J/ApJ/748/93 K-band spectra for 133 nearby M dwarfs (Rojas-Ayala+, 2012) ================================================================================ Metallicity and temperature indicators in M dwarf K-band spectra: testing new and updated calibrations with observations of 133 solar neighborhood M dwarfs. Rojas-Ayala B., Covey K.R., Muirhead P.S., Lloyd J.P. =2012ApJ...748...93R ================================================================================ ADC_Keywords: Abundances ; Effective temperatures ; Spectra, infrared ; Spectral types ; Stars, M-type ; Equivalent widths Keywords: stars: abundances - stars: fundamental parameters - stars: late-type Abstract: We present K-band spectra for 133 nearby (d < 33 pc) M dwarfs, including 18 M dwarfs with reliable metallicity estimates (as inferred from an FGK type companion), 11 M dwarf planet hosts, more than 2/3 of the M dwarfs in the northern 8 pc sample, and several M dwarfs from the LSPM catalog. From these spectra, we measure equivalent widths of the Ca and Na lines, and a spectral index quantifying the absorption due to H_2_O opacity (the H_2_O-K2 index). Using empirical spectral type standards and synthetic models, we calibrate the H_2_O-K2 index as an indicator of an M dwarf's spectral type and effective temperature. We also present a revised relationship that estimates the [Fe/H] and [M/H] metallicities of M dwarfs from their Na I, Ca I, and H_2_O-K2 measurements. Comparisons to model atmosphere provide a qualitative validation of our approach, but also reveal an overall offset between the atomic line strengths predicted by models as compared to actual observations. Our metallicity estimates also reproduce expected correlations with Galactic space motions and H{alpha} emission line strengths, and return statistically identical metallicities for M dwarfs within a common multiple system. Finally, we find systematic residuals between our H_2_O-based spectral types and those derived from optical spectral features with previously known sensitivity to stellar metallicity, such as TiO, and identify the CaH1 index as a promising optical index for diagnosing the metallicities of near-solar M dwarfs. Description: Near-infrared spectra of the 133 stars were obtained with the TripleSpec spectrograph on the Palomar 200 inch Hale Telescope during several observing runs between 2007 and 2010. TripleSpec at Palomar has no moving parts and simultaneously acquires 5 cross-dispersed orders covering 1.0-2.4um at a resolution of {lambda}/{Delta}{lambda}~2700. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 77 133 TripleSpec nearby M dwarf sample - source properties table3.dat 83 133 TripleSpec nearby M dwarf Sample - spectral measurements spectra/* . 133 1.88-2.46{mu}m Spectra of the M dwarfs (FITS files) -------------------------------------------------------------------------------- See also: V/70 : Nearby Stars, Preliminary 3rd Version (Gliese+ 1991) I/311 : Hipparcos, the New Reduction (van Leeuwen, 2007) III/198 : Palomar/MSU nearby star spectroscopic survey (Hawley+ 1997) I/238 : Yale Trigonometric Parallaxes, Fourth Edition (van Altena+ 1995) III/114 : Spectra of Late-Type Standards, 2.0-2.5 Microns (Kleinmann+ 1986) J/MNRAS/403/1949 : UBV(RcIc)JHK photometry of HIP nearby stars (Koen+, 2010) J/ApJ/704/975 : Rotational velocities for M dwarfs (Jenkins+, 2009) J/ApJ/701/764 : Light curves for five M-dwarf stars (Fernandez+, 2009) J/A+A/493/645 : Gl 176 radial velocities (Forveille+, 2009) J/PASP/121/117 : Fe & Ti abundances of 12 M stars (Woolf+, 2009) J/AJ/135/785 : SDSS-DR5 low-mass star spectroscopic sample (West+, 2008) J/ApJ/622/1102 : The planet-metallicity correlation. (Fischer+, 2005) J/A+A/415/1153 : [Fe/H] for 98 extra-solar planet-host stars (Santos+, 2004) J/AJ/123/3356 : PMSU nearby star spectroscopic survey. III. (Gizis+, 2002) J/A+A/364/665 : Very low mass stars radial velocities (Segransan+, 2000) J/A+A/331/581 : Rotation and activity in field M dwarfs (Delfosse+ 1998) J/AJ/113/806 : M-Subdwarfs (Gizis 1997) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 12 A12 --- Name Star name 14 A1 --- n_Name [abc] Alternative designation (G1) 16- 19 F4.1 pc Dist [1.8/41.9]? Star's distance 21- 25 F5.2 mag Vmag [7.49/19.74] V-band magnitude 27 I1 --- r_Vmag [1/8] Dist and Vmag reference (1) 29- 34 F6.3 mag Ksmag [3/11] 2MASS Ks-band magnitude 36- 46 A11 "YYYY/MMM/DD" Date Spectrum observation date 48- 51 I4 --- S/N [201/2079] Average signal-to-noise ratio obtained in the K-band continuum 53- 67 A15 --- Comm Star comment 69- 95 A27 --- File FileName of individual spectrum in the "spectra" subdirectory (column added by CDS) -------------------------------------------------------------------------------- Note (1): Reference as follows: 1 = HIPPARCOS, van Leeuwen 2007, Cat. I/311; 2 = YALE, van Altena et al. 2001, Cat. I/238; 3 = PMSU, Reid et al. 1995, Cat. III/198; 4 = Koen et al. 2010, Cat. J/MNRAS/403/1949; 5 = Leggett 1992ApJS...82..351L; 6 = Bessel 1990A&AS...83..357B; 7 = Gould & Chaname 2004, Cat. J/ApJS/150/455; 8 = Gliese & Jahreiss Catalog of Nearby Star, Cat. V/70 -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 12 A12 --- Name Star name 14 A1 --- n_Name [abc] Alternative designation (G1) 16- 20 F5.3 0.1nm EWNaI NaI equivalent width 22- 26 F5.3 0.1nm e_EWNaI EWNaI uncertainty 28- 32 F5.3 0.1nm EWCaI CaI equivalent width 34- 38 F5.3 0.1nm e_EWCaI EWCaI uncertainty 40- 44 F5.3 --- H2O-K2 H_2_O-K2 index (2) 46- 50 F5.3 --- e_H2O-K2 H20-K2 uncertainty 52 I1 --- SpT [0/9] M-spectral subtype 54- 57 I4 K Teff [2492/4031]? Effective temperature 59- 61 I3 K e_Teff [15/106]? Teff uncertainty 63- 67 F5.2 [Sun] [M/H] [-0.45/0.33] Overall metallicity (3) 69- 72 F4.2 [Sun] e_[M/H] [0.12] [M/H] uncertainty 74- 78 F5.2 [Sun] [Fe/H] [-0.64/0.46] [Fe/H] metallicity 80- 83 F4.2 [Sun] e_[Fe/H] [0.17/0.18] [Fe/H] uncertainty -------------------------------------------------------------------------------- Note (2): Covey et al. (2010ApJ...722..971C) adopted the H_2_O-K index to characterize the spectral types of highly reddened young stars from moderate S/N spectra. We developed a modified H_2_O-index using two new regions that do not show any noticeable atomic lines. This H_2_O-K2 water index is defined in equation (5). See section 3.2 for further explanations. Note (3): See section 5.2 for the new K-band overall metallicity ([M/H]) calibration. -------------------------------------------------------------------------------- Global notes: Note (G1): Flag as follows: a = LSPM J0011+5908. b = 2MASS J18353790+3259545. c = Stars with low quality K-band spectra. -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 15-Oct-2013