Astronomy:HD 204018

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Short description: Visual binary in Microscopium
HD 204018
Microscopium constellation map.svg
Red circle.svg
location of HD 204018 (circled)
Observation data
{{#ifeq:J2000.0 (ICRS)|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| [[History:Epoch|Epoch J2000.0 (ICRS)]]      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000.0 (ICRS)}}
Constellation Microscopium
A
Right ascension  21h 27m 01.62303s[1]
Declination −42° 32′ 52.5560″[1]
Apparent magnitude (V) 5.58±0.01[2]
B
Right ascension  21h 27m 01.75500s[3]
Declination −42° 32′ 55.0458″[3]
Apparent magnitude (V) 8.09±0.01[2]
Characteristics
A
Evolutionary stage subgiant[4]
Spectral type kA4 hF0 V mF6[5]
U−B color index +0.15[6]
B−V color index +0.39[6]
B
Spectral type F8 V[7]
U−B color index +0.06[7]
B−V color index +0.55[7]
Astrometry
Radial velocity (Rv)18.3±2.8[8] km/s
A
Proper motion (μ) RA: −48.257[1] mas/yr
Dec.: +13.160[1] mas/yr
Parallax (π)18.489 ± 0.0498[1] mas
Distance176.4 ± 0.5 ly
(54.1 ± 0.1 pc)
Absolute magnitude (MV)+1.74[9]
B
Proper motion (μ) RA: −53.002 mas/yr
Dec.: +15.410 mas/yr
Parallax (π)18.5325 ± 0.0349[3] mas
Distance176.0 ± 0.3 ly
(54.0 ± 0.1 pc)
Absolute magnitude (MV)+4.00[7]
Details
A
Mass1.65±0.11[10] M☉
Radius2.55±0.13[11] R☉
Luminosity15±1.2[12] L☉
Surface gravity (log g)3.86±0.08[13] cgs
Temperature6,778[14] K
Rotational velocity (v sin i)85[15] km/s
Age1.36±0.19[1] Gyr
B
Mass1.02[16] M☉
Radius1.09±0.21[17] R☉
Surface gravity (log g)4.29[16] cgs
Temperature6,235±115[18] K
Age3.46[19] Gyr
Other designations
CD−43°14539, CPD−43°9451, GC 30021, HD 204018, HIP 105913, HR 8202, SAO 230692, WDS J21270-4233AB[20]
Database references
SIMBADThe 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,[2] making it faintly visible to the naked eye under ideal conditions. The companion has an apparent magnitude of 8.09.[2] The system is located relatively close at a distance of 176 light years based on Gaia DR3 parallax measurements[1][3] but is receding with a heliocentric radial velocity of 18.3 km/s.[8] At its current distance, HD 204018's combined brightness is diminished by 0.13 magnitudes due to interstellar dust.[21]

HD 204018A is an Am star with a stellar classification of kA4hF0 VmF6,[5] 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[10] and 2.55 times the Sun's radius.[11] It radiates 15 times the luminosity of the Sun[12] from its photosphere at an effective temperature of 6,778 K,[14] giving it a yellowish-white hue. At an age of 1.5 billion years, HD 2014018A is estimated to be on the subgiant branch.[4] An alternate model places it on the main sequence at an age of 1,35 billion years.[1] The object spins at a moderate speed with a projected rotational velocity of 85 km/s.[15]

The companion is an F8 main sequence star[7] located ​2 1⁄2" away along a position angle of 151°.[22] It has an angular diameter of 0.186±0.035 arcseconds,[18] which yields a radius of 1.09 R☉ at its estimated distance.[17] It has 102% times the mass of the Sun[16] and an effective temperature of 6,235 K.[18] HD 204018B is estimated to be 3.46 billion years old and is slightly metal deficent.[19]

