GRB 160325A
GCN Circular 19353
Subject
GRB 160325A: Skynet PROMPT-CTIO observations of the optical afterglow
Date
2016-04-26T14:02:12Z (10 years ago)
From
Adam S. Trotter at UNC-Chapel Hill/PROMPT/Skynet <atrotter@physics.unc.edu>
A. Trotter, D. Reichart, J. Haislip, J. Moore, N. Frank, M. Maples, E. Johnson, R. Joyner, J. Martin, C. Salemi, J. A. Crain, K. Ivarsen, A. LaCluyze, and M. Nysewander report:
Skynet observed the Swift BAT/XRT localization of GRB 160325A (Sonbas et al., GCN 19222, Swift trigger=680436) with with two 16" telescopes (P5, P6) and one 24" telescope (P1) of the PROMPT array at CTIO, Chile. Starting at 2016-03-25 07:01:44 UT and continuing until 09:55 UT (t=100s-2.9h post-trigger), Skynet took a total of 211 exposures ranging from 10-160s in the V band (P6) and the I band (P1,P5).
We clearly detected a fading optical afterglow at the position first reported by Fugazza & Melandri (GCN 19223).
A preliminary light curve is at:
http://www.skynet.unc.edu/grb/grb160325a.png
Magnitudes are in the Vega System, calibrated to 4 APASS DR9 stars in the field. Magnitudes have not been corrected for line-of-sight Milky Way dust extinction, with expected E(B-V)=0.12 (Schlafly & Finkbeiner 2011).
No further Skynet observations are scheduled.
GCN Circular 19244
Subject
Konus-Wind observation of GRB 160325A
Date
2016-03-29T13:44:26Z (10 years ago)
From
Anastasia Tsvetkova at Ioffe Institute <tsvetkova@mail.ioffe.ru>
A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks, P. Oleynik,
M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline
on behalf of the Konus-Wind team, report:
The long-duration GRB 160325A
(Swift-BAT trigger #680436: Sonbas, Lien & Page, GCN 19222;
Fermi GBM detection: Roberts, GCN 19224;
Fermi-LAT detection: Axelsson et al., GCN 19227)
triggered Konus-Wind at T0=25162.835 s UT (06:59:22.835).
The burst light curve shows two emission episodes,
a total duration of the burst (80-360 keV) is ~45 s.
The emission is seen up to ~1.5 MeV.
As observed by Konus-Wind, the burst
had a fluence of 1.73(-0.12,+0.14)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+10.304 s,
of 3.04(-1.04,+1.08)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the burst
(measured from T0 to T0+49.408 s)
is best fit in the 20 keV - 1.5 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.93(-0.14,+0.15),
and Ep = 214(-23,+31) keV (chi2 = 69/60 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -2.45 (chi2 = 69/59 dof).
The spectrum near the peak count rate
(measured from T0 to T0+16.640 s)
is best fit in the 20 keV - 2 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.76(-0.15,+0.18),
the high energy photon index beta = -2.47(-0.59,+0.26),
the peak energy Ep = 207(-26,+32) keV,
chi2 = 70/57 dof.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160325_T25162/
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 19234
Subject
GRB 160325A, Swift-BAT refined analysis
Date
2016-03-26T04:07:19Z (10 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),
D. M. Palmer (LANL), T. Sakamoto (AGU), E. Sonbas (Adiyaman Univ.),
M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 160325A (trigger #680436)
(Sonbas et al., GCN Circ. 19222). The BAT ground-calculated position is
RA, Dec = 15.697, -72.702 deg which is
RA(J2000) = 01h 02m 47.4s
Dec(J2000) = -72d 42' 06.4"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.
The mask-weighted light curve shows a multi-peaked structure that starts at
~ T-60 s and ends at ~T+60 s. The burst location came into the BAT FoV
at ~T-93 s during a preplanned slew, so there could be further burst activities
beforehand. The burst structure contains two main pulses. The first pulse starts
at ~T-60 s, peaks at ~ T-34 s, and ends at ~T-25 s. The second pulse starts
at ~T0, peaks at ~T+3 s, and ends ~T+5 s. T90 (15-350 keV) is 64.9 +- 14.7 sec
(estimated error including systematics).
