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HD 204018

location of HD 204018 (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Microscopium
A
Right ascension	21 27 01.62303
Declination	−42° 32′ 52.5560″
Apparent magnitude (V)	5.58±0.01
B
Right ascension	21 27 01.75500
Declination	−42° 32′ 55.0458″
Apparent magnitude (V)	8.09±0.01
Characteristics
A
Evolutionary stage	subgiant
Spectral type	kA4 hF0 V mF6
U−B color index	+0.15
B−V color index	+0.39
B
Spectral type	F8 V
U−B color index	+0.06
B−V color index	+0.55
Astrometry
Radial velocity (Rv)	18.3±2.8 km/s
A
Proper motion (μ)	RA: −48.257 mas/yr Dec.: +13.160 mas/yr
Parallax (π)	18.489 ± 0.0498 mas
Distance	176.4 ± 0.5 ly (54.1 ± 0.1 pc)
Absolute magnitude (MV)	+1.74
B
Proper motion (μ)	RA: −53.002 mas/yr Dec.: +15.410 mas/yr
Parallax (π)	18.5325 ± 0.0349 mas
Distance	176.0 ± 0.3 ly (54.0 ± 0.1 pc)
Absolute magnitude (MV)	+4.00
Details
A
Mass	1.65±0.11 M☉
Radius	2.55±0.13 R☉
Luminosity	15±1.2 L☉
Surface gravity (log g)	3.86±0.08 cgs
Temperature	6,778 K
Rotational velocity (v sin i)	85 km/s
Age	1.36±0.19 Gyr
B
Mass	1.02 M☉
Radius	1.09±0.21 R☉
Surface gravity (log g)	4.29 cgs
Temperature	6,235±115 K
Metallicity	−0.11 dex
Age	3.46 Gyr
Other designations
69 G. Microscopii[20], CD−43°14539, CPD−43°9451, GC 30021, HD 204018, HIP 105913, HR 8202, SAO 230692, WDS J21270-4233AB
Database references
SIMBAD	The system
	A
	B

HD 204018, also designated as HR 8202, is a visual binary located in the southern constellation Microscopium. The primary has an apparent magnitude of 5.58, making it faintly visible to the naked eye under ideal conditions. The companion has an apparent magnitude of 8.09. The system is located relatively close at a distance of 176 light years based on Gaia DR3 parallax measurements but is receding with a heliocentric radial velocity of 18.3 km/s. At its current distance, HD 204018's combined brightness is diminished by 0.13 magnitudes due to interstellar dust.

HD 204018A is an Am star with a stellar classification of kA4hF0 VmF6, indicating that it has the calcium K-line of an A4 star, the hydrogen lines of a F0 main-sequence star and the metallic lines of a F6 star. It has 1.65 times the mass of the Sun and 2.55 times the Sun's radius. It radiates 15 times the luminosity of the Sun from its photosphere at an effective temperature of 6,778 K, giving it a yellowish-white hue. At an age of 1.5 billion years, HD 2014018A is estimated to be on the subgiant branch. An alternate model places it on the main sequence at an age of 1,35 billion years. The object spins at a moderate speed with a projected rotational velocity of 85 km/s.

The companion is an F8 main sequence star located 2+1⁄2" away along a position angle of 151°. It has an angular diameter of 0.186±0.035 arcseconds, which yields a radius of 1.09 R_☉ at its estimated distance. It has 102% times the mass of the Sun and an effective temperature of 6,235 K. HD 204018B is estimated to be 3.46 billion years old and is slightly metal deficient.

There is a magnitude 12 co-moving companion located 295.3" away from the system along a position angle of 75°. It is a red dwarf with an estimated spectral class of K6 and any orbit would take over a million years.

