16 Serpentis

16 Serpentis

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Serpens
Right ascension	15^h 36^m 29.57498^s[1]
Declination	10° 00′ 36.5574″[1]
Apparent magnitude (V)	5.261[2]
Characteristics
Spectral type	K0III: CN1 Ba0.7 Sr2[3]
U−B color index	+0.66[4]
B−V color index	+0.937[2]
Astrometry
Radial velocity (Rv)	+2.94±0.13[1] km/s
Proper motion (μ)	RA: 41.881[1] mas/yr Dec.: −125.722[1] mas/yr
Parallax (π)	14.3226 ± 0.1100 mas[1]
Distance	228 ± 2 ly (69.8 ± 0.5 pc)
Orbit[5]
Period (P)	5,324±19 d
Eccentricity (e)	0.345±0.024
Periastron epoch (T)	44,090±53
Argument of periastron (ω) (secondary)	358±4°
Semi-amplitude (K1) (primary)	3.86±0.09 km/s
Details
16 Ser A
Mass	1.70[2] M☉
Radius	8[6] R☉
Luminosity	42.7[2] L☉
Surface gravity (log g)	2.64±0.12[7] cgs
Temperature	4,946±51[7] K
Metallicity [Fe/H]	−0.13±0.06[7] dex
Rotational velocity (v sin i)	1.4[6] km/s
Age	2.40[2] Gyr
Other designations
16 Ser, BD+10°2884, FK5 3226, GC 20981, HD 139195, HIP 76425, HR 5802, SAO 101640[8]
Database references
SIMBAD	data

16 Serpentis is a binary star^[5] system in the Serpens Caput portion of the equatorial constellation of Serpens,^[8] located 228 light years from the Sun. It is visible to the naked eye as a fain, orange-hued star with an apparent visual magnitude of 5.261.^[2] The system is moving further from the Earth with a heliocentric radial velocity of +3 km/s.^[1]

The variable radial velocity of this star was discovered at Lick Observatory and was announced by J. H. Moore in 1924. It is a single-lined spectroscopic binary with an orbital period of 14.58 years and an eccentricity of 0.345.^[5] The visible component is an evolved giant star with a stellar classification of K0III: CN1 Ba0.7 Sr2.^[3] This is a mild barium star^[9] with the suffix notation above indicating associated abundance anomalies. The companion is a presumed white dwarf star that has already passed through its giant stage, during which time it enhanced the envelope of the companion with s-process elements. The pair form one of the widest barium star binaries known, which may account for the mildness of the barium anomaly.^[5]

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
2. Luck, R. Earle (2015). "Abundances in the Local Region. I. G and K Giants". Astronomical Journal. 150 (3). 88. arXiv:1507.01466. Bibcode:2015AJ....150...88L. doi:10.1088/0004-6256/150/3/88. S2CID 118505114.]
3. Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
4. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
5. Griffin, R. F. (February 1991). "Spectroscopic binary orbits from photoelectric radial velocities. Paper 96: 16 Serpentis". The Observatory. 111: 29–37. Bibcode:1991Obs...111...29G.
6. Massarotti, Alessandro; et al. (January 2008). "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity". The Astronomical Journal. 135 (1): 209–231. Bibcode:2008AJ....135..209M. doi:10.1088/0004-6256/135/1/209.
7. Prugniel, Ph.; et al. (July 2011). "The atmospheric parameters and spectral interpolator for the MILES stars". Astronomy & Astrophysics. 531: A165. arXiv:1104.4952. Bibcode:2011A&A...531A.165P. doi:10.1051/0004-6361/201116769. S2CID 54940439.
8. "16 Ser". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-03-22.
9. Tomkin, J.; Lambert, D. L. (1986). "Heavy-element abundances in the mild barium stars Omicron Virginis and 16 Serpentis". The Astrophysical Journal. 311: 819. Bibcode:1986ApJ...311..819T. doi:10.1086/164821.