Introduction to on-line MSC

Last update: April 20, 2010

Data on 1359 stellar systems of multiplicity 3 to 7 are given. All systems are physical and, with little exception, hierarchical. They are represented as several "elementary binaries". For each binary the orbital period and separation are given, as well as component magnitudes, spectral types and estimated masses. Orbital elements are also given when available. The present (April 2010) on-line version of the catalogue is updated as compared to the 1999 (CDS) and the original 1997 publication. The component designation and hierarchy description are changed.

The web interface to MSC contains several elements:

• Navigation panel (blue, upper part). You can examine each system sequentially (PREV/NEXT buttons), search for objects with known catalogue numbers HR, HD, ADS, HIP ( if not found, next largest number will be displayed), browse and select objects from a table (specify the initial WDS code, even incomplete like '13' or '0812', and the number of rows to display), or search by the R.A. and Dec. equatorial coordinates within some radius.
• Main entry (green) gives the WDS(2000) code, equatorial coordinates of the primary (2000), parallax (arcseconds), proper motions in [mas/yr], radial velocity [km/s], cluster flag, mass of the "heaviest" component (solar masses), and the total number of known components N**.
• Cross-identifiers (light yellow) are given as one or several lines with catalogue numbers, visual magnitudes, spectral types and optional names.
• Systems (blue) contain information for each pair: designations of the primary and secondary components (or super-components if composed of several stars), the link to "parent" component that establishes the hierarchy (* for the root or upper-level, t for trapezia systems), type of the system, orbital period and its units (days, years or kiloyears), separation (m = milliarcseconds), magnitudes and spectral types (or B-V color) of individual components, and remark for this system. The last columns contain estimated component masses and their codes , and the position angle.
• Orbital elements (light yellow) are given when available. The system to which the elements refer is indicated as "primary,secondary"
• Notes for some systems.
• Graph showing the structure of hierarchical systems as binary tree. The numbers indicate component's designations, magnitudes, spectral types and masses. Graphs are produced automatically from the links to "parents".

General

Missing numerical values are displayed as zeros!

The periods of wide binaries are estimated from separations, parallaxes and masses, as explained in the paper. Similarly, the separations of close binaries are estimated from their periods. The exact meaning of the "period" and "separation" columns depends uniquely on the type of the system.

System type codes

• c - wide, possibly C.P.M. system
• C - C.P.M. system (sep.>3"); The following small letters give the criteria used: h - hypothetical parallax, r - radial velocities, p - photometric distances, m - proper motions.
• v - close visual or interferometric system (sep.<3")
• V - visual system with computed orbit
• a - astrometric system (perturbed motion suspected)
• A - astrometric orbit for invisible companion is computed
• s - possibly spectroscopic system (var. RV or composite sp.)
• S1, S2 - spectroscopic system with computed orbit, single- or double-lined
• o - occultation binary
• E - eclipsing binary with known period
• e - eclipsing binary, period not known

Mass codes

• * - given in the original publication
• a - estimated from spectral type or B-V color index from Allen tables
• s - sum of masses for the sub-system(s)
• q - estimated from primary mass and mass ratio of SB2
• m - minimum secondary mass for SB1
• v - estimated from magnitude difference of a visual binary
• : - uncertain, magnitude difference assumed to be 2 mag.

The web interface to MSC is new, errors or unexpected behavior are possible. Please, direct bug reports and other comments to A.Tokovinin, atokovinin-AT-ctio.noao.edu

The MSC web interface is programmed by Alex Serbul from the company Qsoft in July 2005: serbul-AT-qsoft.ru