Articles in 2017

The nuclear region of NGC 1097 is found to be dominated by non-thermal pressure. An anti-correlation between the star formation efficiency of molecular clouds and the magnetic field strength indicates that the formation of massive stars is quenched.

We calculate the continuous nanohertz gravitational-wave emission from individual supermassive black hole binaries and the gravitational-wave background they generate, which will be observable with pulsar timing arrays.

The authors present a photon detector suitable for terahertz astronomy, with very high sensitivity, low power consumption and the ability to be configured into arrays. This device is demonstrably able to count individual far-infrared photons.

The inner four planets of the TRAPPIST-1 system experienced induction heating due to magnetic interaction with their host star. This led them to experience increased volcanic activity, outgassing and potentially a subsurface magma ocean.

Experiments are presented that indicate that methane can be produced abiotically on Mars through the photocatalytic reaction of CO₂, in a process called methanogenesis. Methane can then be shocked (through impacts) to form RNA nucleobases and glycine.

By assessing the ionization fraction of the environment around Tycho’s (type Ia) supernova, the authors have constrained the properties of its progenitor enough to rule out a hot, luminous white dwarf. A double white dwarf binary merger is allowed.

A candidate dual supermassive black hole system with a projected separation of 0.35 pc is found in the gas-rich interacting spiral galaxy NGC 7674, evidenced by a ∼0.7 kpc Z-shaped radio jet and two, possibly inverted-spectrum, compact radio cores.

The authors present a spectrophotometric and hydrodynamical study of supernova OGLE-2014-SN-073, which had remarkably high inferred ejecta mass and energy, potentially higher than can be explained with canonical core-collapse neutrino-driven explosions.

Rotation of the Galactic bar at the centre of the Milky Way can explain gaps and asymmetries in stellar stream Palomar 5. Similar streams close to the Galactic Centre are therefore unfit for probing the dark matter subhalo interactions in our Galaxy.

A previously unidentified class of variable stars has been found in OGLE survey data, characterized by periodic brightness variations on ~30-min timescales, amplitudes of ~0.3 mag and temperatures of ~30,000 K. They are potentially evolved low-mass stars.

Ultrarelativistic photons and neutrinos from gamma-ray bursts offer a testbed for quantum gravity effects that would lead to an energy dependence of the travel times. A statistical analysis of astrophysical data shows that this behaviour may have been observed.

The origin of Galactic positrons that produce gamma ray emission when annihilated is still debated. Mergers of two white dwarfs are likely to be the main source of these positrons. Such mergers produce sub-luminous, thermonuclear supernovae.

Using an innovative method, the mass of a pulsar can be constrained using the maximum ‘glitch’ in the star’s rotational frequency: the bigger the glitch, the lower the mass. This method is used to estimate the mass of all observed glitchers.

Liquid methane lakes dot Titan’s polar regions. Numerical models reveal that the creation of buoyant bubbles through nitrogen exsolution near the bed of the Ligeia Mare lake can explain transient brightenings observed by Cassini on the lake’s surface.

The stacking of nearly three-quarters of a million spectra has unearthed a previously unknown component of the Galactic halo: a widely distributed, neutral, excited hydrogen layer that could harbour a sizeable proportion of the Milky Way’s baryons.

Periodic pulsations of polarized emission and a strong magnetic field were found in a white-dwarf double system. These findings confirm a pulsar-like emission mechanism for the system that has so far been associated only with neutron stars.