The Mass of the MACHO-LMC-5 Lens Star

We combine the available astrometric and photometric data for the 1993 microlensing event MACHO-LMC-5 to measure the mass of the lens, M=0.097 +/- 0.016 Msun. This is the most precise direct mass measurement of a single star other than the Sun. In principle, the measurement error could be reduced as low as 10% by improving the trig parallax measurement using, for example, the Space Interferometry Mission. Further improvements might be possible by rereducing the original photometric lightcurve using image subtraction or by obtaining new, higher-precision baseline photometry of the source. We show that the current data strongly limit scenarios in which the lens is a dark (i.e., brown-dwarf) companion to the observed M dwarf rather than being the M dwarf itself. These results set the stage for a confrontation between mass estimates of the M dwarf obtained from spectroscopic and photometric measurements and a mass measurement derived directly from the star's gravitational influence. This would be the first such confrontation for any isolated star other than the Sun

The Aquarius Co-Moving Group is Not a Disrupted Classical Globular Cluster

We present a detailed analysis of high-resolution, high S/N spectra for 5 Aquarius stream stars observed with the MIKE spectrograph on the Magellan Clay telescope. Our sample represents one third of the 15 known members in the stream. We find the stream is not mono-metallic: the metallicity ranges from [Fe/H] = -0.63 to -1.58. No anti-correlation in Na-O abundances is present, and we find a strong positive Mg-Al relationship, similar to that observed in the thick disk. We find no evidence that the stream is a result of a disrupted classical globular cluster, contrary to a previously published claim. High [(Na, Ni, alpha)/Fe] and low [Ba/Y] abundance ratios in the stream suggests it is not a tidal tail from a disrupted dwarf galaxy, either. The stream is chemically indistinguishable from Milky Way field stars with the exception of one candidate, C222531-145437. From its position, velocity, and detailed chemical abundances, C222531-145437 is likely a star that was tidally disrupted from omega-Centauri. We propose the Aquarius stream is Galactic in origin, and could be the result from a disk-satellite perturbation in the Milky Way thick disk on the order of a few Gyr ago: derived orbits, UVW velocities, and angular momenta of the Aquarius members offer qualitative support for our hypothesis. Assuming C222531-145437 is a tidally disrupted member of omega-Centauri, this system is the most likely disk perturber. In the absence of compelling chemical and/or dynamical evidence that the Aquarius stream is the tidal tail of a disrupted satellite, we advocate the "Aquarius group" as a more appropriate description. Like the Canis Major over-density, as well as the Hercules and Monoceros groups, the Aquarius group joins the list of kinematically-identified substructures that are not actually accreted material: they are simply part of the rich complexity of the Milky Way structure.Comment: Accepted to MNRAS. Updated to journal versio

Adaptive response of neonatal sepsis-derived Group B Streptococcus to bilirubin

This work was funded by the Neonatal Unit Endowment Fund, Aberdeen Maternity Hospital. RH is funded by a career researcher fellowship from NHS Research Scotland. SG was funded by the MRC Flagship PhD programme. We are grateful for the support of Dr Phil Cash and Aberdeen Proteomics, at University of Aberdeen, in completing this project. Supplementary information accompanies this paper at https://doi.org/10.1038/s41598-018-24811-3.Peer reviewedPublisher PD

Gamma-ray burst precursors from tidally resonant neutron star oceans: potential implications for GRB 211211A

Precursor emission has been observed seconds to minutes before some short gamma-ray bursts. While the origins of these precursors remain unknown, one potential explanation relies on the resonance of neutron star pulsational modes with the tidal forces during the inspiral phase of a compact binary merger. In this paper, we present a model for short gamma-ray burst precursors which relies on tidally resonant neutron star oceans. In this scenario, the onset of tidal resonance in the crust-ocean interface mode corresponds to the ignition of the precursor flare, possibly through the interaction between the excited neutron star ocean and the surface magnetic fields. From just the precursor total energy, the time before the main event, and a detected quasi-periodic oscillation frequency, we may constrain the binary parameters and neutron star ocean properties as never before. Our model can immediately distinguish neutron star-black hole mergers from binary neutron star mergers without gravitational wave detection. We apply our model to GRB 211211A, the recently detected long duration short gamma-ray burst with a quasi-periodic precursor, and explore the parameters of this system within its context. The precursor of GRB 211211A is consistent with a tidally resonant neutron star ocean explanation that requires an extreme-mass ratio NSBH merger and a high mass neutron star. While difficult to reconcile with the gamma-ray burst main emission and associated kilonova, our results constrain the possible precursor generating mechanisms in this system. A systematic study of short gamma-ray burst precursors with the model presented here can test precursor origin and could probe the possible connection between gamma-ray bursts and neutron star-black hole mergers.Comment: 9 pages, 2 figures, accepted in MNRA

