James R. A. Davenport et al 2019 ApJ 871 241

Analysis of a sample of 347 Kepler flare stars shows that flare activity decreases for all low-mass stars as they spin down, and thus with age.

D. S. Aguado et al 2019 ApJS 240 23

Twelve years after first light, SDSS is putting out its 15th data release — which includes 4,824 Mapping Nearby Galaxies at APO (MaNGA) data cubes, as well as new data analysis and visualization products.

Kosuke Namekata et al 2019 ApJ 871 187

An analysis of 5,356 active solar-type stars observed by Kepler reveals that starspot lifetimes are ~10–350 days when spot areas are 0.1%–2.3% of the solar hemisphere, shorter than expected in analogy with the Sun.

Scott J. Kenyon and Benjamin C. Bromley 2019 AJ 157 79

N-body simulations disfavor undiscovered satellites in the Pluto–Charon system inside Hydra’s orbit; orbits with a semimajor axis >1.1x that of Hydra, on the other hand, are stable on timescales >150–300 Myr.

B. van der Holst et al 2019 ApJL 872 L18

Predictions of the first Parker Solar Probe close encounter suggest that the probe was close to the heliospheric current sheet, the trajectory was in the slow solar wind, and the plasma along the trajectory was unstable.

Karina T. Voggel et al 2019 ApJ 871 159

The supermassive black hole number density caused by stripped galaxy nuclei is estimated at 0.002–0.008 Mpc⁻³, representing a significant fraction (8%–32%) of the supermassive black hole density in the local universe.