3 Serpentis

3 Serpentis is a binary star in the constellation Serpens with an orbital period of approximately 66 years. It is dimly visible to the naked eye with an apparent magnitude of 5.337. Located around 114 parsecs (370 ly) distant, it is an orange giant of spectral type K0III, a star that has used up its core hydrogen.

3 Serpentis
Observation data
Epoch J2000      Equinox J2000
Constellation Serpens
Right ascension 15h 15m 11.352s[1]
Declination +04° 56′ 21.71″[1]
Apparent magnitude (V) 5.337[2]
Characteristics
Spectral type K0III[3]
Astrometry
Proper motion (μ) RA: −24.90±0.81[1] mas/yr
Dec.: 4.80±0.54[1] mas/yr
Parallax (π)8.74 ± 0.75[1] mas
Distance370 ± 30 ly
(114 ± 10 pc)
Absolute magnitude (MV)+1.15[4]
Orbit[5]
Period (P)66±5 yr
Semi-major axis (a)229±2″
Eccentricity (e)0.962±0.005
Inclination (i)132±4°
Details
Surface gravity (log g)+2.77[6] cgs
Temperature4,550[6] K
Metallicity [Fe/H]+0.03[6] dex
Rotational velocity (v sin i)1.5[7] km/s
Other designations
BD+05° 2985, FK5 562, HD 135482, HIP 74649, HR 5675, SAO 120916[8]
Database references
SIMBADdata

The two components of 3 Serpentis can be resolved using speckle interferometry and were separated by 0.23" in 2014. The orbit is highly eccentric and at periastron passage in 1997, the two are calculated to have been only 6 mas apart.[5]

Individual spectra for the two components of 3 Serpentis cannot be obtained and the spectral type of K0III is for the two stars combined. The primary is 2.5 magnitudes brighter than the secondary and cooler. The combined spectral type indicates that the primary is likely to have evolved away from the main sequence, but comparison of the colour and brightness of the secondary suggest it is still a main sequence star.[5]

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.Vizier catalog entry
  2. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H.
  3. Cenarro, A. J.; Peletier, R. F.; Sanchez-Blazquez, P.; Selam, S. O.; Toloba, E.; Cardiel, N.; Falcon-Barroso, J.; Gorgas, J.; Jimenez-Vicente, J.; Vazdekis, A. (2007). "Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters". Monthly Notices of the Royal Astronomical Society. 374 (2): 664–690. arXiv:astro-ph/0611618. Bibcode:2007MNRAS.374..664C. doi:10.1111/j.1365-2966.2006.11196.x.
  4. McWilliam, Andrew (1990). "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances". The Astrophysical Journal Supplement Series. 74: 1075. Bibcode:1990ApJS...74.1075M. doi:10.1086/191527.
  5. Horch, Elliott P.; et al. (2015). "Observations of Binary Stars with the Differential Speckle Survey Instrument. VI. Measures during 2014 at the Discovery Channel Telescope". The Astronomical Journal. 150 (5): 151. arXiv:1509.03498. Bibcode:2015AJ....150..151H. doi:10.1088/0004-6256/150/5/151.
  6. Soubiran, Caroline; Le Campion, Jean-François; Brouillet, Nathalie; Chemin, Laurent (2016). "The PASTEL catalogue: 2016 version". Astronomy & Astrophysics. 591: A118. arXiv:1605.07384. Bibcode:2016A&A...591A.118S. doi:10.1051/0004-6361/201628497.
  7. De Medeiros, J. R.; Do Nascimento, J. D.; Sankarankutty, S.; Costa, J. M.; Maia, M. R. G. (2000). "Rotation and lithium in single giant stars". Astronomy and Astrophysics. 363: 239. arXiv:astro-ph/0010273. Bibcode:2000A&A...363..239D.
  8. "* 3 Ser". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 July 2014.
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