There is a magnitude 12 co-moving companion located 295.3" away from the system along a position angle of 75°.[22] It is a red dwarf with an estimated spectral class of K6 and any orbit would take over a million years.[23]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 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.
  2. ↑ 2.0 2.1 2.2 2.3 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. doi:10.1051/0004-6361:20011822. ISSN 0004-6361. Bibcode: 2002A&A...384..180F. 
  3. ↑ 3.0 3.1 3.2 3.3 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.
  4. ↑ 4.0 4.1 Corbally, C. J. (December 1984). "Close visual binaries. III - Parameters and evolutionary status". The Astronomical Journal 89: 1887. doi:10.1086/113700. ISSN 0004-6256. Bibcode: 1984AJ.....89.1887C. 
  5. ↑ 5.0 5.1 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. doi:10.1086/192182. ISSN 0067-0049. Bibcode: 1995ApJS...99..135A. 
  6. ↑ 6.0 6.1 Feinstein, A. (April 1967). "Multicolor UBVRI observations of metallic-line stars". Publications of the Astronomical Society of the Pacific 79: 184. doi:10.1086/128464. ISSN 0004-6280. Bibcode: 1967PASP...79..184F. 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 Corbally, C. J. (August 1984). "Close visual binaries. I - MK classifications". The Astrophysical Journal Supplement Series 55: 657. doi:10.1086/190973. ISSN 0067-0049. Bibcode: 1984ApJS...55..657C. 
  8. ↑ 8.0 8.1 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. doi:10.1134/S1063773706110065. ISSN 1063-7737. Bibcode: 2006AstL...32..759G. 
  9. ↑ Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331–346. doi:10.1134/S1063773712050015. ISSN 1063-7737. Bibcode: 2012AstL...38..331A. 
  10. ↑ 10.0 10.1 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. ISSN 0004-6361. Bibcode: 1999A&A...352..555A. 
  11. ↑ 11.0 11.1 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. doi:10.1051/0004-6361:20035930. ISSN 0004-6361. Bibcode: 2004A&A...426..297K. 
  12. ↑ 12.0 12.1 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. doi:10.3847/0004-6256/151/3/59. Bibcode: 2016AJ....151...59C. 
  13. ↑ Stassun, Keivan G. et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal 158 (4): 138. doi:10.3847/1538-3881/ab3467. Bibcode: 2019AJ....158..138S. 
  14. ↑ 14.0 14.1 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. doi:10.3847/1538-4365/ab04f5. Bibcode: 2019ApJS..241...12S. 
  15. ↑ 15.0 15.1 Huang, Su-Shu (September 1953). "A Statistical Study of the Rotation of the Stars.". The Astrophysical Journal 118: 285. doi:10.1086/145751. ISSN 0004-637X. Bibcode: 1953ApJ...118..285H. 
  16. ↑ 16.0 16.1 16.2 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. doi:10.1051/0004-6361/202142369. ISSN 0004-6361. Bibcode: 2022A&A...658A..91A. 
  17. ↑ 17.0 17.1 Lang, Kenneth R. (2006). Astrophysical formulae. Astronomy and astrophysics library. 1 (3 ed.). Birkhäuser. ISBN 3-540-29692-1. https://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41. . The radius (R*) is given by:
    [math]\displaystyle{ \begin{align} 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{align} }[/math]
  18. ↑ 18.0 18.1 18.2 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. doi:10.3847/1538-3881/aa957b. Bibcode: 2017AJ....154..259S. 
  19. ↑ 19.0 19.1 Gontcharov, G. A. (December 2012). "Dependence of kinematics on the age of stars in the solar neighborhood". Astronomy Letters 38 (12): 771–782. doi:10.1134/S1063773712120031. ISSN 1063-7737. Bibcode: 2012AstL...38..771G. 
  20. ↑ "HR 8202". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HR+8202. 
  21. ↑ 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. doi:10.1093/mnras/stx2219. ISSN 0035-8711. Bibcode: 2017MNRAS.472.3805G. 
  22. ↑ 22.0 22.1 Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (December 2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal 122 (6): 3466–3471. doi:10.1086/323920. ISSN 0004-6256. Bibcode: 2001AJ....122.3466M. 
  23. ↑ Tokovinin, Andrei (23 February 2018). "The Updated Multiple Star Catalog". The Astrophysical Journal Supplement Series 235 (1): 6. doi:10.3847/1538-4365/aaa1a5. Bibcode: 2018ApJS..235....6T. 
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