V bands, but in white bandat the dark
pixels postion there was still a faint point-like source.
Some subframs are avaliable at:
http://www.xinglong-naoc.org:8080/GRB070406/20h_W.fit
http://www.xinglong-naoc.org:8080/GRB070406/35h_W.fit
http://www.xinglong-naoc.org:8080/GRB070406/41h_W.fit
http://www.xinglong-naoc.org:8080/GRB070406/41h_R.fit
the source detected by Bloom et al.(GCN6259) may just be a
coincidence with the coordinat we mentioned before.
This message can be cited.
GCN Circular 6259
Subject
GRB 070406: Gemini South Imaging and XRT analysis
Date
2007-04-08T05:05:48Z (19 years ago)
From
Josh Bloom at UC Berkeley <jbloom@astron.berkeley.edu>
J. S. Bloom (UC Berkeley), H-W. Chen (Chicago), J. X. Prochaska (UC
Santa Cruz), N. R. Bulter (UC Berkeley) report:
We observed the field of GRB 070406 (Cummings et al.; GCN 6247) with
the GMOS instrument on Gemini South in r and i-band filters. An i-
band finder is provided (*) with mean epoch 7.26 April 2007 UT (~29.4
hours after the GRB). The images cover the region of the XRT source
(Troja et al.; GCN 6255). Our re-analysis of the XRT data, based on
the first 20 ks and allowing for the possiblity of an astrometric XRT
frame offset, yields a moderately larger XRT error circle (labeled
"Butler") of:
RA(J2000) = 13:15:51.16 DEC = +16:30:47.7 (6.4" at 90%
confidence)
We cannot confirm any variability of the X-ray source. The SDSS
galaxy noted by Kann (GCN 6256) and the faint source noted by
Malesani et al. (GCN 6257) are well detected. We note that the
Malesani source appears to be resolved and it thus unlikely to be the
afterglow (it also appears marginally detected in the SDSS i-band
image from Cool et al. GCN 6248). We note 5 additional sources in the
XRT error circle (J2000):
RA DEC
s1 13:15:51.41 +16:30:42.6
s2 13:15:51.19 +16:30:41.9
s3 13:15:50.94 +16:30:42.6
s4 13:15:50.75 +16:30:48.0
s5 13:15:51.48 +16:30:52.7
We make no claims about variability at this time.
We find no source at the location of the Xin et al. transient (GCN
6253). However, we do detect a faint source ~2.3 arcseconds to the
South West of that position at:
OT? 13:15:40.91 16:34:13.1
This source is several magnitudes fainter than the galaxy to the
northwest noted by Xin et al., whereas Xin et al. indicate that their
source was 4 magnitudes brighter at 35.4 hour after the GRB."
This message can be cited.
(*) http://lyra.berkeley.edu/~jbloom/grb070406_ep1.pdf
GRAASP thanks to Henry Lee and the observing team at Gemini South for
performing these ToO observations.
GCN Circular 6258
Subject
GRB070406: Swift UVOT observations
Date
2007-04-08T00:33:09Z (19 years ago)
From
Wayne Landsman at GSFC/SSAI <landsman@milkyway.gsfc.nasa.gov>
W. Landsman (NASA/GSFC), M. Chester (PSU) and S. McBreen (MPE) report on
behalf of the Swift UVOT team:
Swift/UVOT observed the field of GRB 070406 starting 20.6 hours after
the trigger. Swift did not autonomously slew because the burst was
below the trigger threshold.
Comparison with pre-burst DSS and SDSS images show no new source within
the BAT error circle with the following 3 sigma upper limits in the
co-added frames in all filters:
Filter T_start T_Stop Exp(s) Mag 3-sig UL
(s) (s)
V 84712 132829 1407 21.6
B 74251 139272 3360 23.0
U 102871 138592 2539 22.4
UVW1 98648 137680 3666 24.3
UVM2 90394 133486 2845 23.5
UVW2 80549 131916 2626 23.9
White 75162 115280 1318 22.6
The blue galaxy found in pre-burst SDSS images (Kann, GCN 6256) within
the tentative XRT error circle (Troja et al., GCN 6255) is found from
the UVOT observations to be unusually bright in the UV filters.
Mag Err
V 20.05 0.15
B 20.06 0.05
U 19.11 0.04
UVW1 18.83 0.04
UVM2 18.52 0.05
UVW2 18.67 0.04
However, there is no compelling evidence of variability of this source
within the individual UVOT frames.
GCN Circular 6257
Subject
GRB 070406: further analysis of NOT images.
Date
2007-04-07T23:01:08Z (19 years ago)
From
Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center <malesani@astro.ku.dk>
D. Malesani (DARK/NBI), H. Uthas (NOT), J. Hjorth, C.C. Thoene, J.P.U.
Fynbo (DARK/NBI), and M.I. Andersen (AIP), report on behalf of a larger
collaboration:
Following the identification of a candidate X-ray afterglow (Troja et al.,
GCN 6255) of GRB 070406 (Cummings et al., GCN 6247), we inspected again
our images taken with the NOT (Malesani et al., GCN 6254).