The time-averaged spectrum from T-51.74 to T+60.45 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.27 +- 0.04. The fluence in the 15-150 keV band is 7.1 +- 0.2 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T-33.46 sec in the 15-150 keV band
is 5.2 +- 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/680436/BA/
GCN Circular 19233
Subject
GRB 160325A: GROND Upper Limits
Date
2016-03-26T01:22:14Z (10 years ago)
From
Corentin Delvaux at MPE <delvaux@mpe.mpg.de>
C. Delvaux (MPE Garching), D. A. Kann (TLS Tautenburg), F. Knust, and J.
Greiner (both MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 160325A (Swift trigger 680436; Sonbas et
al., GCN #19222, Fermi GBM detection, Roberts, GCN #19924, Fermi LAT
detection, Axelsson et al., GCN #19227) simultaneously in g'r'i'z'JHK
with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG
telescope at ESO La Silla Observatory (Chile).
Observations started at 23:29 UT on 25/03/2016, 16.5 hrs after the GRB
trigger. They were performed at an average seeing of 1.7" and at an
average airmass of 2.3.
We do not detect the source reported by Fugazza et Melandri (GCN #19223)
down to the following magnitudes (in AB system):
g > 22.4 mag,
r > 22.5 mag,
i > 22.3 mag,
z > 22.4 mag,
J > 20.3 mag,
H > 19.8 mag, and
K > 18.5 mag.
Given upper limits are calibrated against GROND zeropoints as well as
2MASS field stars and are not corrected for the expected Galactic
foreground extinction corresponding to a reddening of E_(B-V)=0.1 mag in
the direction of the burst (Schlafly & Finkbeiner 2011).
GCN Circular 19232
Subject
GRB 160325A: Swift-XRT refined Analysis
Date
2016-03-25T23:14:54Z (10 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), D.N. Burrows (PSU),
T.G.R. Roegiers (PSU), L.M. McCauley (PSU), A.P. Beardmore (U.
Leicester), P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), V.
D'Elia (ASDC) and E. Sonbas report on behalf of the Swift-XRT team:
We have analysed 7.5 ks of XRT data for GRB 160325A (Sonbas et al. GCN
Circ. 19222), from 55 s to 41.2 ks after the BAT trigger. The data
comprise 436 s 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 Evans et
al. (GCN Circ. 19229).
The late-time light curve (from T0+6.0 ks) can be modelled with a
power-law decay with a decay index of alpha=2.7 (+0.6, -0.5).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.342 (+0.033, -0.029). The
best-fitting absorption column is consistent with the Galactic value
of 5.9 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has
a photon index of 2.18 (+0.16, -0.08) and a best-fitting absorption
column consistent with the Galactic value. The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum is 3.9 x 10^-11 (7.3 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 5.9 (+0.9, -0.0) x 10^21 cm^-2
Galactic foreground: 5.9 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index: 2.18 (+0.16, -0.08)
If the light curve continues to decay with a power-law decay index of
2.7, the count rate at T+24 hours will be 1.5 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.9 x
10^-15 (1.1 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00680436.
This circular is an official product of the Swift-XRT team.
GCN Circular 19231
Subject
GRB 160325A: Further Swift/UVOT Observations
Date
2016-03-25T22:40:00Z (10 years ago)
From
Lea Hagen at PSU <lea.zernow.hagen@gmail.com>
L. M. Z. Hagen (PSU) and E. Sonbas (Adiyaman Univ.)
report on behalf of the Swift/UVOT team:
We report further on the Swift/UVOT observations of GRB 160325A which
began 75 s after the BAT trigger (Sonbas et al., GCN Circ. 19222). A
source was reported earlier by McCauley et al. (GCN Circ. 19228), which
was consistent with the XRT position (Evans et al., GCN Circ. 19229)
and infrared detection (Fugazza et al., GCN Circ. 19223). We confirm
that the source is rapidly fading.
