GRB 121027A
GCN Circular 13937
Subject
GRB 121027A: sub-mm upper limit
Date
2012-11-01T15:32:19Z (13 years ago)
From
Jochen Greiner at MPI <jcg@mpe.mpg.de>
J. Greiner (MPE Garching), A. Belloche, T. Csengeri, F. Wyrowski
(all MPIfR Bonn), F. Schuller, F. Montenegro (both APEX, ESO),
V. Sudilovsky, J. Elliott (both MPE Garching),
D. A. Kann (MPE Garching/Universe Cluster),
A. de Ugarte Postigo (IAA-CSIC Granada/DARK Copenhagen),
T. Kruehler (DARK Copenhagen) report:
We observed the afterglow of the peculiar GRB 121027A (Starling et al. 2012,
GCN 13911; Levan et al. 2012, GCN 13920; Evans et al. 2012, GCN 13921) with
LABOCA/APEX at 870 micron. The observations in photometry mode started on
Oct. 31, 7:57 UT, 4.02 days after the Swift trigger (Evans et al. 2012,
GCN 13906, Barthelmy et al. 2012, GCN 13910). They were performed under
good weather conditions (pwv ~ 1 mm), and lasted for 1 hr.
No source is detected, down to a 3 sigma upper limit of 21 mJy/beam.
GCN Circular 13932
Subject
GRB 121027A: Swift/UVOT Possible Detection
Date
2012-10-30T17:59:26Z (13 years ago)
From
Frank Marshall at GSFC <femarsha@khamseen.gsfc.nasa.gov>
F. E. Marshall (NASA/GSFC) and P. A. Evans (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 121027A
77 s after the BAT trigger (Evans et al., GCN Circ. 13906).
A source consistent with the XRT position (Beardmore et al. GCN Circ. 13916)
and the nIR position (Starling et al. GCN Circ. 13911)
is weakly detected in the initial UVOT exposures.
The preliminary detection and 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 77 1192 353 21.55 +/- 0.25
v 619 1239 75 >19.5
b 544 1167 58 >19.7
u 289 1143 285 >20.6
w1 668 1118 58 >19.8
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 13930
Subject
GRB 121027A: X-shooter redshift confirmation
Date
2012-10-30T09:05:32Z (13 years ago)
From
Thomas Kruehler at Dark Cosmology Center <tom@dark-cosmology.dk>
T. Kruehler (DARK), N. R. Tanvir (U. Leicester), A. de Ugarte Postigo (IAA-CSIC and DARK/NBI),
D. Malesani (DARK), J. Fynbo (DARK), A. Melandri (INAF-OAB), A. J. Levan (U. Warwick),
K. Wiersema (U. Leicester), S. Schulze (PUC and MCSS), P. Goldoni (APC,CEA/Irfu),
H. Flores (Obs. Paris) and L. Kaper (U. Amsterdam) report on behalf of a larger collaboration:
We observed the optical/NIR counterpart (Starling et al. GCN 13911,
Levan et al. GCN 13920, Sudilovsky et al. GCN 13926) of GRB 121027A
(Evans et al. GCN 13906) with the VLT/X-shooter spectrograph,
beginning at Oct 30 2012 04:52 UT, which is 2.89 days after the GRB.
We identify emission lines of [OIII]4959 and [OIII]5007, and several absorption
lines of CIV, AlII, AlIII, MgI, MgII and FeII at a common redshift of z=1.773. This
confirms the provisional redshift given in Tanvir et al. (GCN 13929) for this GRB.
We note that the afterglow remains remarkably bright at 2.9 days post burst.
From the photometry of the acquisition image, we measure R = 21.15 +- 0.05
assuming R = 15.96 for the USNO star 0311-0027010 at RA = 04:14:21.83,
Dec = -58:50:28.8.
We thank the VLT staff, in particular Linda Schmidtobreick and
Myriam Rodrigues, for their assistance in obtaining these data,
and acknowledge J. Elliott for private information about the transient brightness.
