The B-Star Exoplanet Abundance Study: a co-moving 16–25 M_Jup companion to the young binary system HIP 79098

Abstract

Wide low-mass substellar companions are known to be very rare among low-mass stars, but appear to become increasingly common with increasing stellar mass. However, B-type stars, which are the most massive stars within ∼150 pc of the Sun, have not yet been examined to the same extent as AFGKM-type stars in that regard. In order to address this issue, we launched the ongoing B-star Exoplanet Abundance Study (BEAST) to examine the frequency and properties of planets, brown dwarfs, and disks around B-type stars in the Scorpius-Centaurus (Sco-Cen) association; we also analyzed archival data of B-type stars in Sco-Cen. During this process, we identified a candidate substellar companion to the B9-type spectroscopic binary HIP 79098 AB, which we refer to as HIP 79098 (AB)b. The candidate had been previously reported in the literature, but was classified as a background contaminant on the basis of its peculiar colors.Here we demonstrate that the colors of HIP 79098 (AB)b are consistent with several recently discovered young and low-mass brown dwarfs, including other companions to stars in Sco-Cen. Furthermore, we show unambiguous common proper motion over a 15-year baseline, robustly identifying HIP 79098 (AB)b as a bona fide substellar circumbinary companion at a 345±6 AU projected separation to the B9-type stellar pair. With a model-dependent mass of 16-25 MJup yielding a mass ratio of <1%, HIP 79098 (AB)b joins a growing number of substellar companions with planet-like mass ratios around massive stars. Our observations underline the importance of common proper motion analysis in the identification of physical companionship, and imply that additional companions could potentially remain hidden in the archives of purely photometric surveys. ⋆ Based on archival observations from the European Southern Observatory, Chile (Programs 073.D-0534 and 095.C-0755).

Search for (sub)stellar Companions of Exoplanet Hosts by Exploring the Second ESA-Gaia Data Release

“…l This companion was revealed spectro-photometrically by Aller et al (2013). With Gaia DR2 astrometry we prove here its companionship with the exoplanet host star HIP 77900 A. m HIP 79098 C was reported by (Janson et al, 2019) as equidistant and co-moving companion of the exoplanet host star HIP 79098 A, based on its Gaia DR2 astrometry, confirmed by the analysis of the companion, which is presented here. n This companion was revealed spectro-photometrically by Aller et al (2013).…”

“…The star exhibits a wide stellar companion, whose WDS designation (GQ Lup C) is used here. HIP 79098 A is a spectroscopic binary and hosts the brown dwarf HIP 79098 B (Janson et al, 2019), which is listed as exoplanet in the EPE. ROXs 12 A is the host star of the brown dwarf ROXs 12 B, detected by Kraus et al (2014), which is listed as exoplanet in the EPE.…”

Discovery of a directly imaged planet to the young solar analog YSES 2

“…Despite several remarkable exoplanet and brown dwarf discoveries by high-contrast imaging at high angular resolution in the Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programs 099.C-0698(A), 0101.C-0153(A), 0101.C-0341(A), and 106.20X2.001. past few years (e.g., Marois et al 2008;Schmidt et al 2008;Marois et al 2010;Lagrange et al 2010;Rameau et al 2013;Bailey et al 2014;Macintosh et al 2015;Chauvin et al 2017;Keppler et al 2018;Haffert et al 2019;Janson et al 2019;Bohn et al 2020a,b), there is an ongoing debate regarding the formation mechanisms that create these super-Jovian gas giants with semimajor axes greater than 10 au. It is unclear whether these companions have a star-like origin from a collapsing molecu- lar cloud that is broken up into fragments, creating planetarymass objects similar to a stellar binary (Kroupa 2001;Chabrier 2003), or through formation in a circumstellar disk instead.…”

Two Directly Imaged, Wide-orbit Giant Planets around the Young, Solar Analog TYC 8998-760-1*

“…Even though several sub-stellar companions have been identified and characterized with these instruments (e.g. Macintosh et al 2015;Galicher et al 2014;Chauvin et al 2017a;Keppler et al 2018;Müller et al 2018;Janson et al 2019;Mesa et al 2019), only two systems have been detected so far that show unambiguous evidence for the presence of more than one directly imaged companion: one of these multi-planet systems is HR 8799 -an approximately 30 Myr-old star of spectral class A5 that is harboring four giant planets at orbits with semi-major axes ranging from 15 au to 70 au (Marois et al 2008(Marois et al , 2010Wang et al 2018). The other one is PDS 70, which is a K7-type star at an age of approximately 5.4 Myr that is hosting at least two accreting protoplanets inside the gap of a transitional disk that is surrounding this pre-main sequence star (Keppler et al 2018;Müller et al 2018;Haffert et al 2019).…”