J/ApJ/838/73 Brown dwarf surface gravities with Keck/NIRSPEC (Martin , 2017)
Surface gravities for 228 M, L, and T dwarfs in the NIRSPEC Brown Dwarf
Spectroscopic Survey.
Martin E.C., Mace G.N., McLean I.S., Logsdon S.E., Rice E.L.,
Kirkpatrick J.D., Burgasser A.J., McGovern M.R., Prato L.
<Astrophys. J., 838, 73-73 (2017)>
=2017ApJ...838...73M 2017ApJ...838...73M (SIMBAD/NED BibCode)
ADC_Keywords: Spectra, infrared ; Equivalent widths ; Spectral types ;
Stars, ages ; Stars, T-type ; Surveys ; Stars, brown dwarf
Keywords: brown dwarfs; infrared: stars; stars: atmospheres; stars: low-mass;
surveys
Abstract:
We combine 131 new medium-resolution (R∼2000) J-band spectra of M, L,
and T dwarfs from the Keck NIRSPEC Brown Dwarf Spectroscopic Survey
(BDSS) with 97 previously published BDSS spectra to study
surface-gravity-sensitive indices for 228 low-mass stars and brown
dwarfs spanning spectral types M5-T9. Specifically, we use an
established set of spectral indices to determine surface gravity
classifications for all of the M6-L7 objects in our sample by
measuring the equivalent widths (EW) of the K I lines at 1.1692,
1.1778, and 1.2529µm, and the 1.2µm FeHJ absorption index. Our
results are consistent with previous surface gravity measurements,
showing a distinct double peak-at ∼L5 and T5-in K I EW as a function
of spectral type. We analyze the K I EWs of 73 objects of known ages
and find a linear trend between log(Age) and EW. From this
relationship, we assign age ranges to the very low gravity,
intermediate gravity, and field gravity designations for spectral
types M6-L0. Interestingly, the ages probed by these designations
remain broad, change with spectral type, and depend on the
gravity-sensitive index used. Gravity designations are useful
indicators of the possibility of youth, but current data sets cannot
be used to provide a precise age estimate.
Description:
In this paper, we follow up on prior NIR spectroscopy by our group and
use a modified Allers & Liu (A13, 2013ApJ...772...79A 2013ApJ...772...79A) method to
determine surface gravities for 228 M, L, and T dwarfs.
We present medium-resolution (R∼20000) J-band spectra of 85 M dwarfs,
92 L dwarfs, and 51 T dwarfs obtained as part of the Keck NIRSPEC
Brown Dwarf Spectroscopic Survey (BDSS). Ninety-seven spectra were
published previously in McLean+ (2003ApJ...596..561M 2003ApJ...596..561M), Burgasser+
(2003ApJ...592.1186B 2003ApJ...592.1186B), McGovern+ (2004ApJ...600.1020M 2004ApJ...600.1020M), Rice+
(2010ApJS..186...63R 2010ApJS..186...63R), Kirkpatrick+ (2010, J/ApJS/190/100), Luhman
(2012ARA&A..50...65L 2012ARA&A..50...65L), Thompson+ (2013PASP..125..809T 2013PASP..125..809T), Mace+ (2013,
J/ApJS/205/6), Mace+ (2013ApJ...777...36M 2013ApJ...777...36M), and Kirkpatrick+ (2014,
J/ApJ/783/122), and the remaining 131 are presented here for the first
time.
