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,[3] 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.[5]

SW Lyncis

A visual band light curve for SW Lyncis, adapted from Ogloza et al. (1998)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Lynx
Right ascension	08h 07m 41.569s[2]
Declination	+41° 48′ 01.74″[2]
Apparent magnitude (V)	9.58[3] primary eclipse: 10.20 secondary eclipse: 9.65[4]
Characteristics
Spectral type	F2 V[5]
B−V color index	0.255±0.041[3]
Variable type	Detached Algol[4]
Astrometry
Radial velocity (Rv)	+32.39±1.35[5] km/s
Proper motion (μ)	RA: −16.887 mas/yr[2] Dec.: −36.795 mas/yr[2]
Parallax (π)	3.3655 ± 0.0571 mas[2]
Distance	970 ± 20 ly (297 ± 5 pc)
Orbit[5]
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[6]
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[7]
Database references
SIMBAD	data

The variable luminosity of this system was reported by R. Kippenhahn in 1955.[8] Huth in 1958 classified it as a β Lyr-type variable.[9] 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.[10]

M. Vetešník noted in 1968 that the light curve for the system appeared noticeably asymmetric.[9] 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.[11] 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.[12] 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.[1] The third component is thought to contribute less than 1.5% of the light output of the system.[13]

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.[14] 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.[15]

References

Further reading