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NEWMDWARFS - New M Dwarfs in the Solar Neighborhood

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Overview

This table contains the results from a spectroscopic study of 1080 nearby active M dwarfs, selected by correlating the Two Micron All Sky Survey (2MASS) and ROSAT catalogs at galactic latitudes greater than 15 degrees above or below the Galactic Plane and using a matching radius of 20 arcseconds, as well as color cuts (J-H < 0.75, H-K > 0.15 and 0.8 < J-K < 1.1) designed to select M dwarfs. The authors have derived the spectral types and estimated distances for all of their stars. The spectral types range between K5 and M6. Nearly half of the stars lie within 50 pc. The authors have measured the equivalent width of the H-alpha emission line. Their targets show an increase in chromospheric activity from early to mid-spectral types, with a peak in activity around M5. Using the count rate and hardness ratios obtained from the ROSAT catalog,the authors have derived the stellar X-ray luminosities. Their stars display a "saturation-type" relation between the chromospheric and coronal activity. The relation is such that log L_X/L_bol remains "saturated" at a value of approximately -3 for varying H-alpha equivalent width. The authors have found 568 matches in the USNO-B catalog and have derived the tangential velocities v_tan for these stars. There is a slight trend of decreasing chromospheric activity with age, such that the stars with higher v_tan values have lower H-alpha equivalent widths. The coronal emission, however, remains saturated at a value of log L_X/L_bol ~ -3 for varying tangential velocities, suggesting that the coronal activity remains saturated with age. The authors do not find any break in the saturation-type relation at the spectral type at which stars become fully convective (~M3.5). Most of the stars in their sample show more coronal emission than the dMe stars in the Hyades and Praesepe clusters and have v_tan < 40 km s-1, suggesting that they belong to a young population.

Catalog Bibcode

2006AJ....132..866R

References

Identification of new M Dwarfs in the Solar Neighborhood
    Riaz B., Gizis J.E., Harvin, J.
   <Astronomical J., 132, 866 (2006)>
   =2006AJ....132..866R

Provenance

This table was created by the HEASARC in March 2010 based on the (corrected) electronic version of Table 1 from the reference paper which was obtained from the Astronomical Journal web site.

Parameters

Name
The 2MASS near-infrared source identification in the standard format.

RA
The Right Ascension of the near-infrared source in the selcted equinox. This was constructed by the HEASARC based on the 2MASS name, and thus was based on the J2000 position given to a precision of 0.01 seconds of time.

Dec
The Declination of the near-infrared source in the selcted equinox. This was constructed by the HEASARC based on the 2MASS name, and thus was based on the J2000 position given to a precision of 0.1 arcseconds.

LII
The Galactic Longitude of the near-infrared source.

BII
The Galactic Latitude of the near-infrared source.

Cah1_Index
The value of the CaH1 index as defined in Reid et al. (1995, AJ, 110, 1838).

Cah2_Index
The value of the CaH2 index as defined in Reid et al. (1995, AJ, 110, 1838).

Cah3_Index
The value of the CaH3 index as defined in Reid et al. (1995, AJ, 110, 1838).

Tio5_Index
The value of the TiO5 index as defined in Reid et al. (1995, AJ, 110, 1838).

Jmag
The 2MASS J-band magnitude of the near-infrared source.

Hmag
The 2MASS H-band magnitude of the near-infrared source.

Kmag
The 2MASS K-band magnitude of the near-infrared source.

Spect_Type
The spectral type ST of the near-infrared source derived from equation (1) of the reference paper, viz., ST = -10.775*TiO5 + 8.2. Notice that the authors believe that all the stars in this sample are dwarf stars, i.e., have a luminosity class of V.

Halpha_EW
The H-alpha equivalent width, in Angstroms, where positive values signify emission and negative values signify absorption.

Log_Lx_Lbol
The logarithm of the ratio of the X-ray (ROSAT) and bolometric luminosities for the source, where the X-ray flux is calculated according to equations (5) and (6) of the reference paper and the bolometric magnitude is calculated from the K-band magnitude according to equation (4) of the reference paper.

Tangential_Velocity
The tangential velocity of the star, derived from the USNO-B Catalog when an optical counterpart was found, in km/s.

Distance
The distance to the star, in pc, derived as discussed in Section 5.2 of the reference paper.

Parallax_Distance
The distance to the star, in pc, derived from the trigonometric parallax (available for 44 stars in the sample).

Alt_Name
An alternative source designation, if available

Class
The HEASARC Browse object classification, based on the value of the spect_type parameter and an assumed dwarf star classification.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 25-Mar-2010