ISPY-NACO Imaging Survey for Planets around Young stars

Abstract

Context. The occurrence rate of long-period (a 50 au) giant planets around young stars is highly uncertain since it is not only governed by the protoplanetary disc structure and planet formation process, but also reflects both dynamical re-structuring processes after planet formation as well as possible capture of planets not formed in situ. Direct imaging is currently the only feasible method to detect such wide-orbit planets and constrain their occurrence rate. Aims. We aim to detect and characterise wide-orbit giant planets during and shortly after their formation phase within protoplanetary and debris discs around nearby young stars. Methods. We carry out a large L -band high-contrast direct imaging survey for giant planets around 200 young stars with protoplanetary or debris discs using the NACO instrument at the ESO Very Large Telescope on Cerro Paranal in Chile. We use very deep angular differential imaging observations with typically >60 • field rotation, and employ a vector vortex coronagraph where feasible to achieve the best possible point source sensitivity down to an inner working angle of about 100 mas. This paper introduces the NACO Imaging Survey for Planets around Young stars (NACO-ISPY), its goals and strategy, the target list, and data reduction scheme, and presents preliminary results from the first 2.5 survey years. Results. We achieve a mean 5 σ contrast of ∆L = 6.4 ± 0.1 mag at 150 mas and a background limit of L bg = 16.5 ± 0.2 mag at >1. 5. Our detection probability is >50% for companions with 8 M Jup at semi-major axes of 80-200 au and >13 M Jup at 30-250 au. It thus compares well to the detection space of other state-of-the-art high-contrast imaging surveys. We have already contributed to the characterisation of two new planets originally discovered by VLT/SPHERE, but we have not yet independently discovered new planets around any of our target stars. We have discovered two new close-in low-mass stellar companions around R CrA and HD 193571 and report in this paper the discovery of close co-moving low-mass stellar companions around HD 72660 and HD 92536. Furthermore, we report L -band scattered light images of the discs around eleven stars, six of which have never been imaged at L -band before. Conclusions. The first 2.5 yr of the NACO-ISPY survey have already demonstrated that VLT/NACO combined with our survey strategy can achieve the anticipated sensitivity to detect giant planets and reveal new close stellar companions around our target stars.

Discovery of an Edge-on Circumstellar Debris Disk around BD+45° 598: A Newly Identified Member of the β Pictoris Moving Group

“…Surveys carried out by space-based observatories such as Spitzer, Herschel, and WISE have uncovered hundreds of stars within ∼200 pc with a significant infrared excess in their spectral energy distributions at 22-24μm suggesting the presence of warm circumstellar dust (e.g., Trilling et al 2008;Carpenter et al 2009;Cotten & Song 2016;Patel et al 2017;Silverberg et al 2018), or a colder component identified by an excess at 70-160 μm (e.g., Hillenbrand et al 2008;Matthews et al 2010;Eiroa et al 2013;Sibthorpe et al 2018). The identification of these circumstellar disks has also coincided with several high-contrast imaging surveys targeting stars with an infrared excess (e.g., Janson et al 2013;Rameau et al 2013;Nielsen et al 2019;Launhardt et al 2020). Scattered-light images of debris disk systems in the optical or near-infrared (2 μm) returned by these surveys (e.g., Esposito et al 2020) are particularly powerful for characterizing planetary systems, as the morphology of stable debris belts may reveal the gravitational influence of giant planets sculpting the dust distribution through resonant interactions (e.g., Wyatt 2003;Chiang et al 2009;Morales et al 2011;Su et al 2013;Matthews et al 2018).…”

Insights into the planetary dynamics of HD 206893 with ALMA

“…Some exoKuiper belt host systems even have companions in the brown dwarf or low stellar mass regime, suggesting that their likely formation through gravitational instability (Boss 1997(Boss , 2003(Boss , 2011Vorobyov 2013) is compatible with the formation of massive Kuiper belt analogues, e.g. HR 2562 (Konopacky et al 2016), HD 193571 (Musso Barcucci et al 2019) HD 92536 (Launhardt et al 2020), andHD 206893 (Milli et al 2017). The latter is the subject of this paper.…”

A faint companion around CrA-9: protoplanet or obscured binary?

“…We combined the different sources of uncertainty in quadrature for each parameter. For NACO, Launhardt et al (2020) reported plate scale and true north measurements of 27.2 ± 0.1 mas/px and 0.57 ± 0.12 • based on all their astrometric measurements between December 2015 and March 2018, respectively. We adopted these values, but conservatively adopted an uncertainty of 0.5 • for the PA of TN, to account for any difference between for the different epochs of observations.…”