GRB 131227A
GCN Circular 15616
Subject
GRB 131227A: Swift detection of a burst
Date
2013-12-27T05:09:45Z (11 years ago)
From
Mike Siegel at PSU/Swift MOC <siegel@swift.psu.edu>
S. R. Oates (UCL-MSSL), H. A. Krimm (CRESST/GSFC/USRA),
N. P. M. Kuin (UCL-MSSL) and M. H. Siegel (PSU) report on behalf of
the Swift Team:
At 04:44:51 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 131227A (trigger=582184). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 67.386, +28.864 which is
RA(J2000) = 04h 29m 33s
Dec(J2000) = +28d 51' 52"
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 ~2000 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 04:45:48.0 UT, 57 seconds
after the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source with an enhanced position: RA, Dec 67.3781,
28.8827 which is equivalent to:
RA(J2000) = 04h 29m 30.74s
Dec(J2000) = +28d 52' 57.9"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). 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 in excess of the Galactic value (1.53 x
10^21 cm^-2, Kalberla et al. 2005), with an excess column of 2.1
(+2.23/-1.94) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 6.01e-10 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 66 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
1.02.
Burst Advocate for this burst is S. R. Oates (samantha.oates AT ucl.ac.uk).
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 15617
Subject
GRB 131227A: OT candidate from KAIT Optical observations
Date
2013-12-27T07:06:02Z (11 years ago)
From
Weikang Zheng at UC Berkeley <zwk@astro.berkeley.edu>
WeiKang Zheng, Alexei V. Filippenko, Adam Morgan (UC Berkeley), and
S. B. Cenko (NASA/Goddard Space Flight Center) report on behalf of the
KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to GRB 131227A (Oates et al., GCN 15616)
starting at 04:47:49 UT, 178 s after the burst. Observations were
performed with an automatic sequence in the V, I, and clear(roughly R)
filters, and the exposure time was 20 s per image.
Within the XRT error circle, we detected a new faint source at
coordinate of (J2000):
Ra = 04:29:30.83, Dec= +28:52:58.81 (uncertainty about 1")
The object faded from mag ~18.6 to be below than 20.0 in our clear
band image about 10 minutes after (calibrated to USNO B1.0). We
suggest this is the OT of GRB 131227A. Further observations are
encouraged.
GCN Circular 15618
Subject
GRB 131227A: Enhanced Swift-XRT position
Date
2013-12-27T14:13:38Z (11 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans and M.R. Goad (U. Leicester) report
on behalf of the Swift-XRT team:
Using 4481 s of XRT Photon Counting mode data and 6 UVOT
images, 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 = 67.37825, 28.88310 which is equivalent to:
RA (J2000): 04 29 30.78
Dec (J2000): +28 52 59.2
with an uncertainty of 1.6 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 is an official product of the Swift-XRT team.
GCN Circular 15620
Subject
GRB 131227A: Swift-BAT refined analysis
Date
2013-12-27T15:00:28Z (11 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/UMBC),
C. B. Markwardt (GSFC), S. R. Oates (UCL-MSSL), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+651 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 131227A (trigger #582184)
(Oates, et al., GCN Circ. 15616). The BAT ground-calculated position is
RA, Dec = 67.369, 28.879 deg which is
RA(J2000) = 04h 29m 28.5s
Dec(J2000) = +28d 52' 44.3"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 90%.
The mask-weighted light curve shows several overlapping peaks starting
at ~T-2 sec, peaking at ~T+2 sec, and ending at ~T+22 sec with a long low-level
tail out to ~T+100 sec. T90 (15-350 keV) is 18.0 +- 1.6 sec (estimated error
including systematics).
The time-averaged spectrum from T-1.19 to T+19.23 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.36 +- 0.12. The fluence in the 15-150 keV band is 8.4 +- 0.6 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+1.61 sec in the 15-150 keV band
is 1.1 +- 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/582184/BA/
GCN Circular 15621
Subject
GRB 131227A: Swift/UVOT Upper Limits
Date
2013-12-27T15:55:33Z (11 years ago)
From
Massimiliano de Pasquale at MSSL-UCL <m.depasquale@ucl.ac.uk>
M. De Pasquale (UCL-MSSL) and S. R. Oates (UCL-MSSL)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 131227A
66 s after the BAT trigger (Oates et al. GCN Circ. 15616).