Preliminary detections 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 75 224 146 15.65+-0.05
white 567 1187 205 17.24+-0.05
white 7227 12203 231 19.59+-0.16
v 617 809 38 15.12+-0.07
v 1044 1237 38 15.79+-0.10
v 1392 6402 216 17.73+-0.14
b 543 735 38 17.11+-0.11
b 1143 1510 58 18.70+-0.33
b 7023 7222 196 >19.64
u 287 537 245 18.91+-0.22
u 691 7017 274 >19.47
uvw1 666 1461 97 18.36+-0.32
uvw1 6613 6812 196 19.05+-0.33
uvm2 641 1263 77 18.30+-0.34
uvm2 1416 6607 216 18.73+-0.29
uvw2 593 1387 97 >18.63
uvw2 5998 6197 196 18.30+-0.19
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 19230
Subject
GRB 160325A: afterglow confirmation
Date
2016-03-25T17:22:35Z (10 years ago)
From
Andrea Melandri at INAF-OAB <andrea.melandri@brera.inaf.it>
A. Melandri, D. Fugazza (INAF-OAB), M. De Pasquale (MSSL-UCL) report on behalf of a larger collaboration:
Further analysis of REM near-infrared observations of the field of of GRB 160325A (Sonbas et al., GCN 19222) showed that the source reported as candidate afterglow in our earlier imaging (Fugazza & Melandri, GCN 19223; McCauley & Sonbas, GCN 19228) has faded in the JHK filters. Observations cover the time interval bewteen ~1 and 120 minutes after the burst event.
The light curve has an initial decay of alpha1 ~ 0.45, and after 10 minutes it steepens to alpha2 ~ 1.5. The fading nature confirms that this source is the afterglow of GRB 160325A.
GCN Circular 19229
Subject
GRB 160325A: Enhanced Swift-XRT position
Date
2016-03-25T17:07:26Z (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 2264 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 160325A, 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 = 15.65055, -72.69659 which is equivalent
to:
RA (J2000): 01h 02m 36.13s
Dec (J2000): -72d 41' 47.7"
with an uncertainty of 1.7 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 19228
Subject
GRB160325A Swift/UVOT Detection
Date
2016-03-25T15:25:24Z (10 years ago)
From
Marissa McCaule at PSU <marissamc@swift.psu.edu>
L. M. McCauley (PSU) and E. Sonbas (Adiyaman Univ.) report on behalf of
the Swift/UVOT team:
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 74 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 01:02:36.28 = 15.65118
DEC(J2000) = -72:41:46.8 = -72.69634
with a 90%-confidence error radius of about 0.61 arc sec. This position is
5.35
arc sec. from the center of the XRT error circle and consistent with the
position
reported by Fugazza et al. (GCN Circ. 19223).
Preliminary detections 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_fc 74 160 86 15.48+-0.03
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 19227
Subject
GRB 160325A: Fermi-LAT detection
Date
2016-03-25T13:58:49Z (10 years ago)
From
Magnus Axelsson at Stockholm U. <magaxe@kth.se>
M. Axelsson (KTH Stockholm), E. Bissaldi (Politecnico and INFN Bari), R. Desiante (INFN Torino and Udine University) and F. Longo (University of Trieste and INFN Trieste) report on behalf of the Fermi-LAT team:
At UT 06:59:21 on March 25 2016 Fermi-LAT detected high-energy emission from GRB 160325A, which was also detected by Swift (Sonbas et al. 2016, GCN 19222) and Fermi-GBM (trigger 480581965/160325291; Roberts 2016, GCN 19224).
The best LAT on-ground location is found to be:
RA, Dec (J2000) = (16.14, -72.66)
with an error radius of 0.17 deg (90 % containment, statistical error only).
