GRB 150120A
GCN Circular 17310
Subject
GRB 150120A: Swift detection of a possibly-short burst
Date
2015-01-20T03:12:39Z (10 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
V. D'Elia (ASDC), D. N. Burrows (PSU), M. M. Chester (PSU),
N. Gehrels (NASA/GSFC), L. Izzo (URoma/ICRA),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU),
B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf
of the Swift Team:
At 02:57:46 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150120A (trigger=627137). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 10.308, +33.981 which is
RA(J2000) = 00h 41m 14s
Dec(J2000) = +33d 58' 52"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single symmetric
peak structure with a duration of about 1.5 sec. The peak count rate
was ~4000 counts/sec (15-350 keV), at ~0.5 sec after the trigger.
The XRT began observing the field at 02:59:02.6 UT, 76.2 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 10.31883, 33.99480 which is equivalent
to:
RA(J2000) = 00h 41m 16.52s
Dec(J2000) = +33d 59' 41.3"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 59 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 in excess of the Galactic value (7.86 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 6
(+5.52/-4.12) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 82 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
0.10.
Burst Advocate for this burst is V. D'Elia (delia AT asdc.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 17311
Subject
GRB 150120A: Prompt enhanced Swift-XRT position
Date
2015-01-20T03:24:31Z (10 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Using promptly downlinked XRT event data for GRB 150120A, we find an
enhanced XRT position of the afterglow: RA, Dec: 10.3187, 33.9944 which
is equivalent to:
RA (J2000) = 00 41 16.49
Dec (J2000) = +33 59 39.7
with an uncertainty of 2.2 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/627137.
Position enhancement is 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 17312
Subject
GRB 150120A: P60 optical observations
Date
2015-01-20T04:06:55Z (10 years ago)
From
Daniel Perley at Caltech <dperley@astro.caltech.edu>
D. A. Perley (Caltech) and S. B. Cenko (NASA/GSFC) report:
The Palomar 60-inch robotic telescope began automatic follow-up of the
location of possibly-short GRB 150120A (D'Elia et al. GCN 17310)
starting at 2015-01-20 03:00:33 UT, approximately 2.7 minutes after the
GRB trigger. A sequence of rotating r, i, and z 60-second exposures was
acquired, followed by five 180-second exposures in each of r and i
bands, under good conditions.
No sources are clearly detected inside the enhanced XRT error circle
(Evans et al., GCN 17311), either in either individual exposures or in
stacks of all 60-second exposures taken in each filter (approximate UT
center time 15 minutes post-trigger, limiting magnitudes r>22.5, i>22.4,
z>20.9). We detect two faint sources slightly outside the error circle
in the stacked frames:
Source A: RA=00:41:16.55, dec=+33:59:42.87
Source B: RA=00:41:16.76, dec=+33:59:42.11
Both sources appear to be marginally detected in SDSS pre-imaging and we
do not yet have evidence of fading behavior. Further observations and
analysis are ongoing.
[GCN OPS NOTE(20jan15): Per author's request, the date in the third line
was changed from 2015-01-t0 to 2015-01-20.]
GCN Circular 17313
Subject
GRB 150120A: Gemini-North optical imaging
Date
2015-01-20T07:51:01Z (10 years ago)
From
Wen-fai Fong at U of Arizona <wfong@email.arizona.edu>
W. Fong (U. Arizona), R. Chornock (Ohio U.) and D. Fox (PSU) report:
"We observed the location of the possibly short GRB 150120A (D'Elia et al.,
GCN 17310) with the Gemini Multi-Object Spectrograph (GMOS) mounted on the
Gemini-North 8-m telescope starting on 2015 Jan 20.206 UT (2.0 hr after the
BAT trigger). We obtained 1800-sec in each of the riz-bands in 0.5" seeing.
Within the enhanced XRT position (Evans, GCN 17311), we do not detect any
optical sources in our images. Tied to SDSS, we calculate a 3-sigma limit
of r>26.3 AB mag.
We clearly detect two sources on the outskirts of the XRT position (Sources
A and B from P60 observations; Perley et al., GCN 17312), both of which
appear extended in our images. We do not find any evidence for variability
of these sources over the duration of our observations.
We thank Gemini observers and staff Sabrina Pakzad, Katherine Roth, Joe
Burchett, and Rongmon Bordoloi for the quick scheduling and execution of
these observations."
GCN Circular 17317
Subject
GRB 150120A: Enhanced Swift-XRT position
Date
2015-01-20T10:39:01Z (10 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester)
report on behalf of the Swift-XRT team.
Using 465 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 150120A, 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 = 10.31893, +33.99485 which is equivalent
to:
RA (J2000): 00h 41m 16.54s
Dec (J2000): +33d 59' 41.5"
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 17319
Subject
GRB 150120A: Fermi GBM observation
Date
2015-01-20T13:49:42Z (10 years ago)
From
Andreas von Kienlin at MPE <azk@mpe.mpg.de>
A. von Kienlin (MPE) and E. Burns (UAH)
report on behalf of the Fermi GBM Team:
"At 02:57:47.00 UT on 20 January 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150120A (trigger 443415470/150120123), which was
also detected by the Swift/BAT & XRT
(D'Elia et al. 2015, GCN 17310). The GBM on-ground location is consistent
with the Swift position.