No optical afterglow consistent with the enhanced XRT position
(Evans et al. GCN Circ. 15618) or the source detected by KAIT (Zheng
et al. GCN 15617) 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 first
finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 66 216 147 >20.6
u_FC 278 528 246 >19.9
white 66 13019 1430 >21.9
v 608 6785 471 >19.7
b 534 12318 1160 >21.1
u 278 11406 1366 >20.9
w1 5558 7195 393 >20.1
w2 4942 6580 393 >20.5
The magnitudes in the table are not corrected for the strong Galactic
extinction due to the reddening of E(B-V) = 1.02 in the direction of
the burst (Schlegel et al. 1998).
GCN Circular 15622
Subject
GRB 131227A: Xinglong optical observations
Date
2013-12-27T16:02:49Z (11 years ago)
From
Dong Xu at DARK/NBI <dong.dark@gmail.com>
D. Xu (DARK/NBI), T.-M. Zhang, L.-P. Xin, F. Xiao (NAOC) report:
We observed the field of GRB 131227A (Oates et al., GCN 15616) using
the 2.16m Xinglong telescope, equipped with BFOSC and located in
Heibei, China. We obtained 2x600s R-band images with a mean time of
9.086 hr after the BAT trigger.
At the afterglow position (Zheng et al., GCN 15617), which is within
the XRT error circle (Evans & Goad, GCN 15618), the afterglow has
decayed to have R>21.2 mag, calibrated with nearby USNO B1 field.
GCN Circular 15623
Subject
GRB 131227A: Swift-XRT refined Analysis
Date
2013-12-27T17:09:04Z (11 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
V. D'Elia (ASDC), A. Maselli (INAF-IASFPA), M.C. Stroh (PSU), D.N.
Burrows (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), C. Pagani
(U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB)
and S.R. Oates report on behalf of the Swift-XRT team:
We have analysed 8.6 ks of XRT data for GRB 131227A (Oates et al. GCN
Circ. 15616), from 63 s to 18.8 ks after the BAT trigger. The data
comprise 1.8 ks in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. Using 4789 s of PC mode data and 7 UVOT
images, we find an enhanced XRT position (using the XRT-UVOT alignment
and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
67.37831, +28.88296 which is equivalent to:
RA (J2000): 04h 29m 30.80s
Dec(J2000): +28d 52' 58.7"
with an uncertainty of 1.4 arcsec (radius, 90% confidence).
The light curve can be modelled with a power-law decay with a decay
index of alpha=1.110 (+0.029, -0.028).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.28 (+0.22, -0.21). The
best-fitting absorption column is 4.4 (+0.9, -0.8) x 10^21 cm^-2, in
excess of the Galactic value of 1.5 x 10^21 cm^-2 (Kalberla et al.
2005). The PC mode spectrum has a photon index of 1.93 (+0.22, -0.21)
and a best-fitting absorption column of 4.9 (+1.2, -1.1) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 4.9 x 10^-11 (8.1 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 4.9 (+1.2, -1.1) x 10^21 cm^-2
Galactic foreground: 1.5 x 10^21 cm^-2
Excess significance: 5.3 sigma
Photon index: 1.93 (+0.22, -0.21)
If the light curve continues to decay with a power-law decay index of
1.110, the count rate at T+24 hours will be 3.6 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x
10^-13 (2.9 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/00582184.
This circular is an official product of the Swift-XRT team.
GCN Circular 15624
Subject
GRB 131227A: Gemini-North Redshift
Date
2013-12-27T18:44:22Z (11 years ago)
From
Antonino Cucchiara at NASA/GSFC <antonino.cucchiara@nasa.gov>
A. Cucchiara (ORAU/NASA-GSFC) and S.B. Cenko (NASA-GSFC)
report on behalf of a larger collaboration:
"On December 27.42 UT (~ 5.1 hr after the Swift trigger) we
began observing the afterglow of GRB 131227A (Oates et al.
GCN 15616, Zheng et al. GCN 15617) with the GMOS spectrograph
mounted on the Gemini-North telescope.
Under poor seeing conditions the afterglow was marginally
detected in our i�-band acquisition image.
Nevertheless, we performed a spectroscopic sequence of 2x900s
spectra with GMOS and the R400 grating, covering the 4400-8600A
wavelength range.
Clear evidence of continuum flux is detected beyond 7600A, while
no flux is present in either spectra nor in a coadded spectrum
blueward of this wavelength.
No other obvious emission or absorption features are present in
the spectrum, though the signal-to-noise ratio is not extremely
high.