Observation information (spanning 1999 Apr to 2015 Mar) for all of the
targets in our sample is listed in Table 1.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 110 228 Observations and designations
table2.dat 114 228 Equivalent widths and spectral index values for
the Keck NIRSPEC Brown Dwarf Spectroscopic Survey
(BDSS) J-band spectra
table3.dat 145 69 BDSS objects with known ages
refs.dat 81 146 References
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
J/ApJ/476/311 : 2MASS M-dwarf discoveries (Kirkpatrick+ 1997)
J/AJ/120/479 : Low-mass stars in the Upper Sco association (Ardila+, 2000)
J/ApJ/564/421 : Spectra of T dwarfs. I. (Burgasser+, 2002)
J/AJ/123/3409 : SDSS M, L, and T dwarfs (Hawley+, 2002)
J/AJ/124/1190 : Northern high proper motion stars in DSS (Lepine+, 2002)
J/AJ/126/2421 : 2MASS-Selected sample of ultracool dwarfs (Cruz+, 2003)
J/AJ/125/3302 : HST binary very low mass stars and brown dwarfs (Gizis+, 2003)
J/AJ/125/1598 : New high PM stars in the northern sky (Lepine+, 2003)
J/AJ/127/3553 : JHK photom. and spectroscopy for L and T dwarfs (Knapp+, 2004)
J/other/ARA+A/42.685 : Young stars near the Sun (Zuckerman+, 2004)
J/other/ARA+A/43.195 : L and T dwarf stars (Kirkpatrick, 2005)
J/AJ/130/1733 : Optical spectroscopy of ρ Oph stars (Wilking+, 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/ApJ/647/1180 : Infrared photometry of Taurus SFR (Luhman+, 2006)
J/AJ/132/891 : Binaries among nearby L dwarfs (Reid+, 2006)
J/AJ/131/3016 : Low-mass objects in Upper Scorpius (Slesnick+, 2006)
J/AJ/134/1162 : 11 new T dwarfs in 2MASS (Looper+, 2007)
J/ApJS/172/663 : Infrared observations of the Pleiades (Stauffer+, 2007)
J/ApJ/689/1295 : Lithium test implications for BDs (Kirkpatrick+, 2008)
J/ApJ/688/362 : Disks around BDs in σ Ori cluster (Luhman+, 2008)
J/AJ/136/1290 : Ultracool dwarfs from the 2MASS (Reid+, 2008)
J/AJ/137/1 : PMs and astrometry of late-type dwarfs (Faherty+, 2009)
J/ApJ/704/975 : Rotational velocities for M dwarfs (Jenkins+, 2009)
J/ApJ/705/1416 : Volume-limited sample of M7-M9.5 dwarfs <20pc (Reiners+, 2009)
J/ApJS/190/100 : NIR proper motion survey using 2MASS (Kirkpatrick+, 2010)
J/AJ/139/1808 : Colors and kinematics of SDSS L dwarfs (Schmidt+, 2010)
J/ApJS/197/19 : First brown dwarfs discovered by WISE (Kirkpatrick+, 2011)
J/MNRAS/422/1495 : UKIDSS Gal. Clusters Survey Pleiades members (Lodieu+ 2012)
J/MNRAS/426/3403 : UKIDSS-GCS α Per members (Lodieu+, 2012)
J/ApJ/758/31 : IR photometry for members of Upper Sco (Luhman+, 2012)
J/ApJ/744/134 : SONYC new brown dwarfs in ρ Oph (Muzic+, 2012)
J/ApJ/746/154 : Improved kinematic plxes for Sco-Cen members (Pecaut+, 2012)
J/ApJS/205/6 : T dwarf population revealed by WISE (Mace+, 2013)
J/ApJ/762/88 : Young stellar kinematic group candidate members (Malo+, 2013)
J/PASP/125/809 : New nearby M, L, and T dwarfs (Thompson+, 2013)
J/ApJ/783/121 : BANYAN II. Nearby young assoc. cand. members (Gagne+, 2014)
J/ApJ/783/122 : AllWISE motion survey (Kirkpatrick+, 2014)
J/AJ/147/34 : SpeX library of L-type dwarfs (Schneider+, 2014)
J/ApJ/814/118 : L/T transition dwarfs search with PS1 & WISE II. (Best+, 2015)
J/ApJ/798/73 : BANYAN All-Sky Survey (BASS) catalog. V. YMGs (Gagne+, 2015)
J/ApJS/225/10 : Kinematic analysis of M7-L8 dwarfs (Faherty+, 2016)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 25 A25 --- Name Star designation
27- 30 I4 --- Ref [1003/1111] Discovery reference
32- 48 A17 --- AName Abbreviated name
50- 58 A9 --- SpT MK spectral type
60- 63 I4 --- r_SpT [1001/1108] SpT reference
65- 75 A11 --- Date UT date of observation
