2 Lyncis

2 Lyncis is a binary star system in the northern constellation Lynx. It is visible to the naked eye, having an apparent visual magnitude of 4.44.^[2] The distance to this system, judging by an annual parallax shift of 20.83±0.40 mas,^[1] is around 157 light years. It is moving closer to the Sun with a heliocentric radial velocity of −2 km/s.^[5]

2 Lyncis

2 Lyncis in optical light.
Observation data Epoch J2000      Equinox J2000
Constellation	Lynx
Right ascension	06h 19m 37.38458s[1]
Declination	+59° 00′ 39.4683″[1]
Apparent magnitude (V)	4.44[2]
Characteristics
Spectral type	A2 Vs[3]
B−V color index	0.032±0.004[2]
Variable type	Eclipsing binary[4]
Astrometry
Radial velocity (Rv)	−2.0±0.1[5] km/s
Proper motion (μ)	RA: −5.35[1] mas/yr Dec.: +23.86[1] mas/yr
Parallax (π)	20.83 ± 0.40 mas[1]
Distance	157 ± 3 ly (48.0 ± 0.9 pc)
Absolute magnitude (MV)	1.03[2]
Orbit[6]
Period (P)	1306.82±0.96 d
Eccentricity (e)	0.497±0.010
Periastron epoch (T)	2450962.0±2.0
Argument of periastron (ω) (secondary)	186.30±0.79°
Semi-amplitude (K1) (primary)	3.281±0.044 km/s
Details[6]
2 Lyn A
Mass	2.32±0.02[3] M☉
Radius	2.2 R☉
Luminosity	39.5+1.8 −1.7[3] L☉
Surface gravity (log g)	4.1±0.1 cgs
Temperature	9,310±100 K
Rotation	1.56 d
Rotational velocity (v sin i)	44 km/s
2 Lyn B
Mass	0.46 M☉
Other designations
2 Lyn, UZ Lyn, BD+59° 959, FK5 237, HD 43378, HIP 30060, HR 2238, SAO 25665[7]
Database references
SIMBAD	data

This is a spectroscopic binary star system with an orbital period of around 3.6 years and an eccentricity of 0.5. It is classified as a probable (91% chance) eclipsing binary with the variable star designation UZ Lyn, showing a net magnitude decrease of 0.3 during an occultation.^[4]

The primary component is an A-type main-sequence star^[6] with a stellar classification of A2 Vs,^[3] where the 's' indicates narrow (sharp) absorption lines. The orbiting companion may be the source of the X-ray emission from this system, as stars similar to the primary component do not generally produce detectable levels of X-rays.^[8]

References

1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
3. Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
4. Avvakumova, E. A.; et al. (October 2013), "Eclipsing variables: Catalogue and classification" (PDF), Astronomische Nachrichten, 334 (8): 860, Bibcode:2013AN....334..860A, doi:10.1002/asna.201311942, hdl:10995/27061
5. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
6. Lehmann, H.; et al. (April 2003), "Binary nature and elemental abundances of 2 Lyn and HD 169981", Astronomy and Astrophysics, 402: 229–235, Bibcode:2003A&A...402..229L, doi:10.1051/0004-6361:20030253.
7. "2 Lyn". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-03-07.
8. De Rosa, R. J.; et al. (July 2011), "The Volume-limited A-Star (VAST) survey - I. Companions and the unexpected X-ray detection of B6-A7 stars", Monthly Notices of the Royal Astronomical Society, 415 (1): 854–866, arXiv:1103.4363, Bibcode:2011MNRAS.415..854D, doi:10.1111/j.1365-2966.2011.18765.x, S2CID 84181878.