GRB 180905A
GCN Circular 23201
Subject
GRB 180905A: Swift detection of a burst
Date
2018-09-05T14:07:32Z (7 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
V. D'Elia (SSDC), A. D'Ai (INAF-IASFPA), J.D. Gropp (PSU),
J. A. Kennea (PSU), M. J. Moss (George Washington University),
K. L. Page (U Leicester), D. M. Palmer (LANL) and B. Sbarufatti (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:
At 13:57:46 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180905A (trigger=859421). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 91.035, -4.591 which is
RA(J2000) = 06h 04m 08s
Dec(J2000) = -04d 35' 27"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). As is usual for an image trigger, no obvious
variation is visible in the immediately-available lightcurve.
The XRT began observing the field at 14:00:12.3 UT, 145.9 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 91.0602, -4.5724 which is equivalent to:
RA(J2000) = 06h 04m 14.45s
Dec(J2000) = -04d 34' 20.6"
with an uncertainty of 5.1 arcseconds (radius, 90% containment). This
location is 112 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 2.5 s image was 2.03e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 135 seconds with the White filter
starting 153 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
0.60.
Burst Advocate for this burst is V. D'Elia (delia AT ssdc.asi.it).
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 23207
Subject
GRB 180905A: Enhanced Swift-XRT position
Date
2018-09-05T18:09:33Z (7 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 1840 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 180905A, 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 = 91.06265, -4.57015 which is equivalent
to:
RA (J2000): 06h 04m 15.04s
Dec (J2000): -04d 34' 12.6"
with an uncertainty of 1.8 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 23208
Subject
GRB 180905A: BOOTES-3/YA optical observations
Date
2018-09-05T20:41:11Z (7 years ago)
From
Youdong HU at IAA-CSIC, UGR <youdong@iaa.es>
Y.-D. Hu, E. Fernandez-Garcia, J. C. Tello, A. Ayala and A. J.
Castro-Tirado (IAA-CSIC), I. Carrasco and C. Perez del Pulgar (Univ. de
Malaga), M. D. Caballero-Garcia (ASU-CAS, CZ) and R. Querel (NIWA), on
behalf of a larger collaboration, report:
The 60cm BOOTES-3/YA robotic telescope at NIWA Lauder in Otago (New
Zealand) automatically responded to the Swift trigger of GRB 180905A
(D'Elia et al. GCNC 23201) ~0.55 h after the burst as soon as it became
few degrees above the horizon. The first image (clear filter) were
obtained starting at 14:30:52 UT. At the position of the Swift/XRT
enhanced X-ray position (Beardmore et al. GCNC 23207), no optical
afterglow is detected down to 20 mag on a 720s co-added image at
14:38:31 (mid-exposure), in agreement with the non-detection by
Swift/UVOT.
Further analysis is ongoing.
We thank the staff at NIWA for its excellent support.
GCN Circular 23210
Subject
GRB 180905A: Swift-XRT refined Analysis
Date
2018-09-06T02:40:59Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A.P. Beardmore (U. Leicester), P. D'Avanzo (INAF-OAB), A. D'Ai
(INAF-IASFPA), D.N. Burrows (PSU), A. Tohuvavohu (PSU), S. J. LaPorte
(PSU), P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester) and V.
D'Elia report on behalf of the Swift-XRT team:
We have analysed 9.0 ks of XRT data for GRB 180905A (D'Elia et al. GCN
Circ. 23201), from 152 s to 35.0 ks after the BAT trigger. The data
comprise 135 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Beardmore et al. (GCN Circ. 23207).
The light curve can be modelled with a power-law decay with a decay
index of alpha=1.556 (+0.029, -0.027).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.45 (+0.11, -0.10). The
best-fitting absorption column is 5.7 (+1.1, -1.0) x 10^21 cm^-2, in
excess of the Galactic value of 3.5 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.68 (+0.28, -0.26)
and a best-fitting absorption column of 5.5 (+2.2, -1.8) 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 (6.9 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 5.5 (+2.2, -1.8) x 10^21 cm^-2
Galactic foreground: 3.5 x 10^21 cm^-2
Excess significance: 1.8 sigma
Photon index: 1.68 (+0.28, -0.26)
If the light curve continues to decay with a power-law decay index of
1.556, the count rate at T+24 hours will be 1.8 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.9 x
10^-14 (1.2 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/00859421.
This circular is an official product of the Swift-XRT team.
