13 research outputs found
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The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. I. Discovery of the Optical Counterpart Using the Dark Energy Camera
We present the Dark Energy Camera (DECam) discovery of the optical counterpart of the first binary neutron star merger detected through gravitational-wave emission, GW170817. Our observations commenced 10.5 hr post-merger, as soon as the localization region became accessible from Chile. We imaged 70 deg 2 in the i and z bands, covering 93% of the initial integrated localization probability, to a depth necessary to identify likely optical counterparts (e.g., a kilonova). At 11.4 hr post-merger we detected a bright optical transient located from the nucleus of NGC 4993 at redshift z = 0.0098, consistent (for km s -1 Mpc -1 ) with the distance of 40 ±8 Mpc reported by the LIGO Scientific Collaboration and the Virgo Collaboration (LVC). At detection the transient had magnitudes of and , and thus an absolute magnitude of , in the luminosity range expected for a kilonova. We identified 1500 potential transient candidates. Applying simple selection criteria aimed at rejecting background events such as supernovae, we find the transient associated with NGC 4993 as the only remaining plausible counterpart, and reject chance coincidence at the 99.5% confidence level. We therefore conclude that the optical counterpart we have identified near NGC 4993 is associated with GW170817. This discovery ushers in the era of multi-messenger astronomy with gravitational waves and demonstrates the power of DECam to identify the optical counterparts of gravitational-wave sources.Funding for the DES Projects has been provided by the DOE and NSF(USA), MEC/MICINN/MINECO (Spain), STFC (UK), HEFCE (UK). NCSA (UIUC), KICP (U.Chicago), CCAPP (OhioState), MIFPA (TexasA&M), CNPQ, FAPERJ, FINEP (Brazil), DFG (Germany) and the Collaborating Institutions in the Dark Energy Survey. For further information please visit the publisher's website
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The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. II. UV, Optical, and Near-infrared Light Curves and Comparison to Kilonova Models
We present UV, optical, and NIR photometry of the first electromagnetic
counterpart to a gravitational wave source from Advanced LIGO/Virgo, the binary
neutron star merger GW170817. Our data set extends from the discovery of the
optical counterpart at days to days post-merger, and includes
observations with the Dark Energy Camera (DECam), Gemini-South/FLAMINGOS-2
(GS/F2), and the {\it Hubble Space Telescope} ({\it HST}). The spectral energy
distribution (SED) inferred from this photometry at days is well
described by a blackbody model with K, a radius of cm (corresponding to an expansion velocity of ), and a bolometric luminosity of erg
s. At days we find a multi-component SED across the optical and
NIR, and subsequently we observe rapid fading in the UV and blue optical bands
and significant reddening of the optical/NIR colors. Modeling the entire data
set we find that models with heating from radioactive decay of Ni, or
those with only a single component of opacity from -process elements, fail
to capture the rapid optical decline and red optical/NIR colors. Instead,
models with two components consistent with lanthanide-poor and lanthanide-rich
ejecta provide a good fit to the data, the resulting "blue" component has
M and
c, and the "red" component has
M and
c. These ejecta masses are broadly
consistent with the estimated -process production rate required to explain
the Milky Way -process abundances, providing the first evidence that BNS
mergers can be a dominant site of -process enrichment
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The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. I. Discovery of the Optical Counterpart Using the Dark Energy Camera
We present the Dark Energy Camera (DECam) discovery of the optical counterpart of the first binary neutron star merger detected through gravitational-wave emission, GW170817. Our observations commenced 10.5 hr post-merger, as soon as the localization region became accessible from Chile. We imaged 70 deg2 in the i and z bands, covering 93% of the initial integrated localization probability, to a depth necessary to identify likely optical counterparts (e.g., a kilonova). At 11.4 hr post-merger we detected a bright optical transient located from the nucleus of NGC 4993 at redshift z = 0.0098, consistent (for km s-1 Mpc-1) with the distance of 40 ±8 Mpc reported by the LIGO Scientific Collaboration and the Virgo Collaboration (LVC). At detection the transient had magnitudes of and , and thus an absolute magnitude of , in the luminosity range expected for a kilonova. We identified 1500 potential transient candidates. Applying simple selection criteria aimed at rejecting background events such as supernovae, we find the transient associated with NGC 4993 as the only remaining plausible counterpart, and reject chance coincidence at the 99.5% confidence level. We therefore conclude that the optical counterpart we have identified near NGC 4993 is associated with GW170817. This discovery ushers in the era of multi-messenger astronomy with gravitational waves and demonstrates the power of DECam to identify the optical counterparts of gravitational-wave sources
Impact of PhACs on Soil Microorganisms
International audienceThe use of reclaimed water in crop irrigation helps to mitigate water shortage. The fertilization of arable soils with sewage sludge, biosolids, or livestock manure reduces extensive application of synthetic fertilizers. However, both practices lead to the introduction of pharmaceutical active compounds (PhACs) in arable soil, known to host a wide range of living organisms, including microorganisms which are supporting numerous ecosystem services. In soils, the fate of PhACs is governed by different abiotic and biotic processes. Among them, soil sorption and microbial transformation are the most important ones and determine the fate, occurrence, and dispersion of PhACs into the different compartments of the environment. The presence of PhACs in soils can compromise the abundance, diversity, and activity of the soil microbial community which is one of the key players in a range of soil ecosystem services. This chapter reviews the current knowledge of the effects of PhACs, commonly found in wastewater effluents and derived organic fertilizers, on the soil microbial community