Gliese 221

Gliese 221 (GJ 221), also known as BD-06 1339, is a star with an exoplanetary companion in the equatorial constellation of Orion. It is too faint to be visible to the naked eye, having an apparent visual magnitude of 9.70[2] and an absolute magnitude of 8.15.[4] Using parallax measurements, the distance to this system can be estimated as 66.2 light-years. It is receding from the Sun with a radial velocity of +23 km/s.[1] This is a high proper motion star, traversing the celestial sphere at an angular rate of 0.333″·yr−1.[7]

Gliese 221
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Orion
Right ascension 05h 53m 00.285s[1]
Declination −05° 59′ 41.44″[1]
Apparent magnitude (V) 9.70[2]
Characteristics
Spectral type K7V/M0V[3]
B−V color index 1.321±0.001[2]
Astrometry
Radial velocity (Rv)+22.9±0.4[1] km/s
Proper motion (μ) RA: −1.170 mas/yr[1]
Dec.: −346.762 mas/yr[1]
Parallax (π)49.2485 ± 0.0185 mas[1]
Distance66.23 ± 0.02 ly
(20.305 ± 0.008 pc)
Absolute magnitude (MV)8.154±0.077[4]
Details
Mass0.72±0.21[5] M☉
Radius0.613±0.064[4] R☉
Luminosity0.095±0.01[5] L☉
Surface gravity (log g)4.74±0.02[5] cgs
Temperature4,324±100[5] K
Metallicity [Fe/H]−0.34±0.08[5] dex
Age4.4±4[5] Gyr
Other designations
BD−06 1339, GJ 221, HIP 27803, PPM 188554, LTT 2396, 2MASS J05530028-0559410,[6] Gaia EDR3 3022099969137163904
Database references
SIMBADdata
Exoplanet Archivedata
Extrasolar Planets
Encyclopaedia		data

This is a late K-type or early M-type main-sequence star with a stellar classification of K7V/M0V.[3] It has 72% of the mass and 61% of the radius of the Sun.[5] The star is roughly 4.4[5] billion years old and is depleted in heavy elements, containing just 46% of solar abundance of iron.[5] It is an active star and the level of chromospheric activity has been found to vary significantly over time.[3] The star is radiating 10%[5] of the luminosity of the Sun from its photosphere at an effective temperature of 4,324 K.[5]

Planetary system

From 2003 to 2012, the star was under observance from the High Accuracy Radial Velocity Planet Searcher (HARPS). It is becoming less active and this reduced activity allowed for lower-mass planetary measurements to be made.

A super-Venus planet, and an eccentric Neptune / Saturn in the habitable zone, were deduced by radial velocity in January 2013.[8] They were confirmed in May 2013.[9] In January 2014, a candidate planet d was proposed.[10]

The planet Gliese 221b is not transiting the disk of the parent star,[11] and its existence was disputed in 2022.[12]

The Gliese 221 planetary system[13][8]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b (disputed[12]) >8.5806 ± 1.2712 M🜨 0.0428 ± 0.0007 3.8728 ± 0.0004 - — —
c >54.026 ± 9.534 M🜨 0.435 ± 0.007 125.94 ± 0.44 0.31 ± 0.11 — —
d (unconfirmed) 22.246 M🜨 1.0947 500 — — —

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  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. Lo Curto, G.; et al. (March 2013), "The HARPS search for southern extra-solar planets. XXXII. New multi-planet systems in the HARPS volume limited sample: a super-Earth and a Neptune in the habitable zone", Astronomy & Astrophysics, 551: 7, arXiv:1301.2741, Bibcode:2013A&A...551A..59L, doi:10.1051/0004-6361/201220415, S2CID 116916728, A59.
  4. Houdebine, E. R.; et al. (2016). "Rotation-Activity Correlations in K and M Dwarfs. I. Stellar Parameters and Compilations of v sin I and P/Sin I for a Large Sample of Late-K and M Dwarfs". The Astrophysical Journal. 822 (2): 97. arXiv:1604.07920. Bibcode:2016ApJ...822...97H. doi:10.3847/0004-637X/822/2/97. S2CID 119118088.
  5. Sousa, S. G.; et al. (2018), "SWEET-Cat updated", Astronomy & Astrophysics, 620: A58, arXiv:1810.08108, Bibcode:2018A&A...620A..58S, doi:10.1051/0004-6361/201833350, S2CID 119374557.
  6. "BD-06 1339". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-11-18.
  7. Luyten, W. J. (June 1995), "NLTT Catalogue", VizieR On-line Data Catalog: I/98A. Originally published in: 1979nltt.book.....L, Bibcode:1995yCat.1098....0L.
  8. Lo Curto, G.; et al. (2013), "The HARPS search for southern extrasolar planets: XXXVI. New multi-planet systems in the HARPS volume limited sample: a super-Earth and a Neptune in the habitable zone", Astronomy & Astrophysics, 551: A59, arXiv:1301.2741, Bibcode:2013A&A...551A..59L, doi:10.1051/0004-6361/201220415, S2CID 116916728.
  9. Arriagada, Pamela; et al. (2013), "Two Planetary Companions Around the K7 Dwarf Gj 221: A Hot Super-Earth and a Candidate in the Sub-Saturn Desert Range", The Astrophysical Journal, 771 (1): 42, arXiv:1305.2203, Bibcode:2013ApJ...771...42A, doi:10.1088/0004-637X/771/1/42, S2CID 119212312.
  10. Tuomi, Mikko (2014), "A new cold sub-Saturnian candidate planet orbiting GJ 221", Monthly Notices of the Royal Astronomical Society: Letters, 440: L1–L5, arXiv:1401.4000, doi:10.1093/mnrasl/slu014
  11. Gillon, M.; et al. (2017), "The Spitzer search for the transits of HARPS low-mass planets", Astronomy & Astrophysics, 601: A117, arXiv:1701.01303, Bibcode:2017A&A...601A.117G, doi:10.1051/0004-6361/201629270, S2CID 86862862.
  12. Simpson, Emilie R.; Fetherolf, Tara; Kane, Stephen R.; Li, Zhexing; Pepper, Joshua; Močnik, Teo (2022). "Revisiting BD-06 1339b: A Likely False Positive Caused by Stellar Activity". The Astronomical Journal. 163 (5): 215. arXiv:2203.06191. Bibcode:2022AJ....163..215S. doi:10.3847/1538-3881/ac5d41. S2CID 247446960.
  13. Planet BD-061339b.
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