SW Lyncis
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Lynx |
| Right ascension | 08h 07m 41.569s |
| Declination | +41° 48′ 01.74″ |
| Apparent magnitude (V) | 9.58 primary eclipse: 10.20 secondary eclipse: 9.65 |
| Characteristics | |
| Spectral type | F2 V |
| B−V color index | 0.255±0.041 |
| Variable type | Detached Algol |
| Astrometry | |
| Radial velocity (Rv) | +32.39±1.35 km/s |
| Proper motion (μ) | RA: −16.887 mas/yr Dec.: −36.795 mas/yr |
| Parallax (π) | 3.3655±0.0571 mas |
| Distance | 970 ± 20 ly (297 ± 5 pc) |
| Orbit | |
| Period (P) | 0.644066 d |
| Eccentricity (e) | 0.00 |
| Periastron epoch (T) | 2,451,400.1795±0.0025 HJD |
| Semi-amplitude (K1) (primary) | 116.73±1.65 km/s |
| Semi-amplitude (K2) (secondary) | 222.75±3.20 km/s |
| Details | |
| Primary | |
| Mass | 1.77±0.37 M☉ |
| Radius | 1.76±0.16 R☉ |
| Luminosity | 10.15±0.15 L☉ |
| Temperature | 7,800 K |
| Secondary | |
| Mass | 0.92±0.18 M☉ |
| Radius | 1.32±0.12 R☉ |
| Luminosity | 0.64±0.01 L☉ |
| Temperature | 4,588±6 K |
| Other designations | |
| SW Lyn, BD+42°1811, HD 67008, HIP 39771, SAO 42180 | |
| Database references | |
| SIMBAD | data |
SW Lyncis is a binary or possibly a multiple-star system in the northern constellation of Lynx, abbreviated SW Lyn. With a combined apparent visual magnitude of 9.58, it is too faint to be visible to the naked eye. The system is located at a distance of approximately 970 light years based on parallax measurements, and is drifting further away with a net radial velocity of about +32 km/s.
The variable luminosity of this system was reported by R. Kippenhahn in 1955. Huth in 1958 classified it as a β Lyr-type variable. W. Strohmeier found a short period of 15.46 hours in 1959, although there was no minimum detected from a secondary eclipse. H. Mauder classified this as an eclipsing binary of the Algol type based on a light curve assembled in 1960. J. K. Gleim in 1967 noted that the period of the system had changed, suggesting that there may be a third body in the system. He considered it to be a member of the β Lyr class, although it is more closely related to the Algol type than W Ursae Majoris variables.
M. Vetešník noted in 1968 that the light curve for the system appeared noticeably asymmetric. He published orbital elements for this system in 1977 and found a stellar classification of F2V for the primary component. A low mass ratio suggested the secondary is much smaller and less luminous than the primary. L. Qingyao and associates in 1991 concluded that this is a semi-detached system with one of the components filling its Roche lobe, and thought the secondary to be over-sized and over-luminous for its mass. W. Ogłoza and associates in 1998 supported the idea of a semi-detached system, and found that the light curve suggested the presence of a third component in the system with an orbital period of 5.83 years. The third component is thought to contribute less than 1.5% of the light output of the system.
In 2010, C.-H. Kim and associates performed modelling of the 34-year cycle variations of the system and conjectured that two additional circumbinary companions are creating this effect. However, subsequent studies suggest that such a configuration would be too unstable. The system behavior remains unexplained. SW Lyn is presently classified as a near contact binary that decreases in brightness to magnitude 10.20 during the primary eclipse and to magnitude 9.65 with the secondary eclipse.