On 17 August 2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo interferometer detected gravitational waves (GWs) emanating from a binary neutron star merger, ...GW170817. Nearly simultaneously, the Fermi and INTEGRAL (INTErnational Gamma-Ray Astrophysics Laboratory) telescopes detected a gamma-ray transient, GRB 170817A. At 10.9 hours after the GW trigger, we discovered a transient and fading optical source, Swope Supernova Survey 2017a (SSS17a), coincident with GW170817. SSS17a is located in NGC 4993, an S0 galaxy at a distance of 40 megaparsecs. The precise location of GW170817 provides an opportunity to probe the nature of these cataclysmic events by combining electromagnetic and GW observations.
On 17 August 2017, Swope Supernova Survey 2017a (SSS17a) was discovered as the optical counterpart of the binary neutron star gravitational wave event GW170817. We report time-series spectroscopy of ...SSS17a from 11.75 hours until 8.5 days after the merger. Over the first hour of observations, the ejecta rapidly expanded and cooled. Applying blackbody fits to the spectra, we measured the photosphere cooling from
11,000
−
900
+
3400
to
9300
−
300
+
300
kelvin, and determined a photospheric velocity of roughly 30% of the speed of light. The spectra of SSS17a began displaying broad features after 1.46 days and evolved qualitatively over each subsequent day, with distinct blue (early-time) and red (late-time) components. The late-time component is consistent with theoretical models of r-process–enriched neutron star ejecta, whereas the blue component requires high-velocity, lanthanide-free material.
The merging neutron star gravitational-wave event GW170817 has been observed throughout the entire electromagnetic spectrum from radio waves to γ-rays. The resulting energetics, variability, and ...light curves are shown to be consistent with GW170817 originating from the merger of two neutron stars, in all likelihood followed by the prompt gravitational collapse of the massive remnant. The available γ-ray, X-ray, and radio data provide a clear probe for the nature of the relativistic ejecta and the non-thermal processes occurring within, while the ultraviolet, optical, and infrared emission are shown to probe material torn during the merger and subsequently heated by the decay of freshly synthesized r-process material. The simplest hypothesis, that the non-thermal emission is due to a low-luminosity short γ-ray burst (sGRB), seems to agree with the present data. While low-luminosity sGRBs might be common, we show here that the collective prompt and multi-wavelength observations are also consistent with a typical, powerful sGRB seen off-axis. Detailed follow-up observations are thus essential before we can place stringent constraints on the nature of the relativistic ejecta in GW170817.
Abstract
We present an analysis of the host-galaxy environment of Swope Supernova Survey 2017a (SSS17a), the discovery of an electromagnetic counterpart to a gravitational-wave source, GW170817. ...SSS17a occurred 1.9 kpc (in projection; 10.″2) from the nucleus of NGC 4993, an S0 galaxy at a distance of 40 Mpc. We present a
Hubble Space Telescope
(
HST
) pre-trigger image of NGC 4993,
Magellan
optical spectroscopy of the nucleus of NGC 4993 and the location of SSS17a, and broadband UV-through-IR photometry of NGC 4993. The spectrum and broadband spectral-energy distribution indicate that NGC 4993 has a stellar mass of
log
(
M
/
M
⊙
)
=
10.49
−
0.20
+
0.08
and star formation rate of 0.003
M
⊙
yr
−1
, and the progenitor system of SSS17a likely had an age of >2.8 Gyr. There is no counterpart at the position of SSS17a in the
HST
pre-trigger image, indicating that the progenitor system had an absolute magnitude
M
V
>
−
5.8
mag. We detect dust lanes extending out to almost the position of SSS17a and >100 likely globular clusters associated with NGC 4993. The offset of SSS17a is similar to many short gamma-ray-burst offsets, and its progenitor system was likely bound to NGC 4993. The environment of SSS17a is consistent with an old progenitor system such as a binary neutron star system.
Cutaneous small vessel vasculitis secondary to COVID‐19 infection: a case report Mayor‐Ibarguren, A.; Feito‐Rodriguez, M.; Quintana Castanedo, L. ...
