USco1621 B and USco1556 B: Two wide companions at the deuterium-burning mass limit in Upper Scorpius

Abstract

(Abridged) Our aim is to identify analogues of gas giant planets, as companions at wide separations of very young stars. To identify these objects, we cross correlated the Visible and Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey (VHS) and the United Kingdom Infrared Telescope Infrared Deep Sky Survey Galactic Clusters Survey (UKIDSS GCS) catalogues to search for common proper motion companions to 1195 already known members of Upper Scorpius (USco; age $\sim$5-10 Myr, distance $\sim$145 pc). We present the discovery and spectroscopic characterisation of two very wide substellar companions of two early-M stars in Upper Scorpius: USco1621 B and USco1556 B. We obtained optical and near-infrared low-resolution spectroscopy of the candidates to characterise their spectral energy distribution and confirm their membership to the association. We also acquired adaptive optics images of the primaries and secondaries to search for signs of binarity and close companions. We determined a spectral type of M8.5 in the optical for both companions, along with L0 and L0.5 in the near-infrared for USco1621 B and USco1556 B, respectively. The spectra of the two companions show evident markers of youth. The comparison with theoretical evolutionary models gives estimated masses of 0.015$\pm$0.002 and 0.014$\pm$0.002 M${}_{\odot }$, with temperatures of 2270$\pm$90 and 2240$\pm$100 K, respectively. The physical separations between the components of both systems are 2880$\pm$20 and 3500$\pm$40 AU for USco1621 and USco1556 systems, respectively. We did not find any additional close companion in the adaptive optics images. The probability that the two secondaries are physically bound to their respective primaries, and not chance alignments of USco members, is 86%, and the probability that none of them are physically related is 1.0%.

17 pages, 15 figures, accepted for publication in A&A

References in corpus (33)

• The Gaia mission
• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• The K2 Mission: Characterization and Early results
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• VOSA: Virtual Observatory SED Analyzer. An application to the Collinder 69 open cluster
• The WFCAM Science Archive
• The UKIRT Wide Field Camera ZYJHK Photometric System: Calibration from 2MASS
• The properties of brown dwarfs and low-mass hydrogen-burning stars formed by disc fragmentation
• Young L Dwarfs Identified in the Field: A Preliminary Low-Gravity, Optical Spectral Sequence from L0 to L5
• Low-Mass Dwarf Template Spectra from the Sloan Digital Sky Survey
• Direct Imaging and Spectroscopy of a Planetary Mass Candidate Companion to a Young Solar Analog
• The Visible and Infrared Survey Telescope for Astronomy (VISTA): Design, Technical Overview and Performance
• Characterizing Young Brown Dwarfs using Low Resolution Near-IR Spectra
• Discovery of a young planetary mass companion to the nearby M dwarf VHS J125601.92-125723.9
• The minimum mass for star formation, and the origin of binary brown dwarfs
• The Wide Brown Dwarf Binary Oph 1622-2405 and Discovery of A Wide, Low Mass Binary in Ophiuchus (Oph 1623-2402): A New Class of Young Evaporating Wide Binaries?
• Discovery of a wide planetary-mass companion to the young M3 star GU Psc
• Near-infrared cross-dispersed spectroscopy of brown dwarf candidates in the Upper Sco association
• A Large-Area Search for Low Mass Objects in Upper Scorpius I: The Photometric Campaign and New Brown Dwarfs
• BOSS Ultracool Dwarfs I: Colors and Magnetic Activity of M and L dwarfs
• CARMENES input catalogue of M dwarfs II. High-resolution imaging with FastCam
• Discovery of a wide companion near the deuterium burning mass limit in the Upper Scorpius association
• New brown dwarfs in Upper Sco using UKIDSS Galactic Cluster Survey science verification data
• Age Determination in Upper Scorpius with Eclipsing Binaries
• Spatial Distributions of Young Stars
• New Pre-main-Sequence Stars in the Upper Scorpius Subgroup of Sco-Cen
• Wide, Cool and Ultracool Companions to Nearby Stars from Pan-STARRS1
• New Evidence for a Substellar Luminosity Problem: Dynamical Mass for the Brown Dwarf Binary Gl 417BC
• The optical+infrared L dwarf spectral sequence of young planetary-mass objects in the Upper Scorpius association
• New members in the Upper Sco association from the UKIDSS Early Data Release
• Age spreads and the temperature dependence of age estimates in Upper Sco
• A new take on the low-mass brown dwarf companions on wide-orbits in Upper-Scorpius
• A low-mass triple system with a wide L/T transition brown dwarf component: NLTT 51469AB/SDSS 2131-0119

Cited by in corpus (5)

• Refining the Census of the Upper Scorpius Association with Gaia
• Host star metallicity of directly imaged wide-orbit planets: implications for planet formation
• Exploring the planetary-mass population in the Upper Scorpius association
• Strong H$\alpha$ emission in the young planetary mass companion 2MASS J0249-0557 c
• Two close binaries across the hydrogen-burning limit in the Praesepe open cluster