If this break is due to Lyman-alpha, the implied GRB redshift
would be z~5.3.
We caution, however, that this line of sight is subject to high
galactic extinction (A_V= 2.8).
We thank the Gemini staff for performing these observations under
challenging conditions, in particular Marie Lemoine-Busserolle."
GCN Circular 15625
Subject
GRB 131227A: P60 Limits
Date
2013-12-27T19:05:01Z (11 years ago)
From
S. Bradley Cenko at Caltech <cenko@srl.caltech.edu>
S. B. Cenko (NASA/GSFC) and D. A. Perley (Caltech) report on behalf of a
larger collaboration:
We observed the location of the optical afterglow (Zheng et al., GCN
15617) of the Swift GRB 131227A (Oates et al., GCN 15616) with the robotic
Palomar 60 inch telescope. Observations were obtained in the r', i', and
z' filters beginning at 05:59 UT on 2013 Dec 27 (~ 1.24 hours after the
Swift trigger time). We do not detect any sources at the location of the
KAIT optical afterglow. Using nearby point sources from the USNO-B1
catalog for reference, we calculate an upper limit of r > 21.0 mag at a
mean epoch of 1.50 hr after the Swift trigger.
GCN Circular 15632
Subject
GRB 131227A: GROND Upper Limits
Date
2013-12-29T17:07:39Z (11 years ago)
From
Alexander Kann at TLS Tautenburg <kann@tls-tautenburg.de>
D. A. Kann (MPE Garching), A. Nicuesa Guelbenzu (TLS Tautenburg) and J.
Greiner (MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 131227A (Swift trigger 582184; Oates et al.,
GCN 15616) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2m MPG telescope at La Silla Observatory
(Chile).
Observations started at 02:10 UT on December 28th, around 21.4 hrs after
the GRB trigger, and lasted for 2 hours. They were performed at an average
seeing of 1".0 and at an average airmass of 2.
At the position of the optical afterglow reported by Zheng et al. (GCN
15617) and Cucchiara et al. (priv. comm., see also GCN 15624) we do not
detect any source down to 3-sigma AB limiting magnitudes of
g' > 25.7,
r' > 25.6,
i' > 24.8,
z' > 24.6,
J > 21.8,
H > 21.1, and
K > 19.7.
We do detect a compact source to the north-east, at
RA (J2000) = 04:29:30.90
Dec. (J2000) = +28:53:00.3
with an uncertainty of 0".3 and AB magnitudes
r' = 24.28 +/- 0.1,
i' = 24.19 +/- 0.1,
z' = 22.82 +/- 0.1, and
J = 20.66 +/- 0.4.
It is undetected to above-mentioned limits in the other filters. The
relationship of this source to the afterglow is unclear.
The given limits and magnitudes are derived based on calibrating the
images against GROND zeropoints in g'r'i'z' and 2MASS field stars in JHK
and are not corrected for the Galactic foreground extinction corresponding
to a reddening of E_(B-V)= 1.02 mag in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 15649
Subject
GRB 131227A: KAIT light curve analysis
Date
2014-01-01T20:55:53Z (11 years ago)
From
Weikang Zheng at UC Berkeley <zwk@astro.berkeley.edu>
WeiKang Zheng, Alexei V. Filippenko, Adam Morgan (UC Berkeley), and
S. B. Cenko (NASA/Goddard Space Flight Center) report on behalf of the
KAIT GRB team:
We analyzed the early time KAIT data of GRB 131227A (Oates et al., GCN
15616). The afterglow is easily detected in our clear and I band
images, but not in V band images (single or co-added). After correcting
for the large Galactic extinction (A_V = 2.8 mag, A_I = 1.5 mag;
Schlegel et al., 2011, ApJ, 737, 103), we found the afterglow had a
color of (V - I) > 1.2 mag at early times (~200 s - 900 s). This is
consistent with the spectral break around 7600 A reported by Cucchiara &
Cenko (GCN 15624), but still not so constraining to say the break is
caused by Lyman-alpha.
Due to lack of emission below 7600 A (either because of extinction
or Lyman-alpha break), we calibrated the KAIT clear image to the i'
band. Our preliminary result shows the afterglow decays as a power law
with alpha = -0.99. The late time upper limit reported by Kann et al.
(GCN 15632) is below the extrapolation of the line.
The preliminary light curve can be found at the following link:
http://128.32.15.133/kait/grb/131227A/GRB131227A.png