Narrowband Searches for Continuous and Long-duration Transient Gravitational Waves from Known Pulsars in the LIGO-Virgo Third Observing Run

Isolated neutron stars that are asymmetric with respect to their spin axis are possible sources of detectable continuous gravitational waves. This paper presents a fully coherent search for such signals from eighteen pulsars in data from LIGO and Virgo's third observing run (O3). For known pulsars, efficient and sensitive matched-filter searches can be carried out if one assumes the gravitational radiation is phase-locked to the electromagnetic emission. In the search presented here, we relax this assumption and allow both the frequency and the time derivative of the frequency of the gravitational waves to vary in a small range around those inferred from electromagnetic observations. We find no evidence for continuous gravitational waves, and set upper limits on the strain amplitude for each target. These limits are more constraining for seven of the targets than the spin-down limit defined by ascribing all rotational energy loss to gravitational radiation. In an additional search, we look in O3 data for long-duration (hours-months) transient gravitational waves in the aftermath of pulsar glitches for six targets with a total of nine glitches. We report two marginal outliers from this search, but find no clear evidence for such emission either. The resulting duration-dependent strain upper limits do not surpass indirect energy constraints for any of these targets. © 2022. The Author(s). Published by the American Astronomical Society

Constraints on the cosmic expansion history from GWTC–3

We use 47 gravitational wave sources from the Third LIGO–Virgo–Kamioka Gravitational Wave Detector Gravitational Wave Transient Catalog (GWTC–3) to estimate the Hubble parameter H(z), including its current value, the Hubble constant H0. Each gravitational wave (GW) signal provides the luminosity distance to the source, and we estimate the corresponding redshift using two methods: the redshifted masses and a galaxy catalog. Using the binary black hole (BBH) redshifted masses, we simultaneously infer the source mass distribution and H(z). The source mass distribution displays a peak around 34 M⊙, followed by a drop-off. Assuming this mass scale does not evolve with the redshift results in a H(z) measurement, yielding ${H}_{0}={68}_{-8}^{+12}\,\mathrm{km}\ \,\ {{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ (68% credible interval) when combined with the H0 measurement from GW170817 and its electromagnetic counterpart. This represents an improvement of 17% with respect to the H0 estimate from GWTC–1. The second method associates each GW event with its probable host galaxy in the catalog GLADE+, statistically marginalizing over the redshifts of each event's potential hosts. Assuming a fixed BBH population, we estimate a value of ${H}_{0}={68}_{-6}^{+8}\,\mathrm{km}\ \,\ {{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ with the galaxy catalog method, an improvement of 42% with respect to our GWTC–1 result and 20% with respect to recent H0 studies using GWTC–2 events. However, we show that this result is strongly impacted by assumptions about the BBH source mass distribution; the only event which is not strongly impacted by such assumptions (and is thus informative about H0) is the well-localized event GW190814

Anomalous alkaline sulphate fluids produced in a magmatic hydrothermal system : Savo, Solomon Islands

In magmatic-hydrothermal and associated geothermal systems, acidic magmatic-derived fluids (pH5) geothermal fluids are typically limited to lateral outflows some distance from the main vent. Here we describe an unusual hydrothermal system associated with Savo volcano, a recently active (1830–40) trachyte-dominated island arc stratovolcano in the Solomon Islands. Hot springs (~100°C) near to the volcanic crater discharge alkaline waters instead of the more commonly recognised acidic fluids. The hydrothermal system of Savo dominantly discharges sinter and travertine-forming alkaline sulphate (pH 7–8) waters at hot springs on its upper flanks, in addition to a small number of lower discharge acid sulphate springs (pH 2–7). Alkaline sulphate springs discharge dilute, chloride-poor (600 mg/l) and silica-rich (>250 mg/l) fluids. They have restricted δ34SSO4 (5.4 ± 1.5‰) and δ18OH2O values (−4‰; local non-thermal groundwater is −8‰). Acid sulphate springs discharge low chloride (<20 mg/l), high sulphate (300–800 mg/l) waters, with variable silica (100–300 mg/l) and distinctly lower δ34SSO4 values (−0.6 ± 2.5‰) compared to the alkaline sulphate fluids. They also display high δ18OH2O and δDH2O relative to non-thermal groundwater. Geochemical modelling shows that water–rock reaction and dilution in the presence of secondary anhydrite, pyrite and quartz leads to chloride being diluted to low concentrations, whilst maintaining high sulphate and silica concentrations in the fluid. Strontium, oxygen and hydrogen isotopes confirm water–rock reaction and mixing with groundwater as primary controls on the composition of the alkaline sulphate springs. The highly unusual dilute chemistry of all discharges at Savo is a consequence of high regional rainfall, i.e. climatic control, and results from open system mixing at depth between hydrothermal and meteoric waters