GRB 170817A
GCN Circular 21520
Subject
GRB 170817A: Fermi GBM detection
Date
2017-08-17T20:00:07Z (8 years ago)
From
Andreas von Kienlin at MPE <azk@mpe.mpg.de>
A. von Kienlin (MPE), C. Meegan (UAH) and A. Goldstein (USRA)
report on behalf of the Fermi GBM Team:
"At 12:41:06.47 UT on 17 August 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 170817A (trigger 524666471 / 170817529).
The on-ground calculated location, using the GBM trigger
data, is RA = 176.8, DEC = -39.8 (J2000 degrees,
equivalent to 12 h 47 m, -39 d 48'), with an uncertainty
of 11.6 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).
The angle from the Fermi LAT boresight at the GBM trigger time is 91 degrees.
The GRB light curve shows a weak short pulse
with a duration (T90) of about 2 s (50-300 keV).
The time-averaged spectrum from T0-0.512 s to 2.048 s is
well fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.89 +/- 0.5 and
the cutoff energy, parameterized as Epeak, is 82 +/- 21 keV
The event fluence (10-1000 keV) in this time interval is
(2.3 +/- 0.4)E-07 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0-0.32 s in the 8-1000 keV band
is 1.9 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 22372
Subject
GW170817/GRB170817A: Preliminary results of Chandra monitoring
Date
2018-01-29T20:42:49Z (7 years ago)
From
Eleonora Troja at GSFC <eleonora.troja@nasa.gov>
E. Troja (UMD/GSFC) and L. Piro (INAF/IAPS) report on behalf of
a larger collaboration:
The Chandra X-ray Observatory re-observed the field of GW170817
starting on January 17th, 2018, and performed five short exposures
observations as part of its on-going monitoring program (PI: Wilkes).
Only three of these exposures (ObsID: 20936, 20938, 20939) are currently
archived and available to the public. Here we report the preliminary
findings
from these observations.
The X-ray afterglow is detected with high significance in all the exposures
at an average count rate of 0.0016 cts/s in the 0.5-8.0 keV energy band.
A preliminary inspection of the hardness ratio does not show any
significant
spectral variation. Therefore, we perform a spectral analysis using an
absorbed
power-law model with absorption column fixed at the Galactic value of
7.5E20 cm^-2 and a photon index Gamma=1.575 as derived from our broadband
analysis (Troja et al. 2018, arXiv:1801.06516).
We derive an unabsorbed X-ray flux of (3.2 +/- 0.3)E-14 erg/cm2/s in the
0.3-10 keV energy band. The quoted error is at the 68% confidence level.
This new measurement is higher than the value measured by Chandra
at ~110 days (~2.5E-14 erg/cm2/s, Troja et al. 2018), and higher than the
value measured by XMM-Newton at ~135 days (D'Avanzo et al., 2018).
The latest measurement is consistent with a rising afterglow with F~t^0.8,
although, within the errors, a slow turn-over of the X-ray light curve
cannot be excluded.
Further analysis is on-going.
GCN Circular 22374
Subject
GW170817/GRB170817A: Updated results from the full Chandra dataset
Date
2018-01-30T13:00:12Z (7 years ago)
From
Eleonora Troja at GSFC <eleonora.troja@nasa.gov>
E. Troja (UMD/GSFC) and L. Piro (INAF/IAPS) report on behalf of
a larger collaboration:
We analyzed the full set of five observations of GW170817
performed by the Chandra X-ray Observatory between January 17th
and January 28th, 2018, i.e. ~153 and ~164 days after the merger.
A log of observations is reported below:
ObsID Exposure [ks] 0.5-8.0 keV count rate [cts/s]
20936 31.75 0.0018 +/- 0.0002
20937 20.77 0.0014 +/- 0.0003
20938 15.86 0.0019 +/- 0.0003
20939 22.25 0.0011 +/- 0.0002
20945 14.22 0.0010 +/- 0.0003
The average net count-rate is 0.00148 +/- 0.00011 cts/s,
consistent with the value of 0.00145 +/- 0.00014 observed
at 110 days (Troja et al. 2018, arXiv:1801.06516).
The average spectrum, obtained by coadding the five exposures,
is well described by an absorbed power-law model with
N_H=7.5E20 cm^-2 and photon index Gamma=1.65+/-0.16 (68% c.l.),
consistent with the value derived from the broadband spectrum
at earlier times (Troja et al. 2018, arXiv:1801.06516).
Based on this new analysis, we estimate an unabsorbed X-ray flux
of (2.6 +/- 0.3)E-14 erg/cm2/s (68% c.l.) in the 0.3-10 keV band,
consistent with the X-ray flux measured at 110 days.
Our results do not support the claim of a decreasing X-ray flux,
as suggested by D'Avanzo et al. (2018, arXiv:1801.06164), and
are consistent either with a slowly rising afterglow or a slow
turn-over of the X-ray light curve expected when the afterglow
reaches its peak (e.g. Lazzati et al. 2017, arXiv:1712.03237;
Troja et al. 2018, arXiv:1801.06516).
We note that the X-ray afterglow displays a marginal level of
variability on timescales of a few days, being the count-rate
from the last two exposures (20939,20945) consistently lower.
The spectrum from these two observations is characterized by a
photon index Gamma= 1.9 +/- 0.3 (68% c. l.), slightly softer
than the value measured in the first three exposures (20936,20937,
and 20938) Gamma = 1.59+/-0.17 (68% c. l.), yet consistent within
the large uncertainties. The lower count-rate and soft spectral
shape could be indicative of the cooling frequency entering the
X-ray band, although the limited statistics prevent us to draw
any firm conclusion.
GCN Circular 22763
Subject
GW170817/GRB170817A: LBT optical detection
Date
2018-06-05T14:03:37Z (7 years ago)
From
Andrea Rossi at INAF <a.rossi@iasfbo.inaf.it>
A. Rossi (INAF-OAS), M. Cantiello (INAF-OA Abruzzo) V. Testa, D. Paris
(INAF-OAR), A. Melandri, S. Covino, O. S. Salafia, P. D'Avanzo, S.
Campana (INAF-OAB), L. Nicastro, E. Palazzi, F. Cusano (INAF-OAS), G.
Stratta (Urbino University/INFN Firenze), R. Carini, S. Piranomonte, E.
Brocato (INAF-OAR), V. D'Elia (ASDC), and M. Branchesi (GSSI) report on
behalf of the GRAWITA collaboration and its partners:
We observed the optical counterpart of GRB 170817A (Kienlin et al., GCN
21520) associated to GW 170817 (LVC GCN Circ. 21509, 21513) with the LBC
imager mounted on the Large Binocular Telescope (Mt Graham, AZ, USA).
Observations were performed in the r-sloan filter on 2018-01-23, i.e.,
~160 days after the GW/GRB trigger.
At the location of the optical transient (e.g., Coulter et al., GCN
21529; Adams et al., 21816) we detect the optical afterglow of GRB
170817A with magnitude r-sloan=26.2+-0.4, calibrated against Pan-STARRS
field stars. Image analysis was performed after preliminary removal of
an elliptical model of the underlying host galaxy from each single
frame. However, some residual emission is left which contributes for
~0.2 mags to the uncertainty of the photometry.
Our detection is the first one from a ground-based optical telescope. It
is in agreement with a turnover/flattening in the optical light curve of
GW 170817/GRB 170817A as inferred by Alexander at al. 2018
(arXiv:1805.02870) and with the overall flattening/declining temporal
evolution observed in the X-ray and radio bands (D'Avanzo et al. 2018,
A&A, 613 L1; Hajela et al. GCN Circ. 22692; Troja et al. GCN Circ.
22693; Dobie et al. arXiv:1803.06853; Alexander at al. 2018;
arXiv:1805.02870).
We acknowledge the excellent support from the LBT staff in obtaining
these observations.
GCN Circular 33638
Subject
GRB 170817A: an awesome GCN Circular
Date
2023-10-17T18:45:03Z (2 years ago)
From
Leo Singer at NASA/GSFC <leo.p.singer@nasa.gov>
Via
Web form
AT2017gfo was a dope kilonova, but I also hear that there were X-ray and UV observations in arXiv:1710.05437