GRB 161104A
GCN Circular 20168
Subject
GRB 161104A: Magellan imaging and spectroscopy
Date
2016-11-11T02:15:11Z (9 years ago)
From
Wen-fai Fong at U of Arizona <wfong@email.arizona.edu>
W. Fong (University of Arizona) and R. Chornock (Ohio University) report:
We imaged the location of the short-duration GRB 161104A (Mingo et al., GCN
20213) with the Inamori-Magellan Areal Camera and Spectrograph (IMACS)
mounted on the Magellan/Baade 6.5-m telescope at a mid-time of 2016 Nov
7.170 UT (2.77 days post-burst). We obtained 6x360-sec of r-band exposures
in 1.0" seeing at an airmass of 1.3. We clearly detect the four optical
sources reported from GROND (Nicuesa Guelbenzu et al.; GCN 20132) and
Gemini (Troja et al.; GCN 20137) imaging. Given the relatively poor seeing,
accurate photometry of the individual sources is challenging. However, the
sources appear to have similar relative flux levels as previously reported,
suggesting a lack of significant variability in any of these sources. We
note that Source A (Nicuesa Guelbenzu et al.; GCN 20132) is fully
coincident with the latest XRT position*, while the three remaining sources
are on the outskirts of the position.
In addition, we obtained 3x1800-sec of spectroscopy with Magellan/IMACS on
2016 Nov 8 UT in 0.6" seeing at an airmass of 1.1. We used the 200 line
grism and the f/2 camera to cover 4000-10000 Angstroms. The slit was
aligned through Sources A and B (Nicuesa Guelbenzu et al.; GCN 20132) and
also serendipitously passed through a nearby extended source 6.1" from the
center of the XRT position (Source X; RA=5:11:34.77, Dec=-51:27:41.8). The
spectrum of Source A exhibits a red continuum indicative of an early-type
galaxy with prominent Ca II H+K stellar absorption lines at z=0.793. Source
B has a faint trace with a single possible emission line of unknown
identification near 9780 Angs. The spectrum of Source X is also that of an
early-type galaxy at z=0.788. We note that both Sources A and X lack
prominent emission lines of either [O II] 3727 or H-beta. The similarity
in the redshifts of Sources A and X, their early-type galaxy spectra, and
the abundance of extended sources in the vicinity of the XRT position may
signify an origin from a cluster or group.
We thank Magellan telescope operators Hernan, Jorge and Mauricio for their
assistance with these observations.
*http://www.swift.ac.uk/xrt_positions/
GCN Circular 20166
Subject
GRB 161104A: Chandra X-ray observations
Date
2016-11-10T17:27:14Z (9 years ago)
From
Wen-fai Fong at U of Arizona <wfong@email.arizona.edu>
R. Margutti (Northwestern U.), E. Berger (Harvard U.), and W. Fong (U.
Arizona) report:
"We observed the location of the short GRB161104A with the Chandra X-ray
Observatory (CXO) on 2016 Nov 8th, 14:41:45 UT, 364 ks after trigger (Mingo
et al., GCN 20123) under a pre-approved guest observer program (PI Berger).
No X-ray source is detected within the enhanced XRT position (Goad et al.,
GCN 20124). In particular, we do not find evidence for statistically
significant X-ray emission at the location of the optical source reported
by Troja et al., GCN 20137 at RA, Dec = 05:11:34.5, -51:27:33.90. Using
19.8 ks of CXO observations we infer a 3 sigma count-rate limit of 3.0E-4
c/s in the 0.5-8 keV energy range. The neutral hydrogen absorption in the
direction of the transient is 1.4E+20 cm-2 (Kalberla et al., 2005).
Assuming the spectral parameters that best fit the Swift-XRT observations
(power-law photon index Gamma=1.36 and no evidence for intrinsic neutral
hydrogen absorption, Burrows et al., GCN 20128) the inferred absorbed
(unabsorbed) flux limit is Fx< 4.4E-15 erg/s/cm2 (Fx<4.5E-15 erg/s/cm2) in
the 0.3-10 keV energy range. Our observations indicate a steepening of the
X-ray afterglow temporal decay. Starting from 20 ks after trigger, the
X-ray afterglow decays as t^-alpha with alpha>1.3.
