GRB 170405A
GCN Circular 21003
Subject
GRB 170405A: SMARTS optical/IR afterglow observations
Date
2017-04-09T00:35:06Z (9 years ago)
From
Bethany Cobb at GWU <bcobb@gwu.edu>
B. E. Cobb (GWU), reports:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 170405A
(GCN 20984, Troja et al.) at two epochs (with mid-exposure times
of 2017-04-06 02:51 UT & 06:52 UT). For each epoch, several
dithered images were obtained with total summed exposure times
of 15 min in V and I and 12 min in J and K.
The fading afterglow of GRB 170405A (e.g. GCN 20984, Troja et al.;
GCN 20988, Malesani et al.; GCN 20989, Klotz et al.) was detected
with the preliminary magnitudes (or 3-sigma limits) listed below.
Note that the optical photometry is calibrated against USNO-B1.0
stars in the field, so suffers from a large photometric calibration
error of about +/-0.2 magnitudes, which has not been included in
the errors quoted below. The IR photometry is calibrated against
2MASS stars. Additionally, the nearby source noted by Malesani
et al. (GCN 20988) is seen and is likely affecting the afterglow
photometry due to its proximity.
mid-exposure
time post-burst
(hours) I mag J mag K mag
8.19000 20.4+/-0.1 >18.5 >16.9
12.1975 21.1+/-0.1 >18.8 >16.8
GCN Circular 21000
Subject
GRB170405A, Swift-UVOT Detection
Date
2017-04-07T06:46:05Z (9 years ago)
From
Sam LaPorte at PSU <sjl5346@psu.edu>
GRB 170405A: Swift/UVOT Detection
S. J. LaPorte (PSU) and E. Troja (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 170405A
129 s after the BAT trigger (Troja et al., GCN Circ. 20984). Consistent
with previous reports (Malesani et al, GCN Circ. 20988; Martin-Carrillo et al.
GCN Circ. 20991), a fading source consistent with the XRT position
(Evans et al. GCN Circ. 20985) is detected in the initial UVOT exposures at:
RA (J2000) = 14:39:18.73 = 219.82805 (deg.)
Dec (J2000) = -25:14:35.4 = -25.24317 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).
The upper limits in the UV bands are consistent with the reported
redshift of z = 3.51 (de Ugarte-Postigo et al, GCN Circ. 20990).
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) 129 279 147 16.01 +/- 0.03
white 747 998 143 18.09 +/- 0.07
v 618 637 20 16.31 +/- 0.14
b 543 563 20 17.34 +/- 0.13
u 287 711 265 >20.2
uvw1 667 859 39 >18.9
uvm2 815 835 19 >17.5
uvw2 593 786 39 >19.1
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.09 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 20999
Subject
GRB 170405A, Swift-BAT refined analysis
Date
2017-04-07T03:25:45Z (9 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), N. Gehrels (GSFC),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), T. Sakamoto (AGU),
M. Stamatikos (OSU), E. Troja (NASA/GSFC/UMCP),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 170405A (trigger #745797)
(Troja et al., GCN Circ. 20984). The BAT ground-calculated position is
RA, Dec = 219.824, -25.236 deg which is
RA(J2000) = 14h 39m 17.8s
Dec(J2000) = -25d 14' 09.7"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 6%.
The burst was outside of the BAT calibrated field of view from T-134.3 s to T+56.7 s.
The mask-weighted light curve using the ���detection mask��� (which covers a broader
field of view, but is not well calibrated; see detail description in Markwardt et al. 2007)
shows a multi-peaked structure that starts at ~T-30 s and ends at ~T+240 s. The
major peak occurs at ~T+5 s. T90 (15-350 keV) is 164.7 +- 35.4 sec (estimated error
including systematics).
The time-averaged spectrum from T+56.7 to T+242.5 sec (i.e., when the burst is in the
BAT calibrated field of view) is best fit by a simple power-law model. The power law
index of the time-averaged spectrum is 1.59 +- 0.12. The fluence in the 15-150 keV
band is 3.7 +- 0.3 x 10^-06 erg/cm2. 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/745797/BA/
GCN Circular 20998
Subject
GRB 170405A: Etelman observatory optical observations
Date
2017-04-06T19:41:45Z (9 years ago)
From
Bruce Gendre at UVI <bruce.gendre@gmail.com>
B. Gendre (UVI), N. Orange (OrangeWave Innovative Science, LLC), D.
Morris (UVI), A. Cucchiara (UVI), D. Drost (UVI), T. Giblin (USAF
Academy), J. Hakkila (College of Charleston), A. Klotz (IRAP), J. Neff
(NSF), D. Smith (UVI), J. Staff (UVI), P. Thierry (Auragne Observatory),
R. Watlington (UVI), and L. Wentlent (UVI) report:
We observed the field of GRB 170405A (Troja et al, GCN 20984;
Hui & Meegan, GCN 20986; Vianello & Kocevski, GCN 20987) with the
0.5m Virgin Island Robotic Telescope (VIRT) on February the 6th,
starting at 6:15 UT (11.6 hours after the trigger). We
performed a series of exposures in the clear filter. The weather
conditions were good during the observations.
