GRB 140818B
GCN Circular 16709
Subject
GRB 140818B: Swift detection of a burst
Date
2014-08-18T18:58:42Z (11 years ago)
From
David Burrows at PSU/Swift <burrows@astro.psu.edu>
A. Vargas (PSU), D. N. Burrows (PSU), S. B. Cenko (GSFC),
N. Gehrels (NASA/GSFC), C. Gronwall (PSU), L. M. Z. Hagen (PSU),
J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), J. L. Racusin (NASA/GSFC),
B. Sbarufatti (INAF-OAB/PSU) and C. A. Swenson (PSU) report on behalf
of the Swift Team:
At 18:44:16 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 140818B (trigger=609885). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 271.148, -1.361 which is
RA(J2000) = 18h 04m 35s
Dec(J2000) = -01d 21' 40"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a multi-peaked
structure with a duration of about 20 sec. The peak count rate
was ~1200 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 18:46:05.6 UT, 109.2 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 271.13656, -1.38660 which is equivalent
to:
RA(J2000) = 18h 04m 32.77s
Dec(J2000) = -01d 23' 11.8"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 100 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. We cannot determine whether the source is
fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 3.53
x 10^21 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 113 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 none of
the XRT error circle. The 8'x8' region for the list of sources generated
on-board covers 100% of the BAT error circle. 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 expected
extinction corresponding to E(B-V) of 0.71.
Burst Advocate for this burst is A. Vargas (avargas AT swift.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 16711
Subject
GRB 140818B: OSN I-band afterglow candidate
Date
2014-08-18T22:50:24Z (11 years ago)
From
Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>
F.J. Aceituno (OSN/IAA-CSIC), J. Gorosabel (IAA-CSIC/UPV-EHU) and A.J.
Castro-Tirado (IAA-CSIC/UMA), report on behalf of a larger collaboration:
We observed the field of GRB 140818B (Vargas et al., GCN 16709) with the
1.5m OSN telescope at Observatorio de Sierra Nevada (Spain). Several 300s
images were acquired in the I- and R-band starting on Aug 18, 20:15 UT
(i.e. 1.5 hours post burst). An optical source at the edge of the
Swift/XRT error box is detected at coordinates (J2000) RA: 18 04 32.47,
Dec: -01 23 09.8 (+/- 1"), which is not present in the corresponding DSS-2
image. A preliminary photometry against the USNO B1.0 catalog yields
an I-band magnitude of 19.7 (Vega). At the moment we cannot determine if
the source if fading in brightness. Further observations are encouraged.
GCN Circular 16712
Subject
GRB 140818B: Enhanced Swift-XRT position
Date
2014-08-19T00:18:06Z (11 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester)
report on behalf of the Swift-XRT team.
Using 990 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 140818B, 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 = 271.13556, -1.38629 which is equivalent
to:
RA (J2000): 18h 04m 32.53s
Dec (J2000): -01d 23' 10.6"
with an uncertainty of 1.9 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 16713
Subject
GRB140818B : GROND afterglow candidate
Date
2014-08-19T02:45:09Z (11 years ago)
From
Karla Varela at MPE <kvarela@mpe.mpg.de>
F. Knust, K. Varela, and J. Greiner (all MPE Garching) report on behalf of
the GROND team:
We observed the field of GRB 140818B (Swift-60985; Vargas et al., GCN
16709) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,PASP
120, 405) mounted at the 2.2m MPG telescope at ESO La Silla Observatory
(Chile). Observations started at 23:43 UT on 2014-08-18, 5 hours after the
GRB trigger. They were performed at an average seeing of 1.23" and at an
average airmass of 1.2.
Based on images with exposure times of 340s in g�r'i'z� and 370s in JHKs,
we detect a source inside the 1.9� error circle reported by Beardmore et
al. (GCN 16712) at
RA (J2000): 18h 04m 32.47s
Dec (J2000): -01d 23� 09.7"
with an uncertainty of 0.5� and magnitudes
g� > 24.1 mag,
r' = 22.1 +/- 0.1 mag,
i' = 21.8 +/- 0.1 mag,
z' = 21.4 +/- 0.1 mag.
J > 20.9 mag,
H > 20.7 mag, and
K > 19.2 mag.