We thank the CXO team for rapid scheduling of our observations."
GCN Circular 20137
Subject
GRB 161104A: Gemini South optical observations
Date
2016-11-05T22:12:41Z (9 years ago)
From
Eleonora Troja at GSFC <eleonora.troja@nasa.gov>
E. Troja (UMD/GSFC), A. Watson (UNAM), S. Covino (INAF), W. H. Lee
(UNAM), N. Butler (ASU), J. Becerra-Gonzalez (UMD/GSFC), A. Lien
(UMBC), T. Sakamoto (AGU) and N. Gehrels (NASA/GSFC) report:
We observed the field of the short GRB 161104A (Mingo et al., GCN 20123)
with the Gemini Multi-Object Spectrograph (GMOS) on the 8m Gemini South
telescope. We acquired 6x120s exposures in the r-band beginning at
02:53 UT on 05 November 2016 (~17 hours after the Swift trigger) and
under good observing conditions.
The three sources reported by Nicuesa Guelbenzu et al. (GCN 20132) are
detected with similar magnitudes, showing no significant variability
between our observations and the GROND exposures taken 1 hour later.
Within the enhanced XRT position (Goad et al., GCN 20124) we detect an
additional faint, point-like source not reported by Nicuesa Guelbenzu
et al. (GCN 20132). The position of this source is RA, Dec = 05:11:34.5,
-51:27:33.90 (J2000), accurate to about 0.5" in each coordinate. We
measure a preliminary magnitude of r~24.6 (AB).
The lack of detection in the subsequent GROND observations suggests that
the source significantly faded, however such rapid decay rate is unusual
for a GRB optical afterglow.
We thank the Gemini staff and observers for rapidly scheduling and executing
these observations.
GCN Circular 20132
Subject
GRB 161104A: GROND observations
Date
2016-11-05T07:37:21Z (9 years ago)
From
Ana Nicuesa at TLS Tautenburg <ana@tls-tautenburg.de>
A. Nicuesa Guelbenzu, S. Schmidl (both TLS Tautenburg) and J. Greiner
(MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 161104A (Swift trigger 720568; Mingo et
al., GCN 20123) simultaneously in g'r'i'z'JHK with GROND (Greiner et
al. 2008, PASP 120, 405) mounted at the 2.2m MPG telescope at the ESO
La Silla Observatory (Chile).
Observations started at 04:00 UT on 2016-11-05, 18 hours after the GRB
trigger. They were performed at an average seeing of 1" and at an
average airmass of 1.2. Inside the enhanced 3.2" XRT position (GCN
20124, Goad et al.) we find a single source at coordinates:
Source A
RA (J2000.0) = 05:11:34.46
DEC (J2000.0) = -51:27:36.3
with an uncertainty of 0.5" in each coordinate.
At the border of the XRT error circle lie two more sources at coordinates:
Source B
RA (J2000.0) = 05:11:34.31
DEC (J2000.0) = -51:27:33.6
Source C
RA (J2000.0) = 05:11:34.73
DEC (J2000.0) = -51:27:34.2
Their r'-band AB magnitudes are:
Source A
r' = 24.1 +- 0.1 mag,
Source B
r' = 24.3 +- 0.1 mag,
Source C
r' = 25.1 +- 0.3 mag,
For the moment no evidence for a fading of any of these objects can be
stated.
Given magnitudes are calibrated against GROND zeropoints and are not
corrected for the Galactic foreground extinction corresponding to a
reddening of E_(B-V) = 0.01 mag in the direction of the burst
(Schlafly & Finkbeiner 2011).
We thank Angela Hempel, La Silla, for performing the observations.
GCN Circular 20130
Subject
GRB 161104A: Swift/UVOT Upper Limits
Date
2016-11-05T03:28:35Z (9 years ago)
From
Mike Siegel at PSU/Swift MOC <siegel@swift.psu.edu>
M. H. Siegel (PSU) and B. Mingo (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 161104A
69 s after the BAT trigger (Mingo et al., GCN Circ. 20123).
