A short GRB analogue with multi-wavelength followup, hypothesized to support a set of interpretations of the GW170817 event, was reported in Troja et al. 2018 (published October 16, 2018 in Nature https://www.nature.com/articles/s41467-018-06558-7.pdf). It must be emphasized that the authors do not restrict their conclusions to particular kilonova models favored by LIGO and collaborators:
“It’s a big step to go from one detected object to two. Our discovery tells us that events like GW170817 and GRB 150101B could represent a whole new class of erupting objects that turn on and off in X-rays and might actually be relatively common.”
Now, nearly a year later, a paper on data-dredged model-fit GRB160821B makes it clear that "exact" is so poorly defined as to be trivial.
"Despite the large number of free parameters, the FS properties are reasonably well constrained"
Troja et al. 2019 https://academic.oup.com/mnras/article/489/2/2104/5554752
"We can exclude dust as the origin of the observed red colour, and interpret it as evidence for a lanthanide-rich kilonova emission"
A lanthanide-rich off-axis observation is not equivalent to the blue "off-axis" (weak, broadband) interpretation of AT2017gfo spectra.
For background studies focusing on problems and phenomenological exceptions emerging through post-GW170817 analysis of its putative astrophysical source, please consult these resources:
https://fulguritics.blogspot.com/2018/10/why-is-information-on-ngc-4993.html
https://fulguritics.blogspot.com/2018/06/gw170817-occurs-at-green-bar.html
Many unusual (and often conflicting) observations - and conclusions reached - decorate GW170817/AT2017gfo, an assumed kilonova believed to be in NGC 4993. We can be more confident that AT2017gfo is behaving contrary to expectations informed by many discrete periods of observation dependent on putative (now openly-disputed) GW170817 strain data, from which crucial scaling statistics underlie all subsequent calculations, conditioning models. Further observation of the transient source in multiple wavelengths is plagued by use of erroneous light curves constructed from a non-coincident maze of uncertain luminosity distances and sky locations relative to foreground objects. As the electromagnetic transient over time have been re-scaled freely by researchers to suit theoretical demands.This practice has led to all post-merger models becoming mutually-incompatible, with little subsequent discussion. Unfortunately, a lack of follow-up observations available to researchers is plaguing the entire enterprise of gravitational wave astronomy and related branches of astrophysics and cosmology.
Troja et al. 2018 was published as Chandra – two weeks prior to publication - can no longer monitor the locations believed to be associated with the emission of GW170817/GRB170817A and GRB150101B https://phys.org/news/2018-10-nasa-space-telescope-orbit.html. The GRB150101B finding, however, had been submitted for publication by other researchers as early as August, 2016 https://arxiv.org/pdf/1608.08626.pdf.
The angular localization of a distant luminous transient utilizing such methods as employed for the recognition of GRB150101B is a highly imprecise exercise in induction from multiple nonstationary data sources with very wide systematic error: https://gcn.gsfc.nasa.gov/other/150101B.gcn3
https://rationalwiki.org/wiki/Texas_sharpshooter_fallacy
GRB150101B and GW170817 are both described as 'blue kilonovas' (lanthanide-poor) in Troja et al. 2018 and in other studies, due to their early flat and weak blue spectral evolution; an early confident fitting of a red kilonova model to GW170817 is, in retrospect, puzzling, as apparent strong spectral evidence of r-process lanthanide nucleosynthesis (associated with red kilonovas) can also be presented with equal confidence, given the length of avilable observations http://iopscience.iop.org/article/10.3847/2041-8213/aa905c/pdf:
"Optical light curves of short GRBs normalized to the observed gamma-ray energy release"
Normalization of electromagnetic data to an assumed spectral model scaled by a simple inverse square law can be circularly-bound to a cherry-picked source distance identified by an arbitrary selection rule, then
bolstered by Bayesian confidence in the expected hard spectrum from the mean
SED of previous short GRBs relative to the spectral dispersion GRB150101, which
yields apparent z-shift (like all other energy, luminosity, coordinate, and
mass parameters, a quantity only estimated after successive rescaling and
curve-fitting operations to suit posterior distributions within meager 68% confidence
bounds):
“X-ray light curves of short GRBs normalized to the observed gamma-ray energy release. The shaded area shows the 68% dispersion region.”