The afterglow candidate reported by Aceituno et al. (GCN #16711) is also
detected inside the 3.9� XRT error circle (GCN 16711) but not inside the
1.9� XRT error circle (GCN 16712) with magnitudes :
r' = 22.4 +/- 0.1 mag,
i' = 21.6 +/- 0.1 mag,
z' = 20.9 +/- 0.1 mag.
The given magnitudes are derived based on calibrating the images against
the GROND zeropoints and 2MASS field stars are not corrected for the
Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.73
in the direction of the burst (Schlegel et al. 1998).
GCN Circular 16714
Subject
GRB 140818B: Fermi GBM detection
Date
2014-08-19T03:03:05Z (11 years ago)
From
Eric Burns at U of Alabama <EricKayserBurns@gmail.com>
Eric Burns (UAH) reports on behalf of the Fermi GBM Team:
"At 18:44:15.70 UT on 18 August 2014, the Fermi Gamma-Ray Burst
Monitor triggered and located GRB 140818B (trigger 430080258
/ 140818781). which was also detected by the Swift/BAT
(Burrows et al. 2014, GCN 16709). The GBM on-ground
location is consistent with the Swift position. The angle
from the Fermi LAT boresight is 32 degrees.
The GBM light curve consists of one main peak followed by
multiple smaller peaks with a duration (T90) of about 23.6 s
(50-300 keV). The time-averaged spectrum from T0-6.14 s to
T0+20.5 s is best fit by a simple power law function with
index -1.7 +/- 0.1.
The event fluence (10-1000 keV) in this time interval is
(1.6 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux
measured starting from T0+0.26 s in the 10-1000 keV band
is 1.7 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 16716
Subject
GRB 140818B: Swift-XRT refined Analysis
Date
2014-08-19T12:58:04Z (11 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
B.P. Gompertz (U. Leicester), M. de Pasquale (INAF-IASFPA), A. Maselli
(INAF-IASFPA), A. Melandri (INAF-OAB), J.A. Kennea (PSU), V. Mangano
(PSU), M.C. Stroh (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester) and A. Vargas report on behalf of the Swift-XRT team:
We have analysed 10 ks of XRT data for GRB 140818B (Vargas et al. GCN
Circ. 16709), from 94 s to 52.9 ks after the BAT trigger. The data
comprise 7 s in Windowed Timing (WT) mode (taken while Swift was
slewing), with the remainder in Photon Counting (PC) mode. The enhanced
XRT position for this burst was given by Beardmore et al. (GCN Circ.
16712).
The light curve can be modelled with a power-law decay with a decay
index of alpha=0.64 (+/-0.05).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.3 (+/-0.3). The
best-fitting absorption column is 5.6 (+2.0, -1.6) x 10^21 cm^-2, in
excess of the Galactic value of 3.5 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 3.6 x 10^-11 (7.4 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 5.6 (+2.0, -1.6) x 10^21 cm^-2
Galactic foreground: 3.5 x 10^21 cm^-2
Excess significance: 2.1 sigma
Photon index: 2.3 (+/-0.3)
If the light curve continues to decay with a power-law decay index of
0.64, the count rate at T+24 hours will be 6.2 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.2 x
10^-13 (4.6 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00609885.
This circular is an official product of the Swift-XRT team.
GCN Circular 16717
Subject
GRB 140818B: Swift/UVOT Upper Limits
Date
2014-08-19T13:10:44Z (11 years ago)
From
Lea Hagen at PSU <lea.zernow.hagen@gmail.com>
L. M. Z. Hagen (PSU) and A. Vargas (PSU)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 140818B
114 s after the BAT trigger (Vargas et al., GCN Circ. 16709). No optical
afterglow consistent with the XRT position (Beardmore et al. GCN Circ.
16712), the OSN candidate (Aceituno et al. GCN Circ 16711), or the GROND
candidate (Knust et al. GCN Circ 16713) is detected in the initial UVOT
exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early
exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 113 5136 530 >21.32
v 654 5546 254 >19.28
b 581 4931 235 >20.11
u 325 6007 506 >20.17
uvw1 704 5956 416 >19.92
uvm2 5551 5751 196 >19.53
uvw2 803 5341 235 >19.97
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.70 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 16718
Subject
GRB 140818B : Correction to GCN 16713
Date
2014-08-19T13:15:25Z (11 years ago)
From
Karla Varela at MPE <kvarela@mpe.mpg.de>
F. Knust, K. Varela, and J. Greiner (all MPE Garching) report on behalf of
the GROND team:
The afterglow candidate reported in GCN 16713 is the same as the one
reported by Aceituno et al. (GCN 16711) located at the edge of the 1.9
arcsec XRT error circle at:
RA (J2000): 18:04:32.47
Dec (J2000): -01:23:09.7
The GROND i�-band magnitude suggests it has decayed by about 2 magnitudes
within 3.5 hours, thus confirming this source to be the afterglow of GRB
140818B.
The magnitudes of the second source reported correspond to a source at the
edge of the 3.9 arcsec XRT error circle at :
RA (J2000): 18:04:32.78
Dec (J2000): -01:23:08.43
We apologize for this mistake.
GCN Circular 16721
Subject
GRB 140818B, Swift-BAT refined analysis
Date
2014-08-19T19:08:38Z (11 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), A. Y. Lien (NASA/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (LANL)
A. Vargas (PSU) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 140818B (trigger #609885)
(Vargas, et al., GCN Circ. 16709). The BAT ground-calculated position is
RA, Dec = 271.168, -1.354 deg which is
RA(J2000) = 18h 04m 40.2s
Dec(J2000) = -01d 21' 14.3"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 39%.
The mask-weighted light curve shows a single-peaked structure starts at ~T-4 sec and
peaks at ~ T+1 sec. The main pulse ends at ~T+2 sec, with some weak emission lasting
till ~T+18 sec. T90 (15-350 keV) is 18.1 +- 5.0 sec (estimated error including systematics).
The time-averaged spectrum from T-3.5 to T+18.1 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.99 +- 0.25. The fluence in the 15-150 keV band is 5.4 +- 0.8 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.31 sec in the 15-150 keV band
is 1.1 +- 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/609885/BA/
GCN Circular 16728
Subject
GRB 140818B: ISON-Kislovodsk and ISON-Burakan optical upper limit
Date
2014-08-20T14:50:32Z (11 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
A. Pozanenko (IKI), E. Romas (ISON), V. Nevskiy (ISON), G. Ohanian
(Byurakan Astrophisical Observatory), H. Andreasyan (Byurakan
Astrophisical Observatory), A. Volnova (IKI), I. Molotov (KIAM),
report on behalf of larger collaboration:
We observed the field of GRB 140818B (Vargas et al., GCN 16709) with
Santel-400AN telescope of ISON-Kislovodsk observatory starting on (UT)
18:54:36 and ISON-Burakan ORI-40 starting on (UT) 18:55:08. In the
enhanced XRT position (Beardmore et al., GCN 16712) we do not detect
optical afterglow candidate (Aceituno et al., GCN 16711; Knust et al.,
GCN 16713) neither in the first image nor in the stacked images.
Preliminary photometry is based on nearby USNO-B1.0 stars, R2 magnitudes:
Date UT start t-T0 Filter Exp. UL(3 sigma) Observatory
(mid, days) (s)
2014-08-18 18:54:36 0.0198 None 7*100 19.0 Kislovodsk
2014-08-18 18:55:08 0.0174 None 21*60 18.5 Burakan
GCN Circular 16748
Subject
GRB 140818B: TLS observations
Date
2014-08-27T09:23:17Z (11 years ago)
From
Sebastian Schmidl at TLS Tautenburg <schmidl@tls-tautenburg.de>
S. Schmidl, S. Klose, D. A. Kann, U. Laux, L. Pfeifer, C. Pohl, and H.
Meusinger (all TLS Tautenburg) report:
We observed the field of GRB 140818B (Swift trigger 609885, Vargas et al.,
GCN 16709) with the 1.34m Tautenburg Schmidt telescope.
Starting at 20:34 UT (1.83 hr after the trigger), we obtained in total 12
x 120s Rc-band images. Observations were obtained at a mean airmass of 1.75.
In a stack of all available images, we detect the source reported by
Aceituno et al. (GCN 16711). Using USNO-B1 field stars for calibration, we
derive a preliminary magnitude (Vega magnitude system) of
Rc = 20.9 +/- 0.2,
at a midtime of 2.08 hr after the burst.
