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J/ApJ/842/118   Brown dwarfs with spectral type later than T6   (Leggett+, 2017)

The Y-type brown dwarfs: estimates of mass and age from new astrometry, homogenized photometry, and near-infrared spectroscopy. Leggett S.K., Tremblin P., Esplin T.L., Luhman K.L., Morley C.V. <Astrophys. J., 842, 118-118 (2017)> =2017ApJ...842..118L (SIMBAD/NED BibCode)
ADC_Keywords: Photometry, infrared ; Stars, Y-type ; Spectral types ; Parallaxes, trigonometric ; Stars, brown dwarf ; Stars, T-type Keywords: brown dwarfs; molecular processes; stars: atmospheres Abstract: The survey of the mid-infrared sky by the Wide-field Infrared Survey Explorer (WISE) led to the discovery of extremely cold, low-mass brown dwarfs, classified as Y dwarfs, which extend the T class to lower temperatures. Twenty-four Y dwarfs are known at the time of writing. Here we present improved parallaxes for four of these, determined using Spitzer images. We give new photometry for four late-type T and three Y dwarfs and new spectra of three Y dwarfs, obtained at Gemini Observatory. We also present previously unpublished photometry taken from HST, ESO, Spitzer, and WISE archives of 11 late-type T and 9 Y dwarfs. The near-infrared data are put onto the same photometric system, forming a homogeneous data set for the coolest brown dwarfs. We compare recent models to our photometric and spectroscopic data set. We confirm that nonequilibrium atmospheric chemistry is important for these objects. Nonequilibrium cloud-free models reproduce well the near-infrared spectra and mid-infrared photometry for the warmer Y dwarfs with 425≤Teff(K)≤450. A small amount of cloud cover may improve the model fits in the near-infrared for the Y dwarfs with 325≤Teff(K)≤375. Neither cloudy nor cloud-free models reproduce the near-infrared photometry for the Teff=250K Y dwarf WISEJ085510.83-071442.5 (W0855). We use the mid-infrared region, where most of the flux originates, to constrain our models of W0855. We find that W0855 likely has a mass of 1.5-8 Jupiter masses and an age of 0.3-6Gyr. The Y dwarfs with measured parallaxes are within 20pc of the Sun and have tangential velocities typical of the thin disk. The metallicities and ages we derive for the sample are generally solar-like. We estimate that the known Y dwarfs are 3 to 20 Jupiter-mass objects with ages of 0.6-8.5Gyr. Description: We present the new GNIRS and FLAMINGOS-2 spectra and the new NIRI photometry in section 4 (see also table 1). We obtained a 0.95≤λ(um)≤2.5 spectrum using GNIRS at Gemini North on 2016 December 24 and 25 via program GN-2016B-Q-46 for WISEAJ041022.75+150247.9 with R∼700. We also obtained near-infrared spectra for WISEJ071322.55-291751.9 and WISEAJ114156.67-332635.5 using FLAMINGOS-2 at Gemini South on 2017 February 3 and 7, via program GS-2017A-FT-2. The JH grism was used giving R∼600. We obtained photometry for WISE J085510.83-071442.5 on Gemini North using NIRI at Y and CH4(short) via program GN-2016A-Q-50, and at M' via program GN-2016A-FT-10 between 2015 December and 2016 March. The M' data for a sample of T and Y dwarfs was obtained via program GN-2016B-Q-46 using NIRI on Gemini North. Finally, we obtained H data for the Y1 WISEA J064723.24-623235.4 using FLAMINGOS-2 on Gemini South, which were presented in Leggett+ (2013ApJ...763..130L). We also obtained new photometry from HST/WFC3, ESO VLT HAWK-I and Spitzer/IRAC and WISE archives; see section 5 and tables 2 and 3. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 70 7 New Gemini NIRI photometry table2.dat 147 7 New near-infrared photometry from WFC3 and HAWK-I archives table3.dat 107 14 New mid-infrared photometry from IRAC and WISE archives table7.dat 67 7 New astrometry table8.dat 189 24 Y dwarf data set table15.dat 424 97 Brown dwarfs or brown dwarf systems with spectral types T6 and later refs.dat 69 73 References
