Wikipedia

HD 178845

HD 178845, also known as HR 7271 or rarely 49 G. Telescopii, is a binary star located in the southern constellation Telescopium. Gaia DR3 parallax measurements place the system 379 light years away[3][1] and both components are approaching the Solar System with heliocentric radial velocities of −26 km/s and −24 km/s respectively.[6][8] At its current distance, HD 178845A's brightness is diminished by 0.22 magnitudes due to interstellar dust.[12]

HD 178845
Location of HD 178845 (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Telescopium
A
Right ascension 19h 12m 46.13847s[1]
Declination −50° 29′ 11.1095″[1]
Apparent magnitude (V) 6.13[2]
B
Right ascension 19h 12m 45.51968s[3]
Declination −50° 29′ 08.7448″[3]
Apparent magnitude (V) 10.90±0.02[4]
Characteristics
A
Spectral type G8 III[5]
B−V color index +0.95[2]
Astrometry
A
Radial velocity (Rv)−26.4±0.4[6] km/s
Proper motion (μ) RA: +44.868 mas/yr[1]
Dec.: −42.034 mas/yr[1]
Parallax (π)8.6125 ± 0.0283 mas[1]
Distance379 ± 1 ly
(116.1 ± 0.4 pc)
Absolute magnitude (MV)+0.68[7]
B
Radial velocity (Rv)−24.2±5.3[8] km/s
Proper motion (μ) RA: +46.984 mas/yr[3]
Dec.: −41.403 mas/yr[3]
Parallax (π)8.6162 ± 0.024 mas[3]
Distance379 ± 1 ly
(116.1 ± 0.3 pc)
Details[9]
A
Mass2.35±0.08 M☉
Radius9.13±0.16 R☉
Luminosity47±0.9 L☉
Surface gravity (log g)2.95±0.10 cgs
Temperature5,001±36 K
Metallicity [Fe/H]+0.02±0.03 dex
Rotational velocity (v sin i)2.6±1.1[10] km/s
Age455+45
−46[1] Myr
Other designations
49 G. Telescopii[11], CD−50°12377, CPD−50°10995, HD 178845, HIP 94398, HR 7271, SAO 245976, CCDM J19128-5029AB, WDS J19128-5029A
Database references
SIMBADdata

The primary has an apparent magnitude of 6.13,[2] placing it near the naked eye viewing limit and the companion has an apparent magnitude of 10.9,[4] making it readily visible in medium-sized telescopes. The system was first observed by astronomer Willem Hendrik van den Bos in 1930.[13] As of 1991, HD 178845B is located 7.2" away along a position angle of 320°.[14]

The primary is an evolved red giant with a stellar classification of G8 III.[5] It has 2.35 times the mass of the Sun[9] but at the age of 455 million years,[1] it has expanded to 9.1 times its radius.[9] It radiates 47 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 5,001 K,[9] giving it a yellow hue. It has a solar metallicity ([Fe/H] = +0.02[9]) and spins modestly with a projected rotational velocity of 2.6 km/s.[10]

References

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  1. ^ a b c d e f g 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. ^ a b c 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.
  3. ^ a b c d e 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. ^ a b Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361.
  5. ^ a b Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars: Declinations −53° to −40°. Vol. 2. Bibcode:1978mcts.book.....H.
  6. ^ a b 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.
  7. ^ 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.
  8. ^ a b Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  9. ^ a b c d e Ottoni, G.; Udry, S.; Ségransan, D.; Buldgen, G.; Lovis, C.; Eggenberger, P.; Pezzotti, C.; Adibekyan, V.; Marmier, M.; Mayor, M.; Santos, N. C.; Sousa, S. G.; Lagarde, N.; Charbonnel, C. (January 2022). "CORALIE radial-velocity search for companions around evolved stars (CASCADES): I. Sample definition and first results: Three new planets orbiting giant stars". Astronomy & Astrophysics. 657: A87. arXiv:2201.01528. Bibcode:2022A&A...657A..87O. doi:10.1051/0004-6361/202040078. eISSN 1432-0746. ISSN 0004-6361.
  10. ^ a b 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. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. eISSN 1432-0746. ISSN 0004-6361. S2CID 54046583.
  11. ^ 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.
  12. ^ 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.
  13. ^ van den Bos, W. H. (May 1930). "New southern double stars, tenth list". Bulletin of the Astronomical Institutes of the Netherlands. 5: 179. Bibcode:1930BAN.....5..179V. ISSN 0365-8910.
  14. ^ 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. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. ISSN 0004-6256.
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