J/ApJ/891/171 COCONUTS. I. Spectra of a WD and T4 comoving syst. (Zhang+, 2020)
COol Companions ON Ultrawide orbiTS (COCONUTS).
I. A high-gravity T4 benchmark around an old white dwarf and a re-examination
of the surface-gravity dependence of the L/T transition.
Zhang Z., Liu M.C., Hermes J.J., Magnier E.A., Marley M.S., Tremblay P.-E.,
Tucker M.A., Do A., Payne A.V., Shappee B.J.
<Astrophys. J., 891, 171-171 (2020)>
=2020ApJ...891..171Z 2020ApJ...891..171Z (SIMBAD/NED BibCode)
ADC_Keywords: Spectra, optical; Spectra, infrared; Stars, white dwarf;
Stars, T-type; Stars, double and multiple
Keywords: White dwarf stars; Brown dwarfs; Substellar companion stars
Abstract:
We present the first discovery from the COol Companions ON Ultrawide
orbiTS (COCONUTS) program, a large-scale survey for wide-orbit
planetary and substellar companions. We have discovered a comoving
system COCONUTS-1, composed of a hydrogen-dominated white dwarf
(PSOJ058.9855+45.4184; d=31.5pc) and a T4 companion
(PSOJ058.9869+45.4296) at a 40.6" (1280au) projected separation. We
derive physical properties for COCONUTS-1B from (1) its near-infrared
spectrum using cloudless Sonora atmospheric models, and (2) its
luminosity and the white dwarf's age (7.3-1.6+2.8Gyr) using Sonora
evolutionary models. The two methods give consistent temperatures and
radii, but atmospheric models infer a lower surface gravity and
therefore an unphysically young age. Assuming evolutionary model
parameters (Teff=1255-8+6K, logg=5.44-0.03+0.02dex,
R=0.789-0.005+0.011RJup), we find that cloudless model
atmospheres have brighter Y- and J-band fluxes than the data,
suggesting that condensate clouds have not fully dispersed around
1300K. The W2 flux (4.6µm) of COCONUTS-1B is fainter than models,
suggesting non-equilibrium mixing of CO. To investigate the gravity
dependence of the L/T transition, we compile all 60 known L6-T6
benchmarks and derive a homogeneous set of temperatures, surface
gravities, and masses. As is well known, young, low-gravity late-L
dwarfs have significantly fainter, redder near-infrared photometry and
∼200-300K cooler temperatures than old, high-gravity objects. Our
sample now reveals such gravity dependence becomes weaker for T
dwarfs, with young objects having comparable near-infrared photometry
and ∼100K cooler temperatures compared to old objects. Finally, we
find that young objects have a larger amplitude J-band brightening
than old objects, and also brighten at H band as they cross the L/T
transition.
Description:
We obtained an optical spectrum of the white dwarf primary COCONUTS-1A
using the SuperNova Integral Field Spectrograph (SNIFS) mounted on the
University of Hawaii (UH) 2.2m telescope on Maunakea.
SNIFS provides a moderate spectral resolution of R∼1200 for a
simultaneous coverage from 3300 to 9700Å. Our observations were
conducted on two consecutive nights (2018 December 11-12 UT), with
total exposure times of 2700s and 1800s, respectively.
We also obtained a near-infrared spectrum of COCONUTS-1A using the
NASA Infrared Telescope Facility (IRTF) on 2018 October 23 UT. We used
the facility spectrograph SpeX (R∼50-160) and the wavelength coverage
of 0.7-2.52um and took 10 exposures with 60s each.
See Section 3.1.
The companion COCONUTS-1B was observed using IRTF/SpeX in prism mode
on 2018 October 22 (UT). See Section 3.2.
Objects:
-----------------------------------------------------------------
RA (ICRS) DE Designation(s)
-----------------------------------------------------------------
03 55 56.50 +45 25 10.3 COCONUTS-1A = PSO J058.9855+45.4184
03 55 56.87 +45 25 46.8 COCONUTS-1B = PSO J058.9869+45.4296
-----------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
fig4.dat 66 2880 UH/SNIFS & IRTF/SpeX spectra of COCONUTS-1A
fig6.dat 65 809 IRTF/SpeX 0.8 Prism spectra of COCONUTS-1B
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See also:
B/mk : Catalogue of Stellar Spectral Classifications (Skiff, 2009-)
III/42 : Selected MK Spectral Types (Jaschek, 1978)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/343 : VIKING catalogue data release 2 (Edge+, 2016)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
II/364 : VIRAC. The VVV Infrared Astrometric Catalogue (Smith+, 2019)
II/367 : The VISTA Hemisphere Survey (VHS) catalog DR5 (McMahon+, 2020)
J/ApJS/99/135 : A-type stars rotation and spectral peculiarities (Abt+ 1995)
J/ApJ/564/421 : Spectra of T dwarfs. I. (Burgasser+, 2002)
J/AJ/125/3302 : HST binary very low mass stars and brown dwarfs (Gizis+, 2003)
J/AJ/126/2048 : NStars project: the Northern Sample. I. (Gray+, 2003)
