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BNMDSPECAT - Brightest (J < 9) M Dwarfs in the Northern Sky Spectroscopic Catalog

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Overview

This table contains a spectroscopic catalog of the 1564 brightest (J < 9m) M-dwarf candidates in the northern sky, as selected from the SUPERBLINK proper-motion catalog (Lepine and Shara 2005, AJ, 129, 1483). Observations confirm 1408 of the candidates to be late-K and M dwarfs with spectral subtypes K7 - M6. From the low (mu > 40 mas yr-1) proper motion limit and high level of completeness of the SUPERBLINK catalog in that magnitude range, the authors estimate that their spectroscopic census most likely includes > 90% of all existing, northern-sky M dwarfs with apparent magnitude J < 9m. Only 682 stars in this sample are listed in the Third Catalog of Nearby Stars (CNS3, Gliese and Jahreiss 1991); 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, the authors 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, the authors find that they can consistently and reliably classify all the stars to a half-subtype precision. The use of corrected spectral indices further requires them to recalibrate the zeta parameter, a metallicity indicator based on the ratio of TiO and CaH optical bandheads. However, the authors find that their zeta values are not sensitive enough to diagnose metallicity variations in dwarfs of subtypes M2 and earlier (+/- 0.5 dex accuracy) and are only marginally useful at later M3-M5 subtypes (+/- 0.2 dex accuracy). Fits of their 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 H-alpha equivalent widths, and the authors find a strong correlation between H-alpha emission in M dwarfs and detected X-ray emission from ROSAT and/or a large UV excess in the GALEX point source catalog. Proper motion data and photometric distances are combined in order 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. The authors state that this catalog will be very useful for guiding the selection of the best M dwarf targets for exoplanet searches, in particular those using high-precision radial velocity measurements.

Catalog Bibcode

2013AJ....145..102L

References

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.
  <Astronomical Journal, Volume 145, Issue 4, article id. 102, 29 pp. (2013)>
  =2013AJ....145..102L             (SIMBAD/NED BibCode)

Provenance

This online catalog was created by the HEASARC in June 2013 based on a machine-readable version of Tables 1, 3 and 7 from the paper which were obtained from the AJ website (Tables 1 and 3) or from the first author (Table 7).

prev obs flag

This flag parameter is non-blank to indicates that the star had a previous observation, and is coded as follows:
    P = PMSU survey (Reid et al. 1995, AJ, 110, 1838; Hawley et al. 1996,
          AJ, 112, 2799);
    M = Meet the Cool Neighbors program (Reid et al. 2007, 133, 2825 and
          previous papers).

Parameters

Name
The standard SUPERBLINK catalog name of the star is used as the primary source designation.

CNS3_Name
The source designation of the star if listed in the Third Catalog of Nearby Stars (CNS3, Gliese and Jahreiss 1991) using the widely used GJ, Gl and Wo names.

RA
The Right Ascension of the star in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-6 degrees (0.0036 arcseconds) in the original table.

Dec
The Declination of the star in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-6 degrees (0.0036 arcseconds) in the original table.

LII
The Galactic Longitude of the star.

BII
The Galactic Latitude of the star.

PM_RA
The proper motion of the star in the Right Ascension direction, in arcseconds yr-1.

PM_Dec
The proper motion of the star in the Declination direction, in arcseconds yr-1.

RASS_Count_Rate
The ROSAT All-Sky Survey point source catalogs (RASS: Voges et al. 1999, A&A, 349, 389; 2000, IAUC 7432, 1) X-ray count rate in counts s-1, of the X-ray counterpart.

RASS_Hardness_Ratio_1
The ROSAT All-Sky Survey point source catalogs (RASS: Voges et al. 1999, A&A, 349, 389; 2000, IAUC 7432, 1) X-ray hardness ratio HR1 of the X-ray counterpart.

GALEX_FUV_Mag
The GALEX 5th data release far-UV (FUV) magnitude of the star.

