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MDWF10PCUX - UV/X-Ray Data for M Dwarfs Within 10 Parsecs

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Overview

M dwarfs are the most numerous stars in the galaxy. They are characterized by strong magnetic activity. The ensuing high-energy emission is crucial for the evolution of their planets and the eventual presence of life on them. The authors systematically study the X-ray and ultraviolet emission of a subsample of M dwarfs from a recent proper-motion survey, selecting all M dwarfs within 10 pc to obtain a nearly volume-limited sample (~90% completeness). Archival ROSAT, XMM-Newton and GALEX data are combined with published spectroscopic studies of H-alpha emission and rotation to obtain a broad picture of stellar activity on M dwarfs. The authors make use of synthetic model spectra to determine the relative contributions of photospheric and chromospheric emission to the ultraviolet flux. They also analyze the same diagnostics for a comparison sample of young M dwarfs in the TW Hya association (~10 Myr old). The authors find that generally the emission in the GALEX bands is dominated by the chromosphere but the photospheric component is not negligible in early-M field dwarfs. The surface fluxes for the H-alpha, near-ultraviolet, far-ultraviolet and X-ray emission are connected via a power-law dependence. The authors present in the reference paper for the first time such flux-flux relations involving broad-band ultraviolet emission for M dwarfs. Activity indices are defined as the flux ratios between the activity diagnostics and the bolometric flux of the star in analogy to the Ca II R'(HK) index. For a given spectral type, these indices display a spread of 2-3 dex which is largest for M4-type stars. Strikingly, at mid-M spectral types, the spread of rotation rates is also at its highest level. The mean activity index for fast rotators, likely representing the saturation level, decreases from X-rays over the FUV to the NUV band and H-alpha, i.e. the fractional radiation output increases with atmospheric height. The comparison to the ultraviolet and X-ray properties of TW Hya members shows a drop of nearly three orders of magnitude for the luminosity in these bands between ~10 Myr and a few Gyr age. A few young field dwarfs (<1 Gyr) in the 10-pc sample bridge the gap indicating that the drop in magnetic activity with age is a continuous process. The slope of the age decay is steeper for the X-ray than for the UV luminosity. This sample is based on the All-Sky Catalog of bright M dwarfs published by Lepine & Gaidos (2011, AJ, 142, 138, CDS Cat. J/AJ/142/138, available at the HEASARC as the MDWARFASC table). The authors selected all 163 stars from this reference that are within 10pc. Four of these stars that were discovered to be actually late K-type stars were removed from this initial sample, leaving a final sample of 159 stars.

Catalog Bibcodes

2013MNRAS.431.2063S
2014MNRAS.442..343S

References

The UV and X-ray activity of the M dwarfs within 10pc of the Sun.
    Stelzer B., Marino A., Micela G., Lopez-Santiago J., Liefke C.
   <Mon. Not. R. Astron. Soc., 431, 2063-2079 (2013)>
   =2013MNRAS.431.2063S
Erratum: The UV and X-ray activity of the M dwarfs within 10pc of the Sun.
    Stelzer B., Marino A., Micela G., Lopez-Santiago J., Liefke C.
   <Mon. Not. R. Astron. Soc., 442, 343-346 (2014)>
   =2014MNRAS.442..343S

Provenance

This table was created by the HEASARC in July 2017 based upon CDS Catalog J/MNRAS/431/2063 files table1.dat and table2.dat. The positions of the stars were not explicitly given in these tables, but were taken by the HEASARC from the All-Sky Catalog of Bright M Dwarfs published by Lepine & Gaidos (2011, AJ, 142, 138, CDS Cat. J/AJ/142/138, available at the HEASARC as the MDWARFASC table). The version of Table 2 used by the HEASARC is the corrected one given in the Erratum (Stelzer et al. 2014) rather than the version given in the original paper (Stelzer et al. 2013).

Parameters

Name
The name of the star, modified by the HEASARC to conform with the naming conventions discussed in the Dictionary of Nomenclature of Celestial Objects. These names have prefixes of the form "PMI J" (in the original reference table the prefix "PM I" was used) followed by five digits which relate to the International Celestial Reference System (ICRS) right ascension (RA) of the star in sexagesimal coordinates; the first four digits are the hours and minutes of RA, the fifth digit is the seconds of RA divided by 6 and rounded down to the nearest integer. These are followed by the declination sign and then four digits which replicate the ICRS Declination (hours, then minutes) of the source. A disambiguation letter (NSEW) is used when the scheme would leave two stars with the same name, with the letter indicating the relative orientation of the stars in the pair.

Alt_Name
The Gliese (Gl) or Gliese-Jahreiss (GJ) designation of the star taken from the Catalog of Nearby Stars (CNS: available at the HEASARC as the CNS3 table).

