Astronomy:HD 166620
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| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Hercules[1] |
| Right ascension | 18h 09m 37.41621s[2] |
| Declination | +38° 27′ 27.9980″[2] |
| Apparent magnitude (V) | 6.40[3] |
| Characteristics | |
| Spectral type | K2 V[4] |
| U−B color index | +0.585[3] |
| B−V color index | +0.875[3] |
| Astrometry | |
| Radial velocity (Rv) | −19.51±0.12[2] km/s |
| Proper motion (μ) | RA: −316.454[2] mas/yr Dec.: −468.348[2] mas/yr |
| Parallax (π) | 90.1234 ± 0.0156[2] mas |
| Distance | 36.190 ± 0.006 ly (11.096 ± 0.002 pc) |
| Absolute magnitude (MV) | 6.17[5] |
| Details[6] | |
| Mass | 0.76+0.032 −0.019 M☉ |
| Radius | 0.77+0.007 −0.006 R☉ |
| Luminosity | 0.36+0.02 −0.01 L☉ |
| Surface gravity (log g) | 4.55+0.02 −0.01 cgs |
| Temperature | 4,989±48 K |
| Metallicity [Fe/H] | −0.21±0.04 dex |
| Rotation | 42.4 d |
| Rotational velocity (v sin i) | <2.0 km/s |
| Age | 10.09+2.73 −3.76 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 166620 or HR 6806 is a solitary, orange, main sequence, and Sun-like (K2 V) star located thirty-six light-years away,[8] in the constellation Hercules. The star is smaller than the Sun, with around 79% of the solar mass and radius, and 35% of the solar luminosity.[9] It appears to be rotating slowly with an estimated period of 42 days. In 1988, it was noticed that the star had an inactive chromosphere, with a surface magnetic field strength of only 1,500 G.[10] From 1990 activity in the chromosphere increased, in line with a 16 year stellar cycle previously observed. But, sometime after 1994 (exact date unknown because of a data collection gap between 1995 and 2004) chromospheric activity greatly reduced, and has stayed flat for more than 16 years. As of 2022,[update] the star appears to have entered the equivalent of a Maunder minimum.[8] The star is around six billion years of age.[11]
There was suspected to be a nearby very cool, and very dim, T9 to Y brown dwarf companion, WISE J180901.07+383805.4, at an angular separation of 769″, which would have corresponded to a projected separation of 8460 AU at the distance of HD 166620. However, with further observation it was found to be bluer than at first thought and more typical of a slightly brighter T7 dwarf, which would place it at a much greater distance of 91 ly (28 pc)—ruling out a physical association. This is confirmed by the differing proper motion of the star and this object.[12]
This star has been targeted by planet searches using the radial velocity method, but as of 2023 no evidence of a planetary companion has been found. Observations rule out the existence of planets down to super-Earth masses with orbital periods less than 2,800 days; at periods less than 10 days, planets less massive than Earth would be detectable.[6]
References
- ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A.
- ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 3.0 3.1 3.2 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data (SIMBAD), Bibcode: 1986EgUBV........0M.
- ↑ Gray, R. O. et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal 132 (1): 161–170, doi:10.1086/504637, Bibcode: 2006AJ....132..161G.
- ↑ Holmberg, J. et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics 501 (3): 941–947, doi:10.1051/0004-6361/200811191, Bibcode: 2009A&A...501..941H.
- ↑ 6.0 6.1 John, A. Anna et al. (October 2023). "Sub-m s-1 upper limits from a deep HARPS-N radial-velocity search for planets orbiting HD 166620 and HD 144579". Monthly Notices of the Royal Astronomical Society 525 (2): 1687-1704. doi:10.1093/mnras/stad2381. Bibcode: 2023MNRAS.525.1687J.
- ↑ "HD 166620". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+166620.
- ↑ 8.0 8.1 Baum, Anna C.; Wright, Jason T. et al. (March 22, 2022). "Five Decades of Chromospheric Activity in 59 Sun-like Stars and New Maunder Minimum Candidate HD 166620". The Astronomical Journal (American Astronomical Society) 163 (4): 183. doi:10.3847/1538-3881/ac5683. ISSN 0004-6256. Bibcode: 2022AJ....163..183B.
- ↑ Marsden, S. C. et al. (November 2014), "A BCool magnetic snapshot survey of solar-type stars", Monthly Notices of the Royal Astronomical Society 444 (4): 3517–3536, doi:10.1093/mnras/stu1663, Bibcode: 2014MNRAS.444.3517M.
- ↑ Basri, Gibor; Marcy, Geoffrey W. (July 1988), "Physical realism in the analysis of stellar magnetic fields", Astrophysical Journal, Part 1 330: 274–285, doi:10.1086/166471, Bibcode: 1988ApJ...330..274B.
- ↑ Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008), "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics", The Astrophysical Journal 687 (2): 1264–1293, doi:10.1086/591785, Bibcode: 2008ApJ...687.1264M.
- ↑ Luhman, Kevin L. et al. (December 2012), "New M, L, and T Dwarf Companions to Nearby Stars from the Wide-field Infrared Survey Explorer", The Astrophysical Journal 760 (2): 9, doi:10.1088/0004-637X/760/2/152, 152, Bibcode: 2012ApJ...760..152L.
External links
- "ARICNS: 01473". ARICNS. Centre of Astronomy, Heidelberg University. https://wwwadd.zah.uni-heidelberg.de/datenbanken/aricns/cnspages/4c4c01473.htm.
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