References

1. ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
2. ^ Fabricius, C.; Høg, E.; Makarov, V. V.; Mason, B. D.; Wycoff, G. L.; Urban, S. E. (March 2002). "The Tycho double star catalogue". Astronomy & Astrophysics. 384 (1): 180–189. Bibcode:2002A&A...384..180F. doi:10.1051/0004-6361:20011822. eISSN 1432-0746. ISSN 0004-6361.
3. ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
4. ^ Corbally, C. J. (December 1984). "Close visual binaries. III - Parameters and evolutionary status". The Astronomical Journal. 89: 1887. Bibcode:1984AJ.....89.1887C. doi:10.1086/113700. ISSN 0004-6256.
5. ^ Abt, Helmut A.; Morrell, Nidia I. (July 1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". The Astrophysical Journal Supplement Series. 99: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182. ISSN 0067-0049.
6. ^ Feinstein, A. (April 1967). "Multicolor UBVRI observations of metallic-line stars". Publications of the Astronomical Society of the Pacific. 79: 184. Bibcode:1967PASP...79..184F. doi:10.1086/128464. eISSN 1538-3873. ISSN 0004-6280.
7. ^ Corbally, C. J. (August 1984). "Close visual binaries. I - MK classifications". The Astrophysical Journal Supplement Series. 55: 657. Bibcode:1984ApJS...55..657C. doi:10.1086/190973. eISSN 1538-4365. ISSN 0067-0049.
8. ^ Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. eISSN 1562-6873. ISSN 1063-7737. S2CID 119231169.
9. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
10. ^ Allende Prieto, C.; Lambert, D. L. (December 1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: masses, radii and effective temperatures". Astronomy and Astrophysics. 352: 555–562. arXiv:astro-ph/9911002. Bibcode:1999A&A...352..555A. ISSN 0004-6361.
11. ^ Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (October 2004). "The angular sizes of dwarf stars and subgiants". Astronomy & Astrophysics. 426 (1): 297–307. arXiv:astro-ph/0404180. Bibcode:2004A&A...426..297K. doi:10.1051/0004-6361:20035930. eISSN 1432-0746. ISSN 0004-6361.
12. ^ Chandler, Colin Orion; McDonald, Iain; Kane, Stephen R. (17 February 2016). "The Catalog of Earth-Like Exoplanet Survey Targets (CELESTA): A Database of Habitable Zones Around Nearby Stars". The Astronomical Journal. 151 (3): 59. arXiv:1510.05666. Bibcode:2016AJ....151...59C. doi:10.3847/0004-6256/151/3/59. eISSN 1538-3881.
13. Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. eISSN 1538-3881. hdl:1721.1/124721. S2CID 166227927.
14. ^ Schofield, Mathew; et al. (14 March 2019). "The Asteroseismic Target List for Solar-like Oscillators Observed in 2 minute Cadence with the Transiting Exoplanet Survey Satellite". The Astrophysical Journal Supplement Series. 241 (1): 12. arXiv:1901.10148. Bibcode:2019ApJS..241...12S. doi:10.3847/1538-4365/ab04f5. eISSN 1538-4365.
15. ^ Huang, Su-Shu (September 1953). "A Statistical Study of the Rotation of the Stars". The Astrophysical Journal. 118: 285. Bibcode:1953ApJ...118..285H. doi:10.1086/145751. eISSN 1538-4357. ISSN 0004-637X.
16. ^ Anders, F.; et al. (February 2022). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia EDR3 stars brighter than G = 18.5". Astronomy & Astrophysics. 658: A91. arXiv:2111.01860. Bibcode:2022A&A...658A..91A. doi:10.1051/0004-6361/202142369. eISSN 1432-0746. ISSN 0004-6361.
17. ^ Lang, Kenneth R. (2006). Astrophysical formulae. Astronomy and astrophysics library. Vol. 1 (3 ed.). Birkhäuser. ISBN 3-540-29692-1.. The radius (R_*) is given by:

    ${\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(54\cdot 0.187\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 2.17\cdot R_{\bigodot }\end{aligned}}}$

18. ^ Stevens, Daniel J.; Stassun, Keivan G.; Gaudi, B. Scott (29 November 2017). "Empirical Bolometric Fluxes and Angular Diameters of 1.6 Million Tycho-2 Stars and Radii of 350,000 Stars with Gaia DR1 Parallaxes". The Astronomical Journal. 154 (6): 259. arXiv:1708.05025. Bibcode:2017AJ....154..259S. doi:10.3847/1538-3881/aa957b. eISSN 1538-3881. S2CID 119191064.
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20. Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
21. "HR 8202". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 21 December 2022.
22. Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society. 472 (4): 3805–3820. arXiv:1709.01160. Bibcode:2017MNRAS.472.3805G. doi:10.1093/mnras/stx2219. eISSN 1365-2966. ISSN 0035-8711.
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24. Tokovinin, Andrei (23 February 2018). "The Updated Multiple Star Catalog". The Astrophysical Journal Supplement Series. 235 (1): 6. arXiv:1712.04750. Bibcode:2018ApJS..235....6T. doi:10.3847/1538-4365/aaa1a5. eISSN 1538-4365.

v t e Constellation of Microscopium
List of stars in Microscopium Microscopium in Chinese astronomy
Stars	Bayer α β γ δ ε ζ η θ θ ι ν Flamsteed 2 PsA 3 PsA Variable R S T U AT AU AV AX BO DD HR 7817 7893 7909 7933 7971 7987 8046 8100 8104 8108 8200 8202 HD 202628 Other PSR J2124−3358 WASP-7
Exoplanets WASP-7b
Galaxies	NGC 6925 7012 7057 7060 Other ESO 286-19
Category

• Binary stars
• A-type subgiants
• Am stars
• F-type main-sequence stars
• Microscopium
• Gould objects
• Durchmusterung objects
• Henry Draper Catalogue objects
• Hipparcos objects
• Bright Star Catalogue objects