59 research outputs found

    Influence of surface density on the CO2 photoreduction activity of a DC magnetron sputtered TiO2 catalyst

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    Advancing in the photocatalyst scale-up is crucial for the development of highly efficient solar fuels production at industrial scale. Here, we report DC-magnetron sputtering as a suitable technique to produce photocatalytic TiO2 coatings for CO2 reduction with a view on process scalability. The crystallinity of the obtained TiO2 coatings varies with surface density, with amorphous or quasi-amorphous coatings obtained with very low densities, while UV light absorption coefficients show the opposite trend, which has been related to the proportionally higher abundace of surface defects and grain boundaries associated to the small crystal size and/or amorphicity of the lightest coatings. The as-prepared samples lead to the reduction of CO2 as demonstrated by 13C isotope tracing. An optimum catalyst area density of 1 g/m2 (by geometric area) is obtained in terms of CO2 photoreduction production, which is ascribed to a compromise situation between crystallinity and absorption coefficient. Selectivity to the different reaction products also varies with the coating characteristics, with amorphous or quasi-amorphous light coatings favouring methanol formation, in contrast with the preferred CO evolution in heavier, crystalline ones. Raman spectroscopy reveals the formation of peroxo and peroxocarbonate species on the photocatalyst surface as oxidation products during the CO2 reduction, the accummulation of which is proposed to be related to the observed catalyst deactivation

    Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift during the LIGO-Virgo Run O3b

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    We search for gravitational-wave signals associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (2019 November 1 15:00 UTC-2020 March 27 17:00 UTC). We conduct two independent searches: A generic gravitational-wave transients search to analyze 86 GRBs and an analysis to target binary mergers with at least one neutron star as short GRB progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these GRBs. A weighted binomial test of the combined results finds no evidence for subthreshold gravitational-wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each GRB. Finally, we constrain the population of low-luminosity short GRBs using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate. © 2022. The Author(s). Published by the American Astronomical Society

    Open data from the third observing run of LIGO, Virgo, KAGRA, and GEO

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    The global network of gravitational-wave observatories now includes five detectors, namely LIGO Hanford, LIGO Livingston, Virgo, KAGRA, and GEO 600. These detectors collected data during their third observing run, O3, composed of three phases: O3a starting in 2019 April and lasting six months, O3b starting in 2019 November and lasting five months, and O3GK starting in 2020 April and lasting two weeks. In this paper we describe these data and various other science products that can be freely accessed through the Gravitational Wave Open Science Center at https://gwosc.org. The main data set, consisting of the gravitational-wave strain time series that contains the astrophysical signals, is released together with supporting data useful for their analysis and documentation, tutorials, as well as analysis software packages

    Search for gravitational-wave transients associated with magnetar bursts in advanced LIGO and advanced Virgo data from the third observing run

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    Gravitational waves are expected to be produced from neutron star oscillations associated with magnetar giant f lares and short bursts. We present the results of a search for short-duration (milliseconds to seconds) and longduration (∼100 s) transient gravitational waves from 13 magnetar short bursts observed during Advanced LIGO, Advanced Virgo, and KAGRA’s third observation run. These 13 bursts come from two magnetars, SGR1935 +2154 and SwiftJ1818.0−1607. We also include three other electromagnetic burst events detected by FermiGBM which were identified as likely coming from one or more magnetars, but they have no association with a known magnetar. No magnetar giant flares were detected during the analysis period. We find no evidence of gravitational waves associated with any of these 16 bursts. We place upper limits on the rms of the integrated incident gravitational-wave strain that reach 3.6 × 10−²³ Hz at 100 Hz for the short-duration search and 1.1 ×10−²² Hz at 450 Hz for the long-duration search. For a ringdown signal at 1590 Hz targeted by the short-duration search the limit is set to 2.3 × 10−²² Hz. Using the estimated distance to each magnetar, we derive upper limits upper limits on the emitted gravitational-wave energy of 1.5 × 1044 erg (1.0 × 1044 erg) for SGR 1935+2154 and 9.4 × 10^43 erg (1.3 × 1044 erg) for Swift J1818.0−1607, for the short-duration (long-duration) search. Assuming isotropic emission of electromagnetic radiation of the burst fluences, we constrain the ratio of gravitational-wave energy to electromagnetic energy for bursts from SGR 1935+2154 with the available fluence information. The lowest of these ratios is 4.5 × 103

    Solar hydrogen production from ethanol-water vapours over metal/TiO2 photocatalysts supported on β-SiC alveolar foams

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    In this work, we have explored the feasibility of alveolar open-cell β-SiC foams as catalyst support for solar hydrogen production. For that purpose, Pt and Ru nanoparticles have been obtained, by means of photoassisted synthesis, on TiO2-coated foams and tested in gas-phase hydrogen production from water-ethanol mixtures in a tubular reactor coupled to a compound parabolic solar collector (CPC). Subnanometre-sized metal or metal/oxide nanoparticles are obtained for Pt/TiO2/SiC and Ru/TiO2/SiC foams, respectively, where co-catalyst nanoparticles decorate the TiO2 coating which in turn is attached to the SiC foam through an amorphous SiO2 washcoat formed by SiC pre-calcination. In solar photocatalytic reactions, all of the assayed foam-supported photocatalysts are active for the production of hydrogen, with Pt/TiO2 ones being the most active and foam pore size exerting little influence on hydrogen outcome. In the best conditions, 14 % UV-to-hydrogen (equivalent to 0.49 % solar-to-hydrogen) conversion efficiency, with photonic efficiency higher than 30 %, is attained. © 2023 The AuthorsThis work has received financial support from Spanish MCIN/AEI/ 10.13039/501100011033 and “ERDF A way of making Europe”, through projects PID2020–118593RB-C22 and ENE2017-89170-R, from Comunidad de Madrid European Structural Funds through FotoArt-CM project (S2018/NMT-4367), and from the European Research Council (ERC) through the HyMAP project, grant agreement no. 648319. The University of Strasbourg IdEx Program is thanked for funding the PhD fellowship of Javier Ivanez.Data will be made available on request.Peer reviewe