GCN Circular 13929
Subject
GRB 121027A - Gemini South spectroscopy
Date
2012-10-29T23:01:55Z (13 years ago)
From
Nial Tanvir at U.Leicester <nrt3@star.le.ac.uk>
N. R. Tanvir, K. Wiersema (U. Leicester), A. J. Levan (U. Warwick),
R. L. C. Starling (U. Leicester), S. Margheim, T. Hayward (Gemini) report:
We observed the counterpart of GRB 121027A (Starling et al.
GCN 13911; Levan et al. GCN 13920; Sudilovsky et al. GCN13926 )
with the GMOS-S spectrograph at Gemini-South, beginning at
Oct 29 2012 05:42 UT. The spectrum covers a wavelength range of
roughly 5200A to 7900A, and was obtained in rather
poor conditions. Our provisional reduction shows a generally featureless
trace, with only one significant absorption feature, at about 7770A.
If we identify this feature with the MgII doublet at 2796/2803A
(the poor S/N and low resolution make it unclear whether or not the
observed line is a doublet), it would imply a redshift of z=1.77.
Whilst this is perhaps the most likely identification, further observations
are encouraged to test this possibility.
GCN Circular 13926
Subject
GRB 121027A: GROND Confirmation of Rebrightening
Date
2012-10-29T19:48:09Z (13 years ago)
From
Alexander Kann at TLS Tautenburg <kann@tls-tautenburg.de>
V. Sudilovsky (MPE Garching), D. A. Kann (MPE Garching/Universe Cluster),
T. Kr�hler (DARK, Copenhagen), and J. Greiner (MPE Garching) report on
behalf of the GROND team:
Following two days of bad weather delay, we observed the field of GRB
121027A (Evans et al., GCN 13906) simultaneously in g'r'i'z'JHK with GROND
(Greiner et al. 2008, PASP, 120, 405) mounted on the 2.2 m MPG/ESO
telescope at La Silla Observatory (Chile).
Observations began at 08:10 on October 29th (mid-time ~2.05 days
post-trigger). They were performed at an average seeing of 1.6" (r'-band)
and at an average airmass of 1.2.
We detect the NIR afterglow reported by Starling et al. (GCN 13911) and
Levan et al. (GCN 13920) in all seven bands.
Based on a 460 sec integration in g'r'i'z' and 1200 sec integration in
JHK, we measure preliminary magnitudes (all in AB system) of
g' = 22.1 +/- 0.2 mag
r' = 21.6 +/- 0.1 mag
i' = 21.3 +/- 0.1 mag
z' = 20.9 +/- 0.1 mag
J = 20.4 +/- 0.1 mag
H = 19.7 +/- 0.1 mag
K = 19.0 +/- 0.1 mag
We note an increase of brightness by ~ 1 magnitude relative to the
observations reported by Levan et al. (GCN 13920) at 32 hours after the
GRB.
Our detection in all bands constrains the redshift of this burst to z < 3.5.
Given magnitudes are calibrated against GROND zeropoints in the optical,
and 2MASS field stars in the NIR, and are not corrected for the expected
Galactic foreground extinction corresponding to a reddening of E(B-V) =
0.02 mag in the direction of the burst (Schlegel et al. 1998).
GCN Circular 13922
Subject
GRB 121027A: MASTER early prompt optical limit
Date
2012-10-29T11:09:57Z (13 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <gcncirc@observ.inetcomm.ru>
H. Levato and C. Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
C. Mallamaci, C. Lopez and F. Podest
Observatorio Astronomico Felix Aguilar (OAFA)
E. Gorbovskoy, V. Lipunov, V. Kornilov, D. Denisenko, A. Kuznetsov,
D. Kuvshinov, A. Belinski, N. Tyurina, N. Shatskiy, P. Balanutsa, D. Zimnukhov,
V.V. Chazov
Lomonosov Moscow State University, Sternberg Astronomical Institute
A. Tlatov, A.V. Parhomenko, D. Dormidontov, V. Sennik
Kislovodsk Solar Station of the Pulkovo Observatory
K. Ivanov, S. Yazev, N.M. Budnev, O. Gres, O. Chuvalaev, V.A. Poleshchuk
Irkutsk State University
V. Yurkov, Yu. Sergienko, D. Varda, E. Sinyakov
Blagoveschensk Educational State University, Blagoveschensk
V. Krushinski, I. Zalozhnich, A. Popov, A. Bourdanov
Ural Federal University
MASTER-ICATE robotic Very Wide Field Cameras (FOV=2x384 square degrees,
D=72mm, f/1.2, 1 pix = 22 arcsec, http://observ.pereplet.ru) located in
Argentina (Observatorio Astronomico Felix Aguilar,
http://93.180.27.230:8080/) were pointed to the GRB 121027A by Swift
trigger (Evans et al., GCNC 13906) 85 s after GRB time at
2012-10-27 07:33:54 UT.
