J/AJ/157/63 Radius relations for low-metallicity M-dwarf stars (Kesseli+, 2019)
Radii of 88 M subdwarfs and updated radius relations for low-metallicity
M-dwarf stars.
Kesseli A.Y., Kirkpatrick J.D., Fajardo-Acosta S.B., Penny M.T.,
Gaudi B.S., Veyette M., Boeshaar P.C., Henderson C.B., Cushing M.C.,
Calchi-Novati S., Shvartzvald Y., Muirhead P.S.
<Astron. J., 157, 63 (2019)>
=2019AJ....157...63K 2019AJ....157...63K (SIMBAD/NED BibCode)
ADC_Keywords: Stars, nearby ; Stars, M-type ; Stars, subdwarf ; Stars, dwarfs ;
Photometry, SDSS ; Photometry, ugriz ; Photometry, infrared ;
Effective temperatures ; Stars, diameters ; Abundances, [Fe/H]
Keywords: stars: abundances - stars: fundamental parameters - stars: low-mass -
subdwarfs
Abstract:
M subdwarfs are low-metallicity M dwarfs that typically inhabit the halo
population of the Galaxy. Metallicity controls the opacity of stellar
atmospheres; in metal-poor stars, hydrostatic equilibrium is reached
at a smaller radius, leading to smaller radii for a given effective
temperature. We compile a sample of 88 stars that span spectral classes
K7 to M6 and include stars with metallicity classes from solar-metallicity
dwarf stars to the lowest metallicity ultra subdwarfs to test how
metallicity changes the stellar radius. We fit models to Palomar Double
Spectrograph (DBSP) optical spectra to derive effective temperatures
(Teff) and we measure bolometric luminosities (Lbol) by combining broad
wavelength-coverage photometry with Gaia parallaxes. Radii are then
computed by combining the Teff and Lbol using the Stefan-Boltzman law.
We find that for a given temperature, ultra subdwarfs can be as much as
five times smaller than their solar-metallicity counterparts. We present
color-radius and color-surface brightness relations that extend down to
[Fe/H] of -2.0 dex, in order to aid the radius determination of M subdwarfs,
which will be especially important for the WFIRST exoplanetary microlensing
survey.
Description:
We collected broadband photometry for all of our sources, spanning the
blue end of the optical region to mid-IR wavelengths. Optical photometry
was collected from the Sloan Digital Sky Survey's 12th data release (SDSS;
Alam et al. 2015, Cat. V/147), the Pan-STARRS1 survey (Chambers et al.
2016, Cat. II/349), and from Gaia's Red and Blue Photometers (Gaia
Collaboration et al. 2016, Cat. I/337). All of the near-infrared (NIR)
photometry was from the 2MASS All-Sky Point Source Catalog (2MASS;
Skrutskie et al. 2006, Cat VII/233), with one source supplemented from the
corresponding Reject Table (this source is noted in Table 2). The Wide-field
Infrared Survey Explorer (WISE; Wright et al. 2010AJ....140.1868W 2010AJ....140.1868W) AllWISE
Point Source Catalog served as our source of mid-IR photometry. Both WISE
and 2MASS photometry were downloaded from IRSA
(http://irsa.ipac.caltech.edu/frontpage/).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 289 94 Photometry
table3.dat 79 87 Derived parameters
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
J/PASP/121/117 : Fe and Ti abundances of 12 low-metallicity M stars
(Woolf+, 2009)
J/A+A/564/A90 : M subdwarfs VLT/UVES high resolution spectra
(Rajpurohit+, 2014)
J/MNRAS/443/2561 : CONCH-SHELL catalog of nearby M dwarfs (Gaidos+, 2014)
J/ApJ/804/64 : Empirical and model parameters of 183 M dwarfs
(Mann+, 2015)
J/other/RAA/16.G7 : Nearby M subdwarfs from LAMOST DR2 (Bai+, 2016)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Star Star identifier
16- 22 F7.4 mag umagSD [11.0806/24.4154]? Apparent SDSS u band magnitude
24- 29 F6.4 mag e_umagSD [0.0005/1.1093]? Uncertainty in umagSD
31- 37 F7.4 mag gmagSD [8.6298/21.6095]? Apparent SDSS g band magnitude
39- 44 F6.4 mag e_gmagSD [0.0001/1.086]? Uncertainty in gmagSD
46- 51 F6.3 mag gmagPS [14.255/21.15]? Apparent Pan-STARRS g band
magnitude
53- 60 F8.6 mag e_gmagPS [0.000293/0.034]? Uncertainty in gmagPS