We co-added the exposures taken between 6h15UT (t0+11.6h) and
7h29UT (t0+12.8h), for a total exposure of 3510s. At the position of the
optical afterglow reported by Malesani et al. (GCN 20988), we do not
detect any optical emission, with an upper limit of R = 21.3 (Johnson
system) estimated from nearby NOMAD1 stars.
Magnitudes have not been corrected for Galactic extinction.
The VIRT is still in its commissioning phase.
This message can be cited.
GCN Circular 20997
Subject
GRB 170405A: Swift-XRT refined Analysis
Date
2017-04-06T17:03:32Z (9 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
K.L. Page (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A.
D'Ai (INAF-IASFPA), A. Cholden-Brown (PSU), S. J. LaPorte (PSU), J.A.
Kennea (PSU), B. Mingo (U. Leicester), A.P. Beardmore (U. Leicester)
and report on behalf of the Swift-XRT team: report on behalf of the
Swift-XRT team:
We have analysed 6.5 ks of XRT data for GRB 170405A, from 111 s to 57.3
ks after the BAT trigger. The data comprise 489 s in Windowed Timing
(WT) mode (the first 8 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode.
The late-time light curve (from T0+4.5 ks) can be modelled with a
power-law decay with a decay index of alpha=1.66 (+0.14, -0.12).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.592 (+0.027, -0.019). The
best-fitting absorption column is consistent with the Galactic value
of 8.7 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has
a photon index of 1.84 (+0.09, -0.07) 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 3.6 x 10^-11 (4.2 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Galactic foreground: 8.7 x 10^20 cm^-2
Intrinsic column: 8.7 (+68.1, -0.0) x 10^20 cm^-2 at z=3.51
Photon index: 1.84 (+0.09, -0.07)
If the light curve continues to decay with a power-law decay index of
1.66, the count rate at T+24 hours will be 5.5 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.0 x
10^-13 (2.3 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/00745797.
This circular is an official product of the Swift-XRT team.
GCN Circular 20996
Subject
GRB 170405A: RATIR Optical and NIR Observations
Date
2017-04-06T15:58:54Z (9 years ago)
From
Eleonora Troja at GSFC <eleonora.troja@nasa.gov>
Eleonora Troja (GSFC), Nat Butler (ASU), Alan M. Watson (UNAM),
Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM),
Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB),
Antonino Cucchiara(UVI), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz
(UCSC),
Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey Moseley (GSFC),
John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:
We observed the field of GRB 170405A (Troja, et al., GCN 20984) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio Astron��mico Nacional on
Sierra San Pedro M��rtir from 2017/04 6.23 to 2017/04 6.48 UTC (10.93
to 16.85 hours after the BAT trigger), obtaining a total of 3.84 hours
exposure in the r and i bands and 1.62 hours exposure in the Z,
Y, J, and H bands.
For a source within the Swift-UVOT error circle (Troja, et al., GCN 20984),
in comparison with the USNO-B1 and 2MASS catalogs, we obtain the following
detections:
r 22.67 +/- 0.05
i 21.83 +/- 0.04
Z 21.26 +/- 0.07
Y 21.14 +/- 0.07
J 20.75 +/- 0.07
H 20.56 +/- 0.08
These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.
The nearby object noted by Malesani et al., (GCN 20988) is detected in all
our images and might affect our photometric measurements. The reported
values should be therefore considered as preliminary.
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.
Further observations are planned.
GCN Circular 20995
Subject
Konus-Wind observation of GRB 170405A
Date
2017-04-06T14:57:40Z (9 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov,
D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline,
on behalf of the Konus-Wind team, report:
The long GRB 170405A (Swift-BAT detection: Troja et al.,GCN 20984;
Fermi-GBM detection: Hui & Meegan., GCN 20986;
Fermi-LAT detection: Vianello & Kocevski, GCN 20987)
triggered Konus-Wind at T0=67181.254 s UT (18:39:41.254)
The light curve shows a multi-peaked structure
with a total duration of ~100 s and a hint of a subsequent
weak/soft emission lasting until ~T0+200 s.
