λ Ophiuchi, Latinized as Lambda Ophiuchi, is a triple star system[3] in the equatorial constellation of Ophiuchus.[10] It has the traditional name Marfik /ˈmɑːrfɪk/,[11] which now applies exclusively to the primary component.[12] The system is visible to the naked eye as a faint point of light with an apparent visual magnitude of 3.82.[2] It is located approximately 173 light-years from the Sun, based on its parallax,[1] but is drifting closer with a radial velocity of –16 km/s.[2]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Ophiuchus |
Right ascension | 16h 30m 54.82314s[1] |
Declination | +01° 59′ 02.1209″[1] |
Apparent magnitude (V) | 3.82[2] 4.18 + 5.22 + 11.0)[3] |
Characteristics | |
Spectral type | A0V + A4V[4] |
U−B color index | +0.01[5] |
B−V color index | +0.022±0.014[2] |
Variable type | Suspected[6] |
Astrometry | |
Radial velocity (Rv) | −16.0±1.5[2] km/s |
Proper motion (μ) | RA: –30.98[1] mas/yr Dec.: –73.42[1] mas/yr |
Parallax (π) | 18.84 ± 0.55 mas[1] |
Distance | 173 ± 5 ly (53 ± 2 pc) |
Absolute magnitude (MV) | 0.20[2] |
Orbit[7] | |
Period (P) | 192 yr |
Semi-major axis (a) | 0.91″ |
Eccentricity (e) | 0.611 |
Inclination (i) | 23.0° |
Longitude of the node (Ω) | 53.3° |
Periastron epoch (T) | B 1939.7 |
Argument of periastron (ω) (secondary) | 157.5° |
Details | |
A | |
Mass | 2.62±0.04[8] M☉ |
Luminosity | 76.0+5.1 −4.8[8] L☉ |
Temperature | 8,831+101 −102[8] K |
Rotational velocity (v sin i) | 138[8] km/s |
B | |
Mass | 1.90[9] M☉ |
C | |
Mass | 0.72[9] M☉ |
Other designations | |
Database references | |
SIMBAD | data |
The inner pair form a binary star[13] system with an orbital period of 192 years and an eccentricity of 0.611.[7] Both components are A-type main-sequence stars, indicating that they are generating energy through core hydrogen fusion. The brighter member of this pair, designated component A, is the primary for the system with a visual magnitude of 4.18[3] and a stellar classification of A0V.[4] The secondary, component B, is magnitude 5.22[3] and class A4V.[4]
Component C is magnitude 11.0 and lies at an angular separation of 119″ from the inner pair.[3] It has a common proper motion and is at approximately the same distance as the other two stars,[14] although any orbit would last for hundreds of thousands of years.[9] It has a mass 72% of the Sun's, a radius 58% of the Sun's, a temperature of about 4,157 K, and 7% of the Sun's luminosity.[14] It has an estimated spectral type of K6.[9]
λ Ophiuchi is the system's Bayer designation. The designations of the three components as Lambda Ophiuchi A, B and C derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[15]
It bore the traditional name Marfik (or Marsik), from the Arabic مرفق marfiq "elbow". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[16] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[17] It approved the name Marfik for the component Lambda Ophiuchi A on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[12]