Direct imaging discovery of a super-Jovian around the young Sun-like star AF Leporis

Expanding the sample of directly imaged companions to nearby, young stars that are amenable to detailed astrometric and spectroscopic studies is critical for the continued development and validation of theories of their evolution and atmospheric processes. The recent release of the {\it Gaia} astrometric catalogue allows us to efficiently search for these elusive companions by targeting those stars that exhibit the astrometric reflex motion induced by an orbiting companion. The nearby (27 pc), young (24 Myr) star AF Leporis (AF Lep) was targeted because of its astrometric acceleration, consistent with a wide-orbit planetary companion detectable with high-contrast imaging. We used the SPHERE instrument on the VLT to search for faint substellar companions in the immediate vicinity of AF Lep. We used observations of a nearby star interleaved with those of AF Lep to efficiently subtract the residual point spread function. This provided sensitivity to faint planetary-mass companions within 1 arcsec (∼30 au) of the star. We detected the companion AF Lep b at a separation of 339 mas (9 au), within the inner edge of its unresolved debris disk. The measured K-band contrast and the age of the star yield a model-dependent mass of 4 and 6 MJup, consistent with the mass derived from an orbital fit of 4.3+2.9−1.2 MJup. The near-infrared SED of the planet is consistent with an object at the L--T spectral type transition, but under-luminous with respect to field-gravity objects. AF Lep b joins a growing number of substellar companions imaged around stars in the young β Pic moving group. With a mass of between 3 and 7 MJup, it occupies a gap in this isochronal sequence between the hotter, more massive companions like PZ~Tel~B and β~Pic~b, and the cooler 51~Eri~b, which is sufficiently cool for methane to form within its photosphere.
http://arxiv.org/abs/2302.06332

A red giant orbiting a black hole

We report spectroscopic and photometric follow-up of a dormant black hole (BH) candidate from Gaia DR3. We show that the system, which we call Gaia BH2, contains a ∼1M⊙ red giant and a dark companion with mass M2=8.9±0.3M⊙ that is very likely a BH. The orbital period, Porb=1277 days, is much longer than that of any previously studied BH binary. Our radial velocity (RV) follow-up over a 6-month period spans most of the orbit's dynamic range in RV and is in excellent agreement with predictions of the Gaia solution. UV imaging and high-resolution optical spectra rule out all plausible luminous companions that could explain the orbit. The star is a bright (G=12.3), slightly metal-poor ([Fe/H]=−0.22) low-luminosity giant (Teff=4600K; R=7.9R⊙; log[g/(cms−2)]=2.6). The binary's orbit is moderately eccentric (e=0.52). The giant is strongly enhanced in α−elements, with [α/Fe]=+0.26, but the system's Galactocentric orbit is typical of the thin disk. We obtained X-ray and radio nondetections of the source near periastron, which support BH accretion models in which the net accretion rate at the horizon is much lower than the Bondi-Hoyle-Lyttleton rate. At a distance of 1.16 kpc, Gaia BH2 is the second-nearest known BH, after Gaia BH1. Its orbit -- like that of Gaia BH1 -- seems too wide to have formed through common envelope evolution. Gaia BH1 and BH2 have orbital periods at opposite edges of the Gaia DR3 sensitivity curve, perhaps hinting at a bimodal intrinsic period distribution for wide BH binaries. Dormant BH binaries like Gaia BH1 and Gaia BH2 likely significantly outnumber their close, X-ray bright cousins, but their formation pathways remain uncertain.
http://arxiv.org/abs/2302.07880