We haven`t found optical transient within Swift XRT
error-box on our first (1 s exposure) set and on coadd image
with complete exposure
of 11 seconds during gamma-burst activity (Barthelmy et al., GCN 13910).
The 5-sigma upper limit on unfiltered (with respect to Tyho V mag) single
image has been about 11.0 mag and 11.7 mag on coadded image.
The automatic photometry is:
Date time Exp.time Limit
Coadd
2012-10-27 07:33:54 11 11.7
2012-10-27 07:35:05 41 12.2
2012-10-27 07:37:25 7 11.2
2012-10-27 07:38:16 80 11.7
2012-10-27 07:44:18 17 11.2
2012-10-27 07:45:18 75 12.2
2012-10-27 07:50:38 11 11.6
2012-10-27 07:51:03 26 12.1
2012-10-27 07:51:56 30 12.2
Our cameras are continuously imaging the sky with 1 sec exposures without
time gap.
This message can be cited.
GCN Circular 13921
Subject
GRB 121027A: Swift-XRT refined Analysis
Date
2012-10-29T09:29:21Z (13 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P. A. Evans, K.L. Page and J.P. Osborne (U Leicester) report on behalf
of the Swift-XRT team:
We have analysed 12 ks of XRT data for GRB 121027A (Evans et al. GCN
Circ. 13906), from 57 s to 76.2 ks after the BAT trigger. The data
comprise 2.0 ks in Windowed Timing (WT) mode (the first 9 s were 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 13916).
This burst is unusual in showing multiple strong rebrightenings at high
flux in X-rays, a rebrightening has also reported in the IR (Levan et
al GCN 13920). This behaviour is reminiscent of the tidal disruption
event Swift J1644.
The light curve initially follows a power-law decay with an index of
alpha~1.8. This is interrupted by a flare beginning at T+220 s and
lasting ~300 s, after which the decay appears much steeper: alpha~6.6.
However at T+800 s the count rate jumps sharply, increasing by more
than 2 orders of magnitude in under 300 s; by T+1.1 ks the count rate
is ~30 ct/sec, corresponding to an observed flux of ~1e-9 erg/cm^2/s.
At this point the GRB left Swift's observing window, however during the
next observation (T+5.3 ks to T+6ks) the count rate remained high,
increasing from ~20 ct/s at the start of the observation to ~60 ct/s at
the end. The MAXI observation (GCN 13908) occurred between these
observations, and the flux reported by MAXI is consistent with the
Swift flux of ~1-2 e-9 erg cm^2/s. Over the next 4 exposures (T+11 ks
to T+30 ks), the count-rate declines with an index of ~3.8 to a level
of ~0.08 ct/s, it then remains at that level until T+76 ks, where our
current observations end. The hardness ratio follows the count-rate
during the rebrightenings (i.e. the emission is harder when brighter),
which is typical of flaring activity.