    A search using GEO600 for gravitational waves coincident with fast radio bursts from SGR 1935+2154

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    International audienceThe magnetar SGR 1935+2154 is the only known Galactic source of fast radio bursts (FRBs). FRBs from SGR 1935+2154 were first detected by CHIME/FRB and STARE2 in 2020 April, after the conclusion of the LIGO, Virgo, and KAGRA Collaborations' O3 observing run. Here we analyze four periods of gravitational wave (GW) data from the GEO600 detector coincident with four periods of FRB activity detected by CHIME/FRB, as well as X-ray glitches and X-ray bursts detected by NICER and NuSTAR close to the time of one of the FRBs. We do not detect any significant GW emission from any of the events. Instead, using a short-duration GW search (for bursts \leq 1 s) we derive 50% (90%) upper limits of 104810^{48} (104910^{49}) erg for GWs at 300 Hz and 104910^{49} (105010^{50}) erg at 2 kHz, and constrain the GW-to-radio energy ratio to 10141016\leq 10^{14} - 10^{16}. We also derive upper limits from a long-duration search for bursts with durations between 1 and 10 s. These represent the strictest upper limits on concurrent GW emission from FRBs

    Search for gravitational waves emitted from SN 2023ixf

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    International audienceWe present the results of a search for gravitational-wave transients associated with core-collapse supernova SN 2023ixf, which was observed in the galaxy Messier 101 via optical emission on 2023 May 19th, during the LIGO-Virgo-KAGRA 15th Engineering Run. We define a five-day on-source window during which an accompanying gravitational-wave signal may have occurred. No gravitational waves have been identified in data when at least two gravitational-wave observatories were operating, which covered 14%\sim 14\% of this five-day window. We report the search detection efficiency for various possible gravitational-wave emission models. Considering the distance to M101 (6.7 Mpc), we derive constraints on the gravitational-wave emission mechanism of core-collapse supernovae across a broad frequency spectrum, ranging from 50 Hz to 2 kHz where we assume the GW emission occurred when coincident data are available in the on-source window. Considering an ellipsoid model for a rotating proto-neutron star, our search is sensitive to gravitational-wave energy 1×105Mc21 \times 10^{-5} M_{\odot} c^2 and luminosity 4×105Mc2/s4 \times 10^{-5} M_{\odot} c^2/\text{s} for a source emitting at 50 Hz. These constraints are around an order of magnitude more stringent than those obtained so far with gravitational-wave data. The constraint on the ellipticity of the proto-neutron star that is formed is as low as 1.041.04, at frequencies above 12001200 Hz, surpassing results from SN 2019ejj

    Search for gravitational waves emitted from SN 2023ixf

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    International audienceWe present the results of a search for gravitational-wave transients associated with core-collapse supernova SN 2023ixf, which was observed in the galaxy Messier 101 via optical emission on 2023 May 19th, during the LIGO-Virgo-KAGRA 15th Engineering Run. We define a five-day on-source window during which an accompanying gravitational-wave signal may have occurred. No gravitational waves have been identified in data when at least two gravitational-wave observatories were operating, which covered 14%\sim 14\% of this five-day window. We report the search detection efficiency for various possible gravitational-wave emission models. Considering the distance to M101 (6.7 Mpc), we derive constraints on the gravitational-wave emission mechanism of core-collapse supernovae across a broad frequency spectrum, ranging from 50 Hz to 2 kHz where we assume the GW emission occurred when coincident data are available in the on-source window. Considering an ellipsoid model for a rotating proto-neutron star, our search is sensitive to gravitational-wave energy 1×105Mc21 \times 10^{-5} M_{\odot} c^2 and luminosity 4×105Mc2/s4 \times 10^{-5} M_{\odot} c^2/\text{s} for a source emitting at 50 Hz. These constraints are around an order of magnitude more stringent than those obtained so far with gravitational-wave data. The constraint on the ellipticity of the proto-neutron star that is formed is as low as 1.041.04, at frequencies above 12001200 Hz, surpassing results from SN 2019ejj

    Search for gravitational waves emitted from SN 2023ixf

    No full text
    International audienceWe present the results of a search for gravitational-wave transients associated with core-collapse supernova SN 2023ixf, which was observed in the galaxy Messier 101 via optical emission on 2023 May 19th, during the LIGO-Virgo-KAGRA 15th Engineering Run. We define a five-day on-source window during which an accompanying gravitational-wave signal may have occurred. No gravitational waves have been identified in data when at least two gravitational-wave observatories were operating, which covered 14%\sim 14\% of this five-day window. We report the search detection efficiency for various possible gravitational-wave emission models. Considering the distance to M101 (6.7 Mpc), we derive constraints on the gravitational-wave emission mechanism of core-collapse supernovae across a broad frequency spectrum, ranging from 50 Hz to 2 kHz where we assume the GW emission occurred when coincident data are available in the on-source window. Considering an ellipsoid model for a rotating proto-neutron star, our search is sensitive to gravitational-wave energy 1×105Mc21 \times 10^{-5} M_{\odot} c^2 and luminosity 4×105Mc2/s4 \times 10^{-5} M_{\odot} c^2/\text{s} for a source emitting at 50 Hz. These constraints are around an order of magnitude more stringent than those obtained so far with gravitational-wave data. The constraint on the ellipticity of the proto-neutron star that is formed is as low as 1.041.04, at frequencies above 12001200 Hz, surpassing results from SN 2019ejj
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