62- 68 F7.4 mag Bmag [7.8828/20.1607]? Apparent Gaia blue band
magnitude
70- 75 F6.4 mag e_Bmag [0.0012/0.0993]? Uncertainty in Bmag
77- 82 F6.3 mag rmagPS [13.861/19.275]? Apparent Pan-STARRS r band
magnitude
84- 91 F8.6 mag e_rmagPS [5.1e-05/0.015]? Uncertainty in rmagPS
93- 99 F7.4 mag rmagSD [7.0918/19.2307]? Apparent SDSS r band magnitude
101-106 F6.4 mag e_rmagSD [0/2.0723]? Uncertainty in rmagSD
108-113 F6.3 mag imagPS [14.531/17.864]? Apparent Pan-STARRS i band
magnitude
115-122 F8.6 mag e_imagPS [0.000976/0.018]? Uncertainty in imagPS
124-130 F7.4 mag imagSD [6.4159/17.8655]? Apparent SDSS i band magnitude
132-137 F6.4 mag e_imagSD [0/7.8301]? Uncertainty in imagSD
139-145 F7.4 mag Rmag [6.0594/17.4027]? Apparent Gaia red band
magnitude
147-152 F6.4 mag e_Rmag [0.0006/0.054]? Uncertainty in Rmag
154-159 F6.3 mag zmagPS [13.534/17.237]? Apparent Pan-STARRS z band
magnitude
161-168 F8.6 mag e_zmagPS [1.7e-05/0.02]? Uncertainty in ymagPS
170-176 F7.4 mag zmagSD [6.7336/17.1567]? Apparent SDSS z band magnitude
178-183 F6.4 mag e_zmagSD [0.0001/1.0869]? Uncertainty in zmagSD
185-190 F6.3 mag ymagPS [12.622/16.964]? Apparent Pan-STARRS y band
magnitude
192-199 F8.6 mag e_ymagPS [9e-06/0.2]? Uncertainty in ymagPS
201-206 F6.3 mag Jmag [5.449/15.827]? Apparent 2MASS J band magnitude
208-212 F5.3 mag e_Jmag [0.018/0.079]? Uncertainty in Jmag
214-219 F6.3 mag Hmag [5.282/15.539]? Apparent 2MASS H band magnitude
221-225 F5.3 mag e_Hmag [0.016/0.117]? Uncertainty in Hmag
227-232 F6.3 mag Ksmag [4.593/15.362]? Apparent 2MASS Ks band
magnitude
234-238 F5.3 mag e_Ksmag [0.014/0.18]? Uncertainty in Ksmag
240-245 F6.3 mag W1mag [4.042/14.997]? Apparent WISE 3.4 micron band
magnitude
247-251 F5.3 mag e_W1mag [0.022/0.282]? Uncertainty in W1mag
253-258 F6.3 mag W2mag [3.318/14.754]? Apparent WISE 4.6 micron band
magnitude
260-264 F5.3 mag e_W2mag [0.016/0.165]? Uncertainty in W2mag
266-271 F6.3 mag W3mag [2.495/13.051]? Apparent WISE 12 micron band
magnitude
273-277 F5.3 mag e_W3mag [0.013/0.406]? Uncertainty in W3mag
279-283 F5.3 mag W4mag [2.519/8.816]? Apparent WISE 22 micron band
magnitude
285-289 F5.3 mag e_W4mag [0.018/0.423]? Uncertainty in W4mag
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Star Star identifier
15- 20 A6 --- SpType Spectral type (1)
22- 25 I4 K Teff [2700/4300] Effective temperature
27- 29 I3 K e_Teff [100] Uncertainty in Teff
31- 36 F6.3 [Lsun] logL [-3.137/-1.044] Bolometric luminosity
(log(Lbol/L☉))
38- 42 F5.3 [Lsun] e_logL [0.001/0.333] Uncertainty in logL
44- 48 F5.3 Rsun Rad [0.104/0.626] Radius
50- 54 F5.3 Rsun e_Rad [0.007/0.165] Uncertainty in Rad
56- 60 F5.2 [-] [Fe/H] [-1.88/0.25] Metallicity
62- 65 F4.2 [-] e_[Fe/H] [0.08/0.3] Uncertainty in [Fe/H]
67- 77 A11 --- Meth Method for determining the metallicity (2)
79 A1 --- r_Meth [abc] Reference for Meth (3)
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Note (1): We restricted our spectral class range to ∼K7 through ∼M7. The
Lepine et al. (2007ApJ...669.1235L 2007ApJ...669.1235L) subdwarf subclasses - subdwarfs (sd),
extreme subdwarfs (esd), and ultra subdwarfs (usd), roughly represent objects
in the metallicity ranges log ([Fe/H])~-0.5, -1.0, and -1.5, respectively.
Most known late-K through late-M subdwarfs were classified before the
Lepine et al. system was established, some of which were typed against the
earlier Gizis (1997, J/AJ/113/806) two-subclass system. Others pre-date both
of these papers and are classified on a mixture of systems.
Note (2): Method as follows:
Lit = Previously measured literature [Fe/H] value;
Phot = Photometrically determined [Fe/H] value;
Spec = Spectroscopic metallicity;
iSHELL_Spec = We used the high-resolution (R∼35000) near-infrared iSHELL
spectra.
Note (3): Reference as follows:
a = Mann et al. (2015, J/ApJ/804/64).
b = Gaidos et al. (2014, J/MNRAS/443/2561).
c = Schmidt et al. (2016MNRAS.460.2611S 2016MNRAS.460.2611S).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 20-May-2019