See also: V/144 : Near-IR spectroscopy of low-mass binaries and brown dwarfs (Mace, 2014) J/ApJ/564/421 : Spectra of T dwarfs. I. (Burgasser+, 2002) J/AJ/126/2487 : T dwarfs in the southern hemisphere (Burgasser+, 2003) J/AJ/127/3553 : JHK photometry & spectroscopy for L and T dwarfs (Knapp+, 2004) J/A+A/433/185 : Abundance analysis of 102 F and G dwarfs (Bensby+, 2005) J/MNRAS/373/781 : JHK photometry of faint standard stars (Leggett+, 2006) J/AJ/134/2398 : Stellar SEDs in SDSS and 2MASS filters (Covey+, 2007) J/MNRAS/384/1399 : Proper motions of field L and T dwarfs (Jameson+, 2008) J/AJ/137/1 : PMs and astrometry of late-type dwarfs (Faherty+, 2009) J/ApJS/197/19 : First brown dwarfs discovered by WISE (Kirkpatrick+, 2011) J/ApJ/753/156 : T/Y brown dwarfs with WISE photometry (Kirkpatrick+, 2012) J/A+A/562/A71 : Abundances of solar neighbourhood dwarfs (Bensby+, 2014) J/A+A/589/A49 : Photometric brown-dwarf classification (Skrzypek+, 2016) J/ApJ/832/58 : IRAC monitoring of WISE J085510.83-071442.5 (Esplin+, 2016) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 25 A25 --- Name Brown dwarf designation 27 A1 --- l_SpT Limit flag on SpT 28- 31 A4 --- SpT Spectral type 33 A1 --- l_Ymag 3σ limit flag on Ymag 34- 37 F4.1 mag Ymag ? Gemini/NIRI Y magnitude in the MKO Y system 39- 43 F5.2 mag CH4s [23.38]? Gemini/NIRI CH4(short) magnitude 45- 48 F4.2 mag e_CH4s [0.2]? CH4s uncertainty 50- 54 F5.2 mag Hmag [23.11]? Gemini/NIRI H magnitude 56- 59 F4.2 mag e_Hmag [0.27]? Hmag uncertainty 61- 65 F5.2 mag M'mag [12/14]? Gemini/NIRI M' magnitude 67- 70 F4.2 mag e_M'mag [0.06/0.2]? M'mag uncertainty
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 25 A25 --- Name Borwn dwarf designation 27- 30 A4 --- SpT Spectral type 32- 36 F5.2 mag F105W [18/26]? HST/WFC3 F105W magnitude 38- 41 F4.2 mag e_F105W [0.03/0.2]? F105W uncertainty 43- 47 F5.2 mag F125W [17/26]? HST/WFC3 F125W magnitude 49- 52 F4.2 mag e_F125W [0.03/0.3]? F125W uncertainty 54- 58 F5.2 mag F127W [16/25]? HST/WFC3 F127W magnitude 60- 63 F4.2 mag e_F127W [0.02/0.3]? F127W uncertainty 65- 69 F5.2 mag F160W [17/25.5]? HST/WFC3 F160W magnitude 71- 74 F4.2 mag e_F160W [0.03/0.2]? F160W uncertainty 76- 80 F5.2 mag Jmag [18.7/19.7]? VLT/HAWK-I J magnitude (MKO system) 82- 85 F4.2 mag e_Jmag [0.02/0.03]? Jmag uncertainty 87- 91 F5.2 mag Hmag [19.2/20.2]? VLT/HAWK-I H magnitude (MKO system) 93- 96 F4.2 mag e_Hmag [0.02/0.03]? Hmag uncertainty 98-147 A50 --- PID WFC3 and HAWK-I PI and observation identifier
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 25 A25 --- Name Brown dwarf designation 26- 27 A2 --- m_Name Binary indicator 29 A1 --- f_Name [a] Flag on Name (1) 31 A1 --- l_SpT Limit flag on SpT 32- 36 A5 --- SpT Spectral type 38- 42 F5.2 mag [3.6] [14/17.8]? Spitzer/IRAC 3.6um magnitude 44- 47 F4.2 mag e_[3.6] [0.02/0.1]? [3.6] uncertainty 49- 53 F5.2 mag [4.5] [12.5/15.5]? Spitzer/IRAC 4.5um magnitude 55- 58 F4.2 mag e_[4.5] [0.02/0.03]? [4.5] uncertainty 60- 64 F5.2 mag W1mag [17.3/19.1]? WISE W1 (3.4um) band magnitude 66- 69 F4.2 mag e_W1mag [0.2/0.3]? W1mag uncertainty 71- 75 F5.2 mag W3mag [11.9/14]? WISE W3 (12um) band magnitude 77- 80 F4.2 mag e_W3mag [0.1/0.3]? W3mag uncertainty 82-107 A26 --- PID IRAC PI and observation ID
Note (1): a = For 2MASS J00345157+0523050, we also measured [5.8]=13.13±0.03 and [8.0]=12.41±0.03mag.