The given magnitude is not corrected for the large Galactic foreground
extinction corresponding to a reddening of E_(B-V) = 0.73 mag in the
direction of the burst (Schlegel et al. 1998).
GCN Circular 16757
Subject
GRB140818B, the review of the sky area in plate archives
Date
2014-08-30T19:39:14Z (11 years ago)
From
Valentyna Golovnya at Main Astro Obs,Kyiv <golov_v@ukr.ne>
V.V. Golovnya (Main Astro Obs, Kyiv)
report:
We have undertaken the review of the sky area in vicinity of
GRB140818B (Vargas et al., GCN 16709; Beardmore et al.,
GCN 16712) on astronegatives, collected in Ukrainian NAS
Main astronomical observatory plate archive (1976-1996).
All the plates with the possible object appearance are
digitized using Microtek ScanMaker 9800XL TMA and Epson Expression 10000XL flatbed scanners and have been
placed into Golosiiv Plate Archive database DBGPA with open
access to them.��The list of plates is given in the table:
yyyymmdd/TimeUT --Plates--�������������������������� Exp.��LM����USNOA2 0825
19910613/222704��GUA040C001802A��22.5��15.9���� -11812892
19910709/205250��GUA040C001826A��23.5��15.7���� -11814106
19820715/175441��TAS040A000284������ 23.0��17.3�� ��-11812584
�� No any object has been found in the point with the mentioned
coordinates of GRB. But the image of some object have��found near GRB position on the two of selected plates.
Brighness of the object is estimated as V=15.0 and V=16.5:
�� Plates���������������������������������� ��RA,(J2000.0),Dec��������������������V
GUA040C001802A 18:04:32.08 -01:22:57.0 15.0
TAS040A000284���� ��18:04:32.63 -01:22:55.6 16.5
Plates:��
GUA040C���the plates archive identifier of DWA (D/F=400/2000,
���������������� M=103"/mm) of the Ukrainian NAS Main Astro obs.
���������������� (Marsden's number - 83) the plate number [1].
TAS040A -the plates archive identifier of DAZ (D/F=400/3000,
���������������� M=68.8"/mm) of the Tashkent Astro obs.
���������������� (Marsden's number - 186) the plate number [1].
Exp.���� - Duration of the maximum exposure (minutes).
LM - Limited V mag, derived in the 2,5 arcmin area around
������������ the location given in GCN Circ.16712:
������������ RA(J2000): 18h 04m 32.53s, Dec(J2000): -01d 23' 10.6"
USNOA2 - Comparison star.
�� The preview images of 3 areas together with��
the 2,5x2,5 min.of arc area from SkyMap can be found in��
http://gua.db.ukr-vo.org/img/grb/140818B/index.html
The images with full resolution are available via e-mail on
demand.
References:
1.L.Pakuliak DATABASE of GOLOSIIV PLATE ARCHIVE (DBGPA V2.0), http://gua.db.ukr-vo.org
GCN Circular 16780
Subject
GRB 140818B: TShAO optical upper limit
Date
2014-09-05T06:16:20Z (11 years ago)
From
Alexei Pozanenko at IKI <alex@grb.rssi.ru>
A. Pozanenko (IKI), I. Rewa, W. Mundrzyjewski, A. Kusakin (Fesenkov Astrophysical Institute), A. Volnova (IKI), report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 140818B (Vargas et al., GCN 16709)with Zeiss-1000 (East) telescope of Tien Shan Astronomical Observatory starting on Aug. 19, (UT) 17:05. We took several images in R-filter. Within enhanced XRT error circle (Beardmore et al., GCN 16712) we do not detect the afterlow (Aceituno et al., GCN 16711; Knust et al., GCN 16713). The source mentioned by Knust et al. (GCN 16713) is clearly visible in a stacked image in coordinates (J2000) 18:04:32.76 -01:23:08.9 (uncertainty is 0.2 arcsec in both coordinates) and has brightness of R=22.1+/-0.1.
Details of a photometry of the stacked image are following
Date UT start t-T0,d Exp,s Filter Up_Lim (3 sigma)
(mid)
2014-08-19 16:11:12 0.9317 20*600 R 22.9
The photometry is based on nearby USNO-B1.0 stars, R2 magnitudes.