No optical afterglow consistent with the XRT position
(Goad et al. GCN Circ. 20124)
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 initial exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 69 170 99 >20.8
w1 4984 5184 197 >19.9
m2 4779 4979 197 >21.7
w2 5805 6005 197 >19.9
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 20129
Subject
GRB 161104A, Swift-BAT refined analysis
Date
2016-11-05T02:14:12Z (9 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC),
B. Mingo (U Leicester), J. P. Norris (BSU), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+150 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 161104A (trigger #720568)
(Mingo, et al., GCN Circ. 20123). The BAT ground-calculated position is
RA, Dec = 77.906, -51.447 deg which is
RA(J2000) = 05h 11m 37.3s
Dec(J2000) = -51d 26' 49.7"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 99%.
The mask-weighted light curve shows a single spike that starts at at ~T-0.02,
peaks at ~T+0.02, and ends at~T+0.1. T90 (15-350 keV) is 0.1 +- 0.02 sec
(estimated error including systematics).
The time-averaged spectrum from T-0.0 to T+0.1 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.57 +- 0.20. The fluence in the 15-150 keV band is 3.1 +- 0.5 x 10^-8 erg/cm2.
The 1-sec peak photon flux measured from T-0.46 sec in the 15-150 keV band
is 0.6 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
Using a 4-ms binned light curve, the lag analysis finds a lag of
2.0 +/- 8.0 ms for the 100-350 keV to 25-50 keV band,
and -3.5 +/- 8.0 ms for the 50-100 keV to 15-25 keV band.
These values are consistent with those of a short GRB.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/720568/BA/
[GCN OPS NOTE05nov16): Per author's request, JN as was added
to the author list.]
GCN Circular 20128
Subject
GRB 161104A: Swift-XRT refined Analysis
Date
2016-11-04T21:00:38Z (9 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
D.N. Burrows (PSU), T.G.R. Roegiers (PSU), L.M. McCauley (PSU), B.
Mingo (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri
(INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC) and B. Mingo (U
Leicester) report on behalf of the Swift-XRT team:
We have analysed 6.3 ks of XRT data for GRB 161104A (Mingo et al. GCN
Circ. 20123), from 68 s to 23.6 ks after the BAT trigger. The data are
entirely in Photon Counting (PC) mode. The enhanced XRT position for
this burst was given by Goad et al. (GCN Circ. 20124).
The light curve can be modelled with a power-law decay with a decay
index of alpha=0.37 (+0.17, -0.16).
If the light curve continues to decay with a power-law decay index of
0.37, the count rate at T+24 hours will be 1.6 x 10^-3 count s^-1
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00720568.
This circular is an official product of the Swift-XRT team.
GCN Circular 20124
Subject
GRB 161104A: Enhanced Swift-XRT position
Date
2016-11-04T12:32:51Z (9 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester)
report on behalf of the Swift-XRT team.
Using 95 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 161104A, 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 = 77.89359, -51.46011 which is equivalent
to:
RA (J2000): 05h 11m 34.46s
Dec (J2000): -51d 27' 36.4"
with an uncertainty of 3.2 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 20123
Subject
GRB 161104A: Swift detection of a short burst
Date
2016-11-04T10:00:19Z (9 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
B. Mingo (U Leicester), A. P. Beardmore (U Leicester),
D. N. Burrows (PSU), P.A. Evans (U Leicester),
K. L. Page (U Leicester) and T. N. Ukwatta (LANL) report on behalf of
the Swift Team:
At 09:42:26 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 161104A (trigger=720568). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 77.881, -51.452 which is
RA(J2000) = 05h 11m 31s
Dec(J2000) = -51d 27' 07"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single peak
structure with a duration of about 0.3 sec. The peak count rate
was ~6000 counts/sec (15-350 keV), at ~0.1 sec after the trigger.
The XRT began observing the field at 09:43:24.9 UT, 58.3 seconds after
the BAT trigger. The position determined from promptly downlinked data
is incorrect because the XRT centroided on a cosmic ray.
Using promptly downlinked data we find an uncatalogued X-ray source
located at RA, Dec 77.89236, -51.45898 which is equivalent to:
RA(J2000) = 05h 11m 34.17s
Dec(J2000) = -51d 27' 32.3"
with an uncertainty of 4.5 arcseconds (radius, 90% containment). This
location is 35 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density.
UVOT took a finding chart exposure of 101 seconds with the White filter
starting 67 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 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 0.02.
Burst Advocate for this burst is B. Mingo (bm188 AT 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.)