Confirming new white dwarf-ultracool dwarf binary candidates

Abstract

We present the results of a study to discover prospective new white dwarf-L dwarf binaries as identified by their near-infrared excesses in the UKIDSS catalogue. We obtained optical spectra to validate the white dwarf nature for 22 of the candidate primary stars, confirming ten as white dwarfs and determining their effective temperatures and gravities. For all ten white dwarfs we determined that the near-infrared excess was indeed indicative of a cool companion. Six of these are suggestive of late M dwarf companions, and three are candidate L dwarf companions, with one straddling the M$-$L boundary. We also present near-infrared spectra of eight additional candidate white dwarf-ultracool dwarf binaries where the white dwarf primary had been previously confirmed. These spectra indicate one candidate at the M$-$L boundary, three potential L dwarf companions, and one suspected M dwarf, which showed photometric variability on a $\sim$6 hour period, suggesting the system may be close. Radial velocity follow up is required to confirm whether these systems are close, or widely separated.

Accepted to MNRAS

References in corpus (58)

• The Seventh Data Release of the Sloan Digital Sky Survey
• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• Astrophysics Source Code Library
• The Infrared Telescope Facility (IRTF) Spectral Library: Cool Stars
• The Hawaii Infrared Parallax Program. I. Ultracool Binaries and the L/T Transition
• The Formation Rate, Mass and Luminosity Functions of DA White Dwarfs from the Palomar Green Survey
• An Improved Spectroscopic Analysis of DA White Dwarfs from the Sloan Digital Sky Survey Data Release 4
• A Catalog of Spectroscopically Confirmed White Dwarfs from the Sloan Digital Sky Survey Data Release 4
• A $Gaia$ Data Release 2 catalogue of white dwarfs and a comparison with SDSS
• SDSS DR7 White Dwarf Catalog
• How Dry is the Brown Dwarf Desert?: Quantifying the Relative Number of Planets, Brown Dwarfs and Stellar Companions around Nearby Sun-like Stars
• Spectroscopic Analysis of DA White Dwarfs: Stark Broadening of Hydrogen Lines Including Non-Ideal Effects
• The 2MASS Wide-Field T Dwarf Search. III. Seven New T Dwarfs and Other Cool Dwarf Discoveries
• Low-Mass Dwarf Template Spectra from the Sloan Digital Sky Survey
• New white dwarf and subdwarf stars in the Sloan Digital Sky Survey Data Release 12
• New white dwarf stars in the Sloan Digital Sky Survey Data Release 10
• The Palomar/Keck Adaptive Optics Survey of Young Solar Analogs: Evidence for a Universal Companion Mass Function
• Low Luminosity Companions to White Dwarfs
• Search for brown-dwarf companions of stars
• Strong Brightness Variations Signal Cloudy-to-Clear Transition of Brown Dwarfs
• Subtle Signatures of Multiplicity in Late-type Dwarf Spectra: The Unresolved M8.5 + T5 Binary 2MASS J03202839-0446358
• Survival of a brown dwarf after engulfment by a red giant star
• DA white dwarfs in SDSS DR7 and a search for infrared excess emission
• Hot subdwarfs from the ESO Supernova Ia Progenitor Survey: II. Atmospheric parameters of subdwarf O stars
• Brown Dwarf Photospheres are Patchy: A Hubble Space Telescope Near-infrared Spectroscopic Survey Finds Frequent Low-level Variability
• The chemical diversity of exo-terrestrial planetary debris around white dwarfs
• DB white dwarfs in the Sloan Digital Sky Survey Data Release 10 and 12
• The MUCHFUSS project - Searching for hot subdwarf binaries with massive unseen companions: Survey, target selection and atmospheric parameters
• Fundamental parameter accuracy of DA and DB white dwarfs in Gaia Data Release 2
• Abundance studies of sdB stars using UV echelle HST/STIS spectroscopy
• The EBLM Project IV. Spectroscopic orbits of over 100 eclipsing M dwarfs masquerading as transiting hot-Jupiters
• A Possible Brown Dwarf Companion to the White Dwarf GD1400
• White dwarfs in the UKIDSS Large Area Survey: The Substellar Companion Fraction
• Measuring M dwarf Winds with DAZ White Dwarfs
• A brief introductory guide to TLUSTY and SYNSPEC
• High resolution optical spectroscopy of Praesepe white dwarfs
• The catalogue of radial velocity variable hot subluminous stars from the MUCHFUSS project
• NLTT5306: The shortest Period Detached White Dwarf + Brown Dwarf Binary
• Companions to APOGEE Stars I: A Milky Way-Spanning Catalog of Stellar and Substellar Companion Candidates and their Diverse Hosts
• Solution to the problem of the surface gravity distribution of cool DA white dwarfs from improved 3D model atmospheres
• A Search for Variability in Exoplanet Analogues and Low-Gravity Brown Dwarfs
• Two white dwarfs in ultrashort binaries with detached, eclipsing, likely substellar companions detected by K2
• White dwarf-main sequence binaries from SDSS DR8: unveiling the cool white dwarf population
• Short-Term H-alpha Variability in M Dwarfs
• Two intermediate-mass transiting brown dwarfs from the TESS mission
• Multiwaveband photometry of the irradiated brown dwarf WD0137-349B
• Hot Subdwarf Stars Observed in LAMOST DR1 - Atmospheric parameters from single-lined spectra
• Cool Companions to White Dwarf Stars from the Two Micron All Sky Survey All Sky Data Release
• WD0837+185:the formation and evolution of an extreme mass ratio white dwarf-brown dwarf binary in Praesepe
• The first sub-70 minute non-interacting WD-BD system: EPIC212235321
• The eclipsing post-common envelope binary CSS21055: a white dwarf with a probable brown-dwarf companion
• An eclipsing post common-envelope system consisting of a pulsating hot subdwarf B star and a brown dwarf companion
• Emission lines in the atmosphere of the irradiated brown dwarf WD0137-349B
• J band Variability of M Dwarfs in the WFCAM Transit Survey
• SDSS J000555.90-100213.5: a hot, magnetic carbon-atmosphere WD rotating with a 2.1 day period
• Signs of accretion in the white dwarf + brown dwarf binary NLTT5306
• UV-excess sources with a red/IR-counterpart: low-mass companions, debris disks and QSO selection
• Substellar companions and the formation of hot subdwarf stars

Cited by in corpus (9)

• The population of hot subdwarf stars studied with Gaia -- IV. Catalogues of hot subluminous stars based on Gaia EDR3
• A Catalogue of Potential Post Common Envelope Binaries
• Radial velocity variability and evolution of hot subdwarf stars
• A New Method for Finding Nearby White Dwarf Exoplanets and Detecting Biosignatures
• Four new deeply-eclipsing white dwarfs in ZTF
• Discovery of a resolved white dwarf-brown dwarf binary with a small projected separation: SDSS J222551.65+001637.7AB
• The magnetic system SMSS J1606-1000 as a period bouncer
• Where to find over-massive brown dwarfs: new benchmark systems for binary evolution
• PHL 5038AB: Is the brown dwarf causing pollution of its white dwarf host star?