Byte-by-byte Description of file: table7.dat
Bytes Format Units Label Explanations
1- 25 A25 --- Name Brown dwarf designation 26- 27 A2 --- m_Name Binary indicator 29 A1 --- f_Name Flag on Name (1) 31- 35 F5.3 arcsec Plx [0.05/0.2] Parallax 37- 41 F5.3 arcsec e_Plx [0.005/0.02] Plx uncertainty 43- 48 F6.3 arcsec/yr pmRA [-2.4/0.8] Proper motion along RA 50- 54 F5.3 arcsec/yr e_pmRA [0.004/0.02] pmRA uncertainty 56- 61 F6.3 arcsec/yr pmDE [-1.3/0.3] Proper motion along DEC 63- 67 F5.3 arcsec/yr e_pmDE [0.004/0.01] pmDE uncertainty
Note (1): Flag as follows: a = Astrometric measurements are given in Table 11. b = Parallax from Luhman & Esplin (2016AJ....152...78L). c = Astrometric measurements are given in Table 12. d = Astrometric measurements are given in Table 13. e = Astrometric measurements are given in Table 14.
Byte-by-byte Description of file: table8.dat
Bytes Format Units Label Explanations
1- 25 A25 --- Name Y dwarf designation 26 A1 --- m_Name Binary indicator 28 A1 --- f_Name [abc] Flag on Name (1) 30- 31 A2 --- l_SpT [≥] Limit flag on SpT 32- 36 A5 --- SpT Spectral type 38- 42 F5.2 mag M-m [-1.5/3.3]? Distance modulus 44- 47 F4.2 mag e_M-m [0.04/0.3]? M-m uncertainty 49- 53 F5.2 mag Ymag [19.6/26.6]? MKO system Y-band magnitude 55- 58 F4.2 mag e_Ymag [0.03/0.3]? Ymag uncertainty 60- 64 F5.2 mag Jmag [19.4/25.5] MKO system J-band magnitude 66- 69 F4.2 mag e_Jmag [0.03/0.7] Jmag uncertainty 71- 75 F5.2 mag Hmag [19.9/25.3] MKO system H-band magnitude 77- 80 F4.2 mag e_Hmag [0.04/0.4] Hmag uncertainty 82- 86 F5.2 mag Kmag [19.9/23.5]? MKO system K-band magnitude 88- 91 F4.2 mag e_Kmag [0.06/0.4]? Kmag uncertainty 93- 97 F5.2 mag [3.6] [16/19.3]? Spitzer/IRAC 3.6um band magnitude 99-102 F4.2 mag e_[3.6] [0.02/0.2]? [3.6] uncertainty 104-108 F5.2 mag [4.5] [13.5/16.8]? Spitzer/IRAC 4.5um band magnitude 110-113 F4.2 mag e_[4.5] [0.02/0.05]? [4.5] uncertainty 115-119 F5.2 mag W1mag [16.4/19.1]? WISE W1 (3.4um) magnitude (2) 121-124 F4.2 mag e_W1mag [0.08/0.4]? W1mag uncertainty 126-130 F5.2 mag W2mag [13.5/17]? WISE W2 (4.6um) magnitude (2) 132-135 F4.2 mag e_W2mag [0.04/0.1]? W2mag uncertainty 137-141 F5.2 mag W3mag [11.7/14]? WISE W3 (12um) magnitude (2) 143-146 F4.2 mag e_W3mag [0.2/0.5]? W3mag uncertainty 148-154 A7 --- r_plx Plx reference (see refs.dat file) 156-167 A12 --- r_IRAC IRAC reference (see refs.dat file) 169-180 A12 --- r_YJHK YJHK reference (see refs.dat file) 182-189 A8 --- Ref Discovery reference (see refs.dat file)
Note (1): Flag as follows: a = WISE J014656.66+423410.0B and WISEPC J121756.91+162640.2B are in close binary systems. Mid-infrared photometry is not available for the individual components of the systems. b = We have also measured for WISE J085510.83-071442.5 M'=13.95±0.20mag and for WISEA J205628.88+145953.6 M'=14.00±0.15mag. c = The brown dwarf WISE name is WISEA J163940.84-684739.4 (as in tables 3 and 8) and not, WISE J163940.86-684744.6. Corrected by CDS after confirmation by the author (see the "Acknowledgements" section below); flag added by CDS. Note (2): From AllWISE catalog.