GALEX_NUV_Mag
The GALEX 5th data release near-UV (NUV) magnitude of the star.

Vmag
The optical V-band magnitude of the star taken from the SUPERBLINK proper-motion catalog (Lepine and Shara 2005, AJ, 129, 1483).

Vmag_Flag
This flag parameter indicates the source and, hence expected accuracy of the quoted V-band magnitude of the star. The V magnitudes come from two sources with different levels of accuracy and reliability. For 919 stars in Table 1, generally the brightest ones, the V magnitudes come from the Hipparcos and Tycho-2 catalogs. These are generally more reliable with typical errors smaller than +/- 0.1 magnitudes and are flagged with vmag_flag values of 'T'. The other 645 objects have their V magnitudes estimated from POSS-I and/or POSS-II photographic magnitudes as prescribed in Lepine (2005, AJ, 130, 1247). Photographic magnitudes of relatively bright stars often suffer from large errors at the ~ 0.5 magnitudes level or more, in part due to photographic saturation; those stars are labeled with vmag_flag values of 'P'.

Jmag
The infrared J-band magnitude of the star, taken from the 2MASS Catalog (Cutri et al. 2003).

Hmag
The infrared H-band magnitude of the star, taken from the 2MASS Catalog (Cutri et al. 2003).

Ks_Mag
The infrared KS-band magnitude of the star, taken from the 2MASS Catalog (Cutri et al. 2003).

Observatory
The observatory where the spectrum of the star was collected: 'MDM' for the MDM (Michigan, Dartmouth, MIT) Observatory (894 stars) or 'UH22' for University of Hawaii, 2.2m Telescope. More details of the spectroscopic observations are given in Section 2 of the reference paper.

Spect_Date
The date on which the spectrum of the star was obtained, converted by the HEASARC from the JD units given in the original table.

Cah2_Index
The CaH2 spectral band index, as defined in Table 2 and Section 3.2 of the reference paper, after correction for instrumental effects, as discussed in the same section and using the coefficients given in Table 4 of the reference paper.

Cah3_Index
The CaH3 spectral band index, as defined in Table 2 and Section 3.2 of the reference paper, after correction for instrumental effects, as discussed in the same section and using the coefficients given in Table 4 of the reference paper.

Tio5_Index
The TiO5 spectral band index, as defined in Table 2 and Section 3.2 of the reference paper, after correction for instrumental effects, as discussed in the same section and using the coefficients given in Table 4 of the reference paper.

Vo1_Index
The VO1 spectral band index, as defined in Table 2 and Section 3.2 of the reference paper, after correction for instrumental effects, as discussed in the same section and using the coefficients given in Table 4 of the reference paper.

Tio6_Index
The TiO6 spectral band index, as defined in Table 2 and Section 3.2 of the reference paper, after correction for instrumental effects, as discussed in the same section and using the coefficients given in Table 4 of the reference paper.

Vo2_Index
The VO2 spectral band index, as defined in Table 2 and Section 3.2 of the reference paper, after correction for instrumental effects, as discussed in the same section and using the coefficients given in Table 4 of the reference paper.

Num_Spect_Subtype
The numerical spectral subtype of the star, measured from the average of the band indices and listed to two decimal figures, if the star is of M spectral type, as evaluated from the corrected spectral band indices (not-rounded).See Section 3.2.3 of the reference paper for a complete discussion.

Spect_Type
The adopted spectral type of the star based on the value of the numerical spectral subtype. These values are rounded to the nearest half integer to provide the authors' more formal spectral classifications to a half-subtype precision. Some 170 stars were not found to be good fits to any of the K5, K7, or M type templates, and thus are identified as early-K or G dwarfs and given spectral types of 'G/K' in this table.

Metallicity_Index
The metallicity index, zeta_TiO/CaH_ , of the star, as defined and discussed in Section 6 of the reference paper.

Log_G
The logarithm of the surface gravity of the star, in cgs units, from the best PHOENIX model spectral fit: see Section 5 of the reference paper.