A spectrum formed from the first observation in WT mode data can be
fitted with an absorbed power-law with a photon spectral index of 2.55
(+/-0.06). The best-fitting absorption column is 2.80 (+0.16, -0.15) x
10^21 cm^-2, in excess of the Galactic value of 1.5 x 10^20 cm^-2
(Kalberla et al. 2005). The PC mode spectrum has a photon index of 1.94
(+0.29, -0.27) and a best-fitting absorption column of 1.1 (+0.7, -0.6)
x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum is 3.8 x 10^-11 (4.8 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.1 (+0.7, -0.6) x 10^21 cm^-2
Galactic foreground: 1.5 x 10^20 cm^-2
Excess significance: 2.5 sigma
Photon index: 1.94 (+0.29, -0.27)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00536831.
Multi-wavelength follow-up is strongly recommended.
This circular is an official product of the Swift-XRT team.
GCN Circular 13920
Subject
GRB 121027A: Brightening IR counterpart
Date
2012-10-29T08:36:06Z (13 years ago)
From
Andrew Levan at U.of Leicester <A.J.Levan@warwick.ac.uk>
A.J. Levan (U. Warwick), R.Starling, N.R. Tanvir, K. Wiersema (U.
Leicester), A. R. Lopez-Sanchez (AAO/Macquarie University), T. Young
(ANU), K. Glazebrook (Swinburne), L. Spitler (Macquarie University/AAO),
and S. Lee (AAO) report:
"We observed the candidate afterglow of GRB 121027A (Evans et al.
GCN 13906; Starling et al. GCN 13916) with the Anglo Australian
Telescope for a second epoch on the night of 28 October 2012. The
second epoch was obtained ~32 hours after the burst, and 26 hours
after the first epoch reported in Starling et al. (GCN 13916). We
clearly detect the afterglow candidate, and find that it has
brightened by approximately 1 magnitude in the K-band between the
two epochs. This confirms it as the infrared afterglow of GRB
121027A. We note that rising behaviour in the IR over this time
period is extremely unusual, and given the extremely bright, and
long lived X-ray afterglow (e.g. Serino et al. GCN 13908) could be
indicative of an event similar in nature to Swift J1644+57."
GCN Circular 13916
Subject
GRB 121027A: Enhanced Swift-XRT position
Date
2012-10-29T00:49:15Z (13 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 661 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 121027A, 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 = 63.59738, -58.82962 which is equivalent
to:
RA (J2000): 04h 14m 23.37s
Dec (J2000): -58d 49' 46.6"
with an uncertainty of 2.0 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 13911
Subject
GRB 121027A: nIR afterglow candidate with AAT
Date
2012-10-27T20:11:13Z (13 years ago)
From
Rhaana Starling at U of Leicester <rlcs1@star.le.ac.uk>
R.L.C. Starling (U. Leicester), A.J. Levan (U. Warwick), K. Wiersema (U. Leicester), A.R. Lopez-Sanchez (AAO/Macquarie
+University), N.R. Tanvir (U. Leicester), T. Young (ANU), L. Spitler (Macquarie University/AAO) and S. Lee (AAO) report:
We triggered near-infrared observations with IRIS2 on the Anglo-Australian Telescope for GRB 121027A, beginning ~3.5 hours
+after the Swift BAT trigger (Evans et al. GCN Circ. 13907).
The field was observed for 2x10 minutes in each of J, H and K bands. In a preliminary analysis of the K band data (beginning
+13:49 UT) we clearly detect a source within the enhanced XRT error circle (www.swift.ac.uk/sper/536831) at position:
RA 04 14 23.44
Dec -58 49 47.4 (J2000)
with approximate magnitude K(AB)=21.10 +/- 0.13.
The source is not discernable from the J and H band images. These, however, do not go as deep owing to variable weather
+conditions; the limiting magnitude in H(AB) is 21.3 (3-sigma, beginning 13:22 UT).
These data were obtained under programme AAT/12B/30.
[GCN OPS NOTE(28oct12): Per author's request, ALG was changed to ARL-S in the author list.]
GCN Circular 13910
Subject
GRB 121027A: Swift-BAT refined analysis
Date
2012-10-27T14:44:48Z (13 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),
P. A. Evans (U Leicester), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), G. Sato (ISAS), M. Stamatikos (OSU),
J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
Using the data set from T-61 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 121027A (trigger #536831)
(Evans, et al., GCN Circ. 13906 (not 13907)). The BAT ground-calculated position is
RA, Dec = 63.598, -58.839 deg, which is
RA(J2000) = 04h 14m 23.5s
Dec(J2000) = -58d 50' 21.3"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 80%.