77-100 A24 --- Calib A0V star calibrator(s) (other spectral type
in parenthesis)
102-105 F4.2 arcsec Slit [0.3/0.8] Slit width
107-110 I4 s Exp [120/6600] Exposure time
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- AName Abbreviated name
19- 27 A9 --- SpT MK spectral type
29- 33 F5.2 0.1nm K1.1692 [-2.2/20.5]? KI 1.1692um equivalent width
in Å units
35- 38 F4.2 0.1nm e_K1.1692 [0.02/5]? K1.1692 uncertainty
40- 44 F5.2 0.1nm K1.1778 [-0.9/18]? KI 1.1778um equivalent width
in Å units
46- 49 F4.2 0.1nm e_K1.1778 [0.02/5.1]? K1.1778 uncertainty
51- 55 F5.2 0.1nm K1.2437 [-2.5/9.3]? KI 1.2437um equivalent width
in Å units
57- 60 F4.2 0.1nm e_K1.2437 ? K1.2437 uncertainty
62- 66 F5.2 0.1nm K1.2529 [-1.2/11.2]? KI 1.2529um equivalent width
in Å units
68- 71 F4.2 0.1nm e_K1.2529 [0.02/2.1]? K1.2529 uncertainty
73- 77 F5.3 --- FeH [0.6/1.5] 1.2µm FeHJ absorption index
79- 83 F5.3 --- e_FeH [0/0.8] FeH uncertainty
85- 95 A11 --- Grav Gravity scores: K1 K2 K4 FeH
(0=high gravity) (1)
97-101 A5 --- Type Gravity type from this paper (G1)
103-114 A12 --- pType Gravity type from A13 (G1)
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Note (1): Gravity scores were computed for the KI EWs at 1.1692um, 1.1778um, and
1.2529um as well as for the FeHJ index. To determine gravity scores
for our sample, we compared our computed EW and FeHJ values to the
cutoffs tabulated in Allers & Liu (A13, 2013ApJ...772...79A 2013ApJ...772...79A). If the
index value was higher than the INT-G cutoff, then it received a score
of "0," indicating field gravity. If the index value was between the
INT-G and VL-G cutoffs, then it received a score of "1" and if the
index value was smaller than the VL-G cutoff, then it received a
value of "2," indicating low surface gravity.
See section 3.3 for further explanations.
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 25 A25 --- Name Star name
27- 41 A15 --- AName Abbreviated name
43- 44 I2 h RAh Hour of right ascension (J2000)
46- 47 I2 min RAm Minute of right ascension (J2000)
49- 54 F6.3 s RAs Second of right ascension (J2000)
56 A1 --- DE- Sign of declination (J2000)
57- 58 I2 deg DEd Degree of declination (J2000)
60- 61 I2 arcmin DEm Arcminute of declination (J2000)
63- 67 F5.2 arcsec DEs Arcsecond of declination (J2000)
69- 77 A9 --- SpT MK spectral type
79 A1 --- l_Age [<*] Limit flag on Age
(*: range 80-300)
81- 85 F5.1 Myr Age [0.3/750]? Age
87- 91 F5.1 Myr e_Age ? Negative uncertainty on Age
93- 97 F5.1 Myr E_Age ? Positive uncertainty on Age
99-103 A5 --- Type Gravity type (G1)
105-129 A25 --- Notes Notes
131-135 F5.1 % Mm [54/100]? Membership probability
136-138 A3 --- f_Mm Amb: ambiguous
140-145 A6 --- r_Mm Membership reference(s) (see refs.dat file)
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Byte-by-byte Description of file: refs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Ref [1/1111] Reference code
6- 24 A19 --- BibCode Bibcode of the reference
26- 51 A26 --- Auth First author's name
52- 81 A30 --- Comm Comment (Catalog's reference)
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Global notes:
Note (G1): Allers & Liu (A13, 2013ApJ...772...79A 2013ApJ...772...79A) define spectral indices and
pseudo-equivalent widths (EWs) of various gravity-sensitive features
in lower-resolution NIR spectra to classify the spectra into three
groups: low (VL-G), intermediate (INT-G), and high (FLD-G) gravity
objects, roughly corresponding to young (≲30Myr),
intermediate (∼30-200Myr), and field-age (≳200Myr) objects.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 30-Oct-2017