Psi Serpentis

Psi Serpentis (ψ Ser, ψ Serpentis) is a triple star[5] system within the Serpens Caput part of the equatorial constellation Serpens. Based upon an annual parallax shift of 68.22 mas as seen from Earth,[1] it is located approximately 47.8 light years from the Sun. This system came closest approach to the Sun about 585,000 years ago when it made perihelion passage at an estimated distance of 23.27 ly (7.134 pc).[12] Psi Serpentis is faintly visible to the naked eye with an apparent visual magnitude of 5.84.[2]

Psi Serpentis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Serpens
Right ascension  15h 44m 01.82075s[1]
Declination +02° 30′ 54.6340″[1]
Apparent magnitude (V) 5.84[2] + 12.00[3]
Characteristics
Spectral type G5 V[4] + (M3 + M3)[5]
U−B color index +0.23[2]
B−V color index +0.68[2]
Astrometry
Radial velocity (Rv)+17.93±0.89[6] km/s
Proper motion (μ) RA: −43.11[1] mas/yr
Dec.: −143.57[1] mas/yr
Parallax (π)68.22 ± 0.66[1] mas
Distance47.8 ± 0.5 ly
(14.7 ± 0.1 pc)
Absolute magnitude (MV)+5.03[4]
Orbit[7]
Period (P)528.79 yr
Semi-major axis (a)5.037″
Eccentricity (e)0.146
Inclination (i)144.5°
Longitude of the node (Ω)210.7°
Periastron epoch (T)1939.76
Argument of periastron (ω)
(secondary)		129.5°
Details[6]
ψ Ser A
Mass0.993±0.007 M☉
Radius1.00±0.03[8] R☉
Luminosity0.98[9] L☉
Surface gravity (log g)4.48±0.02 cgs
Temperature5,683±5 K
Metallicity [Fe/H]0.036±0.006 dex
Rotational velocity (v sin i)11.01[10] km/s
Age3.2 Gyr
Other designations
ψ Ser, 23 Ser, BD+02° 2989, FK5 3248, GJ 9527, HD 140538, HIP 77052, HR 5853, SAO 121152.[11]
Database references
SIMBADdata

This system can be resolved into two components that orbit each other with a period of 528.79 years and an eccentricity of 0.146.[7] The primary, component A, is a yellow-hued G-type main sequence star with a stellar classification of G5 V. It is a solar analog, but its physical properties differ enough from the Sun to not be considered a solar twin.[4] The star has an estimated 99.3% of the mass of the Sun,[6] and it matches the Sun's radius within the margin of error.[8] It is radiating 98%[9] of the solar luminosity from its photosphere at an effective temperature of 5,683 K.[6]

When observed from 1997 through 2000, the primary component appeared to be transitioning from a maunder minimum state to a state of cycling magnetic activity.[13] It has developed a four-year activity cycle. During the period 2000–2004, it showed a strong activity cycle with little correlation between photometric variation and surface activity. This was followed by a flatter activity cycle from 2004–2008 that showed an inverse brightness variation with the level of activity. The difference in the two cycles may indicate a change from faculae-dominated to star spot-dominated variations in luminosity.[14]

The known secondary, component B, is magnitude 12.00 and lies at an angular separation of 4.6 arc seconds from the primary along a position angle of 18°, as of 2013.[3] In 2015, this component was resolved via interferometry into a binary star system with a separation of 0.22 arc seconds, corresponding to a projected separation of 3 AU. Both components, Ba and Bb, are likely red dwarfs roughly of class M3 with masses of about 25% the mass of the Sun.[5] They have a tentative orbital period of around six years and a semimajor axis of 0.19 arc seconds.[15]

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.
  2. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
  3. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122: 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
  4. Mahdi, D.; et al. (March 2016), "Solar twins in the ELODIE archive", Astronomy & Astrophysics, 587: 9, arXiv:1601.01599, Bibcode:2016A&A...587A.131M, doi:10.1051/0004-6361/201527472, A131.
  5. Rodriguez, David R.; et al. (May 2015), "Stellar multiplicity and debris discs: an unbiased sample", Monthly Notices of the Royal Astronomical Society, 449 (3): 3160–3170, arXiv:1503.01320, Bibcode:2015MNRAS.449.3160R, doi:10.1093/mnras/stv483.
  6. Ramírez, I.; et al. (December 2014), "The Solar Twin Planet Search. I. Fundamental parameters of the stellar sample", Astronomy & Astrophysics, 572: 19, arXiv:1408.4130, Bibcode:2014A&A...572A..48R, doi:10.1051/0004-6361/201424244, A48.
  7. Gatewood, G.; Mason, B. D. (2013), Information Circular No. 181 (PDF), International Astronomical Union Commission 26 (Double Stars), p. 1, retrieved 2017-03-25.
  8. Takeda, Genya; et al. (February 2007), "Structure and Evolution of Nearby Stars with Planets. II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog", The Astrophysical Journal Supplement Series, 168 (2): 297–318, arXiv:astro-ph/0607235, Bibcode:2007ApJS..168..297T, doi:10.1086/509763.
  9. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x.
  10. Martínez-Arnáiz, R.; et al. (September 2010), "Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter" (PDF), Astronomy and Astrophysics, 520: A79, arXiv:1002.4391, Bibcode:2010A&A...520A..79M, doi:10.1051/0004-6361/200913725.
  11. "psi Ser". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-03-23.
  12. Bailer-Jones, C. A. L. (March 2015), "Close encounters of the stellar kind", Astronomy & Astrophysics, 575: 13, arXiv:1412.3648, Bibcode:2015A&A...575A..35B, doi:10.1051/0004-6361/201425221, A35.
  13. Hall, Jeffrey C.; et al. (March 2007), "The Activity and Variability of the Sun and Sun-like Stars. I. Synoptic Ca II H and K Observations", The Astronomical Journal, 133 (3): 862–881, Bibcode:2007AJ....133..862H, doi:10.1086/510356.
  14. Hall, Jeffrey C.; et al. (July 2009), "The Activity and Variability of the Sun and Sun-Like Stars. II. Contemporaneous Photometry and Spectroscopy of Bright Solar Analogs", The Astronomical Journal, 138 (1): 312–322, Bibcode:2009AJ....138..312H, CiteSeerX 10.1.1.216.9004, doi:10.1088/0004-6256/138/1/312.
  15. Tokovinin, Andrei; Horch, Elliott P. (November 2016), "Speckle Interferometry of Secondary Components in Nearby Visual Binaries", The Astronomical Journal, 152 (5): 7, arXiv:1608.06586, Bibcode:2016AJ....152..116T, doi:10.3847/0004-6256/152/5/116, 116.
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