The emission is seen up to ~10 MeV.
As observed by Konus-Wind, the burst had a fluence of
(1.05 �� 0.12)x10^-4 erg/cm2 and a 64-ms peak energy flux,
measured from T0+15.744, of (5.9 �� 0.9)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+73.984 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.53 (-0.17,+0.19),
the high energy photon index beta = -2.36 (-0.25,+0.15),
the peak energy Ep = 244 (-27,+32) keV,
chi2 = 98/96 dof.
The spectrum near the peak count rate (measured from T0+8.448 s
to T0+24.832 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.54 (-0.22,+0.24),
the high energy photon index beta = -2.56 (-1.02,+0.27),
the peak energy Ep = 265 (-36,+51) keV,
chi2 = 71/96 dof.
Assuming the redshift z=3.510 (de Ugarte Postigo et al., GCN 20990)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.3, and Omega_Lambda = 0.7,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~2.6x10^54 erg,
the peak luminosity L_iso is ~6.6x10^53 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~1100 keV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170405_T67181/
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
[GCN OPS NOTE(06apr17): Per author's request, in the first paragraph
the V&K CirNum was changed from "20827" to "20987", and in the 6th paragraph
the de Ugarte Postigo CircNum was changed from "20104" to "20990".]
GCN Circular 20994
Subject
GRB 170405A: LCO FTN observations
Date
2017-04-06T13:02:36Z (9 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
C. Guidorzi (U. Ferrara), S. Kobayashi, I.A. Steele (LJMU), A. Gomboc
(U. Nova Gorica), C.G. Mundell (U. Bath) on behalf of a large
collaboration report:
We observed Swift GRB 170405A (Troja et al. GCN 20984) on April 06, from
10:23 to 11:01 UT (0.66 to 0.68 days since the GRB) with the 2-m LCO
Faulkes Telescope North with the SDSS i and r filters. We do not detect
the optical afterglow (Troja et al; Malesani et al. GCN 20988; Klotz et
al. GCN 20989; de Ugarte Postigo et al. GCN 20990; Martin-Carrillo et
al. GCN 20991; Mazaeva et al. GCN 20992) down to the following limits:
Mid Time Exposure Filter Magnitude (AB)
(days) (s)
-------------------------------------------------------
0.66 5x120 SDSS-R > 21.6
0.68 4x120 SDSS-I > 21.6
-------------------------------------------------------
as calibrated against nearby Pan-STARRS objects. The nearby Pan-STARRS
object mentioned by Malesani et al. is clearly visible in our stacked
frames.
GCN Circular 20992
Subject
GRB 170405A: ISON/Terskol optical observations
Date
2017-04-06T12:12:17Z (9 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
E. Mazaeva (IKI), V. Agletdinov (KIAM), A. Pozanenko (IKI), A. Volnova
(IKI), I. Molotov (KIAM) report on behalf of larger GRB follow-up
collaboration:
We observed the field of GRB 170405A (Troja et al., GCN 20984) with
K-800 (0.8m) telescope of ISON/Terskol observatory starting on
April, 05 (UT) 19:12:55, i.e. 45 minutes after GRB onset. We obtained
several unfiltered images of 15 s exposure. The optical afterglow Troja
et al., GCN 20984; Malesani et al., GCN 20988; Klotz et al., GCN 20989;
Ugarte Postigo et al., GCN 20990; Martin-Carrillo et al., GCN 20991)
is clearly visible in combined images. Preliminary photometry of the
afterglow is following
Date UT start t-T0 Filter Exp. OT Err. UL
(mid, days) (s)
2017-04-05 19:12:55 0.03139 CR 72*15 17.27 0.10 20.1
2017-04-05 19:34:33 0.04300 CR 48*15 17.96 0.13 19.8
2017-04-05 19:49:05 0.06019 CR 110*15 18.39 0.14 20.4
2017-04-05 20:23:55 0.08543 CR 110*15 19.18 0.22 20.2
2017-04-05 21:01:48 0.11099 CR 107*15 n/d n/d 18.9
Photometry is based on nearby USNO-B1.0 stars
USNO-B.1_id R2
0647-0315771 15.13
0647-0315754 15.45
0647-0315872 15.34
0647-0315921 15.08
0647-0315788 14.92
Preliminary light curve of the afterglow can be found in
http://grb.rssi.ru/GRB170405A/GRB170405A_light_curve.png
GCN Circular 20991
Subject
GRB 170405A: Watcher optical detection
Date
2017-04-06T07:36:55Z (9 years ago)
From
Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>
A. Martin-Carrillo (UCD), D. Murphy (UCD), L. Hanlon (UCD), H. J. van Heerden (UFS), B. van Soelen (UFS) and P. J. Meintjes (UFS)
We observed the field of GRB 170405A (Troja et al, GCN 20984; Hui & Meegan, GCN 20986; Vianello & Kocevski, GCN 20987) using the 40cm UCD Watcher telescope at Boyden Observatory in South Africa.