Detection and molecular characterisation of Cryptosporidium parvum in British European hedgehogs (Erinaceus europaeus)

Surveillance was conducted for the occurrence of protozoan parasites of the genus Cryptosporidium in European hedgehogs (Erinaceus europaeus) in Great Britain. In total, 108 voided faecal samples were collected from hedgehogs newly admitted to eight wildlife casualty treatment and rehabilitation centres. Terminal large intestinal (LI) contents from three hedgehog carcasses were also analysed. Information on host and location variables, including faecal appearance, body weight, and apparent health status, was compiled. Polymerase Chain Reaction (PCR) targeting the 18S ribosomal RNA gene, confirmed by sequencing, revealed an 8% (9/111) occurrence of Cryptosporidium parvum in faeces or LI contents, with no significant association between the host or location variables and infection. Archived small intestinal (SI) tissue from a hedgehog with histological evidence of cryptosporidiosis was also positive for C. parvum by PCR and sequence analysis of the 18S rRNA gene. No other Cryptosporidium species were detected. PCR and sequencing of the glycoprotein 60 gene identified three known zoonotic C. parvum subtypes not previously found in hedgehogs: IIdA17G1 (n=4), IIdA19G1 (n=1) and IIdA24G1 (n=1). These subtypes are also known to infect livestock. Another faecal sample contained C. parvum IIcA5G3j which has been found previously in hedgehogs, and for which there is one published report in a human, but is not known to affect livestock. The presence of zoonotic subtypes of C. parvum in British hedgehogs highlights a potential public health concern. Further research is needed to better understand the epidemiology and potential impacts of Cryptosporidium infection in hedgehogs

Experimentally Quantifying the Advantages of Weak-Value-Based Metrology

We experimentally investigate the relative advantages of implementing weak-value-based metrology versus standard methods. While the techniques outlined herein apply more generally, we measure small optical beam deflections both using a Sagnac interferometer with a monitored dark port (the weak-value-based technique), and by focusing the entire beam to a split detector (the standard technique). By introducing controlled external transverse detector modulations and transverse beam deflection momentum modulations, we quantify the mitigation of these sources in the weak-value-based experiment versus the standard focusing experiment. The experiments are compared using a combination of deterministic and stochastic methods. In all cases, the weak-value technique performs the same or better than the standard technique by up to two orders of magnitude in precision for our parameters. We further measure the statistical efficiency of the weak-value-based technique. By postselecting on 1% of the photons, we obtain 99% of the available Fisher information of the beam deflection parameter

The Mass of the MACHO-LMC-5 Lens Star

We combine the available astrometric and photometric data for the 1993 microlensing event MACHO-LMC-5 to measure the mass of the lens, M=0.097 +/- 0.016 Msun. This is the most precise direct mass measurement of a single star other than the Sun. In principle, the measurement error could be reduced as low as 10% by improving the trig parallax measurement using, for example, the Space Interferometry Mission. Further improvements might be possible by rereducing the original photometric lightcurve using image subtraction or by obtaining new, higher-precision baseline photometry of the source. We show that the current data strongly limit scenarios in which the lens is a dark (i.e., brown-dwarf) companion to the observed M dwarf rather than being the M dwarf itself. These results set the stage for a confrontation between mass estimates of the M dwarf obtained from spectroscopic and photometric measurements and a mass measurement derived directly from the star's gravitational influence. This would be the first such confrontation for any isolated star other than the Sun.Comment: 20 pages inc 3 fig, submitted to Ap