The angle from the Fermi LAT boresight is 98 degrees.
The GBM light curve shows a single pulse
with a duration (T90) of about 2 s (50-300 keV).
The time-averaged spectrum from T0-1.024 s to T0+0.512 s is
well fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.43 (+0.28/-0.24) and
the cutoff energy, parameterized as Epeak, is 130 (+150/-50) keV
The event fluence (10-1000 keV) in this time interval is
(3.4 +/- 0.8)E-07 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0-0.64 s in the 10-1000 keV band
is 3.1 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 17323
Subject
GRB 150120A: Swift/UVOT Upper Limits
Date
2015-01-20T19:56:38Z (10 years ago)
From
Margaret Chester at PSU <chester@swift.psu.edu>
M. M. Chester (PSU) and V. D'Elia (ASDC) report on behalf of
the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 150120A
83 s after the BAT trigger (D'Elia et al., GCN Circ. 17310).
No optical afterglow consistent with the XRT position (Evans et al.
GCN Circ. 17317) 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) exposures and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 83 233 147 >20.6
u_FC 295 545 246 >20.1
white 83 5674 461 >21.0
v 624 6085 432 >19.5
b 550 10198 449 >21.0
u 295 6700 658 >20.6
w1 674 6495 432 >20.5
m2 649 6290 432 >21.1
w2 600 5880 432 >20.5
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.10 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 17329
Subject
GRB 150120A: Swift-BAT refined analysis
Date
2015-01-20T22:50:07Z (10 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), V. D'Elia (ASDC), N. Gehrels (GSFC), J. Norris (BSU),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 150120A (trigger #627137)
(D'Elia, et al., GCN Circ. 17310). The BAT ground-calculated position is
RA, Dec = 10.330, 33.980 deg which is
RA(J2000) = 00h 41m 19.1s
Dec(J2000) = +33d 58' 48.6"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 71%.
The mask-weighted light curve shows a single short spike that starts at ~ T-0.4 s, peaks
at ~ T+0.4 s, and ends at ~ T+1.0 s. T90 (15-350 keV) is 1.20 +- 0.16 sec
(estimated error including systematics).
The time-averaged spectrum from T-0.40 to T+0.95 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.81 +- 0.18. The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.06 sec in the 15-150 keV band
is 1.8 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The burst spectrum appears to be at the softer end of short bursts, which have an
average spectral index of 1.2 when fitting with a simple power-law model
(Sakamoto et al. 2011). However, the fast fading shown in the X-ray light curve
(http://www.swift.ac.uk/xrt_curves/00627137/) suggests that this is indeed a short burst.
The lag analysis of this burst does not show a constraining result due to
the low intensity.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/627137/BA/
GCN Circular 17332
Subject
GRB 150120A: KAIT Optical Upper Limit
Date
2015-01-21T01:45:57Z (10 years ago)
From
Weikang Zheng at UC Berkeley <zwk@astro.berkeley.edu>
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRB 150120A (D'Elia et al.,
GCN 17310) starting at 02:59:24 UT, 98 s after the burst.
Observations were performed with an automatic sequence in the
clear (roughly R), V, and I filters, and the exposure time was
20 s per image. We do not detect any new source in our
images within the enhanced XRT error circle (Evans et al.,
GCN 17317). The typical limiting magnitude of our single clear
image is about 18.5 calibrated to USNO B1.0.
GCN Circular 17334
Subject
GRB 150120A: Swift-XRT refined Analysis
Date
2015-01-21T03:12:03Z (10 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U.
Leicester), A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), B.
Sbarufatti (INAF-OAB/PSU), V. Mangano (PSU), M.C. Stroh (PSU), D.N.
Burrows (PSU) and V. D'Elia report on behalf of the Swift-XRT team:
We have analysed 5.9 ks of XRT data for GRB 150120A (D'Elia et al. GCN
Circ. 17310), from 86 s to 16.2 ks after the BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Evans et al. (GCN Circ. 17311).
The light curve can be modelled with a power-law decay with a decay
index of alpha=~4.6.
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.0 (+/-0.5). The
best-fitting absorption column is 6.5 (+4.8, -3.3) x 10^21 cm^-2, in
excess of the Galactic value of 7.9 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 4.4 x 10^-11 (7.4 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 6.5 (+4.8, -3.3) x 10^21 cm^-2
Galactic foreground: 7.9 x 10^20 cm^-2
Excess significance: 2.8 sigma
Photon index: 2.0 (+/-0.5)
If the light curve continues to decay with a power-law decay index of
~4.6, the count rate at T+24 hours will be 1.2 x 10^-13 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.4 x
10^-24 (9.0 x 10^-24) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00627137.
This circular is an official product of the Swift-XRT team.
