Astronomy:HD 193721

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Short description: Astrometric binary in the constellation Octans
HD 193721
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
Constellation Octans
Right ascension  20h 33m 17.6366s[1]
Declination −80° 57′ 53.5944″[1]
Apparent magnitude (V) 5.77±0.01[2]
Characteristics
Spectral type G6/8 II[3]
U−B color index +0.85[4]
B−V color index +1.14[4]
Astrometry
Radial velocity (Rv)8.6±0.7[5] km/s
Proper motion (μ) RA: +9.794[1] mas/yr
Dec.: −16.081[1] mas/yr
Parallax (π)4.2823 ± 0.165[1] mas
Distance760 ± 30 ly
(234 ± 9 pc)
Absolute magnitude (MV)−0.24[6]
Details
Mass3.49[7] M☉
Radius24.38[8] R☉
Luminosity300±5[9] L☉
Surface gravity (log g)2.14±0.02[1] cgs
Temperature4953±122[8] K
Metallicity [Fe/H]−0.15[10] dex
Rotational velocity (v sin i)2.7±1.1[11] km/s
Other designations
CPD−81°901, FK5 3994, GC 28453, HD 193721, HIP 101427, HR 7785, SAO 258861, WDS J20333-8058A[12]
Database references
SIMBADdata

HD 193721 (HR 7785) is an astrometric binary[13] in the southern circumpolar constellation Octans. It has an apparent magnitude of 5.77,[2] allowing it to be faintly seen with the naked eye. Parallax measurements place the system 760 light years[1] away from the Solar System and it is currently receding with a heliocentric radial velocity 8.6 km/s.[5]

HD 193721 has a stellar classification of G6/8 II[3] — intermediate between a G6 and 8 bright giant. At present it has 3.49 times the mass of the Sun,[7] but has expanded to 24.4 times its girth.[8] It shines with a luminosity of 300 solar luminosity[9] from its enlarged photosphere at an effective temperature of 4,953 K,[8] giving a yellow hue. HD 193721 is metal deficent with an iron abundance 71% that of the Sun[10] and spins leisurely with a projected rotational velocity of 2.7 km/s.[11]

The system has an companion designated CPD −81°900. The object has a spectral classification of F8[14] and is located 25.5″ along a position angle of 0° (as of 1998).[15] CPD −81°900 is a foreground object, having a higher parallax[16] and different proper motion.[15]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode: 2000A&A...355L..27H. 
  3. ↑ 3.0 3.1 Houk, N.; Cowley, A. P. (1975). University of Michigan Catalogue of two-dimensional spectral types for the HD stars. Volume I. Declinations -90_ to -53_ƒ0.. Bibcode: 1975mcts.book.....H. 
  4. ↑ 4.0 4.1 Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory 4: 99–110. Bibcode: 1966CoLPL...4...99J. 
  5. ↑ 5.0 5.1 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. 
  6. ↑ Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation" (in en). Astronomy Letters 38 (5): 331–346. doi:10.1134/S1063773712050015. ISSN 1063-7737. Bibcode: 2012AstL...38..331A. 
  7. ↑ 7.0 7.1 Kervella, Pierre; Arenou, Frédéric; Thévenin, Frédéric (2022). "Stellar and substellar companions from Gaia EDR3". Astronomy & Astrophysics 657: A7. doi:10.1051/0004-6361/202142146. ISSN 0004-6361. Bibcode: 2022A&A...657A...7K. 
  8. ↑ 8.0 8.1 8.2 8.3 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. ISSN 0004-6256. Bibcode: 2019AJ....158..138S. 
  9. ↑ 9.0 9.1 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  10. ↑ 10.0 10.1 Anders, F. et al. (August 2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy & Astrophysics 628: A94. doi:10.1051/0004-6361/201935765. ISSN 0004-6361. Bibcode: 2019A&A...628A..94A. 
  11. ↑ 11.0 11.1 De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (January 2014). "A catalog of rotational and radial velocities for evolved stars: V. Southern stars⋆⋆⋆". Astronomy & Astrophysics 561: A126. doi:10.1051/0004-6361/201220762. ISSN 0004-6361. Bibcode: 2014A&A...561A.126D. 
  12. ↑ "HR 7785". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HR+7785. 
  13. ↑ Frankowski, A.; Jancart, S.; Jorissen, A. (19 December 2006). "Proper-motion binaries in the Hipparcos catalogue". Astronomy & Astrophysics 464 (1): 377–392. doi:10.1051/0004-6361:20065526. ISSN 0004-6361. Bibcode: 2007A&A...464..377F. 
  14. ↑ Stoy, R. H. (1968). "Cape photographic catalague for 1950.0, zones −80° to −90°". Annals of the Cape Observatory 22. Bibcode: 1968AnCap..22.....S. 
  15. ↑ 15.0 15.1 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. 
  16. ↑ Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
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