RA
The Right Ascension of the star in the selected equinox. This was given in the the All-Sky Catalog of bright M dwarfs published by Lepine & Gaidos (2011, AJ, 142, 138, CDS Cat. J/AJ/142/138, available at the HEASARC as the MDWARFASC table) in decimal degree coordinates (2000.0 epoch) in the ICRS system and to a precision of 10-6 degrees in the original table.

Dec
The Declination of the star in the selected equinox. This was given in the the All-Sky Catalog of bright M dwarfs published by Lepine & Gaidos (2011, AJ, 142, 138, CDS Cat. J/AJ/142/138, available at the HEASARC as the MDWARFASC table) in decimal degree coordinates (2000.0 epoch) in the ICRS system and to a precision of 10-6 degrees in the original table.

LII
The Galactic Longitude of the star.

BII
The Galactic Latitude of the star.

Distance
The heliocentric distance D to the star, in parsecs, calculated from the trigonometric parallax of the star given in Lepine & Gaidos (2011).

Distance_Error
The RMS uncertainty in the heliocentric distance D to the star, in parsecs.

Spect_Type
The spectral type of the star. The authors adopted spectral types from the spectroscopic literature, except for two stars without available spectral types for which they resorted to the values derived from their (V-J) color indexes, as described in Section 2.2 of the reference paper.

T_Eff
The effective temperature of the star Teff, in K, obtained as described in Section 2.2 of the reference paper.

Log_Bol_Flux
The logarithm of the bolometric flux fbol of the star at the distance of the earth, in erg cm-2 s-1. This was obtained from the surface flux Fbol = sigmaB * Teff4, where sigmaB is Boltzmann's constant, by multiplying the latter by the scaling factor (R*/D)2. R* values were derived from Baraffe et al. (1998, A&A, 337, 403) models assuming an age of 5 Gyr for all stars.

V_Sin_I_Limit
This parameter is set to "<" to indicate that the corresponding quoted parameter value is an upper limit.

V_Sin_I
The projected rotational velocity of the star, v sin i, where v is the actual rotational velocity and i is the inclination to the line of sight, in km s-1. The data on the rotational velocities were taken from the spectroscopic catalogs of Reiners et al. (2012, AJ, 143, 93) and Mohanty and Basri (2003, ApJ, 583, 451).

Log_NUV_Flux
The logarithm of the GALEX near-UV (177-283 nm band) flux fNUV of the star at the distance of the earth, in erg cm-2 s-1. See Section 3.2 of the reference paper for more details.

Log_NUV_Flux_Lower
The lower bound of the logarithm of the GALEX near-UV (177-283 nm band) flux fNUV,lo of the star at the distance of the earth, in erg cm-2 s-1.

Log_NUV_Flux_Upper
The upper bound of the logarithm of the GALEX near-UV (177-283 nm band) flux fNUV,up of the star at the distance of the earth, in erg cm-2 s-1

Log_FUV_Flux_Limit
This parameter is set to "<" to indicate that the corresponding quoted parameter value is an upper limit.

Log_FUV_Flux
The logarithm of the GALEX far-UV (134-179 nm band) flux fFUV of the star at the distance of the earth, in erg cm-2 s-1. See Section 3.2 of the reference paper for more details.

Log_FUV_Flux_Lower
The lower bound of the logarithm of the GALEX far-UV (134-179 nm band) flux fFUV,lo of the star at the distance of the earth, in erg cm-2 s-1.

Log_FUV_Flux_Upper
The upper bound of the logarithm of the GALEX far-UV (134-179 nm band) flux fFUV,up of the star at the distance of the earth, in erg cm-2 s-1.

Log_Xray_Flux_Limit
This parameter is set to "<" to indicate that the corresponding quoted parameter value is an upper limit.

Log_Xray_Flux
The logarithm of the archival ROSAT or XMM-Newton X-ray flux (0.2-2.0 keV band) of the star at the distance of the earth, in erg cm-2 s-1. See Section 3.1 of the reference paper for more details.

Log_Xray_Flux_Lower
The lower bound of the logarithm of the archival ROSAT or XMM-Newton X-ray flux (0.2-2.0 keV band) of the star at the distance of the earth, in erg cm-2 s-1.

Log_Xray_Flux_Upper
The upper bound of the logarithm of the archival ROSAT or XMM-Newton X-ray flux (0.2-2.0 keV band) of the star at the distance of the earth, in erg cm-2 s-1.

Class
The HEASARC Browse object classification of the star based upon its quoted spectral type (as given in the spect_type parameter).


Contact Person

Questions regarding the MDWF10PCUX database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 27-Jul-2017