Very Low Mass Binaries Archive

This page last updated on Tuesday, July 28, 2009. There are currently 99 VLM binaries listed.

This Archive contains an up-to-date list of all the stellar (and sub-stellar) binary systems with total estimated mass < 0.2 M_solar known in the literature. It targets both theorists and observers interested in understanding the empirical data of this subject. In most cases binary parameters are extracted directly from refereed journals referenced in the Table. Additional background information can be found in:

Not Alone: Tracing the Origins of Very-Low-Mass Stars and Brown Dwarfs Through Multiplicity Studies (Burgasser, A. J., Reid, I. N., Siegler, N., Close, L., Allen, P., Lowrance, P., Gizis, J. 2006, chapter in Protostars and Planets V) (Download in postscript, PDF)

Please send suggestions, corrections, and updates to nicholas.siegler at If time, I will link the star names to ADS. If this table has been useful in your research, we suggest an acknowledgment of the form "This publication has made use of the Very-Low-Mass Binaries Archive housed at and maintained by Nick Siegler, Chris Gelino, and Adam Burgasser."

Columns In The Table:

Notes: dash: not measured or not reported; semicolon as suffix: estimated value (eg L:)

  1. "name" : name of the more massive component in the binary
  2. "projected sep (AU)" : projected separation (AU). It is the product of the measured angular separation in arcsec (column 4 / 1000) and distance in parsecs (column 6) unless astrometric constraints known (column 9)
  3. "projected sep error (AU)" : projected separation uncertainty (AU). Uncertainties of the measured angular separation (column 5 / 1000) and distance (column 7) taken in quadrature.
  4. "angular sep (mas)" : angular separation (mas); SB2: double-lined spectroscopic binaries
  5. "angular error (mas)" : angular separation uncertainty (mas); NG: uncertainty not given by authors
  6. "dist (pc)" : distance (pc) (typically photometric or spectra-photometric derived distances, trig parallax if column 8 = Y)
  7. "dist error (pc)" : distance uncertainty (pc)
  8. "plx (Y/N)" : measured trigonometric parallax: Y/N
  9. "sma (Y/N)" : measured semimajor axis: Y/N (a Y may also include a constrained orbital period)
  10. "SpT A" : estimated spectral type component A (Unless spectra was obtained from the resolved binary components, a Y in column 11, component A is estimated from an empirical absolute magnitude relation chosen by the authors; delta magnitude is applied to obtain component B's spectral type. Absolute magnitude of the primary is estimated from A's color. Uncertainties are typically +/- 1.5 SpT.
  11. "SpT B" : estimated spectral type component B
  12. "SpT region (O/I)" : optical (O) or infrared (I) spectral classification; if both are available, optical is reported
  13. "resolv. spectra (Y/N)" : actual spectra obtained of the resolved members: Y/N
  14. "est mass_A (Msun)" : estimate of primary mass (solar masses); taken as the best estimate of the reported mass range. Except for the few cases where dynamical masses are measured or constrained (column 9 = Y), masses are estimated through the use of evolutionary models requiring age and distance estimates. There may be large uncertainties associated with these estimated masses mainly due to the unceratinties of these parameters (reported mass uncertainties are typically < 0.02 solar mass). Mass models are typically insensitive to ages > 1 Gyr.
  15. "est mass_B (Msun)" : estimate of secondary mass (solar masses); taken as the center of the reported mass range with uncertainties typically < 0.02 solar masses.
  16. "q" : mass ratio (mass_B / mass_A)
  17. "P (yr)" : period (yr). Calculated by Kepler's 3rd Law and a statistical scaling of the measured angular separation by 1.26 (Fischer & Marcy 1991) unless period measured or constrained by authors (column 9 = Y).
  18. "age (Myr)" : estimated age (Myr); central of range reported. Field star ages are not quantified here (dash) but can be considered to span the range of solar neighborhood common ages (0.6-7.5 Gyr).
  19. "location" : name of association or cluster, otherwise "field".
  20. "bin. ref." : binary reference
  21. "SpT ref." : spectral type reference of the integrated binary or if column 9 = Y of the resolved binary
  22. "dist. ref." : distance reference
  23. "comments" : comments