The Fermi-LAT position is consistent with that found by Swift-XRT (Sonbas et al. 2016, GCN 19222).
The LAT data show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance. More than 45 photons >100 MeV and 3 photons > 1GeV are detected in the 1500 s following the trigger. The highest-energy photon is a 3 GeV event which is observed 100 seconds after the GBM trigger.
The Fermi-LAT point of contact for this burst is M. Axelsson (magaxe@kth.se<mailto:magaxe@kth.se>).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular 19224
Subject
GRB 160325A: Fermi GBM detection
Date
2016-03-25T12:53:53Z (10 years ago)
From
Oliver Roberts at UCD/Fermi <oliver.roberts@ucd.ie>
O.J. Roberts (UCD) reports on behalf of the Fermi GBM Team:
"At 06:59:21.51 UT on the 25th of March 2016, the Fermi
Gamma-Ray Burst Monitor triggered and located GRB 160325A
(trigger 480581965 / 160325291), which was also detected by
Swift (Sonbas et al. 2008, GCN 19222). The GBM on-ground location
is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time
using the Swift XRT position is about 6 degrees.
The GBM light curve consists of two main emission episodes with a
duration (T90) of about 43 s (50-300 keV). The time-averaged
spectrum from T0+2.3 s to T0+45.3 s is well fit by a Band function
with Epeak = 235 +/- 19 keV, alpha = -0.78 +/- 0.05,
and beta = -2.21 +/- 0.14.
The event fluence (10-1000 keV) in this time interval is
(1.91 +/- 0.04) E-05 erg/cm^2. The 1.024-sec peak photon
flux measured starting from T0+9.5 s in the 10-1000 keV band
is 8.5 +/- 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 19223
Subject
GRB160325A: REM NIR observations
Date
2016-03-25T08:04:34Z (10 years ago)
From
Dino Fugazza at INAF-OAB <dino.fugazza@brera.inaf.it>
D. Fugazza, A. Melandri (INAF/OAB) report on behalf of the REM team:
We observed the field of GRB 160325A (Sonbas et al., GCN 19222) with the
60-cm robotic telescope REM located at the La Silla Observatory (Chile).
The observations started at 07:01:08 UT, 65 seconds after the Burst, and
were carried out simultaneously with in the g, r, i, z and H bands.
An uncatalogued bright source in the XRT error box is detected at the
coordinates:
RA(2000) = 01:02:36.06
Dec(2000) = -72:41:47.7
with an estimated uncertainty of +/- 0.7 arcsec.
A very preliminary photometry indicates it was H ~10.71 +/- 0.01 about
270 sec after the burst.
Further observations are in progress to assess its variability.
GCN Circular 19222
Subject
GRB 160325A: Swift detection of a burst
Date
2016-03-25T07:31:21Z (10 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
E. Sonbas (Adiyaman Univ.), A. Y. Lien (GSFC/UMBC) and
K. L. Page (U Leicester) report on behalf of the Swift Team:
At 07:00:03 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160325A (trigger=680436). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 15.597, -72.706 which is
RA(J2000) = 01h 02m 23s
Dec(J2000) = -72d 42' 22"
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. One of the major pulses occurred
at ~ -40 s before BAT trigger during spacecraft slews. The peak count rate
was ~9000 counts/sec (15-350 keV), at ~3 sec after the trigger.
The XRT began observing the field at 07:01:10.0 UT, 66.4 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 15.65210,
-72.69671 which is equivalent to:
RA(J2000) = 01h 02m 36.50s
Dec(J2000) = -72d 41' 48.2"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 67 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 in excess of the Galactic value (5.91 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 2.3
(+2.60/-2.22) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 4.15e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 74 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. Because of the density of catalogued stars, further
analysis is required to report an upper limit for any afterglow in the
sub-image. The 8'x8' region for the list of sources generated on-board covers
0.00% of the XRT error circle. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.04.
Burst Advocate for this burst is E. Sonbas (edasonbas AT yahoo.com).
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.)