Inside the XRT error circle, we confirm the presence of a bright object,
present in the USNO and SDSS catalogs and already noted by Kann (GCN
6256). By comparing its magnitude with several other SDSS objects
(photometry as presented by Cool et al. in GCN 6248), we find r = 19.89 +-
0.07 (AB), where the error corresponds to the scatter between the
instrumental (R band) and SDSS (r band) magnitudes. Thus, even if this
object is related to the GRB, there is no evidence for afterglow
contribution at 24.9 hr after the trigger.
At the edge of the XRT error circle, we also note the presence of a second
object, barely detected in our image (r_AB ~ 23.7), with coordinates
(J2000, 1" error radius):
alpha = 13:15:51.15
delta = +16:30:50.9
GCN Circular 6256
Subject
Short GRB 070406 - Possible Bright Host Galaxy
Date
2007-04-07T20:00:52Z (19 years ago)
From
Alexander Kann at TLS Tautenburg <kann@tls-tautenburg.de>
D. A. Kann (TLS Tautenburg) reports:
At the position of the possible X-ray afterglow (Troja, Page &
McBreen, GCN 6255) of the short GRB 070406 (Cummings et
al., GCN 6247), there is a bright galaxy (at least, it is flagged as
such) detected in the SDSS at position (J2000):
RA = 13:15:51.6
Dec = +16:30:48.31
This is 3".75 away in RA and 1".41 in Dec. and thus within the
error circle.
The (model) magnitudes are:
u' = 20.017 +/- 0.050
b' = 19.775 +/- 0.016
v' = 19.720 +/- 0.019
r' = 19.630 +/- 0.025
i' = 19.510 +/- 0.078
It is thus quite blue. Further X-ray observations should show if
this is possibly only an AGN.
Spectroscopy of this galaxy is strongly encouraged.
This message may be cited.
GCN Circular 6255
Subject
GRB 070406: Swift XRT Team analysis - Possible X-ray counterpart
Date
2007-04-07T19:36:58Z (19 years ago)
From
Eleonora Troja at INAF-IASFPA <nora@ifc.inaf.it>
E. Troja (U. Leicester/INAF-IASFPa), Kim Page (U.
Leicester) and S. McBreen (MPE) report on behalf of the
Swift XRT team:
We analysed the first 13 orbits of Swift XRT data for
GRB 070406 (Cummings et al., GCN Circ. 6247), taken
between
20.6 hr and 35.5 hr after the BAT trigger. Swift did not
autonomously slew because the burst was below the trigger
threshold.
In the Photon Counting mode image (13 ks of exposure)
no source is detected at the position of the optical
candidate, proposed by Xin et al. (GCN Circ. 6253), with a
3-sigma upper limit of 1.5E-03 cts/s.
A faint uncatalogued X-ray source is detected within the
BAT
error circle. The source is located at:
RA(J2000)= 13h 15m 51.35s
Dec(J2000)=+16d 30' 46.9"
with an error radius of 5" (90% containment). This lies
68 arcsec from the BAT position given in GCN Circ. 6247.
We note that the projected offset of the source from the
bright galaxy quoted in Ofek et al. (GCN Circ. 6249)
is 45". At a redshift of z=0.11 it corresponds to 89 kpc.
With the data so far available we can not tell if the
source is fading. Further Swift observations are ongoing.
This circular is an official product of the Swift XRT
Team.
[GCN OPS NOTE(09apr07): Per author's request, the word 'counterpart'
was added to the Subject line, and the Instituitional trailer
signifying it is virus-free was removed.]
GCN Circular 6254
Subject
GRB 070406: NOT observations
Date
2007-04-07T16:43:11Z (19 years ago)
From
Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center <malesani@astro.ku.dk>
D. Malesani (DARK/NBI), H. Uthas (NOT), C.C. Thoene, J.P.U. Fynbo, J.
Hjorth (DARK/NBI), M.I. Andersen (AIP) report on behalf of a larger
collaboration:
We observed the field of the short GRB 070406 (Cummings et al., GCN 6247)
using the NOT equipped with ALFOSC. Observations were carried out in the R
band, started on 2007 Apr 7.058 UT (24.5 hr after the GRB), and the total
exposure time was 30 min.
Inside the BAT error circle, we find no source brighter than the SDSS
limit r_AB ~ 23 (Cool et al. GCN 6248; see also Adelman-McCarthy et al.
2006, ApJS, 162, 38). The limiting magnitude of our image is R_AB ~ 23.5.
We also do not see any object at the position of the candidate afterglow
proposed by Xin et al. (GCN 6253) down to the quoted limiting magnitude.
[GCN OPS NOTE(09apr07): Per author's request, the "Zheng et al" was chnaged
to "Xin et al".]
GCN Circular 6253
Subject
GRB 070406: Optical candidate
Date
2007-04-07T15:04:31Z (19 years ago)
From
W.K. Zheng at NAOC <zwk@bao.ac.cn>
L.P. Xin, M.Zhai, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J.S. Deng,
and W.K. Zheng on behalf of EAFON report:
We have refined the first epoach of Xinglong TNT 80cm data of
GRB070406(Cummings et al.; GCN 6247), we find an uncatalog object
at the location: RA, DEC 198.9206, +16.5708 (J2000),which is
RA (J2000) 13:15:41
Dec(J2000) +16:34:15
this position is 3.3 arcmin away from the center of BAT position but
3.3 arcmin is 0.3 arcmin far away from the uncertainty of BAT position.