T_Eff
The effective temperature of the star, in degrees K, from the best PHOENIX model spectral fit: see Section 5 of the reference paper

Prev_Obs_Flags
Flags [PM] Indicate Previous Observation: P=PMSU Survey, M=MtCN Program

Trig_Parallax
The trigonometric parallax of the star, in arcseconds.

Trig_Parallax_Error
The uncertainty in the trigonometric parallax, in arcseconds.

Spect_Parallax
The spectroscopic parallax of the star, in arcseconds, calculated assuming the absolute J magnitude has the functional dependence on numerical spectral subtype ST (the num_spect_subtype parameter) given by equation (23) of the reference paper, viz., MJ = 5.680 + 0.393*ST + 0.040*(ST)2. The offset in absolute magnitude between active and non-active stars suggests that spectroscopic and photometric distances would be more accurate for active stars in this census if their estimated absolute magnitudes were made 0.46 mag brighter that suggested by equation (23). Thus, for active stars (defined as stars which qualify as active based on any one of the authors' criteria: H-alpha, UV, X-ray).of subtype M2.5 and earlier, the spectroscopic parallax is calculated assuming MJ = 5.220 + 0.393*ST + 0.040*(ST)2 (equation (25) in the reference paper).

Spect_Parallax_Error
The uncertainty in the spectroscopic parallax, in arcseconds.

Phot_Parallax
The photometric parallax of the star, in arcseconds, calculated assuming the absolute J magnitude has the functional dependence on (V - J) color given by equation (22) of the reference paper, viz., MJ = 1.194 + 1.823*(V - J) -0.079*(V - J)2. The offset in absolute magnitude between active and non-active stars suggests that spectroscopic and photometric distances would be more accurate for active stars in this census if their estimated absolute magnitudes were made 0.46 mag brighter that suggested by equation (22). Thus, for active stars (defined as stars which qualify as active based on any one of the authors' criteria: H-alpha, UV, X-ray).of subtype M2.5 and earlier, the spectroscopic parallax is calculated assuming MJ = 0.734 + 1.823*(V - J) -0.079*(V - J)2 (equation (24) in the reference paper).

Phot_Parallax_Error
The uncertainty in the photometric parallax, in arcseconds

Uvel
The U component of the star's spatial velocity, in km s-1, obtained as discussed in Section 8.2 of the reference paper.

Vvel
The V component of the star's spatial velocity, in km s-1, obtained as discussed in Section 8.2 of the reference paper.

Wvel
The W component of the star's spatial velocity, in km s-1, obtained as discussed in Section 8.2 of the reference paper.

Halpha_EW
The H-alpha equivalent width index EWHA of the star, in Angstroms, as defined in equation (21) of the reference paper. The EWHA index measures the flux in a region (6557.61 A - 6571.61 A), which includes the H-alpha line, in relation to a pseudo-continuum region spanning 6500 A - 6550 A and 6575 A - 6625 A; the calculation provides a value in units of wavelength (A) like the traditional equivalent width. Note that for an H-alpha line in emission, values of the EWHA index are negative, following the usual convention.

Halpha_Activity_Flag
This flag is set to 'Y' if the star is considered to be active based on its H-alpha index, EWHA. Specifically, if EWHA < -0.75 A, which usually corresponds to a clearly detectable H-alpha line in emission.

Xray_Activity_Flag
This flag is set to 'Y' if the star is considered to be active based on its RASS X-ray emission flux, Fx. Specifically, if the ratio of the X-ray flux to the infrared Ks flux, Fx/FKs > -2.6.

UV_Activity_Flag
This flag is set to 'Y' if the star is considered to be active based on its GALEX near-UV emission flux, FNUV. Specifically, if the ratio of the NUV flux to the infrared J flux FNUV/FJ > -4.0.

Class
The HEASARC Browse object classification, based on the value of the spect_type parameter. The stars classed as 'G/K' have been given class values corresponding to G0.


Contact Person

Questions regarding the BNMDSPECAT database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 20-Jun-2013