Due to bad weather observations started at 19:31:13 UT, about 51.4 minutes after the burst trigger (T0=18:39:48 UT). A faint source consistent with the UVOT coordinates reported by Troja et al. is detected on our combined images taken with the SDSS r��� filter. At a mid-time of 20:00 UT, we derive a preliminary magnitude of r���=18.0 (AB system), confirming that the source has faded since the UVOT detection.
Magnitudes were calibrated using several nearby APASS stars. No correction for Galactic extinction in the direction of the GRB has been applied.
GCN Circular 20990
Subject
GRB 170405A: Redshift from OSIRIS/GTC
Date
2017-04-06T03:10:20Z (9 years ago)
From
Antonio de Ugarte Postigo at IAA-CSIC <deugarte@iaa.es>
A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), D.A. Kann (IAA-CSIC),
C.C. Thoene (IAA-CSIC), L. Izzo (IAA-CSIC), N.R. Tanvir (U. Leicester),
G. Lombardi (GTC, IAC), and A. Marante (GTC) report on behalf of a
larger collaboration:
We observed the field of GRB 170405A (Troja et al., GCN 20984; Hui
& Meegan, GCN 20986; Vianello & Kocevski, GCN 20987) using OSIRIS
on the 10.4m GTC at the Roque de los Muchachos observatory (La Palma,
Spain). The observation consisted of 3x900s using the R1000B grism,
covering the range between 3700 and 7800 ��. The first spectrum started at
2:14 UT (7.57 hr after the burst).
On a preliminary reduction based on archival calibrations we detect a
spectral continuum with strong absorption features, which we identify as
due to Ly-alpha, SiII, OI, CII, SiIV, CIV, FeII and AlII at a common redshift of
z = 3.510, which we identify as the redshift of the GRB.
GCN Circular 20989
Subject
GRB 170405A: TAROT Reunion observatory optical observations
Date
2017-04-06T02:22:43Z (9 years ago)
From
Alain Klotz at IRAP-CNRS-OMP <Alain.Klotz@free.fr>
Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP),
Boer, M., Laugier, R. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.)
Thierry P. (Auragne Observatory, France),
Klotz A.N.O. (Guitalens Observatory, France)
report:
We imaged the field of GRB 170405A detected by SWIFT
(trigger 745797) with the TAROT robotic telescope (D=18cm)
located at the Reunion observatory, France.
The observations started 3.84h after the GRB trigger.
We detected the OT (Troja et al., GCN 20984;
Hui & Meegan, GCN 20986; Vianello & Kocevski, GCN 20987;
Malesani, GCNC 20988):
t0+3.84h to t0+3.97h : R=19.0 +/- 0.2
Magnitudes were estimated with the nearby NOMAD1 stars
and are not corrected for galactic dust extinction.
GCN Circular 20988
Subject
GRB 170405A: NOT optical observations
Date
2017-04-06T01:22:36Z (9 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
Daniele Malesani (DARK/NBI), K. E. Heintz (DARK/NBI and Univ. Iceland),
and Tapio Pursimo (NOT) report on behalf of a larger collaboration:
We observed the optical afterglow of GRB 170405A (Troja et al., GCN
20984; Hui & Meegan, GCN 20986; Vianello & Kocevski, GCN 20987) with the
Nordic Optical Telescope (NOT) equipped with the ALFOSC imager.
Observations were carried out in the SDSS griz filters, with a
sub-optimal PSF (1.6-2.0").
Inspection of the r-band image (with mean time Apr 6.01 UT, that is 5.47
hr after the trigger) clearly shows the optical afterglow first
localized by UVOT (Troja et al., GCN 20984), which has now faded to r =
21.05 +- 0.08 AB, calibrated against nearby stars from the Pan-STARRS
catalog. In our images, the afterglow coordinates are perfectly
consistent with the UVOT values:
RA(J2000) = 14:39:18.72
Dec(J2000) = -25:14:35.3
We also note the presence of a nearby object approximately 2.3" W of the
afterglow, also visible in the Pan-STARRS archival images (with a
Pan-STARRS magnitude r = 21.82 +- 0.19 AB). Its relation to the GRB is
not clear, but its proximity may affect the afterglow photometry.