GCN Circular 23211
Subject
GRB 180905A: MITSuME Akeno optical upper limits
Date
2018-09-06T05:53:52Z (7 years ago)
From
Katsuhiro L. Murata at Nagoya U <murata@u.phys.nagoya-u.ac.jp>
M. Niwano, R. Itoh, K. L. Murata, Y. Tachibana, S. Harita, K. Morita,
K. Shiraishi, K. Iida, R. Adachi, M. Oeda,
Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We searched for the optical counterpart of GRB 180905A
(V. D'Elia et al., GCN Circular #23201)
with the optical three color (g', Rc, and Ic) CCD cameras attached to
the MITSuME 50cm telescope of Akeno Observatory, Yamanashi, Japan.
The observation started on 2018-09-05 17:29:51.08 UT.
We did not find any point source at the enhanced position of the
XRT error circle (A.P. Beardmore et al., GCN Circular #23207) in all three
bands.
We obtained following 5-sigma upper limits for the magnitudes.
T0+[min] MID-UT T-EXP[sec] g' Rc Ic
-------------------------------------------------------------------------------------------------------
202.32 18:46:39 8,100 >18.9 >18.6 >18.4
-------------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used UCAC-4 catalog for flux calibration.
GCN Circular 23212
Subject
GRB 180905A: RATIR Optical and NIR Observations
Date
2018-09-06T13:30:04Z (7 years ago)
From
Alan M. Watson at Instituto de Astronomia UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC),
William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J.
Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz
(UCSC), Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey
Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki
Toy (UMD) report:
We observed the field of GRB 180905A (D'Elia et al., GCN Circ. 23201)
with the Reionization and Transients Infrared Camera (RATIR;
www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio
Astron��mico Nacional on Sierra San Pedro M��rtir from 2018/09 6.42 to
2018/09 6.51 UTC (20.07 to 22.23 hours after the BAT trigger), obtaining
a total of 1.17 hours exposure in the r and i bands and 0.57 hours
exposure in the Z, Y, J, and H bands.
For a source within the Swift-XRT enhanced error circle (Beardmore et
al., GCN Circ. 23207), in comparison with the USNO-B1 and 2MASS
catalogs, we obtain the following upper limits (3-sigma):
r > 23.26
i > 23.10
Z > 22.21
Y > 22.06
J > 21.60
H > 21.25
These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.
GCN Circular 23213
Subject
GRB 180905A, Swift-BAT refined analysis
Date
2018-09-06T16:12:08Z (7 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
T. Sakamoto (AGU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), V. D'Elia (SSDC),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+250 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180905A (trigger #859421)
(D'Elia et al., GCN Circ. 23201). The BAT ground-calculated position is
RA, Dec = 91.038, -4.592 deg which is
RA(J2000) = 06h 04m 09.2s
Dec(J2000) = -04d 35' 31.9"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 29%.
The mask-weighted light curve shows a weak long pulse that starts
at ~T-60 s and ends at ~T+150 s. Note that the burst came into the BAT
field of view at T-84 s, and BAT entered the SAA after ~ T+250 s. Therefore,
there might be additional burst emission before and after the available event
data range. T90 (15-350 keV) is 165.3 +- 28.9 sec (estimated error including
systematics).
The time-averaged spectrum from T-58.9 to T+146.7 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.60 +- 0.12. The fluence in the 15-150 keV band is 4.2 +- 0.3 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-2.09 sec in the 15-150 keV band
is 1.0 +- 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/859421/BA/
GCN Circular 23215
Subject
GRB 180905A: Swift/UVOT Upper Limits
Date
2018-09-09T19:37:38Z (7 years ago)
From
Mike Siegel at PSU/Swift MOC <siegel@swift.psu.edu>
M. H. Siegel (PSU) and V. D'Elia (SSDC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180905A
154 s after the BAT trigger (D'Elia et al., GCN Circ. 23201).
No optical afterglow consistent with the XRT position
(D'Elia et al. GCN Circ. 23201) is detected in the initial UVOT exposures,
as confirmed by Bootes (Hu et al., GCN Circ. 23208), MITSUME (Niwano
et al., GCN Circ. 23211) and RATIR (Watson et al., GCN Circ. 23212).
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 154 289 133 >20.4
white 154 6385 373 >21.1
v 5316 5515 197 >19.1
b 4700 6335 393 >20.5
u 4495 6130 393 >20.3
w1 5726 5925 197 >19.6
m2 5520 5720 197 >19.8
w2 5111 5311 197 >19.2
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.60 in the direction of the burst
(Schlegel et al. 1998).