The mask-weighted light curve shows a FRED with two small peaks on the tail,
starting at ~T-9 sec, peaking at ~T+3 sec, with a long tail out to
~T+105 sec (or possibly to ~T+165 sec). T90 (15-350 keV) is 62.6 +- 4.8 sec
(estimated error including systematics).
The time-averaged spectrum from T-9.34 to T+65.33 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.82 +- 0.09. The fluence in the 15-150 keV band is 2.0 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+2.00 sec in the 15-150 keV band
is 1.3 +- 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/536831/BA/
GCN Circular 13908
Subject
GRB 121027A: MAXI/GSC detection 40 minutes after the Swift Trigger
Date
2012-10-27T09:51:02Z (13 years ago)
From
Motoko Suzuki at RIKEN <motoko@crab.riken.jp>
M. Serino (RIKEN), S. Nakahira (JAXA), N. Negoro, M. Asada (Nihon U.),
K. Yamaoka (ISAS), S. Ueno, H. Tomida, M. Ishikawa (JAXA),
T. Mihara, M. Sugizaki, T. Yamamoto, J. Sugimoto, M. Matsuoka (RIKEN),
N. Kawai, M. Morii, R. Usui, K. Ishikawa, T. Yoshii (Tokyo Tech),
A. Yoshida (AGU), H. Tsunemi, M. Kimura (Osaka U.),
M. Nakajima (Nihon U.),
Y. Ueda, K. Hiroi, M. Shidatsu, R. Sato (Kyoto U.),
Y. Tsuboi, M. Higa (Chuo U.)
M. Yamauchi, Y. Nishimura, T. Hanayama, K. Yoshidome (Miyazaki U.)
report on behalf of the MAXI team:
At 2012-10-27T08:12:53UT, the MAXI/GSC nova alert system triggered on a
bright uncatalogued X-ray transient source.
The transient emission lasted at least 38 seconds within the 41 second
long triangular transit response of MAXI/GSC.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (63.75 deg, -58.68 deg) = (04:15:00, -58:40:59)(J2000)
with a 90% C.L. statistical error of 0.43 deg and an additional systematic
uncertainty of 0.1 deg (90% containment radius).
The 4-10 keV flux was ~150 mCrab.
The position is consistent with GRB 121027A (GCN 13906, 13907),
so we identify the source is GRB 121027A observed 40 minutes after
the Swift Trigger.
There was no significant excess flux in the previous transit at 06:40 UT
(92 min before the trigger time) with an upper limit of 20 mCrab.
GCN Circular 13906
Subject
GRB 121027A: Swift detection of a burst
Date
2012-10-27T07:55:18Z (13 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P. A. Evans (U Leicester), C. Gronwall (PSU),
H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (NASA/GSFC),
K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of
the Swift Team:
At 07:32:29 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 121027A (trigger=536831). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 63.610, -58.801 which is
RA(J2000) = 04h 14m 26s
Dec(J2000) = -58d 48' 04"
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 80 sec. The peak count rate
was ~2000 counts/sec (15-350 keV), at ~3 sec after the trigger.
The XRT began observing the field at 07:33:37.0 UT, 67.4 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
63.5977, -58.8298 which is equivalent to:
RA(J2000) = 04h 14m 23.44s
Dec(J2000) = -58d 49' 47.2"
with an uncertainty of 2.5 arcseconds (radius, 90% containment). This
location is 106 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 1.50
x 10^20 cm^-2 (Kalberla et al. 2005).
The initial flux in the 2.5 s image was 6.10e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 250 seconds with the U filter starting
288 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 19.2 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 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.02.
Due to the maintenance work at Goddard this weekend (GCN 13905) there
may be a delay in receiving the full dataset, and thus refined
analyses may not be available until late Sunday/early Monday.
Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.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.)