GCN Circular 20987
Subject
GRB 170405A: Fermi-LAT detection
Date
2017-04-06T00:24:15Z (9 years ago)
From
Giacomo Vianello at SLAC <giacomov@slac.stanford.edu>
G.Vianello (Stanford), D.Kocevski (NASA/MSFC)
report on behalf of the Fermi-LAT team:
At 18:39:22.89 on April, 05, 2017 Fermi-LAT detected high-energy
emission from GRB 170405A, which was also detected by Swift (Troja et
al., GCN 20984) and Fermi/GBM (trigger 513110367/170405777).
The best LAT on-ground location is found to be:
RA, Dec = 219.37, -25.23 (J2000)
with an error radius of 0.51 deg (90 % containment, statistical error
only). This was 53 deg from the LAT boresight at the time of the
trigger and triggered an autonomous repoint of the spacecraft. This
position is compatible with the XRT position reported by Evans et al.
(GCN 20985).
The data from the Fermi-LAT show a significant increase in the event
rate that is spatially and temporally correlated with the trigger with
high significance. More than 13 events have been observed above 100
MeV which are spatially and temporally correlated with the GRB. The
highest-energy photon is a 900 MeV event which is observed 445 seconds
after the GBM trigger.
We note that roughly 5 ks of data are currently available. We will
provide an update, if necessary, as more data become available.
The Fermi-LAT point of contact for this burst is Giacomo Vianello
(giacomov@stanford.edu)
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 20986
Subject
GRB 170405A: Fermi GBM observation
Date
2017-04-05T22:51:57Z (9 years ago)
From
C. Michelle Hui at MSFC/Fermi-GBM <c.m.hui@nasa.gov>
C. M. Hui (MSFC) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
At 18:39:22.89 UT on 05 April 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 170405A (trigger 513110367/170405777),
which was also detected by Swift (Troja et al. 2017, GCN 20984).
The GBM on-ground location is consistent with the Swift position.
The trigger resulted in an Autonomous Repoint Request (ARR)
by the GBM Flight Software owing to the high peak flux of the GRB.
This ARR was accepted and the spacecraft slewed to the GBM in-flight
location. The initial angle from the Fermi LAT boresight is 52 degrees.
The GBM light curve shows multiple peaks
with a duration (T90) of about 78.6 s (50-300 keV).
The time-averaged spectrum from T0+7.2 s to T0+86.0 s is
adequately fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.01 +/- 0.01 and
the cutoff energy, parameterized as Epeak, is 355.2 +/- 8.6 keV.
The event fluence (10-1000 keV) in this time interval is
(7.85 +/- 0.07)E-05 erg/cm^2. The 1s peak photon flux measured
starting from T0+29.5 s in the 10-1000 keV band is
15.8 +/- 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 20985
Subject
GRB 170405A: Enhanced Swift-XRT position
Date
2017-04-05T20:38:10Z (9 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 368 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 170405A, 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 = 219.82767, -25.24368 which is equivalent
to:
RA (J2000): 14h 39m 18.64s
Dec (J2000): -25d 14' 37.3"
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 20984
Subject
GRB 170405A: Swift detection of a burst with an optical counterpart
Date
2017-04-05T18:50:16Z (9 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
E. Troja (NASA/GSFC/UMCP), S. D. Barthelmy (GSFC),
D. N. Burrows (PSU), S. B. Cenko (GSFC), A. Cholden-Brown (PSU),
A. D'Ai (INAF-IASFPA), F. E. Marshall (NASA/GSFC) and
M. H. Siegel (PSU) report on behalf of the Swift Team:
At 18:39:48 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 170405A (trigger=745797). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 219.810, -25.244, which is
RA(J2000) = 14h 39m 14s
Dec(J2000) = -25d 14' 36"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows multiple peaks
with a duration of about 180 sec. The peak count rate
was ~4500 counts/sec (15-350 keV), at ~4 sec after the trigger.
The XRT began observing the field at 18:41:49.0 UT, 120.6 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 219.8290, -25.2438 which is equivalent to:
RA(J2000) = +14h 39m 18.96s
Dec(J2000) = -25d 14' 37.7"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 61 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy.
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 128 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 14:39:18.72 = 219.82800
DEC(J2000) = -25:14:35.3 = -25.24315
with a 90%-confidence error radius of about 0.61 arc sec. This position is 3.7
arc sec. from the center of the XRT error circle. The estimated magnitude is
16.18 with a 1-sigma error of about 0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.09.
Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov).
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.)