Byte-by-byte Description of file: table15.dat
Bytes Format Units Label Explanations
1- 25 A25 --- Name Star name (1) 26- 27 A2 --- m_Name Binary indicator (2) 29- 32 F4.1 --- SpT [6/12] Spectral type indicator e.g. 6=T6 12=Y2 34- 39 F6.2 mag M-m [-2.4/3.3]?=999 Distance modulus (absolute magnitude - apparent magnitude) 41- 46 F6.2 mag JMag [14.2/28.8]?=999 Absolute MKO J (Vega) magnitude 49- 54 F6.2 mag C2Mag [12/17.2]?=999 Absolute Spitzer/IRAC 4.5um (Vega) magnitude 57- 62 F6.2 mag J-C2 [1.9/11.6]?=999 MKO J - Spitzer/IRAC C2 color 64- 69 F6.2 mag imag [22.5/26]?=99 SDSS i (AB) magnitude 71- 76 F6.2 mag zmag [18/22.8]?=199 SDSS z (AB) magnitude 78- 83 F6.2 mag Ymag [15/26.6]?=299 MKO Y (Vega) magnitude 85- 89 F5.2 mag Jmag [14.2/25.5] MKO J (Vega) magnitude 91- 96 F6.2 mag Hmag [14.6/25.3]?=300 MKO H (Vega) magnitude 98-103 F6.2 mag Kmag [15.2/23.5]?=399 MKO K (Vega) magnitude 105-110 F6.2 mag L'mag [12.3/14]?=499 MKO L' (Vega) magnitude 112-117 F6.2 mag M'mag [11.7/14]?=599 MKO M' (Vega) magnitude 119-124 F6.2 mag C1mag [13/19.3]?=699 Spitzer/IRAC 3.6um (Vega) magnitude 127-132 F6.2 mag C2mag [11.6/16.8]?=799 Spitzer/IRAC 4.5um (Vega) magnitude 135-140 F6.2 mag C3mag [12.3/15.4]?=899 Spitzer/IRAC 5.8um (Vega) magnitude 142-147 F6.2 mag C4mag [11.7/14.6]?=999 Spitzer/IRAC 8.0um (Vega) magnitude 149-155 F7.2 mag W1mag [14/19.1]?=1999 WISE W1 3.35um (Vega) magnitude 158-164 F7.2 mag W2mag [11.6/17]?=2999 WISE W2 4.6um (Vega) magnitude 167-173 F7.2 mag W3mag [10.2/14]?=3999 WISE W3 11.6um (Vega) magnitude 175-178 F4.2 mag e_M-m [0.01/0.3]?=9 Uncertainty in M-m 180-183 F4.2 mag e_imag [0.09/0.7]?=9 Uncertainty in imag 185-188 F4.2 mag e_zmag [0.04/0.3]?=9 Uncertainty in zmag 190-193 F4.2 mag e_Ymag [0.01/0.3]?=9 Uncertainty in Ymag 195-198 F4.2 mag e_Jmag [0.01/0.3] Uncertainty in Jmag 200-203 F4.2 mag e_Hmag [0.01/0.4]?=9 Uncertainty in Hmag 205-208 F4.2 mag e_Kmag [0.02/0.4]?=9 Uncertainty in Kmag 210-213 F4.2 mag e_L'mag [0.04/0.08]?=9 Uncertainty in L'mag 215-218 F4.2 mag e_M'mag [0.06/0.2]?=9 Uncertainty in M'mag 220-223 F4.2 mag e_C1mag [0.02/0.2]?=9 Uncertainty in C1mag 225-228 F4.2 mag e_C2mag [0.01/0.05]?=9 Uncertainty in C2mag 230-233 F4.2 mag e_C3mag [0.03/0.2]?=9 Uncertainty in C3mag 235-238 F4.2 mag e_C4mag [0.03/0.2]?=9 Uncertainty in C4mag 240-243 F4.2 mag e_W1mag [0.03/0.5]?=9 Uncertainty in W1mag 245-249 F5.3 mag e_W2mag [0.02/0.2]?=9 Uncertainty in W2mag 251-254 F4.2 mag e_W3mag [0.07/0.5]?=9 Uncertainty in W3mag 256-286 A31 --- Ref1 Discovery reference (see refs.dat file) 288-306 A19 --- Comp Name if object is known to be part of a multiple system 308-338 A31 --- Ref2 Spectral classification reference (see refs.dat file) 340-361 A22 --- Ref3 Trigonometric parallax reference (see refs.dat file) 363-424 A62 --- Ref4 Photometry reference (see refs.dat file)
Note (1): Survey+position based identifiers are given for all sources and have been verified with Simbad except for WISE J080715.26-661851.6. We give this identifier to object WD 0806-661B to indicate the presence of a faint but measurable source in the WISE images. Note (2): Binary component indicators for systems with blended photometry in one or more bands. The photometry of blended binary systems is given as Binary=AB. Otherwise the photometry is of the individual component.
Byte-by-byte Description of file: refs.dat
Bytes Format Units Label Explanations
1- 4 A4 --- Ref Reference code in table 8 6- 28 A23 --- Ref15 Reference code (First author's name and year) in table 15 30- 48 A19 --- BibCode Bibcode of the reference 50- 69 A20 --- Comm Comment
History: From electronic version of the journal Acknowledgements: Sandy K. Leggett [Gemini Observatory]
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 31-Jan-2018
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