GRB 160422A
GCN Circular 19359
Subject
GRB 160422A: XRT Afterglow Confirmation
Date
2016-04-28T13:38:27Z (10 years ago)
From
Alessandro Maselli at INAF/IASF Palermo <maselli@ifc.inaf.it>
A. Maselli (INAF-IASFPA), D. Malesani (DARK/NBI), K.L. Page and P.A.
Evans (U. Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has conducted further observations of the field of the
Fermi-detected burst GRB 160422A (Yassine et al., GCN Circ. 19329; Burns
et al., GCN Circ. 19331), extending from T0+400 ks to T0+470 ks after
the Fermi/GBM trigger.
At the position of the candidate afterglow reported by Maselli et al.
(GCN Circ. 19334) no source is detected in the new observation, with a
three sigma upper limit of 2.6e-3 ct/s. This confirms that it was the
X-ray afterglow of GRB 160422A.
The results of the full analysis of the XRT observations are available
at http://www.swift.ac.uk/xrt_products/00020605
This circular is an official product of the Swift-XRT team.
GCN Circular 19352
Subject
GRB 160422A: GROND NIR afterglow detection
Date
2016-04-26T11:17:40Z (10 years ago)
From
Jan Bolmer at MPE/Garching <jan@bolmer.de>
T. Schweyer, J. Bolmer, J. Greiner (all MPE Garching), and D. A. Kann
(TLS Tautenburg) report on behalf of the GROND team:
We observed the field of GRB 160422A (Fermi/GBM trigger 483019143;
Yassine et al., GCN #19329) 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 23:02 UT on 22-04-2016, 11.06 hrs after the
GRB trigger. They were performed at an average seeing of 2.0" and at
an average airmass of 2.2, but also through thick cirrus, which
prevented proper measurements in g'r'i'z'.
We found a single point source coincident with the 0.45" Swift-UVOT
error circle reported by Marshall et al. (GCN #19333).
Based on the first 4 min of total exposures in JHK, we estimate
preliminary magnitudes (all in AB system) of
J = 17.9 +/- 0.3 mag,
H = 17.4 +/- 0.3 mag, and
K > 17.0 mag.
Given magnitudes are calibrated against 2MASS field stars 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 (Schlafly & Finkbeiner 2011).
GCN Circular 19346
Subject
GRB 160422A: Swift/UVOT Afterglow Confirmation
Date
2016-04-26T02:00:23Z (10 years ago)
From
Frank Marshall at GSFC <femarsha@khamseen.gsfc.nasa.gov>
F. E. Marshall (NASA/GSFC) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 160422A
32624 s after the LAT trigger (Yassine et al., GCN Circ. 19329).
The optical afterglow candidate (Marshall, GCN Circ. 19333)
has faded in a later observation in the same filter.
Its positional consistency with the XRT source
(Maselli et al. GCN Circ. 19334) and its fadiing
behavior confirm that it is the optical afterglow of GRB 160422A.
The preliminary UVOT position is:
RA (J2000) = 02:48:22.78 = 42.09493 (deg.)
Dec (J2000) = -57:52:30.4 = -57.87512 (deg.)
with an estimated uncertainty of 0.45 arc sec. (radius, 90% confidence).
Preliminary detections 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 33427 34064 627 19.50 � 0.05
white 44903 44701 785 19.91 � 0.06
v 39970 45820 320 19.29 � 0.23
u 32624 33420 783 19.09 � 0.10
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 19345
Subject
GRB 160422A: CALET Gamma-Ray Burst Monitor detection
Date
2016-04-26T01:27:37Z (10 years ago)
From
Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp>
S. Ricciarini (U of Florence), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama,
Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), I. Takahashi (IPMU),
Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U),
W. Ishizaki (ICRR), M. L. Cherry (LSU), P. S. Marrocchesi (U of Siena)
and the CALET collaboration:
The long-duration GRB 160422A (Burns et al., GCN circ. 19331; Yassine et al.,
GCN circ. 19329; INTEGRAL-ACS #7450) triggered the CALET Gamma-Ray Burst Monitor (CGBM)
at 11:59:08.28 on 22 April 2016. The burst signal was only seen by the SGM instrument.
This fact is consistent that the GRB location of the Fermi-LAT (Yassine et al.,
GCN circ. 19329) was outside the field of view of the CALET CALorimeter (CAL) instrument,
which has the capability to observe gamma-rays above 1 GeV, at the trigger time.
The boresight angle of the SGM to the Fermi-LAT position was ~105 deg.
The light curve of the SGM shows at least two episodes. The first episode starts at
T0-7 sec, peaks at T0-6 sec and ends at T0-4 sec. The second episode shows the emission
starting at T0, peaking at T0+1 sec and ending at T0+4 sec. The T90 duration measured by
the SGM data is 8.7 +- 0.3 sec (100-1000 keV).
The CGBM data used in this analysis are provided by the Waseda CALET Operation Center
located at the Waseda University.
GCN Circular 19334
Subject
GRB 160422A: Swift-XRT afterglow detection
Date
2016-04-23T05:15:14Z (10 years ago)
From
Alessandro Maselli at INAF/IASF Palermo <maselli@ifc.inaf.it>
A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), B. Sbarufatti
(INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), J.P. Osborne
(U. Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester), P.
D'Avanzo (INAF-OAB) and P.A. Evans (U. Leicester) report on behalf of
the Swift-XRT team:
Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 160422A (Yassine et al. GCN Circ. 19329),
collecting 4.9 ks of Photon Counting (PC) mode data between T0+32.6 ks
and T0+45.8 ks.
Three uncatalogued X-ray sources are detected inside or close to the
Fermi/LAT error region, of which one ("Source 1") is above the RASS
limit, and is therefore likely the GRB afterglow. The position of this
source is RA, Dec=42.0947, -57.8757 which is equivalent to:
RA (J2000): 02:48:22.74
Dec(J2000): -57:52:32.6
with an uncertainty of 3.6 arcsec (radius, 90% confidence). This
position is 2.0 arcmin from the Fermi/LAT position and 2.6 arcsec from
the Swift-UVOT candidate optical afterglow (Marshall, GCN Circ. 19333).
The light curve can be modelled with a power-law decay with a decay
index of alpha=1.3 (+/-1.0).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.3 (+0.4, -0.3). The
best-fitting absorption column is 2.4 (+1.3, -1.0) x 10^21 cm^-2, in
excess of the Galactic value of 2.3 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 3.1 x 10^-11 (5.1 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 2.4 (+1.3, -1.0) x 10^21 cm^-2
Galactic foreground: 2.3 x 10^20 cm^-2
Excess significance: 3.5 sigma
Photon index: 2.3 (+0.4, -0.3)
If the light curve continues to decay with a power-law decay index of
1.3, the count rate at T+24 hours will be 0.017 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.2 x
10^-13 (8.5 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/ToO_GRBs/00020605/index_1.php.
The results of the full analysis of the XRT observations are available
at http://www.swift.ac.uk/ToO_GRBs/00020605.
This circular is an official product of the Swift-XRT team.
GCN Circular 19333
Subject
GRB 160422A: Swift/UVOT Candidate Afterglow
Date
2016-04-23T00:48:34Z (10 years ago)
From
Frank Marshall at GSFC <femarsha@khamseen.gsfc.nasa.gov>
F. E. Marshall (NASA/GSFC)
reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 160422A
32624 s after the LAT trigger (Yassine et al. GCN Circ. 19329).
A candidate optical afterglow
is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 02:48:22.79 = 42.09497 (deg.)
Dec (J2000) = -57:52:30.4 = -57.87511 (deg.)
with an estimated uncertainty of 0.45 arc sec. (radius, 90% confidence).
Preliminary detections 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 33427 34064 627 19.71 +/- 0.07
u 32624 33420 783 19.05 +/- 0.11
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 OPS NOTE(25apr16), Per author's request, the LAT reference was corrected.]
GCN Circular 19331
Subject
GRB 160422A: Fermi GBM observation
Date
2016-04-22T21:44:08Z (10 years ago)
From
Eric Burns at U of Alabama <eb0016@uah.edu>
E. Burns (UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 11:59:00.81 UT on 22 April 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160422A (trigger 483019144 / 160422499).
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 to
the LAT location is 53 degrees. The GBM on-ground location is
consistent with the LAT location (Yassine et al., GCN 19329).
The GBM light curve consists of a single main peak
with a duration (T90) of about 12 s (50-300 keV).
The time-averaged spectrum from T0 s to T0+13.1 s is
well fit by a Band function with Epeak = 242 +/- 4 keV,
alpha = -0.95 +/- 0.01, and beta = -2.42 +/- 0.04.
The event fluence (10-1000 keV) in this time interval is
(8.68 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+8.0 s in the 10-1000 keV band
is 93.8 +/- 0.6 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 19330
Subject
GRB 160422A: Swift ToO observations
Date
2016-04-22T20:11:16Z (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 team:
Swift has initiated a ToO observation of the Fermi/LAT GRB 160422A.
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020605
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Fermi/LAT event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a
GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular 19329
Subject
GRB 160422A: Fermi-LAT Detection
Date
2016-04-22T19:26:41Z (10 years ago)
From
Judith Racusin at GSFC <judith.racusin@nasa.gov>
M. Yassine (LUPM, Montpellier), J. L. Racusin (NASA/GSFC), and N. Omodei (Stanford) report on
behalf of the Fermi-LAT team:
Fermi LAT detected high-energy emission associated with GRB 160422A, which was also detected
by Fermi GBM (trigger 483019143 / 160422499) at 11:59:00.81 on April 22, 2016.
The best LAT on-ground location is found to be:
RA, Dec (J2000) = 42.05, -57.9
with an error radius of 0.07 deg (90% containment, statistical error only).
This was 80 deg from the LAT boresight at the time of the trigger, and triggered an autonomous
repoint of the spacecraft. The GRB became unocculted by the Earth and entered the LAT field
of view at ~T0+400 seconds.
The data from the Fermi-LAT show a significant increase in the event rate that is spatially correlated
with the trigger with high significance.
The highest-energy photon is a 12 GeV event which is observed 770 seconds after the GBM trigger.
A Swift ToO has been requested for this burst.
The Fermi-LAT point of contact for this burst is Manal Yassine (manal.yassine@lupm.in2p3.fr).
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.