The Global Oscillation Network Group (GONG) Project will place a network of instruments around the world to observe solar oscillations as continuously as possible for three years. The Project has now chosen the six network sites based on analysis of survey data from fifteen sites around the world. The chosen sites are: Big Bear Solar Observatory, California; Mauna Loa Solar Observatory, Hawaii: Learmonth Solar Observatory, Australia; Udaipur Solar Observatory, India; Observatorio del Teide, Tenerife; and Cerro Tololo Interamerican Observatory, Chile.

A moderate-resolution spectroscopic survey of Fleming's sample of 54 X-ray selected M dwarfs with photometric distances less than 25 pc is presented. All the objects consist of one or two dMe stars, some being doubles or spectroscopic binaries. Radial and rotation velocities have been measured by fits to the Halpha profiles. Radial velocities have been measured by cross correlation. Artificial broadening of an observed spectrum has produced a relationship between Halpha FWHM and rotation speed, which we use to infer rotation speeds for the entire sample by measurement of the Halpha emission line. We find three ultrafast rotators ( UFRs, v sin i greater than or equal to 100 km s(-1)) and eight stars with 30 km s(-1) v sin i < 100 km s(-1). We find that the UFRs have quite variable emission and should be observed for photometric variability. Cross-correlation velocities measured for UFRs are shown to depend on rotation speed and the filtering used. The radial velocity dispersion of the sample is 17 km s(-1). A new double emission line spectroscopic binary with a period of 3.55 days has been discovered, RX J1547.4+4507, and another known one is in the sample, the Hyades member RX J0442.5+2027. Three other objects are suspected spectroscopic binaries, and at least six are visual doubles. The only star in the sample observed to have significant lithium happens to be a known TW Hya association member, TWA 8A. These results all show that there are a number of young (<10(8) yr) and very young (<10(7) yr) low-mass stars in the immediate solar neighborhood. The Hα activity strength does not depend on rotation speed. Our fast rotators are less luminous than similarly fast rotators in the Pleiades. They are either younger than the Pleiades or gained angular momentum in a different way.

Pressure-induced lattice collapse was discovered in tetragonal (T) phase of single crystal Fe1.05Te at room temperature through x-ray and neutron-diffraction measurements. A remarkable compression along the c axis (similar to 5%) was observed upon increasing pressure from the ambient condition to 4 GPa. Indexed results demonstrate that the crystallographic structure remains unchanged after the collapse, revealing that the collapse does not break symmetry of crystal structure. The Fe-spin state change was proposed to account for the lattice collapse. The equations of state for the T phase and pressure-induced collapsed T phase were determined from the diffraction measurements.

The hyper-velocity star S5-HVS1, ejected 5 Myr ago from the Galactic Centre at 1800 km s(-1), was most likely produced by tidal break-up of a tight binary by the supermassive black hole SgrA*. Taking a Monte Carlo approach, we show that the former companion of S5-HVS1 was likely a main-sequence star between 1.2 and 6 M-circle dot and was captured into a highly eccentric orbit with pericentre distance in the range of 1-10 au and semimajor axis about 10(3) au. We then explore the fate of the captured star. We find that the heat deposited by tidally excited stellar oscillation modes leads to runaway disruption if the pericentre distance is smaller than about 3 au. Over the past 5 Myr, its angular momentum has been significantly modified by orbital relaxation, which may stochastically drive the pericentre inwards below 3 au and cause tidal disruption. We find an overall survival probability in the range 5 per cent to 50 per cent, depending on the local relaxation time in the close environment of the captured star, and the initial pericentre at capture. The pericentre distance of the surviving star has migrated to 10-100 au, making it potentially the most extreme member of the S-star cluster. From the ejection rate of S5-HVS1-like stars, we estimate that there may currently be a few stars in such highly eccentric orbits. They should be detectable (typically K-s less than or similar to 18.5 mag) by the GRAVITY instrument and by future Extremely Large Telescopes and hence provide an extraordinary probe of the spin of SgrA*.

An international project was successfully completed which involved two major undertakings: (1) a round-robin to demonstrate the viability of the selected standard and ( 2) the certification of the lattice parameters of the SRM 1990, a Standard Reference Material(R) for single crystal diffractometer alignment. This SRM is a set of approximate to 3500 units of Cr-doped Al2O3, or ruby spheres [ (0.420.011 mole fraction % C ( expanded uncertainty)]. The round-robin consisted of determination of lattice parameters of a pair of crystals: the ruby sphere as a standard, and a zeolite reference to serve as an unknown. Fifty pairs of crystals were dispatched from Hauptman-Woodward Medical Research Institute to volunteers in x-ray laboratories world-wide. A total of 45 sets of data was received from 32 laboratories. The mean unit cell parameters of the ruby spheres was found to be a = 4.7608 Angstrom +/- 0.0062 Angstrom, and c = 12.9979 Angstrom +/- 0.020 Angstrom ( 95 % intervals of the laboratory means). The source of errors of outlier data was identified. The SRM project involved the certification of lattice parameters using four well-aligned single crystal diffractometers at ( Bell Laboratories) Lucent Technologies and at NRC of Canada ( 39 ruby spheres), the quantification of the Cr content using a combined microprobe and SEM/EDS technique, and the evaluation of the mosaicity of the ruby spheres using a double-crystal spectrometry method. A confirmation of the lattice parameters was also conducted using a Guinier-Hagg camera. Systematic corrections of thermal expansion and refraction corrections were applied. These rubies are rhombohedral, with space group R 3 c. The certified mean unit cell parameters are a = 4.76080 +/- 0.00029 Angstrom, and c = 12.99568 Angstrom +/- 0.00087 Angstrom ( expanded uncertainty). These certified lattice parameters fall well within the results of those obtained from the international round-robin study. The Guinier-Hagg transmission measurements on five samples of powdered rubies ( a = 4.7610 Angstrom +/- 0.0013 Angstrom, and c = 12.9954 Angstrom +/- 0.0034 Angstrom) agreed well with the values obtained from the single crystal spheres.

The Perseverance rover has collected seven oriented samples of sedimentary rocks, all likely older than the oldest signs of widespread life on Earth, at the exposed base of the western fan in Jezero crater, Mars. The samples include a sulfate- and clay-bearing mudstone and sandstone, a fluvial sandstone from a stratigraphically low position at the fan front, and a carbonate-bearing sandstone deposited above the sulfate-bearing strata. All samples contain aqueously precipitated materials and most or all were aqueously deposited. Although the rover instruments have not confidently detected organic matter in the rocks from the fan front, the much more sensitive terrestrial instruments will still be able to search for remnants of prebiotic chemistries and past life, and study Mars's past habitability in the samples returned to Earth. The hydrated, sulfate-bearing mudstone has the highest potential to preserve organic matter and biosignatures, whereas the carbonate-bearing sandstones can be used to constrain when and for how long Jezero crater contained liquid water. Returned sample science analyses of sulfate, carbonate, clay, phosphate and igneous minerals as well as trace metals and volatiles that are present in the samples acquired at the fan front would provide transformative insights into past habitable environments on Mars, the evolution of its magnetic field, atmosphere and climate and the past and present cycling of atmospheric and crustal water, sulfur and carbon.