J/AJ/127/3553 : JHK photometry & spectroscopy for L & T dwarfs (Knapp+, 2004)
J/ApJS/156/47 : DA white dwarfs from the Palomar Green Survey (Liebert+, 2005)
J/ApJS/159/141 : Spectroscopic properties of cool stars. I. (Valenti+, 2005)
J/other/ARA+A/43.195 : L and T dwarf stars (Kirkpatrick, 2005)
J/ApJ/637/1067 : Near-IR spectral classification of T dwarfs (Burgasser+, 2006)
J/AJ/131/2722 : New L and T dwarfs from the SDSS (Chiu+, 2006)
J/AJ/132/161 : NStars project: The southern sample. I. (Gray+, 2006)
J/AJ/132/891 : Binaries among nearby L dwarfs (Reid+, 2006)
J/ApJS/167/40 : SDSS4 confirmed white dwarfs catalog (Eisenstein+, 2006)
J/A+A/460/695 : Search for Associations Containing Young stars (Torres+, 2006)
J/AJ/133/439 : Luminosity function of M7-L8 ultracool dwarfs (Cruz+, 2007)
J/AJ/134/1162 : 11 new T dwarfs in 2MASS (Looper+, 2007)
J/A+A/481/661 : Hyades brown dwarfs and very low mass stars (Bouvier+, 2008)
J/AJ/136/1290 : Ultracool dwarfs from the 2MASS (Reid+, 2008)
J/ApJ/689/1295 : Lithium test implications for BDs (Kirkpatrick+, 2008)
J/ApJS/180/117 : MK classifications of spectroscopic binaries (Abt, 2009)
J/ApJ/699/649 : Young M dwarfs within 25pc. I. (Shkolnik+, 2009)
J/ApJ/710/1142 : SpeX spectroscopy of low mass binaries. I. (Burgasser+, 2010)
J/MNRAS/403/1949 : UBV(RcIc)JHK photometry of HIP nearby stars (Koen+, 2010)
J/A+A/522/A112 : i'z' photometry of L5 & later dwarf candidates (Reyle+, 2010)
J/ApJ/730/128 : Spectroscopy of DA WD from the SDSS-DR4 (Tremblay+, 2011)
J/A+A/530/A138 : Geneva-Copenhagen survey re-analysis (Casagrande+, 2011)
J/A+A/535/A54 : HARPS search for extra-solar planets. XXIX (Segransan+, 2011)
J/ApJ/752/56 : BDKP. III. Parallaxes for 70 ultracool dwarfs (Faherty+, 2012)
J/ApJ/754/44 : The AstraLux Large M-dwarf Survey (Janson+ 2012)
J/ApJS/201/19 : Hawaii Infrared Parallax Program. I. (Dupuy+, 2012)
J/MNRAS/430/1171 : Sub-stellar birth rate from UKIDSS (Day-Jones+, 2013)
J/MNRAS/433/457 : 76 T dwarfs from the UKIDSS LAS (Burningham+, 2013)
J/A+A/569/A120 : Spectra of wide companions to planet-host stars (Lodieu+ 2014)
J/ApJ/792/119 : Companions to nearby stars from Pan-STARRS 1 (Deacon+, 2014)
J/ApJ/794/125 : IN-SYNC. I. APOGEE stellar parameters (Cottaar+, 2014)
J/ApJ/794/159 : Statistical analysis of exoplanet surveys (Brandt+, 2014)
J/ApJS/214/17 : Orbital monitoring of AstraLux binaries (Janson+, 2014)
J/A+A/577/A128 : CARMENES input catalog of M dwarfs. I (Alonso-Floriano+, 2015)
J/MNRAS/449/3651 : L and T dwarfs from UKIDSS LAS (Marocco+, 2015)
J/ApJ/810/158 : M,L,T dwarfs fundamental param. and SEDs (Filippazzo+, 2015)
J/MNRAS/454/593 : Young moving groups in solar neighbourhood (Bell+, 2015)
J/ApJ/814/118 : L/T dwarfs search with PS1 & WISE. II. (Best+, 2015)
J/A+A/589/A21 : K-H2 line shapes for cool BDs spectra (Allard+, 2016)
J/ApJS/225/10 : Kinematic analysis of M7-L8 dwarfs (Faherty+, 2016)
J/ApJ/833/96 : Hawaii infrared plx program. II. Ultracool dwarfs (Liu+, 2016)
J/ApJS/231/15 : Astrometric monitoring of ultracool dwarf bin. (Dupuy+, 2017)
J/ApJ/848/11 : Spectroscopic and photometric analysis of WDs (Bedard+, 2017)
J/ApJS/234/1 : Cat. of M, L, & T dwarfs from PS1 3π Survey (Best+, 2018)
J/AJ/156/18 : APOGEE binary comp. of evolved stars (Price-Whelan+, 2018)
J/MNRAS/482/4570 : Gaia DR2 white dwarf candidates (Gentile Fusillo+, 2019)
J/ApJ/878/63 : Cool WD atm. models. IV. Spectral evolution (Blouin+, 2019)
J/AJ/158/13 : The first 300 stars observed by the GPIES (Nielsen+, 2019)
Byte-by-byte Description of file: fig4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 I1 --- Sp Spectrum (1)
3- 19 F17.11 0.1nm lambda [3298.6/25414.2] Wavelength in Angstroms (2)
21- 43 E23.11 cW/m2/nm Flux [-2.74e-16/4.9e-16] Flux
in erg/cm2/s/Å units
45- 66 E22.11 cW/m2/nm e_Flux [1.96e-18/2.67e-16] Uncertainty in Flux
--------------------------------------------------------------------------------
Note (1): Spectrum code as follows:
1 = UH88/SNIFS (2070 occurrences);
2 = SpeX/0.8prism (810 occurrences).
Note (2): The wavelength of the IRTF/SpeX spectrum is converted from vacuum to
air based on Ciddor (1996ApOpt..35.1566C 1996ApOpt..35.1566C) to match the wavelength of the
SNIFS spectrum.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: fig6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 F18.16 um lambda [0.68/2.54] Wavelength, Vacuum
20- 42 E23.16 cW/m2/nm Flux [-2.86e-17/8.5e-17] Flux
in erg/cm2/s/Å units
44- 65 E22.16 cW/m2/nm e_Flux [9e-19/4.91e-17] Uncertainty in Flux
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 10-Aug-2021