JEADV. Journal of the European Academy of Dermatology and Venereology/Journal of the European Academy of Dermatology and Venereology,
October 2020, Letnik:
34, Številka:
10
Journal Article
Eleven hours after the detection of gravitational wave source GW170817 by the Laser Interferometer Gravitational-Wave Observatory and Virgo Interferometers, an associated optical transient, SSS17a, ...was identified in the galaxy NGC 4993. Although the gravitational wave data indicate that GW170817 is consistent with the merger of two compact objects, the electromagnetic observations provide independent constraints on the nature of that system. We synthesize the optical to near-infrared photometry and spectroscopy of SSS17a collected by the One-Meter Two-Hemisphere collaboration, finding that SSS17a is unlike other known transients. The source is best described by theoretical models of a kilonova consisting of radioactive elements produced by rapid neutron capture (the r-process). We conclude that SSS17a was the result of a binary neutron star merger, reinforcing the gravitational wave result.
We discovered Swope Supernova Survey 2017a (SSS17a) in the LIGO/Virgo Collaboration (LVC) localization volume of GW170817, the first detected binary neutron star (BNS) merger, only 10.9 hr after the ...trigger. No object was present at the location of SSS17a only a few days earlier, providing a qualitative spatial and temporal association with GW170817. Here, we quantify this association, finding that SSS17a is almost certainly the counterpart of GW170817, with the chance of a coincidence being ≤ (90% confidence). We arrive at this conclusion by comparing the optical properties of SSS17a to other known astrophysical transients, finding that SSS17a fades and cools faster than any other observed transient. For instance, SSS17a fades >5 mag in g within 7 days of our first data point, while all other known transients of similar luminosity fade by <1 mag during the same time period. Its spectra are also unique, being mostly featureless, even as it cools. The rarity of "SSS17a-like" transients combined with the relatively small LVC localization volume and recent non-detection imply the extremely unlikely chance coincidence. We find that the volumetric rate of SSS17a-like transients is ≤ Gpc−3 yr−1 and the Milky Way rate is per century. A transient survey designed to discover similar events should be high cadence and observe in red filters. The LVC will likely detect substantially more BNS mergers than current optical surveys will independently discover SSS17a-like transients, however a 1 day cadence survey with the Large Synoptic Survey Telescope (LSST) could discover an order of magnitude more events.
Resumen Introducción Debido a las características electromagnéticas únicas del microhilo amorfo magnetoelástico, los cambios en la presión de un fluido provocarán una variación de la tensión mecánica ...sobre el sensor, lo que supondrá una variación de su imanación que será detectable de forma inalámbrica. Utilizando esta tecnología, se podrá desarrollar un sistema inalámbrico para el seguimiento de procedimientos en cirugía vascular. Métodos El sensor diseñado consiste en un anillo de microhilo magnetoelástico que se integró en un modelo in vitro con flujo pulsátil. Se simularon distintos grados de estenosis en distintas localizaciones, tanto en arteria bovina como en un segmento de PTFE. Se realizó el análisis de Fourier de las señales registradas, y se emplearon el test de correlación de Pearson y curvas COR para el análisis de la información. Resultados Se obtuvo un índice de correlación de Pearson de 0,945 (p < 0,001) entre la presión invasiva del fluido y la potencia de la señal emitida por el microhilo magnetoelástico en arteria bovina. Se obtuvieron unas excelentes curvas COR, tanto en el caso de las estenosis preanastomóticas (AUC 0,98; IC 95%: 0,97-1) y anastomóticas (AUC 0,93; IC 95%: 0,86-0,99), como en el caso de las estenosis distales (AUC 0,88; IC 95%: 0,79-0,98), comparadas con un grupo control. Conclusiones El microhilo magnetoelástico es capaz de detectar, localizar y cuantificar el grado de estenosis en arteria bovina, así como en una anastomosis latero-terminal, con una elevada potencia estadística. Por primera vez se ha desarrollado un sensor inalámbrico in vitro para el seguimiento postoperatorio de los procedimientos en cirugía vascular.
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