The above quote from Troja et al. 2018 is absolutely false. The optical emission of GW170817/GRB170817A/SSS17a/AT 2017gfo was visible within 11 hours of the putative LIGO GW signal (near-IR identified first by Swope), 15.3 hours later in UV (Swift), X-rays after 9 days (Chandra), and radio emission at 16 days (Jansky VLA) https://dcc.ligo.org/public/0145/P1700294/007/ApJL-MMAP-171017.pdf.“The optical afterglow of GRB170817A became visible >100 days after the merger and is not reported in the plot”
Many liberties have been taken to "confirm" the association of GRB150101B with the putative distance of its source transient, within an active hypothesis development regime:
"The earliest follow-up observations of GRB150101B were performed by the Swift satellite starting 1.5 days after the burst. Swift monitoring lasted for 4 weeks and shows a persistent X-ray source. The study of GRB150101B at X-ray energies is complicated by its proximity to a low-luminosity AGN, which contaminates the Swift measurements. Observations with the Chandra X-ray Observatory were critical to resolve the presence of the two nearby sources, and to characterize their properties. [... . ...] The flat Swift light curve, although dominated by the AGN contribution, provides an important indication on the behavior of the early GRB afterglow, which had to remain sub-dominant over the observed period. [... .] Two leading models are commonly adopted to describe the broadband afterglow evolution of GRB170817A: a highly relativistic structured jet seen off-axis, and a choked jet with a nearly isotropic mildly relativistic cocoon. We fit both models to the GRB150101B afterglow with a Bayesian MCMC parameter estimation scheme, using the same priors and afterglow parameters as in ref. https://arxiv.org/abs/1801.06516. For the structured jet, we assumed that the energy follows a Gaussian angular profile" https://www.nature.com/articles/s41467-018-06558-7Data presented by Troja et al. 2018 are rendered deceptively-comparable by log-log plotting or scaling to frame, presenting a highly-processed >350 keV photon count as a much more energetic trigger. Data are presented after weighting and mask subtraction informed by posterior fits to expected hypothetical models – of which only one family can be chosen (with one putative member: GW170817, also known as GRB170817A/SSS17a/AT 2017gfo). The proposed GW170817-like kilonova family does not fit the only two prior observations of short GRB-kilonova sequences – themselves very similar to each other (cf. GRB 080503 and GRB 130603B http://www.mpe.mpg.de/~jcg/grb080503.html).
"There were more high-energy gamma rays, above 50 billion electron volts, or GeV, than anyone predicted, the team reports. Weirder still, rays with energies above 100 GeV appeared only during the solar minimum, when the sun’s activity level was low. One photon emitted during the solar minimum had an energy as high as 467.7 GeV."Long TGF transients, extending >100 ms are not uncommon:
“Terrestrial gamma-ray flashes (TGFs) are gamma-ray bursts detected from space that are associated with lightning activity. In the present paper, we show that the shorter TGF durations (50 ms) recently discovered by the gamma-ray burst monitor (GBM) aboard the Fermi Gamma-Ray Space Telescope are consistent with the temporal dispersion associated with the Compton scattering of photons produced by an instantaneous TGF source. This new result suggests that short TGF pulses observed from satellites correspond to very short TGF sources with durations less than ~10 ms and that the observed long TGF pulses (≳100 ms) may be due to overlapping of emissions produced by a sequence of elementary processes with much shorter temporal durations.”
Celestin and Pasko 2012 https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2011GL050342
The Livingston GW1701817 signal was contaminated by a glitch for the same period that the delayed LIGO Hanford signal exceeds background noise amplitude. Virgo detected nothing, which was interpreted to indicate that the Fermi-INTEGRAL signal also originated in a >30 deg2 blind spot for the Virgo station:
https://gcn.gsfc.nasa.gov/other/G298048.gcn3“Investigation of L1 data identified a noise transient from a known class
of instrumental glitches during the inspiral signal. The duration of this
glitch is a small fraction of a second and does not appear to affect the
signal at times away from the glitch. To make an improved preliminary
estimate of the sky position, we re-analyzed the data, removing the L1
noise transient at GPS time 1187008881.389 by multiplying the strain data
with a Tukey window, such that the total duration of the zeroed data is
0.2 s and the total duration of the Tukey window is 1.2 s.”
The GW150914 transient signal also has a strict duration of 0.2 seconds: https://fulguritics.blogspot.com/2018/06/progress-on-ligo-event-analysis-here.html
A Prior kilonova observation by Hubble (first image), showing very convincing collocation of an anomalous luminous transient within a critical co-boundary of a galactic shell. Indistinguishable distances between Milky Way foreground stars and both putative GW170817 and GRB150101B sources complicate observations (2nd and 3rd images):
http://hubblesite.org/pubinfo/pdf/2013/29/pdf.pdf
http://chandra.si.edu/photo/2017/2nstars/
Fong et al 2018 (draft dated February 22, 2018), showing galactic core at center, which saturates observations prior to application of synthetic models derived from ensuing GRB170817A/GW170817 research https://arxiv.org/pdf/1608.08626.pdf
Galactic core is ambiguously visualized with saturated GRB150101B, which may be deceptive upon a cursory reading, resembling a compact pair: https://www.nature.com/articles/s41467-018-06558-7
Solar activity during GRB150101B was intriguing, with three C-class flares and definite shock arrival and substorm oscillation throughout the day; a polar coronal hole, as expected to be common during solar maximum, grows, while sunspot number increases by 7 to >100; the time of arrival of GRB150101B at 15:23 UTC corresponds to a bifurcation in several interplanetary magnetic field time series https://www.spaceweatherlive.com/en/archive/2015/01/01:
All images processed uniformly to reveal nonstationary, masks, artifacts, and incompatible resolution between epochs/exposures, in which subtle effects combining luminous covariation of objects, scintillation, scattering/polarization/absorption by dust and gas, and extinction may be considered:
