J/AJ/145/102 Spectroscopy of bright M dwarfs in the northern sky (Lepine+, 2013)
A spectroscopic catalog of the brightest (J<9) M dwarfs in the northern sky.
Lepine S., Hilton E.J., Mann A.W., Wilde M., Rojas-Ayala B., Cruz K.L.,
Gaidos E.
<Astron. J., 145, 102 (2013)>
=2013AJ....145..102L 2013AJ....145..102L
ADC_Keywords: Stars, dwarfs ; Stars, M-type ; Stars, bright ; Spectroscopy ;
Effective temperatures ; Parallaxes, spectroscopic ;
Parallaxes, trigonometric ; Proper motions
Keywords: brown dwarfs - catalogs - stars: fundamental parameters -
stars: late-type - stars: low-mass - surveys
Abstract:
We present a spectroscopic catalog of the 1564 brightest (J<9) M dwarf
candidates in the northern sky, as selected from the SUPERBLINK proper
motion catalog. Observations confirm 1408 of the candidates to be
late-K and M dwarfs with spectral subtypes K7-M6. From the low
(µ>40mas/yr) proper motion limit and high level of completeness of
the SUPERBLINK catalog in that magnitude range, we estimate that our
spectroscopic census most likely includes >90% of all existing,
northern-sky M dwarfs with apparent magnitude J<9. Only 682 stars in
our sample are listed in the Third Catalog of Nearby Stars (CNS3);
most others are relative unknowns and have spectroscopic data
presented here for the first time. Spectral subtypes are assigned
based on spectral index measurements of CaH and TiO molecular bands; a
comparison of spectra from the same stars obtained at different
observatories, however, reveals that spectral band index measurements
are dependent on spectral resolution, spectrophotometric calibration,
and other instrumental factors. As a result, we find that a consistent
classification scheme requires that spectral indices be calibrated and
corrected for each observatory/instrument used. After systematic
corrections and a recalibration of the subtype-index relationships for
the CaH2, CaH3, TiO5, and TiO6 spectral indices, we find that we can
consistently and reliably classify all our stars to a half-subtype
precision. The use of corrected spectral indices further requires us
to recalibrate the ζ parameter, a metallicity indicator based on
the ratio of TiO and CaH optical bandheads. However, we find that our
ζ values are not sensitive enough to diagnose metallicity
variations in dwarfs of subtypes M2 and earlier (±0.5dex accuracy)
and are only marginally useful at later M3-M5 subtypes (±0.2dex
accuracy). Fits of our spectra to the Phoenix atmospheric model grid
are used to estimate effective temperatures. These suggest the
existence of a plateau in the M1-M3 subtype range, in agreement with
model fits of infrared spectra but at odds with photometric
determinations of Teff. Existing geometric parallax measurements are
extracted from the literature for 624 stars, and are used to determine
spectroscopic and photometric distances for all the other stars.
Active dwarfs are identified from measurements of Hα equivalent
widths, and we find a strong correlation between Hα emission in
M dwarfs and detected X-ray emission from ROSAT and/or a large UV
excess in the GALEX point source catalog. We combine proper motion
data and photometric distances to evaluate the (U, V, W) distribution
in velocity space, which is found to correlate tightly with the
velocity distribution of G dwarfs in the solar neighborhood. However,
active stars show a smaller dispersion in their space velocities,
which is consistent with those stars being younger on average. Our
catalog will be most useful to guide the selection of the best M dwarf
targets for exoplanet searches, in particular those using
high-precision radial velocity measurements.
Description:
Targets for the follow-up spectroscopic program were selected from the
catalog of 8889 bright M dwarfs of Lepine & Gaidos (2011, cat.
J/AJ/142/138). All stars are selected from the SUPERBLINK catalog of
stars (Lepine & Shara, 2005, cat. I/298) with proper motions µ>40mas/yr.
Of the 1564 M dwarf candidates, we found that 286 had been observed at
the MDM observatory by one of us (SL) prior to 2008 November, as part
of a separate spectroscopic follow-up survey of very nearby (d<20pc)
stars (Alpert & Lepine, 2011AAS...21724211A 2011AAS...21724211A). The remaining targets
were distributed between our observing teams at the MDM Observatory
and University of Hawaii 2.2m telescope (UH22), with the MDM team in
charge of higher declination targets (δ>30) and the UH22 team in
charge of the lower declination range (0<δ<30).
Spectra were collected at the MDM observatory in a series of 22
observing runs scheduled between 2002 June and 2012 April. Most of the
spectra were collected at the McGraw-Hill 1.3m telescope, but a number
were obtained at the neighboring Hiltner 2.4m telescope. Two different
spectrographs were used: the MkIII spectrograph, and the CCDS
spectrograph. Both are facility instruments which provide low- to
medium-resolution spectroscopy in the optical regime. Their operation
at either 1.3m or 2.4m telescopes is identical. Data were collected in
slit spectroscopy mode, with an effective slit width of 1.0" to 1.5".
The MkIII spectrograph was used with two different gratings: the
300l/mm grating blazed at 8000Å, providing a spectral resolution
R∼2000, and the 600l/mm grating blazed at 5800Å, which provides
R∼4000. The two gratings were used with either one of two thick-chip
CCD cameras (Wilbur and Nellie) both having negligible fringing in the
red. Spectra for a total of 901 bright M dwarf targets were collected
at MDM.
Additional spectra were obtained with the SuperNova Integral Field
Spectrograph (SNIFS) on the University of Hawaii 2.2m telescope on
Mauna Kea between 2009 February and 2012 November. SNIFS has separate
but overlapping blue (3200-5600Å) and red (5200-10000Å)
spectrograph channels, along with an imaging channel, mounted behind a
common shutter. The spectral resolution is ∼1000 in the blue channel,
and ∼1300 in the red channel; the spatial resolution of the
225-lenslet array is 0.4". Spectra for 655 bright M dwarf targets were
collected at UH22 with SNIFS.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 113 1564 Survey stars: positions and photometry
table3.dat 95 1564 Survey Stars: spectroscopic data
table7.dat 84 1564 Survey stars: distances, kinematics, and activity
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See also:
II/312 : GALEX-DR5 (GR5) sources from AIS and MIS (Bianchi+ 2011)
I/298 : LSPM-North Catalog (Lepine+ 2005)
IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)
III/198 : Palomar/MSU nearby star spectroscopic survey (Hawley+ 1997)
I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)
V/70 : Nearby Stars, Preliminary 3rd Version (Gliese+ 1991)
J/AJ/142/138 : All-sky catalog of bright M dwarfs (Lepine+, 2011)
J/AJ/133/439 : Luminosity function of M7-L8 ultracool dwarfs (Cruz+, 2007)
J/AJ/126/2421 : 2MASS-Selected sample of ultracool dwarfs (Cruz+, 2003)
J/AJ/123/2828 : Spectroscopy of northern NLTT stars (Cruz+, 2002)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- --- [PM]
4- 16 A13 --- PM Source name (IHHMMm+DDMMWW) (G1)
18- 30 A13 --- CNS3 Name in Third Catalog of Nearby Stars (CNS3;
Gliese & Jahreiss, 1991, cat. V/70) (1)
32- 41 F10.6 deg RAdeg Right Ascension in decimal degrees (ICRS)
43- 51 F9.6 deg DEdeg Declination in decimal degrees (ICRS)
53- 58 F6.3 arcsec/yr pmRA Proper motion in Right Ascension
60- 65 F6.3 arcsec/yr pmDE Proper motion in Declination
67- 72 F6.4 ct/s Xray ? ROSAT Xray count rate (2)
74- 78 F5.2 --- HR1 ? ROSAT HR1 hardness ratio (2)
80- 84 F5.2 mag FUV ? GALEX/Far-UV magnitude (3)
86- 90 F5.2 mag NUV ? GALEX/Near-UV magnitude (3)
92- 96 F5.2 mag Vmag Estimated visual magnitude (G1)
98 A1 --- n_Vmag [PT] Origin of Vmag (Photographic or Tycho) (4)
100-103 F4.2 mag Jmag 2MASS J magnitude (from cat. II/246)
105-108 F4.2 mag Hmag 2MASS H magnitude (from cat. II/246)
110-113 F4.2 mag Kmag 2MASS Ks magnitude (from cat. II/246)
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Note (1): GJ, Gl, or Wo number.
Note (2): X-ray flux and hardness ratio from the ROSAT all-sky points source
catalog (Voges et al., 1999, cat. IX/10; Voges et al., 2000IAUC.7432....3V 2000IAUC.7432....3V).
Note (3): From the GALEX fifth data release (Bianchi et al., 2011, cat. II/312).
Note (4): Flag as follows:
T = The V magnitude come from the Hipparcos and Tycho-2 catalogs (cat. I/239).
This is generally more reliable with typical errors smaller than ±0.1
magnitude.
P = The V magnitude estimated from POSS-I and/or POSS-II photographic magnitude
as prescribed in Lepine (2005, cat. J/AJ/130/1247). Photographic magnitudes
of relatively bright stars often suffer from large errors at the ∼0.5
magnitude level or more, in part due to photographic saturation.
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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- 2 A2 --- --- [PM]
4- 16 A13 --- PM Source name (IHHMMm+DDMMWW) (G1)
18- 21 A4 --- Obs Observatory where observed (MDM or
UH22=University of Hawaii 2.2m Telescope)
23- 29 F7.2 d Date Epoch of observation (JD-2450000)
31- 35 F5.3 --- CaH2 ? CaH2 spectral index (5)
37- 41 F5.3 --- CaH3 ? CaH3 spectral index (5)
43- 47 F5.3 --- TiO5 ? TiO5 spectral index (5)
49- 54 F6.3 --- VO1 ? VO1 spectral index (5)
56- 60 F5.3 --- TiO6 ? TiO6 spectral index (5)
62- 66 F5.3 --- VO2 ? VO2 spectral index (5)
68- 72 F5.2 --- Mst ? Numerical spectral subtype M (6)
74- 77 A4 --- SpT Adopted MK spectral subtype
79- 83 F5.2 --- zeta ? ζ metallicity index (7)
85- 87 F3.1 [cm/s2] logg ? Gravity from PHOENIX model fits
89- 92 I4 K Teff ? Effective temperature from PHOENIX model fits
94 A1 --- P [P] Previously observed in the PMSU (Palomar-MSU
spectroscopic survey; Reid et al. 1995 and
Hawley et al. 1996, cat. III/198)
95 A1 --- M [M] Previously observed and classified as part
of the Meet the Cool Neighbors (MCN)
spectroscopic program (8)
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Note (5): All spectral indices are corrected for instrumental effects. See
Section 3.2 for additional details.
Note (6): Evaluated from the corrected spectral band indices (not-rounded).
Note (7): Index based on the ratio of TiO and CaH optical bandheads,
introduced by Lepine et al. (2007ApJ...669.1235L 2007ApJ...669.1235L):
ζ=1 for near solar metallicity, ζ=0 for metal-poor subdwarfs.
Note (8): The MCN paper series: Cruz & Reid, 2002,
cat. J/AJ/123/2828; Cruz et al., 2003, cat. J/AJ/126/2421; Cruz et al.,
2007, cat. J/AJ/133/439
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- --- [PM]
4- 16 A13 --- PM Source name (IHHMMm+DDMMWW) (G1)
18- 23 F6.4 arcsec plx1 ? Trigonometric parallax
25- 30 F6.4 arcsec e_plx1 ? Uncertainty in plx1
32- 36 F5.3 arcsec plx2 ? Spectroscopic parallax
38- 42 F5.3 arcsec e_plx2 ? Uncertainty in plx2
44- 48 F5.3 arcsec plx3 ? Photometric parallax
50- 54 F5.3 arcsec e_plx3 ? Uncertainty in plx3
56- 61 F6.1 km/s Uvel ? U component of velocity
63- 68 F6.1 km/s Vvel ? V component of velocity
70- 74 F5.1 km/s Wvel ? W component of velocity
76- 80 F5.2 0.1nm EWHa ? Hα equivalent width index; in Å
82 A1 --- H [Y] Hα activity indicator (Y=Yes) (9)
83 A1 --- X [Y] X-ray activity indicator (Y=Yes) (9)
84 A1 --- U [Y] UV activity indicator (Y=Yes) (9)
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Note (9): The last three columns display flags for stars found to be active
from either Hα, X-ray, or UV flux.
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Global notes:
Note (G1): From the SUPERBLINK catalog (Lepine & Shara, 2005, cat. I/298).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 22-Apr-2014