Aims. Uncovering the ingredients and the architecture of planetary systems is a very active field of research that has fuelled many new theories on giant planet formation, migration, composition, and interaction with the circumstellar environment. We aim at discovering and studying new such systems, to further expand our knowledge of how low-mass companions form and evolve. Methods. We obtained high-contrast H-band images of the circumstellar environment of the F5V star HD 206893, known to host a debris disc never detected in scattered light. These observations are part of the SPHERE High Angular Resolution Debris Disc Survey (SHARDDS) using the InfraRed Dual-band Imager and Spectrograph (IRDIS) installed on VLT/SPHERE. Results. We report the detection of a source with a contrast of 3.6 × 10 −5 in the H-band, orbiting at a projected separation of 270 milliarcsec or 10 au, corresponding to a mass in the range 24 to 73 M Jup for an age of the system in the range 0.2 to 2 Gyr. The detection was confirmed ten months later with VLT/NaCo, ruling out a background object with no proper motion. A faint extended emission compatible with the disc scattered light signal is also observed. Conclusions. The detection of a low-mass companion inside a massive debris disc makes this system an analog of other young planetary systems such as β Pictoris, HR 8799 or HD 95086 and requires now further characterisation of both components to understand their interactions.

We observed a nearby millisecond pulsar J2124-3358 with the Hubble Space Telescope in broad far-UV (FUV) and optical filters. The pulsar is detected in both bands with fluxes F (1250-2000Å) = (2.5 ± 0.3) × 10 −16 erg s −1 cm −2 and F (3800 − 6000Å) = (6.4 ± 0.4) × 10 −17 erg s −1 cm −2 , which correspond to luminosities of ≈ 5.8 × 10 27 and 1.4 × 10 27 erg s −1 , for d = 410 pc and E(B − V ) = 0.03. The optical-FUV spectrum can be described by a power-law model, f ν ∝ ν α , with slope α = 0.18-0.48 for a conservative range of color excess, E(B − V ) = 0.01-0.08. Since a spectral flux rising with frequency is unusual for pulsar magnetospheric emission in this frequency range, it is possible that the spectrum is predominantly magnetospheric (power law with α < 0) in the optical while it is dominated by thermal emission from the neutron star surface in the FUV. For a neutron star radius of 12 km, the surface temperature would be between 0.5 × 10 5 and 2.1 × 10 5 K, for α ranging from −1 to 0, E(B − V ) = 0.01-0.08, and d = 340-500 pc. In addition to the pulsar, the FUV images reveal extended emission spatially coincident with the known Hα bow shock, making PSR J2124-3358 the second pulsar (after PSR J0437−4715) with a bow shock detected in FUV.

We report on a Hubble Space Telescope detection of the nearby, old pulsar B0950+08 (d 262 pc, spin-down age 17.5 Myr) in two far-ultraviolet (FUV) bands. We measured the mean flux densitiesf ν = 109 ± 6 nJy and 83 ± 14 nJy in the F125LP and F140LP filters (pivot wavelengths 1438 and 1528Å). Using the FUV data together with previously obtained optical-UV data, we conclude that the optical-FUV spectrum consists of two components -a nonthermal (presumably magnetospheric) power-law spectrum (f ν ∝ ν α ) with slope α ∼ −1.2 and a thermal spectrum emitted from the bulk of the neutron star surface with a temperature in the range of (1-3) × 10 5 K, depending on interstellar extinction and neutron star radius. These temperatures are much higher than predicted by neutron star cooling models for such an old pulsar, which means that some heating mechanisms operate in neutron stars. A plausible mechanism responsible for the high temperature of PSR B0950+08 is the interaction of vortex lines of the faster rotating neutron superfluid with the slower rotating normal matter in the inner neutron star crust (vortex creep heating).

We report non-detections of the ∼ 3 × 10 8 yr old, slow, isolated, rotation-powered pulsar PSR J2144-3933 in observations with the Hubble Space Telescope in one optical band (F475X) and two farultraviolet bands (F125LP and F140LP), yielding upper bounds F F475X < 22.7 nJy, F F125LP < 5.9 nJy, F F140LP < 19.5 nJy, at the pivot wavelengths 4940Å, 1438Å and 1528Å, respectively. Assuming a blackbody spectrum, we deduce a conservative upper bound on the surface (unredshifted) temperature of the pulsar of T < 42, 000 K. This makes PSR J2144-3933 the coldest known neutron star, allowing us to study thermal evolution models of old neutron stars. This temperature is consistent with models with either direct or modified Urca reactions including rotochemical heating, and, considering frictional heating from the motion of neutron vortex lines, it puts an upper bound on the excess angular momentum in the neutron superfluid, J < 10 44 erg s.

Red giant asteroseismology can provide valuable information for studying the Galaxy as demonstrated by space missions like CoRoT and Kepler. However, previous observations have been limited to small data sets and fields-of-view. The TESS mission provides far larger samples and, for the first time, the opportunity to perform asteroseimic inference from full-frame images full-sky, instead of narrow fields and pre-selected targets. Here, we seek to detect oscillations in TESS data of the red giants in the Kepler field using the 4-yr Kepler results as benchmark. Because we use 1-2 sectors of observation, our results are representative of the typical scenario from TESS data. We detect clear oscillations in ∼3000 stars with another ∼1000 borderline (low S/N) cases. In comparison, best-case predictions suggests ∼4500 detectable oscillating giants. Of the clear detections, we measure Δν in 570 stars, meaning a ∼20 per cent Δν yield (14 per cent for one sector and 26 per cent for two sectors). These yields imply that typical (1-2 sector) TESS data will result in significant detection biases. Hence, to boost the number of stars, one might need to use only νmax as the seismic input for stellar property estimation. However, we find little bias in the seismic measurements and typical scatter is about 5–6 per cent in νmax and 2-3 per cent in Δν. These values, coupled with typical uncertainties in parallax, Teff, and [Fe/H] in a grid-based approach, would provide internal uncertainties of 3 per cent in inferred stellar radius, 6 per cent in mass and 20 per cent in age for low-luminosity giant stars. Finally, we find red giant seismology is not significantly affected by seismic signal confusion from blending for stars with Tmag ≲ 12.5.