GRB 100702A
GCN Circular 10916
Subject
GRB 100702A: Swift detection of a short burst
Date
2010-07-02T01:23:20Z (15 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
M. H. Siegel (PSU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
J. M. Gelbord (PSU), D. Grupe (PSU), S. T. Holland (CRESST/USRA/GSFC),
J. A. Kennea (PSU), D. M. Palmer (LANL) and T. N. Ukwatta (GSFC/GWU)
report on behalf of the Swift Team:
At 01:03:47 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100702A (trigger=426438). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 245.702, -56.538 which is
RA(J2000) = 16h 22m 49s
Dec(J2000) = -56d 32' 15"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single peak
with a duration of about 0.3 sec. The peak count rate
was ~11000 counts/sec (15-350 keV), at ~0.2 sec after the trigger.
The XRT began observing the field at 01:05:21.1 UT, 93.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
245.6969, -56.5316 which is equivalent to:
RA(J2000) = 16h 22m 47.26s
Dec(J2000) = -56d 31' 53.8"
with an uncertainty of 2.4 arcseconds (radius, 90% containment). This
location is 24 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of
2.84e+21 cm^-2 (Kalberla et al. 2005).
The initial flux in the 2.5 s image was 9.31e-10 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White
filter starting 101 seconds after the BAT trigger. The 2.7'x2.7'
sub-image covers 100% of the XRT error circle. A known source from the
DSS is within the XRT error circle. However, because of the density of
catalogued stars, further analysis is required to determine if this
is the GRB host, afterglow or an unrelated background source. The
coverage of the XRT error circle by the 8'x8' region for the list of
sources generated on-board is uncertain because the large number of
sources filled the available telemetry. Because of the density of
catalogued stars, further analysis is required to report an upper
limit for any afterglow in the region. No correction has been made
for the large, but uncertain extinction expected.
Burst Advocate for this burst is M. H. Siegel (siegel 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 10918
Subject
GRB 100702A: VLT optical observations
Date
2010-07-02T04:20:18Z (15 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
Daniele Malesani (DARK/NBI), Andrew J. Levan (Univ. Warwick), Johan P.
U. Fynbo (DARK/NBI), report on behalf of the X-shooter GRB collaboration:
We observed the field of the short GRB 100702A (Siegel et al., GCN
10916) with the ESO VLT equipped with X-shooter.
In the R-band acquisition image, taken starting on 2010 July 2 at 2:05
UT (1 hr after the GRB), we detect two pointlike sources within the XRT
error circle (Siegel et al., GCN 10916):
A: RA = 16:22:47.05, Dec = -56:31:53.3, R = 15.49
B: RA = 16:22:47.27, Dec = -56:31:55.4, R = 17.20
A third object is located just above the XRT circle:
C: RA = 16:22:47.30, Dec = -56:31:50.6, R = 17.25
Photometry was computed against USNO-B1. Sources A and C are clearly
visible in the DSS, while source B can be barely spotted, blended with
source A. A finding chart is visible at the following URL:
http://www.astro.ku.dk/~malesani/GRB/100702A/GRB100702A_finder.jpg
A second R-band image was taken 48 minutes after, and none of the above
mentioned sources vary by more than 0.05 mag during this time span. For
an afterglow decay proportional to t^-1, a variation of ~0.6 mag would
be expected.
It is thus likely that none of the above sources is related to the GRB.
This is not surprising given the moderately crowded field (at Galactic
latitude b = -5 deg). We note that the glare from the above mentioned
bright objects makes it difficult to identify faint sources within the
XRT error circle.
We acknowledge excellent and prompt support from the observing staff at
Paranal, in particular Christophe Martayan, Andrew Fox, Vincenzo
Mainieri, Manuel Olivares, Thomas Szeifert, and the visitor observer,
Nick Cox.
GCN Circular 10919
Subject
GRB 100702A: Magellan near-IR observations
Date
2010-07-02T04:37:40Z (15 years ago)
From
Edo Berger at Harvard <eberger@cfa.harvard.edu>
W. Fong, E. Berger, and M. Servillat (Harvard) report:
"We observed the location of the short GRB 100702A (GCN 10916) with
the PANIC infrared imager on the Magellan/Baade 6.5-m telescope
starting on 2010 July 2.089 UT (65 min after the burst). A total of
27 min were obtained in the J-band with seeing of about 0.55 arcsec.
Within the 2.4-arcsec radius XRT error circle we detect one bright
point source and two fainter sources at the following coordinates
(J2000; astrometry relative to the 2MASS catalog):
S1: RA = 16:22:47.23, DEC = -56:31:55.6
S2: RA = 16:22:47.53, DEC = -56:31:54.6
S3: RA = 16:22:47.24, DEC = -56:31:52.2
Source S1 is the same as source "B" in GCN 10918 (Malesani et al.),
while sources S2 and S3 are not detected in their finder.
We note that in 2MASS images of the field source S1 is possibly
blended with the bright star at RA = 16:22:47.01, DEC = -56:31:53.5
(designated source "A" in GCN 10918), while sources S2 and S3 are
below the 2MASS sensitivity threshold.
Additional observations are planned to check for variability of
sources S2 and S3."