We also reimaged this fied 35.4 hours after the burst with the same
band, preliminary result shows the object has faded ~1 mag during our
two epoach observation, the object has a mag of ~18.4 derived form
USNO-A2.0 35.4 hours after the burst. so we recommend this object as
the candidate of GRB070406 though it is 0.3 arcmin far away from the
uncertainty of BAT position.
We also find there is a faint galaxy 9.8 arcsec away from the candidate
in the SDSS image, at the location:RA, DEC 198.9192, +16.5732,
this galexy has a magnitude of r=22.07. While the galaxy mentioned in
GCN6249(Ofek et al.) lies on the other side of the BAT center positon.
We encourage further photometry and spectrum observation to confirm
this candidate.
This message may be cited.
GCN Circular 6252
Subject
GRB 070406: The exprosure time of Xinglong TNT optical Upper Limit
Date
2007-04-07T08:36:52Z (19 years ago)
From
L.P. Xin at NAOC <xlp@bao.ac.cn>
W.K. Zheng, M.Zhai, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J.S. Deng,
Y. Urata, J.Z. Li and L.P. Xin on behalf of EAFON report:
I want to make a apologize that
I have forgotten to provide you the exposure time
of the combined image in CGN 6250,
that was 1090s .
This message may be cited
GCN Circular 6251
Subject
GRB 070406: SARA upper limit
Date
2007-04-07T05:19:27Z (19 years ago)
From
Adria C. Updike at Clemson U <aupdike@clemson.edu>
A. C. Updike, H. A. Eid, and D. H. Hartmann (Clemson University)
report on behalf of the Clemson GRB Follow-Up Team:
We imaged the field of GRB 070406 approximately 26 hours after Swift
Trigger 274153 with the SARA 0.9m at Kitt Peak under good weather conditions.
We obtained 20 300-second exposures in the R band. We find no fading OT
candidate in the stacked images down to a limiting magnitude of R = 20.0
+/- 0.2 mag (based on calibration to USNO A2.0).
The Clemson University GRB Response Site may be found at:
http://people.clemson.edu/~kgarime/burst/index.php
The SARA Homepage can be found at:
http://saraobservatory.org
Thanks to Alexander Kann for his input.
This message may be cited.
GCN Circular 6250
Subject
GRB 070406: Xinglong TNT optical Upper Limit
Date
2007-04-07T00:38:13Z (19 years ago)
From
L.P. Xin at NAOC <xlp@bao.ac.cn>
W.K. Zheng, M.Zhai, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J.S. Deng,
Y. Urata, J.Z. Li and L.P. Xin on behalf of EAFON report:
We have imaged the field of GRB 070406 with the
TNT 0.8m telescope at Xinglong Observatory started
from 20:42:33 UT on Apil. 6, about 19.86 hours after the burst.
seven white band images were obtained,
and no new source was found in our Totally combined image
within the error region of BAT of the Swift.
the 3-sigma limit is ~19.8 derieved form USNO A-2.0.
This message may be cited.
GCN Circular 6249
Subject
GRB 070406: photo-z of a bright galaxy in BAT error circle
Date
2007-04-06T21:29:54Z (19 years ago)
From
Eran Ofek at Tel Aviv U. <eran@wise1.tau.ac.il>
E. O. Ofek (Caltech) reports on behalf of a larger collaboration:
Within the BAT error circle of GRB070406 (Cummings et al.; GCN 6247),
there is a relatively bright (g~18.5) SDSS galaxy.
The coordinates of the galaxy are:
13:15:52.94 +16:31:26.0 J2000.0
and it has a photometric redshift of 0.11.
GCN Circular 6247
Subject
GRB 070406: Swift detection of a burst
Date
2007-04-06T21:00:11Z (19 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
J. R. Cummings (NASA/UMBC), J. A. Kennea (PSU),
W. B. Landsman (NASA/GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL), M. Stamatikos (NASA/ORAU) and
E. Troja (INAF-IASFPA) report on behalf of the Swift Team:
At 00:50:40 UT, BAT triggered and located GRB 070406
(Trigger #274153) as a sub-threshold (6.4 sigma) peak
in a 0.256 second image. Subsequent ground analysis
optimized the detection to a confident 8.3 sigma, at the
location: RA, dec 198.956, +16.529d (J2000), which is
RA(J2000) +13h 15m 49s
dec(J2000) +16d 31' 46"
with an uncertainty of 3 arcmin (radius, 90% containment,
including systematic uncertainty). The burst is ~0.7 seconds
long with a double-peaked profile, with a peak
count rate of 1200 counts/s.
Because the burst was sub-threshold on-board,
Swift did not automatically slew to the GRB location.
However a Target Of Opportunity (ToO) observation
is currently being prepared with a 60 kilosecond
observation beginning ~2200 UT.