Gliese 687

Gliese 687, or GJ 687 (Gliese–Jahreiß 687) is a red dwarf in the constellation Draco. This is one of the closest stars to the Sun and lies at an approximate distance of less than 15 light years. Even though it is close by, it has a magnitude of about 9, so it can only be seen through a moderately sized telescope. Gliese 687 has a high proper motion, advancing 1.304 arcseconds per year across the sky. It has a net relative velocity of about 39 km/s.[2] It is known to have a Neptune-mass planet.[7] In old books and articles it is refeered as Argelander Oeltzen 17415.[8]

Gliese 687
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension  17h 36m 25.8999s[1]
Declination +68° 20′ 20.909″[1]
Apparent magnitude (V) 9.15[2]
Characteristics
Spectral type M3.5 V[3]
U−B color index 1.06
B−V color index 1.49
Astrometry
Radial velocity (Rv)–23.2[4] km/s
Proper motion (μ) RA: –320.47[1] mas/yr
Dec.: –1269.55[1] mas/yr
Parallax (π)220.86 ± 0.92[1] mas
Distance14.77 ± 0.06 ly
(4.53 ± 0.02 pc)
Absolute magnitude (MV)10.87
Details
Mass0.401 ± 0.040[5] M☉
Radius0.492 ± 0.038[5] R☉
Surface gravity (log g)4.66[5] cgs
Temperature3,095 ± 107[5] K
Metallicity [Fe/H]+0.11 ± 0.20[5] dex
Rotational velocity (v sin i)<2.8[6] km/s
Other designations
BD +68°946, GCTP 4029.00, GJ 687, HIP 86162, LHS 450, LTT 15232, SAO 17568.[2]
Database references
SIMBADdata

Properties

Gliese 687 has about 40% of the Sun's mass and nearly 50% of the Sun's radius. Compared to the Sun, it has a slightly higher proportion of elements with higher atomic numbers than helium.[5] It appears to have a rotation of 60 days and to be somewhat chromospherically active.

It displays no excess of infrared radiation that would indicate orbiting dust.[9]

Planetary System

It is known to have a planet, Gliese 687 b, with a mass of 18.394 Earth masses (which makes it comparable to Neptune), an orbital period of 38.14 days, and a low orbital eccentricity.[7]

The Gliese 687 planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 18.394 M⊕ 0.16353 38.14 0.04 — —

X-ray source

Gliese 687 is a solitary red dwarf that emits X-rays.[10]

gollark: The thing which makes it monady is that you can do `x >>= f`, which in this case takes a `Maybe` x, and if it is `Just a`, passes that `a` to `f`, which then returns another `Maybe`.
gollark: Anyway, ignoring LyricLy, the bee entity: `Maybe` can be `Just x`, representing that it has an x, or `Nothing`, representing that it contains *no* x. You can do `return`/`pure`, which gives you a `Just x` for any `x`.
gollark: Or possibly binary. Something like that.
gollark: Those are different, I think it just means "Unary operator" in APL.
gollark: `IO` is just `State` but it stores the entire real world.

See also
  • List of nearest stars

References
  1. Perryman, M. A. C.; et al. (July 1997). "The HIPPARCOS Catalogue". Astronomy & Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P.
  2. "LHS 450 -- High proper-motion Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2009-11-12.
  3. Endl, Michael; Cochran, William D.; Kürster, Martin; Paulson, Diane B.; Wittenmyer, Robert A.; MacQueen, Phillip J.; Tull, Robert G. (September 2006). "Exploring the Frequency of Close-in Jovian Planets around M Dwarfs". The Astrophysical Journal. 649 (1): 436–443. arXiv:astro-ph/0606121. Bibcode:2006ApJ...649..436E. doi:10.1086/506465.
  4. Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Alan Henry Batten; John Frederick Heard (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: Academic Press. Bibcode:1967IAUS...30...57E.
  5. Berger, D. H.; et al. (2006). "First Results from the CHARA Array. IV. The Interferometric Radii of Low-Mass Stars". The Astrophysical Journal. 644 (1): 475–483. arXiv:astro-ph/0602105. Bibcode:2006ApJ...644..475B. doi:10.1086/503318.
  6. Jenkins, J. S.; Ramsey, L. W.; Jones, H. R. A.; Pavlenko, Y.; Gallardo, J.; Barnes, J. R.; Pinfield, D. J. (October 2009). "Rotational Velocities for M Dwarfs". The Astrophysical Journal. 704 (2): 975–988. arXiv:0908.4092. Bibcode:2009ApJ...704..975J. doi:10.1088/0004-637X/704/2/975.
  7. Burt, Jennifer; Vogt, Steven S.; Butler, R. Paul; Hanson, Russell; Meschiari, Stefano; Rivera, Eugenio J.; Henry, Gregory W.; Laughlin, Gregory (2014). "The Lick–Carnegie exoplanet survey: Gliese 687 b: A Neptune-mass planet orbiting a nearby red dwarf". The Astrophysical Journal. 789 (2): 114. arXiv:1405.2929. Bibcode:2014ApJ...789..114B. doi:10.1088/0004-637X/789/2/114.
  8. Lynn, W. T. (June 1890). "On the proper motions of three stars". Monthly Notices of the Royal Astronomical Society. 50 (8): 519–520. Bibcode:1890MNRAS..50..519L. doi:10.1093/mnras/50.8.519.
  9. Gautier, Thomas N., III; et al. (September 2007). "Far-Infrared Properties of M Dwarfs". The Astrophysical Journal. 667 (1): 527–536. arXiv:0707.0464. Bibcode:2007ApJ...667..527G. doi:10.1086/520667.CS1 maint: multiple names: authors list (link)
  10. Schmitt JHMM; Fleming TA; Giampapa MS (September 1995). "The X-ray view of the low-mass stars in the solar neighborhood". Astrophys. J. 450 (9): 392–400. Bibcode:1995ApJ...450..392S. doi:10.1086/176149.

Notes
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