GCN Circular 10921
Subject
GRB 100702A: Second epoch of Magellan near-IR observations and afterglow limits
Date
2010-07-02T13:26:12Z (15 years ago)
From
Edo Berger at Harvard <eberger@cfa.harvard.edu>
E. Berger, W. Fong, and M. Servillat (Harvard) report:
"We re-observed the location of the short GRB 100702A (GCN 10916) with
the PANIC infrared imager on the Magellan/Baade 6.5-m telescope
starting on 2010 July 2.290 UT (4.8 hours after our first observation,
which started 65 min after the burst; GCN 10919). A total of 27 min
were obtained in the J-band with slightly worse seeing than in our
first epoch, 0.75 arcsec. Digital image subtraction of the two epochs
using the ISIS package reveals no change in the flux of our
previously-identified sources S1 (source "B" of Malesani et al. GCN
100918), S2, or S3. No other variable sources are detected within a
45x45 arcsec region centered on the XRT position to a 5-sigma limit of
J>22.1 mag (Vega).
We note, however, that the bright star at RA = 16:22:47.01, DEC =
-56:31:53.5 (designated source "A" in GCN 10918) strongly contaminates
the subtracted image over about 1/4 of the XRT error circle."
GCN Circular 10922
Subject
Swift/UVOT observations of GRB100702A
Date
2010-07-02T13:37:35Z (15 years ago)
From
Massimiliano de Pasquale at MSSL-UCL <mdp@mssl.ucl.ac.uk>
M. De Pasquale (MSSL-UCL) and M. H. Siegel (PSU) report on behalf of the
Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 100621A 101s
after the BAT trigger (Siegel et al, GCN 10916). The enhanced XRT error
circle appears crowded with sources (Malesani et al., GCN 10918, Fong et
al, GCN 10919) which blend together. There is no clear indication of
change of optical flux between the first exposures and later ones. The
preliminary magnitudes and 3-sigma upper limits for the finding chart
exposures (FC) and summed images for the emission in the XRT enhanced
error circle are:
Filter T_start T_stop Exp(s) Magnitude/3-sigma upper
limit
-------------------------------------------------------------
white (FC) 101 251 147 17.99 +/- 0.07
white 594 10684 1295 17.84 +/- 0.05
u (FC) 314 564 246 18.85 +/- 0.17
u 5020 5151 131 18.96 +/- 0.26
v 4405 17014 735 16.72 +/- 0.04
b 570 6306 216 17.79 +/- 0.08
uvw1 4815 5015 196 > 19.60
uvm2 4610 4810 197 > 19.40
uvw2 4200 16457 1432 > 20.85
-------------------------------------------------------------
The quoted upper limits have not been corrected for the expected Galactic
extinction along the line of sight corresponding to E_(B-V) = 0.41 mag.
All photometry is on the UVOT photometric system described in Poole et al.
(2008, MNRAS, 383, 627).
GCN Circular 10923
Subject
Swift/UVOT observations of GRB100702A - correction
Date
2010-07-02T13:54:36Z (15 years ago)
From
Massimiliano de Pasquale at MSSL-UCL <mdp@mssl.ucl.ac.uk>
M. De Pasquale (MSSL) reports:
"In the text of the GCN circular 10922, Swift/UVOT observations of
GRB100702A', GRB100621A
is erroneously mentioned. All the data quoted in that circular refer to
GRB100702A. We
apologize for the mistake".
GCN Circular 10924
Subject
GRB 100702A: Swift XRT refined analysis
Date
2010-07-02T15:15:29Z (15 years ago)
From
Dirk Grupe at PSU/Swift-XRT <grupe@astro.psu.edu>
D. Grupe and M. Siegel (PSU)
report on behalf of the Swift-XRT team:
We have analyzed 3770 s of XRT data for GRB 100702A
(Siegel et al. GCN Circ. 10916), from 100 s to 9676 s after the
BAT trigger. The data comprise 190 s in Windowed Timing (WT) mode
with the remainder in Photon Counting (PC) mode. The light curve can
be modeled with an initial power-law decay with an index of
alpha=0.65 (+0.37, -0.25), followed by a break at T+185 s to an alpha
of 4.33 (+0.53, -0.24). The afterglow is not detected after the
first orbit.
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.92 (+0.11, -0.10). The
best-fitting absorption column is 3.6 (+/-0.4) x 10^21 cm^-2, in
excess of the Galactic value of 2.8 x 10^21 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 4.45 x 10^-11 (6.94 x 10^-11) erg
cm^-2 count^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00426438.
This circular is an official product of the Swift-XRT team.
GCN Circular 10926
Subject
GRB 100702A, Swift-BAT refined analysis
Date
2010-07-02T15:45:04Z (15 years ago)
From
Takanori Sakamoto at NASA/GSFC <takanori@milkyway.gsfc.nasa.gov>
W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC),
T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. H. Siegel (PSU), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 100702A (trigger #426438)
(Siegel, et al., GCN Circ. 10916). The BAT ground-calculated position is
RA, Dec = 245.693, -56.549 deg which is
RA(J2000) = 16h 22m 46.4s
Dec(J2000) = -56d 32' 57.4"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 61%.
The mask-weighted light curve shows a FRED-like pulse starting at T_zero to
~T+0.25 sec. There is a possible weak pulse emission at T-0.25 sec.
T90 (15-350 keV) is 0.16 +- 0.03 sec (estimated error including systematics).
The time-averaged spectrum from T+0.036 to T+0.236 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.54 +- 0.15. The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T-0.36 sec in the 15-150 keV band
is 2.0 +- 0.2 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/426438/BA/