GCN Circular 17341
Subject
GRB 150120A: ISON-NM early optical limit
Date
2015-01-21T18:22:16Z (10 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
L. Elenin (KIAM), E. Mazaeva (IKI), A. Volnova (IKI), I. Molotov
(KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up
collaboration:
We observed the field of the Swift GRB 150120A (D'Elia et al.,
GCN 17310) with 0.4-m telescope of ISON-NM observatory in robotic mode
starting on Jan., 20 (UT) 02:58:58, i.e. 72 seconds after burst trigger.
We obtained 60 unfiltered images of 30 s exposure. We do not detect any
source within enhanced XRT error circle (Evans et al., GCN 17317):
Date UT start t-T0 Exp. Filter UL (3sigma)
(mid.,days) (s)
2015-01-20 02:58:58 0.00227 5*30 Clear 19.0
2015-01-20 02:58:58 0.01950 60*30 Clear 20.2
The photometry is based on nearby SDSS DR9 stars
SDSS9_id R_Lupton
J004136.43+340051.9 15.61
J004135.94+335950.0 14.56
J004101.23+335851.1 15.84
GCN Circular 17350
Subject
GRB 150120A: possible AMI 15 GHz detection
Date
2015-01-26T10:59:48Z (10 years ago)
From
Gemma Anderson at U of Oxford <gemma.anderson@astro.ox.ac.uk>
G. E. Anderson, R. P. Fender, T. D. Staley (University of Oxford),
A. J. van der Horst (George Washington University), A. Rowlinson (CASS)
We observed the position of the possibly-short burst GRB 150120A
(D�Elia et al., GCN 17310) at 15 GHz with the Arcminute Microkelvin Imager
(AMI-LA) starting on 2015 Jan 21.690 to 21.856 UT, corresponding to 1.6 days
post-burst. On this date we possibly detected a ~4 sigma radio source with flux
0.17 +/- 0.04 mJy at the position
RA(J200): 0:41:16.72
Dec(J2000): 33:59:55.4
with a positional uncertainty of ~10 arcseconds. This is ~14 arcseconds from
the best XRT position quoted by Evan et al., GCN 17317.
An earlier and later observation was conducted on 2015 Jan 20.475 to 20.559 UT
and 2015 Jan 22.666 to 22.832 UT, corresponding to 0.4 and 2.5 days post-burst,
yielding 3 sigma flux upper limits of 0.19 mJy and 0.10 mJy, respectively.
Further AMI monitoring is planned. We thank the AMI staff for scheduling these observations.
GCN Circular 17358
Subject
GRB 150120A: Gemini-N imaging and host redshift
Date
2015-01-28T22:40:07Z (10 years ago)
From
Ryan Chornock at Ohio U <chornock@ohio.edu>
R. Chornock (Ohio University) and W. Fong (University of Arizona) report:
We re-imaged the field of the possibly-short GRB 150120A (D'Elia et al.,
GCN 17310) with the Gemini Multi-Object Spectrograph (GMOS) mounted on the
Gemini-North 8-m telescope starting on 2015 Jan 22.284 UT (2.16 days
post-burst and 49.8 hr after our first Gemini observations; Fong et al.,
GCN 17313). We obtained a total of 2160s of observations in r-band in
1.0" seeing at an airmass of 1.6. Image subtraction using the ISIS package
reveals no residuals in or around the enhanced XRT position (Evans et al.,
GCN 17317). Based on the 3-sigma limit of the second epoch, which is not
deep as our first epoch due to poorer conditions, we place a limit of r(AB)>25.0
mag on the optical afterglow of GRB 150120A at 2.0 hr
post-burst.
We note that the enhanced XRT position (Evans et al., GCN 17317) shifted
relative to the prompt enhanced XRT position (Evans, GCN 17311) and now
encompasses Source A of Perley & Cenko (GCN 17312), while Source B is now
just outside the XRT error circle. We placed a spectroscopic slit across
both Sources A and B and obtained a pair of 900s GMOS spectra on 2014 Jan.
27 with the R400 grating (range 4900-9200 Angs). Both galaxies exhibit
nebular emission lines (H-beta, [O III]) at the same common redshift of
z=0.460.
We thank the staff at Gemini for their assistance scheduling and
performing these observations.
GCN Circular 17361
Subject
GRB 150120A: 9.8 GHz VLA upper limit
Date
2015-01-30T00:44:17Z (10 years ago)
From
Wen-fai Fong at U of Arizona <wfong@email.arizona.edu>
W. Fong (U. Arizona) reports:
"We observed the field of the possibly-short GRB 150120A (D'Elia et al.,
GCN 17310) with the Karl G. Jansky Very Large Array (VLA) beginning on 2015
Jan 21.027 UT (21.7 hr post-burst) at a mean frequency of 9.8 GHz. In 70
min of observations, we do not detect any radio source within or around the
enhanced XRT position (Evans et al., GCN 17317). In addition, we do not
detect any radio source within or near the position of the possible AMI
source at 15 GHz (Anderson et al., GCN 17350). We therefore place a 3-sigma
limit of ~30 microJy on the 9.8 GHz radio afterglow of GRB 150120A at 21.7
hr after the burst.
We thank the VLA staff for quickly executing these observations."